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Sample records for bunch length measurement

  1. CEBAF Upgrade Bunch Length Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Mahmoud [Old Dominion Univ., Norfolk, VA (United States)

    2016-05-01

    Many accelerators use short electron bunches and measuring the bunch length is important for efficient operations. CEBAF needs a suitable bunch length because bunches that are too long will result in beam interruption to the halls due to excessive energy spread and beam loss. In this work, bunch length is measured by invasive and non-invasive techniques at different beam energies. Two new measurement techniques have been commissioned; a harmonic cavity showed good results compared to expectations from simulation, and a real time interferometer is commissioned and first checkouts were performed. Three other techniques were used for measurements and comparison purposes without modifying the old procedures. Two of them can be used when the beam is not compressed longitudinally while the other one, the synchrotron light monitor, can be used with compressed or uncompressed beam.

  2. Bunch length measurements using synchrotron ligth monitor

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Mahmoud [Old Dominion University, Norfolk, VA; Tiefenback, Michael G. [Jefferson Lab, Newport News, VA

    2015-09-01

    The bunch length is measured at CEBAF using an invasive technique. The technique depends on applying an energy chirp for the electron bunch and imaging it through a dispersive region. The measurements are taken through Arc1 and Arc2 at CEBAF. The fundamental equations, procedure and the latest results are given.

  3. Electron bunch length measurement at the Vanderbilt FEL

    Energy Technology Data Exchange (ETDEWEB)

    Amirmadhi, F.; Brau, C.A.; Mendenhall, M. [Vanderbilt Free-Electron-Laser Center, Nashville, TN (United States)] [and others

    1995-12-31

    During the past few years, a number of experiments have been performed to demonstrate the possibility to extract the longitudinal charge distribution from spectroscopic measurements of the coherent far-infrared radiation emitted as transition radiation or synchrotron radiation. Coherent emission occurs in a spectral region where the wavelength is comparable to or longer than the bunch length, leading to an enhancement of the radiation intensity that is on the order of the number of particles per bunch, as compared to incoherent radiation. This technique is particularly useful in the region of mm and sub-mm bunch lengths, a range where streak-cameras cannot be used for beam diagnostics due to their limited time resolution. Here we report on experiments that go beyond the proof of principle of this technique by applying it to the study and optimization of FEL performance. We investigated the longitudinal bunch length of the Vanderbilt FEL by analyzing the spectrum of coherent transition radiation emitted by the electron bunches. By monitoring the bunch length while applying a bunch-compression technique, the amount of the compression could be easily observed. This enabled us to perform a systematic study of the FEL performance, especially gain and optical pulse width, as a function of the longitudinal electron distribution in the bunch. The results of this study will be presented and discussed.

  4. Coherent Transition Radiation to Measure the SLAC Electron Bunch Length

    CERN Document Server

    Muggli, Patric; Hogan, Mark; Ischebeck, Rasmus; Krejcik, Patrick; Schlarb, Holger; Siemann, Robert; Walz, Dieter

    2005-01-01

    Ultrashort electron bunches are now available at Stanford Linear Accelerator Center and are use mainly to produce short bursts of x-rays in a magnetic undulator and for plasma wakefield acceleration experiments. The shortest bunches have an rms longitudinal width of ˜10 microns, and a peak current of about 30 kA. Methods to measure such short bunch lengths include electro-optic modulation of a short laser pulse in a nonlinear crystal and coherent transition (CTR) autocorrelation. The transition radiation spectrum emitted by the bunches when traversing a 1 micron thin titanium foil is coherent for wavelengths longer that the bunch length and extends into the millimeter wavelength range. A CTR far-infrared autocorrelator was used to measure the bunch length as a function of the accelerator. The results obtained with this autocorrelator are the only measurements of the SLAC ultra-short bunches to date. Experimental results, as well as the limitations of the measurements and the future improvements to the autoco...

  5. Electron bunch length measurement with a wakefield radiation decelerator

    Directory of Open Access Journals (Sweden)

    Weiwei Li

    2014-03-01

    Full Text Available In this paper, we propose a novel method to measure the electron bunch length with a dielectric wakefield radiation (DWR decelerator which is composed of two dielectric-lined waveguides (DLWs and an electron spectrometer. When an electron beam passes through a DLW, the DWR is excited which leads to an energy loss of the electron beam. The energy loss is found to be largely dependent on the electron bunch length and can be easily measured by an electron spectrometer which is essential for a normal accelerator facility. Our study shows that this method has a high resolution and a great simplicity.

  6. Bunch Length and Impedance Measurements at SPEAR3

    Energy Technology Data Exchange (ETDEWEB)

    Corbett, W.J.; Cheng, W.X.; Fisher, A.S.; Huang, X.; /SLAC

    2011-11-02

    Streak camera measurements were made at SPEAR3 to characterize longitudinal coupling impedance. For the nominal optics, data was taken at three rf voltages and a single-bunch current range of 0-20mA. Both bunchcentroid phase shift and bunch lengthening were recorded to extract values for resistive and reactive impedance. An (R+L) and a Q=1 model were then back-substituted into the Haissinski equation and compared with raw profile data. In the short bunch (low-{alpha}) mode, distribution 'bursting' was observed.

  7. Infrared Spectroscope for Electron Bunch-length Measurement: Heat Sensor Parameters Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Domgmo-Momo, Gilles; /Towson U. /SLAC

    2012-09-05

    The Linac Coherent Light Source (LCLS) is used for many experiments. Taking advantage of the free electron laser (FEL) process, scientists of various fields perform experiments of all kind. Some for example study protein folding; other experiments are more interested in the way electrons interact with the molecules before they are destroyed. These experiments among many others have very little information about the electrons x-ray produced by the FEL, except that the FEL is using bunches less than 10 femtoseconds long. To be able to interpret the data collected from those experiments, more accurate information is needed about the electron's bunch-length. Existing bunch length measurement techniques are not suitable for the measurement of such small time scales. Hence the need to design a device that will provide more precise information about the electron bunch length. This paper investigates the use of a pyreoelectric heat sensor that has a sensitivity of about 1.34 micro amps per watt for the single cell detector. Such sensitivity, added to the fact that the detector is an array sensor, makes the detector studied the primary candidate to be integrated to an infrared spectrometer designed to better measure the LCLS electron bunch length.

  8. Single-shot electron bunch length measurements using a spatial electro-optical autocorrelation interferometer.

    Science.gov (United States)

    Sütterlin, Daniel; Erni, Daniel; Schlott, Volker; Sigg, Hans; Jäckel, Heinz; Murk, Axel

    2010-10-01

    A spatial, electro-optical autocorrelation (EOA) interferometer using the vertically polarized lobes of coherent transition radiation (CTR) has been developed as a single-shot electron bunch length monitor at an optical beam port downstream the 100 MeV preinjector LINAC of the Swiss Light Source. This EOA monitor combines the advantages of step-scan interferometers (high temporal resolution) [D. Mihalcea et al., Phys. Rev. ST Accel. Beams 9, 082801 (2006) and T. Takahashi and K. Takami, Infrared Phys. Technol. 51, 363 (2008)] and terahertz-gating technologies [U. Schmidhammer et al., Appl. Phys. B: Lasers Opt. 94, 95 (2009) and B. Steffen et al., Phys. Rev. ST Accel. Beams 12, 032802 (2009)] (fast response), providing the possibility to tune the accelerator with an online bunch length diagnostics. While a proof of principle of the spatial interferometer was achieved by step-scan measurements with far-infrared detectors, the single-shot capability of the monitor has been demonstrated by electro-optical correlation of the spatial CTR interference pattern with fairly long (500 ps) neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pulses in a ZnTe crystal. In single-shot operation, variations of the bunch length between 1.5 and 4 ps due to different phase settings of the LINAC bunching cavities have been measured with subpicosecond time resolution.

  9. Longitudinal bunch length measurement of RFQ beam using in-house developed detector system

    Science.gov (United States)

    Pandey, H. K.; Dechoudhury, S.; Bhattacharyya, T. K.; Chakrabarti, A.

    2017-09-01

    We report here the bunch width measurement of 98keV/u ion beam accelerated through a 3.4 m long 37.8 MHz Radio Frequency Quadruple (RFQ) linac using a minimally interceptive approach. The detector system for this measurement has been indigenously developed and is based on secondary electron emission from tungsten filament on being hit by ion beam, followed by a capacitive loaded helical resonator cavity. A Channeltron Electron Multiplier (CEM) detector is used for detection of electrons. The design, development and optimization of various parameters of bunch width detector system along with its deflector cavity applicable in the low frequency regime (few tens of MHz) have been discussed. The measured bunch profile of accelerated Nitrogen beam from RFQ is in close agreement with the estimated profile obtained via simulation.

  10. Bunch Length Measurements at the SLS Linac Using Electro Optical Sampling

    CERN Document Server

    Steffen, Bernd; Schmüser, Peter; Simrock, Stefan

    2004-01-01

    The temporal profile of the electron bunches in the SLS Linac was determined by means of electro-optical techniques. In a first experiment a mode locked Ti:Sa Laser with 15 fs pulse width (FWHM) was used for coincidence and sampling measurements between the laser pulse and the coherent transition radiation (CTR) generated by short electron bunches. A synchronization accuracy of 70 fs rms between the 3 GHz Linac RF and the 81 MHz repetition frequency of the laser was achieved, which is important for the optimum time resolution of the applied electro-optical sampling technique. In a second experiment a mode locked Nd:YAG laser with 400 ps long pulses will be used for electro-optical autocorrelation measurements between the CTR and the laser pulses. This alternative technique promises single shot capability and requires much relaxed synchronization stability between laser and electron beam.

  11. Application of a Low-Energy Electron Beam as a Tool for ultrashort bunch length measurement in circular machines

    CERN Document Server

    Nikiforov, D A; Malyutin, D; Matveenko, A; Rusinov, K; Starostenko, A A

    2017-01-01

    A new diagnostic device designed for non-destructive ultrashort bunch length measurement is described. The operating principle of the device and the measuring technique are described. The possible scheme of arrangement of the device elements are described. The results of simulations of EBP application for different beams under investigation are presented. The quality requirements of the low energy testing beam are considered and resolving detector ability is determined.

  12. LIGHT SOURCE: RF deflecting cavity for bunch length measurement in Tsinghua Thomson scattering X-ray source

    Science.gov (United States)

    Shi, Jia-Ru; Chen, Huai-Bi; Tang, Chuan-Xiang; Huang, Wen-Hui; Du, Ying-Chao; Zheng, Shu-Xin; Ren, Li

    2009-06-01

    An RF deflecting cavity used for bunch length measurement has been designed and fabricated at Tsinghua University for the Thomson Scattering X-Ray Source. The cavity is a 2856 MHz, π-mode, 3-cell standing-wave cavity, to diagnose the 3.5 MeV beam produced by photocathode electron gun. With a larger power source, the same cavity will again be used to measure the accelerated beam with energy of 50 MeV before colliding with the laser pulse. The RF design using MAFIA for both the cavity shape and the power coupler is reviewed, followed by presenting the fabrication procedure and bench measurement results of two cavities.

  13. Effects of correlations between particle longitudinal positions and transverse plane on bunch length measurement: a case study on GBS electron LINAC at ELI-NP

    Science.gov (United States)

    Sabato, L.; Arpaia, P.; Cianchi, A.; Liccardo, A.; Mostacci, A.; Palumbo, L.; Variola, A.

    2018-02-01

    In high-brightness LINear ACcelerators (LINACs), electron bunch length can be measured indirectly by a radio frequency deflector (RFD). In this paper, the accuracy loss arising from non-negligible correlations between particle longitudinal positions and the transverse plane (in particular the vertical one) at RFD entrance is analytically assessed. Theoretical predictions are compared with simulation results, obtained by means of ELEctron Generation ANd Tracking (ELEGANT) code, in the case study of the gamma beam system (GBS) at the extreme light infrastructure—nuclear physics (ELI-NP). In particular, the relative error affecting the bunch length measurement, for bunches characterized by both energy chirp and fixed correlation coefficients between longitudinal particle positions and the vertical plane, is reported. Moreover, the relative error versus the correlation coefficients is shown for fixed RFD phase 0 rad and π rad. The relationship between relative error and correlations factors can help the decision of using the bunch length measurement technique with one or two vertical spot size measurements in order to cancel the correlations contribution. In the case of the GBS electron LINAC, the misalignment of one of the quadrupoles before the RFD between  ‑2 mm and 2 mm leads to a relative error less than 5%. The misalignment of the first C-band accelerating section between  ‑2 mm and 2 mm could lead to a relative error up to 10%.

  14. Single-shot method for measuring femtosecond bunch length in linac-based free-electron lasers

    Directory of Open Access Journals (Sweden)

    Z. Huang

    2010-09-01

    Full Text Available There is growing interest in the generation and characterization of femtosecond and subfemtosecond pulses from linac-based free-electron lasers (FELs. In this report, following the method of Ricci and Smith [Phys. Rev. ST Accel. Beams 3, 032801 (2000PRABFM1098-440210.1103/PhysRevSTAB.3.032801], we investigate the measurement of the longitudinal bunch profile of an ultrashort electron bunch produced by these FELs. We show that this method can be applied in a straightforward manner at x-ray FEL facilities such as the Linac Coherent Light Source by slightly adjusting the second bunch compressor followed by running the bunch on an rf zero-crossing phase of the final linac. We find that the linac wakefield strongly perturbs the measurement, and through analysis show that it can be compensated in a simple way. We demonstrate the effectiveness of this method and wakefield compensation through numerical simulations, including effects of coherent synchrotron radiation and longitudinal space charge. When used in conjunction with a high-resolution electron spectrometer, this method potentially reveals the temporal profile of the electron beam down to the femtosecond and subfemotsecond scale.

  15. Harmonically resonant cavity as a bunch-length monitor

    Directory of Open Access Journals (Sweden)

    B. Roberts

    2016-05-01

    Full Text Available A compact, harmonically resonant cavity with fundamental resonant frequency 1497 MHz was used to evaluate the temporal characteristics of electron bunches produced by a 130 kV dc high voltage spin-polarized photoelectron source at the Continuous Electron Beam Accelerator Facility (CEBAF photoinjector, delivered at 249.5 and 499 MHz repetition rates and ranging in width from 45 to 150 picoseconds (FWHM. A cavity antenna attached directly to a sampling oscilloscope detected the electron bunches as they passed through the cavity bore with a sensitivity of ∼1  mV/μA. The oscilloscope waveforms are a superposition of the harmonic modes excited by the beam, with each cavity mode representing a term of the Fourier series of the electron bunch train. Relatively straightforward post-processing of the waveforms provided a near-real time representation of the electron bunches revealing bunch-length and the relative phasing of interleaved beams. The noninvasive measurements from the harmonically resonant cavity were compared to measurements obtained using an invasive RF-deflector-cavity technique and to predictions from particle tracking simulations.

  16. Microwave measurement of intra bunch charge distributions

    CERN Document Server

    Dehler, M

    2003-01-01

    A direct way of obtaining intra bunch charge distributions is to measure the amplitude roll off as well as the phase behavior of the spectrum of the single bunch self field. To that effect, a microwave pickup together with a microwave front end has been installed in the storage ring of the Swiss Light Source (SLS). As pickup, button type bpms are used, which have been designed for a broad band behavior in the excess of 30 GHz. Three bpms together with their individual front ends are used in order to sample the beam spectrum at frequencies of 6, 12 and 18 GHz, which compares to the standard spectrum of a 1 mA single bunch extending to approximately 12 GHz (13 ps rms bunch length). The signals are mixed to base band in loco using the multiplied RF frequency as a LO. By shifting the LO phase, simultaneously the amplitude roll off as well the complex phase of the beam spectrum can be obtained. Where using a resonator as a pickup would smear out the response over several bunches, allowing only the determination of...

  17. Generation and measurement of velocity bunched ultrashort bunch of pC charge

    Directory of Open Access Journals (Sweden)

    X. H. Lu

    2015-03-01

    Full Text Available In this paper, we discuss the velocity compression in a short rf linac of an electron bunch from a rf photoinjector operated in the blowout regime. Particle tracking simulations shows that with a beam charge of 2 pC an ultrashort bunch duration of 16 fs can be obtained at a tight longitudinal focus downstream of the linac. A simplified coherent transition radiation (CTR spectrum method is developed to enable the measurement of ultrashort (sub-50 fs bunches at low bunch energy (5 MeV and low bunch charges (<10  pC. In this method, the ratio of the radiation energy selected by two narrow bandwidth filters is used to estimate the bunch length. The contribution to the coherent form factor of the large transverse size of the bunch suppresses the radiation signal significantly and is included in the analysis. The experiment was performed at the UCLA Pegasus photoinjector laboratory. The measurement results show bunches of sub-40 fs with 2 pC of charge well consistent with the simulation using actual experimental conditions. These results open the way to the generation of ultrashort bunches with time-duration below 10 fs once some of the limitations of the setup (rf phase jitter, amplitude instability and low field in the gun limited by breakdown are corrected.

  18. Optical Design of a Broadband Infrared Spectrometer for Bunch Length Measurement at the Linac Coherent Light Source

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Kiel; /SLAC

    2012-09-07

    The electron pulses generated by the Linac Coherent Light Source at the SLAC National Accelerator Laboratory occur on the order of tens of femtoseconds and cannot be directly measured by conventional means. The length of the pulses can instead be reconstructed by measuring the spectrum of optical transition radiation emitted by the electrons as they move toward a conducting foil. Because the emitted radiation occurs in the mid-infrared from 0.6 to 30 microns a novel optical layout is required. Using a helium-neon laser with wavelength 633 nm, a series of gold-coated off-axis parabolic mirrors were positioned to direct a beam through a zinc selenide prism and to a focus at a CCD camera for imaging. Constructing this layout revealed a number of novel techniques for reducing the aberrations introduced into the system by the off-axis parabolic mirrors. The beam had a recorded radius of less than a millimeter at its final focus on the CCD imager. This preliminary setup serves as a model for the spectrometer that will ultimately measure the LCLS electron pulse duration.

  19. Nondestructive diagnostic for electron bunch length in accelerators using the wakefield radiation spectrum

    Directory of Open Access Journals (Sweden)

    S. V. Shchelkunov

    2005-06-01

    Full Text Available We report the development of a nondestructive technique to measure bunch rms length in the psec range and below, and eventually in the fsec range, by measuring the high-frequency spectrum of wakefield radiation which is caused by the passage of a relativistic electron bunch through a channel surrounded by a dielectric. We demonstrate numerically that the generated spectrum is determined by the rms bunch length, while the specific axial and longitudinal charge distribution is not important. Measurement of the millimeter-wave spectrum will determine the rms bunch length in the psec range. This has been done using a series of calibrated mesh filters and the charge bunches produced by the 50 MeV rf linac system at ATF (Accelerator Test Facility, Brookhaven. We have developed the analysis of the factors crucial for achieving good accuracy in this measurement, and find the experimental data are fully understood by the theory. We point out that this technique also may be used for measuring fsec bunch lengths, using a prepared planar wakefield microstructure.

  20. Measuring the longitudinal bunch profile at CTF3

    CERN Document Server

    Dabrowski, A E; Bettoni, S; Braun†, H H; Corsini, R; Döbert, S; Egger, D; Lefevre, T; Rabiller, A; Shaker, H; Soby, L; Skowronski, P K; Tecker, F; Velasco, M

    2010-01-01

    The CLIC Test Facility 3 (CTF3) is being built and commissioned by an international collaboration in order to test the feasibility of the proposed Compact Linear Collider (CLIC) two-beam acceleration scheme. The monitoring and control of the bunch length throughout the CTF3 complex is important since this affects the efficiency and the stability of the final RF power production process. Bunch length diagnostics therefore form an essential component of the beam instrumentation at CTF3. This paper presents longitudinal profile measurements based on Streak camera and non-destructive RF power and microwave spectrometry techniques.

  1. Measuring the Bunch Frequency Multiplication at CTF3

    CERN Document Server

    Bettoni, S; Corsini, R; Dabrowski, A; Doebert, S; Egger, D; Ferrari, A; Lefevre, T; Rabiller, A; Skowronski, PK; Soby, L; Tecker, F; Welsch, CP

    2010-01-01

    The CLIC Test Facility 3 (CTF3) is being built and commissioned by an international collaboration to test the feasibility of the proposed Compact Linear Collider (CLIC) drive beam generation scheme. Central to this scheme is the use of RF deflectors to inject bunches into a delay loop and a combiner ring, in order to transform the initial bunch frequency of 1.5 GHz from the LINAC to a final bunch frequency of 12 GHz. The optimization procedure relies on several steps. The active length of each ring is carefully adjusted to within less than millimetre accuracy using a wiggler magnet. The transverse optics of the machine must be set up in a way to ensure beam isochronicity. Diagnostics based on optical Streak camera and RF power measurements have been designed to measure the longitudinal behaviour of the beam during the combination. This paper presents their performance and recent measurements

  2. Luminosity geometric reduction factor from colliding bunches with different lengths

    Energy Technology Data Exchange (ETDEWEB)

    Verdu-Andres, S. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2017-09-29

    In the interaction point of the future electron-Ion collider eRHIC, the electron beam bunches are at least one order of magnitude shorter than the proton beam bunches. With the introduction of a crossing angle, the actual number of collisions resulting from the bunch collision gets reduced. Here we derive the expression for the luminosity geometric reduction factor when the bunches of the two incoming beams are not equal.

  3. Studies of bunch length and charge for the planned THz source, FLUTE

    Energy Technology Data Exchange (ETDEWEB)

    Naknaimueang, Somprasong [Karlsruhe Institute of Technology, Karlsruhe (Germany); Collaboration: FLUTE-Collaboration

    2013-07-01

    FLUTE is a THz source consisting of a 7 MeV photon gun, a 40 to 50 MeV linac, and a bunch compressor. The gun can produce up to 3 nC electron bunches which are several picoseconds long. At high charges, the transverse and longitudinal beam sizes are limited by space charge effects. In addition, coherent synchrotron radiation effects in the compressor limit the minimum obtainable bunch length in this case. The relationship between bunch charge and obtainable bunch length for a FLUTE-type accelerator is discussed.

  4. Electron beam bunch length characterizations using incoherent and coherent radiation on the APS SASE FEL project.

    Energy Technology Data Exchange (ETDEWEB)

    Berg, W. J.; Happek, U.; Lewellen, J. W.; Lumpkin, A. H.; Sereno, N. S.; Yang, B. X.

    1999-08-28

    The Advanced Photon Source (APS) injector linac has been reconfigured with a low-emittance rf thermionic gun and a photocathode (PC) rf gun to support self-amplified spontaneous emission (SASE) free-electron laser (FEL) experiments. One of the most critical parameters for optimizing SASE performance (gain length) is the electron beam peak current, which requires a charge measurement and a bunch length measurement capability. We report here initial measurements of the latter using both incoherent optical transition radiation (OTR) and coherent transition radiation (CTR), A visible light Hamarnatsu C5680 synchroscan streak camera was used to measure the thermionic rf gun beam's bunch length ({sigma} {approximately}2 to 3ps) via OTR generated by the beam at 220 MeV and 200 mA macropulse average current. In addition, a CTR monitor (Michelson Interferometer) based on a Golay cell as the far infrared (FIR) detector has been installed at the 40-MeV station in the beamline. Initial observation s of CTR signal strength variation with gun a-magnet current and interferograms have been obtained. Progress in characterizing the beam at these locations and a comparison to other bunch length determinations will be presented.

  5. Pulse length of ultracold electron bunches extracted from a laser cooled gas

    Science.gov (United States)

    Franssen, J. G. H.; Frankort, T. L. I.; Vredenbregt, E. J. D.; Luiten, O. J.

    2017-01-01

    We present measurements of the pulse length of ultracold electron bunches generated by near-threshold two-photon photoionization of a laser-cooled gas. The pulse length has been measured using a resonant 3 GHz deflecting cavity in TM110 mode. We have measured the pulse length in three ionization regimes. The first is direct two-photon photoionization using only a 480 nm femtosecond laser pulse, which results in short (∼15 ps) but hot (∼104 K) electron bunches. The second regime is just-above-threshold femtosecond photoionization employing the combination of a continuous-wave 780 nm excitation laser and a tunable 480 nm femtosecond ionization laser which results in both ultracold (∼10 K) and ultrafast (∼25 ps) electron bunches. These pulses typically contain ∼103 electrons and have a root-mean-square normalized transverse beam emittance of 1.5 ± 0.1 nm rad. The measured pulse lengths are limited by the energy spread associated with the longitudinal size of the ionization volume, as expected. The third regime is just-below-threshold ionization which produces Rydberg states which slowly ionize on microsecond time scales. PMID:28396879

  6. Single bunch longitudinal measurements at the Cornell Electron-Positron Storage Ring

    Directory of Open Access Journals (Sweden)

    R. Holtzapple

    2000-03-01

    Full Text Available Measurements of the beam's bunch length in the Cornell Electron-Positron Storage Ring (CESR have been made using a streak camera. The streak camera uses visible synchrotron radiation produced by the beam to measure its longitudinal distribution. A description of CESR, the experimental setup, the streak camera used, and systematic errors and analysis techniques of the streak camera are described in this paper. The dependence of the bunch distribution on the current and accelerating rf voltage for a single bunch CESR was measured and compared with a theoretical model of CESR. The CESR vacuum chamber impedance is determined from the measured bunch distributions and is presented in this paper.

  7. Measuring the electron bunch timing with femtosecond resolution at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Bock, Marie Kristin

    2013-03-15

    Bunch arrival time monitors (BAMs) are an integral part of the laser-based synchronisation system which is being developed at the Free Electron Laser in Hamburg (FLASH).The operation principle comprises the measurement of the electron bunch arrival time relative to the optical timing reference, which is provided by actively length-stabilised fibre-links of the synchronisation system. The monitors are foreseen to be used as a standard diagnostic tool, not only for FLASH but also for the future European X-Ray Free-Electron Laser (European XFEL). The present bunch arrival time monitors have evolved from proof-of-principle experiments to beneficial diagnostic devices, which are almost permanently available during standard machine operation. This achievement has been a major objective of this thesis. The developments went in parallel to improvements in the reliable and low-maintenance operation of the optical synchronisation system. The key topics of this thesis comprised the characterisation and optimisation of the opto-mechanical front-ends of both, the fibre-links and the BAMs. The extent of applications involving the bunch arrival time information has been enlarged, providing automated measurements for properties of the RF acceleration modules, for instance, the RF on-crest phase determination and the measurement of energy fluctuations. Furthermore, two of the currently installed BAMs are implemented in an active phase and gradient stabilisation of specific modules in order to minimise the arrival time jitter of the electron bunches at the location of the FEL undulators, which is crucial for a high timing resolution of pump-probe experiments.

  8. Optical measurement of the longitudinal ion distribution of bunched ion beams in the ESR

    Energy Technology Data Exchange (ETDEWEB)

    Wen, W.Q. [Institute of Modern Physics, Chinese Academy of Sciences, 730000 Lanzhou (China); GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); University of Chinese Academy of Sciences, 100049 Beijing (China); Lochmann, M. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Institut für Kernchemie, Universität Mainz, 55128 Mainz (Germany); Ma, X., E-mail: x.ma@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, 730000 Lanzhou (China); Bussmann, M. [Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden (Germany); Winters, D.F.A. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Nörtershäuser, W. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Institut für Kernchemie, Universität Mainz, 55128 Mainz (Germany); Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany); Botermann, B. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Institut für Kernchemie, Universität Mainz, 55128 Mainz (Germany); Geppert, C.; Frömmgen, N.; Hammen, M. [Institut für Kernchemie, Universität Mainz, 55128 Mainz (Germany); Hannen, V.; Jöhren, R. [Institut für Kernphysik, Universität Münster, 48149 Münster (Germany); and others

    2013-05-21

    An optical technique to study the longitudinal distribution of ions in a bunched ion beam circulating in a storage ring is presented. It is based on the arrival-time analysis of photons emitted after collisional excitation of residual gas molecules. The beam-induced fluorescence was investigated in the ultraviolet regime with a channeltron and in the visible region using a photomultiplier tube. Both were applied to investigate the longitudinal shape of bunched and electron-cooled {sup 209}Bi{sup 80+} ion beams at about 400 MeV/u in the experimental storage ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Bunch lengths were determined with an uncertainty of about 0.5 m using the UV-sensitive channeltron and with slightly lower accuracy from the photomultiplier data due to the slower transitions in the red region of the spectrum. The Gaussian shape of the longitudinal distribution of ions inside the bunch was confirmed. With the information of the transverse beam size that can be measured simultaneously by a newly installed ionization profile monitor (IPM) at the ESR, an accurate determination of the ion density in the bunched beam will be allowed. -- Highlights: ► Optical methods to measure the bunch shape of ion beam at storage ring. ► High resolution of bunch length was obtained from the UV-sensitive channeltron. ► The Gaussian shape of longitudinal distribution of the ions in the bunch was confirmed.

  9. Measuring the bunch frequency multiplication at the 3rd CLIC Test Facility

    CERN Document Server

    Dabrowski, AE; Bravin, E; Corsini, R; Dobert, S; Lefevre, T; Rabiller, A; Soby, L; Skowronski, P K; Tecker, F; Egger, D; Ferrari, A; Welsch, C P

    2012-01-01

    The CLIC Test Facility 3 (CTF3) is being built and commissioned by an international collaboration to test the feasibility of the proposed Compact Linear Collider (CLIC) drive beam generation scheme. Central to this scheme is the use of RF deflectors to inject bunches into a delay loop and a combiner ring, in order to transform the initial bunch frequency of 1.5 GHz from the linac to a final bunch frequency of 12 GHz. To do so, the machine's transverse optics must be tuned to ensure beam isochronicity and each ring's length can finally be adjusted with wiggler magnets to a sub millimeter path length accuracy. Diagnostics based on optical streak camera and RF power measurements, in particular frequency bands, have been designed to measure the longitudinal behaviour of the beam during the combination. This paper presents the diagnostics and recent commissioning measurements.

  10. Determination of Longitudinal Electron Bunch Lengths on Picosecond Time Scales

    CERN Document Server

    Martínez, C; Calviño, F

    1999-01-01

    At CERN (European Laboratory for Particle Physics) the CLIC (Compact Linear Collider) study is pursuing the design of an electron-positron high-energy linear collider using an innovative concept for the RF (Radio Frequency) power production, the socalled two-beam acceleration scheme. In order to keep the length of the collider in a reasonable range while being able of accelerating electrons and positrons up to 5 TeV, the normal-conducting accelerating structures should operate at very high frequency (in this case 30 GHz). The RF power necessary to feed the accelerating cavities is provided by a second electron beam, the drive beam, running parallel to the main beam. The CLIC Test Facility (CTF) was build with the main aim of studying and demonstrating the feasibility of the two beam acceleration scheme and technology. It is composed of two beams, the drive beam that will generate the 30 GHz RF power and the main beam which will be accelerated by this power. In order to have a good efficiency for the power gen...

  11. Electron Cloud Cyclotron Resonances in the Presence of a Short-bunch-length Relativistic Beam

    Energy Technology Data Exchange (ETDEWEB)

    Celata, C.M.; Furman, Miguel A.; Vay, J.-L.; Yu, Jennifer W.

    2008-09-02

    Computer simulations using the 2D code"POSINST" were used to study the formation of the electron cloud in the wiggler section of the positron damping ring of the International Linear Collider. In order to simulate an x-y slice of the wiggler (i.e., a slice perpendicular to the beam velocity), each simulation assumed a constant vertical magnetic field. At values of the magnetic field where the cyclotron frequency was an integral multiple of the bunch frequency, and where the field strength was less than approximately 0.6 T, equilibrium average electron densities were up to three times the density found at other neighboring field values. Effects of this resonance between the bunch and cyclotron frequency are expected to be non-negligible when the beam bunch length is much less than the product of the electron cyclotron period and the beam velocity, for a beam moving at v~;;c. Details of the dynamics of the resonance are described.

  12. Multiple bunch longitudinal dynamics measurements at the Cornell Electron-Positron Storage Ring

    Directory of Open Access Journals (Sweden)

    R. Holtzapple

    2001-01-01

    Full Text Available The Cornell Electron-Positron Storage Ring (CESR has a longitudinal dipole-coupled-bunch instability that limits the total amount of current that can be stored in the ring without feedback. As a result, it is one of the major limitations for higher stored current and luminosity. This paper reports the measurements of multiple bunch longitudinal dynamics done on CESR with a streak camera. The camera was used to measure the dependence of the bunch distribution on current and accelerating rf voltage, for multiple bunches stored in CESR, as well as the effects of the longitudinal instability on the bunch distribution. Measurements of the beam's longitudinal bunch distribution with multiple bunches present in the ring help give an understanding of the instability, how it affects the bunch distribution, and possibly give insight into a cure of the instability.

  13. Real-Time, Single-Shot Temporal Measurements of Short Electron Bunches, Terahertz CSR and FEL Radiation

    CERN Document Server

    Berden, G; Van der Meer, A F G

    2005-01-01

    Electro-optic detection of the Coulomb field of electron bunches is a promising technique for single-shot measurements of the bunch length and shape in the sub-picosecond time domain. This technique has been applied to the measurement of 50 MeV electron bunches in the FELIX free electron laser, showing the longitudinal profile of single bunches of around 650 fs FWHM [Phys. Rev. Lett. 93, 114802 (2004)]. The method is non-destructive and real-time, and therefore ideal for online monitoring of the longitudinal shape of single electron bunches. At FELIX we have used it for real-time optimization of sub-picosecond electron bunches. Electro-optic detection has also been used to measure the electric field profiles of far-infrared (or terahertz) optical pulses generated by the relativistic electrons. We have characterised the far-infrared output of the free electron laser, and more recently, we have measured the temporal profile of terahertz optical pulses generated at one of the bending magnets.

  14. Measuring the electron beam energy in a magnetic bunch compressor

    Energy Technology Data Exchange (ETDEWEB)

    Hacker, Kirsten

    2010-09-15

    Within this thesis, work was carried out in and around the first bunch compressor chicane of the FLASH (Free-electron LASer in Hamburg) linear accelerator in which two distinct systems were developed for the measurement of an electron beams' position with sub-5 {mu}m precision over a 10 cm range. One of these two systems utilized RF techniques to measure the difference between the arrival-times of two broadband electrical pulses generated by the passage of the electron beam adjacent to a pickup antenna. The other system measured the arrival-times of the pulses from the pickup with an optical technique dependent on the delivery of laser pulses which are synchronized to the RF reference of the machine. The relative advantages and disadvantages of these two techniques are explored and compared to other available approaches to measure the same beam property, including a time-of-flight measurement with two beam arrival-time monitors and a synchrotron light monitor with two photomultiplier tubes. The electron beam position measurement is required as part of a measurement of the electron beam energy and could be used in an intra-bunch-train beam-based feedback system that would stabilize the amplitude of the accelerating field. By stabilizing the accelerating field amplitude, the arrival-time of the electron beam can be made more stable. By stabilizing the electron beam arrival-time relative to a stable reference, diagnostic, seeding, and beam-manipulation lasers can be synchronized to the beam. (orig.)

  15. Development of a coherent transition radiation-based bunch length monitor with application to the APS RF thermionic gun beam optimization

    CERN Document Server

    Lumpkin, Alex H; Berg, W J; Borland, M; Happek, U; Lewellen, J W; Sereno, N S

    2001-01-01

    We report further development of an EPICS-compatible bunch length monitor based on the autocorrelation of coherent transition radiation (CTR). In this case the monitor was used to optimize the beam from the S-band thermionic RF gun on the Advanced Photon Source (APS) linac. Bunch lengths of 400-500 fs (FWHM) were measured in the core of the beam, which corresponded to about 100-A peak current in each micropulse. The dependence of the CTR signal on the square of the beam charge for the beam core was demonstrated. We also report the first use of the beam accelerated to 217 MeV for successful visible wavelength SASE FEL experiments.

  16. Wakefield measurement using principal component analysis on bunch-by-bunch information during transient state of injection in a storage ring

    Directory of Open Access Journals (Sweden)

    Zhichu Chen

    2014-11-01

    Full Text Available Wakefields and beam instabilities are important issues for a storage ring and are described by various theoretical formalisms. Direct measurements of the beam motion related to different dynamical mechanisms are a useful input to accelerator optimization. This paper reports on an experimental method based on a simplified wakefield model, where bunch-by-bunch position information were monitored during the transient injection process at the Shanghai Synchrotron Radiation Facility. Processing the bunch-by-bunch data by means of the principal component analysis allowed for immediate operational improvements—such as in situ compensation of the kicker leakage, and energy matching between the booster and the storage ring.

  17. Long bunch trains measured using a prototype cavity beam position monitor for the Compact Linear Collider

    Directory of Open Access Journals (Sweden)

    F. J. Cullinan

    2015-11-01

    Full Text Available The Compact Linear Collider (CLIC requires beam position monitors (BPMs with 50 nm spatial resolution for alignment of the beam line elements in the main linac and beam delivery system. Furthermore, the BPMs must be able to make multiple independent measurements within a single 156 ns long bunch train. A prototype cavity BPM for CLIC has been manufactured and tested on the probe beam line at the 3rd CLIC Test Facility (CTF3 at CERN. The transverse beam position is determined from the electromagnetic resonant modes excited by the beam in the two cavities of the pickup, the position cavity and the reference cavity. The mode that is measured in each cavity resonates at 15 GHz and has a loaded quality factor that is below 200. Analytical expressions for the amplitude, phase and total energy of signals from long trains of bunches have been derived and the main conclusions are discussed. The results of the beam tests are presented. The variable gain of the receiver electronics has been characterized using beam excited signals and the form of the signals for different beam pulse lengths with the 2/3  ns bunch spacing has been observed. The sensitivity of the reference cavity signal to charge and the horizontal position signal to beam offset have been measured and are compared with theoretical predictions based on laboratory measurements of the BPM pickup and the form of the resonant cavity modes as determined by numerical simulation. Finally, the BPM was calibrated so that the beam position jitter at the BPM location could be measured. It is expected that the beam jitter scales linearly with the beam size and so the results are compared to predicted values for the latter.

  18. Non-destructive measurement and monitoring of separation of charged particle micro-bunches

    Science.gov (United States)

    Zhang, H.; Konoplev, I. V.; Lancaster, A. J.; Harrison, H.; Doucas, G.; Aryshev, A.; Shevelev, M.; Terunuma, N.; Urakawa, J.

    2017-07-01

    Micro-bunched particle beams are used for a wide range of research including wakefield-based particle acceleration and tunable sources of radiation. In all applications, accurate and non-destructive monitoring of the bunch-to-bunch separation is required. With the development of femtosecond lasers, the generation of micro-bunched beams directly from a photocathode becomes routine; however, non-destructive monitoring of the separation is still a challenge. We present the results of proof-of-principle experiments conducted at the Laser Undulator Compact X-ray accelerator measuring the distance between micro-bunches via the amplitude modulation analysis of a monochromatic radiation signal. Good agreement with theoretical predictions is shown; limitations and further improvements are discussed.

  19. Modelling and measurements of bunch profiles at the LHC

    Energy Technology Data Exchange (ETDEWEB)

    Papadopoulou, S. [Crete U.; Antoniou, F. [Liverpool U.; Argyropoulos, T. [CERN; Fitterer, M. [Fermilab; Hostettler, M. [CERN; Papaphilippou, Y. [CERN

    2017-07-20

    The bunch profiles in the LHC are often observed to be non-Gaussian, both at Flat Bottom (FB) and Flat Top (FT) energies. Especially at FT, an evolution of the tail population in time is observed. In this respect, the Monte-Carlo Software for IBS and Radiation effects (SIRE) is used to track different types of beam distributions. The impact of the distribution shape on the evolution of bunch characteristics is studied. The results are compared with observations from the LHC Run 2 data.

  20. Measurement report on the LHC injection kicker ripple denition and maximum pulse length (MD 1268)

    CERN Document Server

    Bartmann, Wolfgang; Kotzian, Gerd; Stoel, Linda; Velotti, Francesco Maria; Vlachodimitropoulos, Vasileios; Wiesner, Christoph; CERN. Geneva. ATS Department

    2016-01-01

    The present LHC lling scheme uses a batch spacing which corresponds to the design report specication of the injection kicker rise time. A reduction of the batch spacing can be directly used to increase luminosity without detrimental eect on beam stability. Therefore, measurements were performed to understand if a tighter batch spacing would lead to increased injection oscillations of a the rst and last bunches of a bunch train and eventually also a growth of the transverse emittance. The results of theses measurement were used to dene the minimum possible batch spacing for an acceptable emittance growth. Another measurement was performed to test if a batch consisting of 320 bunches can be injected instead of the nominal 288 bunch trains. This bunch train is dierently produced in the LHC injectors and features an optimum between beam stability and luminosity gain. The pulse length of the injection kicker was measured to ensure the full batch can be injected at once.

  1. Reflective optical system for time-resolved electron bunch measurements at PITZ

    Energy Technology Data Exchange (ETDEWEB)

    Rosbach, K.; Baehr, J. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Roensch-Schulenburg, J. [Hamburg Univ. (Germany). Inst. fuer Experimentalphysik

    2011-01-15

    The Photo-Injector Test facility at DESY, Zeuthen site (PITZ), produces pulsed electron beams with low transverse emittance and is equipped with diagnostic devices for measuring various electron bunch properties, including the longitudinal and transverse electron phase space distributions. The longitudinal bunch structure is recorded using a streak camera located outside the accelerator tunnel, connected to the diagnostics in the beam-line stations by an optical system of about 30 m length. This system mainly consists of telescopes of achromatic lenses, which transport the light pulses and image them onto the entrance slit of the streak camera. Due to dispersion in the lenses, the temporal resolution degrades during transport. This article presents general considerations for time-resolving optical systems as well as simulations and measurements of specific candidate systems. It then describes the development of an imaging system based on mirror telescopes which will improve the temporal resolution, with an emphasis on off-axis parabolic mirror systems working at unit magnification. A hybrid system of lenses and mirrors will serve as a proof of principle. (orig.)

  2. Improvement in the accuracy of flux measurement of radio sources by exploiting an arithmetic pattern in photon bunching noise

    Science.gov (United States)

    Lieu, Richard

    2018-01-01

    A hierarchy of statistics of increasing sophistication and accuracy is proposed, to exploit an interesting and fundamental arithmetic structure in the photon bunching noise of incoherent light of large photon occupation number, with the purpose of suppressing the noise and rendering a more reliable and unbiased measurement of the light intensity. The method does not require any new hardware, rather it operates at the software level, with the help of high precision computers, to reprocess the intensity time series of the incident light to create a new series with smaller bunching noise coherence length. The ultimate accuracy improvement of this method of flux measurement is limited by the timing resolution of the detector and the photon occupation number of the beam (the higher the photon number the better the performance). The principal application is accuracy improvement in the bolometric flux measurement of a radio source.

  3. A robust fibre laser system for electro-optic electron bunch profile measurements at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Wissmann, Laurens-Georg

    2012-08-15

    For the electro-optic measurement of electron bunch profiles at FLASH a robust ytterbium doped fibre laser (YDFL) system has been developed consisting of a laser oscillator and a two-staged amplifier. The oscillator is designed to meet the specifications of high reliability and low noise operation. The amplifier makes use of tailored nonlinearity to enhance the spectral bandwidth of the output laser pulses. Active repetition rate control enables sub-picosecond synchronisation of the laser to the accelerator reference RF. Using a two-stage gating scheme the output pulse train repetition rate is adopted to the accelerator repetition rate. An experimental site used for electro-optic electron bunch diagnostics has been redesigned to support single-shot bunch profile measurements based on spectral decoding. An existing bunch profile monitor with a similar laser system was upgraded and electro-optic bunch profile measurements were conducted, allowing for a comparison with measurements done with other longitudinal electron bunch diagnostics and with former measurements.

  4. Bunch-by-bunch measurement of transverse coherent beam-beam modes in the Fermilab Tevatron collider

    Directory of Open Access Journals (Sweden)

    Giulio Stancari

    2012-04-01

    Full Text Available A system for bunch-by-bunch detection of transverse proton and antiproton coherent oscillations in the Tevatron is described. It is based on the signal from a single beam-position monitor located in a region of the ring with large amplitude functions. The signal is digitized over a large number of turns and Fourier analyzed off-line with a dedicated algorithm. To enhance the signal, band-limited noise is applied to the beam for about 1 s. This excitation does not adversely affect the circulating beams even at high luminosities. The device has a response time of a few seconds, a frequency resolution of 1.6×10^{-5} in fractional tune, and it is sensitive to oscillation amplitudes of 60 nm. It complements Schottky detectors as a diagnostic tool for tunes, tune spreads, and beam-beam effects. Measurements of coherent mode spectra are presented to show the effects of betatron tunes, beam-beam parameter, and collision pattern, and to provide an experimental basis for beam-beam numerical codes. Comparisons with a simplified model of beam-beam oscillations are also described.

  5. Bunch Current Measurement Using a High-Speed Photodetector at HLS II

    Science.gov (United States)

    Zhou, Tianyu; Yang, Yongliang; Sun, Baogen; Lu, Ping; Wu, Fangfang; Wang, Jigang; Zhou, Zeran; Luo, Qing; Wang, Qian; Li, Hao

    2017-07-01

    This paper presents a novel bunch current measurement system based on an ultrafast photodetector and a high-speed digitizer at Hefei light source II (HLS II). We use a metal-semiconductor-metal photodetector to measure the emitted optical synchrotron radiation intensity directly, representing the bunch current intensity. To achieve bunch-by-bunch resolution, the sampling rate of the system is nearly 225 GS/s, which is achieved via a dedicated equivalent sampling algorithm. The detailed description of the experimental setup and the equivalent sampling algorithm are presented. According to preliminary tests of the daily operation mode and single-bunch mode, the measured root-mean-square of the beam current is 1%, which shows that the new system satisfies the requirements for high-precision bunch current measurements. In addition, experimental results of the “HLS” Morse-code fill pattern mode demonstrate that this system could also be a convenient and robust tool for beam top-up modes in the future.

  6. Ion bunch length effects on the beam-beam interaction and its compensation in a high-luminosity ring-ring electron-ion collider

    Energy Technology Data Exchange (ETDEWEB)

    Montag C.; Oeftiger, A.; Fischer, W.

    2012-05-20

    One of the luminosity limits in a ring-ring electron-ion collider is the beam-beam effect on the electrons. In the limit of short ion bunches, simulation studies have shown that this limit can be significantly increased by head-on beam-beam compensation with an electron lens. However, with an ion bunch length comparable to the beta-function at the IP in conjunction with a large beam-beam parameter, the electrons perform a sizeable fraction of a betatron oscillation period inside the long ion bunches. We present recent simulation results on the compensation of this beam-beam interaction with multiple electron lenses.

  7. Correlation between morphological characters and estimated bunch ...

    African Journals Online (AJOL)

    The methodology of multiple linear regression (MLR) was used to estimate bunch weight. The most significant variables that were measured included number of leaves at harvest, number of fruits per bunch, FW, FL, rachis weight (RW) and stalk length (SL), generating the following prediction equation: BW= -5.249 + ...

  8. Measurements of Transverse Coupled-Bunch Instabilities in PEP-II

    Energy Technology Data Exchange (ETDEWEB)

    Teytelman, D.

    2005-04-11

    At the design currents the PEP-II High and Low Energy Rings operate above the coupled-bunch instability thresholds in horizontal and vertical planes. Both machines have used analog bunch-by-bunch feedback systems to stabilize the beams since commissioning. Here we present a measurement technique that uses the capabilities of the PEP-II programmable digital longitudinal feedback system to provide transient diagnostics in X or Y directions. This technique allows one to measure instability growth or damping rates as well as oscillation frequencies in both open-loop and closed-loop conditions. Based on these measurements the configuration of the relevant transverse feedback channel can be optimized. The technique will be illustrated with instability measurements and feedback optimization examples. Comparisons of the measured modal patterns and growth rates to the theoretical predictions will be presented.

  9. Stability of longitudinal bunch length feedback for heavy-ion synchrotrons

    Directory of Open Access Journals (Sweden)

    D. Lens

    2013-03-01

    Full Text Available In heavy-ion synchrotrons such as the SIS18 at Helmholtzzentrum für Schwerionenforschung, Helmholtz Centre for Heavy Ion Research (GSI, coherent oscillations of the particle bunches are damped by rf feedback systems to increase the stability and to improve the beam quality. In the longitudinal direction, important modes are the coherent longitudinal dipole and quadrupole oscillation. In this paper we present a new and rigorous approach to analyze the longitudinal feedback to damp these modes. The results are applied to the rf feedback loop at GSI that damps the quadrupole mode. The stability analysis is compared with simulations and is in good agreement with results of a beam experiment. Finally, we summarize practical implications for the operation of the feedback system regarding performance and stability.

  10. LHC MD 1279: Bunch Flattening in Physics

    CERN Document Server

    AUTHOR|(CDS)2073675; Baudrenghien, Philippe; Esteban Muller, Juan; Shaposhnikova, Elena; CERN. Geneva. ATS Department

    2017-01-01

    Vertex reconstruction is not accurate enough for LHCb when the bunch length in physics shrinks below about 0.9 ns. The end-of-fill MD studies presented here proved that bunch flattening using sinusoidal RF modulation is a loss-free method to increase the r.m.s. bunch length and flatten the bunch profile. Furthermore, the optimum modulation parameters to be used in physics have been identified. Subsequently, bunch flattening in physics was used operationally with a modulation frequency of 98.75 % of the central synchrotron frequency and 0.6 modulation amplitude, resulting in a 150-200 ps increase in the BQM-measured bunch length. A ‘mid-of-fill’ test at arrival to flat top revealed that also the bunch distribution created by the controlled emittance blow-up during the ramp is affected when bunch flattening is applied. The measurements took place on 17th June and the 4th, 7th and 22nd July 2016. Operational cases are shown as well.

  11. How to measure path length?

    NARCIS (Netherlands)

    Stroeven, P.

    2015-01-01

    Path length measuring is a relevant engineering problem. Leonardo Da Vinci designed for the military appropriate equipment, the podometer, to do so. Modern equipment such as step meters and map meters are quite similar to Da Vinci?s design, despite geometrical statistical - stereological - methods

  12. Fast Faraday cup to measure neutralized drift compression in intense ion charge bunches

    Directory of Open Access Journals (Sweden)

    A. B. Sefkow

    2006-05-01

    Full Text Available Heavy ion drivers for heavy ion fusion and high energy density physics applications use space-charge-dominated ion beams which must undergo longitudinal bunch compression in order to meet the requisite beam intensities desired at the target. The Neutralized Drift Compression Experiment-1A (NDCX-1A at Lawrence Berkeley National Laboratory is used to determine the effective limits of neutralized drift compression, which occurs due to an imposed longitudinal velocity tilt on the drifting beam and subsequent neutralization of the beam’s space charge with background plasma. The accurate and temporally resolved measurement of the ion beam’s current and pulse length, which has been longitudinally compressed to a few nanoseconds duration at its focal plane, is a critical diagnostic. This paper describes the design and experimental results for a fast and accurate ion beam probe, which reliably measures the absolute beam current in the presence of high density plasma at the focal plane as a function of time. A particle-in-cell code has been used to model the propagation of the intense ion beam and to design the diagnostic probe.

  13. Real-time monitoring of longitudinal electron bunch parameters by intensity-integrated and spectroscopic measurements of single coherent THz pulses; Echtzeitbestimmung longitudinaler Elektronenstrahlparameter mittels absoluter Intensitaets- und Spektralmessung einzelner kohaerenter THz Strahlungspulse

    Energy Technology Data Exchange (ETDEWEB)

    Wesch, Stephan

    2012-12-15

    High-gain free-electron lasers (FELs) generate intense and monochromatic photon pulses with few tens of femtosecond duration. For this purpose, electron beams are accelerated to relativistic energies and shrunk longitudinally down to micrometer size.The diagnosis of theses compressed electron bunches is a challenge especially for MHz bunch repetition rates as provided by the FEL FLASH in Hamburg. In this thesis, coherently emitted THz radiation of single electron bunches were investigated, on which the longitudinal structure is imprinted. Two instruments were used: First, the FLASH bunch compression monitors, relying on the integrated intensity measurement of diffraction radiation, were modified to determine the overall length of every bunch behind the two bunch compressors (BC). A model was developed showing that their response is independent of the exact bunch shape for lengths below 200 {mu}m (rms). This could experimentally be verified in the range between 50 and 190 {mu}m within 7% accuracy for themonitor behind the last BC by comparison with measurements with the transverse deflecting structure (TDS). Second, a single-shot spectrometer with five staged reflective blazed gratings has been designed, build and commissioned. With its two grating sets, the wavelength ranges from 5.5 to 44 {mu}m and 45 to 440 {mu}m can be simultaneously detected by 118 fast pyroelectric elements. Measurements based on transition radiation spectra were compared with profiles recorded by the TDS.The shape of the spectra as well as the reconstructed temporal profiles (using the Kramers-Kronig relation for phase retrieval) are in excellent agreement. For bunches with a charge of 50 pC, bunch lengths down to 5 {mu}m (fhwm) could be detected.

  14. Structural changes in bunched crystalline ion beams

    CERN Document Server

    Bussmann, M; Schätz, T; Habs, D

    2003-01-01

    Measurements of the spatial distribution of bunched crystalline ion beams in the radio frequency quadrupole storage ring PALLAS are presented for different ratios of the longitudinal and the transverse confinement strengths. The length of highly elongated crystalline ion bunches and its dependence on the bunching voltage is compared to predictions for a one-dimensional ion string and three-dimensional space-charge-dominated beams. The length is found to be considerably shorter than that predicted by the models. Furthermore, the scaling of the length with the bunching voltage is shown to differ from the expected inverse cube root scaling. These differences can partially be attributed to the formation of a mixed crystalline structure. Additionally, a concise mapping of the structural transition from a string to a zig-zag configuration as a function of the ratio of the confinement strengths is presented, which in a similar way deviates from the predictions.

  15. Studies of longitudinal profile of electron bunches and impedance measurements at Indus-2 synchrotron radiation source

    Energy Technology Data Exchange (ETDEWEB)

    Garg, Akash Deep, E-mail: akash-deep@rrcat.gov.in [Beam Diagnostics Section (BDS), Indus Operations, Beam Dynamics and Diagnostics Division (IOBDD), Raja Ramanna Centre for Advanced Technology, Indore 452 013, M.P. (India); Homi Bhabha National Institute (HBNI) at Raja Ramanna Centre for Advanced Technology, Indore (India); Yadav, S.; Kumar, Mukesh; Shrivastava, B.B.; Karnewar, A.K.; Ojha, A.; Puntambekar, T.A. [Beam Diagnostics Section (BDS), Indus Operations, Beam Dynamics and Diagnostics Division (IOBDD), Raja Ramanna Centre for Advanced Technology, Indore 452 013, M.P. (India)

    2016-04-01

    Indus-2 is a 3rd generation synchrotron radiation source at the Raja Ramanna Centre for Advanced Technology (RRCAT) in India. We study the longitudinal profile of electrons in Indus-2 by using dual sweep synchroscan streak camera at visible diagnostic beamline. In this paper, the longitudinal profiles of electron bunch are analyzed by filling beam current in a single bunch mode. These studies are carried at injection energy (550 MeV) and at ramped beam energy (2.5 GeV). The effects of the wakefield generated interactions between the circulating electrons and the surrounding vacuum chamber are analyzed in terms of measured effects on longitudinal beam distribution. The impedance of the storage ring is obtained by fitting the solutions of Haissinski equation to the measured bunch lengthening with different impedance models. The impedance of storage ring obtained by a series R+L impedance model indicates a resistance (R) of 1350±125 Ω, an inductance (L) of 180±25 nH and broadband impedance of 2.69 Ω. These results are also compared with the values obtained from measured synchronous phase advancing and scaling laws. These studies are very useful in better understanding and control of the electromagnetic interactions.

  16. Measurement of self-shaped ellipsoidal bunches from a photoinjector with postacceleration

    Directory of Open Access Journals (Sweden)

    Brendan O’Shea

    2011-01-01

    Full Text Available Recent work has shown the possibility of generating self-shaped ellipsoidal beams with properties commensurate with the requirements of future light sources such as free-electron lasers and inverse Compton sources. In this so-termed “blowout” regime, short laser bunches are transformed via photoemission into short electron bunches which then self-consistently evolve into nearly uniform-density ellipsoids under space-charge forces. We report here on the first blowout studies conducted in collaboration between the UCLA Particle Beam Physics Lab and the Photo Injector Test Facility, Zeuthen (PITZ. The measurements conducted at the PITZ photoinjector facility examine the evolution of 750 pC, 2.7 ps FWHM electron bunches born in an L-band photoinjector and subsequently accelerated through a nine-cell L-band booster for a resulting energy of 12 MeV. These measurements represent the first observations of self-shaped ellipsoid evolution under postinjector acceleration, a key step in demonstrating the utility of such self-shaped beams at higher energy, where the advantages in both transverse and longitudinal and transverse phase space may be exploited in creating very high brightness beams.

  17. The Tevatron bunch by bunch longitudinal dampers

    Energy Technology Data Exchange (ETDEWEB)

    Cheng-Yang Tan and James Steimel

    2002-09-25

    We describe in this paper the Tevatron bunch by bunch dampers. The goal of the dampers is to stop the spontaneous longitudinal beam size blowup of the protons during a store. We will go through the theory and also show the measured results during the commissioning of this system. The system is currently operational and have stopped the beam blowups during a store.

  18. Initial Measurements of CSR from a Bunch-Compressed Beam at APS

    CERN Document Server

    Lumpkin, Alex H; Borland, M; Sereno, N S

    2005-01-01

    The interest in bunch compression to generate higher peak current electron beams with low emittance continues in the free-electron laser (FEL) community. At the Advanced Photon source (APS) we have both an rf thermionic gun and an rf photocathode (PC) gun on the S-band linac. At the 150-MeV point in the linac, we have a flexible chicane bunch compressor whose four dipoles bend the beam in the horizontal plane. There is also a vertical bend dipole after the chicane that allows measurement of energy and horizontal beam size at the imaging screen station to study possible effects on emittance due to coherent synchrotron radiation (CSR) in the chicane. A far-infrared (FIR) coherent radiation monitor is located downstream of the chicane as well. We have begun recommissioning of this device with coherent transition radiation (CTR), but we also have directly observed CSR from the bunch-compressed beam as it transits the vertical dipole and goes into the down leg. The unique geometry allows simultaneous tracking of b...

  19. Slip length measurement using BBM

    Science.gov (United States)

    Ahmadzadegan, Adib; Snoeyink, Craig

    2015-11-01

    We will be presenting experimental characterizations of slip lengths of fluids in nano/micro channels. These channels are becoming increasingly important in sensor and separations applications. However, crucial questions still remain on the mechanisms that govern slip-length behavior. We used Bessel Beam microscopy (BBM), a novel super-resolution imaging system, in conjunction with TIRF system. These two, together led us to be able to do Particle Tracking Velocimetry with significantly higher accuracy than previously possible. We will be presenting results demonstrating the feasibility of this approach and advantages that make this method unique.

  20. Measurements and analysis of a high-brightness electron beam collimated in a magnetic bunch compressor

    Directory of Open Access Journals (Sweden)

    F. Zhou

    2015-05-01

    Full Text Available A collimator located in a magnetic bunch compressor of a linear accelerator driven x-ray free electron laser has many potential applications, such as the removal of horns in the current distribution, the generation of ultrashort beams, and as a diagnostic of the beam slice emittance. Collective effects, however, are a major concern in applying the technique. Systematic measurements of emittance and analysis were performed using a collimator in the first bunch compressor of the Linac Coherent Light Source (LCLS. In the nominal, undercompressed configuration using the collimator we find that the y emittance (nonbending plane is not increased, and the x emittance (in the bending plane is increased by about 25%, in comparison to the injector emittance. From the analysis we conclude that the parasitic effects associated with this method are dominated by coherent synchrotron radiation (CSR, which causes a “systematic error” for measuring slice emittance at the bending plane using the collimation method. In general, we find good agreement between the measurements and simulations including CSR. However, for overcompressed beams at smaller collimator gaps, an extra emittance increase is found that does not agree with 1D simulations and is not understood.

  1. Detector Performance and Upgrade Plans of the Pixel Luminosity Telescope for Online per-Bunch Luminosity Measurement at CMS

    CERN Document Server

    CMS Collaboration

    2017-01-01

    The Pixel Luminosity Telescope (PLT) is a dedicated system for luminosity measurement at the CMS experiment using silicon pixel sensors. It was installed during LS1 and has been providing luminosity measurements throughout Run 2. The online bunch-by-bunch luminosity measurement employs the "fast-or" capability of the pixel readout chip (PSI46) to quickly identify likely tracks at the full 40MHz interaction rate. In addition, the full pixel information is read out at a lower rate, allowing for more detailed offline analysis. In this talk, we will present details of the commissioning, performance and operational history of the currently installed hardware and upgrade plans for LS2.

  2. The Fine Structure of the Longitudinal Machine Impedance Observed with Single Bunches

    CERN Document Server

    Bohl, T; Shaposhnikova, Elena

    1998-01-01

    Using a beam spectrum measurement the detailed structure of the CERN SPS longitudinal machine impedance has been observed over a wide frequency range. Single high intensity proton bunches were injected into the machine with RF off. The spectrum of the unstable bunch modes, produced by the different resonant impedances in the ring, was measured during slow debunching. The maximum mode amplitude as a function of frequency was recorded for many injected bunches. The central frequency of each bunch mode is close to the resonant frequency of the impedance and the width depends upon the bunch length. Using sufficiently long bunches allowed the machine impedance to be seen in detail in the frequency range 100MHz to 4GHz. The low frequency of this range is defined by the initial stable bunch spectrum, and the high frequency by the vacuum chamber cut-off frequency. The dominant peaks in the spectrum have been identified with different impedance sources in the machine - some previously unknown.

  3. Martian Length of Day Measurements from Rovers

    Science.gov (United States)

    Eubanks, T. M.; Bills, B.

    2012-06-01

    Changes in the Martian Length of Day (LOD) can be determined at a scientifically use level by a combination of regular (but not necessarily frequent) range and Doppler measurements from Earth and dead reckoning in a Kalman filter.

  4. Measurement of Sub-Picosecond Electron Bunches via Electro-Optic Sampling of Coherent Transition Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, Timothy John [Northern Illinois U.

    2012-01-01

    Future collider applications as well as present high-gradient laser plasma wakefield accelerators and free-electron lasers operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation or the bunch wakefields with sub-picosecond time resolution. We present results on the single-shot electro-optic spectral decoding of coherent transition radiation from bunches generated at the Fermilab A0 photoinjector laboratory. A longitudinal double-pulse modulation of the electron beam is also realized by transverse beam masking followed by a transverse-to-longitudinal phase-space exchange beamline. Live profile tuning is demonstrated by upstream beam focusing in conjunction with downstream monitoring of single-shot electro-optic spectral decoding of the coherent transition radiation.

  5. Simultaneous detection of longitudinal and transverse bunch signals at ANKA

    Energy Technology Data Exchange (ETDEWEB)

    Kehrer, Benjamin; Blomley, Edmund; Brosi, Miriam; Bruendermann, Erik; Hiller, Nicole; Mueller, Anke-Susanne; Steinmann, Johannes; Schedler, Manuel; Schuh, Marcel; Schoenfeldt, Patrik; Smale, Nigel [Karlsruhe Institute of Technology, Karlsruhe (Germany); Schuetze, Paul [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany)

    2016-07-01

    The ANKA storage ring offers different operation modes including the short-bunch mode with bunch lengths tuned down to a few picoseconds. This can lead to the occurrence of microwave instabilities coupled to the emission of coherent synchrotron radiation (CSR) in the so-called 'bursts'. To study this CSR instability we use several turn-by-turn enabled detector systems to synchronously measure both the THz signal as well as bunch profiles. The different detectors are placed at different locations around the storage ring. Here we discuss the experimental setup and calibration of the various systems' synchronisation.

  6. Carbon Nanotubes: Measuring Dispersion and Length

    Energy Technology Data Exchange (ETDEWEB)

    Fagan, Jeffrey A.; Bauer, Barry J.; Hobbie, Erik K.; Becker, Matthew L.; Hight-Walker, Angela; Simpson, Jeffrey R.; Chun, Jaehun; Obrzut, Jan; Bajpai, Vardhan; Phelan, Fred R.; Simien, Daneesh; Yeon Huh, Ji; Migler, Kalman B.

    2011-03-01

    Advanced technological uses of single-wall carbon nanotubes (SWCNTs) rely on the production of single length and chirality populations that are currently only available through liquid phase post processing. The foundation of all of these processing steps is the attainment of individualized nanotube dispersion in solution; an understanding of the collodial properties of the dispersed SWCNTs can then be used to designed appropriate conditions for separations. In many instances nanotube size, particularly length, is especially active in determining the achievable properties from a given population, and thus there is a critical need for measurement technologies for both length distribution and effective separation techniques. In this Progress Report, we document the current state of the art for measuring dispersion and length populations, including separations, and use examples to demonstrate the desirability of addressing these parameters.

  7. Measurement and analysis of SPS kicker magnet heating and outgassing with Different Bunch Spacing

    CERN Document Server

    Barnes, M J; Cornelis, K; Ducimetière, L; Mahner, E; Papotti, G; Rumolo, G; Senaj, V; Shaposhnikova, E

    2010-01-01

    Fast kicker magnets are used to inject beam into and eject beam out of the CERN SPS accelerator ring. These kickers are generally ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the ferrite yoke can provoke significant beam induced heating, over several hours, even above the Curie temperature of the ferrite. At present the nominal bunch spacing in the SPS is 25 ns, however for an early stage of LHC operation it is preferable to have 50 ns bunch spacing. Machine Development (MD) studies have been carried out with an inter-bunch spacing of 25 ns, 50 ns or 75 ns. For some of the SPS kicker magnets the 75 ns bunch spacing resulted in considerable beam induced heating. In addition the MDs showed that 50 ns bunch spacing could result in a very rapid pressure rise in the kicker magnet and thus cause an interlock. This paper discusses the MD observations of the SPS kickers and analyses the available d...

  8. Distance and Cable Length Measurement System

    Science.gov (United States)

    Hernández, Sergio Elias; Acosta, Leopoldo; Toledo, Jonay

    2009-01-01

    A simple, economic and successful design for distance and cable length detection is presented. The measurement system is based on the continuous repetition of a pulse that endlessly travels along the distance to be detected. There is a pulse repeater at both ends of the distance or cable to be measured. The endless repetition of the pulse generates a frequency that varies almost inversely with the distance to be measured. The resolution and distance or cable length range could be adjusted by varying the repetition time delay introduced at both ends and the measurement time. With this design a distance can be measured with centimeter resolution using electronic system with microsecond resolution, simplifying classical time of flight designs which require electronics with picosecond resolution. This design was also applied to position measurement. PMID:22303169

  9. Distance and Cable Length Measurement System

    Directory of Open Access Journals (Sweden)

    Jonay Toledo

    2009-12-01

    Full Text Available A simple, economic and successful design for distance and cable length detection is presented. The measurement system is based on the continuous repetition of a pulse that endlessly travels along the distance to be detected. There is a pulse repeater at both ends of the distance or cable to be measured. The endless repetition of the pulse generates a frequency that varies almost inversely with the distance to be measured. The resolution and distance or cable length range could be adjusted by varying the repetition time delay introduced at both ends and the measurement time. With this design a distance can be measured with centimeter resolution using electronic system with microsecond resolution, simplifying classical time of flight designs which require electronics with picosecond resolution. This design was also applied to position measurement.

  10. LHC MD 652: Coupled-Bunch Instability with Smaller Emittance (all HOMs)

    CERN Document Server

    AUTHOR|(CDS)2081238; Timko, Helga; CERN. Geneva. ATS Department

    2017-01-01

    The aim of the MD was to measure the coupled-bunch stability from all HOM impedances, with a reduced longitudinal emittance in order to explore the HL-LHC conditions. The acceleration ramp was performed with the nominal beams of 2016, but a reduced target bunch length and RF voltage. With this reduced emittance, the beam remained close but above the single-bunch stability threshold. No coupled-bunch oscillations were observed, so we can conclude that the stability threshold for coupled-bunch instability is not lower than the single-bunch threshold. An interesting observation in the MD was the long-lasting injection oscillations, whose traces can still be seen at arrival to flat top; in agreement with observations in earlier MDs. The measurements took place between 28th October 20:00 and 29th October 05:10.

  11. Temporal Characterization of Electron Beam Bunches with a Fast Streak Camera at the JLab FEL Facility

    CERN Document Server

    Zhang, S; Douglas, D; Hardy, D; Hernandez-Garcia, C; Jordan, K; Neil, G; Shinn, M D

    2005-01-01

    The design and construction of an optical transport that brings synchrotron radiation from electron bunches to a fast streak camera in a remote area has become a useful tool for online observation of bunch length and stability. This paper will report on the temporal measurements we have done, comparison with simulations, and the on-going work for another imaging optical transport system that will make possible the direct measurement of the longitudinal phase space by measuring the bunch length as a function of energy.

  12. Temporal profile monitor based on electro-optic spatial decoding for low-energy bunches

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2017-11-01

    Full Text Available The measurement of electron bunch temporal profile is one of the key diagnostics in accelerators, especially for ultrashort bunches. The electro-optic (EO technique enables the precise longitudinal characterization of bunch electric field in a single-shot and nondestructive way, which can simultaneously obtain and analyze the time jitter between the electron bunch and the synchronized laser. An EO monitor based on spatial decoding for temporal profile measurement and timing jitter recoding has recently been demonstrated and analyzed in depth for low-energy bunches at the Tsinghua Thomson scattering X-ray source. A detailed description of the experimental setup and measurement results are presented in this paper. An EO signal as short as 82 fs (rms is observed with 100  μm gallium phosphide for a 40 MeV electron bunch, and the corresponding length is 106 fs (rms with 300  μm zinc telluride. Owing to the field-opening angle, we propose a method to eliminate the influence of energy factor for bunches with low energy, resulting in a bunch length of ∼60  fs (rms. The monitor is also successfully applied to measure time jitter with approximately 10 fs accuracy. The experiment environment is proved to be the main source of the slow drift, which is removed using feedback control. Consequently, the rms time jitter decreases from 430 fs to 320 fs.

  13. Velocity bunching of high-brightness electron beams

    Directory of Open Access Journals (Sweden)

    S. G. Anderson

    2005-01-01

    Full Text Available Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modern high brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly

  14. VELOCITY BUNCHING OF HIGH-BRIGHTNESS ELECTRON BEAMS

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, S G; Musumeci, P; Rosenzweig, J B; Brown, W J; England, R J; Ferrario, M; Jacob, J S; Thompson, M C; Travish, G; Tremaine, A M; Yoder, R

    2004-10-15

    Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modern high brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS) experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly in ICS experiments

  15. LHC MD 1087: Controlled Longitudinal Emittance Blow-up with Short Bunches

    CERN Document Server

    Timko, Helga; Esteban Muller, Juan; Jaussi, Michael; Lasheen, Alexandre; Shaposhnikova, Elena; CERN. Geneva. ATS Department

    2017-01-01

    The aim of the MD was to study the controlled longitudinal emittance blow-up applied during the ramp with bunches that are slightly shorter than operational. Earlier MDs in 2015 have shown that with a short target bunch length, the blow-up is less controlled and a bifurcation of bunch lengths occurs. The presented measurements show that the bifurcation is independent of the presence of the bunch length feedback, pointing towards an intensity-dependent phenomenon, originating from a synchrotron frequency shift with intensity. Accurate measurements of synchrotron frequency shift with intensity are presented as well. The measurements took place between 22nd August 2016, 19:00 and 23rd August 2016, 04:00.

  16. Electron-bunch lengthening on higher-harmonic oscillations in storage-ring free-electron lasers.

    Science.gov (United States)

    Sei, Norihiro; Ogawa, Hiroshi; Okuda, Shuichi

    2017-09-01

    The influence of higher-harmonic free-electron laser (FEL) oscillations on an electron beam have been studied by measuring its bunch length at the NIJI-IV storage ring. The bunch length and the lifetime of the electron beam were measured, and were observed to have become longer owing to harmonic lasing, which is in accord with the increase of the FEL gain. It was demonstrated that the saturated FEL power could be described by the theory of bunch heating, even for the harmonic lasing. Cavity-length detuning curves were measured for the harmonic lasing, and it was found that the width of the detuning curve was proportional to a parameter that depended on the bunch length. These experimental results will be useful for developing compact resonator-type FELs by using higher harmonics in the extreme-ultraviolet and the X-ray regions.

  17. Automated body hair counting and length measurement.

    Science.gov (United States)

    Vallotton, P; Thomas, N

    2008-11-01

    Hair loss or hair excess is a common condition. There is a growing need to quantitatively assess the success of interventions aimed at replenishing areas that lack hair or at removing hair from areas such as the back, the legs, or the arms. Non-invasive methods that do not require staining are highly desirable because the staining process itself may affect the efficacy of the treatment. We introduce a system based on a flatbed scanner and on novel and sensitive image analysis algorithms to count the number of hairs and their individual length. Additionally, a measure of hair visibility is introduced, which allows assessing objectively the severity of the condition. Our system is able to detect even hairs that are difficult to see to a human observer. It is robust to skin impurities or variations in the skin texture and colour. Scanner imaging ensures a sharp image over the whole field. The system analyses on the order of two images per minute, making it suitable for large clinical studies. Counts delivered by a human counter vs. the software were within 10% of each other (N=12). Based on our results, we expect that the software will be useful to a number of researchers investigating medical and cosmetic issues involving objective assessment of pilosity. The algorithm itself may be of use for other applications.

  18. Photon-bunching measurement after two 25-km -long optical fibers

    Science.gov (United States)

    Halder, M.; Tanzilli, S.; de Riedmatten, H.; Beveratos, A.; Zbinden, H.; Gisin, N.

    2005-04-01

    To show the feasibility of a long-distance partial Bell-state measurement, a Hong-Ou-Mandel experiment with coherent photons is reported. Pairs of degenerate photons at telecommunication wavelength are created by parametric down-conversion in a periodically poled lithium niobate waveguide. The photon pairs are separated in a beam splitter and transmitted via two fibers of 25km . The wave packets are relatively delayed and recombined on a second beam splitter, forming a large Mach-Zehnder interferometer. Coincidence counts between the photons at the two output modes are registered. The main challenge consists in the trade-off between low count rates due to narrow filtering and length fluctuations of the 25-km -long arms during the measurement. For balanced paths a Hong-Ou-Mandel dip with a net visibility of 47.3% is observed, which is close to the maximal theoretical value of 50% developed here. This proves the practicability of a long-distance Bell-state measurement with two independent sources, as, e.g., required in an entanglement swapping configuration in the scale of tens of kilometers.

  19. Beam Diagnostics Based on Time-Domain Bunch-by-Bunch Data

    Energy Technology Data Exchange (ETDEWEB)

    Teytelman, Dmitry

    2000-03-30

    A bunch-by-bunch longitudinal feedback system has been used to control coupled-bunch longitudinal motion and study the behavior of the beam at ALS, SPEAR, PEP-II, and DAPHNE. Each of these machines presents unique challenges to feedback control of unstable motion and data analysis. Here the authors present techniques developed to adapt the feedback system to operating conditions at these accelerators. A diverse array of techniques has been developed to extract information on different aspects of beam behavior from the time-domain data captured by the feedback system. These include measurements of growth and damping rates of coupled-bunch modes, bunch-by-bunch current monitoring, measurements of bunch-by-bunch synchronous phases and longitudinal tunes, beam noise spectra. A technique is presented which uses the longitudinal feedback system to measure transverse growth and damping rates. Techniques are illustrated with data acquired at all of the four abovementioned machines.

  20. Experimental observation of constructive superposition of wakefields generated by electron bunches in a dielectric-lined waveguide

    Directory of Open Access Journals (Sweden)

    S. V. Shchelkunov

    2006-01-01

    Full Text Available We report results from an experiment that demonstrates the successful superposition of wakefields excited by 50 MeV bunches which travel ∼50  cm along the axis of a cylindrical waveguide which is lined with alumina. The bunches are prepared by splitting a single laser pulse prior to focusing it onto the cathode of an rf gun into two pulses and inserting an optical delay in the path of one of them. Wakefields from two short (5–6 psec 0.15–0.35 nC bunches are superimposed and the energy loss of each bunch is measured as the separation between the bunches is varied so as to encompass approximately one wakefield period (∼21   cm. A spectrum of ∼40   TM_{0m} eigenmodes is excited by the bunch. A substantial retarding wakefield (2.65   MV/m·nC for just the first bunch is developed because of the short bunch length and the narrow vacuum channel diameter (3 mm through which they move. The energy loss of the second bunch exhibits a narrow peak when the bunch spacing is varied by only 4 mm (13.5 psec. This experiment is compared with a related experiment reported by a group at the Argonne National Laboratory where the bunch spacing was not varied and a much weaker retarding wakefield (∼0.1   MV/m·nC for the first bunch comprising only about 10 eigenmodes was excited by a train of long (∼9   mm bunches.

  1. Measurements and Analysis of Longitudinal HOM Driven Coupled Bunch Modes in PEP-II Rings

    Energy Technology Data Exchange (ETDEWEB)

    Mastorides, T; Rivetta, C.; Fox, J.D.; Winkle, D.Van; /SLAC

    2008-07-07

    The growth rates of the longitudinal higher-order impedance-driven beam modes have greatly increased since the initial PEP-II design and commissioning. This increase is attributed to the addition of 6 1.2MW RF stations with 8 accelerating cavities in the HER and 2 1.2MW RF stations with 4 accelerating cavities in the LER, which allowed operations at twice the design current and almost four times the luminosity. As a result, the damping requirements for the longitudinal feedback have greatly increased since the design, and the feedback filters and control schemes have evolved during PEP-II operations. In this paper, growth and damping rate data for the higher-order mode (HOM) driven coupled-bunch modes are presented from various PEP-II runs and are compared with historical estimates during commissioning. The effect of noise in the feedback processing channel is also studied. Both the stability and performance limits of the system are analyzed.

  2. Interaction of ultrarelativistic electron and proton bunches with dense plasmas

    CERN Document Server

    Rukhadze, A A

    2012-01-01

    Here we discuss the possibility of employment of ultrarelativistic electron and proton bunches for generation of high plasma wakefields in dense plasmas due to the Cherenkov resonance plasma-bunch interaction. We estimate the maximum amplitude of such a wake and minimum system length at which the maximum amplitude can be generated at the given bunch parameters.

  3. Multi-bunch Feedback Systems

    CERN Document Server

    Lonza, M.

    2014-12-19

    Coupled-bunch instabilities excited by the interaction of the particle beam with its surroundings can seriously limit the performance of circular particle accelerators. These instabilities can be cured by the use of active feedback systems based on sensors capable of detecting the unwanted beam motion and actuators that apply the feedback correction to the beam. Advances in electronic technology now allow the implementation of feedback loops using programmable digital systems. Besides important advantages in terms of flexibility and reproducibility, digital systems open the way to the use of novel diagnostic tools and additional features. We first introduce coupled-bunch instabilities, analysing the equation of motion of charged particles and the different modes of oscillation of a multi-bunch beam, showing how they can be observed and measured. Different types of feedback systems will then be presented as examples of real implementations that belong to the history of multi-bunch feedback systems. The main co...

  4. Generation and Use of Coherent Transition Radiation from Short Electron Bunches

    Energy Technology Data Exchange (ETDEWEB)

    Settakorn, Chitrlada

    2001-08-28

    When accelerated, an electron bunch emits coherent radiation at wavelength longer than or comparable to the bunch length. The coherent radiation intensity scales with the square of the number of electron per bunch and its radiation spectrum is determined by the Fourier Transform of the electron bunch distribution squared. At the SUNSHINE (Stanford University Short Intense Electron Source) facility, electron bunches can be generated as short as {sigma}{sub z} = 36 {micro}m (120 femtosecond duration) and such bunches can emit coherent radiation in the far-infrared. Since a typical number for the electron population in a bunch is 10{sup 8}-10{sup 9}, the coherent radiation intensity is much higher than that of incoherent radiation as well as that of a conventional far-infrared radiation source. This concentrates on coherent transition and diffraction radiation from short electron bunches as a potential high intensity far-infrared radiation source and for sub-picosecond electron bunch length measurements. Coherent transition radiation generated from a 25 MeV beam at a vacuum-metal interface is characterized. Such a high intensity radiation source allows far-infrared spectroscopy to be conducted conveniently with a Michelson interferometer and a room temperature detector. Measurements of the refractive index of silicon are described to demonstrate the possibilities of far-infrared spectroscopy using coherent transition radiation Coherent diffraction radiation, which is closely related to coherent transition radiation, can be considered as another potential FIR radiation source. Since the perturbation by the radiation generation to the electron beam is relatively small, it has the advantage of being a nondestructive radiation source.

  5. Validation of Navigation Ultrasound for Clavicular Length Measurement

    DEFF Research Database (Denmark)

    Høj, Anders Thorsmark; Villa, Chiara; Christensen, Ole M

    2017-01-01

    ultrasound, to deliver accurate measurements seems promising. To examine the reliability and validity of navigation ultrasound for length measurements of the clavicle, a study was performed using length measurements performed before forensic autopsies from 2012 to 2013. In total, 38 bodies with a median age...

  6. Recent Advances and New Techniques in Visualization of Ultra-short Relativistic Electron Bunches

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Dao; /SLAC

    2012-06-05

    Ultrashort electron bunches with rms length of {approx} 1 femtosecond (fs) can be used to generate ultrashort x-ray pulses in FELs that may open up many new regimes in ultrafast sciences. It is also envisioned that ultrashort electron bunches may excite {approx}TeV/m wake fields for plasma wake field acceleration and high field physics studies. Recent success of using 20 pC electron beam to drive an x-ray FEL at LCLS has stimulated world-wide interests in using low charge beam (1 {approx} 20 pC) to generate ultrashort x-ray pulses (0.1 fs {approx} 10 fs) in FELs. Accurate measurement of the length (preferably the temporal profile) of the ultrashort electron bunch is essential for understanding the physics associated with the bunch compression and transportation. However, the shorter and shorter electron bunch greatly challenges the present beam diagnostic methods. In this paper we review the recent advances in the measurement of ultra-short electron bunches. We will focus on several techniques and their variants that provide the state-of-the-art temporal resolution. Methods to further improve the resolution of these techniques and the promise to break the 1 fs time barrier is discussed. We review recent advances in the measurement of ultrashort relativistic electron bunches. We will focus on several techniques and their variants that are capable of breaking the femtosecond time barrier in measurements of ultrashort bunches. Techniques for measuring beam longitudinal phase space as well as the x-ray pulse shape in an x-ray FEL are also discussed.

  7. Tropicalized Lambda Lengths, Measured Laminations and Convexity

    DEFF Research Database (Denmark)

    C. Penner, R.

    of the basic cell decomposition of Riemann's moduli space to other contexts for general moduli spaces of flat connections on a surface. In any case, this discussion drastically simplifies aspects of previous related studies as is explained. Furthermore, a new class of measured laminations relative to an ideal...

  8. From Concrete to Abstract in the Measurement of Length

    Science.gov (United States)

    Stephanou, Andreas; Fisher, William P., Jr.

    2013-09-01

    The concatenation of units of length is widely viewed as the paradigmatic expression of fundamental measurement. Survey, assessment, and test scores in educational and psychological measurement are often interpreted in ways that assume a concatenation of units to have been established, even though these assumptions are rarely stated or tested. A concatenation model for measurement is shown to be equivalent to a Rasch model: any two units of measurement placed end to end must together be of the same length as either one of them added to itself. This additive principle and a concatenation model of measurement together serve as a heuristic guide for organizing two experimental approaches to calibrating instruments for measuring length. The capacity to reproduce the unit of measurement from theory with no need for repeated empirical calibration experiments, as in the geometrical bisection of the line and the resultant halving of the length measure, is highlighted as essential to demonstrating a thorough understanding of the construct.

  9. Determination of electron bunch shape using transition radiation and phase-energy measurements

    Energy Technology Data Exchange (ETDEWEB)

    Crosson, E.R.; Berryman, K.W.; Richman, B.A. [Stanford Univ., CA (United States)] [and others

    1995-12-31

    We present data comparing microbunch temporal information obtained from electron beam phase-energy measurements with that obtained from transition radiation auto-correlation measurements. The data was taken to resolve some of the ambiguities in previous transition radiation results. By measuring the energy spectrum of the electron beam as a function of its phase relative to the accelerating field, phase-energy information was extracted. This data was analyzed using tomographic techniques to reconstruct the phase-space distribution assuming an electron energy dependence of E({var_phi}) = E{sub o} + E{sub acc}cos({var_phi}), where E{sub o} is the energy of an electron entering the field, E{sub acc} is the peak energy gain, and {var_phi} is the phase between the crest of the RF wave and an electron. Temporal information about the beam was obtained from the phase space distribution by taking the one dimensional projection along the time axis. We discuss the use of this technique to verify other transition radiation analysis methods.

  10. Modelling and Measurements of Bunch Profiles at the LHC Flat Bottom

    CERN Document Server

    Papadopoulou, Stefania; Muller, Juan; Papaphilippou, Yannis; Trad, Georges

    2016-01-01

    At the LHC flat bottom the interplay between a series of effects (i.e. intrabeam scattering, longitudinal beam manipulations, non-linearities of the machine, etc) can lead to a population of the tails of the beam distributions, which may become non-Gaussian. This paper presents observations of the evolution of particle distributions in the LHC flat bottom. Novel distribution functions are employed to represent the beam profiles, and used as a guideline for generalising emittance growth rate estimations due to IBS. Finally, an attempt is made to benchmark an IBS Monte-Carlo simulation code, able to track 3D particle distributions, with the measured beam profile evolutions.

  11. Validation of a novel ultrasound measurement of achilles tendon length

    DEFF Research Database (Denmark)

    Barfod, Kristoffer Weisskirchner; Riecke, Anja Falk; Boesen, Anders

    2014-01-01

    PURPOSE: A clinically applicable and accurate method for measuring Achilles tendon length is needed to investigate the influence of elongation of the Achilles tendon after acute rupture. The purpose of this study was to develop and validate an ultrasonographic (US) length measurement...... of the Achilles tendon-aponeurosis complex. METHODS: Both legs of 19 non-injured subjects were examined by magnetic resonance imaging (MRI) and US. The length from calcaneus to the medial head of m. Gastrocnemius was measured by three independent US examiners. Repeated US measurements were performed and compared...... to be further assessed in the setting of acute Achilles tendon rupture. CLINICAL RELEVANCE: This new ultrasound measurement might allow for length measurement of ruptured Achilles tendons in the acute and chronic state after rupture. LEVEL OF EVIDENCE: II....

  12. Self-bunching electron guns

    CERN Document Server

    Mako, F; Weilhammer, Peter

    1999-01-01

    We report on three electron gun projects that are aimed at power tube and injector applications. The purpose of the work is to develop robust electron guns which produce self-bunched, high-current-density beams. We have demonstrated cold emission, long life, and tolerance to contamination. The cold emission process is based on secondary electron emission. FMT has studied this resonant bunching process which gives rise to high current densities (0.01-5 kA/cm/sup 2/), high charge bunches (up to 100 nC/bunch), and short pulses (1-100 ps) for frequencies from 1 to 12 GHz. The beam pulse width is nominally ~5% of the RF period. The first project is the L-Band Micro-Pulse Gun (MPG). Measurements show ~40 ps long microbunches at ~20 A/cm/sup 2/ without contamination due to air exposure. Lifetime testing has been carried out for about 18 months operating at 1.25 GHz for almost 24 hours per day at a repetition rate of 300 Hz and 5 mu s-long macro- pulses. About 5.8*10/sup 13/ micro-bunches or 62,000 coulombs have pass...

  13. Measurement of the electrotonic length constant in cultured muscle fibres

    NARCIS (Netherlands)

    Magchielse, T.; Hooisma, J.; Muijser, H.

    1981-01-01

    The measurement of passive electrical membrane properties in cultured muscle cells is complicated by the fact that the electrotonic length in these cells often exceeds their actual length, leading to serious deviations from the simple infinite cable behaviour. By using very short current pulses for

  14. [Comparison between the tooth length measured by cone-beam CT and the tooth length measured with vernier caliper].

    Science.gov (United States)

    Yang, Yi-qiang; Mi, Zhen-lin; Ge, Zhen-lin

    2013-11-01

    To evaluate the accuracy of cone-bean CT (CBCT) on the measurement of the tooth length. One hundred and sixty single root premolars extracted for orthodontic purposes were selected. The tooth length was measured with vernier caliper. The premolars were divided into 10 groups randomly, 16 premolars in each group.In each group, the teeth were lined in molar area, premolar area, canine area and anterior tooth area in maxilla and mandible. Then CBCT was taken, and the tooth length was measured using the software supplied by the manufacturer in coronal and sagittal plane. Accuracy was compared between vernier caliper measurement and CBCT measurement. The tooth length measured by CBCT was smaller than that measured with the vernier caliper. Significant differences were found in six areas, except the maxillary and mandibular premolar areas. With the increase of mesial-distal inclination or buccolingual torque angle, the difference between tooth length measured by CBCT and that measured with vernier caliper increased. The correlation between buccolingual torque angle (∠X1) and the coronal view of CBCT radiology tooth length (Spearmen index was 7.00, P vernier caliper.

  15. Validity of plant fiber length measurement : a review of fiber length measurement based on kenaf as a model

    Science.gov (United States)

    James S. Han; Theodore. Mianowski; Yi-yu. Lin

    1999-01-01

    The efficacy of fiber length measurement techniques such as digitizing, the Kajaani procedure, and NIH Image are compared in order to determine the optimal tool. Kenaf bast fibers, aspen, and red pine fibers were collected from different anatomical parts, and the fiber lengths were compared using various analytical tools. A statistical analysis on the validity of the...

  16. Effective length measurements of prototype Main Injector Dipole endpacks

    Energy Technology Data Exchange (ETDEWEB)

    Glass, H.D.; Brown, B.C.; Harding, D.J.

    1993-03-03

    An endpack design has been developed for the Fermilab Main Injector Dipole. A major part of the design process was the testing of a series of prototype removable endpacks. The magnetic parameters that were tested included the effective length and the field shape variation. This report presents a description of the measurement techniques and the results for the effective length. The final endpack has an effective length at 1500 A (0.29T) of 2.6 {plus_minus} 0.3 mm greater than the steel length, and the change in effective length from 1500 A to maximum current of 9500 A (1.74T) is {minus}1.88 {plus_minus} 0.05 mm.

  17. Effective length measurements of prototype Main Injector Dipole endpacks

    Energy Technology Data Exchange (ETDEWEB)

    Glass, H.D.; Brown, B.C.; Harding, D.J.

    1993-03-03

    An endpack design has been developed for the Fermilab Main Injector Dipole. A major part of the design process was the testing of a series of prototype removable endpacks. The magnetic parameters that were tested included the effective length and the field shape variation. This report presents a description of the measurement techniques and the results for the effective length. The final endpack has an effective length at 1500 A (0.29T) of 2.6 [plus minus] 0.3 mm greater than the steel length, and the change in effective length from 1500 A to maximum current of 9500 A (1.74T) is [minus]1.88 [plus minus] 0.05 mm.

  18. Holographic Spectroscopy for Rapid Electron Bunch Analysis: Development of an Instrument with THZ Resolved Optical Gating

    Energy Technology Data Exchange (ETDEWEB)

    Sievers, Albert

    2011-10-28

    The main thrust of our project was to apply the concepts of holographic spectroscopy, developed earlier in the visible and near IR spectral regions for satellite mapping, to the THz region in order to measure the spectral signature of the coherent radiation emanating from a relativistic electron bunch to obtain the bunch length itself. There were four major discoveries. (1) In the course of this ground-breaking work we developed and built the first static THz interferometer suitable for the realization of such a holographic Fourier transform spectrometer. Experimental tests and analysis of the observed results have provided the necessary foundation for future development of THz detector arrays optimized for spectroscopic applications. (2) Since such detectors do not exist at the present time our next effort was to find an alternative approach. We explored the electro-optic (EO) detection of the THz pulse using the short pulse of a visible diode laser synchronized to the bunch with the long-term goal aimed at single bunch measurement capability. The main hurdle was found to be the parasitic scattering of the diode radiation in the EO medium. By using the optical Fourier transform of the THz interference pattern the effects of this background were suppressed enough to obtain the spectrum using multiple shot acquisition. During our experiments at the FLASH facility at DESY we determined that for single bunch measurement capability the diode laser has to be able to produce sub 100 ps pulses with peak power of at least 1 W. Since these parameters are quite feasible at the current stage of diode laser science this combination of techniques can be used for single shot measurement of a short electron bunch. (3) In carrying out the above effort a simpler measurement possibility was uncovered involving the visible/nearIR pulse of incoherent radiation produced by the same bunch. This observation made possible the cross-correlation of the THz coherent and visible incoherent

  19. Diagnostic technique applied for FEL electron bunches

    Science.gov (United States)

    Brovko, O.; Grebentsov, A.; Morozov, N.; Syresin, E.; Yurkov, M.

    2016-05-01

    Diagnostic technique applied for FEL ultrashort electron bunches is developed at JINR-DESY collaboration within the framework of the FLASH and XFEL projects. Photon diagnostics are based on calorimetric measurements and detection of undulator radiation. The infrared undulator constructed at JINR and installed at FLASH is used for longitudinal bunch shape measurements and for two-color lasing provided by the FIR and VUV undulators. The pump probe experiments with VUV and FIR undulators provide the bunch profile measurements with resolution of several femtosecond. The new three microchannel plates (MCP) detectors operated in X-ray range are under development now in JINR for SASE1-SASE 3 European XFEL.

  20. Femtosecond electron-bunch dynamics in laser wakefields and vacuum

    Directory of Open Access Journals (Sweden)

    A. G. Khachatryan

    2007-12-01

    Full Text Available Recent advances in laser wakefield acceleration demonstrated the generation of extremely short (with a duration of a few femtoseconds relativistic electron bunches with relatively low (of the order of couple of percent energy spread. In this article we study the dynamics of such bunches in drift space (vacuum and in channel-guided laser wakefields. Analytical solutions were found for the transverse coordinate of an electron and for the bunch envelope in the wakefield in the case of arbitrary change in the energy. Our results show strong bunch dynamics already on a millimeter scale propagation distance both in plasma and in vacuum. When the bunch propagates in vacuum, its transverse sizes grow considerably; the same is observed for the normalized bunch emittance that worsens the focusability of the bunch. A scheme of two-stage laser wakefield accelerator with small drift space between the stages is proposed. It is found that fast longitudinal betatron phase mixing occurs in a femtosecond bunch when it propagates along the wakefield axis. When bunch propagates off axis, strong bunch decoherence and fast emittance degradation due to the finite bunch length was observed.

  1. Energy spread minimization in a cascaded laser wakefield accelerator via velocity bunching (Conference Presentation)

    Science.gov (United States)

    Zhang, Zhijun

    2017-05-01

    We report the observation of energy-spread compensation of electron bunches in a laser wakefield accelerator in experiment. The compensation was caused by the gradient wakefield in plasma wake, and the energy spectra of the bunches evolved during the acceleration so that we propose a new method to diagnose the longitudinal length of the ultrashort electron bunch. By analyzing the energy spectra of electron bunches with different acceleration length, the wakefield gradient difference and the wakefield slope of the bunch could be estimated by combining with the slippage between the plasma wave and the electron bunch, thus the electron bunches' longitudinal length could be estimated. By applying this new method, the longitudinal length of electron bunches with charge of about 40 pC generated from a laser wakefield accelerator was estimated to be (2.4 ± 2.2) μm in experiment, which was in good agreement with three-dimension particle-in-cell simulations.

  2. Calculation of coupled bunch effects in the synchrotron light source BESSY VSR

    Energy Technology Data Exchange (ETDEWEB)

    Ruprecht, Martin

    2016-02-22

    In the scope of this thesis, the strength of coupled bunch instabilities (CBIs) driven by longitudinal monopole higher order modes (HOMs) and transverse dipole and quadrupole HOMs is evaluated for the upgrade project BESSY Variable Pulse Length Storage Ring (BESSY VSR) at Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH (HZB), based on analytic calculations and tracking simulations, and compared to the performance of an active bunch-by-bunch feedback (BBFB). Algorithms for tracking codes are derived, and a semi-empirical formula for the estimation of transverse quadrupole CBIs is presented. CBI studies are an integral part of the benchmarking of the cavity models for BESSY VSR and have been accompanying and influencing their entire design process. Based on the BESSY VSR cavity model with highly advanced HOM damping, beam stability is likely to be reached with a BBFB system, independent of the bunch fill pattern. Additionally, measurements of CBIs have been performed at BESSY II and the Metrology Light Source of the Physikalisch-Technische Bundesanstalt (MLS), where the longitudinal long range impedance was characterized. Transient beam loading is evaluated by means of analytic formulas and new experimentally verified tracking codes. For the baseline bunch fill pattern of BESSY VSR, it is shown that the particular setup of cavity frequencies amplifies the transient effect on the long bunch, limiting its elongation and potentially resulting in increased Touschek losses.

  3. Infrared single shot diagnostics for the longitudinal profile of the electron bunches at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Delsim-Hashemi, Hossein

    2008-09-15

    The longitudinal profile of electron bunches plays an important role in the design of single-pass free electron lasers and future linear e{sup +}e{sup -} colliders. For the free electron laser FLASH in Hamburg, a longitudinal compression scheme is used which results in an asymmetric longitudinal bunch profile with a 'spike'. This 'spike', which has a very high peak current, is used in a high-gain SASE-FEL process to produce high intensity (about 70 {mu}J) femtosecond photon pulses in the XUV wavelength range. The required high peak current of the electron bunch is realized by confining a large number of electrons in a width, measured in time units, of few tens of femtosecond, making the diagnostics of such bunches a challenge. Furthermore, the operation of facilities such as FLASH shows that single-shot diagnostics is indispensable. It is intuitive to use a time domain method to measure the electron bunch length. However, when the structures present in the bunch profile fall in the femtoseconds range, this is beyond the resolution of time-resolved methods developed so far. In this thesis, a wavelength-domain technique is described that can fulfill both requirements of single shot and high resolution reaching to the femtoseconds range. The amount of charge that is confined in a typical length of several femtoseconds (FWHM of the spike) can be determined by a novel single-shot spectrometer that resolves the coherent radiation (e.g. coherent transition radiation) in the far-infrared and mid-infrared range. Furthermore the extension of this single-shot spectroscopy to shorter wavelengths reaching the near-infrared, makes it possible to investigate the presence of structures in the bunch profile that might correlate or anti-correlate to the SASE intensity. (orig.)

  4. The impact of precise robotic lesion length measurement on stent length selection: ramifications for stent savings.

    Science.gov (United States)

    Campbell, Paul T; Kruse, Kevin R; Kroll, Christopher R; Patterson, Janet Y; Esposito, Michele J

    2015-09-01

    Coronary stent deployment outcomes can be negatively impacted by inaccurate lesion measurement and inappropriate stent length selection (SLS). We compared visual estimate of these parameters to those provided by the CorPath 200® Robotic PCI System. Sixty consecutive patients who underwent coronary stent placement utilizing the CorPath System were evaluated. The treating physician assessed orthogonal images and provided visual estimates of lesion length and SLS. The robotic system was then used for the same measures. SLS was considered to be accurate when visual estimate and robotic measures were in agreement. Visual estimate SLSs were considered to be "short" or "long" if they were below or above the robotic-selected stents, respectively. Only 35% (21/60) of visually estimated lesions resulted in accurate SLS, whereas 33% (20/60) and 32% (19/60) of the visually estimated SLSs were long and short, respectively. In 5 cases (8.3%), 1 less stent was placed based on the robotic lesion measurement being shorter than the visual estimate. Visual estimate assessment of lesion length and SLS is highly variable with 65% of the cases being inaccurately measured when compared to objective measures obtained from the robotic system. The 32% of the cases where lesions were visually estimated to be short represents cases that often require the use of extra stents after the full lesion is not covered by 1 stent [longitudinal geographic miss (LGM)]. Further, these data showed that the use of the robotic system prevented the use of extra stents in 8.3% of the cases. Measurement of lesions with robotic PCI may reduce measurement errors, need for extra stents, and LGM. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Sonographic Measurement of Normal Splenic Length in Korean Adults

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Sang Bum; Cheon, Byung Kook; Kim, Jong Min; Oh, Kyung Seoung; Jung, Gyoo Sik; Huh, Jin Do; Joh, Young Duk [Kosin University College of Medicine, Busan (Korea, Republic of)

    1996-12-15

    To establish upper limit of normal splenic length of Korean adults on ultrasonography and to determice the degree of interobserver and intraobserver variation. Ultrasonographic scans were performed to measure the maximum length of spleen in 105 of 150 adults selected by convenience sampling. Remained 45 cases with any conditions that could alter splenic size were excluded from this study. The maximum length of spleen was measured and correlated with body surface area, patient height, weight, age and sex. In 31 of the 105 adults we evaluated the interobserver and intraobserver variations in sonographic measurements of splenic length obtained by three radiologists in blind fashion. The mean splenic length in 105 adults was 8.56cm ({+-} 0.95). The splenic length positively correlated with body surface area, patient height and weight (P <0.001), and negatively correlated with patient age (P < 0.01). Male spleen (8.87 cm {+-} 1.07) was longer than female spleen (8.35 cm {+-} 0.81) (P < 0.05). The following guidelines are proposed for the upper limit of normal splenic length at different groups of body surface area: no longer than 10 cm at 1.20{approx}1.59 m{sup 2}, 11 cm at1.60{approx}1.79 m{sup 2}, and 12 cm at 1.80{approx}1.99 m{sup 2}. The mean interobserver variation between any two radiologists ranged from 0.32 cm ({+-} 0.29) to 0.39 cm ({+-} 0.33) and interobserver variations were within 1 cm in 96%. The mean intraobserver variations were within 0.5 cm in 91%. The splenic length closely correlated with body surface area, patient height, weight and age. Particularly the upper limit of normal splenic length changed according to body surface area. Interobserver variation about 1 cm and intraobserver variation about 0.5 cm should be considered in the measurement of the splenic length on ultrasonography

  6. Validation of a novel ultrasound measurement of achilles tendon length.

    Science.gov (United States)

    Barfod, Kristoffer Weisskirchner; Riecke, Anja Falk; Boesen, Anders; Hansen, Philip; Maier, Jens Friedrich; Døssing, Simon; Troelsen, Anders

    2015-11-01

    A clinically applicable and accurate method for measuring Achilles tendon length is needed to investigate the influence of elongation of the Achilles tendon after acute rupture. The purpose of this study was to develop and validate an ultrasonographic (US) length measurement of the Achilles tendon-aponeurosis complex. Both legs of 19 non-injured subjects were examined by magnetic resonance imaging (MRI) and US. The length from calcaneus to the medial head of m. Gastrocnemius was measured by three independent US examiners. Repeated US measurements were performed and compared to MRI measurements. Intra-rater and inter-rater reliability and the agreement between MRI and US were determined. Data were evaluated using the intraclass correlation coefficient (ICC), the standard error of the measurement (SEM) and the minimal detectable change (MDC). Intra-rater reliability of US assessment showed no significant differences between test days: ICC 0.96, SEM 4 mm and MDC 10 mm. Inter-rater reliability showed a systematic difference between US observers of 2-5 mm (p = 0.001-0.036); ICC 0.97, SEM 3 mm and MDC 9 mm. MRI measurements were on average 4 mm longer than US (p = 0.001). The novel ultrasound measurement showed good reliability and accuracy. For comparison between groups of non-injured subjects differences of more than 4 mm can be detected. For repeated assessment of individual subjects differences of more than 10 mm can be detected. The measurement needs to be further assessed in the setting of acute Achilles tendon rupture. This new ultrasound measurement might allow for length measurement of ruptured Achilles tendons in the acute and chronic state after rupture. II.

  7. Beam diagnostics based on time-domain bunch-by-bunch data

    Energy Technology Data Exchange (ETDEWEB)

    Teytelman, D.; Fox, J.; Hindi, H.; Limborg, C.; Linscott, I.; Prabhakar, S.; Sebek, J.; Young, A. [Stanford Linear Accelerator Center P.O. Box 4349 Stanford, California 94309 (United States); Drago, A.; Serio, M. [INFN-Laboratori Nazionali di Frascati, P.O. Box 13 I-00044 Frascati (Roma) (Italy); Barry, W.; Stover, G. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road Berkeley, California 94563 (United States)

    1998-12-01

    A bunch-by-bunch longitudinal feedback system has been used to control coupled-bunch longitudinal motion and study the behavior of the beam at ALS, SPEAR, PEP-II, and DA{Phi}NE. Each of these machines presents unique challenges to feedback control of unstable motion and data analysis. Here we present techniques developed to adapt this feedback system to operating conditions at these accelerators. A diverse array of techniques has been developed to extract information on different aspects of beam behavior from the time-domain data captured by the feedback system. These include measurements of growth and damping rates of coupled-bunch modes, bunch-by-bunch current monitoring, measurements of bunch-by-bunch synchronous phases and longitudinal tunes, and beam noise spectra. A technique is presented which uses the longitudinal feedback system to measure transverse growth and damping rates. Techniques are illustrated with data acquired at all of the four above-mentioned machines. {copyright} {ital 1998 American Institute of Physics.}

  8. On measuring the neutron coherent scattering length with ultrahigh ...

    Indian Academy of Sciences (India)

    We propose an order of magnitude improvement in the present five parts in 105 precision of a nondispersive interferometric measurement of the neutron coherent scattering length c. For this purpose we make a judicious selection of the Bragg angle for the interferometer and the sample thickness. The precision is further ...

  9. LHC Longitudinal Single-Bunch Stability Threshold

    CERN Document Server

    Esteban Muller, Juan Federico; Baudrenghien, Philippe; Lasheen, Alexandre; Roggen, Toon; Shaposhnikova, Elena; Timko, Helga; CERN. Geneva. ATS Department

    2016-01-01

    The aim of the MD studies presented here was to determine with a reasonable accuracy the single-bunch longitudinal stability threshold in the LHC. The measurements were performed by placing along the ring 8 or 20 ‘single’ bunches with different intensities but similar longitudinal emittances. Then they were accelerated and bunch stability was observed at arrival to flat top. Combining the results of two measurement sessions, the single bunch stability threshold is estimated to be (2.4 ± 0.2) × 10^11 ppb for an emittance of 1.89 eVs (1.0 ns) at 6.5 TeV with 12 MV RF voltage. Measurements were taken during the MD session MD472 from 22:00 on 20th to 05:00 on 21st July 2015 and session MD365 from 17:00 on 26th to 01:00 on 27th August 2015.

  10. Status of the short bunch operation project at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Hass, Eugen; Kuhl, Alexander; Rossbach, Joerg [University of Hamburg (Germany); Rehders, Marie; Roensch-Schulenburg, Juliane [University of Hamburg (Germany); CFEL, Hamburg (Germany); Schlarb, Holger; Schreiber, Siegfried [DESY, Hamburg (Germany)

    2013-07-01

    The FEL FLASH (Free-Electron Laser in Hamburg) operates between 4.12 and 45 nm. Typically photon pulses between 50 and 200 fs are generated. Many users at FLASH work on pump-probe experiments, where time resolution is determined by the pulse duration. Therefore they have expressed a keen interest in being provided with shorter XUV pulses. The shortest possible SASE pulse is a single longitudinal optical mode of the FEL radiation. The most direct way to realize this at FLASH would be to reduce the electron bunch length to only a few μm at the entrance of the undulator section. In the ideal case a bunch charge of only 20 pC is suited for the generation of such short bunches. Thus a shorter initial bunch length at the photo-cathode can be chosen, which in turn reduces the bunch compression required to reach single mode conditions. A new photo-injector laser with adjustable pulse duration is used to optimize the initial electron bunch length. Beam dynamic studies are being performed to optimize the injection and compression of small charge electron bunches, starting with the pulse parameters of the injector laser. Improvements of important diagnostics are under way to adapt for charges and bunch lengths that are very small compared to standard FLASH operation. An overview and current status of the project is given in this contribution.

  11. Traceability of optical length measurements on sand surfaces

    DEFF Research Database (Denmark)

    Mohaghegh, Kamran; Yazdanbakhsh, Seyed Alireza; Tiedje, Niels Skat

    2016-01-01

    This work concerns traceable measurements on moulds used in automatic casting lines made of green sand, which has a very low strength against the force of a contact probe. A metrological set-up was made based on the use of calibrated workpieces following ISO 15530-3 to determine the uncertainty...... of optical measurements on a sand surface. A new customised sand sample was developed using a hard binder to withstand the contact force of a touch probe, while keeping optical cooperativeness similar to that of green sand. The length of the sample was calibrated using a dial gauge set-up. An optical 3D...... scanner with fringe pattern projection was used to measure the length of a green sand sample (soft sample) with traceability transfer through the hard sample. Results confirm that the uncertainty of the optical scanner on the substituted hard sample is similar to that of the soft sample, so the hard...

  12. KEKB bunch feedback systems

    Energy Technology Data Exchange (ETDEWEB)

    Tobiyama, M.; Kikutani, E. [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

    1996-08-01

    Design and the present status of the bunch by bunch feedback systems for KEKB rings are shown. The detection of the bunch oscillation are made with the phase detection for longitudinal plane, the AM/PM method for transverse plane. Two GHz component of the bunch signal which is extracted with an analog FIR filter is used for the detection. Hardware two-tap FIR filter systems to shift the phase of the oscillation by 90deg will be used for the longitudinal signal processing. The same system will be used with no filtering but with only digital delay for transverse system. The candidate for the kicker and the required maximum power are also estimated. (author)

  13. Precision Neutron Scattering Length Measurements with Neutron Interferometry

    Science.gov (United States)

    Huber, M. G.; Arif, M.; Jacobson, D. L.; Pushin, D. A.; Abutaleb, M. O.; Shahi, C. B.; Wietfeldt, F. E.; Black, T. C.

    2011-10-01

    Since its inception, single-crystal neutron interferometry has often been utilized for precise neutron scattering length, b, measurements. Scattering length data of light nuclei is particularly important in the study of few nucleon interactions as b can be predicted by two + three nucleon interaction (NI) models. As such they provide a critical test of the accuracy 2+3 NI models. Nuclear effective field theories also make use of light nuclei b in parameterizing mean-field behavior. The NIST neutron interferometer and optics facility has measured b to less than 0.8% relative uncertainty in polarized 3He and to less than 0.1% relative uncertainty in H, D, and unpolarized 3He. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons are Bragg diffracted in the blades to produce two spatially separate (yet coherent) beam paths much like an optical Mach-Zehnder interferometer. A gas sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths which is proportional to b. This talk will focus on the latest scattering length measurement for n-4He which ran at NIST in Fall/Winter 2010 and is currently being analyzed.

  14. ACHROMAT WITH LINEAR SPACE CHARGE FOR BUNCHED BEAMS

    Energy Technology Data Exchange (ETDEWEB)

    RAPARIA,D.; ALESSI,J.G.; LEE,Y.Y.; WENG,W.T.

    1998-08-23

    The standard definition for an achromat is a transport line having zero values for the spatial dispersion (R16) and the angular dispersion (RZ6). For a bunched beam with linear space charge this definition of achromaticity does not hold. The linear space charge in the presence of a bend provides coupling between (a) bunch spatial width and bunch length (R1.5) and (b) bunch angular spread and bunch length (R25). Therefore, achromaticity should be redefined as a line having zero values of the spatial dispersion (R16), the angular dispersion (R26), and matrix elements R15 and R25. These additional conditions (R15=R25=0) can be achieved, for example, with two small RF cavities at appropriate locations in the achromat, to cancel space charge effects. An example of the application of this technique to the Spallation Neutron Source (SNS) high energy beam transport line is presented.

  15. Estimation of stature from radiographic measurement of foot dimensions: Truncated foot length may be more reliable than full foot length.

    Science.gov (United States)

    Gwani, Abdullahi Suleiman; Salihu, Abubakar Tijjani; Garba, Isa Sa'idu; Rufa'i, Adamu Ahmad

    2017-02-01

    Foot length has been shown to be a reliable dimension for estimation of stature. However, phalanges of the foot are very small bones and their length may not be proportional to person's stature. Thus, we hypothesized that foot length measured excluding the phalanges, the truncated foot length, may be more reliable in stature estimation than full foot length. This study, therefore, aimed at comparing the accuracy of the regression equations derived from the truncated foot length and the full foot length. The study recruited a sample of 32 young adults (16 males and 16 females) aged from 20 to 35 years. Lateral radiographs of the right feet were obtained for each subject in a bilateral standing position while maintaining equal weight on both feet. Standing height of the participants was measured with a stadiometer. Truncated foot length and full foot length were measured on the lateral radiographs of the foot. Independent t-test was used to check for mean differences in the dimensions between genders. Linear regression analysis was used to determine the equations for stature estimation. Intra and inter-observer reliability were calculated from four precision estimates: absolute technical error of measurement (aTEM), relative technical error of measurement (rTEM), coefficient of reliability (Rr) and coefficient of variation (Cv). All the dimensions measured were significantly larger in males than females. Linear regression equations were derived for estimation of stature using both the truncated foot length and full foot length. The regression equations derived from truncated foot length have larger correlation coefficient, coefficient of determination, adjusted coefficient of determination as well as smaller standard error of estimation than those derived from full foot length. All the precision estimates showed that the measurement errors are within acceptable limits. This study suggests that even if the full foot length is available, excluding the phalanges may

  16. The elementary school teachers’ ability in the length measurement

    Science.gov (United States)

    Julie, Hongki

    2017-09-01

    The purpose of this study was to describe the elementary school teachers' mathematical ability (1) to develop students’ activities which constructed longer than, shorter than, and as long as concepts, (2) to develop students’ activities which constructed standard unit on the length measurement, and (3) to develop a problem which used by student to construct why a conversion activity on the unit of the length was useful in the daily life after they have participated in the Realistic Mathematics Education (RME) workshops. Curry and Outhread said if teachers knew more about the growth of students’ conceptual understanding of the length, they would be better able to teach that topic [4]. Therefore, in the workshop, teachers were asked to learn more on the stages of the measurement teaching and learning process and why each stage was important. This capability was described by the results of a test which was content of four problems given to teachers after they have attended the workshop. Research subjects in this study were 14 elementary school teachers at Yogyakarta. The results of the study were as follows: (1) only four of 14 teachers who had the first ability; (2) all teachers had the second ability; and (3) all the teachers did not have the third ability.

  17. Length-free near infrared measurement of newborn malnutrition

    Science.gov (United States)

    Mustafa, Fatin Hamimi; Bek, Emily J.; Huvanandana, Jacqueline; Jones, Peter W.; Carberry, Angela E.; Jeffery, Heather E.; Jin, Craig T.; McEwan, Alistair L.

    2016-11-01

    Under-nutrition in neonates can cause immediate mortality, impaired cognitive development and early onset adult disease. Body fat percentage measured using air-displacement-plethysmography has been found to better indicate under-nutrition than conventional birth weight percentiles. However, air-displacement-plethysmography equipment is expensive and non-portable, so is not suited for use in developing communities where the burden is often the greatest. We proposed a new body fat measurement technique using a length-free model with near-infrared spectroscopy measurements on a single site of the body - the thigh. To remove the need for length measurement, we developed a model with five discrete wavelengths and a sex parameter. The model was developed using air-displacement-plethysmography measurements in 52 neonates within 48 hours of birth. We identified instrumentation required in a low-cost LED-based screening device and incorporated a receptor device that can increase the amount of light collected. This near-infrared method may be suitable as a low cost screening tool for detecting body fat levels and monitoring nutritional interventions for malnutrition in neonates and young children in resource-constrained communities.

  18. Measurement of radon diffusion length in thin membranes.

    Science.gov (United States)

    Malki, A; Lavi, N; Moinester, M; Nassar, H; Neeman, E; Piasetzky, E; Steiner, V

    2012-07-01

    Building regulations in Israel require the insulating of buildings against radon (222)Rn penetration from soil. In radon-prone areas membranes stretched between the soil and the building foundation are used, together with sealing other possible penetration routes. Designing the radon mitigation procedure requires checking that all sealing materials are practically, radon tight, having a thickness of at least three times the radon diffusion length. In this work, a very simple technique to evaluate the radon diffusion length in thin membranes, using a radon source of known activity and an activated charcoal canister as radon detector is presented. The theoretical formalism and measurement results for polyethylene membranes of different densities obtained in a recent comparison exercise are presented.

  19. Bunch rotation tests at SPS flat top for the AWAKE experiment

    CERN Document Server

    Argyropoulos, T; Bohl, T; Esteban Müller, J F; Petrenko, A; Shaposhnikova, E; Timko, H

    2013-01-01

    This note summarises the results of two MDs on bunch rotation at SPS flat top. The first MD was carried out on 11th July 2012 with the Q26 optics, while the second MD on the 30th October 2012 used the Q20 optics. To obtain a short bunch length, which is important for the plasma wake-field acceleration project AWAKE, the bunches have been rotated in longitudinal phase space on the SPS flat top. The aim of the MDs was to obtain first estimates of what bunch length, intensity, and transverse emittances - which are crucial for the project - can be achieved for high-intensity single bunches.

  20. Bucket shaking stops bunch dancing in Tevatron

    Energy Technology Data Exchange (ETDEWEB)

    Burov, A.; Tan, C.Y.; /Fermilab

    2011-03-01

    Bunches in Tevatron are known to be longitudinally unstable: their collective oscillations, also called dancing bunches, persist without any signs of decay. Typically, a damper is used to stop these oscillations, but recently, it was theoretically predicted that the oscillations can be stabilized by means of small bucket shaking. Dedicated measurements in Tevatron have shown that this method does stop the dancing. According to predictions of Refs. [2,3], the flattening of the bunch distribution at low amplitudes should make the bunch more stable against LLD. An experiment has been devised to flatten the distribution by modulating the RF phase at the low-amplitude synchrotron frequency for a few degrees of amplitude. These beam studies show that stabilisation really happens. After several consecutive shakings, the dancing disappears and the resulting bunch profile becomes smoother at the top. Although not shown in this report, sometimes a little divot forms at the centre of the distribution. These experiments confirm that resonant RF shaking flattens the bunch distribution at low amplitudes, and the dancing stops.

  1. Hollow bunches production

    CERN Document Server

    Hancock, S

    2017-01-01

    Hollow bunches address the issue of high-brightnessbeams suffering from transverse emittance growth in a strongspace charge regime. During the Proton Synchrotron (PS)injection plateau, the negative space charge tune shift canpush the beam onto theQy=6integer resonance. Modify-ing the longitudinal bunch profile in order to reduce the peakline charge density alleviates the detrimental impact of spacecharge. To this end we first produce longitudinally hollowphase space distributions in the PS Booster by exciting aparametric resonance with the phase loop feedback system.These inherently flat bunches are then transferred to the PS,where the beam becomes less prone to the emittance growthcaused by the integer resonance.During the late 2016 machine development sessions inthe PS Booster we profited from solved issues from 2015and managed to reliably extract hollow bunches of1.3eVsmatched longitudinal area. Furthermore, first results to cre-ate hollow bunches with larger longitudinal emittances to-wards the LHC Inject...

  2. Bunch cleaning strategies and experiments at the Advanced Photon Source.

    Energy Technology Data Exchange (ETDEWEB)

    Sereno, N. S.

    1999-04-15

    The Advanced Photon Source (APS) design incorporated a positron accumulator ring (PAR) as part of the injector chain. In order to increase reliability and accommodate other uses of the injector, APS will run with electrons, eliminating the need for the PAR, provided another method of eliminating rf bucket pollution in the APS is found. Satellite bunches captured from an up to 30-ns-long beam from the linac need to be removed in the injector synchrotron and storage ring. The bunch cleaning method considered here relies on driving a stripline kicker with an amplitude modulated (AM) carrier signal where the carrier is at a revolution harmonic sideband corresponding to the vertical tune. The envelope waveform is phased so that all bunches except a single target bunch (eventually to be injected into the storage ring) are resonated vertically into a scraper. The kicker is designed with a large enough shunt impedance to remove satellite bunches from the injection energy of 0.4 GeV up to 1 GeV. Satellite bunch removal in the storage ring relies on the single bunch current tune shift resulting from the machine impedance. Small bunches remaining after initial preparation in the synchrotron may be removed by driving the beam vertically into a scraper using a stripline kicker operating at a sideband corresponding to the vertical tune for small current bunches. In this paper both design specifications and bunch purity measurements are reported for both the injector synchrotron and storage ring.

  3. Comparison of three methods of measuring the atmospheric coherence length

    Science.gov (United States)

    Slavin, Ann C.; Wells, Ann L.; Fugate, Robert Q.; Fried, David L.; Drexler, James J.

    1997-09-01

    In the fall of 1996, we had the opportunity to mneasure the atmospheric coherence length (Fried's r0 parameter) at the STarfire Optical Range using three instruments. Each instrument measured r0 using a different theory and technique. The first instrument, designed and built by Dr. Donald Walters of the Naval Postgraduate School, is based on measuring the MTF of the atmosphere using a stellar image on a one dimensional detector. The second instrument, designed and built by Lockheed Martin engineers at White Sands Missile Range, is based on measuring the differential motion of stellar images. The third technique in this study used short exposure star images taken through the 1.5m telescope and processed by matching the images to shrot exposure theory values of r0. All of the instruments were located at the STarfire Optical Range and data were collected during both day and night hours. This paper presents the results of these measurements and discusses the different techniques in terms of the results obtained.

  4. Measurements of Newton's gravitational constant and the length of day

    Science.gov (United States)

    Anderson, J. D.; Schubert, G.; Trimble, V.; Feldman, M. R.

    2015-04-01

    About a dozen measurements of Newton's gravitational constant, G, since 1962 have yielded values that differ by far more than their reported random plus systematic errors. We find that these values for G are oscillatory in nature, with a period of P = 5.899 +/- 0.062 \\text{yr} , an amplitude of (1.619 +/- 0.103) × 10-14 \\text{m}3 \\text{kg}-1 \\text{s}-2 , and mean-value crossings in 1994 and 1997. However, we do not suggest that G is actually varying by this much, this quickly, but instead that something in the measurement process varies. Of other recently reported results, to the best of our knowledge, the only measurement with the same period and phase is the Length of Day (LOD —defined as a frequency measurement such that a positive increase in LOD values means slower Earth rotation rates and therefore longer days). The aforementioned period is also about half of a solar activity cycle, but the correlation is far less convincing. The 5.9 year periodic signal in LOD has previously been interpreted as due to fluid core motions and inner-core coupling. We report the G/LOD correlation, whose statistical significance is 0.99764 assuming no difference in phase, without claiming to have any satisfactory explanation for it. Least unlikely, perhaps, are currents in the Earth's fluid core that change both its moment of inertia (affecting LOD) and the circumstances in which the Earth-based experiments measure G. In this case, there might be correlations with terrestrial-magnetic-field measurements.

  5. Design of low energy bunch compressors with space charge effects

    Directory of Open Access Journals (Sweden)

    A. He

    2015-01-01

    Full Text Available In this paper, we explore a method to manipulate low energy electron bunches in a space charge dominated regime, and we use this method to design low energy linac bunch compressors to compress electron bunches in a space charge dominated regime. In the method, we use the space charge effects instead of avoiding them; i.e., we use the space charge forces to generate the required energy chirp instead of the ordinary method which uses the rf accelerating system to generate the chirp. We redefine the concepts of the dispersion function and beta functions in a space charge dominated regime to guide the optimization. Using this method, we study the low energy (5–22 MeV linac bunch compressor design to produce short (∼150  fs and small size (∼30  μm bunches for the electron beam slicing project. The low energy linac bunch compressors work in a space charge dominated regime, and the bunches at the downstream of the gun have a negative energy chirp due to the space charge effects. To provide compression for the negative energy chirped bunch, we design a positive R_{56} dispersive section using a four-dipole chicane with several quadrupole magnets. We have designed low energy linac bunch compressors with different photocathode rf guns. For example, one linac bunch compressor with the BNL photocathode electron rf gun has achieved a low energy bunch with the 166 fs rms bunch length, 28 and 31  μm rms beam size in the vertical and horizontal directions, respectively, at 5 MeV with 50 pC charge. Another example with LBNL’s very-high frequency gun has achieved a low energy bunch with the 128 fs rms bunch length, 42 and 25  μm rms beam size in the vertical and horizontal directions, respectively, at 22 MeV with 200 pC charge.

  6. Resistive wall wakefields of short bunches at cryogenic temperatures

    Directory of Open Access Journals (Sweden)

    G. Stupakov

    2015-03-01

    Full Text Available We present calculations of the longitudinal wakefields at cryogenic temperatures for extremely short bunches, characteristic for modern x-ray free electron lasers. The calculations are based on the equations for the surface impedance in the regime of the anomalous skin effect in metals. This paper extends and complements an earlier analysis of B. Podobedov, Phys. Rev. ST Accel. Beams 12, 044401 (2009. into the region of very high frequencies associated with bunch lengths in the micron range. We study in detail the case of a rectangular bunch distribution for parameters of interest of LCLS-II with a superconducting undulator.

  7. Single Bunch Monopole Instability

    Energy Technology Data Exchange (ETDEWEB)

    Podobedov, B.; Heifets, S.; /SLAC

    2005-09-12

    We study single bunch stability with respect to monopole longitudinal oscillations in electron storage rings. Our analysis is different from the standard approach based on the linearized Vlasov equation. Rather, we reduce the full nonlinear Fokker-Planck equation to a Schroedinger-like equation which is subsequently analyzed by perturbation theory. We show that the Haissinski solution [3] may become unstable with respect to monopole oscillations and derive a stability criterion in terms of the ring impedance.

  8. Adaptive method for electron bunch profile prediction

    Directory of Open Access Journals (Sweden)

    Alexander Scheinker

    2015-10-01

    Full Text Available We report on an experiment performed at the Facility for Advanced Accelerator Experimental Tests (FACET at SLAC National Accelerator Laboratory, in which a new adaptive control algorithm, one with known, bounded update rates, despite operating on analytically unknown cost functions, was utilized in order to provide quasi-real-time bunch property estimates of the electron beam. Multiple parameters, such as arbitrary rf phase settings and other time-varying accelerator properties, were simultaneously tuned in order to match a simulated bunch energy spectrum with a measured energy spectrum. The simple adaptive scheme was digitally implemented using matlab and the experimental physics and industrial control system. The main result is a nonintrusive, nondestructive, real-time diagnostic scheme for prediction of bunch profiles, as well as other beam parameters, the precise control of which are important for the plasma wakefield acceleration experiments being explored at FACET.

  9. Creation and Storage of Long and Flat Bunches in the LHC

    CERN Document Server

    Damerau, H

    2005-01-01

    To maximize the luminosity of the Large Hadron Collider (LHC), the collision of particle bunches with a uniform longitudinal particle density is considered for a future upgrade. The benefits of such bunches and their generation by means of special longitudinal beam manipulations are presented in this report. Three possible options are analyzed with respect to their potential luminosity gain at the beam-beam limit: short rectangular bunches held by radio frequency (RF) harmonics using multiples of the nominal RF frequency of 400.8MHz, long and flat bunches held by multiples of 40.08MHz, and so-called superbunches, confined by barrier buckets. The comparison of the three different approaches shows that flat bunches, with an intermediate bunch length of the order of several meters, are capable of producing a comparable luminosity to superbunches, while avoiding most of their inherent disadvantages. Possible schemes to create the bunches with uniform line density are studied and a longitudinal manipulation to com...

  10. Correlation between morphological characters and estimated bunch ...

    African Journals Online (AJOL)

    CHARLES

    2012-06-12

    Jun 12, 2012 ... The objective of this study was to measure and identify the variables that have more influence on bunch weight (BW), and determine a statistical model for predicting yield for the Tropical banana cultivar (cv.). The experiment consisted of a uniformity trial, conducted in Guanambi, Bahia, with a total.

  11. Development and commissioning of a double-prism spectrometer for the diagnosis of femtosecond electron bunches

    Energy Technology Data Exchange (ETDEWEB)

    Wunderlich, Steffen

    2016-12-15

    Free-electron lasers as accelerator-driven light sources and wakefield-based acceleration in plasmas require the knowledge of the longitudinal extension and the longitudinal current profile of the involved electron bunches. These bunches can yield lengths below 10 μm, or durations shorter than approx. 33 fs, as well as charges less than 30 pC. During this work, transition radiation from relativistic electron bunches was investigated in the mid-infrared wavelength regime. A spectrometer using an arrangement of two consecutive zinc selenide prisms was developed, built and commissioned. The instrument covers the spectral range from 2 μm to 18 μm in a single shot. Measurements with the double-prism spectrometer were conducted at the FEL facilities FLASH at DESY in Hamburg, Germany and FELIX at the Radboud Universiteit in Nijmegen, The Netherlands. The assessment of the spectrometer and comparative studies with established diagnostic devices at FLASH show high signal-to-noise ratios at bunch charges below 10 pC and confirm the obtained results.

  12. LHC Report: spring cleaning over, bunches of luminosity

    CERN Multimedia

    CERN Bulletin

    2011-01-01

    Scrubbing was completed on Wednesday 13 April. The run had seen over 1000 bunches per beam successfully circulating at 450 GeV. Measurements showed that electron cloud activity in the cold regions had been suppressed. A decrease of vacuum activity in the warm regions demonstrated that the cleaning had also achieved the required results there. As discussed in the last Bulletin, the scrubbing was performed with high intensity bunches with 50 nanosecond spacing. Given the potential luminosity performance with this spacing (more bunches, higher bunch intensity from the injectors) and in the light of the results of the scrubbing run, the decision was taken to continue the 2011 physics run with this bunch spacing.   A few issues with 50 nanosecond spacing had to be resolved when standard operations for luminosity production resumed. Once things had been tidied up, stable beams were provided for the experiments, firstly with 228 bunches per beam and then with 336 bunches per beam. The 336 bunch fill that w...

  13. Ocular Axial Length Measurement Among Normal Adults Using ...

    African Journals Online (AJOL)

    2017-07-26

    Jul 26, 2017 ... it, and adnexal structures, which support it both within the orbit and external to the orbit. The distance ... orbito-ocular disease, referred for MRI of the brain and/or paranasal sinuses. The referring clinician ... In addition, the difference observed in the length of the IZL among the various age groups was not ...

  14. Beam measurements of the SPS longitudinal impedance

    CERN Document Server

    Lasheen, A

    2017-01-01

    Longitudinal instabilities are one of the main limitationsin the CERN SPS to reach the beam parameters requiredfor the High Luminosity LHC project. In preparation tothe SPS upgrade, possible remedies are studied by perform-ing macroparticle simulations using the machine impedancemodel obtained from electromagnetic simulations and mea-surements. To benchmark the impedance model, the resultsof simulations are compared with various beam measure-ments. In this study, the reactive part of the impedance wasprobed by measuring the quadrupole frequency shift withintensity, obtained from bunch length oscillations at mis-matched injection into the SPS. This method was appliedover many last years to follow up the evolution of the SPSimpedance, injecting bunches with the same bunch length.A novel approach, giving significantly more information,consists in varying the injected bunch length. The compari-son of these measurements with macroparticle simulationsallowed to test the existing model and identify some missingSPS i...

  15. Spins, charge radii and magnetic moments of neutron-rich Mn isotopes measured with bunched beam Collinear Laser Spectroscopy

    CERN Document Server

    AUTHOR|(CDS)2085887; Heylen, Hanne

    In this work, the odd-even $^{51–63}$Mn isotopes have been analyzed using collinear laser spectroscopy, from which the magnetic dipole moment and the change in change in mean square charge radius can be determined. The magnetic moment is very sensitive to the composition of the total nuclear wave function, while the charge radius gives information about the relative size and degree of deformation of the nucleus. An additional advantage of collinear laser spectroscopy is the possibility of direct measurement of the nuclear spin. The main motivation behind the study of these isotopes is to investigate the change in nuclear structure when approaching neutron number N = 40. This region is of interest due to the apparent doubly magic nature of $^{68}$Ni , which is not seen in the N = 40 isotopes of $^{26}$Fe and $^{24}$Cr. Mn, situated between these elements, offers another perspective due to its uncoupled proton. Based on the observed spectra and extracted moments, spins were assigned to $^{59,61,63}$Mn. The ex...

  16. Dynamic Length Metrology (DLM) for measurements with sub-micrometre uncertainty in a production environment

    DEFF Research Database (Denmark)

    De Chiffre, Leonardo; Hansen, Hans Nørgaard; Hattel, Jesper Henri

    2016-01-01

    Conventional length metrology for traceable accurate measurements requires costly temperature controlled facilities, long waiting time for part acclimatisation, and separate part material characterisation. This work describes a method called Dynamic Length Metrology (DLM) developed to achieve sub...

  17. Analysis of bunch by bunch oscillations with bunch trains at injection into LHC at 25 ns bunch spacing

    CERN Document Server

    Bartosik, H

    2012-01-01

    An MD on August 26, 2011 was dedicated to injection studies of bunch trains with 25 ns spacing and nominal intensity of approximately 1×10(11) protons per bunch. Due to an electrical glitch, the MD was stopped after two attempts of injecting a train of 48 bunches for beam 2. Both injections were aborted after less than 0.1 s. In particular, the first attempt with transverse damper on was dumped after 1000 turns while the second attempt with transverse damper off was dumped after 500 turns only. In this note, an analysis of the bunch by bunch oscillation data recorded with the post-mortem system from the transverse damper is presented. The presented data clearly shows the presence of instabilities that affect mainly the second half of the batch. This is compatible with what would be expected qualitatively in the presence of the electron cloud effect.

  18. Bunch-by-Bunch Analysis of the LHC Heavy-Ion Luminosity

    CERN Document Server

    Schaumann, M

    2013-01-01

    After the first run in 2010 [1], the LHC continued its heavy-ion operation with collisions of lead nuclei in late 2011. The beam dynamics of the high intensity lead beams are strongly influenced by intra-beam scattering (IBS), especially on the injection plateau. Each train injected from the SPS spends a different time at injection, introducing significant changes from train to train. Within the trains there is an even larger spread imprinted by the SPS injection plateau. This results in a spread of the luminosity produced in each bunch crossing. The particle losses during collisions are dominated by nuclear electromagnetic processes, leading to a non-exponential intensity decay during the fill and short luminosity lifetime at 3:5Z TeV. The lu- minosity, emittance, intensity and bunch length evolution of the 2011 run was analysed bunch-by-bunch and compared with simulations. Based on this analysis, estimates of the potential luminosity performance at 6:5Z TeV, after the present shutdown, are given.

  19. New diagnostics and cures for coupled-bunch instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakar, S.

    2000-02-14

    Electromagnetic interaction between a charged particle beam and its surroundings causes collective instabilities, which must be controlled if the new light sources and colliders are to meet their design goals. Control requires a combination of passive damping and fast active feedback on an unprecedented technological scale. Efficient instability diagnosis techniques are also needed for machines with large numbers of bunches. This thesis describes new methods of measuring and analyzing coupled-bunch instabilities in circular accelerators, and demonstrates the existence of a new cure. A new technique is demonstrated for simultaneous measurement of growth rates, damping rates and coherent tune shifts of all unstable coupled-bunch eigenmodes from a single 10-25-ms transient snapshot of beam motion. The technique has been used to locate and quantify beam impedance resonances at PEP-II, ALS and SPEAR. This method is faster than existing spectral scan methods by at least an order of magnitude, and has the added advantage of revealing coupled-bunch dynamics in the linear small-signal regime. A method is also presented for estimating beam impedance from multi-bunch fill shape and synchronous phase measurements. Phase space tracking of multi-bunch instabilities is introduced as a ``complete instability diagnostic.'' Digitized multi-bunch data is analyzed offline, to estimate the phase space trajectories of bunches and modes. Availability of phase space trajectories is shown to open up a variety of possibilities, including measurement of reactive impedance, and diagnosis of the fast beam-ion instability. Knowledge gained from longitudinal measurements (all made using a digital longitudinal feedback system) has been used to optimize cavity temperatures, tuner positions and feedback parameters, and also to identify sources of beam noise at the three machines. A matrix-based method is presented for analyzing the beneficial effect of bunch-to-bunch tune variation on

  20. Longitudinal impedance monitoring in the SPS with single short bunches at 26 GeV/c (RF on)

    CERN Document Server

    Bohl, T; Shaposhnikova, E; CERN. Geneva. AB Department

    2008-01-01

    In the course of monitoring the low frequency impedance of the SPS over the years usually the quadrupole frequency shift as a function of intensity is measured with single bunches at 26 GeV/c with RF on using the peak detected signal. The additional acquisition of longitudinal bunch profiles allows the evaluation of various parameters of the injected beam, details of its quadrupole oscillation and the evolution of the bunch length as a function of time. Data acquired between 1999 and 2007 will be analysed in this respect. It will be shown that the bunch length data at 600 ms indicates clearly the effect of the SPS impedance reduction programme realised in 2000/2001 and that from then on the absolute value of the quadrupole frequency shift shows a tendency to increase over the years, indicating an impedance increase. However, it does not allow to monitor unambiguously the changes from one year to the next. The reason that the quadrupole frequency shift is not very well determined is attributed to the lack of r...

  1. [Voice classification in professional singers: the influence of vocal fold length, vocal tract length and body measurements].

    Science.gov (United States)

    Mürbe, D; Roers, F; Sundberg, J

    2011-06-01

    Professional voice performance is strongly affected by the functional adjustments of the structures involved in voice production. Generally, these functional skills are required by means of intensive training. On the other hand, the individual morphology of the larynx and vocal tract limits this functional variability. Thus, to neglect morphological conditions might result in voice problems. The present paper summarizes investigations on the influence of morphological measurements on the voice classification of professional singers. Vocal fold length, vocal tract length and body height have been found to differ systematically between sopranos, mezzosopranos, altos, tenors, baritones and basses. Although the knowledge of morphological measures does not permit a definite assignment or prediction of the individual voice classification, the data are valuable for counseling by voice teachers and phoniatricians. This might contribute to the prevention of voice disorders.

  2. Bunch Compressor Beamlines for the Tesla and S Band Linear Colliders

    CERN Document Server

    Emma, P

    2003-01-01

    A detailed design for a single stage beam bunch length compressor for both the TESLA and the S-Band Linear Collider (SBLC) is presented. Compression is achieved by introducing an energy-position correlation along the bunch with an rf section at zero-crossing phase followed by a short bending section with energy dependent path length (momentum compaction). The motivation for a wiggler design is presented and many of the critical single bunch tolerances are evaluated. A solenoid based spin rotator is included in the design and transverse emittance tuning elements, diagnostics and tuning methods are described. Bunch length limitations due to second order momentum compaction and sinusoidal rf shape are discussed with options for compensation. Finally, the disadvantages of bunch compression using a 180 sup o arc are discussed.

  3. A Novel Diagnostics of Ultrashort Electron Bunches Based on Detection of Coherent Radiation from Bunched Electron Beam in an Undulator

    CERN Document Server

    Saldin, Evgeny L; Yurkov, Mikhail V

    2004-01-01

    We propose a new method for measurements of the longitudinal profile of 100 femtosecond electron bunches for X-ray Free Electron Lasers (XFELs). The method is based on detection of coherent undulator radiation produced by modulated electron beam. Seed optical quantum laser is used to produce exact optical replica of ultrashort electron bunches. The replica is generated in apparatus which consists of an input undulator (energy modulator), and output undulator (radiator) separated by a dispersion section. The radiation in the output undulator is excited by the electron bunch modulated at the optical wavelength and rapidly reaches a hundred-MW-level power. We then use the now-standard method of ultrashort laser pulse-shape measurement, a tandem combination of autocorrelator and spectrum (FROG -- frequency resolved optical gating) providing real-time single-shot measurements of the electron bunch structure. The big advantage of proposed technique is that it can be used to determine the slice energy spread and emi...

  4. Esophageal distensibility measurement: impact on clinical management and procedure length.

    Science.gov (United States)

    Ahuja, N K; Agnihotri, A; Lynch, K L; Hoo-Fatt, D; Onyimba, F; McKnight, M; Okeke, F C; Garcia, P; Dhalla, S; Stein, E; Pasricha, P J; Clarke, J O

    2017-08-01

    Luminal distensibility measurement has demonstrated relevance to various disease processes, though its effects on clinical decision-making have been less well understood. This study aims to characterize the clinical impact of impedance planimetry measurement as well as the learning curve associated with its use in the esophagus. A single provider performed distensibility measurement in conjunction with upper endoscopy for a variety of clinical indications with the functional lumen imaging probe (FLIP) over a period of 21 months. Procedural data were prospectively collected and, along with medical records, retrospectively reviewed. Seventy-three procedures (70 patients) underwent esophageal distensibility measurement over the timeline of this study. The most common procedural indications were known or suspected achalasia (32.9%), dysphagia with connective tissue disease (13.7%), eosinophilic esophagitis (12.3%), and dysphagia with prior fundoplication (9.6%). FLIP results independently led to a change in management in 29 (39.7%) cases and supported a change in management in an additional 15 (20.5%) cases. The most common change in management was a new or amended therapeutic procedure (79.5%). Procedural time added by distensibility measurement was greater among earlier cases than among later cases. The median time added overall was 5 minutes and 46 seconds. Procedural time added varied significantly by procedural indication, but changes in management did not. Distensibility measurement added meaningful diagnostic information that impacted therapeutic decision-making in the majority of cases in which it was performed. Procedural time added by this modality is typically modest and decreases with experience. © The Authors 2017. Published by Oxford University Press on behalf of International Society for Diseases of the Esophagus. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  5. Cervical length measurement: comparison of transabdominal and transvaginal approach

    DEFF Research Database (Denmark)

    Westerway, Sue C; Pedersen, Lars Henning; Hyett, Jon

    2015-01-01

    accurately, particularly if the cervix is short. At 24–34 weeks, a policy of proceeding to TV scan if TA measurement is positive predictive value so is of limited value as a predictive tool for women attending with symptoms and signs...... of preterm labour > 24 weeks gestation. There is no value in TA assessment of the cervix > 36 weeks....

  6. Flat bunches in the LHC

    CERN Document Server

    Shaposhnikova, E; Baudrenghien, P; Mastoridis, T; Muller, J E; Papotti, G; Salvant, B; Timko, H; Bhat, C; Burov, A

    2014-01-01

    A high harmonic RF system which could serve multiple purposes was proposed for the LHC. Possible applications of the second harmonic RF system include beam stabilisation in the longitudinal plane in absence of wide-band longitudinal feedback and reduction of bunch peak line density. Apart from other useful features flat bunches are expected to produce less beam-induced heating below 1 GHz, the frequency region critical for some LHC equipment. The latter however can also be achieved by de-populating the bunch center. This was demonstrated during the dedicated machine development session in the LHC using RF phase modulation. In this paper the results of tests with single bunches and nominal LHC beams are presented and possible use of this technique in LHC operation is discussed.

  7. Measurements of Newton's gravitational constant and the length of day

    OpenAIRE

    Anderson, JD; Schubert, G; Trimble, V.; Feldman, DE

    2015-01-01

    Copyright © EPLA, 2015. About a dozen measurements of Newton's gravitational constant, G, since 1962 have yielded values that differ by far more than their reported random plus systematic errors. We find that these values for G are oscillatory in nature, with a period of P = 5.899 ± 0.062 yr, an amplitude of (1.619 ± 0.103) × 10 -14 m 3 kg -1 s -2 , and mean-value crossings in 1994 and 1997. However, we do not suggest that...

  8. A tool for measuring the bending length in thin wires.

    Science.gov (United States)

    Lorenzini, M; Cagnoli, G; Cesarini, E; Losurdo, G; Martelli, F; Piergiovanni, F; Vetrano, F; Viceré, A

    2013-03-01

    Great effort is currently being put into the development and construction of the second generation, advanced gravitational wave detectors, Advanced Virgo and Advanced LIGO. The development of new low thermal noise suspensions of mirrors, based on the experience gained in the previous experiments, is part of this task. Quasi-monolithic suspensions with fused silica wires avoid the problem of rubbing friction introduced by steel cradle arrangements by directly welding the wires to silica blocks bonded to the mirror. Moreover, the mechanical loss level introduced by silica (φfs ∼ 10(-7) in thin fused silica wires) is by far less than the one associated with steel. The low frequency dynamical behaviour of the suspension can be computed and optimized, provided that the wire bending shape under pendulum motion is known. Due to the production process, fused silica wires are thicker near the two ends (necks), so that analytical bending computations are very complicated. We developed a tool to directly measure the low frequency bending parameters of fused silica wires, and we tested it on the wires produced for the Virgo+ monolithic suspensions. The working principle and a set of test measurements are presented and explained.

  9. Step Bunching and Solution Flow

    Science.gov (United States)

    Chernov, A. A.

    2003-01-01

    Imagine a sequence of equidistant steps parallel to one another on a crystal face growing from solution. Steps may be one or part of a lattice spacing high. With such ideal morphology, the most perfect material is expected to be produced. Sometimes this happens. Much more often, however, steps form bunches, acquire wavy shapes and interlace. With time, these spontaneous perturbations may be increased in amplitude, i.e. the stepped surface becomes morphologically unstable. Interferometric studies of Y.G. Kuznetsov, L.N. Rashkovich, P.G. Vekilov and N.A. Booth and the author demonstrated that the step bunching depends at least on direction and rate of solution flow over the interface, supersaturation and presence of impurities. In particular, if solution and step flow are parallel to one another, the steps convene into bunches. If these flows are antiparallel, the bunches disappear. As the step train propagates, the overall bunch height often increases infinitely. However, we have found recently that if the flow rate is large enough, (approximately 1 meter per second), the bunch height may be limited. All these phenomena come from interaction between steps. The interaction mechanisms are still not fully understood. I plan to overview major approaches to the still unresolved problem on how these dissipative structures on growing crystal face appear and evolve.

  10. Single-bunch beams for BC-75

    Energy Technology Data Exchange (ETDEWEB)

    Sodja, J.; Clendenin, J.E.; Erickson, R.A.; Miller, R.H.

    1983-06-01

    On June 8, 1983, a beam consisting of a single S-band bunch was transported through the linac into the beam switchyard (BSY) and analyzed in the C-line (Beamline 27) at 30 GeV. The C-line toroid 2712 measured an intensity of approximately 2 x 10/sup 9/e/sup -//pulse. The exact intensity was uncertain due to the limited response time of the toroid for fast, single-bunch beams. However, the linear Q intensity monitors (Lin Q) showed the transmission of the beam through the linac between Sectors 2 and 30 to be fairly flat with an intensity of 3 x 10/sup 9/e/sup -//pulse in the final 19 sectors. The CID Faraday cup, which is located adjacent to the Gun Lin Q, was used to check the calibration of the Lin Q.

  11. Measuring body length of male sperm whales from their clicks: the relationship between inter-pulse intervals and photogrammetrically measured lengths.

    Science.gov (United States)

    Growcott, Abraham; Miller, Brian; Sirguey, Pascal; Slooten, Elisabeth; Dawson, Stephen

    2011-07-01

    Sperm whales (Physeter macrocephalus) emit short, broadband clicks which often include multiple pulses. The time interval between these pulses [inter-pulse interval (IPI)] represents the two-way time for a pulse to travel between the air sacs located at either end of the sperm whale's head. The IPI therefore, is a proxy of head length which, using an allometric relationship, can be used to estimate total body length. Previous studies relating IPI to an independent measure of length have relied on very small sample sizes and manual techniques for measuring IPI. Sound recordings and digital stereo photogrammetric measurements of 21 individuals were made off Kaikoura, New Zealand, and, in addition, archived recordings of whales measured with a previous photogrammetric system were reanalyzed to obtain a total sample size of 33 individuals. IPIs were measured automatically via cepstral analysis implemented via a software plug-in for pamguard, an open-source software package for passive acoustic monitoring. IPI measurements were highly consistent within individuals (mean CV=0.63%). The new regression relationship relating IPI (I) and total length (T) was found to be T=1.258I+5.736 (r(2)=0.77, p 11 m) sperm whales. © 2011 Acoustical Society of America

  12. A paired-laser photogrammetric method for in situ length measurement of benthic fishes

    Science.gov (United States)

    Rizzo, Austin A.; Welsh, Stuart A.; Thompson, Patricia A.

    2017-01-01

    Photogrammetry, a technique to obtain measurements from photographs, may be a valid method for measuring lengths of rare, threatened, or endangered species. Photogrammetric methods of measurement are nonintrusive and reduce the possibility of physical damage or physiological stress associated with the capture and handling of individuals. We evaluated precision and accuracy of photogrammetric length measurements relative to board measurements of Greenside Darters Etheostoma blennioides and Variegate Darters E. variatum in an aquarium and applied photogrammetry in a field study of the Diamond Darter Crystallaria cincotta, a federally listed endangered species. Digital photographs were taken of each individual using a waterproof camera equipped with two parallel lasers. Photogrammetric length measurements were digitized with ImageJ software. Agreement between board and photogrammetric measurements were high for Greenside and Variegate darters. The magnitude of differences was small between direct and photogrammetric measurements, ranging from 0.6% to 3.1%, depending on the species measured and the type of measurement taken. These results support photogrammetry as a useful method for obtaining length measurements of benthic stream fishes. Photogrammetric methods allowed for length measurements and an assessment of length frequency of 199 Diamond Darters, informative data for management that could not be collected with conventional measuring-board methods.

  13. Design of a Multi-Bunch BPM for the Next Linear Collider

    CERN Document Server

    Young, A

    2001-01-01

    The Next Linear Collider (NLC) design requires precise control of colliding trains of high-intensity (1.4 x 10 sup 1 sup 0 particles/bunch) and low-emittance beams. High-resolution multi-bunch beam position monitors (BPMs) are required to ensure uniformity across the bunch trains with bunch spacing of 1.4ns. A high bandwidth (approx 350 MHz) multi-bunch BPM has been designed based on a custom-made stripline sum and difference hybrid on a Teflon-based material. High bandwidth RF couplers were included to allow injection of a calibration tone. Three prototype BPMs were fabricated at SLAC and tested in the Accelerator Test Facility at KEK and in the PEP-II ring at SLAC. Tone calibration data and single-bunch and multi-bunch beam data were taken with high-speed (5Gsa/s) digitizers. Offline analysis determined the deconvolution of individual bunches in the multi-bunch mode by using the measured single bunch response. The results of these measurements are presented in this paper.

  14. Significance of axial length monitoring in children with congenital cataract and update of measurement methods.

    Science.gov (United States)

    Zhan, Jiao; Lin, Haotian; Zhang, Xinyu; Chen, Weirong; Liu, Yizhi

    2013-06-01

    Congenital cataract is the main cause of blindness in children, with significantly varying treatment effects. The development of axial length is an important factor that affects the prognosis of these children. However, when compared with the eyes of normal children, the mechanism of growth of the axial length is so complicated that the reported findings differ significantly in terms of the measuring apparatus, assessment methods, and statistical outcome, making the rule of axial length development still unclear. In this paper, we first review the process of axial length development in normal healthy children and compare different hypotheses about certain factors that could affect the development of axial length. The results of some current research about the characteristics of axial length development in congenital cataract children are then reviewed. Lastly, the advantages and disadvantages of current axial length measurements methods are compared and analyzed. The purpose of this review is to improve our understanding of the complexity and importance of axial length development and to suggest better use of axial length monitoring measurements in congenital cataract children for pediatric ophthalmologists, with the hope of offering assistance that will enhance long-term therapeutic effects for these children.

  15. Measurement accuracy and reliability of tooth length on conventional and CBCT reconstructed panoramic radiographs

    Directory of Open Access Journals (Sweden)

    Carlos Flores-Mir

    2014-10-01

    Full Text Available INTRODUCTION: This in vivo study assessed accuracy and reliability of tooth length measurements obtained from conventional panoramic radiographs and CBCT panoramic reconstructions to that of a digital caliper (gold standard. METHODS: The sample consisted of subjects who had CBCT and conventional panoramic radiographic imaging and who required maxillary premolar extraction for routine orthodontic treatment. A total of 48 teeth extracted from 26 subjects were measured directly with digital calipers. Radiographic images were scanned and digitally measured in Dolphin 3D software. Accuracy of tooth length measurements made by CBCT panoramic reconstructions, conventional panoramic radiographs and digital caliper (gold standard were compared to each other by repeated measures one-way ANOVA with Bonferroni correction and by single measures intraclass correlation coefficient. RESULTS: Repeated root length measures with digital calipers, panoramic radiographs and CBCT constructed panoramic-like images were all individually highly reliable. Compared to the caliper (gold standard, tooth measurements obtained from conventional panoramic radiographs were on average 6.3 mm (SD = 2.0 mm longer, while tooth measurements from CBCT panoramic reconstructions were an average of 1.7 mm (SD = 1.2 mm shorter. CONCLUSIONS: In comparison to actual tooth lengths, conventional panoramic radiographs were relatively inaccurate, overestimating the lengths by 29%, while CBCT panoramic reconstructions underestimated the lengths by 4%.

  16. Measurement accuracy and reliability of tooth length on conventional and CBCT reconstructed panoramic radiographs.

    Science.gov (United States)

    Flores-Mir, Carlos; Rosenblatt, Mark R; Major, Paul W; Carey, Jason P; Heo, Giseon

    2014-01-01

    This in vivo study assessed accuracy and reliability of tooth length measurements obtained from conventional panoramic radiographs and CBCT panoramic reconstructions to that of a digital caliper (gold standard). The sample consisted of subjects who had CBCT and conventional panoramic radiographic imaging and who required maxillary premolar extraction for routine orthodontic treatment. A total of 48 teeth extracted from 26 subjects were measured directly with digital calipers. Radiographic images were scanned and digitally measured in Dolphin 3D software. Accuracy of tooth length measurements made by CBCT panoramic reconstructions, conventional panoramic radiographs and digital caliper (gold standard) were compared to each other by repeated measures one-way ANOVA with Bonferroni correction and by single measures intraclass correlation coefficient. Repeated root length measures with digital calipers, panoramic radiographs and CBCT constructed panoramic-like images were all individually highly reliable. Compared to the caliper (gold standard), tooth measurements obtained from conventional panoramic radiographs were on average 6.3 mm (SD = 2.0 mm) longer, while tooth measurements from CBCT panoramic reconstructions were an average of 1.7 mm (SD = 1.2 mm) shorter. In comparison to actual tooth lengths, conventional panoramic radiographs were relatively inaccurate, overestimating the lengths by 29%, while CBCT panoramic reconstructions underestimated the lengths by 4%.

  17. Study on the Effect of Calcium and Potassium Spray on Date Bunch Fading Disorder

    Directory of Open Access Journals (Sweden)

    Hosein Shekofteh

    2017-02-01

    Full Text Available Introduction: Date bunch fading disorder has been one of the most important problems, which caused economic damage to date plantation area of Iran. It has been first reported on Mozafti cultivar in Kahnuj area, Kerman province. It has often been observed on soft and mid ripening cultivars such as Mozafti, Mordaseng and Kalote. Furthermore, it usually appears on Mozafti cultivar when fruits change from Khalal to Rutab stage. The most important symptoms of this disorder are sudden wilting of fruits and necrotic strips on the upper surface of the main bunch stalk. Incidence and development of these symptoms increase by high temperature, low relative humidity, and hot and dry wind. Several research studies have been carried out on this disorder so far, but the only research about the effect of nutrition on disorder was performed by Rosta (2003. The aim of the present study was to investigate the effect of calcium and potassium spray on date bunch fading and some traits of date fruit in Rigan region, Kerman province. Materials and Methods: The experiment was conducted based on randomized complete block designs with three replicates in Rigan located in east south of Kerman province, Iran, in 2012. Treatments were: T1: control, T2: spray of calcium nitrate at the concentration of 5 ppm, T3: spray of potassium sulfate at the concentration of 5 ppm, and T4: combined spray of calcium nitrate and potassium sulfate at the concentration of 5 ppm. Treatments were applied at Kimri, Hobabok and Khalal stages. Sampling was performed from 3 date palms (3 bunches from each date palm were selected randomly at the second date harvest. Totally, the traits of 200 fruits were measured in each date palm. The traits measured in the present study were: fruit length, fruit diameter, fruit weight, stone weight, stone diameter, and bunch fading percentage. Results and Discussions: According to the data of variance analysis, treatments had a significant effect on wet fruit

  18. Highly precise eye length measurements in children aged 3 through 12 years.

    Science.gov (United States)

    Quinn, Graham E; Francis, Ellie L; Nipper, Karen S; Flitcroft, D Ian; Ying, Gui-shuang; Rees, Renee C; Schmid, Gregor F; Maguire, Maureen G; Stone, Richard A

    2003-07-01

    To determine the feasibility, reliability, and validity of using partial coherence interferometry, a noncontact method that detects interference patterns from various layers of the eye, to measure axial length in young children. The right eye of 64 subjects (mean age, 8.4 y; age range, 3.4-12.9 y; best-corrected visual acuity >or=20/30) was measured. Subjects fixated monocularly on the collimated light pattern from a laser diode (the alignment beam) and the operator used a video monitor to align the corneal reflection in the optical path. Axial length was measured during an 0.8-second scan using interference patterns from a collimated short coherence superluminescence diode aligned coaxially with the laser diode. Five series of 16 readings each were obtained. The average axial length for each of the 5 series of readings was calculated. Main Outcome Measure Axial length. Within-subject precision of axial length measurements was high, with an overall SE of measurement of 8 micro m for individual subjects across the 5 sessions (95% confidence interval, +/-16 micro m). Subgroup analysis showed that sex, age, spherical equivalent, and refractive error exerted statistically significant effects on precision, but all of the differences among subgroups were 3 micro m or less and likely to be insignificant clinically. Axial length measured by partial coherence interferometry varied systematically, with factors known to influence eye length (ie, age and refractive error), further validating the measurement method. The partial coherence interferometry technique provides reproducible, extraordinarily precise eye length measurements in young children and should enable novel approaches to study eye growth and refractive development.

  19. Comparison of Wright's Formula and the Dunn Method for Measuring the Umbilical Arterial Catheter Insertion Length

    Directory of Open Access Journals (Sweden)

    Se-ra Min

    2015-04-01

    Conclusion: The use of Wright's formula overall results in superior correct placement of the UAC tip. It may be a more accurate and practical method than the conventional practice for measuring the UAC insertion length in newborns.

  20. Measurement and restoration of equality in length of the lower limbs in total hip replacement.

    Science.gov (United States)

    Hoikka, V; Paavilainen, T; Lindholm, T S; Turula, K B; Ylikoski, M

    1987-01-01

    Alteration of the length of the lower limb was measured in 39 patients undergoing total hip replacement. Radiographs were taken in the erect posture prior to operation and 6 months postoperatively. The inequality of limb length was measured by the difference between the height of the vertices of the femoral heads and by the difference between the lowest points of the ischial tuberosities. The change of the length was measured intraoperatively as the difference observed between two reference points: one above the acetabulum and the other on the proximal femur. Good correlation was obtained between the change of the limb length made intraoperatively and the change in the limb length using the ischial tuberosities as reference points; no correlation was observed when the vertices of the femoral heads were the reference points. Inequality of limb length can be radiologically determined before and after total hip arthroplasty. Femoral and prosthetic heads are not good reference points for measurement. The difference in the height of the ischial tuberosities demonstrates inequality of limb functional length as it reflects the tilting of the pelvis.

  1. Measurement and restoration of equality in length of the lower limbs in total hip replacement

    Energy Technology Data Exchange (ETDEWEB)

    Hoikka, V.; Paavilainen, T.; Lindholm, T.S.; Turula, K.B.; Ylikoski, M.

    1987-08-01

    Alteration of the length of the lower limb was measured in 39 patients undergoing total hip replacement. Radiographs were taken in the erect posture prior to operation and 6 months postoperatively. The inequality of limb length was measured by the difference between the height of the vertices of the fermoral heads and by the difference between the lowest points of the ischial tuberosities. The change of the length was measured intraoperatively as the difference observed between two reference points: One above the acetabulum and the other on the proximal femur. Good correlation was obtained between the change of the limb length made intraoperatively and the change in the limb length using the ischial tuberosities as reference points; no correlation was observed when the vertices of the femoral heads were the reference points. Inequality of limb length can be radiologically determined before and after total hip arthroplasty. Femoral and prosthetic heads are not good reference points for measurement. The difference in the height of ischial tuberosities demonstrates inequality of limb functional length as it reflects the tilting of the pelvis.

  2. The influence of humidity on accuracy length measurement on polymer parts

    DEFF Research Database (Denmark)

    Madruga, Daniel González; Alexiou, A.; Dalla Costa, Giuseppe

    2016-01-01

    The work deals with an experimental study of the influence of humidity on accurate length measurements on ABS parts. Polymer parts absorb water from the ambient until they reach hygroscopic equilibrium. Water content causes an expansion of the polymer part. The relationship between the water...... the experiment ambient conditions. The invar fixture with the inductive probes, with a resolution of 0.1 μm, allows length measurement on 8 ABS parts at the same time. The scale was used to collect the water content variation during the experiment with a resolution of 0.1 mg. The length and weight of the ABS...

  3. Loss factor for short bunches in azimuthally symmetric tapered structures

    Directory of Open Access Journals (Sweden)

    A. Blednykh

    2010-06-01

    Full Text Available We use the program ECHO to study numerically the loss factor of axisymmetric cavities and collimators with and without tapering. We consider a Gaussian driving bunch of length σ, and structures with inner radius b, outer radius d, cavity gap (or collimator inner length g, and taper length L. In all cases we consider a short bunch with σ≪b. For the untapered structures (L=0, in certain regimes, we describe our numerical results using the known expressions for a step transition and for the diffraction model. In addition, we identify new regimes where gb, we present a phenomenological formula which accurately describes the dependence of the loss factor on the parameters σ, b, d, and L. This formula also holds for a tapered cavity with g>d^{2}/σ and d-b>b.

  4. Sonographic measurement of renal length in children: Variation associated with body position.

    Science.gov (United States)

    Nakamura, Michiru; Taniguchi, Nobuyuki; Kawai, Fukiko; Yokota, Kyoko; Ono, Tomoko; Wang, Yi; Shigeta, Kouichiro; Omoto, Kiyoka; Koibuchi, Harumi; Itoh, Kouichi

    2003-09-01

    We ultrasonographically measured renal length in the major axis in children. Here we discuss the differences in measured lengths in the supine and prone positions. In study 1, which included 214 children, more than 60 percent of the kidneys measured longer in the supine than in the prone position. The difference (S-P: length in the supine position minus length in the prone position) was substantially greater in the left kidney. In study 2, we observed the relation between the kidney and the liver or spleen in 60 children prospectively to determine if artifacts had contributed to the observed differences. When the location of the liver or spleen was above the ki dney, which may induce velocity displacement and renal duplication artifacts, the kidney tended to measure longer. We conclude that kidneys tend to measure longer in the supine than in the prone position. Difference in renal length in different positions was greater in the left kidney than in the right kidney. Sonographic artifacts are presumed to contribute to differences in measured length.

  5. Estimation of stature by measuring fibula and ulna bone length in 2443 older adults.

    Science.gov (United States)

    Auyeung, T W; Lee, J S W; Kwok, T; Leung, J; Leung, P C; Woo, J

    2009-12-01

    Estimation of Stature by Measuring Fibula and Ulna Bone Length in 2443 Older Adults. Knee height has been commonly used to estimate stature but may not always be possible in the frail older adults with compromised posture. Measurement of fibula and ulna bone length could be an alternative method. We attempted to develop and validate regression models to predict measured and reported height using age, fibula length, ulna length, hip circumferences and body weight. A cross-sectional survey. The study was conducted in the Jockey Club Centre for Osteoporosis Care and Control, School of Public Health, The Chinese University of Hong Kong. Two thousand four hundred and forty three community-dwelling older Chinese aged from 65 to 98 years were recruited. The standing height, fibula length, ulna length, hip circumference and body weight were measured and the reported height was recorded. Three separate multiple linear regression models were developed to predict measured-height and reported-height respectively. In predicting measured-height by the bone-length model, the mean errors were +0.52 cm (over-estimation) in men and +0.45 cm (over-estimation) in women and the SDs were +/- 3.5 cm in both genders. The 95% limits of agreement were: -6.65 to +7.70 cm for men and -6.59 to +7.49 cm for women. The accuracy and precision of stature estimation by fibula and ulna bone length is comparable to that by knee height. This may be an acceptable alternative method when knee height measurement is difficult or when the knee height caliper is not available.

  6. Prospective Secondary Mathematics Teachers' Pedagogical Knowledge for Teaching the Estimation of Length Measurements

    Science.gov (United States)

    Subramaniam, Karthigeyan

    2014-01-01

    Prospective secondary mathematics teachers' pedagogical knowledge for teaching the estimation of length measurements was investigated by examining their personal benchmarks for measurement estimation. Benchmarks for measurement estimation are the meaningful representations of units that serve to increase one's understanding of…

  7. The Length of a Pestle: A Class Exercise in Measurement and Statistical Analysis.

    Science.gov (United States)

    O'Reilly, James E.

    1986-01-01

    Outlines the simple exercise of measuring the length of an object as a concrete paradigm of the entire process of making chemical measurements and treating the resulting data. Discusses the procedure, significant figures, measurement error, spurious data, rejection of results, precision and accuracy, and student responses. (TW)

  8. Loss Factor of Tapered Structures for Short Bunches

    Energy Technology Data Exchange (ETDEWEB)

    Blednykh, A.

    2011-03-28

    Using the electromagnetic simulation code ECHO, we have found a simple phenomenological formula that accurately describes the loss factor for short bunches traversing an axisymmetric tapered collimator. In this paper, we consider tapered collimators with rectangular cross-section and use the GdfidL code to calculate the loss factor dependence on the geometric parameters for short bunches. The results for both axisymmetric and rectangular collimators are discussed. The behaviour of the impedance of tapered structures for very short bunches in the optical regime has been determined in refs. [10,11]. Here, for the loss factors for two particular geometries, we have studied the departure from the optical regime behaviour as bunch length is increased. In both cases, the ratio of the loss factor for the tapered collimator to the loss factor in the optical regime is a function only of the scaling parameter {sigma}L/d{sup 2}. The fact that the bunch length a and the taper length L appear as a product is consistent with the recent scaling derived by Stupakov in ref. [12], since there is only a weak dependence on g. One noteworthy fact that is not a priori expected is that only the larger radius or vertical half-aperture d appears. The reduction factor is independent of b. Moreover, it is striking that the specific form involving the arctan given in Eq. (5) holds for both geometries, with only the coefficient {mu} differing by a factor of {approx}2 for flat vs round. This suggests that there may be a useful phenomenological form for more general geometries which may follow from natural extensions of Eq. (5). This possibility is presently being investigated.

  9. Nonlinear δf particle simulations of collective excitations and energy-anisotropy instabilities in high-intensity bunched beams

    Directory of Open Access Journals (Sweden)

    Hong Qin

    2007-06-01

    Full Text Available Collective effects with strong coupling between the longitudinal and transverse dynamics are of fundamental importance for applications of high-intensity bunched beams. The self-consistent Vlasov-Maxwell equations are applied to high-intensity finite-length charge bunches, and a generalized δf particle simulation algorithm is developed for bunched beams with or without energy anisotropy. The nonlinear δf method exhibits minimal noise and accuracy problems in comparison with standard particle-in-cell simulations. Systematic studies are carried out under conditions corresponding to strong 3D nonlinear space-charge forces in the beam frame. For charge bunches with isotropic energy, finite bunch-length effects are clearly evident by the fact that the spectra for an infinitely long coasting beam and a nearly spherical charge bunch have strong similarities, whereas the spectra have distinctly different features when the bunch length is varied between these two limiting cases. For bunched beams with anisotropic energy, there exists no exact kinetic equilibrium because the particle dynamics do not conserve transverse energy and longitudinal energy separately. A reference state in approximate dynamic equilibrium has been constructed theoretically, and a quasi-steady state has been established in the simulations for the anisotropic case. Collective excitations relative to the reference state have been simulated using the generalized δf algorithm. In particular, the electrostatic Harris instability driven by strong energy anisotropy is investigated for a finite-length charge bunch. The observed growth rates are larger than those obtained for infinitely long coasting beams. However, the growth rate decreases for increasing bunch length to a value similar to the case of a long coasting beam. For long bunches, the instability is axially localized symmetrically relative to the beam center, and the characteristic wavelength in the longitudinal direction is

  10. Validating a universal model of particle transport lengths with laboratory measurements of suspended grain motions

    Science.gov (United States)

    Naqshband, Suleyman; McElroy, Brandon; Mahon, Robert C.

    2017-05-01

    The mechanics of sediment transport are of fundamental importance for fluvio-deltaic morphodynamics. The present study focuses on quantifying particle motions and trajectories across a wide range of flow conditions. In particular, a continuous model is presented that predicts particle travel distances for saltation and suspension based on Rouse number and relative grain roughness. By utilizing a series of eight video cameras in a plexiglass flume direct measurements of the distributions of particle travel distances (excursion lengths) were obtained. To this end, experiments were carried out in dark under black lights with fluorescent painted plastic and quartz sand particles. For relatively high Rouse numbers indicating bed load dominant transport regime (P≥2.5), particle motion is governed by the effect of gravitational forces (settling velocities) and measured excursion lengths closely follow a Gaussian distribution. For P=2.5, particle motion is equally subjected to both gravitational and turbulent forces. Consequently, measured excursion lengths exhibit a bimodal distribution with two distinct peaks. As turbulent fluctuations increase and dominate particle motion over gravity (P(P=1.8-8.9). Furthermore, measured excursion lengths are observed to fit within the predicted range of excursion lengths with no significant difference between measured excursion lengths of plastic and quartz sand particles.

  11. Standardizing corneal nerve fibre length for nerve tortuosity increases its association with measures of diabetic neuropathy.

    Science.gov (United States)

    Edwards, K; Pritchard, N; Vagenas, D; Russell, A; Malik, R A; Efron, N

    2014-10-01

    Recent studies on corneal markers have advocated corneal nerve fibre length as the most important measure of diabetic peripheral neuropathy. The aim of this study was to determine if standardizing corneal nerve fibre length for tortuosity increases its association with other measures of diabetic peripheral neuropathy. Two hundred and thirty-one individuals with diabetes with either predominantly mild or absent neuropathic changes and 61 control subjects underwent evaluation of diabetic neuropathy symptom score, neuropathy disability score, testing with 10-g monofilament, quantitative sensory testing (warm, cold, vibration detection) and nerve conduction studies. Corneal nerve fibre length and corneal nerve fibre tortuosity were measured using corneal confocal microscopy. A tortuosity-standardised corneal nerve fibre length variable was generated by dividing corneal nerve fibre length by corneal nerve fibre tortuosity. Differences in corneal nerve morphology between individuals with and without diabetic peripheral neuropathy and control subjects were determined and associations were estimated between corneal morphology and established tests of, and risk factors for, diabetic peripheral neuropathy. The tortuosity-standardised corneal nerve fibre length variable was better than corneal nerve fibre length in demonstrating differences between individuals with diabetes, with and without neuropathy (tortuosity-standardised corneal nerve fibre length variable: 70.5 ± 27.3 vs. 84.9 ± 28.7, P diabetes, without neuropathy, while corneal nerve fibre length did not (tortuosity-standardised corneal nerve fibre length variable: 94.3 ± 27.1 vs. 84.9 ± 28.7, P = 0.028; corneal nerve fibre length: 20.1 ± 6.3 vs. 18.4 ± 6.2 mm/mm², P = 0.084). Correlations between corneal nerve fibre length and established measures of neuropathy and risk factors for neuropathy were higher when a correction was made for the nerve tortuosity. Standardizing corneal nerve fibre length for

  12. Instantaneous coherence length measurement of a swept laser source using a Mach-Zehnder interferometer

    Science.gov (United States)

    von Niederhäusern, Tim; Meier, Christoph; Duelk, Marcus; Vorreau, Philipp

    2011-03-01

    We present a measurement method which is capable of measuring the instantaneous coherence length as a function of the wavelength while the source is working at its full sweep rate. The measurement principle is based on the dynamic decrease of fringe contrast as a function of the optical path difference. The measurement setup consists of a free-space Mach-Zehnder interferometer with a variable optical path difference. We present results for instantaneous coherence lengths in a range from 0 mm to 50 mm with a mean standard deviation of 0.42 mm at sweep rates of up to 120 kHz.

  13. Human soleus sarcomere lengths measured using in vivo microendoscopy at two ankle flexion angles.

    Science.gov (United States)

    Chen, Xuefeng; Delp, Scott L

    2016-12-08

    The forces generated by the soleus muscle play an important role in standing and locomotion. The lengths of the sarcomeres of the soleus affect its force-generating capacity, yet it is unknown how sarcomere lengths in the soleus change as a function of ankle flexion angle. In this study, we used microendoscopy to measure resting sarcomere lengths at 10° plantarflexion and 20° dorsiflexion in 7 healthy individuals. Mean sarcomere lengths at 10° plantarflexion were 2.84±0.09µm (mean±S.E.M.), near the optimal length for sarcomere force generation. Sarcomere lengths were 3.43±0.09µm at 20° dorsiflexion, indicating that they were longer than optimal length when the ankle was in dorsiflexion and the muscle was inactive. Our results indicate a smaller sarcomere length difference between two ankle flexion angles compared to estimates from musculoskeletal models and suggest why these models frequently underestimate the force-generating capacity of the soleus. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. The accuracy of axial length measurements in cases of macula-off retinal detachment.

    Science.gov (United States)

    Abou-Shousha, Mohsen; Helaly, Hany Ahmed; Osman, Ihab Mohamed

    2016-04-01

    To assess the accuracy of axial length measurements in cases of macula-off retinal detachment using different methods (optical biometry, A-scan ultrasound, and combined applanation vector-A/B-scan biometry). This prospective clinical study included 100 eyes of 100 patients who underwent vitrectomy alone or phacovitrectomy for macula-off retinal detachment. All patients included signed an informed consent. Preoperative examination of the patients included recording the axial length measurements using optical biometry, A-scan ultrasound, and combined applanation vector-A/B-scan biometry. The mean postoperative IOLMaster axial length after macular reattachment was 26.11 ± 2.91 mm. The mean preoperative IOLMaster axial length with macula-off was 25.32 ± 2.72 mm. The mean preoperative A-scan axial length with macula-off was 25.29 ± 2.80 mm. The mean preoperative vector-A/B-scan axial length with macula-off was 26.03 ± 2.90 mm. The preoperative vector-A/B-scan mean absolute error was 0.59 ± 0.48 D (range, 0.10-2.25 D). Regular methods (optical biometry and A-scan biometry) of measuring the axial length in cases with a detached macula proved to be variable and less accurate. The vector-A/B-scan offered good measurements of the actual axial length in the patients. This was reflected on more accurate postoperative refractive outcome. Copyright © 2016 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.

  15. MEASUREMENT OF ROOT CANAL LENGTH – USE OF AN ELECTROMETRIC DEVICE

    OpenAIRE

    ANAND, SC; KHATTAK, BP; SACHDEVA, VP; CHETAL, BR

    1994-01-01

    The measurement of root canal length is a pre-requisite for successful pulpectomy. The conventional manual and radiographic methods are not very accurate. In the present study, odontometer was used [Group B) to assess its efficacy over the conventional methods (Group A) for recording root canal length. In group A, 36 teeth were treated with pulpectomy while in group B, 51 teeth were managed by the same treatment. It was observed that post operative complications in group B were significantly ...

  16. Measured and simulated transport of 1.9 MeV laser-accelerated proton bunches through an integrated test beam line at 1 Hz

    Directory of Open Access Journals (Sweden)

    M. Nishiuchi

    2010-07-01

    Full Text Available A laser-driven repetition-rated 1.9 MeV proton beam line composed of permanent quadrupole magnets (PMQs, a radio frequency (rf phase rotation cavity, and a tunable monochromator is developed to evaluate and to test the simulation of laser-accelerated proton beam transport through an integrated system for the first time. In addition, the proton spectral modulation and focusing behavior of the rf phase rotation cavity device is monitored with input from a PMQ triplet. In the 1.9 MeV region we observe very weak proton defocusing by the phase rotation cavity. The final transmitted bunch duration and transverse profile are well predicted by the PARMILA particle transport code. The transmitted proton beam duration of 6 ns corresponds to an energy spread near 5% for which the transport efficiency is simulated to be 10%. The predictive capability of PARMILA suggests that it can be useful in the design of future higher energy transport beam lines as part of an integrated laser-driven ion accelerator system.

  17. Single Bunch Longitudinal Instability in the CERN SPS

    CERN Document Server

    Lasheen, Alexandre; Hancock, Steven; Radvilas, Edgaras; Roggen, Toon; Shaposhnikova, Elena

    2016-01-01

    The longitudinal single bunch instability observed in the SPS leads to uncontrolled emittance blow-up and limits the quality of high intensity beams required for the High Luminosity LHC and AWAKE projects at CERN. The present SPS impedance model developed from a thorough survey of machine elements was used in macro-particle simulations (with the code BLonD) of the bunch behavior through the acceleration cycle. Comparison of simulations with measurements of the synchrotron frequency shift, performed on the SPS flat bottom to probe the impedance, show a reasonable agreement. During extensive experimental studies various beam and machine parameters (bunch intensity, longitudinal emittance, RF voltage, with single and double RF systems) were scanned in order to further benchmark the SPS impedance model with measurements and to better understand the mechanism behind the instability. It was found that the dependence of instability threshold on longitudinal emittance and beam energy has an unexpected non-monotonic b...

  18. Air method measurements of apple vessel length distributions with improved apparatus and theory

    Science.gov (United States)

    Shabtal Cohen; John Bennink; Mel Tyree

    2003-01-01

    Studies showing that rootstock dwarfing potential is related to plant hydraulic conductance led to the hypothesis that xylem properties are also related. Vessel length distribution and other properties of apple wood from a series of varieties were measured using the 'air method' in order to test this hypothesis. Apparatus was built to measure and monitor...

  19. Standing Height and its Estimation Utilizing Foot Length Measurements in Adolescents from Western Region in Kosovo

    Directory of Open Access Journals (Sweden)

    Stevo Popović

    2017-10-01

    Full Text Available The purpose of this research is to examine standing height in both Kosovan genders in the Western Region as well as its association with foot length, as an alternative to estimating standing height. A total of 664 individuals (338 male and 326 female participated in this research. The anthropometric measurements were taken according to the protocol of ISAK. The relationships between body height and foot length were determined using simple correlation coefficients at a ninety-five percent confidence interval. A comparison of means of standing height and foot length between genders was performed using a t-test. After that a linear regression analysis were carried out to examine extent to which foot length can reliably predict standing height. Results displayed that Western Kosovan male are 179.71±6.00cm tall and have a foot length of 26.73±1.20cm, while Western Kosovan female are 166.26±5.23cm tall and have a foot length of 23.66±1.06cm. The results have shown that both genders made Western-Kosovans a tall group, a little bit taller that general Kosovan population. Moreover, the foot length reliably predicts standing height in both genders; but, not reliably enough as arm span. This study also confirms the necessity for developing separate height models for each region in Kosovo as the results from Western-Kosovans don’t correspond to the general values.

  20. Standing Height and its Estimation Utilizing Foot Length Measurements in Kosovan Adults: National Survey

    Directory of Open Access Journals (Sweden)

    Stevo Popovic

    2017-07-01

    Full Text Available The purpose of this research is to examine standing height in both Kosovan genders as well as its association with foot length, as an alternative to estimating standing height. A total of 1623 individuals (830 male and 793 female participated in this research. The anthropometric measurements were taken according to the protocol of ISAK. The relationships between body height and foot length were determined using simple correlation coefficients at a ninety-five percent confidence interval. A comparison of means of standing height and foot length between genders was performed using a t-test. Then a linear regression analysis was carried out to examine extent to which foot length can reliably predict standing height. Results displayed that Kosovan male are 179.52±5.96cm tall and have a foot length of 26.22±1.19cm, while Kosovan female are 165.72±4.93cm tall and have a foot length of 23.52±1.01cm. The results have shown that both genders made Kosovans a tall nation but not even close to be in top tallest nations. Moreover, the foot length reliably predicts standing height in both genders; but, not reliably enough as arm span.

  1. Effect of different levels of sharpness processing filter on the measurement accuracy of endodontic file length

    Directory of Open Access Journals (Sweden)

    Nastaran Farhadi

    2016-01-01

    Full Text Available Introduction: The present study was undertaken to evaluate the effect of different levels of sharpness processing filter on the accuracy of endodontic file length determination using digital periapical radiography. Materials and Methods: Forty human single-rooted permanent teeth were selected and International Organization for Standardization (ISO #08 K-files were inserted into the root canals of the teeth. The file lengths were measured with a digital caliper as the gold standard. Digital periapical images were obtained using a phosphor storage plate as a detector. Three levels of sharpness tool of Scanora software program version 5.1 was used to produce enhanced images: Sharpen 1 (mild level, Sharpen 2 (moderate level, and Sharpen 3 (high level. Two radiologists and two endodontists measured file lengths on the original and enhanced images. The measurements were compared using repeated measures ANOVA and Bonferroni tests (α = 0.05. Results: There were no significant differences between the measurement accuracy of original images and that of the Sharpen 1 and Sharpen 2 enhanced images (P > 0.05. However, significant differences were found between the measurement accuracy of original and that of the Sharpen 3 enhanced images (P 0.05. Conclusion: The application of mild and moderate levels of sharpness processing filter did not influence the accuracy of endodontic file length determination. However, high-level sharpness processing filter is not recommended due to its unfavorable effects on measurement accuracy.

  2. Improvement of the accuracy in the optical hematocrit measurement by optimizing mean optical path length.

    Science.gov (United States)

    Oshima, Shiori; Sankai, Yoshiyuki

    2009-09-01

    Optical techniques have been developed to acquire blood information (e.g., hematocrit [Hct], saturation of oxygen, thrombus) noninvasively and continuously in an artificial heart. For the practical use of an optical Hct measurement, Twersky's theory has been shown to be useful and have a good agreement in forward-scattered measurements. However, it was not applied to backward-scattered measurements, which can provide the measurement with a less demanding spatial requirement. Additionally, optimal measurement for accuracy is not well examined. Therefore, we developed an accurate Hct measurement in an artificial heart using current optical devices. To this end, we focused on optimizing an emitter-detector distance to provide a maximum optical path length. We attached optical emitter and detector fibers on Tygon tubing at various distances to measure forward- and backward-scattered light. Fresh bovine blood (Hct: 30-50%) was circulated in the tubing by a nonpulsatile artificial heart. We calculated the optical path length at various emitter-detector distances by fitting the measured optical outputs and the reference Hcts to Twersky's theory. Then, we performed Hct measurements. As a result, Twersky's theory is applicable not only to forward- but also to backward-scattered measurements in the physiogical Hct range. In both forward- and backward-scattered measurements, calculated optical path lengths become maximum at the same emitter-detector distance. The accuracy of Hct measurement is improved two to three times with the emitter-detector distance compared with other distances. The mean error is less than 1 Hct%. This result shows that an accurate Hct measurement is realized by selecting the optimal emitter-detector distance, which provides maximum optical path length defined by Twersky's theory. Our study provides a framework for the practical and less restrictive application of the optical Hct measurement to patients with an artificial heart.

  3. Optical Bunch-By-Bunch Diagnostic System in KEK-PF

    CERN Document Server

    Mochihashi, M; Tanimoto, Y

    2001-01-01

    An optical bunch-by-bunch beam diagnostic system, which can detect oscillations of individual bunches in a multibunch operation, has been developed. The system is composed of a high-speed light shutter and an optical beamoscillation detector. The shutter that consists of a pockels cell and polarizers can be opened or closed in a bunch spacing time (2ns in KEK-PF) and it can select a light pulse corresponding to a certain bunch in a bunch train. The beam oscillation detector can detect oscillations of the pickedout bunch with a spectral analysis method. The diagnostic system has been installed in KEK-PF Beamline-21, and observed vertical oscillation of individual bunches due to an instability in the multi-bunch operation.

  4. Core Length and Spray Width Measurements in Shear Coaxial Injectors from X-ray Radiography Measurements (Briefing Charts)

    Science.gov (United States)

    2015-04-01

    based: insensitive to liquid-gas interfaces Used to study diesel, swirl , gas-centered swirl -coaxial , impingers, and aerated liquid jet injectors...injectors are so named because they rely on the shear between an outer low-density, high-velocity annulus and a high-density, low-velocity inner jet to...compared to two-phase core length measurements from the literature. The core length nondimensionalized by the inner jet diameter was found to scale with

  5. Core Length and Spray Width Measurements in Shear Coaxial Rocket Injectors from X-ray Radiography Measurements

    Science.gov (United States)

    2015-05-01

    cone sprays, impinging- jet sprays and gas-centered swirl -coaxial injectors [11-15]. While x-ray radiography can be performed using a synchro- tron...are so named because they rely on the shear between an outer low-density, high-velocity annulus and a high- density, low-velocity inner jet to atomize...two-phase core length measurements from the literature. The core length nondimensionalized by the inner jet diameter was found to scale with the

  6. Bunch lengthening with bifurcation in electron storage rings

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eun-San; Hirata, Kohji [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

    1996-08-01

    The mapping which shows equilibrium particle distribution in synchrotron phase space for electron storage rings is discussed with respect to some localized constant wake function based on the Gaussian approximation. This mapping shows multi-periodic states as well as double bifurcation in dynamical states of the equilibrium bunch length. When moving around parameter space, the system shows a transition/bifurcation which is not always reversible. These results derived by mapping are confirmed by multiparticle tracking. (author)

  7. New interferometric technique to measure the length (thickness) of opaque objects using a commercial interferometer

    Science.gov (United States)

    Suratkar, Amit R.; Davies, Angela D.; Farahi, Faramarz

    2007-09-01

    Wavelength scanning interferometry offers many advantages over traditional phase shifting interferometry, most significantly the elimination of mechanical movement of the part/s for phase modulation by implementing a tunable light source. Further, Fourier analysis on the interference time history enables this technique to accurately measure distances, treating the distance between two optical surfaces as an interferometric cavity. We propose to use a newly acquired wavelength scanning Fizeau interferometer from Zygo Corporation, the MST (Multiple Surface Transform) to explore the limits of absolute thickness metrology to measure an opaque cavity, such as a gauge block. While transparent cavities can be measured with ease in a Fizeau setup, opaque cavities need additional optics. A two mirror Sagnac configuration in conjunction with the interferometer from Zygo Corporation is used to measure the length (thickness) of a 1 inch gauge block. Current gauge block measurements rely on comparison methods to determine the fractional length with respect to a reference or master gauge block or use techniques which require the absolute length of the gauge block to be previously known. By using wavelength scanning interferometry, the absolute length of the gauge block can be determined directly within limits of the repeatability of the instrument. While other techniques implement a point by point approach for measurement or use interpolation methods, we simply use a large aperture to provide the thickness variation over the sample. Experimental results of a 1 inch gauge block along with an uncertainty estimate are discussed.

  8. Self-amplified coherent spontaneous emission in a free electron laser with “quiet” bunches

    Directory of Open Access Journals (Sweden)

    V. A. Goryashko

    2013-03-01

    Full Text Available For a planar free electron laser (FEL configuration we study self-amplified coherent spontaneous emission driven by a gradient of the bunch current in the presence of different levels of noise in bunches. The longitudinal granularity of the electron bunch density originating from shot noise is maintained throughout the analysis. For the FEL model with the SwissFEL injector bunch parameters, we calculate the probability density distribution of the maximum power of the radiation pulses for different levels of shot noise. It turns out that the temporal coherence quickly increases as the noise level reduces. We also show that the FEL based on coherent spontaneous emission produces almost Fourier transform limited pulses. The analysis indicates that the time-bandwidth product is mainly determined by the bunch length and the interaction distance in an undulator. Calculations of the FEL characteristics for different rise times of the front of the current pulse are performed, and it is found that a reduced level of the power fluctuations is preserved for the bunch current pulse with a front duration up to several FEL wavelengths. We also propose a novel scheme that permits the formation of electron bunches with a reduced level of noise and a high gradient of the current at the bunch tail to enhance coherent spontaneous emission. The presented scheme uses effects of noise reduction and controlled microbunching instability and consists of a laser heater, a bunch compressor, and a shot noise suppression section. We show that shot noise reduction by 2 orders of magnitude in electron bunches produced by the SwissFEL injector can be achieved in a compact noise suppression section. The noise factor and microbunching gain of the overall proposed scheme with and without laser heater are estimated.

  9. An Imaging System for Automated Characteristic Length Measurement of Debrisat Fragments

    Science.gov (United States)

    Moraguez, Mathew; Patankar, Kunal; Fitz-Coy, Norman; Liou, J.-C.; Sorge, Marlon; Cowardin, Heather; Opiela, John; Krisko, Paula H.

    2015-01-01

    The debris fragments generated by DebriSat's hypervelocity impact test are currently being processed and characterized through an effort of NASA and USAF. The debris characteristics will be used to update satellite breakup models. In particular, the physical dimensions of the debris fragments must be measured to provide characteristic lengths for use in these models. Calipers and commercial 3D scanners were considered as measurement options, but an automated imaging system was ultimately developed to measure debris fragments. By automating the entire process, the measurement results are made repeatable and the human factor associated with calipers and 3D scanning is eliminated. Unlike using calipers to measure, the imaging system obtains non-contact measurements to avoid damaging delicate fragments. Furthermore, this fully automated measurement system minimizes fragment handling, which reduces the potential for fragment damage during the characterization process. In addition, the imaging system reduces the time required to determine the characteristic length of the debris fragment. In this way, the imaging system can measure the tens of thousands of DebriSat fragments at a rate of about six minutes per fragment, compared to hours per fragment in NASA's current 3D scanning measurement approach. The imaging system utilizes a space carving algorithm to generate a 3D point cloud of the article being measured and a custom developed algorithm then extracts the characteristic length from the point cloud. This paper describes the measurement process, results, challenges, and future work of the imaging system used for automated characteristic length measurement of DebriSat fragments.

  10. A waveguide overloaded cavity as longitudinal kicker for the DA{Phi}NE bunch-by-bunch feedback system

    Energy Technology Data Exchange (ETDEWEB)

    Gallo, A.; Boni, R.; Ghigo, A.; Marcellini, F.; Serio, M.; Zobov, M. [Instituto Nazionale de Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati

    1996-08-01

    The multibunch operation of DA{Phi}NE calls for a very efficient feedback system to damp the coupled-bunch longitudinal instabilities. A collaboration program among SLAC, LBL and LNF laboratories on this subject led to the development of a time domain, digital system based on digital signal processors that has been already successfully tested at ALS. The feedback chain ends with the longitudinal kicker, an electromagnetic structure capable of transferring the proper energy correction to each bunch. A cavity kicker for the DA{Phi}NE bunch-by-bunch longitudinal feedback system based on a pill-box loaded by six waveguides has been designed and a full-scale aluminium prototype has been fabricated at LNF. Both simulations and measurements have shown a peak shunt impedance of about 750 ohm and a bandwidth of about 220 MHz. The large shunt impedance allows to economize on the costly feedback power. Moreover, the damping waveguides drastically reduce the device HOM longitudinal and transverse impedances. One cavity pre ring will be sufficient to operate the machine up to 30 bunches while a second device per ring together with a feedback power improvement will be necessary to reach the ultimate current. (G.T.)

  11. Stability of measures from children's interviews: the effects of time, sample length, and topic.

    Science.gov (United States)

    Heilmann, John; DeBrock, Lindsay; Riley-Tillman, T Chris

    2013-08-01

    The purpose of this study was to examine the reliability of, and sources of variability in, language measures from interviews collected from young school-age children. Two 10-min interviews were collected from 20 at-risk kindergarten children by an examiner using a standardized set of questions. Test-retest reliability coefficients were calculated for 8 language measures. Generalizability theory (G-theory) analyses were completed to document the variability introduced into the measures from the child, session, sample length, and topic. Significant and strong reliability correlation coefficients were observed for most of the language sample measures. The G-theory analyses revealed that most of the variance in the language measures was attributed to the child. Session, sample length, and topic accounted for negligible amounts of variance in most of the language measures. Measures from interviews were reliable across sessions, and the sample length and topic did not have a substantial impact on the reliability of the language measures. Implications regarding the clinical feasibility of language sample analysis for assessment and progress monitoring are discussed.

  12. Comparative analysis of whole genome sequencing-based telomere length measurement techniques.

    Science.gov (United States)

    Lee, Michael; Napier, Christine E; Yang, Sile F; Arthur, Jonathan W; Reddel, Roger R; Pickett, Hilda A

    2017-02-01

    Telomeres are regions of repetitive DNA at the ends of human chromosomes that function to maintain the integrity of the genome. Telomere attrition is associated with cellular ageing, whilst telomere maintenance is a prerequisite for malignant transformation. Whole genome sequencing (WGS) captures sequence information from the entire genome, including the telomeres, and is increasingly being applied in research and in the clinic. Several bioinformatics tools have been designed to determine telomere content and length from WGS data, and include Motif_counter, TelSeq, Computel, qMotif, and Telomerecat. These tools utilise different approaches to identify, quantify and normalise telomeric reads; however, it is not known how they compare to one another. Here we describe the details and utility of each tool, and directly compare WGS telomere length output with laboratory-based telomere length measurements. In addition, we evaluate the accessibility, practicality, speed, and additional features of each tool. Each tool was tested using a range of telomere read extraction criteria, to determine the optimal parameters for the specific WGS read length. The aim of this article is to improve the accessibility of WGS telomere length measurement tools, which have the potential to be applied to WGS cohorts for clinical as well as research benefit. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Comparison of Perineal Sonographically Measured and Functional Urodynamic Urethral Length in Female Urinary Incontinence

    Directory of Open Access Journals (Sweden)

    Laila Najjari

    2016-01-01

    Full Text Available Objectives. To detect the anatomical insufficiency of the urethra and to propose perineal ultrasound as a useful, noninvasive tool for the evaluation of incontinence, we compared the anatomical length of the urethra with the urodynamic functional urethral length. We also compared the urethral length between continent and incontinent females. Methods. 149 female patients were enrolled and divided into four groups (stress, urge, or mixed incontinence; control. Sonographically measured urethral length (SUL and urodynamic functional urethral length (FUL were analyzed statistically. Standardized and internationally validated incontinence questionnaire ICIQ-SF results were compared between each patient group. Results. Perineal SUL was significantly longer in incontinent compared to continent patients (p<0.0001. Pairwise comparison of each incontinent type (stress, urge, or mixed incontinence with the control group showed also a significant difference (p<0.05. FUL was significantly shorter in incontinent patients than in the control group (p=0.0112. But pairwise comparison showed only a significant difference for the stress incontinence group compared with the control group (p=0.0084 and not for the urge or mixed incontinent group. No clear correlation between SUL, FUL, and ICIQ-SF score was found. Conclusions. SUL measured by noninvasive perineal ultrasound is a suitable parameter in the assessment of female incontinence, since incontinent women show a significantly elongated urethra as a sign of tissue insufficiency, independent of the type of incontinence.

  14. Investigation of photon path length distributions in cloudy atmospheres using GOSAT satellite measurements

    Science.gov (United States)

    Kremmling, Beke; Beirle, Steffen; Penning de Vries, Marloes; Wagner, Thomas

    2017-04-01

    Photon path length distributions in the atmosphere are significantly affected by multiple scattering events by the presence of clouds. Our study investigates photon path length distributions for different cloud situations by combining high-resolution space-based measurements of the oxygen A-band with radiative transfer simulations. The measured spectra originate from the GOSAT TANSO-FTS instrument whose high spectral resolution allows to almost resolve individual absorption lines, which is a prerequisite to our study. The spectra are compared to radiance simulations from the Monte Carlo Model McArtim, which also provides detailed information on the simulated scattering events. Apart from radiance spectra, the simulation output contains information on each simulated scattering event. This can be used to infer photon path length distributions. In addition, also the photon penetration depth and altitude-resolved photon path length distributions for individual altitude layers are derived. To verify the retrieval method, the TANSO-FTS dataset has been screened for collocations with measurements from CALIOP (CALIPSO) and CPR (CloudSat). Well-characterized cloud scenes have been selected for further analysis. The spectral agreement is discussed and cloud characteristics, such as the cloud altitude, thickness and optical depth, are compared to the values measured by CALIOP and CPR.

  15. A Study on Sixth Grade Students' Misconceptions and Errors in Spatial Measurement: Length, Area, and Volume

    Science.gov (United States)

    Tan Sisman, Gulcin; Aksu, Meral

    2016-01-01

    The purpose of the present study was to portray students' misconceptions and errors while solving conceptually and procedurally oriented tasks involving length, area, and volume measurement. The data were collected from 445 sixth grade students attending public primary schools in Ankara, Türkiye via a test composed of 16 constructed-response…

  16. Measuring retinal blood flow in rats using Doppler optical coherence tomography without knowing eyeball axial length

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wenzhong; Yi, Ji; Chen, Siyu [Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Jiao, Shuliang [Department of Biomedical Engineering, Florida International University, Miami, Florida 33174 (United States); Zhang, Hao F., E-mail: hfzhang@northwestern.edu [Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208 and Department of Ophthalmology, Northwestern University, Chicago, Illinois 60611 (United States)

    2015-09-15

    Purpose: Doppler optical coherence tomography (OCT) is widely used for measuring retinal blood flow. Existing Doppler OCT methods require the eyeball axial length, in which empirical values are usually used. However, variations in the axial length can create a bias unaccounted for in the retinal blood flow measurement. The authors plan to develop a Doppler OCT method that can measure the total retinal blood flow rate without requiring the eyeball axial length. Methods: The authors measured the retinal blood flow rate using a dual-ring scanning protocol. The small and large scanning rings entered the eye at different incident angles (small ring: 4°; large ring: 6°), focused on different locations on the retina, and detected the projected velocities/phase shifts along the probing beams. The authors calculated the ratio of the projected velocities between the two rings, and then used this ratio to estimate absolute flow velocity. The authors tested this method in both Intralipid phantoms and in vivo rats. Results: In the Intralipid flow phantom experiments, the preset and measured flow rates were consistent with the coefficient of determination as 0.97. Linear fitting between preset and measured flow rates determined the fitting slope as 1.07 and the intercept as −0.28. In in vivo rat experiments, the measured average total retinal blood flow was 7.02 ± 0.31μl/min among four wild-type rats. The authors’ measured flow rates were consistent with results in the literature. Conclusions: By using a dual-ring scanning protocol with carefully controlled incident angle difference between the two scanning rings in Doppler OCT, the authors demonstrated that it is feasible to measure the absolute retinal blood flow without knowing the eyeball axial length.

  17. Path-length distribution and path-length-resolved Doppler measurements of multiply scattered photons by use of low-coherence interferometry.

    Science.gov (United States)

    Petoukhova, A L; Steenbergen, W; de Mul, F F

    2001-10-01

    We report first results of measurements by low-coherence Doppler interferometry of the path-length distribution of photons undergoing multiple scattering in a highly turbid medium. We use a Mach-Zehnder interferometer with multimode graded-index fibers and a superluminescent diode as the light source. The path-length distribution is obtained by recording of the heterodyne fluctuations that arise from the Brownian motion of particles in an Intralipid suspension as a function of the optical path length. The experimental path-length distribution is in good agreement with predictions of Monte Carlo simulations. In the heterodyne spectrum, an increase of the mean Doppler frequency with path length is observed.

  18. Measurement of contact angles of microscopic droplets by focal length method

    Science.gov (United States)

    Geiger, Daniel; Geiger, Kirsten; Neckernuss, Tobias; Marti, Othmar; Amirkhani, Masoud

    2017-08-01

    We present a method to measure contact angles of microscopic droplets with a conventional microscope that possesses a precision focus adjustment stage. The droplets are modeled as spherical caps that act as lenses. Their focal length is determined by measuring the distance from the substrate surface to the level where a sharp image of the aperture stop is observed. The lens diameter is found by edge detection of a microscope image of the microdroplets. The spherical cap model relates the focal length and diameter of such lenses to the contact angle of the used liquid with known refractive index. The measurement procedure was applied to condensed water droplets on a silicon substrate covered by its native oxide layer. The results are found to be in good agreement with conventional, goniometric sessile drop measurements of the advancing contact angle.

  19. Scale and construal: how larger measurement units shrink length estimates and expand mental horizons.

    Science.gov (United States)

    Maglio, Sam J; Trope, Yaacov

    2011-02-01

    Scale can vary by requiring a different number of units to measure the same target. But what are the consequences of using fewer, larger units? We draw on past psychophysical research that shows how using fewer units reduces clutter in measurement, translating to shorter length estimates. Additionally, we propose that larger scale is associated with targets further from a person's immediate experience (i.e., psychologically distant) and higher order mental representation. Evidence from Study 1 indicates that framing a target as further away causes it to be estimated as shorter because people use larger units to measure it compared to when the same target is framed as nearby. Two subsequent studies suggest that direct manipulation of larger (versus smaller) measurement scale produces not only shorter length estimates, but also more distal timing judgments (Study 2) and abstract mental representation (Study 3). Implications for scale and level of mental construal are discussed.

  20. Bilateral step length estimation using a single inertial measurement unit attached to the pelvis.

    Science.gov (United States)

    Köse, Alper; Cereatti, Andrea; Della Croce, Ugo

    2012-02-08

    The estimation of the spatio-temporal gait parameters is of primary importance in both physical activity monitoring and clinical contexts. A method for estimating step length bilaterally, during level walking, using a single inertial measurement unit (IMU) attached to the pelvis is proposed. In contrast to previous studies, based either on a simplified representation of the human gait mechanics or on a general linear regressive model, the proposed method estimates the step length directly from the integration of the acceleration along the direction of progression. The IMU was placed at pelvis level fixed to the subject's belt on the right side. The method was validated using measurements from a stereo-photogrammetric system as a gold standard on nine subjects walking ten laps along a closed loop track of about 25 m, varying their speed. For each loop, only the IMU data recorded in a 4 m long portion of the track included in the calibrated volume of the SP system, were used for the analysis. The method takes advantage of the cyclic nature of gait and it requires an accurate determination of the foot contact instances. A combination of a Kalman filter and of an optimally filtered direct and reverse integration applied to the IMU signals formed a single novel method (Kalman and Optimally filtered Step length Estimation - KOSE method). A correction of the IMU displacement due to the pelvic rotation occurring in gait was implemented to estimate the step length and the traversed distance. The step length was estimated for all subjects with less than 3% error. Traversed distance was assessed with less than 2% error. The proposed method provided estimates of step length and traversed distance more accurate than any other method applied to measurements obtained from a single IMU that can be found in the literature. In healthy subjects, it is reasonable to expect that, errors in traversed distance estimation during daily monitoring activity would be of the same order of

  1. Operational experience with nanocoulomb bunch charges in the Cornell photoinjector

    Directory of Open Access Journals (Sweden)

    Adam Bartnik

    2015-08-01

    Full Text Available Characterization of 9–9.5 MeV electron beams produced in the dc-gun based Cornell photoinjector is given for bunch charges ranging from 20 pC to 2 nC. Comparison of the measured emittances and longitudinal current profiles to optimized 3D space charge simulations yields excellent agreement for bunch charges up to 1 nC when the measured laser distribution is used to generate initial particle distributions in simulation. Analysis of the scaling of the measured emittance with bunch charge shows that the emittance scales roughly as the square root of the bunch charge up to 300 pC, above which the trend becomes linear. These measurements demonstrate that the Cornell photoinjector can produce cathode emittance dominated beams meeting the emittance and peak current specifications for next generation free electron lasers operating at high repetition rate. In addition, the 1 and 2 nC results are relevant to the electron ion collider community.

  2. Measuring the attenuation length of water in the CHIPS-M water Cherenkov detector

    Energy Technology Data Exchange (ETDEWEB)

    Amat, F.; Bizouard, P. [Aix Marseille University Saint-Jerome, 13013 Marseille (France); Bryant, J. [Department of Physics and Astronomy, UCL, Gower St, London WC1E 6BT (United Kingdom); Carroll, T.J.; Rijck, S. De [Department of Physics, University of Texas at Austin, Austin, TX 78712 (United States); Germani, S. [Department of Physics and Astronomy, UCL, Gower St, London WC1E 6BT (United Kingdom); Joyce, T. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Kriesten, B. [Department of Physics, College of William & Mary, Williamsburg, VA 23187 (United States); Marshak, M.; Meier, J. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Nelson, J.K. [Department of Physics, College of William & Mary, Williamsburg, VA 23187 (United States); Perch, A.J.; Pfützner, M.M. [Department of Physics and Astronomy, UCL, Gower St, London WC1E 6BT (United Kingdom); Salazar, R. [Department of Physics, University of Texas at Austin, Austin, TX 78712 (United States); Thomas, J., E-mail: jennifer.thomas@ucl.ac.uk [Department of Physics and Astronomy, UCL, Gower St, London WC1E 6BT (United Kingdom); Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Trokan-Tenorio, J. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Vahle, P. [Department of Physics, College of William & Mary, Williamsburg, VA 23187 (United States); Wade, R. [Avenir Consulting, Abingdon, Oxfordshire (United Kingdom); Wendt, C. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Whitehead, L.H. [Department of Physics and Astronomy, UCL, Gower St, London WC1E 6BT (United Kingdom); and others

    2017-02-01

    The water at the proposed site of the CHIPS water Cherenkov detector has been studied to measure its attenuation length for Cherenkov light as a function of filtering time. A scaled model of the CHIPS detector filled with water from the Wentworth 2W pit, proposed site of the CHIPS deployment, in conjunction with a 3.2 m vertical column filled with this water, was used to study the transmission of 405 nm laser light. Results consistent with attenuation lengths of up to 100 m were observed for this wavelength with filtration and UV sterilization alone.

  3. A hybrid approach for generating ultra-short bunches for advanced accelerator applications

    Energy Technology Data Exchange (ETDEWEB)

    Stratakis, Diktys [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-09-01

    Generation of electron beams with high phase-space density, short bunch length and high peak current is an essential requirement for future linear colliders and bright electron beam sources. Unfortunately, such bunches cannot be produced directly from the source since forces from the mutual repulsion of electrons would destroy the brilliance of the beam within a short distance. Here, we detail a beam dynamics study of an innovative two-stage compression scheme that can generate ultra-short bunches without degrading the beam quality. In the first stage, the beam is compressed with an advanced velocity bunching technique in which the longitudinal phase space is rotated so that electrons on the bunch tail become faster than electrons in the bunch head. In the second stage, the beam is further compressed with a conventional magnetic chicane. With the aid of numerical simulations we show that our two-staged scheme is capable to increase the current of a 50 pC bunch to a notable factor of 100 while the emittance growth can be suppressed to 1% with appropriate tailoring of the initial beam distribution.

  4. Modeling two-stage bunch compression with wakefields: Macroscopic properties and microbunching instability

    Directory of Open Access Journals (Sweden)

    R. A. Bosch

    2008-09-01

    Full Text Available In a two-stage compression and acceleration system, where each stage compresses a chirped bunch in a magnetic chicane, wakefields affect high-current bunches. The longitudinal wakes affect the macroscopic energy and current profiles of the compressed bunch and cause microbunching at short wavelengths. For macroscopic wavelengths, impedance formulas and tracking simulations show that the wakefields can be dominated by the resistive impedance of coherent edge radiation. For this case, we calculate the minimum initial bunch length that can be compressed without producing an upright tail in phase space and associated current spike. Formulas are also obtained for the jitter in the bunch arrival time downstream of the compressors that results from the bunch-to-bunch variation of current, energy, and chirp. Microbunching may occur at short wavelengths where the longitudinal space-charge wakes dominate or at longer wavelengths dominated by edge radiation. We model this range of wavelengths with frequency-dependent impedance before and after each stage of compression. The growth of current and energy modulations is described by analytic gain formulas that agree with simulations.

  5. Analytical bunch compression studies for a linac-based electron accelerator

    Directory of Open Access Journals (Sweden)

    M. Schreck

    2015-10-01

    Full Text Available The current paper deals with analytical bunch compression studies for FLUTE whose results are compared to simulations. FLUTE is a linac-based electron accelerator with a design energy of approximately 40 MeV currently being constructed at the Karlsruhe Institute of Technology. One of the goals of FLUTE is to generate electron bunches with their length lying in the femtosecond regime. In the first phase this will be accomplished using a magnetic bunch compressor. This compressor forms the subject of the studies presented. The paper is divided into two parts. The first part deals with pure geometric investigations of the bunch compressor where space charge effects and the backreaction of bunches with coherent synchrotron radiation are neglected. The second part is dedicated to the treatment of space charge effects. The upshot is that the analytical results in the two parts agree quite well with what is obtained from simulations. This paper shall form the basis for future analytical studies of the FLUTE bunch compressor and of bunch compression, in general.

  6. Photon path length distributions for cloudy skies – oxygen A-Band measurements and model calculations

    Directory of Open Access Journals (Sweden)

    O. Funk

    2003-03-01

    Full Text Available This paper addresses the statistics underlying cloudy sky radiative transfer (RT by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999. Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies are based largely on the accuracy of the measurement of the photon path length distribution (PPD. This paper presents a refined analysis method based on high resolution spectroscopy of the oxygen A-band. The method is validated by Monte Carlo simulation atmospheric spectra. Additionally, a new method to measure the effective optical thickness of cloud layers, based on fitting the measured differential transmissions with a 1-dimensional (discrete ordinate RT model, is presented. These methods are applied to measurements conducted during the cloud radar inter-comparison campaign CLARE’98, which supplied detailed cloud structure information, required for the further analysis. For some exemplary cases, measured path length distributions and optical thicknesses are presented and backed by detailed RT model calculations. For all cases, reasonable PPDs can be retrieved and the effects of the vertical cloud structure are found. The inferred cloud optical thicknesses are in agreement with liquid water path measurements. Key words. Meteorology and atmospheric dynamics (radiative processes; instruments and techniques

  7. Photon path length distributions for cloudy skies – oxygen A-Band measurements and model calculations

    Directory of Open Access Journals (Sweden)

    O. Funk

    Full Text Available This paper addresses the statistics underlying cloudy sky radiative transfer (RT by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999. Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies are based largely on the accuracy of the measurement of the photon path length distribution (PPD. This paper presents a refined analysis method based on high resolution spectroscopy of the oxygen A-band. The method is validated by Monte Carlo simulation atmospheric spectra. Additionally, a new method to measure the effective optical thickness of cloud layers, based on fitting the measured differential transmissions with a 1-dimensional (discrete ordinate RT model, is presented. These methods are applied to measurements conducted during the cloud radar inter-comparison campaign CLARE’98, which supplied detailed cloud structure information, required for the further analysis. For some exemplary cases, measured path length distributions and optical thicknesses are presented and backed by detailed RT model calculations. For all cases, reasonable PPDs can be retrieved and the effects of the vertical cloud structure are found. The inferred cloud optical thicknesses are in agreement with liquid water path measurements.

    Key words. Meteorology and atmospheric dynamics (radiative processes; instruments and techniques

  8. MEASUREMENT OF ROOT LENGTH DENSITY IN INTACT SAMPLES USING X-RADIOGRAPHY AND IMAGE ANALYSIS

    Directory of Open Access Journals (Sweden)

    Alain Pierret

    2011-05-01

    Full Text Available Measurement of root system attributes is of critical importance to understand and model plant growth. Root length density, the length of roots per unit volume of soil, is one of the important parameters required to understand plant performance. Measuring techniques currently in use to assess this parameter, such as for example core washing, are notoriously imprecise and labour-intensive. Roots and soil being inextricably linked, it is virtually impossible to separate them without loosing a significant amount of the root sample to be measured. This noticeably compromises the accuracy of washing techniques. For this reason, non-invasive measurement approaches are highly desirable. Here, a method based on the combination of X-radiography and image analysis is proposed as a new alternative for the measurement of root length density from intact samples. The successive steps of the method, from sampling to image acquisition are briefly described. A specific measurement algorithm, designed to account for the complex spatial arrangement of the roots within the samples is then presented and discussed in detail.

  9. [Stature estimation from length of tibias and fibulas measured in computed radiography of living body].

    Science.gov (United States)

    Fan, Tao; Chen, Xiao-Gang; Zhou, Xiao-Rong; Zhang, Zhao-Hui; Deng, Zhen-Hua; Wang, Hui-Xiang

    2008-04-01

    By measuring lengths of tibias and fibulas in computed radiography (CR) of living body, regression formulae for stature estimation were obtained from these measurements that were adapted to the population of northern adults of Han. The length of tibias and fibulas were measured in radiography, including 422 subjects (207 men and 215 women). The body height of each subject was also recorded. Linear regression analysis between body height and the length of tibias and fibulas , analysis of variance of hypothesis test of linear regression model and t-test of the partial regression coefficient were applied to establish the regression equations for stature estimation. Then the paired t-test between the predictive value and the actual body height, the residual analysis, the tests of equal scedasticity and colinearity had been done to evaluate whether the equations accord with the model. Thirty five regression equations which were statistical significant were obtained. The multiple correlation coefficient was from 0.909 to 0.823 and the standard error of the estimation was between 2.48-3.87 cm. The lengths of tibias and fibulas on the CR films could be helpful to estimate stature. These equations could be used to estimate the body height of the Han population in North China.

  10. A multi-channel THz and infrared spectrometer for femtosecond electron bunch diagnostics by single-shot spectroscopy of coherent radiation

    Energy Technology Data Exchange (ETDEWEB)

    Wesch, Stephan; Schmidt, Bernhard; Behrens, Christopher; Delsim-Hashemi, Hossein; Schmueser, Peter

    2011-08-15

    The high peak current required in free-electron lasers (FELs) is realized by longitudinal compression of the electron bunches to sub-picosecond length. In this paper, a frequency-domain diagnostic method is described that is capable of resolving structures in the femtosecond regime. A novel in-vacuum spectrometer has been developed for spectroscopy of coherent radiation in the THz and infrared range. The spectrometer is equipped with five consecutive dispersion gratings and 120 parallel readout channels; it can be operated either in short wavelength mode (5-44 {mu}m) or in long wavelength mode (45-430 {mu}m). Fast parallel readout permits the spectroscopy of coherent radiation from single electron bunches. Test measurements at the soft X-ray free-electron laser FLASH, using coherent transition radiation, demonstrate excellent performance of the spectrometer. The high sensitivity down to a few micrometers allows study of short bunch features caused for example by microbunching e ects in magnetic chicanes. The device is planned for use as an online bunch profile monitor during regular FEL operation. (orig.)

  11. The analysis of bunch production in the oil palm

    NARCIS (Netherlands)

    Sparnaaij, L.D.

    1959-01-01

    Bunch yield of oil palms can be expressed as the product of number of bunches and average bunch weight. Number of bunches is itself composite, being determined by number of leaves, percentage floral abortion, sex ratio and percentage bunch failure. Of these elements sex ratio proved to be most

  12. Investigations of Longitudinal Charge Distribution in Very Short Electron-Bunches

    CERN Document Server

    Hüning, M

    2001-01-01

    Electro-optical-sampling is a powerful technique to measure the longitudinal charge distribution of very short electron bunches. The electrical field moving with the bunch induces an optical an-isotropy in a ZnTe crystal which is probed by a polarized laser pulse. Two measurement principles are possible. In the first one a short laser pulse of lengths <50 fs is used directly to scan the time varying optical properties of the crystal. In the second method the laser pulse is frequency chirped and the temporal information is encoded into the time ordered frequency spectrum, which can be recovered by an optical grating and a CCD camera. A resolution in the 100 fs regime can also be achieved with longitudinal phase space tomography. Acceleration on the slope of the rf wave at different phases and measurements of the energy profiles are sufficient for a reconstruction algorithm based on maximum entropy methods. The longitudinal phase space distribution can be obtained without artifacts due to the limited angular...

  13. Transverse coupled-bunch instabilities for non-symmetric bunch fillings

    CERN Document Server

    Meincke, O

    1998-01-01

    A program has been written in order to investigate transverse coupled-bunch instabilities for non-symmetric bunch fillings in the case of a large number of bunches. After a short description of the method used to find the instability growth rates, first results of the program are discussed for the SPS and LHC. In particular, a systematic study of the effect of fluctuations in the bunch populations is presented.

  14. Stature estimation in Japanese cadavers using the sacral and coccygeal length measured with multidetector computed tomography.

    Science.gov (United States)

    Torimitsu, Suguru; Makino, Yohsuke; Saitoh, Hisako; Ishii, Namiko; Hayakawa, Mutsumi; Yajima, Daisuke; Inokuchi, Go; Motomura, Ayumi; Chiba, Fumiko; Iwase, Hirotaro

    2014-01-01

    We evaluated the relationship between stature and the length of the sacrum and coccyx using multidetector computed tomography (MDCT) and derived regression equations for stature estimation in the modern Japanese population. Two hundred and sixteen Japanese subjects (110 males and 106 females) who underwent postmortem computed tomography with subsequent forensic autopsy between January 2010 and August 2013 were measured. A sagittal-plane image of the sacrum and coccyx was used. Anterior sacral length (ASL) was defined as the linear distance from the anterosuperior edge of the first sacral vertebra (S1) to the anteroinferior edge of the fifth sacral vertebra (S5), and posterior sacral length (PSL) was defined as the linear distance from the posterosuperior edge of S1 to the anteroinferior edge of S5. Anterior sacrococcygeal length (ASCL) was defined as the linear distance from the anterosuperior edge of S1 to the anteroinferior edge of the last coccygeal vertebra (LCV), and posterior sacrococcygeal length (PSCL) was defined as the linear distance from the posterosuperior edge of S1 to the anteroinferior edge of the LCV. The correlation between stature and each parameter was evaluated by simple regression analysis using Pearson product-moment correlation coefficients. Each parameter was significantly and positively correlated with stature among both males and females. Cadaver stature (CS, cm)=0.39×PSL (mm)+123.70 [Corrected] provided the most accurate stature prediction (R=0.507, SEE=5.83 cm) in males. CS (cm)=0.56×PSCL (mm)+85.29 provided the most accurate stature prediction (R=0.659, SEE=6.68 cm) in females. We conclude that sacral/sacrococcygeal length measured with MDCT is a potentially useful tool for stature estimation, particularly in cases where better predictors such as the long bones are not available. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  15. Cervical Length & Leading Placental Edge to Internal OS Measurements - TA vs TV

    DEFF Research Database (Denmark)

    Westerway, Sue Campbell; Pedersen, Lars Henning; Hyett, Jon

    Brief Description of the Purpose of the Study: To compare cervical length/leading placental edge from the internal cervical os measurements obtained by both transabdominal (TA) and transvaginal (TV) approach and to assess intra / inter-observer variation for these measurements. Methods: Cross...... sectional study of 374 consecutive pregnancies with gestation 12 weeks to term. The cervical length was estimated as the distance from internal to external os, and the placenta / cervix distance as the leading placental edge to internal cervical os. Bland-Altman plots were used to evaluate the two methods....... Importance of the Conclusions: TA estimates of cervix and placental edge position did not reflect the estimates obtained by TV assessment. As both measures are important markers of pregnancy outcome and management, the transabdominal method in the present form is insuffi- cient in clinical management....

  16. Electro-optic methods for longitudinal bunch diagnostics at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Steffen, B.R.

    2007-07-15

    Precise measurements of the temporal profile of sub-picosecond electron bunches are of high interest for the optimization and operation of VUV and X-ray free electron lasers. In this thesis, the shortest electro-optic signals measured so far for electron bunch diagnostics are presented, reaching a time resolution of better than 50 fs (rms). The e ects that introduce signal distortions and limit the time resolution are studied in numerical simulations for different electro-optic detection materials and techniques. The time resolution is mainly limited by lattice resonances of the electro-optic crystal. Electro-optic signals as short as 54 fs (rms) are obtained with gallium phosphide (GaP) crystals in a crossed polarizer detection scheme using temporally resolved electro-optic detection. Measuring near crossed polarization, where the electro-optic signal is proportional to the velocity field of the relativistic electron bunch, the shortest obtained signal width is 70 fs (rms). The electro-optic signals are compared to electron bunch shapes that are measured simultaneously with a transverse deflecting structure with 20 fs resolution. Numerical simulations using the bunch shapes as determined with the transverse deflecting cavity as input data are in excellent agreement with electro-optical signals obtained with GaP, both for temporally and spectrally resolved measurements. In the case of zinc telluride (ZnTe) the observed signals are slightly broader and significantly smaller than expected from simulations. These discrepancies are probably due to the poor optical quality of the available ZnTe crystals. (orig.)

  17. Estimation of Maximum Tibia Length from its Measured Anthropometric Parameters in a Nigerian Population

    Directory of Open Access Journals (Sweden)

    Esomonu Godfrey Ugochukwu

    2016-01-01

    Full Text Available Reliable estimation of stature from skeletal remains will continue to play an important role in assessing a variety of forensic anthropological and archaeological issues. In the present study, we studied and collated data on the morphometry of the tibia as well as analyzing its segment that shows significant correlation with its maximum length and consequently formulating linear regression equations for estimating maximum tibia length (MTL which is specific for the Nigeria population. A total number of 68 intact adult human tibia bones were used (35 right and 33 left. Thirteen anthropometric parameters were measured including the MTL. The mean differences between right and left bones of all the measured parameter were not statistically significant except for the mean shaft circumference. The correlation coefficient between MTL and the bicondylar tibial width (BTW, anterior-posterior intercondylar diameter (APID, anterior-posterior diameter of medial condyle (APDMC, midshaft transverse diameter (MSTD, and distal articular surface length (DASL were seen to be significant (P < 0.05 only in the right tibia; therefore, the linear regression equations for estimation of MTL from these parameters for the right tibia were also significant (P < 0.05. The results of our study concluded that it is possible to estimate the maximum length of the right tibia from the BTW, APID, APDMC, MSTD, and DASL with relative accuracy. Our study may be useful for forensic investigations for the identification of the remains of unknown bodies in a Nigerian population.

  18. Precision measurement of the n-4He scattering length using neutron interferometry

    Science.gov (United States)

    Huber, M. G.; Arif, M.; Jacobson, D. L.; Pushin, D. A.; Abutaleb, M. O.; Black, T. C.; Shahi, C. B.; Wietfeldt, F. E.

    2010-11-01

    The NIST neutron interferometer and optics facility (NIOF) is currently performing a precision measurement of the n-4He scattering length to less than 0.3% relative uncertainty. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons entering the interferometer are Bragg diffracted in the blades to produce two spatially separate yet coherent beam paths much like an optical Mach-Zehnder interferometer. A sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths. This phase difference is directly related to the sample's scattering length. Neutron scattering lengths are one parameter that can be predicted using advanced theoretical models describing two and three nucleon interactions. In an effort to provide tests and/or benchmarks of these theoretical models, the NIOF has already performed precision measurements of neutron scattering lengths to less than 1% relative uncertainty in several low Z gases: H, D, 3He, and polarized 3He. A preliminary result of this work will be given.

  19. Generation of attosecond electron bunches in a laser-plasma accelerator using a plasma density upramp

    Energy Technology Data Exchange (ETDEWEB)

    Weikum, M.K., E-mail: maria.weikum@desy.de [Deutsches Elektronensynchrotron (DESY), Bdg. 30b, Notkestr. 85, 22607 Hamburg (Germany); Department of Physics, University of Strathclyde, G4 0NG Glasgow (United Kingdom); Li, F.Y. [Department of Physics, University of Strathclyde, G4 0NG Glasgow (United Kingdom); Assmann, R.W. [Deutsches Elektronensynchrotron (DESY), Bdg. 30b, Notkestr. 85, 22607 Hamburg (Germany); Sheng, Z.M. [Department of Physics, University of Strathclyde, G4 0NG Glasgow (United Kingdom); Laboratory for Laser Plasmas and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Jaroszynski, D. [Department of Physics, University of Strathclyde, G4 0NG Glasgow (United Kingdom)

    2016-09-01

    Attosecond electron bunches and attosecond radiation pulses enable the study of ultrafast dynamics of matter in an unprecedented regime. In this paper, the suitability for the experimental realization of a novel scheme producing sub-femtosecond duration electron bunches from laser-wakefield acceleration in plasma with self-injection in a plasma upramp profile has been investigated. While it has previously been predicted that this requires laser power above a few hundred terawatts typically, here we show that the scheme can be extended with reduced driving laser powers down to tens of terawatts, generating accelerated electron pulses with minimum length of around 166 attoseconds and picocoulombs charge. Using particle-in-cell simulations and theoretical models, the evolution of the accelerated electron bunch within the plasma as well as simple scalings of the bunch properties with initial laser and plasma parameters are presented. - Highlights: • LWFA with an upramp density profile can trap and accelerate sub-fs electron beams. • A reduction of the necessary threshold laser intensity by a factor 4 is presented. • Electron properties are tuned by varying initial laser and plasma parameters. • Simulations predict electron bunch lengths below 200 attoseconds with pC charge. • Strong bunch evolution effects and a large energy spread still need to be improved.

  20. Effect of e-learning on quality of cervical-length measurements.

    Science.gov (United States)

    van Os, M A; van der Ven, A J; Bloemendaal, P M; Pajkrt, E; de Groot, C J M; Mol, B W J; Haak, M C

    2015-09-01

    To assess the effect of implementation of a newly developed e-learning module on the quality of cervical-length measurements. With the introduction of cervical-length (CL) measurement in a research setting, a CL measurement e-learning module (CLEM) was developed with the purpose to enhance the knowledge and skills of experienced ultrasonographers. CLEM was designed specifically for ultrasonographers who perform ultrasound in a general obstetrical practice but who do not regularly perform CL measurements. CLEM consists of five theoretical questions and three caliper-placement tests to learn the CL measurement technique. The quality of the CL measurements of CLEM participants was compared with images of non-participants using a CL measurement image score (CIS), defined as the sum of six items which assess the quality of the image. Each CLEM participant submitted five CL images and the images of non-CLEM participants were selected randomly from an ultrasound database. The CIS of the CLEM participants (n = 61) were significantly higher than those of non-CLEM participants (n = 23) (164.9 vs 155.6, respectively; P = 0.03). Visualization of the internal os and positioning of the calipers on the internal and external ora were found to have significantly higher CIS among the CLEM participants than among the non-CLEM participants (P = 0.001 and P quality of CL measurements obtained by trained and untrained sonographers. Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.

  1. Analysis of impedance measurements of a suspension of microcapsules using a variable length impedance measurement cell

    Directory of Open Access Journals (Sweden)

    Dejan Krizaj

    2012-10-01

    Full Text Available Electrical impedance measurements of the suspensions have to take into account the double layer impedance that is due to a very thin charged layer formed at the electrode-electrolite interface. A dedicated measuring cell that enables variation of the distance between the electrodes was developed for investigation of electrical properties of suspensions using two electrode impedance measurements. By varying the distance between the electrodes it is possible to separate the double layer and the suspension impedance from the measured data. From measured and extracted impedances electrical lumped models have been developed. The error of non inclusion of the double layer impedance has been analyzed. The error depends on the frequency of the measurements as well as on the distance between the electrodes.

  2. Influence of proton bunch and plasma parameters on the AWAKE experiment

    Science.gov (United States)

    Moreira, Mariana; Vieira, Jorge; Muggli, Patric

    2017-10-01

    The Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) at CERN will test the concept underlying plasma wakefield acceleration using long proton beams that undergo the self-modulation instability. The effectiveness of the experiment hinges on the successful and predictable development of this instability, which fragments the initial proton bunch into smaller beamlets with lengths of the order of the plasma wavelength. Since the initial parameters of the experiment inevitably vary from event to event, this work will aim to understand the correlation between these variations and the resulting wakefield. Using both theoretical models and numerical particle-in-cell simulations, the influence of variations in initial bunch charge, bunch dimensions, bunch energy and plasma density profile on the excited accelerating gradients and on the final energies reached by the witness particles will be investigated. In addition, further options in the experiment setup will be explored with the aim of optimizing the results.

  3. High-intensity coherent FIR radiation from sub-picosecond electron bunches

    Energy Technology Data Exchange (ETDEWEB)

    Kung, P.H.; Lihn, Hung-chi; Wiedemann, H.; Bocek, D.

    1994-01-01

    A facility to generate high-intensity, ultra-short pulses of broad-band far-infrared radiation has been assembled and tested at Stanford. The device uses sub-picosecond relativistic electron bunches to generate coherent radiation through transition or synchrotron radiation in the far-infrared (FIR) regime between millimeter waves and wavelengths of about 100 {mu}m and less. Experimental results show a peak radiation power of greater than 0.33 MW within a micro-bunch and an average FIR radiation power of 4 mW. The average bunch length of 2856 micro-bunches within a 1 {mu}sec macro-pulse is estimated to be about 480 sec. Simulations experimental setup and results will be discussed.

  4. Measurement of optical path length change following pulsed laser irradiation using differential phase optical coherence tomography.

    Science.gov (United States)

    Kim, Jihoon; Oh, Junghwan; Milner, Thomas E

    2006-01-01

    Differential phase optical coherence tomography (DPOCT) is introduced to measure optical path length changes in response to pulsed laser irradiation (585 nm). An analytical equation that includes thermoelastic surface displacement and thermorefractive index change is derived to predict optical path length change in response to pulsed laser irradiation for both "confined surface" and "free surface" model systems. The derived equation is tested by comparing predicted values with data recorded from experiments using two model systems. Thermorefractive index change and the thermal expansion coefficient are deduced from differential phase change (dDeltaphi) and temperature increase (DeltaT0) measurements. The measured n(T0)beta(T0)+dndT[=1.7410(-4)+/-1.710(-6) (1K)] in the free surface experiment matches with the National Institute of Standards and Technology (NIST) data value [=1.7710(-4) (1K)]. Exclusion of lateral thermal expansion in the analytical model for the confined surface experiment causes difference between the measured dndT[=-2.310(-4)+/-7.310(-6)(1K)] and the NIST value [=-9.4510(-5) (1K)]. In spite of the difference in the confined surface experiment, results of our studies indicate DPOCT can detect dynamic optical path length change in response to pulsed laser irradiation with high sensitivity, and applications to tissue diagnostics may be possible.

  5. Continuous measurement of optical surfaces using a line-scan interferometer with sinusoidal path length modulation.

    Science.gov (United States)

    Knell, Holger; Laubach, Sören; Ehret, Gerd; Lehmann, Peter

    2014-12-01

    We present a fast approach to the continuous measurement of rotational symmetric optical surfaces. This approach is based on a line scanning interferometer with sinusoidal modulation of the optical path length. The specimen is positioned with respect to the sensor and both are moved during measurement by use of a five axes system comprising a high precision rotational table. The calibration of both the line sensor as well as the scanning and positioning system is discussed. As proof of principle of the measurement and stitching concept results of a scan of a rotational symmetric sinusoidal structure and a spherical lens with a moderate slope are shown.

  6. Preparation and measurement of FBG-based length, temperature, and vibration sensors

    Science.gov (United States)

    Mikel, Bretislav; Helan, Radek; Buchta, Zdenek; Jelinek, Michal; Cip, Ondrej

    2016-12-01

    We present system of structure health measurement by optical fiber sensors based on fiber Bragg gratings. Our system is focused to additionally install to existing buildings. We prepared first set-up of the system to monitoring of the nuclear power plant containment shape deformation. The presented system can measure up to several tens of sensors simultaneously. Each sensor contains optical fiber grating to measurement of change of length and the other independed fiber grating to monitor the temperature and the other ineligible effects.

  7. Precision Measurement of the n-3He Incoherent Scattering Length Using Neutron Interferometry

    CERN Document Server

    Huber, M G; Black, T C; Chen, W C; Gentile, T R; Hussey, D S; Pushin, D; Wietfeldt, F E; Yang, L

    2008-01-01

    We report the first measurement of the low-energy neutron-3He incoherent scattering length using neutron interferometry: b_i' = (-2.417 +/- 0.012 statistical +/- 0.014 systematic) fm. It is in slight disagreement with the only previous measurement of this quantity by Zimmer, et al., b_i' = (-2.365 +/- 0.020) fm, which used a very different technique, pseudomagnetic spin rotation. The neutron-3He scattering lengths are important for testing and developing nuclear potential models that include three nucleon forces, effective field theories for few-body nuclear systems, and for understanding quantum excitations in liquid helium. This work demonstrates the first use of a polarized nuclear target in a neutron interferometer.

  8. The accuracy of the radiographic method in root canal length measurement

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Eun Young; Park, Chang Seo [Dept. of Dental Radiology, College of Dentistry, Yonsei University, Seoul (Korea, Republic of)

    1998-08-15

    For the successful endodontic treatment, root canal should be cleaned thoroughly by accurate mechanical and chemical canal preparation and sealed completely with canal filling material without damaging the periapical tissues. The accuracy of the root canal length measurement is a prerequisite for the success of the endodontic treatment, and the root canal length is often determined by the standard periapical radiographs and digital tactile sense. In this study, the accuracy and the clinical usefulness of Digora, an intraoral digital imaging processor and the conventional standard radiographs were compared by measuring the length from the top of the file to the root apex. 30 single rooted premolars were invested in a uniformly sized blocks and No.25 K-file was inserted into and fixed in each canal. Each block was placed in equal distance and position to satisfy the principle of the bisecting angle and paralleling techniques and Digora system's image and standard periapical radiographs were taken. Each radiograph was examined by 3 different observers by measuring the length from top of the file to the root apex and each data was compared and analyzed. The results were as follows; 1. In the bisecting angle technique, the average difference between the Digora system and standard periapical radiograph was 0.002 mm and the standard deviation was 0.341 mm which showed no statistically significant difference between the two systems (p>0.05). Also, in the paralleling technique, the average difference between these two system was 0.007 mm and the standard deviation was 0.323 mm which showed no statistically significant difference between the two systems (p>0.05). 2. In Digora system, the average difference between the bisecting angle and paralleling technique was -0.336 mm and the standard deviation was 0.472 mm which showed a statistically significant difference between the two techniques (p<0.05). Also, 3. In Digora system and the standard periapical radiographs

  9. Bilateral step length estimation using a single inertial measurement unit attached to the pelvis

    Science.gov (United States)

    2012-01-01

    Background The estimation of the spatio-temporal gait parameters is of primary importance in both physical activity monitoring and clinical contexts. A method for estimating step length bilaterally, during level walking, using a single inertial measurement unit (IMU) attached to the pelvis is proposed. In contrast to previous studies, based either on a simplified representation of the human gait mechanics or on a general linear regressive model, the proposed method estimates the step length directly from the integration of the acceleration along the direction of progression. Methods The IMU was placed at pelvis level fixed to the subject's belt on the right side. The method was validated using measurements from a stereo-photogrammetric system as a gold standard on nine subjects walking ten laps along a closed loop track of about 25 m, varying their speed. For each loop, only the IMU data recorded in a 4 m long portion of the track included in the calibrated volume of the SP system, were used for the analysis. The method takes advantage of the cyclic nature of gait and it requires an accurate determination of the foot contact instances. A combination of a Kalman filter and of an optimally filtered direct and reverse integration applied to the IMU signals formed a single novel method (Kalman and Optimally filtered Step length Estimation - KOSE method). A correction of the IMU displacement due to the pelvic rotation occurring in gait was implemented to estimate the step length and the traversed distance. Results The step length was estimated for all subjects with less than 3% error. Traversed distance was assessed with less than 2% error. Conclusions The proposed method provided estimates of step length and traversed distance more accurate than any other method applied to measurements obtained from a single IMU that can be found in the literature. In healthy subjects, it is reasonable to expect that, errors in traversed distance estimation during daily monitoring

  10. A first analysis of 3-bunches and 1-bunch scenario for the SPL based Proton Driver

    CERN Document Server

    Aiba, M

    2008-01-01

    The SPL based proton driver for a future neutrino factory has been proposed and studied. The use of the SPL proton driver requires an accumulator and an compressor for forming the output time structure required for the neutrino factory. While the number of bunches per burst could be varied in a range of 1-6, it is preferred to be as small as possible for the muon accelerators and storage ring. Thus a scenario of fewer number of bunches is discussed in this note based on the results from the study of 6-bunches scenario. The new scenario enables to have two operation modes, 3-bunches and 1-bunch, using the same accumulator and compressor. Although not everything is covered in this first analysis, the 3-bunches and 1-bunch scenario seems achievable.

  11. Coherent-Radiation Spectroscopy of Few-Femtosecond Electron Bunches Using a Middle-Infrared Prism Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, T. J.; Behrens, C.; Ding, Y.; Fisher, A. S.; Frisch, J.; Huang, Z.; Loos, H.

    2013-10-28

    Modern, high-brightness electron beams such as those from plasma wakefield accelerators and free-electron laser linacs continue the drive to ever-shorter bunch durations. In low-charge operation ( ~ 20 pC ), bunches shorter than 10 fs are reported at the Linac Coherent Light Source (LCLS). Though suffering from a loss of phase information, spectral diagnostics remain appealing as compact, low-cost bunch duration monitors suitable for deployment in beam dynamics studies and operations instrumentation. Progress in middle-infrared (MIR) imaging has led to the development of a single-shot, MIR prism spectrometer to characterize the corresponding LCLS coherent beam radiation power spectrum for few-femtosecond scale bunch length monitoring. In this Letter, we report on the spectrometer installation as well as the temporal reconstruction of 3 to 60 fs-long LCLS electron bunch profiles using single-shot coherent transition radiation spectra.

  12. Transverse Acoustic Measurements of Superuid Helium-3 at Fixed and Variable Path Lengths

    Science.gov (United States)

    Collett, Charles Alward

    This thesis describes experiments using transverse zero sound in pure superfluid 3He to probe excitations with energies below the superfluid gap. One main focus is on a collective mode of the order parameter, the imaginary squashing mode. The splitting of this mode in a magnetic field causes acoustic birefringence, which rotates the polarization axis of the transverse sound wave. We have made precise measurements of this rotation in magnetic fields up to 0.11 T and observed the onset of nonlinear field dependence. Our measurements of the linear field dependence disagree with theoretical predictions, which led us to discover that the theory only applies when the sound frequency is close to the mode frequency, a condition not satisfied in our experiments. We extrapolated our data to the region of validity of the theory, and measured attractive sub-dominant f-wave pairing interactions. The other main focus is the construction of an experimental apparatus to enable in situ variation of the acoustic cavity spacing at low temperatures. Recent measurements have indicated a coupling between the transverse sound attenuation and surface Andreev bound states, which are predicted to be Majorana states in the specular scattering limit. A variable path length sample cell would enable measurements of the absolute attenuation of transverse sound, as well as allow for the separation of bulk effects from surface effects. It would also enable experiments looking for transverse zero sound in the normal state of 3He, which is predicted to have a high attenuation length requiring a micron-scale acoustic cavity. We have designed and implemented a diaphragm-based variable path length cell, and discuss our current progress and future prospects.

  13. Measurement of the axial eye length by wavelength-tuning interferometry

    Science.gov (United States)

    Lexer, Franz; Hitzenberger, Christoph K.; Kulhavy, Manfred; Fercher, Adolf F.

    1996-12-01

    An alternative approach to measure intraocular optical distances in vivo is wavelength tuning interferometry. The principle of this technique is that every wavelength shift of a laser diode is associated with a phase shift of the waves reflected at the cornea and the retina. This results in a change of the interference order of the fringe system that will occur when the two wavefronts interfere. By Fourier transform of the intensity data, we cannot only measure the axial eye length but also other intraocular distances. In our approach we used an external cavity, single mode laser diode at a center wavelength of 780 nm which is tunable over 15 nm. First measurements were carried out in a model eye using the mode hop free tuning range of 9 nm, at the maximum tuning rate of 0.33 nm/s. The precision we obtained for the axial eye length was 0.04 mm. The large tuning range cannot be used of in vivo measurements because of the slow scanning rate of 0.33 nm/s. With this scanning rate the signal frequency corresponding to the axial eye length is on the order of 30 Hz. This is within the frequency range of the intensity modulations caused by fundus pulsations due to the heart beat and can therefore not be separated from them. The in vivo measurements have to be performed by tuning the wavelength of the laser with a piezoelectric transducer to achieve signal frequencies in the kHz range. Since the tuning range in this case in only 0.18 nm the resolution is about 50 times worse than that achieved in the model eye.

  14. Reliability of length measurements collected by community nurses and health volunteers in rural growth monitoring and promotion services.

    Science.gov (United States)

    Laar, Matilda E; Marquis, Grace S; Lartey, Anna; Gray-Donald, Katherine

    2018-02-17

    Length measurements are important in growth, monitoring and promotion (GMP) for the surveillance of a child's weight-for-length and length-for-age. These two indices provide an indication of a child's risk of becoming wasted or stunted, and are more informative about a child's growth than the widely used weight-for-age index (underweight). Although the introduction of length measurements in GMP is recommended by the World Health Organization, concerns about the reliability of length measurements collected in rural outreach settings have been expressed by stakeholders. Our aim was to describe the reliability and challenges associated with community health personnel measuring length for rural outreach GMP activities. Two reliability studies (A and B), using 10 children less than 24 months each, were conducted in the GMP services of a rural district in Ghana. Fifteen nurses and 15 health volunteers (HV) with no prior experience in length measurements were trained. Intra- and inter-observer technical error of measurement (TEM), average bias from expert anthropometrist, and coefficient of reliability (R) of length measurements were assessed and compared across sessions. Observations and interviews were used to understand the ability and experiences of health personnel with measuring length at outreach GMP. Inter-observer TEM was larger than intra-observer TEM for both nurses and HV at both sessions and was unacceptably (compared to error standards) high in both groups at both time points. Average biases from expert's measurements were within acceptable limits, however, both groups tended to underestimate length measurements. The R for lengths collected by nurses (92.3%) was higher at session B compared to that of HV (87.5%). Length measurements taken by nurses and HV, and those taken by an experienced anthropometrist at GMP sessions were of moderate agreement (kappa = 0.53, p reliability of length measurements improved after two refresher trainings for nurses but

  15. Round-Trip System Available to Measure Path Length Variation in Korea VLBI System for Geodesy

    Science.gov (United States)

    Oh, Hongjong; Kondo, Tetsuro; Lee, Jinoo; Kim, Tuhwan; Kim, Myungho; Kim, Suchul; Park, Jinsik; Ju, Hyunhee

    2010-01-01

    The construction project of Korea Geodetic VLBI officially started in October 2008. The construction of all systems will be completed by the end of 2011. The project was named Korea VLBI system for Geodesy (KVG), and its main purpose is to maintain the Korea Geodetic Datum. In case of the KVG system, an observation room with an H-maser frequency standard is located in a building separated from the antenna by several tens of meters. Therefore KVG system will adopt a so-called round-trip system to transmit reference signals to the antenna with reduction of the effect of path length variations. KVG s round-trip system is designed not only to use either metal or optical fiber cables, but also to measure path length variations directly. We present this unique round trip system for KVG.

  16. Measurement of the $\\pi K$ atom lifetime and the $\\pi K$ scattering length

    CERN Document Server

    Adeva, B.; The PS212 collaboration; Allkofer, Y.; Amsler, C.; Anania, A.; Aogaki, S.; Benelli, A.; Brekhovskikh, V.; Cechak, T.; Chiba, M.; Chliapnikov, P.; Drijard, D.; Dudarev, A.; Dumitriu, D.; Federicova, P.; Fluerasu, D.; Gorin, A.; Gorchakov, O.; Gritsay, K.; Guaraldo, C.; Gugiu, M.; Hansroul, M.; Hons, Z.; Horikawa, S.; Iwashita, Y.; Karpukhin, V.; Kluson, J.; Kobayashi, M.; Kruglov, V.; Kruglova, L.; Kulikov, A.; Kulish, E.; Kuptsov, A.; Lamberto, A.; Lanaro, A.; Lednicky, R.; Marinas, C.; Martincik, J.; Nemenov, L.; Nikitin, M.; Okada, K.; Olchevskii, V.; Pentia, M.; Penzo, A.; Plo, M.; Prusa, P.; Rappazzo, G.; Romero Vidal, A.; Ryazantsev, A.; Rykalin, V.; Saborido, J.; Schacher, J.; Sidorov, A.; Smolik, J.; Takeutchi, F.; Tauscher, L.; Trojek, T.; Trusov, S.; Urban, T.; Vrba, T.; Yazkov, V.; Yoshimura, Y.; Zhabitsky, M.; Zrelov, P.

    2017-09-19

    After having announced the statistically significant observation (5.6~$\\sigma$) of the new exotic $\\pi K$ atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding atom lifetime, based on the full $\\pi K$ data sample: $\\tau = (5.5^{+5.0}_{-2.8}) \\cdot 10^{-15}s$. By means of a precise relation ($<1\\%$) between atom lifetime and scattering length, the following value for the S-wave isospin-odd $\\pi K$ scattering length $a_0^{-}~=~\\frac{1}{3}(a_{1/2}-a_{3/2})$ has been derived: $\\left|a_0^-\\right| = (0.072^{+0.031}_{-0.020}) M_{\\pi}^{-1}$.

  17. A set-up to measure the optical attenuation length of scintillating fibres

    CERN Document Server

    Alfieri, C; Joram, C

    2015-01-01

    The optical attenuation length of a scintillating fibre characterizes the quality of light transport through the fibre. It relates directly to the quantity of detectable light at the readout end of the fibre. An optical bench has been constructed, which allows excitation of the fibre at various distances from the photodetector. Depending on the choice of the photodetector – Si-PIN photodiode or grating spectrometer – the attenuation length is measured as weighted average over the sensitivity of the photodetector or as a spectral distribution. A few examples illustrate its operation and performance. The set-up serves for fibre optimisation in the R&D phase and is expected to be used for systematic checks during the series production phase of the LHCb SciFi tracker project.

  18. Path-length distribution and path-length-resolved Doppler measurements of multiply scattered photons by use of low-coherence interferometry

    NARCIS (Netherlands)

    Petoukhova, Anna; Steenbergen, Wiendelt; de Mul, F.F.M.

    2001-01-01

    We report first results of measurements by low-coherence Doppler interferometry of the path-length distribution of photons undergoing multiple scattering in a highly turbid medium. We use a Mach–Zehnder interferometer with multimode graded-index fibers and a superluminescent diode as the light

  19. Interferometer with Continuously Varying Path Length Measured in Wavelengths to the Reference Mirror

    Science.gov (United States)

    Ohara, Tetsuo (Inventor)

    2016-01-01

    An interferometer in which the path length of the reference beam, measured in wavelengths, is continuously changing in sinusoidal fashion and the interference signal created by combining the measurement beam and the reference beam is processed in real time to obtain the physical distance along the measurement beam between the measured surface and a spatial reference frame such as the beam splitter. The processing involves analyzing the Fourier series of the intensity signal at one or more optical detectors in real time and using the time-domain multi-frequency harmonic signals to extract the phase information independently at each pixel position of one or more optical detectors and converting the phase information to distance information.

  20. Nonlocal bunching of composite bosons

    Science.gov (United States)

    Lasmar, Zakarya; Kaszlikowski, Dagomir; Kurzyński, Paweł

    2017-09-01

    It was suggested that two entangled fermions can behave like a single boson and that the bosonic quality is proportional to the degree of entanglement between the two particles. The relation between bosonic quality and entanglement is quite natural if one takes into account the fact that entanglement appears in bound states of interacting systems. However, entanglement can still be present in spatially separated subsystems that no longer interact. These systems are often the subject of studies on quantum nonlocality and foundations of quantum physics. Here, we ask whether an entangled spatially separated fermionic pair can exhibit bosonic properties. We show that under certain conditions the answer to this question can be positive. In particular, we propose a nonlocal bunching scenario in which two such pairs form an analog of a two-partite bosonic Fock state.

  1. Measurement of cochlear length using the 'A' value for cochlea basal diameter: A feasibility study.

    Science.gov (United States)

    Deep, Nicholas L; Howard, Brittany E; Holbert, Sarah O; Hoxworth, Joseph M; Barrs, David M

    2017-07-01

    To determine whether the cochlea basal diameter (A value) measurement can be consistently and precisely obtained from high-resolution temporal bone imaging for use in cochlear length estimation. A feasibility study at a tertiary referral center was performed using the temporal bone CTs of 40 consecutive patients. The distance from the round window to the lateral wall was measured for each cochlea by two independent reviewers, a neuroradiologist and an otolaryngologist. The interrater reliability was calculated using the intraclass correlation coefficient (ICC) and the Bland-Altman plot. Forty patients (19 males, 21 females) for a total of 80 cochleae were included. Interrater reliability on the same ear had a high level of agreement by both the ICC and the Bland-Altman plot. ICCs were 0.90 (95% CI: 0.82, 0.94) for the left ear and 0.96 (95% CI: 0.92, 0.98) for the right ear. Bland-Altman plot confirmed interrater reliability with all 96% of measurements falling within the 95% limits of agreement. Measurement between the round window and lateral cochlear wall can be consistently and reliably obtained from high-resolution temporal bone CT scans. Thus, it is feasible to utilize this method to estimate the cochlear length of patients undergoing cochlear implantation.

  2. Second trimester cervical length measurement for prediction spontaneous preterm birth in an unselected risk population.

    Science.gov (United States)

    Peixoto, Alberto Borges; da Cunha Caldas, Taciana Mara Rodrigues; Tahan, Luisa Almeida; Petrini, Caetano Galvão; Martins, Wellington P; Costa, Fabricio Da Silva; Araujo Júnior, Edward

    2017-07-01

    To assess the predictive capacity of cervical length (CL) measurement underwent during the second trimester ultrasound for prediction preterm birth measurement (mm) using the transvaginal route was obtained in a sagittal view and the calipers positioned to measure the linear distance between the triangular area of echodensity at the external os and the internal os. To compare the preterm (measurement was dependent of gestational age by performing a linear regression and assessing the coefficient of determination (R2). We additionally assessed the accuracy of CL measurement to predict preterm birth by assessing the area under receiver operating characteristics curves with its respective confidence intervals (CIs) 95%. Preterm birth measurement and gestational age at delivery (R2=0.01, P=0.002). Receiver operating characteristics curve analysis of the ability of CL measurement to predict preterm birth measurement and gestational age at delivery. In an unselected population, CL measurement screening at 20 to 24+6 weeks of gestation does not seem to be a good predictor of preterm birth.

  3. Evaluation of a multimode fiber optic low coherence interferometer for path length resolved Doppler measurments of diffuse light

    OpenAIRE

    Varghese, Babu; Rajan, Vinayakrishnan; van Leeuwen, Ton; Steenbergen, Wiendelt

    2007-01-01

    The performance of a graded index multimode fiber optic low coherence Mach-Zehnder interferometer with phase modulation is analyzed. Investigated aspects were its ability to measure path length distributions and to perform path length resolved Doppler measurements of multiple scattered photons in a turbid suspension of particles undergoing Brownian and translational motion. The path length resolution of this instrument is compared with a system using single mode fibers for illumination and de...

  4. Electron Beam Probe As A Nondestructive Single Bunch Diagnostic Tool For Circular Colliders

    CERN Document Server

    Logatchev, P V; Dikanskij, N S; Frolov, A R; Gusev, Y A; Malutin, D A; Starostenko, A A

    2004-01-01

    In this article we present the experience of using electron beam probe (EBP) on VEPP-4. EBP is destined to determine such parameters of ultrarelativistic bunches of charged particles as centre of mass transverse position, longitudinal charge distribution, spatial orientation. The method is based on a deflection of a thin probe beam on an electromagnetic field of investigated ultrarelativistic bunch. Measured deflection value allows to calculate the spatial charge density. Detailed description of methods for reconstruction of bunch's parameters is presented in [1], [2], [3].

  5. Single Molecule Bioelectronics and Their Application to Amplification-Free Measurement of DNA Lengths.

    Science.gov (United States)

    Gül, O Tolga; Pugliese, Kaitlin M; Choi, Yongki; Sims, Patrick C; Pan, Deng; Rajapakse, Arith J; Weiss, Gregory A; Collins, Philip G

    2016-06-24

    As biosensing devices shrink smaller and smaller, they approach a scale in which single molecule electronic sensing becomes possible. Here, we review the operation of single-enzyme transistors made using single-walled carbon nanotubes. These novel hybrid devices transduce the motions and catalytic activity of a single protein into an electronic signal for real-time monitoring of the protein's activity. Analysis of these electronic signals reveals new insights into enzyme function and proves the electronic technique to be complementary to other single-molecule methods based on fluorescence. As one example of the nanocircuit technique, we have studied the Klenow Fragment (KF) of DNA polymerase I as it catalytically processes single-stranded DNA templates. The fidelity of DNA polymerases makes them a key component in many DNA sequencing techniques, and here we demonstrate that KF nanocircuits readily resolve DNA polymerization with single-base sensitivity. Consequently, template lengths can be directly counted from electronic recordings of KF's base-by-base activity. After measuring as few as 20 copies, the template length can be determined with <1 base pair resolution, and different template lengths can be identified and enumerated in solutions containing template mixtures.

  6. Single Molecule Bioelectronics and Their Application to Amplification-Free Measurement of DNA Lengths

    Directory of Open Access Journals (Sweden)

    O. Tolga Gül

    2016-06-01

    Full Text Available As biosensing devices shrink smaller and smaller, they approach a scale in which single molecule electronic sensing becomes possible. Here, we review the operation of single-enzyme transistors made using single-walled carbon nanotubes. These novel hybrid devices transduce the motions and catalytic activity of a single protein into an electronic signal for real-time monitoring of the protein’s activity. Analysis of these electronic signals reveals new insights into enzyme function and proves the electronic technique to be complementary to other single-molecule methods based on fluorescence. As one example of the nanocircuit technique, we have studied the Klenow Fragment (KF of DNA polymerase I as it catalytically processes single-stranded DNA templates. The fidelity of DNA polymerases makes them a key component in many DNA sequencing techniques, and here we demonstrate that KF nanocircuits readily resolve DNA polymerization with single-base sensitivity. Consequently, template lengths can be directly counted from electronic recordings of KF’s base-by-base activity. After measuring as few as 20 copies, the template length can be determined with <1 base pair resolution, and different template lengths can be identified and enumerated in solutions containing template mixtures.

  7. Radiation excited by a charged-particle bunch on a planar periodic wire structure

    Directory of Open Access Journals (Sweden)

    Andrey V. Tyukhtin

    2014-12-01

    Full Text Available The electromagnetic field of a bunch moving in the presence of a plane grid composed of thin parallel wires is considered by using the averaged boundary conditions method. Two different cases of motion are examined. In the first one, the bunch moves at a constant distance from the grid orthogonally to the wires. The excited surface wave is presented in the form of a spectral integral for a thin bunch with an arbitrary longitudinal profile. The wave propagates along the wires and does not decay with distance (if dissipation is negligible. Energy losses of the bunch over a unit path are obtained. In the second case, the bunch orthogonally crosses the wire grid. The volume and surface waves are separately analyzed. Properties of the spectral angular density of energy of volume radiation in the far-field zone are described. The energy losses due to the volume and surface radiation are determined. It is demonstrated that the structure of the surface waves in both cases allows determination of the length of the bunch.

  8. Calculating the Loss factor of the LCLS Beam Line Elements for Ultra-Shrot Bunches

    Energy Technology Data Exchange (ETDEWEB)

    Novokhatski, A.; /SLAC

    2009-10-17

    The Linac Coherent Light Source (LCLS) is a SASE 1.5-15 {angstrom} x-ray Free-Electron Laser (FEL) facility. Since an ultra-short intense bunch is used in the LCLS operation one might suggest that wake fields, generated in the vacuum chamber, may have an effect on the x-ray production because these fields can change the beam particle energies thereby increasing the energy spread in a bunch. At LCLS a feedback system precisely controls the bunch energy before it enters a beam transport line after the linac. However, in the transport line and later in the undulator section the bunch energy and energy spread are not under feedback control and may change due to wake field radiation, which depends upon the bunch current or on a bunch length. The linear part of the energy spread can be compensated in the upstream linac; the energy loss in the undulator section can be compensated by varying the K-parameter of the undulators, however we need a precise knowledge of the wake fields in this part of the machine. Resistive wake fields are known and well calculated. We discuss an additional part of the wake fields, which comes from the different vacuum elements like bellows, BPMs, transitions, vacuum ports, vacuum valves and others. We use the code 'NOVO' together with analytical estimations for the wake potential calculations.

  9. Seeding of self-modulation instability of a long electron bunch in a plasma.

    Science.gov (United States)

    Fang, Y; Yakimenko, V E; Babzien, M; Fedurin, M; Kusche, K P; Malone, R; Vieira, J; Mori, W B; Muggli, P

    2014-01-31

    We demonstrate experimentally that a relativistic electron bunch shaped with a sharp rising edge drives plasma wakefields with one to seven periods along the bunch as the plasma density is increased. The plasma density is varied in the 10(15)-10(17)  cm(-3) range. The wakefields generation is observed after the plasma as a periodic modulation of the correlated energy spectrum of the incoming bunch. We choose a low bunch charge of 50 pC for optimum visibility of the modulation at all plasma densities. The longitudinal wakefields creating the modulation are in the MV/m range and are indirect evidence of the generation of transverse wakefields that can seed the self-modulation instability, although the instability does not grow significantly over the short plasma length (2 cm). We show that the seeding provides a phase reference for the wakefields, a necessary condition for the deterministic external injection of a witness bunch in an accelerator. This electron work supports the concept of similar experiments in the future, e.g., SMI experiments using long bunches of relativistic protons.

  10. Comparison between Conventional Blind Embryo Transfer and Embryo Transfer Based on Previously Measured Uterine Length

    Directory of Open Access Journals (Sweden)

    Nasrin Saharkhiz

    2014-11-01

    Full Text Available Background: Embryo transfer (ET is one of the most important steps in assisted reproductive technology (ART cycles and affected by many factors namely the depth of embryo deposition in uterus. In this study, the outcomes of intracytoplasmic sperm injection (ICSI cycles after blind embryo transfer and embryo transfer based on previously measured uterine length using vaginal ultrasound were compared. Materials and Methods: This prospective randomised clinical trial included one hundred and forty non-donor fresh embryo transfers during January 2010 to June 2011. In group I, ET was performed using conventional (blind method at 5-6cm from the external os, and in group II, ET was done at a depth of 1-1.5 cm from the uterine fundus based on previously measured uterine length using vaginal sonography. Appropriate statistical analysis was performed using Student’s t test and Chi-square or Fisher’s exact test. The software that we used was PASW statistics version 18. A p value <0.05 was considered statistically significant. Results: Chemical pregnancy rate was 28.7% in group I and 42.1% in group II, while the difference was not statistically significant (p=0.105. Clinical pregnancy, ongoing pregnancy and implantation rates for group I were 21.2%, 17.7%, and 12.8%, while for group II were 33.9%, 33.9%, and 22.1, respectively. In group I and group II, abortion rates were 34.7% and 0%, respectively, indicating a statistically significant difference (p<0.005. No ectopic pregnancy occurred in two groups. Conclusion: The use of uterine length measurement during treatment cycle in order to place embryos at depth of 1-1.5cm from fundus significantly increases clinical and ongoing pregnancy and implantation rates, while leads to a decrease in abortion rate (Registration Number: IRCT2014032512494N1.

  11. Inlet Turbulence and Length Scale Measurements in a Large Scale Transonic Turbine Cascade

    Science.gov (United States)

    Thurman, Douglas; Flegel, Ashlie; Giel, Paul

    2014-01-01

    Constant temperature hotwire anemometry data were acquired to determine the inlet turbulence conditions of a transonic turbine blade linear cascade. Flow conditions and angles were investigated that corresponded to the take-off and cruise conditions of the Variable Speed Power Turbine (VSPT) project and to an Energy Efficient Engine (EEE) scaled rotor blade tip section. Mean and turbulent flowfield measurements including intensity, length scale, turbulence decay, and power spectra were determined for high and low turbulence intensity flows at various Reynolds numbers and spanwise locations. The experimental data will be useful for establishing the inlet boundary conditions needed to validate turbulence models in CFD codes.

  12. Length determination on industrial polymer parts from measurement performed under transient temperature conditions

    DEFF Research Database (Denmark)

    Dalla Costa, Giuseppe; Madruga, Daniel González; De Chiffre, Leonardo

    2016-01-01

    A way to reduce the cost of metrology in manufacturing is to perform dimensional verification directly in the production environment, avoiding a long and expensive acclimatization phase. In this work the effect of a transient temperature state, typical of the production environment...... the cooling phase, from 27 °C to 20 °C approximately. The length variation was measured by means of an inductive probe and the temperature with an RTD surface sensor. The frame of the system was composed by elements in Zerodur and Invar to minimize the thermal deformations of the structure. Uniform...

  13. Application of length vernier in phase coincidence detection and precision frequency measurement.

    Science.gov (United States)

    Miao, Miao; Wei, Zhou; Bin, Wang

    2012-02-01

    For comparison of arbitrary frequency signals, the paper proposed two levels of length vernier based on the time-space relationship are used in three levels of phase coincidence detecting circuits to extract the phase coincidence information by proper logic calculation. The length∕phase of each vernier is respectively corresponding to the accuracy and the resolution of detecting circuit. The time-space relationship is based on high-stability, high-accuracy, and high-speed of signal transmission. The method is effective to reduce the fuzzy region in the phase coincidence information and reach a higher measuring precision.

  14. Reliability, technical error of measurements and validity of length and weight measurements for children under two years old in Malaysia.

    Science.gov (United States)

    Jamaiyah, H; Geeta, A; Safiza, M N; Khor, G L; Wong, N F; Kee, C C; Rahmah, R; Ahmad, A Z; Suzana, S; Chen, W S; Rajaah, M; Adam, B

    2010-06-01

    The National Health and Morbidity Survey III 2006 wanted to perform anthropometric measurements (length and weight) for children in their survey. However there is limited literature on the reliability, technical error of measurement (TEM) and validity of these two measurements. This study assessed the above properties of length (LT) and weight (WT) measurements in 130 children age below two years, from the Hospital Universiti Kebangsaan Malaysia (HUKM) paediatric outpatient clinics, during the period of December 2005 to January 2006. Two trained nurses measured WT using Tanita digital infant scale model 1583, Japan (0.01kg) and Seca beam scale, Germany (0.01 kg) and LT using Seca measuring mat, Germany (0.1cm) and Sensormedics stadiometer model 2130 (0.1cm). Findings showed high inter and intra-examiner reliability using 'change in the mean' and 'intraclass correlation' (ICC) for WT and LT. However, LT was found to be less reliable using the 'Bland and Altman plot'. This was also true using Relative TEMs, where the TEM value of LT was slightly more than the acceptable limit. The test instruments were highly valid for WT using 'change in the mean' and 'ICC' but was less valid for LT measurement. In spite of this we concluded that, WT and LT measurements in children below two years old using the test instruments were reliable and valid for a community survey such as NHMS III within the limits of their error. We recommend that LT measurements be given special attention to improve its reliability and validity.

  15. Evaluation of a multimode fiber optic low coherence interferometer for path length resolved Doppler measurments of diffuse light

    NARCIS (Netherlands)

    Varghese, Babu; Rajan, Vinayakrishnan; van Leeuwen, Ton; Steenbergen, Wiendelt

    2007-01-01

    The performance of a graded index multimode fiber optic low coherence Mach-Zehnder interferometer with phase modulation is analyzed. Investigated aspects were its ability to measure path length distributions and to perform path length resolved Doppler measurements of multiple scattered photons in a

  16. Towards Attosecond High-Energy Electron Bunches: Controlling Self-Injection in Laser-Wakefield Accelerators Through Plasma-Density Modulation

    Science.gov (United States)

    Tooley, M. P.; Ersfeld, B.; Yoffe, S. R.; Noble, A.; Brunetti, E.; Sheng, Z. M.; Islam, M. R.; Jaroszynski, D. A.

    2017-07-01

    Self-injection in a laser-plasma wakefield accelerator is usually achieved by increasing the laser intensity until the threshold for injection is exceeded. Alternatively, the velocity of the bubble accelerating structure can be controlled using plasma density ramps, reducing the electron velocity required for injection. We present a model describing self-injection in the short-bunch regime for arbitrary changes in the plasma density. We derive the threshold condition for injection due to a plasma density gradient, which is confirmed using particle-in-cell simulations that demonstrate injection of subfemtosecond bunches. It is shown that the bunch charge, bunch length, and separation of bunches in a bunch train can be controlled by tailoring the plasma density profile.

  17. Numerical Calculation of Small-Angle Collimator Wakefields for Short Bunches

    Energy Technology Data Exchange (ETDEWEB)

    Bane, Karl LF

    2003-06-16

    Collimators are used to eliminate halo particles from the beam. To relax the wakefield effects a gradual transition from a large to a small aperture is used. However, the existing computer codes face severe problems for long tapered transitions. Two main sources of the problems are the grid dispersion and the staircase geometry approximation. Using recently developed time domain numerical approach, which is able to model curved boundaries and does not suffer from dispersion in longitudinal direction, we calculate the short-range geometric wakefields of the TESLA and NLC collimators. Wake fields and corresponding integral parameters are given for bunches of different length. The numerical results are compared to measurements and to analytical estimations. The applicability range for the analytical formulas is highlighted.

  18. Coherent synchrotron radiation and bunch stability in a compactstorage ring

    Energy Technology Data Exchange (ETDEWEB)

    Venturini, Marco; Warnock, Robert; Ruth, Ronald; Ellison, James A.

    2004-04-09

    We examine the effect of the collective force due to coherent synchrotron radiation (CSR) in an electron storage ring with small bending radius. In a computation based on time-domain integration of the nonlinear Vlasov equation, we find the threshold current for a longitudinal microwave instability induced by CSR alone. The model accounts for suppression of radiation at long wave lengths due to shielding by the vacuum chamber. In a calculation just above threshold, small ripples in the charge distribution build up over a fraction of a synchrotron period, but then die out to yield a relatively smooth but altered distribution with eventual oscillations in bunch length. The instability evolves from small noise on an initial smooth bunch of r.m.s.length much greater than the shielding cutoff. The paper includes a derivation and extensive analysis of the complete impedance function Z for synchrotron radiation with parallel plate shielding. We find corrections to the lowest approximation to the coherent force which involve ''off-diagonal'' values of Z, that is, fields with phase velocity not equal to the particle velocity.

  19. Angstrom-range optical path-length measurement with a high-speed scanning heterodyne optical interferometer.

    Science.gov (United States)

    Riza, Nabeel A; Arain, Muzammil A

    2003-05-01

    A highly accurate method of optical path-length measurement is introduced by use of a scanning heterodyne optical interferometer with no moving parts. The instrument has demonstrated the potential to measure optical path length at angstrom resolution over continuous thickness in the micrometer range. This optical path length can be used to calculate the thickness of any material if the refractive index is known or to measure the refractive index of the material if the thickness is known. The instrument uses a single acousto-optic device in an in-line ultra-stable reflective geometry to implement rapid scanning in the microsecond domain for thickness measurements of the test medium.

  20. Measurement of clavicular length and shortening after a midshaft clavicular fracture: Spatial digitization versus planar roentgen photogrammetry.

    Science.gov (United States)

    Stegeman, Sylvia A; de Witte, Pieter Bas; Boonstra, Sjoerd; de Groot, Jurriaan H; Nagels, Jochem; Krijnen, Pieta; Schipper, Inger B

    2016-08-01

    Clavicular shortening after fracture is deemed prognostic for clinical outcome and is therefore generally assessed on radiographs. It is used for clinical decision making regarding operative or non-operative treatment in the first 2weeks after trauma, although the reliability and accuracy of the measurements are unclear. This study aimed to assess the reliability of roentgen photogrammetry (2D) of clavicular length and shortening, and to compare these with 3D-spatial digitization measurements, obtained with an electromagnetic recording system (Flock of Birds). Thirty-two participants with a consolidated non-operatively treated two or multi-fragmented dislocated midshaft clavicular fracture were analysed. Two observers measured clavicular lengths and absolute and proportional clavicular shortening on radiographs taken before and after fracture consolidation. The clavicular lengths were also measured with spatial digitization. Inter-observer agreement on the radiographic measurements was assessed using the Intraclass Correlation Coefficient (ICC). Agreement between the radiographic and spatial digitization measurements was assessed using a Bland-Altman plot. The inter-observer agreement on clavicular length, and absolute and proportional shortening on trauma radiographs was almost perfect (ICC>0.90), but moderate for absolute shortening after consolidation (ICC=0.45). The Bland-Altman plot compared measurements of length on AP panorama radiographs with spatial digitization and showed that planar roentgen photogrammetry resulted in up to 37mm longer and 34mm shorter measurements than spatial digitization. Measurements of clavicular length on radiographs are highly reliable between observers, but may not reflect the actual length and shortening of the clavicle when compared to length measurements with spatial digitization. We recommend to use proportional shortening when measuring clavicular length or shortening on radiographs for clinical decision making. Copyright

  1. Space Charge Mitigation by Hollow Bunches

    CERN Multimedia

    Oeftiger, AO

    2014-01-01

    To satisfy the requirements of the HL-LHC (High Luminosity Large Hadron Collider), the LHC injector chain will need to supply a higher brightness, i.e. deliver the same transverse beam emittances \\epsilon_{x,y} while providing a higher intensity N. However, a larger number of particles per bunch enhances space charge effects. One approach to mitigate the impact of space charge is to change the longitudinal phase space distribution: hollow bunches feature a depleted bunch centre and a densely populated periphery. Thus, the spatial line density maximum is depressed which ultimately decreases the tune spread imposed by space charge. Therefore, a higher intensity can be accepted while keeping the same overall space charge tune shift. 3 different methods to create hollow bunches in the PSBooster are simulated.

  2. Flat Bunches with a Hollow Distribution for Space Charge Mitigation

    CERN Document Server

    Oeftiger, Adrian; Findlay, Alan James; Hancock, Steven; Rumolo, Giovanni

    2016-01-01

    Longitudinally hollow bunches provide one means to mitigate the impact of transverse space charge. The hollow distributions are created via dipolar parametric excitation during acceleration in CERN's Proton Synchrotron Booster. We present simulation work and beam measurements. Particular emphasis is given to the alleviation of space charge effects on the long injection plateau of the downstream Proton Synchrotron machine, which is the main goal of this study.

  3. In vivo fascicle length measurements via B-mode ultrasound imaging with single vs dual transducer arrangements.

    Science.gov (United States)

    Brennan, Scott F; Cresswell, Andrew G; Farris, Dominic J; Lichtwark, Glen A

    2017-11-07

    Ultrasonography is a useful technique to study muscle contractions in vivo, however larger muscles like vastus lateralis may be difficult to visualise with smaller, commonly used transducers. Fascicle length is often estimated using linear trigonometry to extrapolate fascicle length to regions where the fascicle is not visible. However, this approach has not been compared to measurements made with a larger field of view for dynamic muscle contractions. Here we compared two different single-transducer extrapolation methods to measure VL muscle fascicle length to a direct measurement made using two synchronised, in-series transducers. The first method used pennation angle and muscle thickness to extrapolate fascicle length outside the image (extrapolate method). The second method determined fascicle length based on the extrapolated intercept between a fascicle and the aponeurosis (intercept method). Nine participants performed maximal effort, isometric, knee extension contractions on a dynamometer at 10° increments from 50 to 100° of knee flexion. Fascicle length and torque were simultaneously recorded for offline analysis. The dual transducer method showed similar patterns of fascicle length change (overall mean coefficient of multiple correlation was 0.76 and 0.71 compared to extrapolate and intercept methods respectively), but reached different absolute lengths during the contractions. This had the effect of producing force-length curves of the same shape, but each curve was shifted in terms of absolute length. We concluded that dual transducers are beneficial for studies that examine absolute fascicle lengths, whereas either of the single transducer methods may produce similar results for normalised length changes, and repeated measures experimental designs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Space Charge Mitigation With Longitudinally Hollow Bunches

    CERN Multimedia

    Oeftiger, Adrian; Rumolo, Giovanni

    2016-01-01

    Hollow longitudinal phase space distributions have a flat profile and hence reduce the impact of transverse space charge. Dipolar parametric excitation with the phase loop feedback systems provides such hollow distributions under reproducible conditions. We present a procedure to create hollow bunches during the acceleration ramp of CERN’s PS Booster machine with minimal changes to the operational cycle. The improvements during the injection plateau of the downstream Proton Synchrotron are assessed in comparison to standard parabolic bunches.

  5. Space charge mitigation with longitudinally hollow bunches

    CERN Document Server

    AUTHOR|(CDS)2088716; Hancock, Steven; Rumolo, Giovanni; CERN. Geneva. ATS Department

    2016-01-01

    Suitably, hollow longitudinal phase space distributions have a flat profile and hence reduce the impact of transverse space charge. Dipolar parametric excitation with the phase loop feedback systems provides such hollow distributions under reproducible conditions. We present a procedure to create hollow bunches during the acceleration ramp of CERN’s PS Booster machine with minimal changes to the operational cycle. The improvements during the injection plateau of the downstream Proton Synchrotron are assessed in comparison to standard parabolic bunches.

  6. Sagittal Spine Length Measurement: A Novel Technique to Assess Growth of the Spine.

    Science.gov (United States)

    Spurway, Alan J; Chukwunyerenwa, Chukwudi K; Kishta, Waleed E; Hurry, Jennifer K; El-Hawary, Ron

    2016-09-01

    The accuracy and repeatability of a novel sagittal spine length (SSL) radiographic measurement was examined using photographic and radiographic imaging. To validate the new SSL technique for measuring growth in early-onset scoliosis (EOS) patients. Current assessment of patient growth undergoing growth-friendly surgical treatment for EOS is the use of serial vertical spine height measurements (VH) on coronal radiographs. Spine-based distraction implants are able to control the coronal plane deformity of scoliosis, but exhibit a "law of diminishing returns" in the impact of each follow-up lengthening surgery. As these treatments are kyphogenic, we hypothesize that the increase in kyphosis is, in fact, growth out of plane, not captured by standard spine height measurements. Measurement accuracy was assessed using 6 spine model alignments and clinical radiographs of 23 retrospective EOS patients. Inter- and intrarater reliabilities were assessed using interclass coefficient (ICC) analyses. The discrepancy between the VH and SSL was also investigated. The model assessment showed excellent accuracy, with a 1.54 mm (SD: 1.07, range: 0.03-3.14, p = .226) mean error and mean ICCs of 0.999. As the kyphosis increased, a progressive difference between the phantom VH and SSL was observed. Interrater reliability ICCs of the clinical radiographs averaged 0.981 and 0.804, whereas intrarater reliabilities averaged 0.966 and 0.826, for the coronal and sagittal radiographs, respectively. Mean clinical SSLs were 177.5 mm (SD: 28.5, range: 114.3-250.3), whereas the VH averaged 161.6 mm (SD: 31.8, range: 58.5-243.0), resulting in a 16.0-mm (SD: 16.7, range: 0.3-90.3, p < .0001) difference between the two measurements with a progressive difference as the kyphosis increased. The novel SSL measurement is accurate, repeatable, and complements the current growth assessments for EOS treatments. Until sagittal spine lengths are taken into consideration, the "law of diminishing returns" should

  7. Foot length measurements of newborns of high and low risk pregnancies.

    Science.gov (United States)

    Salge, Ana Karina Marques; Rocha, Érika Lopes; Gaíva, Maria Aparecida Munhoz; Castral, Thaíla Correa; Guimarães, Janaína Valadares; Xavier, Raphaela Maioni

    2017-03-09

    Comparing foot length measurements of newborns in high and low risk pregnancies at a public hospital in Goiânia, GO, Brazil. A cross-sectional study carried out between April, 2013 and May, 2015, with a sample consisting of 180 newborns; 106 infants of women from high-risk pregnancies and 74 of women from low-risk pregnancies. Data were descriptively analyzed. Foot length measurement was performed using a stiff transparent plastic ruler, graduated in millimeters. The length of both feet was measured from the tip of the hallux (big toe) to the end of the heel. A statistically significant relationship was found between the foot length and newborn's weight, between the cephalic and thoracic perimeters in the high-risk group and between the cephalic perimeter in the control group. There is a need for creating cut-off points to identify newborns with intrauterine growth disorders using foot length. Comparar as medidas do comprimento hálux-calcâneo de recém-nascidos em gestações de alto e baixo risco em um hospital público de Goiânia, GO. Estudo transversal, realizado no período de abril de 2013 a maio de 2015, cuja amostra constituiu-se de 180 recém-nascidos, 106 filhos de mulheres com gestação de alto risco e 74 de mulheres com gestação de baixo risco. Os dados foram analisados descritivamente. A medida do comprimento hálux-calcâneo foi realizada utilizando-se de régua plástica transparente rígida, graduada em milímetros. Foram medidos ambos os pés, aferindo-se o comprimento da ponta do hálux até a extremidade do calcâneo. Foi encontrada relação estatisticamente significante entre o comprimento hálux-calcâneo e o peso do recém-nascido, entre os perímetros cefálico e torácico no grupo de alto risco e entre o perímetro cefálico no grupo controle. Existe necessidade da criação de pontos de corte para identificar recém-nascidos com desvios de crescimento intrauterino utilizando-se do comprimento hálux-calcâneo. Comparar las mediciones

  8. Measurement of the attenuation length of argon scintillation light in the ArDM LAr TPC

    Science.gov (United States)

    Calvo, J.; Cantini, C.; Crivelli, P.; Daniel, M.; Di Luise, S.; Gendotti, A.; Horikawa, S.; Molina-Bueno, L.; Montes, B.; Mu, W.; Murphy, S.; Natterer, G.; Nguyen, K.; Periale, L.; Quan, Y.; Radics, B.; Regenfus, C.; Romero, L.; Rubbia, A.; Santorelli, R.; Sergiampietri, F.; Viant, T.; Wu, S.

    2018-01-01

    We report on a measurement of the attenuation length for the scintillation light in the tonne size liquid argon target of the ArDM dark matter experiment. The data was recorded in the first underground operation of the experiment in single-phase operational mode. The results were achieved by comparing the light yield spectra from 39Ar and 83mKr to a description of the ArDM setup with a model of full light ray tracing. A relatively low value close to 0.5 m was found for the attenuation length of the liquid argon bulk to its own scintillation light. We interpret this result as a presence of optically active impurities in the liquid argon which are not filtered by the installed purification systems. We also present analyses of the argon gas employed for the filling and discuss cross sections in the vacuum ultraviolet of various molecules in respect to purity requirements in the context of large liquid argon installations.

  9. Discrimination between monomorphic and polymorphic ventricular tachycardia using cycle length variability measured by wavelet transform analysis.

    Science.gov (United States)

    Sierra, G; Gómez, M J; Le Guyader, P; Trelles, F; Cardinal, R; Savard, P; Nadeau, R

    1998-07-01

    normalized standard deviation of the intervals between individual electrograms (0.076 +/- 0.006). No significant differences were shown (P = .0022), and a strong linear correlation was found between both measurements (Pearson correlation coefficient, .966). It is concluded that WT analysis discriminated accurately between MVT and PVT, and a quantitative relation was found with the spatial dispersion of sites of earliest epicardial activation. The WT results strongly correlated with those obtained by another method of estimating cycle length variability. Methodologically, the strength of the WT lies in the complementary information that could be extracted from the processing of electrograms to enhance the detection/discrimination of different types of arrhythmias.

  10. Retrieval of Effective Correlation Length and Snow Water Equivalent from Radar and Passive Microwave Measurements

    Directory of Open Access Journals (Sweden)

    Juha Lemmetyinen

    2018-01-01

    Full Text Available Current methods for retrieving SWE (snow water equivalent from space rely on passive microwave sensors. Observations are limited by poor spatial resolution, ambiguities related to separation of snow microstructural properties from the total snow mass, and signal saturation when snow is deep (~>80 cm. The use of SAR (Synthetic Aperture Radar at suitable frequencies has been suggested as a potential observation method to overcome the coarse resolution of passive microwave sensors. Nevertheless, suitable sensors operating from space are, up to now, unavailable. Active microwave retrievals suffer, however, from the same difficulties as the passive case in separating impacts of scattering efficiency from those of snow mass. In this study, we explore the potential of applying active (radar and passive (radiometer microwave observations in tandem, by using a dataset of co-incident tower-based active and passive microwave observations and detailed in situ data from a test site in Northern Finland. The dataset spans four winter seasons with daily coverage. In order to quantify the temporal variability of snow microstructure, we derive an effective correlation length for the snowpack (treated as a single layer, which matches the simulated microwave response of a semi-empirical radiative transfer model to observations. This effective parameter is derived from radiometer and radar observations at different frequencies and frequency combinations (10.2, 13.3 and 16.7 GHz for radar; 10.65, 18.7 and 37 GHz for radiometer. Under dry snow conditions, correlations are found between the effective correlation length retrieved from active and passive measurements. Consequently, the derived effective correlation length from passive microwave observations is applied to parameterize the retrieval of SWE using radar, improving retrieval skill compared to a case with no prior knowledge of snow-scattering efficiency. The same concept can be applied to future radar

  11. Longitudinal transport measurements in an energy recovery accelerator with triple bend achromat arcs

    Directory of Open Access Journals (Sweden)

    F. Jackson

    2016-12-01

    Full Text Available Longitudinal properties of electron bunches (energy spread and bunch length and their manipulation are of importance in free electron lasers (FELs, where magnetic bunch length compression is a common feature of beam transport. Recirculating accelerators and energy recovery linac accelerators (ERLs have been used as FEL drivers for several decades and control of longitudinal beam transport is particularly important in their magnet lattices. We report on measurements of longitudinal transport properties in an ERL-FEL, the ALICE (Accelerators and Lasers in Combined Experiments accelerator at Daresbury Laboratory. ALICE is an energy recovery research accelerator that drives an infrared free electron laser. By measuring the time of arrival of electron bunches, the canonical longitudinal transport quantities were measured in the beam transport and bunch compression sections of the lattice. ALICE includes a four-dipole bunch compression chicane providing fixed longitudinal transport, and triple bend achromat arcs including sextupole magnets where the first and second order longitudinal transport can be adjusted. The longitudinal transport properties in these lattice sections were measured and compared with the theoretical model of the lattice. A reasonable level of agreement has been found. The effect of sextupoles in second order, as well as first order, longitudinal correction is considered, with the measurements indicating the level of alignment of the beam to the center of the sextupole.

  12. Properties of Trapped Electron Bunches in a Plasma Wakefield Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kirby, Neil; /SLAC

    2009-10-30

    electron bunches. Chapters four and five present the experimental diagnostics and measurements for the trapped electrons. Next, the sixth chapter introduces suggestions for future trapped electron experiments. Then, Chapter seven contains the conclusions. In addition, there is an appendix chapter that covers a topic which is extraneous to electron trapping, but relevant to the PWFA. This chapter explores the feasibility of one idea for the production of a hollow channel plasma, which if produced could solve some of the remaining issues for a plasma-based collider.

  13. Transvaginal ultrasonographic measurement of cervical length in asymptomatic high-risk women with a short cervical length in the previous pregnancy.

    Science.gov (United States)

    Crane, J M G; Hutchens, D

    2011-07-01

    To determine if asymptomatic women at high risk of preterm delivery who had a short cervical length in their previous pregnancy and delivered at term are at increased risk of having a short cervical length in their next pregnancy, and whether they are at increased risk of preterm birth. This retrospective cohort study included high-risk (those with a history of spontaneous preterm birth, uterine anomaly or excisional treatment for cervical dysplasia) asymptomatic women who were pregnant with a singleton gestation delivering between April 2003 and March 2010, who had had a previous pregnancy and who had transvaginal ultrasonographic cervical length measurement performed at 16-30 weeks' gestation in both pregnancies. Comparison was among women who had a short cervical length (pregnancy but delivered at term in that pregnancy (Short Term Group), women with a history of a normal cervical length (≥ 3.0 cm) in their previous pregnancy delivering at term (Long Term Group), and women who had a short cervical length (pregnancy delivering preterm (Short Preterm Group). Primary outcomes were spontaneous preterm birth at pregnancy compared with those in the Long Term Group (10/23 (43.5%) vs. 4/26 (15.4%), respectively) but not as likely as women in the Short Preterm Group (9/13 (69.2%); P=0.003). Women in the Short Term Group were not at an increased risk of spontaneous preterm birth at pregnancy compared with women in the Long Term Group (2/23 (8.7%) vs. 2/26 (7.7%), respectively), but women in the Short Preterm Group were at an increased risk (6/13 (46.2%); Prisk of threatened preterm labor (6/23 (26.1%) and 4/26 (15.4%) vs. 9/13 (69.2%), respectively; P=0.002) and of receiving corticosteroids for fetal lung maturation (6/23 (26.1%) and 4/26 (15.4%) vs. 11/13 (84.6%), respectively; Phigh-risk asymptomatic women with a short cervical length in their previous pregnancy who delivered at term are at increased risk of having a short cervix in their next pregnancy, they are not

  14. Method for the determination of the three-dimensional structure of ultrashort relativistic electron bunches

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca; Ilinski, Petr; Saldin, Evgeni; Schneidmiller, Evgeni; Yurkov, Mikhail

    2009-05-15

    We describe a novel technique to characterize ultrashort electron bunches in Xray Free-Electron Lasers. Namely, we propose to use coherent Optical Transition Radiation to measure three-dimensional (3D) electron density distributions. Our method relies on the combination of two known diagnostics setups, an Optical Replica Synthesizer (ORS) and an Optical Transition Radiation (OTR) imager. Electron bunches are modulated at optical wavelengths in the ORS setup.When these electron bunches pass through a metal foil target, coherent radiation pulses of tens MW power are generated. It is thereafter possible to exploit advantages of coherent imaging techniques, such as direct imaging, diffractive imaging, Fourier holography and their combinations. The proposed method opens up the possibility of real-time, wavelength-limited, single-shot 3D imaging of an ultrashort electron bunch. (orig.)

  15. Measurement of the local optical properties of turbid media by differential path-length spectroscopy.

    Science.gov (United States)

    Amelink, Arjen; Sterenborg, Henricus J

    2004-05-20

    We report on the development of an optical-fiber-based diagnostic tool with which to determine the local optical properties of a turbid medium. By using a single fiber in contact with the medium to deliver and detect white light, we have optimized the probability of detection of photons scattered from small depths. The contribution of scattered light from greater depths to the signal is measured and subtracted with an additional fiber, i.e., a collection fiber, to yield a differential backscatter signal. Phantoms demonstrate that, when photons have large mean free paths compared with the fiber diameter, single scattering dominates the differential backscatter signal. When photons have small mean free paths compared with the fiber diameter, the apparent path length of the photons that contribute to the differential backscatter signal becomes approximately equal to 4/5 of the fiber diameter. This effect is nearly independent of the optical properties of the sample under investigation.

  16. Local transport measurements at mesoscopic length scales using scanning tunneling potentiometry.

    Science.gov (United States)

    Wang, Weigang; Munakata, Ko; Rozler, Michael; Beasley, Malcolm R

    2013-06-07

    Under mesoscopic conditions, the transport potential on a thin film carrying a current is theoretically expected to bear spatial variation due to quantum interference. Scanning tunneling potentiometry is the ideal tool to investigate such variation, by virtue of its high spatial resolution. We report in this Letter the first detailed measurement of transport potential under mesoscopic conditions. Epitaxial graphene at a temperature of 17 K was chosen as the initial system for study because the characteristic transport length scales in this material are relatively large. Tip jumping artifacts are a major possible contribution to systematic errors; and we mitigate such problems by using custom-made slender and sharp tips manufactured by focused ion beam. In our data, we observe residual resistivity dipoles associated with topographical defects, and local peaks and dips in the potential that are not associated with topographical defects.

  17. First $\\pi K$ atom lifetime and $\\pi K$ scattering length measurements

    CERN Document Server

    Adeva, B; Allkofer, Y; Amsler, C; Anania, A; Aogaki, S; Benelli, A; Brekhovskikh, V; Cechak, T; Chiba, M; Chliapnikov, P; Ciocarlan, C; Constantinescu, S; Doskarova, P; Drijard, D; Dudarev, A; Duma, M; Dumitriu, D; Fluerasu, D; Gorin, A; Gorchakov, O; Gritsay, K; Guaraldo, C; Gugiu, M; Hansroul, M; Hons, Z; Horikawa, S; Iwashita, Y; Karpukhin, V; Kluson, J; Kobayashi, M; Kruglov, V; Kruglova, L; Kulikov, A; Kulish, E; Kuptsov, A; Lamberto, A; Lanaro, A; Lednicky, R; Marinas, C; Martincik, J; Nemenov, L; Nikitin, M; Okada, K; Olchevskii, V; Pentia, M; Penzo, A; Plo, M; Ponta, T; Prusa, P; Rappazzo, G; Romero Vidal, A; Ryazantsev, A; Rykalin, V; Schacher, J; Sidorov, A; Smolik, J; Sugimoto, S; Takeutchi, F; Tauscher, L; Trojek, T; Trusov, S; Urban, T; Vrba, T; Yazkov, V; Yoshimura, Y; Zhabitsky, M; Zrelov, P

    2014-01-01

    The results of a search for hydrogen-like atoms consisting of $\\pi^{\\mp}K^{\\pm}$ mesons are presented. Evidence for $\\pi K$ atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic $\\pi K$ pairs from their breakup in the same target ($178 \\pm 49$) and from Coulomb final state interaction ($653 \\pm 42$). Using these results the analysis yields a first value for the $\\pi K$ atom lifetime of $\\tau=(2.5_{-1.8}^{+3.0})$ fs and a first model-independent measurement of the S-wave isospin-odd $\\pi K$ scattering length $\\left|a_0^-\\right|=\\frac{1}{3}\\left|a_{1/2}-a_{3/2}\\right|= \\left( 0.11_{-0.04}^{+0.09} \\right)M_{\\pi}^{-1}$ ($a_I$ for isospin $I$).

  18. Longitudinal coupled-bunch instability studies in the PS

    CERN Document Server

    Damerau, H

    2017-01-01

    The main longitudinal limitation for LHC-type beams inthe PS are coupled-bunch instabilities. A dedicated proto-typefeedbacksystemusingaFinemetcavityasalongitudinalkicker has been installed. Extensive tests with beam havebeen performed to explore the intensity reach with this feed-back. The maximum intensity with nominal longitudinalemittance at PS extraction has been measured, as well as theemittance required to keep the beam longitudinally stableat the design intensity for the High-Luminosity LHC (HL-LHC). A higher-harmonic cavity is a complementary op-tion to extend the intensity reach beyond the capabilities ofthe coupled-bunch feedback. Preliminary machine develop-ment (MD) studies operating one20MHzor one40MHzRF system as a higher harmonic at the flat-top indicate thebeneficial effect on longitudinal beam stability

  19. Higher-order photon bunching in a semiconductor microcavity

    DEFF Research Database (Denmark)

    Assmann, M.; Veit, F.; Bayer, M.

    2009-01-01

    Quantum mechanically indistinguishable particles such as photons may show collective behavior. Therefore, an appropriate description of a light field must consider the properties of an assembly of photons instead of independent particles. We have studied multiphoton correlations up to fourth order...... in the single-mode emission of a semiconductor microcavity in the weak and strong coupling regimes. The counting statistics of single photons were recorded with picosecond time resolution, allowing quantitative measurement of the few-photon bunching inside light pulses. Our results show bunching behavior...... in the strong coupling case, which vanishes in the weak coupling regime as the cavity starts lasing. In particular, we verify the n factorial prediction for the zero-delay correlation function of n thermal light photons....

  20. Optical path-length modulation for three-dimensional particle measurement in mirror-embedded microchannels.

    Science.gov (United States)

    Choi, Sungyoung; Kim, Seung-Hoon; Park, Je-Kyun

    2010-02-07

    Simple and low-cost implementation of three-dimensional (3D) particle measurement is vital for designing and characterizing microfluidic devices that show spatiotemporally varying characteristics in three dimensions. However, the conventional 3D particle image velocimetry or particle streak velocimetry has proven difficult to address the needs, requiring complex and expensive equipment, precise alignment between optical components, and specialized image-processing algorithms. Here, we report mirror-embedded microchannels and a method of optical path-length (OPL) modulation for 3D particle measurement in the channels. The mirror, ideally at 45 degrees, reflects the side view of the channels and enables 3D positional information to be obtained easily from two different orthogonal-axis images with different optical paths. To offset the optical path difference between two image views, we utilized a cover glass as a medium of high refractive index and placed it in the light path through which the side-view image propagates, thereby prolonging the OPL of the side view and simultaneously shifting its depth of field (DOF) range. This modulation ensures imaging of in-focus side view as well as top view. This 3D imaging principle was verified by observing 3D positions of 6 mum-sized beads in the linear and grooved microchannels. The mirror-embedded scheme can be readily fabricated with existing microfluidic designs, and offer easy and simple implementation of 3D particle measurement.

  1. Spectral reflectance of oil-palm (Elaeis guineensis Jacq. bunches as indicator for optimal harvesting

    Directory of Open Access Journals (Sweden)

    Wunsri, S.

    2005-12-01

    Full Text Available To determine the appropriate harvesting time of Tenera oil palm bunches, the spectral reflectance of ripening bunches was investigated from images taken by a digital Canon PowerShot A20 camera. Every second day images were taken from selected bunches at an oil-palm estate during the growth of the bunchesfrom immaturity to the over-ripe phase, to trace the changes in color which correlate with the process of ripening. The images were analyzed measuring the changes in the three basic colors red, green and blue, using a specially developed Color Analysis computer program for Oil-palm 'fruit' (CAOP, and determining the correlation with the measured palm-oil content of the nuts.Of the three color-bands, the red light reflectance showed the best correlation with ripeness, as the red color increased regularly and practically linearly up to the stage of the maximal oil yield. Some seven days after the thus determined optimal harvesting date for the ripe bunches, some of the ripe nuts will detachfrom the bunch and fall, but then it is too late to use the fallen nuts as indicators for harvesting. From our investigations in the field and in the laboratory we recommend that harvesting should follow immediately after the red reflectance starts declining, after having reached its peak value for the Tenera oil-palm some 5±3 days before nuts begin to detach from the bunch.

  2. Photoperiodic control of diapause induction in the zygaenid moth Thyrassia penangae – involving day-length measurement

    Directory of Open Access Journals (Sweden)

    He H

    2017-01-01

    Full Text Available Hai-Min He, Chao Chen, Hai-Jun Xiao, Fang-Sen Xue Institute of Entomology, Jiangxi Agricultural University, Nanchang, People’s Republic of China Abstract: The zygaenid moth Thyrassia penangae is a typical long-day species, entering winter diapause as a prepupa in a cocoon in response to short-day conditions during autumn. The previous photoperiodic responses under non-24-h light–dark cycle and Nanda–Hamner experiments (greatly extended dark periods coupled with a short photophase or a long photophase revealed that the moth measured day length rather than night length in the determination of diapause. In this study, we further extend non-24-h light–dark cycle experiments and use the Bünsow experiment (the extended scotophase or photophase interrupted by 1-h light pulse or 1-h dark interruption to test the photoperiodism for diapause induction of this moth. The extended non-24-h light–dark cycle experiment showed that when the length of photophase exceeded critical day length, diapause incidence was quite low regardless of scotophase duration. No circadian rhythmicity was found in Bünsow experiments. The incidence of diapause was consistently low when preinterruption photophase was longer than the critical day length. The two experiments provide further evidence that this moth measures day length instead of night length. Keywords: Thyrassia penangae, diapause, photoperiodism, day-length measurement, Bünsow experiment

  3. Effects of correlation in transition radiation of super-short electron bunches

    Science.gov (United States)

    Danilova, D. K.; Tishchenko, A. A.; Strikhanov, M. N.

    2017-07-01

    The effect of correlations between electrons in transition radiation is investigated. The correlation function is obtained with help of the approach similar to the Debye-Hückel theory. The corrections due to correlations are estimated to be near 2-3% for the parameters of future projects SINBAD and FLUTE for bunches with extremely small lengths (∼1-10 fs). For the bunches with number of electrons about ∼ 2.5 ∗1010 and more, and short enough that the radiation would be coherent, the corrections due to correlations are predicted to reach 20%.

  4. Extremely short relativistic-electron-bunch generation in the laser wakefield via novel bunch injection scheme

    NARCIS (Netherlands)

    Khachatryan, A.G.; van Goor, F.A.; Boller, Klaus J.; Reitsma, A.J.W.; Jaroszynski, D.A.

    2004-01-01

    Recently a new electron-bunch injection scheme for the laser wakefield accelerator has been proposed [JETP Lett. 74, 371 (2001); Phys. Rev. E 65, 046504 (2002)]. In this scheme, a low energy electron bunch, sent in a plasma channel just before a high-intensity laser pulse, is trapped in the laser

  5. Curvature-Induced Bunch Self-Interaction for an Energy-Chirped Bunch in Magnetic Bends

    Energy Technology Data Exchange (ETDEWEB)

    Rui Li

    2006-01-04

    The curvature-induced bunch collective interaction in magnetic bends can be studied using effective forces in the canonical formulation of the coherent synchrotron radiation (CSR) effect. In this paper, for an electron distribution moving ultrarelativistically in a bending system, the dynamics of a particle in the electron distribution is derived from the Hamiltonian of the particle in terms of the bunch internal coordinates. The consequent Vlasov equation manifests explicitly how the phase space distribution is perturbed by the effective CSR forces. In particular, we study the impact of an initial linear energy chirp of the bunch on the behavior of the effective longitudinal CSR force, which arises due to the modification of the retardation relation as a result of the energy-chirping-induced longitudinal-horizontal correlation of the bunch distribution (bunch tilt) in dispersive regions.

  6. LHC Report: Boost in bunches brings record luminosity

    CERN Multimedia

    2011-01-01

    Having hit a luminosity of around 8.4x1032 cm-2 s-1 with 768 bunches per beam, the LHC went into a 5-day machine development (MD) program on Wednesday 4 May. Operators are now working on increasing the number of particle bunches in the machine towards a 2011 maximum of around 1380 bunches. The team is already hitting major milestones, recording another record-breaking peak luminosity on Monday 23 May.   Former LHC Project Leader Lyn Evans (to the right) and Laurette Ponce, the engineer-in-charge when the recent luminosity record was achieved. The MD periods improve our understanding of the machine, with the aim of increasing its short- and long-term performance. This one also included tests of the machine’s configurations for special physics runs and a future high luminosity LHC. It was an intense program and overall it went very well, with most measurements carried out successfully. Highlights included: commissioning a dedicated machine setup for TOTEM and ALFA; succe...

  7. Loss of Landau Damping for Bunch Oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Burov, A.; /Fermilab

    2011-04-11

    Conditions for the existence, uniqueness and stability of self-consistent bunch steady states are considered. For the existence and uniqueness problems, simple algebraic criteria are derived for both the action and Hamiltonian domain distributions. For the stability problem, van Kampen theory is used. The onset of a discrete van Kampen mode means the emergence of a coherent mode without any Landau damping; thus, even a tiny couple-bunch or multi-turn wake is sufficient to drive the instability. The method presented here assumes an arbitrary impedance, RF shape, and beam distribution function. Available areas on the intensity-emittance plane are shown for resistive wall wake and single harmonic, bunch shortening and bunch lengthening RF configurations. Thresholds calculated for the Tevatron parameters and impedance model are in agreement with the observations. These thresholds are found to be extremely sensitive to the small-argument behaviour of the bunch distribution function. Accordingly, a method to increase the LLD threshold is suggested. This article summarizes and extends recent author's publications.

  8. Estimates of post-acceleration longitudinal bunch compression

    Energy Technology Data Exchange (ETDEWEB)

    Judd, D.L.

    1977-11-25

    A simple analytic method is developed, based on physical approximations, for treating transient implosive longitudinal compression of bunches of heavy ions in an accelerator system for ignition of inertial-confinement fusion pellet targets. Parametric dependences of attainable compressions and of beam path lengths and times during compression are indicated for ramped pulsed-gap lines, rf systems in storage and accumulator rings, and composite systems, including sections of free drift. It appears that for high-confidence pellets in a plant producing 1000 MW of electric power the needed pulse lengths cannot be obtained with rings alone unless an unreasonably large number of them are used, independent of choice of rf harmonic number. In contrast, pulsed-gap lines alone can meet this need. The effects of an initial inward compressive drift and of longitudinal emittance are included.

  9. Standard test method for In-Plane length measurements of thin, reflecting films using an optical interferometer

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This test method covers a procedure for measuring in-plane lengths (including deflections) of patterned thin films. It applies only to films, such as found in microelectromechanical systems (MEMS) materials, which can be imaged using an optical interferometer. 1.2 There are other ways to determine in-plane lengths. Using the design dimensions typically provides more precise in-plane length values than using measurements taken with an optical interferometer. (Interferometric measurements are typically more precise than measurements taken with an optical microscope.) This test method is intended for use when interferometric measurements are preferred over using the design dimensions (for example, when measuring in-plane deflections and when measuring lengths in an unproven fabrication process). 1.3 This test method uses a non-contact optical interferometer with the capability of obtaining topographical 3-D data sets. It is performed in the laboratory. 1.4 The maximum in-plane length measured is determine...

  10. Bunch decompression for laser-plasma driven free-electron laser demonstration schemes

    Directory of Open Access Journals (Sweden)

    T. Seggebrock

    2013-07-01

    Full Text Available X-ray free-electron lasers (FELs require a very high electron beam quality in terms of emittance and energy spread. Since 2004 high quality electrons produced by laser-wakefield accelerators have been demonstrated, but the electron quality up to now did not allow the operation of a compact x-ray FEL using these electrons. Maier et al. [Phys. Rev. X 2, 031019 (2012PRXHAE2160-330810.1103/PhysRevX.2.031019] suggested a concept for a proof-of-principle experiment allowing FEL operation in the vacuum ultraviolet range based on an optimized undulator and bunch decompression using electron bunches from a laser-plasma accelerator as currently available. In this paper we discuss in more detail how a chicane can be used as a bunch stretcher instead of a bunch compressor to allow the operation of a laser-wakefield accelerator driven FEL using currently available electrons. A scaling characterizing the impact of bunch decompression on the gain length is derived and the feasibility of the concept is tested numerically in a demanding scenario.

  11. Cell length measurements in longitudinal smooth muscle strips of the pig urinary bladder

    NARCIS (Netherlands)

    E. van Asselt (Els); R. Schot (Rachel); R. van Mastrigt (Ron)

    1993-01-01

    textabstractIn this study the length of smooth muscle cells in muscle bundles of pig urinary bladder wall was determined after dissection in Tyrode buffers with different calcium concentrations ([Ca2+]). Previous studies have shown that the length of isolated smooth muscle cells decreases with an

  12. How Does Definition of Minimum Break Length Affect Objective Measures of Sitting Outcomes Among Office Workers?

    DEFF Research Database (Denmark)

    Kloster, Stine; Danquah, Ida Høgstedt; Holtermann, Andreas

    2017-01-01

    described how the definition of minimum break duration affects sitting outcomes. Therefore, the aim was to address how definitions of break length affect total sitting time, number of sit-to-stand transitions, prolonged sitting periods and time accumulated in prolonged sitting periods among office workers......-to-stand transitions decreased, and number of prolonged sitting periods and total time accumulated in prolonged sitting periods increased, with increasing minimum break length. Total sitting time was not influenced by varying break length. CONCLUSIONS: The definition of minimum break length influenced the sitting...... outcomes with the exception of total sitting time. A standard definition of break length is needed for comparison and interpretation of studies in the evolving research field of sedentary behaviour....

  13. Evaluation of a multimode fiber optic low coherence interferometer for path length resolved Doppler measurements of diffuse light.

    Science.gov (United States)

    Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G; Steenbergen, Wiendelt

    2007-12-01

    The performance of a graded index multimode fiber optic low coherence Mach-Zehnder interferometer with phase modulation is analyzed. Investigated aspects were its ability to measure path length distributions and to perform path length resolved Doppler measurements of multiple scattered photons in a turbid suspension of particles undergoing Brownian and translational motion. The path length resolution of this instrument is compared with a system using single mode fibers for illumination and detection. The optical path lengths are determined from the zero order moment of the phase modulation peak in the power spectrum. The weighted first moment, which is equal to the average Doppler shift, shows a linear response for different mean flow velocities within the physiological range.

  14. Evaluation of a multimode fiber optic low coherence interferometer for path length resolved Doppler measurements of diffuse light

    Science.gov (United States)

    Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G.; Steenbergen, Wiendelt

    2007-12-01

    The performance of a graded index multimode fiber optic low coherence Mach-Zehnder interferometer with phase modulation is analyzed. Investigated aspects were its ability to measure path length distributions and to perform path length resolved Doppler measurements of multiple scattered photons in a turbid suspension of particles undergoing Brownian and translational motion. The path length resolution of this instrument is compared with a system using single mode fibers for illumination and detection. The optical path lengths are determined from the zero order moment of the phase modulation peak in the power spectrum. The weighted first moment, which is equal to the average Doppler shift, shows a linear response for different mean flow velocities within the physiological range.

  15. Effective lactation yield: A measure to compare milk yield between cows with different dry period lengths.

    Science.gov (United States)

    Kok, A; van Middelaar, C E; Engel, B; van Knegsel, A T M; Hogeveen, H; Kemp, B; de Boer, I J M

    2016-04-01

    To compare milk yields between cows or management strategies, lactations are traditionally standardized to 305-d yields. The 305-d yield, however, gives no insight into the combined effect of additional milk yield before calving, decreased milk yield after calving, and a possible shorter calving interval in the case of a shortened dry period. We aimed to develop a measure that would enable the comparison of milk yield between cows with different dry period (DP) lengths. We assessed the importance of accounting for additional milk yield before calving and for differences in calving interval. The 305-d yield was compared with a 365-d yield, which included additional milk yield in the 60 d before calving. Next, an effective lactation yield was computed, defined as the daily yield from 60d before calving to 60 d before the next calving, to account for additional milk yield before calving and for differences in calving interval. Test-day records and drying-off dates of 15 commercial farms were used to compute the 305-d, 365-d, and effective lactation yields for individual cows. We analyzed 817 second-parity lactations preceded by no DP, a short DP (20 to 40 d), or a conventional DP (49 to 90 d). Compared with cows with a conventional DP, the 305-d yield of cows with no DP was 7.0 kg of fat- and protein-corrected milk (FPCM) per day lower, and the 305-d yield of cows with a short DP was 2.3 kg of FPCM per day lower. Including additional milk yield before calving in the 365-d yield reduced this difference to 3.4 kg of FPCM per cow per day for cows with no DP and to 0.9 kg of FPCM per cow per day for cows with a short DP. Compared with cows with a conventional DP, median days open were reduced by 25d for cows with no DP and by 18d for cows with a short DP. Accounting for these differences in calving interval in the effective lactation yield further decreased yield reductions for cows with no DP or a short DP by 0.3 kg of FPCM per cow per day. At the herd level, estimated

  16. How Does Definition of Minimum Break Length Affect Objective Measures of Sitting Outcomes Among Office Workers?

    Science.gov (United States)

    Kloster, Stine; Danquah, Ida Høgstedt; Holtermann, Andreas; Aadahl, Mette; Tolstrup, Janne Schurmann

    2017-01-01

    Harmful health effects associated with sedentary behavior may be attenuated by breaking up long periods of sitting by standing or walking. However, studies assess interruptions in sitting time differently, making comparisons between studies difficult. It has not previously been described how the definition of minimum break duration affects sitting outcomes. Therefore, the aim was to address how definitions of break length affect total sitting time, number of sit-to-stand transitions, prolonged sitting periods and time accumulated in prolonged sitting periods among office workers. Data were collected from 317 office workers. Thigh position was assessed with an ActiGraph GT3X+ fixed on the right thigh. Data were exported with varying bout length of breaks. Afterward, sitting outcomes were calculated for the respective break lengths. Absolute numbers of sit-to-stand transitions decreased, and number of prolonged sitting periods and total time accumulated in prolonged sitting periods increased, with increasing minimum break length. Total sitting time was not influenced by varying break length. The definition of minimum break length influenced the sitting outcomes with the exception of total sitting time. A standard definition of break length is needed for comparison and interpretation of studies in the evolving research field of sedentary behavior.

  17. Measurement of the optical path length difference in an interferometer using a sinusoidally frequency-modulated light source.

    Science.gov (United States)

    Shimada, Shumpei; Shizuka, Makoto; Hayashi, Neisei; Mizuno, Yosuke; Nakamura, Kentaro

    2016-04-10

    We develop a technique for measuring the optical path length difference (OPLD) in an interferometer using a frequency-modulated light source. Compared with conventional methods, this technique offers a high sampling rate, high precision, and cost efficiency, and is capable of determining which of the two optical paths is longer. In addition, we show that this technique works properly even when the OPLD is significantly longer than the coherence length of the light source.

  18. Interpretation of Core Length in Shear Coaxial Rocket Injectors from X-ray Radiography Measurements (Briefing Charts)

    Science.gov (United States)

    2014-06-01

    Used to study diesel, swirl , gas-centered swirl -coaxial, impingers, and aerated liquid jet injectors • Use a monochromatic beam of X-rays...the shear between an outer lower-density high-velocity annulus and a higher-density low-velocity inner jet to atomize and mix a liquid and a gas...radiography data and are compared to two-phase core length measurements from the literature. The core length nondimensionalized by the inner jet diameter

  19. Effects of voxel size and resolution on the accuracy of endodontic length measurement using cone beam computed tomography.

    Science.gov (United States)

    Aktan, Ali Murat; Yildirim, Cihan; Karataşlıoğlu, Emrah; Çiftçi, Mehmet Ertuğrul; Aksoy, Fatih

    2016-11-01

    An accurate determination of the working length is indispensable for successful endodontic treatment. The aim of this study was to determine the influence of the voxel size and resolution of CBCT on measuring root canal working length. Thirty extracted single-rooted permanent teeth were used for this study. The working lengths of the teeth were determined by a researcher inserted a K-file into each canal until the tip became visible through the major foramen. The file was withdrawn until its tip was seen at the level of the coronal-most border of the major foramen under. The rubber stop was adjusted to the occlusal reference and the distance from the stop to the false tip was measured with digital calipers and recorded as the actual working length. The CBCT images were obtained with a Planmeca ProMax 3D Mid (Planmeca, Helsinki, Finland) using four sets of settings: from voxel size 0.5mm to voxel size 1.0mm. These measurements were compared with actual lengths (as a control group) using Analysis of Variance and the Dunnett Post Hoc Test. The Pearson correlation coefficient (r) and 95% confidence intervals were calculated to compare all measurement methods. The significance level was set at Plength. A highest correlation was found between the actual length and smallest voxel size and highest CBCT measurements (r=0.94). CBCT imaging can be used endodontic working length measurement and the smallest voxel size and highest resolution yielded more accurate results. Copyright © 2016 Elsevier GmbH. All rights reserved.

  20. Effect of different levels of sharpness processing filter on the measurement accuracy of endodontic file length

    National Research Council Canada - National Science Library

    Nastaran Farhadi; Ali Shokraneh; Masoud Saatchi

    2016-01-01

      Introduction: The present study was undertaken to evaluate the effect of different levels of sharpness processing filter on the accuracy of endodontic file length determination using digital periapical radiography...

  1. Disentangling behavior in early child development : Interpretability of early child language and its effect on utterance length measures

    NARCIS (Netherlands)

    Van Dijk, M.W.G.; Van Geert, P. L. C.

    Early child speech is often difficult to understand and interpret. Usually, these unintelligible units are not included in quantitative measures, such as MLU. In this paper, we claim that these interpretation problems have an unknown effect on utterance length measures (such as MLU), since we have

  2. Fetal liver length measurement at mid-pregnancy among fetuses at risk as a predictor of hemoglobin Bart's disease.

    Science.gov (United States)

    Luewan, S; Tongprasert, F; Piyamongkol, W; Wanapirak, C; Tongsong, T

    2011-03-01

    To assess the effectiveness of liver length measurement in predicting hemoglobin (Hb) Bart's disease among fetuses at risk at mid-pregnancy. Pregnant women at risk of fetal Hb Bart's disease at 18 to 22 weeks of gestation were enrolled in the study. All of them underwent liver length measurement just before cordocentesis for fetal blood analysis. The final diagnosis used as a gold standard was based on fetal Hb typing using high-performance liquid chromatography. A total of 334 pregnant women were recruited into the study. The prevalence of fetal Hb Bart's disease was 26.1% (87 of 334 fetuses). The sensitivity, specificity, as well as positive and negative predictive values of liver length in the prediction of affected fetuses were 71.3, 95.5, 84.9 and 90.4%, respectively. Overall, 24 fetuses (27.6%) had some degree of early hydrops fetalis. Of these, 20 had hepatomegaly as well. Liver length measurements at mid-pregnancy may be helpful in predicting affected fetuses among pregnancies at risk. Normal liver length measurement is associated with a very low risk of the disease. This information may help couples decide on whether to opt for either invasive diagnosis or a noninvasive approach, especially when used as an adjunct to other tests.

  3. Generating ultrarelativistic attosecond electron bunches with laser wakefield accelerators

    NARCIS (Netherlands)

    Luttikhof, M.J.H.; Khachatryan, A.G.; van Goor, F.A.; Boller, Klaus J.

    2010-01-01

    Femtosecond electron bunches with ultrarelativistic energies were recently generated by laser wakefield accelerators. Here we predict that laser wakefield acceleration can generate even attosecond bunches, due to a strong chirp of the betatron frequency. We show how the bunch duration scales with

  4. Electron bunch injection at an angle into a laser wakefield

    NARCIS (Netherlands)

    Luttikhof, M.J.H.; Khachatryan, A.G.; van Goor, F.A.; Boller, Klaus J.; Mora, P.

    2009-01-01

    External injection of electron bunches longer than the plasma wavelength in a laser wakefield accelerator can lead to the generation of femtosecond ultra relativistic bunches with a couple of percent energy spread. Extensive study has been done on external electron bunch (e.g., one generated by a

  5. An improved injector bunching geometry for ATLAS

    Indian Academy of Sciences (India)

    Abstract. The bunching system of the ATLAS positive ion injector (PII) has been improved by relocating the harmonic buncher to a point significantly closer to the second stage sine-wave buncher and the injector LINAC. The longitudinal optics design has also been modified and now employs a virtual waist from the ...

  6. An improved injector bunching geometry for ATLAS

    Indian Academy of Sciences (India)

    The bunching system of the ATLAS positive ion injector (PII) has been improved by relocating the harmonic buncher to a point significantly closer to the second stage sine-wave buncher and the injector LINAC. The longitudinal optics design has also been modified and now employs a virtual waist from the harmonic buncher ...

  7. Multi-Bunch Longitudinal Dynamics and Diagnostics via a Digital Feedback System at PEP-II, DAFNE, ALS and SPEAR

    Energy Technology Data Exchange (ETDEWEB)

    Fox, John D

    1999-04-19

    A bunch-by-bunch longitudinal feedback system based on a programmable DSP architecture is used to study coupled-bunch motion and its sources. Experimental results are presented from PEP-II, DA{Phi}NE, ALS and SPEAR to highlight the operational experience from 4 installations, plus show novel accelerator diagnostics possible with the digital processing system. Modal growth and damping rates are measured via short (20 ms) transient recordings for unstable and stable coupled-bunch modes. Data from steady-state measurements are used to identify unstable modes and noise-driven beam motion. A novel impedance measurement technique is presented which reveals the longitudinal impedance as a function of frequency. This technique uses the measured synchronous phase and charge of every bucket to calculate the impedance seen by the beam at revolution harmonics.

  8. Dancing bunches as Van Kampen modes

    Energy Technology Data Exchange (ETDEWEB)

    Burov, A.; /Fermilab

    2011-03-01

    Van Kampen modes are eigen-modes of Jeans-Vlasov equation [1-3]. Their spectrum consists of continuous and, possibly, discrete parts. Onset of a discrete van Kampen mode means emergence of a coherent mode without any Landau damping; thus, even a tiny couple-bunch wake is sufficient to drive instability. Longitudinal instabilities observed at Tevatron [4], RHIC [5] and SPS [6] can be explained as loss of Landau damping (LLD), which is shown here to happen at fairly low impedances. For repulsive wakes and single-harmonic RF, LLD is found to be extremely sensitive to steepness of the bunch distribution function at small amplitudes. Based on that, a method of beam stabilization is suggested. Emergence of a discrete van Kampen mode means either loss of Landau damping or instability. Longitudinal bunch stability is analysed in weak head-tail approximation for inductive impedance and single-harmonic RF. The LLD threshold intensities are found to be rather low: for cases under study all of them do not exceed a few percent of the zero-amplitude incoherent synchrotron frequency shift, strongly decreasing for shorter bunches. Because of that, LLD can explain longitudinal instabilities happened at fairly low impedances at Tevatron [4], and possibly for RHIC [5] and SPS [6], being in that sense an alternative to the soliton explanation [5, 20]. Although LLD itself results in many cases in emergence of a mode with zero growth rate, any couple-bunch (and sometimes multi-turn) wake would drive instability for that mode, however small this wake is. LLD is similar to a loss of immune system of a living cell, when any microbe becomes fatal for it. The emerging discrete mode is normally very different from the rigid-bunch motion; thus the rigid-mode model significantly overestimates the LLD threshold. The power low of LLD predicted in Ref. [17] agrees with results of this paper. However, the numerical factor in that scaling low strongly depends on the bunch distribution function

  9. Standard practice for measuring the change in length of fasteners using the ultrasonic pulse-echo technique

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2000-01-01

    1.1 This practice covers a procedure for measuring changes in length of threaded fasteners using conventional ultrasonic pulse-echo bolt-measuring instrumentation which has been properly calibrated. 1.2 This procedure is normally intended for metal bolting 0.25 in. (6.4 mm) or more in nominal diameter with effective length-to-diameter ratios of 2:1 or greater. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  10. Spectral reflectance analysis of longkong (Lansium domesticum Corr. bunches as an indicator for optimal harvesting

    Directory of Open Access Journals (Sweden)

    Kaewtubtim, P.

    2007-09-01

    Full Text Available To determine the appropriate harvesting time of Longkong bunches, the spectral reflectance of ripening bunches was investigated from images taken by a digital camera using red LED and green LED. Every day images were taken from selected bunches at a Longkong estate during the growth of the bunches from immaturity to the over-ripe phase, to trace the changes in color that correlate with the process of ripening. The images were analyzed by measuring the changes in the three basic colors i.e. red, green and blue, using a specially developed Color Analysis computer program of Longkong "fruit" (CAOL, and then the obtained results were compared with the sweet in form of total soluble solid (TSS:TA.The result showed that the blue light reflectance from red LED source (Br was selected as an indicator for harvesting Longkong bunches. Br was inversely proportional to ripeness of Longkong. The blue color intensity decreases linearly while TSS:TA increases monotonously. From our investigations, we suggest that the time interval to harvest Longkong should be within 96 ±7 days after the first flower blossom of that bunch takes place while blue level per pixel was in the range of 8.67-2.39. If Longkong bunch was cut while the blue color level was in the range of 8.67-5.53, its taste will be sweet and sour and strong enough for long distance shipment. But if the blue level per pixel was in the range of 5.52-2.39, it has a very good taste and is suitable a for sale in the local area. In addition, it was also found that the blue level per pixel usually decreased at the rate of 0.45 per day. This made is possible to predict the harvesting day by this technique.

  11. 'Length'at Length

    Indian Academy of Sciences (India)

    Admin

    Translation invariance, axiom of choice, continuum hypothesis, axiom of determinateness. B V Rao was a Professor at the Indian Statistical. Institute, Kolkata. Currently he is with the. Chennai Mathematical. Institute. This is the story of length, one of the simplest concepts. Starting with the concept of length for intervals, we ...

  12. Measuring the primary cilium length: improved method for unbiased high‑throughput analysis

    NARCIS (Netherlands)

    Dummer, A; Poelma, C.; DeRuiter, MC; Goumans, M-J TH; Hierck, BP

    2016-01-01

    Background
    Primary cilia are cellular protrusions involved in mechanic and chemical sensing on almost all cells of our body. Important signaling pathways, including Hedgehog, TGFβ, and Ca2+, are linked to cilia and/or cilia function. Cilia can vary in length, which has functional implications.

  13. Importance of epoch length and registration time on accelerometer measurements in younger children

    DEFF Research Database (Denmark)

    Dencker, M; Svensson, J; El-Naaman, B

    2012-01-01

    The aim of this study was to investigate the effect of epoch length on accumulation of minutes of physical activity per day over a spectrum of intensities, and the effect that selection of number of hours of acceptable registration required per day had on number of days that were considered...

  14. Improved theory of time domain reflectometry with variable coaxial cable length for electrical conductivity measurements

    Science.gov (United States)

    Although empirical models have been developed previously, a mechanistic model is needed for estimating electrical conductivity (EC) using time domain reflectometry (TDR) with variable lengths of coaxial cable. The goals of this study are to: (1) derive a mechanistic model based on multisection tra...

  15. High angle phase modulated low coherence interferometry for path length resolved Doppler measurements of multiply scattered light

    Science.gov (United States)

    Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G.; Steenbergen, Wiendelt

    2008-02-01

    We describe an improved method for coherence domain path length resolved measurements of multiply scattered photons in turbid media. An electro-optic phase modulator sinusoidally modulates the phase in the reference arm of a low coherence fiber optic Mach-Zehnder interferometer, at a high phase modulation angle. For dynamic turbid media this results in Doppler broadened phase modulation interference peaks at the modulation frequency and its multiples. The signal to noise ratio is increased by almost one order or magnitude for large modulation angles and the shape of the spectral peaks resulting from the interference of Doppler shifted sample waves and reference light is not changed. The path length dependent Doppler broadening is compared with the theoretical predictions in the single scattered and diffusive regimes. The experimentally measured optical path lengths are validated with the Monte Carlo technique.

  16. Improved ramped bunch train to increase the transformer ratio of a two-channel multimode dielectric wakefield accelerator

    Directory of Open Access Journals (Sweden)

    G. V. Sotnikov

    2011-03-01

    Full Text Available Here we show a possibility of applying the ramped drive bunch train (RBT technique to a two-channel coaxial dielectric wakefield accelerator (CDWA. For numerical research we study a 28 GHz structure with two nested alumina cylindrical shells having these diameters: outer shell, OD=28.1  mm, ID=27  mm; inner shell, OD=6.35  mm, ID=4.0  mm. The structure is to be excited by a train of four annular bunches having energy 14 MeV and axial rms length 1 mm; the total charge of bunches is 200 nC. In the case of equally charged drive bunches, spaced apart by the principal wakefield wavelength 10.67 mm, we obtained transformer ratio T=3.4. If the bunch charge is increasing as the ratio 1∶3∶5∶7 and the bunches are spaced by one and one-half wavelengths, we obtained T=3.8. We found that if the charge ratios are 1.0∶2.4∶3.5∶5.0 and the spaces between the bunches are 2.5, 2.5, and 4.5 wakefield periods, then T increases strongly, T∼20. The RBT also can be used successfully in a high gradient THz CDWA structure. A particle-in-cell simulation shows that the four drive bunches can move without appreciable distortion.

  17. Direct observation of beam bunching in BWO experiments

    CERN Document Server

    Morimoto, I; Maebara, S; Kishiro, J; Takayama, K; Horioka, K; Ishizuka, H; Kawasaki, S; Shiho, M

    2001-01-01

    Backward Wave Oscillation (BWO) experiments using a Large current Accelerator-1 (Lax-1) Induction Linac as a seed power source for an mm-wave FEL are under way. The Lax-1 is typically operated with a 1 MeV electron beam, a few kA of beam current, and a pulse length of 100 ns. In the BWO experiments, annular and solid beams are injected into a corrugated wave guide with guiding axial magnetic field of 1 T. In the BWO with annular beam an output power of 210 MW at 9.8 GHz was obtained. With a solid beam the output power was 130 MW, and an electron beam bunching with the frequency of 9.6-10.2 GHz was observed by a streak camera.

  18. Effects of the Passive Harmonic Cavity on the Beam Bunch

    CERN Document Server

    Chang Lung Hai; Wang, Chaoen; Yeh, Meng-Shu

    2005-01-01

    In this paper, we present a computer tracking code, which can investigate the bunch length, energy spread and the critical current of Robinson instability under the influence of the passive harmonic cavity. The effects of the radiation damping, quantum excitation and the beam loading of the harmonic cavity are included in the computation. The calculated result shows that the beam has a constant energy spread and blows up as the beam current increases from below to over the threshold current of the Robinson instability. It also indicates that the shunt impedance of the harmonic cavity is critical for whether the harmonic cavity can reach the designed goal, a stable and lengthening beam at the design beam current.

  19. Analytical Formulas for Short Bunch Wakes in a Flat Dechirper

    Energy Technology Data Exchange (ETDEWEB)

    Bane, Karl [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stupakov, Gennady [SLAC National Accelerator Lab., Menlo Park, CA (United States); Zagorodnov, Igor [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2016-03-29

    We develop analytical models of the longitudinal and transverse wakes, on and off axis for realistic structures, and then compare them with numerical calculations, and generally find good agreement. These analytical "first order" formulas approximate the droop at the origin of the longitudinal wake and of the slope of the transverse wakes; they represent an improvement in accuracy over earlier, "zeroth order" formulas. In example calculations for the RadiaBeam/LCLS dechirper using typical parameters, we find a 16% droop in the energy chirp at the bunch tail compared to simpler calculations. With the beam moved to 200 m from one jaw in one dechiper section, one can achieve a 3 MV transverse kick differential over a 30 m length.

  20. High angle phase modulated low coherence interferometry for path length resolved Doppler measurements of multiply scattered light

    NARCIS (Netherlands)

    Varghese, Babu; Rajan, Vinayakrishnan; van Leeuwen, Ton; Steenbergen, Wiendelt

    2008-01-01

    We describe an improved method for coherence domain path length resolved measurements of multiply scattered photons in turbid media. An electro-optic phase modulator sinusoidally modulates the phase in the reference arm of a low coherence fiber optic Mach–Zehnder interferometer, at a high phase

  1. Influence of Landscape Coverage on Measuring Spatial and Length Properties of Rock Fracture Networks: Insights from Numerical Simulation

    Science.gov (United States)

    Cao, Wenzhuo; Lei, Qinghua

    2018-01-01

    Natural fractures are ubiquitous in the Earth's crust and often deeply buried in the subsurface. Due to the difficulty in accessing to their three-dimensional structures, the study of fracture network geometry is usually achieved by sampling two-dimensional (2D) exposures at the Earth's surface through outcrop mapping or aerial photograph techniques. However, the measurement results can be considerably affected by the coverage of forests and other plant species over the exposed fracture patterns. We quantitatively study such effects using numerical simulation. We consider the scenario of nominally isotropic natural fracture systems and represent them using 2D discrete fracture network models governed by fractal and length scaling parameters. The groundcover is modelled as random patches superimposing onto the 2D fracture patterns. The effects of localisation and total coverage of landscape patches are further investigated. The fractal dimension and length exponent of the covered fracture networks are measured and compared with those of the original non-covered patterns. The results show that the measured length exponent increases with the reduced localisation and increased coverage of landscape patches, which is more evident for networks dominated by very large fractures (i.e. small underlying length exponent). However, the landscape coverage seems to have a minor impact on the fractal dimension measurement. The research findings of this paper have important implications for field survey and statistical analysis of geological systems.

  2. Complex soliton bunching patterns induced by nonsaturable absorption

    Science.gov (United States)

    Chen, Weicheng; Luo, Aiping

    2017-10-01

    A fiber laser with a semiconductor saturable absorption mirror (SESAM) and a graphene-polymer composite (GPC) film is constructed for achieving different soliton bunching patterns. The SESAM is used as a mode locker for self-started pulse generation, while the GPC provides a nonsaturable absorption effect for achieving a bunching in the laser cavity. There are three extra temporal patterns observed in the experiments through adjusting polarization controllers. They are chaotic bunching, weak coherent bunching and modulated harmonic bunching. The experimental investigation shows that dynamic nonsaturable absorption effect of an absorber is beneficial for generating different bunching patterns. Our work can have a deeper understanding of the formation of the complex soliton bunching patterns in pulsed lasers.

  3. Measurements of 3D slip velocities and plasma column lengths of a gliding arc discharge

    DEFF Research Database (Denmark)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas

    2015-01-01

    A non-thermal gliding arc discharge was generated at atmospheric pressure in an air flow. The dynamics of the plasma column and tracer particles were recorded using two synchronized high-speed cameras. Whereas the data analysis for such systems has previously been performed in 2D (analyzing...... the single camera image), we provide here a 3D data analysis that includes 3D reconstructions of the plasma column and 3D particle tracking velocimetry based on discrete tomography methods. The 3D analysis, in particular, the determination of the 3D slip velocity between the plasma column and the gas flow......, gives more realistic insight into the convection cooling process. Additionally, with the determination of the 3D slip velocity and the 3D length of the plasma column, we give more accurate estimates for the drag force, the electric field strength, the power per unit length, and the radius...

  4. Effect of source/sink ratios on yield components, growth dynamics and structural characteristics of oil palm (Elaeis guineensis) bunches.

    Science.gov (United States)

    Pallas, Benoît; Mialet-Serra, Isabelle; Rouan, Lauriane; Clément-Vidal, Anne; Caliman, Jean-Pierre; Dingkuhn, Michael

    2013-04-01

    Source/sink ratios are known to be one of the main determinants of oil palm growth and development. A long-term experiment (9 years) was conducted in Indonesia on mature oil palms subjected to continuous bunch ablation and partial defoliation treatments to artificially modify source/sink ratios. During the experiment, all harvested bunches were dissected and phenological measurements were carried out to analyse the effect of source/sink ratios on yield components explaining variations in bunch number, the number of fruits per bunch and oil dry weight per fruit. An integrative variable (supply/demand ratio) describing the ratio between the assimilate supply from sources and the growing organ demand for carbohydrate was computed for each plant on a daily basis from observations of the number of developing organs and their sink strength, and of climate variables. Defoliation and bunch ablation affected the bunch number and the fruit number per bunch. Variations in bunch number per month were mainly due to variations in the fraction of aborted inflorescence and in the ratio between female and male inflorescences. Under fluctuating trophic conditions, variations in fruit number per bunch resulted both from changes in fruit-set and in the number of branches (rachillae) per inflorescence. For defoliated plants, the decrease in the number of developing reproductive sinks appeared to be sufficient to maintain fruit weight and oil concentration at the control level, without any major decrease in the concentration of non-structural carbohydrate reserves. Computation of the supply/demand ratio revealed that each yield component had a specific phase of sensitivity to supply/demand ratios during inflorescence development. Establishing quantitative relationships between supply/demand ratios, competition and yield components is the first step towards a functional model for oil palm.

  5. Theoretical analysis and simulation of the influence of self-bunching effects and longitudinal space charge effects on the propagation of keV electron bunch produced by a novel S-band Micro-Pulse electron Gun

    Directory of Open Access Journals (Sweden)

    Jifei Zhao

    2016-06-01

    Full Text Available As an important electron source, Micro-Pulse electron Gun (MPG which is qualified for producing high average current, short pulse, low emittance electron bunches steadily holds promise to use as an electron source of Coherent Smith-Purcell Radiation (CSPR, Free Electron Laser (FEL. The stable output of S-band MPG has been achieved in many labs. To establish reliable foundation for the future application of it, the propagation of picosecond electron bunch produced by MPG should be studied in detail. In this article, the MPG which was working on the rising stage of total effective Secondary Electron Yield (SEY curve was introduced. The self-bunching mechanism was discussed in depth both in the multipacting amplifying state and the steady working state. The bunch length broadening induced by the longitudinal space-charge (SC effects was investigated by different theoretical models in different regions. The 2D PIC codes MAGIC and beam dynamic codes TraceWin simulations were also performed in the propagation. The result shows an excellent agreement between the simulation and the theoretical analysis for bunch length evolution.

  6. DSP and FPGA Based Bunch Current Signal Processing

    CERN Document Server

    Naylor, G A

    2001-01-01

    The current in electron storage rings used as synchrotron light sources must be measured to a very high precision in order to determine the stored beam lifetime. This is especially so in high-energy machines in which the lifetime may be very high. Parametric current transformers (PCT) have traditionally been used to measure the DC or average current in the machine, which offer a very high resolution. Unfortunately these do not allow the different components of a complex filling pattern to be measured separately. A hybrid filling mode delivered at the ESRF consists of one third of the ring filled with bunches with a single highly populated bunch in the middle of the two-thirds gap. The lifetime of these two components may be very different. Similarly the two components are injected separately and can be monitored separately using a fast current transformer (FCT) or an integrating current transformer (ICT). The signals from these devices can be analysed using high speed analogue to digital converters operating ...

  7. Fast digital transverse feedback system for bunch train operation in CESR

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, J.T.; Billing, M.G.; Dobbins, J.A. [Cornell Univ., Ithaca, NY (United States). Lab. of Nuclear Studies] [and others

    1996-08-01

    We have developed a time domain transverse feedback system with the high bandwidth needed to control transverse instabilities when the CESR e{sup +}e{sup -} collider is filled with trains of closely spaced bunches. This system is based on parallel digital processors and a stripline driver. It is capable of acting on arbitrary patterns of bunches having a minimum spacing of 14 ns. Several simplifying features have been introduced. A single shorted stripline kicker driven by one power amplifier is used to control both counter-rotating beams. The desired feedback phase is achieved by sampling the bunch position at a single location on two independently selectable beam revolutions. The system adapts to changes in the betatron tune, bunch pattern, or desired damping rate through the loading of new parameters into the digital processors via the CESR control system. The feedback system also functions as a fast gated bunch current monitor. Both vertical and horizontal loops are now used in CESR operation. The measured betatron damping rates with the transverse feedback system in operation are in agreement with the analytical prediction and a computer simulation developed in connection with this work. (author)

  8. ''High intensity per bunch'' working group

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-07-01

    Third Generation Light Sources are supposed to store high intensity beams not only in many tightly spaced bunches (multibunch operation), but also in few bunch or even single lunch modes of operation, required for example for time structure experiments. Single bunch instabilities, driven by short-range wake fields, however spoil the beam quality, both longitudinally and transversely. Straightforward ways of handling them, by pushing up the chromaticity ({zeta} = {delta}Q/({delta}p/p)) for example, enabled to raise the charge per bunch, but to the detriment of beam lifetime. In addition, since the impedance of the vacuum chamber deteriorates with the installation of new insertion devices, the current thresholds tend to dope down continuously. The goal of this Working Group was then to review these limitations in the existing storage rings, where a large number of beam measurements have been performed to characterise them, and to discuss different strategies which are used against them. About 15 different laboratories reported on the present performance of storage rings, experiences gained in high charge per bunch, and on simulation results and theoretical studies. More than 25 presentations addressed the critical issues and stimulated the discussion. Four main topics came out: - Observation and experimental data; - Impedance studies and tracking codes; - Theoretical investigations; - Cures and feedback. (author)

  9. Coherent synchrotron radiation and bunch stability in a compact storage ring

    Directory of Open Access Journals (Sweden)

    Marco Venturini

    2005-01-01

    Full Text Available We examine the effect of the collective force due to coherent synchrotron radiation (CSR in an electron storage ring with small bending radius. In a computation based on time-domain integration of the nonlinear Vlasov equation, we find the threshold current for a longitudinal microwave instability induced by CSR alone. The model accounts for suppression of radiation at long wavelengths due to shielding by the vacuum chamber. In a calculation just above threshold, small ripples in the charge distribution build up over a fraction of a synchrotron period, but then die out to yield a relatively smooth but altered distribution with eventual oscillations in bunch length. The instability evolves from small noise on an initial smooth bunch of rms length much greater than the shielding cutoff.

  10. Simultaneous Water Vapor and Dry Air Optical Path Length Measurements and Compensation with the Large Binocular Telescope Interferometer

    Science.gov (United States)

    Defrere, D.; Hinz, P.; Downey, E.; Boehm, M.; Danchi, W. C.; Durney, O.; Ertel, S.; Hill, J. M.; Hoffmann, W. F.; Mennesson, B.; hide

    2016-01-01

    The Large Binocular Telescope Interferometer uses a near-infrared camera to measure the optical path length variations between the two AO-corrected apertures and provide high-angular resolution observations for all its science channels (1.5-13 microns). There is however a wavelength dependent component to the atmospheric turbulence, which can introduce optical path length errors when observing at a wavelength different from that of the fringe sensing camera. Water vapor in particular is highly dispersive and its effect must be taken into account for high-precision infrared interferometric observations as described previously for VLTI/MIDI or the Keck Interferometer Nuller. In this paper, we describe the new sensing approach that has been developed at the LBT to measure and monitor the optical path length fluctuations due to dry air and water vapor separately. After reviewing the current performance of the system for dry air seeing compensation, we present simultaneous H-, K-, and N-band observations that illustrate the feasibility of our feed forward approach to stabilize the path length fluctuations seen by the LBTI nuller uses a near-infrared camera to measure the optical path length variations between the two AO-corrected apertures and provide high-angular resolution observations for all its science channels (1.5-13 microns). There is however a wavelength dependent component to the atmospheric turbulence, which can introduce optical path length errors when observing at a wavelength different from that of the fringe sensing camera. Water vapor in particular is highly dispersive and its effect must be taken into account for high-precision infrared interferometric observations as described previously for VLTI MIDI or the Keck Interferometer Nuller. In this paper, we describe the new sensing approach that has been developed at the LBT to measure and monitor the optical path length fluctuations due to dry air and water vapor separately. After reviewing the current

  11. Observation of Bunching of Two Bell States

    Science.gov (United States)

    Eisenberg, H. S.; Hodelin, J. F.; Khoury, G.; Bouwmeester, D.

    2006-04-01

    The bunching of two single photons on a beam splitter is a fundamental quantum effect, first observed by Hong, Ou, and Mandel. It is a unique interference effect that relies only on the photons’ indistinguishability and not on their relative phase. We generalize this effect by demonstrating the bunching of two Bell states, created in two passes of a nonlinear crystal, each composed of two photons. When the two Bell states are indistinguishable, phase-insensitive destructive interference prevents the outcome of fourfold coincidence between the four spatial-polarization modes. For certain combinations of the two Bell states, we demonstrate the opposite effect of antibunching. We relate this result to the number of distinguishable modes in parametric down-conversion.

  12. In vivo accuracy of three electronic root canal length measurement devices: Dentaport ZX, Raypex 5 and ProPex II.

    Science.gov (United States)

    Somma, F; Castagnola, R; Lajolo, C; Paternò Holtzman, L; Marigo, L

    2012-06-01

    To compare in vivo three different electronic root canal length measurement devices: Dentaport ZX, Raypex 5 and ProPex II. Thirty single-rooted permanent teeth scheduled for extraction because of periodontal disease were selected from 10 adult patients (ranging from 45 to 67 years) and divided into three groups of 10 teeth. Before the extraction, an access cavity was prepared and the crown was adjusted to establish a stable reference point for all measurements. The working length in Group 1 was determined using the Dentaport ZX apex locator. A K-file with the largest diameter that could reach the last green bar on the screen was stabilized in the canal using a dual-curable flow resin composite. The same procedure was used for the Raypex 5 (the file reached the last yellow bar) and Propex II (0.0 orange bar) apex locators. The teeth were then extracted and cleared. The distance between the tip of the file and the major foramen was then calculated for each tooth using digital photography according to Axiovision AC software (Carl Zeiss). Positive values were assigned when the file tip passed beyond the major foramen, negative values when the tip was short of the foramen and zero value when the file tip and the foramen coincided. Statistical analysis was performed using the chi-squared test or Fisher's exact test (P ≤ 0.05).   Dentaport ZX, Raypex 5 and ProPex ΙΙ produced, respectively, 6, 2 and 4 out of 10 correct measurements, 0, 6 and 5 long measurements and 4, 2, and 1 short measurements. The differences between the three electronic root canal length measurement devices were not significant (P = 0.507). Under the in vivo conditions of this study, the three electronic root canal length measurement devices were not significantly different in terms of locating the major foramen. © 2012 International Endodontic Journal.

  13. Length and volume of morphologically normal kidneys in Korean Children: Ultrasound measurement and estimation using body size

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jun Hwee; Kim, Myung Joon; Lim, Sok Hwan; Lee, Mi Jung [Dept. of Radiology and Research Institute of Radiological Science, Severance Children' s Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of); Kim, Ji Eun [Biostatistics Collaboration Unit, Yonsei University College of Medicine, Seoul (Korea, Republic of)

    2013-08-15

    To evaluate the relationship between anthropometric measurements and renal length and volume measured with ultrasound in Korean children who have morphologically normal kidneys, and to create simple equations to estimate the renal sizes using the anthropometric measurements. We examined 794 Korean children under 18 years of age including a total of 394 boys and 400 girls without renal problems. The maximum renal length (L) (cm), orthogonal anterior-posterior diameter (D) (cm) and width (W) (cm) of each kidney were measured on ultrasound. Kidney volume was calculated as 0.523 x L x D x W (cm{sup 3}). Anthropometric indices including height (cm), weight (kg) and body mass index (m{sup 2}/kg) were collected through a medical record review. We used linear regression analysis to create simple equations to estimate the renal length and the volume with those anthropometric indices that were mostly correlated with the US-measured renal sizes. Renal length showed the strongest significant correlation with patient height (R2, 0.874 and 0.875 for the right and left kidneys, respectively, p < 0.001). Renal volume showed the strongest significant correlation with patient weight (R2, 0.842 and 0.854 for the right and left kidneys, respectively, p < 0.001). The following equations were developed to describe these relationships with an estimated 95% range of renal length and volume (R2, 0.826-0.884, p < 0.001): renal length = 2.383 + 0.045 x Height (± 1.135) and = 2.374 + 0.047 x Height (± 1.173) for the right and left kidneys, respectively; and renal volume 7.941 + 1.246 x Weight (± 15.920) and = 7.303 + 1.532 x Weight (± 18.704) for the right and left kidneys, respectively. Scatter plots between height and renal length and between weight and renal volume have been established from Korean children and simple equations between them have been developed for use in clinical practice.

  14. Measurement of the magneto-optical correlation length in turbid media.

    Science.gov (United States)

    Lenke, Ralf; Eisenmann, Christoph; Reinke, Daniel; Maret, Georg

    2002-11-01

    In multiple light scattering media, magnetic field induced circular birefringence (Faraday effect) influences interference effects such as speckle pattern or coherent backscattering. It was predicted that in the diffusive regime the relevant correlation length with respect to the Faraday rotation l( small star, filled )(F) differs, in general, from the transport mean free path l( small star, filled ). We have experimentally verified the prediction that the ratio l( small star, filled )(F)/l( small star, filled ) equals 2 for Rayleigh scattering and decreases to 1 with increasing scatterer size. We also discuss the influence of the structure factor on l( small star, filled )(F).

  15. Extremely short relativistic-electron-bunch generation in the laser wakefield via novel bunch injection scheme

    Directory of Open Access Journals (Sweden)

    A. G. Khachatryan

    2004-12-01

    Full Text Available Recently a new electron-bunch injection scheme for the laser wakefield accelerator has been proposed [JETP Lett. 74, 371 (2001JTPLA20021-364010.1134/1.1427124; Phys. Rev. E 65, 046504 (2002PLEEE81063-651X10.1103/PhysRevE.65.046504]. In this scheme, a low energy electron bunch, sent in a plasma channel just before a high-intensity laser pulse, is trapped in the laser wakefield, considerably compressed and accelerated to an ultrarelativistic energy. In this paper we show the possibility of the generation of an extremely short (on the order of 1   μm long or a few femtoseconds in duration relativistic-electron-bunch by this mechanism. The initial electron bunch, which can be generated, for example, by a laser-driven photocathode rf gun, should have an energy of a few hundred keVs to a few MeVs, a duration in the picosecond range or less and a relatively low concentration. The trapping conditions and parameters of an accelerated bunch are investigated. The laser pulse dynamics as well as a possible experimental setup for the demonstration of the injection scheme are also considered.

  16. Anelamento e reguladores de crescimento: efeitos sobre as medidas biométricas e qualidade de cachos da videira 'Superior Seedless' Girdling and growth regulators: effects on the biometric measurements and quality of bunches of vine 'Superior Sedless'

    Directory of Open Access Journals (Sweden)

    Patrícia Coelho de Souza Leão

    2004-12-01

    Full Text Available Com o objetivo de se obter maior tamanho de baga, peso médio de cacho e produtividade, os cachos da variedade Superior Seedless foram pulverizados com ácido giberélico (1 + 20 mg.L-1, bioestimulante Crop Set® nas doses de 0,1 e 0,2% e com ou sem anelamento no caule. Esses tratamentos foram aplicados de forma isolada ou combinados entre si. O trabalho foi conduzido durante o período 2001-2002 (dois ciclos de produção, no Campo Experimental de Bebedouro da Embrapa Semi-Árido em Petrolina-PE. O delineamento experimental foi em blocos ao acaso, com 12 tratamentos e três repetições, sendo duas plantas por parcela. Não foram observadas diferenças significativas entre os tratamentos nos dois ciclos de produção. Entretanto, quando o ácido giberélico foi associado ao Crop Set® 0,1% e anelamento, observou-se uma tendência de aumento no peso de cachos, bem como no peso e tamanho de bagas na safra de 2001. Os cachos tratados com ácido giberélico apresentaram engaços mais grossos e pesados, embora não se observem diferenças significativas entre os tratamentos. Algumas plantas submetidas ao anelamento apresentaram problemas de cicatrização, o que provocou a morte das mesmas, recomendando-se evitar a realização desta prática nas condições em que se realizou este trabalho.Aiming to increase the berry size, weight of bunches and yield, the bunches of the cv. Superior Seedless was powdered with gibberelic acid (1 + 20 mg.L-1, bio-stimulant Crop Set® in the dosis of 0.1 and 0.2%. In adition was used the treatment known as girdling. Those treatments were applied in an isolated way or combined to each other. The work was carried out during 2001-2002 (two harvest seasons, in the Experimental Station of Bebedouro, Semi-arid Embrapa in Petrolina, Pernambuco State. The experimental design were in randomized blocks with 12 treatments and three replications. The differences among the treatments were not statistical significant in the two

  17. Generation of Electron Bunches at Low Repetition Rates Using a Beat-Frequency Technique

    Energy Technology Data Exchange (ETDEWEB)

    Poelker, Matt; Grames, Joseph; Hansknecht, John; Kazimi, Reza; Musson, John

    2007-05-01

    Even at a continuous wave facility such as CEBAF at Jefferson Lab, an electron beam with long time intervals (tens of ns) between individual bunches can be useful, for example to isolate sources of background via time of flight detection or to measure the energy of neutral particles that cannot be separated with a magnetic field. This paper describes a demonstrated method to quickly and easily deliver bunches with repetition rates of 20 to 100 MHz corresponding to time intervals between 10 to 50 ns (respectively). This is accomplished by changing the ON/OFF frequency of the RF-pulsed drive laser by a small amount (f/f < 20%), resulting in a bunch frequency equal to the beat frequency between the radio frequencies of the drive laser and the photoinjector chopper system.

  18. Coupling of relative intensity noise and pathlength noise to the length measurement in the optical metrology system of LISA Pathfinder

    Science.gov (United States)

    Wittchen, Andreas; the LPF Collaboration

    2017-05-01

    LISA Pathfinder is a technology demonstration mission for the space-based gravitational wave observatory, LISA. It demonstrated that the performance requirements for the interferometric measurement of two test masses in free fall can be met. An important part of the data analysis is to identify the limiting noise sources. [1] This measurement is performed with heterodyne interferometry. The performance of this optical metrology system (OMS) at high frequencies is limited by sensing noise. One such noise source is Relative Intensity Noise (RIN). RIN is a property of the laser, and the photodiode current generated by the interferometer signal contains frequency dependant RIN. From this electric signal the phasemeter calculates the phase change and laser power, and the coupling of RIN into the measurement signal depends on the noise frequency. RIN at DC, at the heterodyne frequency and at two times the heterodyne frequency couples into the phase. Another important noise at high frequencies is path length noise. To reduce the impact this noise is suppressed with a control loop. Path length noise not suppressed will couple directly into the length measurement. The subtraction techniques of both noise sources depend on the phase difference between the reference signal and the measurement signal, and thus on the test mass position. During normal operations we position the test mass at the interferometric zero, which is optimal for noise subtraction purposes. This paper will show results from an in-flight experiment where the test mass position was changed to make the position dependant noise visible.

  19. Isotopic fractionation in proteins as a measure of hydrogen bond length.

    Science.gov (United States)

    McKenzie, Ross H; Athokpam, Bijyalaxmi; Ramesh, Sai G

    2015-07-28

    If a deuterated molecule containing strong intramolecular hydrogen bonds is placed in a hydrogenated solvent, it may preferentially exchange deuterium for hydrogen. This preference is due to the difference between the vibrational zero-point energy for hydrogen and deuterium. It is found that the associated fractionation factor Φ is correlated with the strength of the intramolecular hydrogen bonds. This correlation has been used to determine the length of the H-bonds (donor-acceptor separation) in a diverse range of enzymes and has been argued to support the existence of short low-barrier H-bonds. Starting with a potential energy surface based on a simple diabatic state model for H-bonds, we calculate Φ as a function of the proton donor-acceptor distance R. For numerical results, we use a parameterization of the model for symmetric O-H⋯O bonds [R. H. McKenzie, Chem. Phys. Lett. 535, 196 (2012)]. We consider the relative contributions of the O-H stretch vibration, O-H bend vibrations (both in plane and out of plane), tunneling splitting effects at finite temperature, and the secondary geometric isotope effect. We compare our total Φ as a function of R with NMR experimental results for enzymes, and in particular with an earlier model parametrization Φ(R), used previously to determine bond lengths.

  20. Correlation of intra-articular osseous measurements with posterior cruciate ligament length on MRI scans.

    LENUS (Irish Health Repository)

    Orakzai, S H

    2010-01-01

    Six patients with a clinical diagnosis of chronic posterior cruciate ligament (PCL) rupture, based on a positive posterior drawer test, had a normal appearance of the PCL on an MRI scan. It is postulated that the PCL had been ruptured but healed in a lengthened state. 12 volunteers with no history of knee trauma underwent an MRI scan of the knee. In this control group (n = 12), there was a close correlation between the lateral femoral condylar width in the sagittal plane and the PCL length, with a ratio of 2:1 (95% confidence interval (CI) = 1.817-2.095). In the clinically abnormal group (n = 6), the ratio was 1.49:1 (95% CI = 1.206-1.782) (p< 0.0005). In conclusion, the ratio of the lateral femoral condylar width in the sagittal plane to the PCL length is a useful index for diagnosing PCL attenuation and lengthening in the presence of a normal morphological MR appearance.

  1. Isotopic fractionation in proteins as a measure of hydrogen bond length

    Energy Technology Data Exchange (ETDEWEB)

    McKenzie, Ross H., E-mail: r.mckenzie@uq.edu.au [School of Mathematics and Physics, University of Queensland, Brisbane 4072 (Australia); Athokpam, Bijyalaxmi; Ramesh, Sai G. [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India)

    2015-07-28

    If a deuterated molecule containing strong intramolecular hydrogen bonds is placed in a hydrogenated solvent, it may preferentially exchange deuterium for hydrogen. This preference is due to the difference between the vibrational zero-point energy for hydrogen and deuterium. It is found that the associated fractionation factor Φ is correlated with the strength of the intramolecular hydrogen bonds. This correlation has been used to determine the length of the H-bonds (donor-acceptor separation) in a diverse range of enzymes and has been argued to support the existence of short low-barrier H-bonds. Starting with a potential energy surface based on a simple diabatic state model for H-bonds, we calculate Φ as a function of the proton donor-acceptor distance R. For numerical results, we use a parameterization of the model for symmetric O–H⋯O bonds [R. H. McKenzie, Chem. Phys. Lett. 535, 196 (2012)]. We consider the relative contributions of the O–H stretch vibration, O–H bend vibrations (both in plane and out of plane), tunneling splitting effects at finite temperature, and the secondary geometric isotope effect. We compare our total Φ as a function of R with NMR experimental results for enzymes, and in particular with an earlier model parametrization Φ(R), used previously to determine bond lengths.

  2. Simultaneous water vapor and dry air optical path length measurements and compensation with the large binocular telescope interferometer

    Science.gov (United States)

    Defrère, D.; Hinz, P.; Downey, E.; Böhm, M.; Danchi, W. C.; Durney, O.; Ertel, S.; Hill, J. M.; Hoffmann, W. F.; Mennesson, B.; Millan-Gabet, R.; Montoya, M.; Pott, J.-U.; Skemer, A.; Spalding, E.; Stone, J.; Vaz, A.

    2016-08-01

    The Large Binocular Telescope Interferometer uses a near-infrared camera to measure the optical path length variations between the two AO-corrected apertures and provide high-angular resolution observations for all its science channels (1.5-13 microns). There is however a wavelength dependent component to the atmospheric turbulence, which can introduce optical path length errors when observing at a wavelength different from that of the fringe sensing camera. Water vapor in particular is highly dispersive and its effect must be taken into account for high-precision infrared interferometric observations as described previously for VLTI/MIDI or the Keck Interferometer Nuller. In this paper, we describe the new sensing approach that has been developed at the LBT to measure and monitor the optical path length fluctuations due to dry air and water vapor separately. After reviewing the current performance of the system for dry air seeing compensation, we present simultaneous H-, K-, and N-band observations that illustrate the feasibility of our feedforward approach to stabilize the path length fluctuations seen by the LBTI nuller.

  3. Temperature measurement and optical path-length bias improvement modifications to National Institute of Standards and Technology ozone reference standards.

    Science.gov (United States)

    Norris, James E; Choquette, Steven J; Viallon, Joele; Moussay, Philippe; Wielgosz, Robert; Guenther, Franklin R

    2013-05-01

    Ambient ozone measurements in the United States and many other countries are traceable to a National Institute of Standards and Technology Standard Reference Photometer (NIST SRP). The NIST SRP serves as the highest level ozone reference standard in the United States, with NIST SRPs located at NIST and at many U.S. Environmental Protection Agency (EPA) laboratories. The International Bureau of Weights and Measures (BIPM) maintains a NIST SRP as the reference standard for international measurement comparability through the International Committee of Weights and Measures (CIPM). In total, there are currently NIST SRPs located in 20 countries for use as an ozone reference standard. A detailed examination of the NIST SRP by the BIPM and NIST has revealed a temperature gradient and optical path-length bias inherent in all NIST SRPs. A temperature gradient along the absorption cells causes incorrect temperature measurements by as much as 2 degrees C. Additionally, the temperature probe used for temperature measurements was found to inaccurately measure the temperature of the sample gas due to a self-heating effect. Multiple internal reflections within the absorption cells produce an actual path length longer than the measured fixed length used in the calculations for ozone mole fractions. Reflections from optical filters located at the exit of the absorption cells add to this effect. Because all NIST SRPs are essentially identical, the temperature and path-length biases exist on all units by varying amounts dependent upon instrument settings, laboratory conditions, and absorption cell window alignment. This paper will discuss the cause of and physical modifications for reducing these measurement biases in NIST SRPs. Results from actual NIST SRP bias upgrades quantifying the effects of these measurement biases on ozone measurements are summarized. NIST SRPs are maintained in laboratories around the world underpinning ozone measurement calibration and traceability within

  4. Femtosecond timing-jitter between photo-cathode laser and ultra-short electron bunches by means of hybrid compression

    CERN Document Server

    Pompili, Riccardo; Bellaveglia, M; Biagioni, A; Castorina, G; Chiadroni, E; Cianchi, A; Croia, M; Di Giovenale, D; Ferrario, M; Filippi, F; Gallo, A; Gatti, G; Giorgianni, F; Giribono, A; Li, W; Lupi, S; Mostacci, A; Petrarca, M; Piersanti, L; Di Pirro, G; Romeo, S; Scifo, J; Shpakov, V; Vaccarezza, C; Villa, F

    2017-01-01

    The generation of ultra-short electron bunches with ultra-low timing-jitter relative to the photo-cathode (PC) laser has been experimentally proved for the first time at the SPARC_LAB test-facility (INFN-LNF, Frascati) exploiting a two-stage hybrid compression scheme. The first stage employs RF-based compression (velocity-bunching), which shortens the bunch and imprints an energy chirp on it. The second stage is performed in a non-isochronous dogleg line, where the compression is completed resulting in a final bunch duration below 90 fs (rms). At the same time, the beam arrival timing-jitter with respect to the PC laser has been measured to be lower than 20 fs (rms). The reported results have been validated with numerical simulations.

  5. Excitation of Intra-bunch Vertical Motion in the SPS - Implications for Feedback Control of Ecloud and TMCI Instabilities

    CERN Document Server

    Cesaratto, John; Pivi, M T; Rivetta, C H; Turgut, O; Uemura, S; Hofle, W; Wehrle, U

    2012-01-01

    Electron cloud (ecloud) and transverse mode coupledbunch instabilities (TMCI) limit the bunch intensity in the CERN SPS. This paper presents experimental measurements in the SPS of single-bunch motion driven by a GHz bandwidth vertical excitation system [1]. The nal goal is to quantify the change in internal bunch dynamics as instability thresholds are approached, and quantify the frequencies of internal modes as ecloud effects become signicant. Initially, we have been able to drive the beam and view its motion. We show the excitation of barycentric, head-tail and higher vertical modes at different bunch intensities. The beam motion is analyzed in the time domain, via animated presentations of the sampled vertical signals, and in the frequency domain, via spectrograms showing the modal frequencies vs. time. The demonstration of the excitation of selected internal modes is a signicant step in the development of the feedback control techniques.

  6. The Accuracy of the Digital imaging system and the frequency dependent type apex locator in root canal length measurement

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byoung Rib; Park, Chang Seo [Dept. of Dental Radiology, College of Dentistry, Yensei University, Seoul (Korea, Republic of)

    1998-08-15

    In order to achieve a successful endodontic treatment, root canals must be obturated three-dimensionally without causing any damage to apical tissues. Accurate length determination of the root canal is critical in this case. For this reason, I've used the conventional periapical radiography, Digora (digital imaging system) and Root ZX (the frequency dependent type apex locator) to measure the length of the canal and compare it with the true length obtained by cutting the tooth in half and measuring the length between the occlusal surface and the apical foramen. From the information obtained by these measurements, I was able to evaluate the accuracy and clinical usefulness of each systems, whether the thickness of files used in endodontic therapy has any effect on the measuring systems was also evaluated in an effort to simplify the treatment planning phase of endodontic treatment. 29 canals of 29 sound premolars were measured with no 15, no 20, no 25 files by 3 different dentists each using the periapical radiography, Digora and Root ZX. The measurements were then compared with the true length. The results were as follows; 1. In comparing mean discrepancies between measurements obtained by using periapical radiography (mean error : -0.449 {+-} 0.444 mm), Digora (mean error : -0.417 {+-} 0.415 mm) and Root ZX (mean error : 0.123 {+-} 0.458 mm) with true length, periapical radiography and Digora system had statistically significant differences (p<0.05) in most cases while root zx showed none (p>0.05). 2. By subtracting values obtained by using periapical radiography, Digora and Root ZX from the true length and making a distribution table of their absolute values, the following analysis was possible. In the case of periapical film, 140 out of 261 (53.6%) were clinically acceptable satisfying the margin of error of less than 0.5 mm, 151 out of 261 (53,6%) were acceptable in the Digora system while Root ZX had 197 out of 261 (75.5%) within the limits of 0.5 mm

  7. Characterizing acid diffusion lengths in chemically amplified resists from measurements of deprotection kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Abhijit A. [University of Houston, Department of Chemical and Biomolecular Engineering, 4800 Calhoun Road, Houston, Texas 77204, United States; Pandey, Yogendra Narayan [University of Houston, Department of Chemical and Biomolecular Engineering, 4800 Calhoun Road, Houston, Texas 77204, United States; Doxastakis, Manolis [Institute for Molecular Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States; Stein, Gila E. [University of Houston, Department of Chemical and Biomolecular Engineering, 4800 Calhoun Road, Houston, Texas 77204, United States

    2014-10-01

    The acid-catalyzed deprotection of glassy poly(4-hydroxystyrene-co-tertbutyl acrylate) films was studied with infrared absorbance spectroscopy and stochastic simulations. Experimental data were interpreted with a simple description of subdiffusive acid transport coupled to second-order acid loss. This model predicts key attributes of observed deprotection rates, such as fast reaction at short times, slow reaction at long times, and a nonlinear dependence on acid loading. Fickian diffusion is approached by increasing the post-exposure bake temperature or adding plasticizing agents to the polymer resin. These findings demonstrate that acid mobility and overall deprotection kinetics are coupled to glassy matrix dynamics. To complement the analysis of bulk kinetics, acid diffusion lengths were calculated from the anomalous transport model and compared with nanopattern line widths. The consistent scaling between experiments and simulations suggests that the anomalous diffusion model could be further developed into a predictive lithography tool.

  8. Much Ado about Microbunching: Coherent Bunching in High Brightness Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Ratner, Daniel [Stanford Univ., CA (United States)

    2011-05-01

    The push to provide ever brighter coherent radiation sources has led to the creation of correspondingly bright electron beams. With billions of electrons packed into normalized emittances (phase space) below one micron, collective effects may dominate both the preservation and use of such ultra-bright beams. An important class of collective effects is due to density modulations within the bunch, or microbunching. Microbunching may be deleterious, as in the case of the Microbunching Instability (MBI), or it may drive radiation sources of unprecedented intensity, as in the case of Free Electron Lasers (FELs). In this work we begin by describing models of microbunching due to inherent beam shot noise, which sparks both the MBI as well as SLAC's Linac Coherent Light Source, the world's first hard X-ray laser. We first use this model to propose a mechanism for reducing the inherent beam shot noise as well as for predicting MBI effects. We then describe experimental measurements of the resulting microbunching at LCLS, including optical radiation from the MBI, as well as the first gain length and harmonic measurements from a hard X-ray FEL. In the final chapters, we describe schemes that use external laser modulations to microbunch light sources of the future. In these sections we describe coherent light source schemes for both both linacs and storage rings.

  9. Predicted singers' vocal fold lengths and voice classification-a study of x-ray morphological measures.

    Science.gov (United States)

    Roers, Friederike; Mürbe, Dirk; Sundberg, Johan

    2009-07-01

    Students admitted to the solo singing education at the University of Music Dresden, Germany have been submitted to a detailed physical examination of a variety of factors with relevance to voice function since 1959. In the years 1959-1991, this scheme of examinations included X-ray profiles of the singers' vocal tracts. This material of 132 X-rays of voice professionals was used to investigate different laryngeal morphological measures and their relation to vocal fold length. Further, the study aimed to investigate if there are consistent anatomical differences between singers of different voice classifications. The study design used was a retrospective analysis. Vocal fold length could be measured in 29 of these singer subjects directly. These data showed a strong correlation with the anterior-posterior diameter of the subglottis and the trachea as well as with the distance from the anterior contour of the thyroid cartilage to the anterior contour of the spine. These relations were used in an attempt to predict the 132 singers' vocal fold lengths. The results revealed a clear covariation between predicted vocal fold length and voice classification. Anterior-posterior subglottic-tracheal diameter yielded mean vocal fold lengths of 14.9, 16.0, 16.6, 18.4, 19.5, and 20.9mm for sopranos, mezzo-sopranos, altos, tenors, baritones, and basses, respectively. The data support the assumption that there are consistent anatomical laryngeal differences between singers of different voice classifications, which are of relevance to pitch range and timbre of the voice.

  10. In vivo measurement of the local optical properties of tissue by use of differential path-length spectroscopy.

    Science.gov (United States)

    Amelink, Arjen; Sterenborg, Henricus J C M; Bard, Martin P L; Burgers, Sjaak A

    2004-05-15

    We demonstrate the capability of differential path-length spectroscopy (DPS) to determine the local optical properties of tissue in vivo. DPS measurements on bronchial mucosa are analyzed and yield information on the local blood oxygenation, blood content, average microvessel diameter, and wavelength dependence of the reduced scattering coefficient. Our data collected to date show that cancerous bronchial mucosa has a lower capillary oxygenation and a larger average capillary diameter than normal bronchial mucosa.

  11. Observation of coherently enhanced tunable narrow-band terahertz transition radiation from a relativistic sub-picosecond electron bunch train

    Energy Technology Data Exchange (ETDEWEB)

    Piot, P. [Northern Illinois Univ., DeKalb, IL (United States); Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Sun, Y. -E [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Maxwell, T. J. [Northern Illinois Univ., DeKalb, IL (United States); Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Ruan, J. [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Lumpkin, A. H. [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Rihaoui, M. M. [Northern Illinois Univ., DeKalb, IL (United States); Thurman-Keup, R. [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)

    2011-06-27

    We experimentally demonstrate the production of narrow-band (δf/f ~ =20% at f ~ = 0.5 THz) THz transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. In addition, we show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.

  12. Stability of bunched fluxons in magnetically coupled Josephson junctions

    DEFF Research Database (Denmark)

    Grønbech-Jensen, Niels; Cai, David; Samuelsen, Mogens Rugholm

    1993-01-01

    The stability of bunched fluxon states in inductively coupled Josephson junctions is analyzed for fluxons of both equal and opposite polarity. We demonstrate that unipolar fluxons may form stable bunched states if the velocity is above a given threshold. The stability of these bunched states is b...... is based on the existence of two characteristic velocities in the coupled system. The result of analytical stability analysis is in excellent agreement with the results of numerical simulations....

  13. Isotopic fractionation in proteins as a measure of hydrogen bond length

    CERN Document Server

    McKenzie, Ross H; Ramesh, Sai

    2015-01-01

    If a deuterated molecule containing strong intramolecular hydrogen bonds is placed in a hydrogenated solvent it may preferentially exchange deuterium for hydrogen. This preference is due to the difference between the vibrational zero-point energy for hydrogen and deuterium. It is found that the associated fractionation factor $\\Phi$ is correlated with the strength of the intramolecular hydrogen bonds. This correlation has been used to determine the length of the H-bonds (donor-acceptor separation) in a diverse range of enzymes and has been argued to support the existence of short low-barrier H-bonds. Starting with a potential energy surface based on a simple diabatic state model for H-bonds we calculate $\\Phi$ as a function of the proton donor-acceptor distance $R$. For numerical results, we use a parameterization of the model for symmetric O-H.... O bonds. We consider the relative contributions of the O-H stretch vibration, O-H bend vibrations (both in plane and out of plane), tunnelling splitting effects at...

  14. Measurements of neutron spectrum from stopping-length target irradiated by several tens-MeV/u particles

    Energy Technology Data Exchange (ETDEWEB)

    Meigo, Shin-ichiro; Takada, Hiroshi; Nakashima, Hiroshi; Sasa, Toshinobu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Tanaka, Susumu; Shin, Kazuo; Ono, Shinji

    1997-03-01

    Using a Time-of-Flight technique, we have measured neutron spectra from stopping-length targets bombarded with 68-MeV protons and 100-MeV {alpha}-particles. The measured spectra were used to validate the results calculated by the Quantum Molecular Dynamics (QMD) plus Statistical Decay Model (SDM). The results of QMD plus SDM code agreed fairly well with the experimental data for the light target. On the other hand, the QMD plus SDM gives a larger value than the experimental for the heavy target. (author)

  15. Distortion of Crabbed Bunch Due to the Electron Cloud

    Energy Technology Data Exchange (ETDEWEB)

    Wang, L; Raubenheimer, T.; /SLAC

    2008-05-28

    In order to improve the luminosity, two crab cavities have been installed in KEKB HER and LER [1]. Since there is only one crab cavity in each ring, the crab cavity generates a horizontally titled bunch along the whole ring. The achieved specific luminosity with crabbed bunch is higher, but it is not as high as that from beam-beam simulation [2]. One of the suspicions is the electron cloud. The electron cloud in LER (positron beam) may distort the crabbed bunch and cause the luminosity drop. This note briefly estimates the bunch shape distortion due to the electron cloud in KEKB LER.

  16. Tax Bunching, Income Shifting and Self-employment

    DEFF Research Database (Denmark)

    le Maire, Christian Daniel; Schjerning, Bertel

    2013-01-01

    This paper proposes a dynamic extension to Saez (2010) bunching formula that allows us to distinguish bunching based on real responses and income shifting. We provide direct evidence of income shifting and pronounced bunching in taxable income for the Danish self-employed. If income shifting...... was neglected in this case, we would estimate a taxable income elasticity in the range of 0.43-0.53 and conclude that taxable incomes were highly sensitive to changes in marginal tax rates. We show, however, that more than half of the bunching in taxable income is driven by intertemporal income shifting...

  17. Radiation of charged-particle bunches passing perpendicularly by the edge of a semi-infinite planar wire structure.

    Science.gov (United States)

    Tyukhtin, Andrey V; Vorobev, Viktor V; Galyamin, Sergey N

    2015-06-01

    The radiation of a charged-particle bunch moving perpendicularly to a semi-infinite plane grid composed of thin parallel wires is analyzed using the method of averaged boundary conditions (the period of the grid is assumed to be much less than the wavelengths under investigation). We perform an analysis of the volume radiation and surface waves generated by a bunch of finite length. It is shown that the patterns of the volume radiation fundamentally differ from those that arise in the case of an infinite grid. The properties of the surface waves are similar to the properties of Cherenkov radiation in a three-dimensional wire metamaterial. These waves propagate along the wires at the speed of light in a vacuum and do not diminish with distance (if absorption is negligible). The structure of the surface waves allows for the determination of the size and form of the particle bunches.

  18. Influence of apical periodontitis on the accuracy of 3 electronic root canal length measurement devices: an in vivo study.

    Science.gov (United States)

    Saatchi, Masoud; Aminozarbian, Mohammad Ghasem; Hasheminia, Seyed Mohsen; Mortaheb, Amin

    2014-03-01

    The aim of this in vivo study was to evaluate the influence of apical periodontitis (AP) on the accuracy of Dentaport ZX (J Morita, Kyoto, Japan), Raypex 5 (VDW, Munich, Germany), and i-Root (S-Denti, Seoul, Korea) electronic root canal length measurement devices (ERCLMDs). Thirty-two single-rooted teeth scheduled for extraction, consisting of 16 teeth with AP and 16 teeth with normal periapex (NP), were selected. The access cavity was prepared, and the coronal portion of the canal was flared. The electronic working length (EWL) was determined by each ERCLMD according to each manufacturer's instructions. Each tooth was extracted, and the actual working length (AWL) was determined by inserting a size 15 K-file until the tip could be seen at a position tangential to the major foramen and then 0.5 mm was subtracted from the measurement. The distance from the file tip (EWL) to the point 0.5 mm coronal to the major foramen (AWL) was calculated. Data were analyzed using the nonparametric Fisher exact test and the chi-square test. Statistical significance was set at P device in the 2 groups (P > .05). Considering the 2 groups of AP and NP, there were no statistically significant differences in the accuracy of the ERCLMDs (P > .05). The presence of AP did not influence the accuracy of ERCLMDs. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  19. Single bunch stability to monopole excitation

    Directory of Open Access Journals (Sweden)

    Sam Heifets

    1999-04-01

    Full Text Available We study single bunch stability with respect to monopole longitudinal oscillations in electron storage rings. Our analysis is different from the standard approach based on the linearized Vlasov equation. Rather, we reduce the full nonlinear Fokker-Planck equation to a Schrödinger-like equation which is subsequently analyzed by perturbation theory. We show that the Haissinski solution [Nuovo Cimento Soc. Ital. Fis. 18B, 72 (1973] may become unstable with respect to monopole oscillations and derive a stability criterion in terms of the ring impedance. We then discuss this criterion and apply it to a broadband resonator impedance model.

  20. Life expectancy: complex measures of the length and the health related quality of life

    Directory of Open Access Journals (Sweden)

    Daniele Spizzichino

    2008-06-01

    Full Text Available

    Background: Life expectancy is one of the most frequently used indicators to assess mortality and the health of a population. It is a synthetic measure of mortality, which has the advantage of allowing for comparisons over time and between different groups, while eliminating the influence of the age structure of the population. Life expectancy has the advantage of being very easy to understand, although it needs to be interpreted within the context of the complex system of hypothesis that generates it. This is even more important for health expectancies and health gap measures, which are synthetic indicators that take into account both survival and health condition of a population.

    Methods: It is given a description of the most frequently used methods to calculate life expectancy, health expectancies and health gap measures. Measures of health expectancy are disability free life expectancy and healthy life expectancy. As health gap measures, frequently are used DALYs (Disability Adjusted Life Years.

    Discussion: There are various bodies and central government agencies that either have management data or carry out statistical systematic surveys and disability surveys. Statistically speaking, the worst aspect of this scenario is that it creates confusion and uncertainty among the end users of this data, namely the policy makers. At an international level the statistical data on disability is scarcely comparable among countries, despite huge efforts on the part of international organisations to harmonize classifications and definitions of disability.

    Results and Conclusions: There are several methods to compute life expectancy, each of these has some advantages and some disadvantages. Usually life expectancy is used also to account for the health status of population. Actually with the growing role of chronic and degenerative diseases, the increased number of

  1. Measurement of changes in optical path length and reflectivity with phase-shifting laser feedback interferometry.

    Science.gov (United States)

    Ovryn, B; Andrews, J H

    1999-04-01

    The operating characteristics of a novel phase-shifting interferometer are presented. Interference arises by reflecting the light from a sample back into the cavity of a cw He-Ne laser. Changes in phase and fringe visibility are calculated from an overdetermined set of phase-shifted intensity measurements with the phase shifts being introduced with an electro-optic modulator. The interferometer is sensitive enough to measure displacements below 1 Hz with a rms error of approximately 1 nm from a sample that reflects only 3% of the 28 microW that is incident on its surface. The interferometer is applied to the determination of cantilever bending of a piezoelectric bimorph.

  2. The use of cone beam computed tomography to predetermine root canal lengths in molar teeth: a comparison between two-dimensional and three-dimensional measurements.

    Science.gov (United States)

    Tchorz, J P; Poxleitner, P J; Stampf, S; Patzelt, S B M; Rottke, D; Hellwig, E; Altenburger, M J

    2014-05-01

    The aim of this study was to evaluate the accuracy of two-dimensional (2D) and three-dimensional (3D) root canal length measurements in molar teeth using cone beam computed tomography (CBCT). Root canal lengths of twenty molar teeth were measured with two different CBCT approaches. After adjusting the CBCT images, 2D measurements were performed within the sagittal plane between the apical foramen and the coronal reference (cusp). The 3D approach measured centrically in axial planes. A linear mixed model with random intercepts was fitted to compare differences between methods (2D and 3D). The correlation between CBCT measurements and the actual root canal length was evaluated using the Pearson correlation coefficient. Differences between 3D measurements and the actual root canal lengths were significantly smaller compared to the 2D approach (p < 0.001). Mean differences were 0.32 and 0.58 mm, respectively. A high correlation was found between the actual root canal length and 3D measurements (Pearson correlation coefficient = 0.97). Compared to the actual root canal length, 80 % of the 3D measurements were within the limits of ±0.5 mm. 3D measurements of root canals in molar teeth are more accurate than simple 2D measurements and show a high correlation to the actual lengths. In cases where a CBCT is already available, root canal lengths in molar teeth can be accurately predetermined using a standardized 3D approach.

  3. A study of the surface roughness lengths of a high-altitude topical glacier using profile and eddy covariance measurements

    Science.gov (United States)

    Sicart, J.; Litt, M.

    2012-12-01

    The turbulent fluxes remain poorly understood on tropical glaciers. Studies based on the bulk method have shown that sublimation can be high during the dry season, reducing the energy available for melting. However, uncertainties on the bulk method are large, especially when katabatic flows cause a wind speed maximum at low height. Wind and temperature data from an 8-level 6-m mast positioned at 5060 m asl in the ablation area of the Zongo Glacier, Bolivia (16°S), were collected during a one-month period in the dry season of 2007. Concomitant measurements of radiation fluxes and eddy covariance turbulent fluxes were conducted. The surface roughness lengths for temperature and momentum were calculated using the profile and the eddy covariance methods at the hourly time scale. The measurement period was characterized by low synoptic forcing conditions and katabatic wind prevailed at night and most of the day. Katabatic flows were often associated with a wind speed maximum at a height of about 2-3 m and with a strong temperature inversion. Near-neutral profiles were selected to avoid the presence of the katabatic wind speed maximum. Results indicate z0 values of about 3 mm and zT values of about 0.2 mm, in rough agreement with terrain observations. However the scatter in the zT values is large indicating large random errors. The relation between the ratio zT/z0 and the roughness Reynolds number is in rough agreement with the surface renewal model. However, this relation turns out to be mostly due to spurious self-correlation because of the shared variable z0 in zT/z0 and Re*. Finally, the random and systematic errors on the roughness lengths derived from the profile measurements were briefly investigated. The results emphasize the need of accurate measurements of the sensor heights to obtain unbiased roughness lengths.

  4. A study of the surface roughness lengths of a high-altitude tropical glacier using profile and eddy covariance measurements

    Science.gov (United States)

    Sicart, Jean-Emmanuel; Litt, Maxime; Ben Tahar, Vanessa

    2013-04-01

    The turbulent fluxes remain poorly understood on tropical glaciers. Studies based on the bulk method have shown that sublimation can be high during the dry season, reducing the energy available for melting. However, uncertainties on the bulk method are large, especially when katabatic flows cause a wind speed maximum at low height. Wind and temperature data from an 8-level 6-m mast positioned at 5060 m a.s.l. in the ablation area of the Zongo Glacier, Bolivia (16°S), were collected during a one-month period in the dry season of 2007. Concomitant measurements of radiation fluxes and eddy covariance turbulent fluxes were conducted. The surface roughness lengths for temperature (zT) and momentum (z0) were calculated using the profile and the eddy covariance methods at the hourly timescale. The measurement period was characterized by low synoptic forcing conditions and katabatic wind prevailed at night and most of the day. Katabatic flows were often associated with a wind speed maximum at a height of about 2-3 m and with a strong temperature inversion. Near-neutral profiles were selected to avoid the presence of the katabatic wind speed maximum. Results indicate z0 values of about 3 mm and zT values of about 0.2 mm, in rough agreement with terrain observations. However the scatter in the zT values is large indicating large random errors. The relation between the ratio zT/z0 and the roughness Reynolds number (Re*) is in rough agreement with the surface renewal model. However, this relation turns out to be mostly due to spurious self-correlation because of the shared variable z0 in zT/z0 and Re*. Finally, the random and systematic errors on the roughness lengths derived from the profile measurements were briefly investigated. The results emphasize the need of accurate measurements of the sensor heights to obtain unbiased roughness lengths.

  5. Density bunching effects in a laser-driven, near-critical density plasma for ion acceleration

    Science.gov (United States)

    Ettlinger, Oliver; Sahai, Aakash; Hicks, George; Ditter, Emma-Jane; Dover, Nicholas; Chen, Yu-Hsin; Helle, Michael; Gordon, Daniel; Ting, Antonio; Polyanskiy, Mikhail; Pogorelsky, Igor; Babzien, Marcus; Najmudin, Zulfikar

    2016-10-01

    We present work investigating the interaction of relativistic laser pulses with near-critical density gas targets exhibiting pre-plasma scale lengths of several laser wavelengths. Analytical and computational modelling suggest that the interaction dynamics in a low-Z plasma is a direct result of induced density bunching up to the critical surface. In fact, these bunches can themselves become overcritical and experience significant radiation pressure, accelerating ions to higher energies compared to an ``idealised'' plasma slab target. This work will be used to help explain the observation of ion energies exceeding those predicted by radiation pressure driven hole-boring in recent experiments using the TW CO2 laser at the Accelerator Test Facility at Brookhaven National Laboratory.

  6. Development of a Data Reduction Algorithm for Optical Wide Field Patrol (OWL II: Improving Measurement of Lengths of Detected Streaks

    Directory of Open Access Journals (Sweden)

    Sun-Youp Park

    2016-09-01

    Full Text Available As described in the previous paper (Park et al. 2013, the detector subsystem of optical wide-field patrol (OWL provides many observational data points of a single artificial satellite or space debris in the form of small streaks, using a chopper system and a time tagger. The position and the corresponding time data are matched assuming that the length of a streak on the CCD frame is proportional to the time duration of the exposure during which the chopper blades do not obscure the CCD window. In the previous study, however, the length was measured using the diagonal of the rectangle of the image area containing the streak; the results were quite ambiguous and inaccurate, allowing possible matching error of positions and time data. Furthermore, because only one (position, time data point is created from one streak, the efficiency of the observation decreases. To define the length of a streak correctly, it is important to locate the endpoints of a streak. In this paper, a method using a differential convolution mask pattern is tested. This method can be used to obtain the positions where the pixel values are changed sharply. These endpoints can be regarded as directly detected positional data, and the number of data points is doubled by this result.

  7. An Experimental Measurement on Laminar Burning Velocities and Markstein Length of Iso-Butane-Air Mixtures at Ambient Conditions

    Directory of Open Access Journals (Sweden)

    Yousif Alaeldeen Altag

    2016-01-01

    Full Text Available In the present work, experimental investigation on laminar combustion of iso-butane-air mixtures was conducted in constant volume explosion vessel. The experiments were conducted at wide range of equivalence ratios ranging between Ф = 0.6 and 1.4 and atmospheric pressure of 0.1 MPa and ambient temperature of 303K. Using spherically expanding flame method, flame parameters including stretched, unstretched flame propagation speeds, laminar burning velocities and Markstein length were calculated. For laminar burning velocities the method of error bars of 95% confidence level was applied. In addition, values of Markstein lengths were measured in wide range of equivalence ratios to study the influence of stretch rate on flame instability and burning velocity. It was found that the stretched flame speed and laminar burning velocities increased with equivalence ratios and the peak value was obtained at equivalence ratio of Ф = 1.1. The Markstein length decreased with the increases in equivalence ratios, which indicates that the diffusion thermal flame instability increased at high equivalence ratios in richer mixture side. However, the total deviations in the laminar burning velocities have discrepancies of 1.2-2.9% for all investigated mixtures.

  8. LEARNING ONE-DIGIT DECIMAL NUMBERS BY MEASUREMENT AND GAME PREDICTING LENGTH

    Directory of Open Access Journals (Sweden)

    Puji Astuti

    2014-01-01

    Full Text Available This paper aims to describe how students develop understanding of one-digit decimals. To achieve the aim, Local Instruction Theory (LIT about the process of learning decimals and the means designed to support that learning are developed. Along with this idea, the framework of Realistic Mathematics Education (RME is proposed. Based on the aim, design research methodology is used. This paper discusses learning activities of three meetings from teaching experiment of the focus group students of the fourth grade elementary school in Surabaya: SDIT Al Ghilmani. The data indicated that the learning activities promoted the students’ understanding of one-digit decimal numbers.Keyword: measurement, decimal numbers, number line DOI: http://dx.doi.org/10.22342/jme.5.1.1447.35-46

  9. Soft x-ray pulse length measurement by pump-probe absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tom, H.W.K. [Univ. of California, Riverside, CA (United States); Sher, M.H.; Mohideen, U.; Wood, O.R. II; Aumiller, G.D. [AT and T Bell Labs., Holmdel, NJ (United States); McIlrath, T.J. [Univ. of Maryland, College Park, MD (United States); Bokor, J.; Freeman, R.R. [AT and T Bell Labs., Murray Hill, NJ (United States); Sugar, J. [National Institute of Standards and Technology, Gaithersburg, MD (United States)

    1994-12-31

    The authors have demonstrated a system for subpicosecond, soft-x-ray continuum, pump-probe absorption spectroscopy. Using multiphoton ionization to abruptly change the x-ray absorption spectra of a gas, they have measured the temporal profile of laser-generated x-ray pulses near 90 eV. Although the x-ray pulses from a laser-generated plasma here were only as short as {approximately}20 psec, the technique is extendible to higher energy x-rays which will have pulse durations approaching 100 fsec. They also present the absorption spectrum of Kr ions produced under conditions of high intensity non-resonant multiphoton ionization. The spectra are identified with a fit to the Cowan code.

  10. Measuring Optimal Length of the Amplifying Fiber in Different Working Conditions of the Amplifier

    Directory of Open Access Journals (Sweden)

    Radek Poboril

    2014-01-01

    Full Text Available The aim of this article is to highlight possible unwanted behaviour of an EDFA optical amplifier during temperature changes. After a brief introduction dealing with amplifiers and doped fibers in general we focus on the assembly of our own EDFA amplifier with standard construction and the IsoGain I-6 amplifying fiber, and on the parameters of its individual components. Since an erbium doped fiber has usually no direct thermal stabilization, temperature changes can affect performance of the entire amplifier. The next part of the article therefore describes the impacts of such changes on behaviour of our amplifier. At the very end we performed a measurement of the amplifier deployed in the actual WDM-PON the description of which can be found in the last chapter.

  11. Multiple measures of adiposity are associated with mean leukocyte telomere length in the northern Finland birth cohort 1966.

    Directory of Open Access Journals (Sweden)

    Jessica L Buxton

    Full Text Available Studies of leukocyte telomere length (LTL and adiposity have produced conflicting results, and the relationship between body mass index (BMI and telomere length throughout life remains unclear. We therefore tested association of adult LTL measured in 5,598 participants with: i childhood growth measures (BMI and age at adiposity rebound (AR; ii change in BMI from childhood to adulthood and iii adult BMI, waist-to-hip ratio (WHR, body adiposity index (BAI. Childhood BMI at AR was positively associated with LTL at 31 years in women (P = 0.041. Adult BMI and WHR in both men (P = 0.025 and P = 0.049, respectively and women (P = 0.029 and P = 0.008, respectively, and BAI in women (P = 0.021 were inversely associated with LTL at 31 years. An increase in standardised BMI between early childhood and adulthood was associated with shorter adult LTL in women (P = 0.008. We show that LTL is inversely associated with multiple measures of adiposity in both men and women. Additionally, BMI increase in women from childhood to adulthood is associated with shorter telomeres at age 31, potentially indicating accelerated biological ageing.

  12. Multiple measures of adiposity are associated with mean leukocyte telomere length in the northern Finland birth cohort 1966.

    Science.gov (United States)

    Buxton, Jessica L; Das, Shikta; Rodriguez, Alina; Kaakinen, Marika; Couto Alves, Alexessander; Sebert, Sylvain; Millwood, Iona Y; Laitinen, Jaana; O'Reilly, Paul F; Jarvelin, Marjo-Riitta; Blakemore, Alexandra I F

    2014-01-01

    Studies of leukocyte telomere length (LTL) and adiposity have produced conflicting results, and the relationship between body mass index (BMI) and telomere length throughout life remains unclear. We therefore tested association of adult LTL measured in 5,598 participants with: i) childhood growth measures (BMI and age at adiposity rebound (AR)); ii) change in BMI from childhood to adulthood and iii) adult BMI, waist-to-hip ratio (WHR), body adiposity index (BAI). Childhood BMI at AR was positively associated with LTL at 31 years in women (P = 0.041). Adult BMI and WHR in both men (P = 0.025 and P = 0.049, respectively) and women (P = 0.029 and P = 0.008, respectively), and BAI in women (P = 0.021) were inversely associated with LTL at 31 years. An increase in standardised BMI between early childhood and adulthood was associated with shorter adult LTL in women (P = 0.008). We show that LTL is inversely associated with multiple measures of adiposity in both men and women. Additionally, BMI increase in women from childhood to adulthood is associated with shorter telomeres at age 31, potentially indicating accelerated biological ageing.

  13. Reliability and validity of ultrasound measurements of muscle fascicle length and pennation in humans: a systematic review.

    Science.gov (United States)

    Kwah, Li Khim; Pinto, Rafael Z; Diong, Joanna; Herbert, Robert D

    2013-03-15

    Ultrasound imaging is widely used to measure architectural features of human skeletal muscles in vivo. We systematically reviewed studies of the reliability and validity of two-dimensional ultrasound measurement of muscle fascicle lengths or pennation angles in human skeletal muscles. A comprehensive search was conducted in June 2011. Thirty-six reliability studies and six validity studies met the inclusion criteria. Data from these studies indicate that ultrasound measurements of muscle fascicle lengths are reliable across a broad range of experimental conditions [intraclass correlation coefficient (ICC) and r values were always > 0.6, and coefficient of variation values were always 0.5 and coefficient of variation values were always 0.7) under certain conditions, such as when large limb muscles are imaged in a relaxed state and the limb or joint remains stationary. Future studies on validity should consider ways to test for the validity of two-dimensional ultrasound imaging in contracted or moving muscles and the best method of probe alignment.

  14. Quality Assessment of Soaps Produced from Palm Bunch Ash ...

    African Journals Online (AJOL)

    Michael Horsfall

    ABSTRACT: The making of soap using vegetable matter (palm bunch waste) was examined. All the factors that impact blackish on the soap products after saponification process were studied with a view to remedying them. The remedial process involved subjecting the dried palm bunch matter to total combustion, soaking, ...

  15. Intermediate Review of Single Bunch Collective Effects in the LHC

    CERN Document Server

    Angal-Kalinin, Deepa; Vos, L

    2002-01-01

    This paper presents an intermediate review of the single bunch collective effects in the LHC. It first reviews the LHC impedance budget including all elements for which a design is presently available. Then, based on this updated budget, the corresponding rise times and thresholds for single bunch instabilities are evaluated and discussed.

  16. Evaluation of fruit and bunch traits in black Sigatoka resistant ...

    African Journals Online (AJOL)

    Studies involving the evaluation of fruit and bunch characteristics of twenty seven cultivars of plantain and banana were undertaken. Results showed that bunch weight of plantain hybrid, 25344-18, differed significantly (P<0.05) from all other genotypes except SH 3362, with an average of 20.8 kg plant. The number of hands ...

  17. Responses of savanna lawn and bunch grasses to water limitation

    NARCIS (Netherlands)

    van der Plas, Alfons; Zeinstra, Patricia; Veldhuis, Michiel; Fokkema, Rienk; Tielens, Elske; Howison, Ruth; Olff, Han

    The grass layer of African savannas consists of two main vegetation types: grazing lawns, dominated by short, mostly clonally reproducing grasses, and bunch grasslands, dominated by tall bunch grasses. This patchy distribution of vegetation types is mostly created by large herbivores, which

  18. Instability during bunch shortening of an electron-cooled beam

    Directory of Open Access Journals (Sweden)

    M. Takanaka

    2003-10-01

    Full Text Available Bunch shortening causes an electron-cooled beam to be space charge dominated at low energies. Instability during the bunch shortening has been studied using a particle-tracking program where the 3D space-charge field due to the beam is calculated with a simplifying model.

  19. Bunched soliton states in weakly coupled sine-Gordon systems

    DEFF Research Database (Denmark)

    Grønbech-Jensen, N.; Samuelsen, Mogens Rugholm; Lomdahl, P. S.

    1990-01-01

    The interaction between solitons of two weakly coupled sine-Gordon systems is considered. In particular, the stability of bunched states is investigated, and perturbation results are compared with numerical results.......The interaction between solitons of two weakly coupled sine-Gordon systems is considered. In particular, the stability of bunched states is investigated, and perturbation results are compared with numerical results....

  20. Cooling and bunching of ion beams for collinear laser spectroscopy

    CERN Document Server

    Nieminen, A; Billowes, J; Forest, D H; Griffith, J A R; Huikari, J; Jokinen, A; Moore, I D; Moore, R; Tungate, G; Äystö, J

    2003-01-01

    A greatly increased sensitivity in collinear laser spectroscopy experiments has been achieved by the application of new on-line ion cooling and bunching techniques. Cooling of a low-energy ion beam to low emittance and low velocity spread is shown to increase the peak efficiency while bunching the beam results in highly efficient background suppression.

  1. Femtosecond electron-bunch dynamics in laser wakefields and vacuum

    NARCIS (Netherlands)

    Khachatryan, A.G.; Irman, A.; van Goor, F.A.; Boller, Klaus J.

    2007-01-01

    Recent advances in laser wakefield acceleration demonstrated the generation of extremely short (with a duration of a few femtoseconds) relativistic electron bunches with relatively low (of the order of couple of percent) energy spread. In this article we study the dynamics of such bunches in drift

  2. Coupled-Beam and Coupled-Bunch Instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Burov, Alexey [Fermilab

    2016-06-23

    A problem of coupled-beam instability is solved for two multibunch beams with slightly different revolution frequencies, as in the Fermilab Recycler Ring (RR). Sharing of the inter-bunch growth rates between the intra-bunch modes is described. The general analysis is applied to the RR; possibilities to stabilize the beams by means of chromaticity, feedback and Landau damping are considered.

  3. Single-Bunch Stability With Direct Space Charge

    CERN Multimedia

    Oeftiger, Adrian

    2017-01-01

    Previous studies have shown the suppressing effect of direct space charge on impedance-driven head-tail instabilities. The present work investigates transverse stability for the HL-LHC scenario based on our macro-particle simulation tool PyHEADTAIL using realistic bunch distributions. The impact of selfconsistent modelling is briefly discussed for non-linear space charge forces. We study how space charge pushes the instability threshold for the transverse mode coupling instability (TMCI) occurring between mode 0 and -1. Next we consider finite chromaticity: in absence of space charge, the impedance model predicts head-tail instabilities. For a selected case below TMCI threshold at Q0 = 5, we demonstrate the stabilising effect of space charge. Finally, we compare simulation results to past LHC measurements.

  4. Mechanical measurements of heterogeneity and length scale effects in PEG-based hydrogels

    Science.gov (United States)

    Bush, Brian G.; Shapiro, Jenna M.; DelRio, Frank W.; Cook, Robert F.; Oyen, Michelle L.

    2015-01-01

    Colloidal-probe spherical indentation load-relaxation experiments with a probe radius of 3 μm are conducted on poly(ethylene glycol) (PEG) hydrogel materials to quantify their steady-state mechanical properties and time-dependent transport properties via a single experiment. PEG-based hydrogels are shown to be heterogeneous in both morphology and mechanical stiffness at this scale; a linear-harmonic interpolation of hyperelastic Mooney-Rivlin and Boussinesq flat-punch indentation models was used to describe the steady-state response of the hydrogels and determine upper and lower bounds for indentation moduli. Analysis of the transient load-relaxation response during displacement-controlled hold periods provides a means of extracting two time constants τ1 and τ2, where τ1 and τ2 are assigned to the viscoelastic and poroelastic properties, respectively. Large τ2 values at small indentation depths provide evidence of a non-equilibrium state characterized by a phenomenon that restricts poroelastic fluid flow through the material; for larger indentations, the variability in τ2 values decreases and pore sizes estimated from τ2 via indentation approach those measured via macroscopic swelling experiments. The contact probe methodology developed here provides a means of assessing hydrogel heterogeneity, including time-dependent mechanical and transport properties, and has potential implications in hydrogel biomedical and engineering applications. PMID:26255839

  5. Extracting quantitative measures from finite length nonlinear timeseries- complex systems approaches

    Science.gov (United States)

    Wicks, R.; Chapman, S. C.; Kiyani, K.; Hnat, B.; Dendy, R. O.

    2006-12-01

    We consider two complex systems approaches to obtaining quantitative measures from `real world' timeseries, such as in situ solar wind observations and geomagnetic indices, where information about the process in not known a priori. The first is statistical- we discuss the problem of obtaining the scaling exponents from the PDF of fluctuations (differenced variables) via PDF collapse and structure functions. If the probability density is heavy tailed, outliers strongly influence the scaling behaviour of the moments. From an operational point of view, we wish to recover the scaling exponents of the underlying process by excluding a minimal population of these outliers. We test these ideas on a synthetically generated symmetric alpha-stable Lèvy process and show that the Lèvy exponent is recovered in up to the 6th order moment after ~0.1-0.5% of the data are excluded. The scaling properties of the excluded outliers can then be tested to provide additional information about the system. We highlight application of this technique to in- situ spacecraft observation of the turbulent solar wind and to geomagnetic indices. The second of these is dynamical- we explore the use of Mutual Information (MI) as a method to determine order- disorder transitions and test this idea on the Viscek `boid' model for flocking. We compare MI with the full system susceptibility we demonstrate that MI can pinpoint the phase transition with reasonable accuracy. We also consider the MI as a tool for detecting nonlinear correlation between different systems with application to `space weather', that is, solar wind triggering of geomagnetic activity on the earth.

  6. Path-length-resolved measurements of multiple scattered photons in static and dynamic turbid media using phase-modulated low-coherence interferometry.

    Science.gov (United States)

    Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G; Steenbergen, Wiendelt

    2007-01-01

    In optical Doppler measurements, the path length of the light is unknown. To facilitate quantitative measurements, we develop a phase-modulated Mach-Zehnder interferometer with separate fibers for illumination and detection. With this setup, path-length-resolved dynamic light scattering measurements of multiple scattered light in static and dynamic turbid media are performed. Optical path length distributions spanning a range from 0 to 11 mm are measured from the area under the phase modulation peak around the modulation frequency in the power spectrum. A Doppler-broadened phase modulation interference peak is observed that shows an increase in the average Doppler shift with optical path length, independent of absorption. Validation of the estimated path length distributions is done by measuring their deformation for increasing absorption and comparing these observations with predictions based on Lambert-Beer's law.

  7. Evaluation of the CERN Super Proton Synchrotron longitudinal impedance from measurements of the quadrupole frequency shift

    Directory of Open Access Journals (Sweden)

    A. Lasheen

    2017-06-01

    Full Text Available Longitudinal instabilities are one of the main limitations in the CERN Super Proton Synchrotron (SPS to reach the beam parameters required for the High Luminosity LHC project. In preparation to the SPS upgrade, possible remedies are studied by performing macroparticle simulations using the machine impedance model obtained from electromagnetic simulations and measurements. To benchmark the impedance model, the results of simulations are compared with various beam measurements. In this study, the reactive part of the impedance was probed by measuring the quadrupole frequency shift with intensity, obtained from bunch length oscillations at mismatched injection into the SPS. This method was applied over many last years to follow up the evolution of the SPS impedance, injecting bunches with the same bunch length. A novel approach, giving significantly more information, consists in varying the injected bunch length. The comparison of these measurements with macroparticle simulations allowed us to test the existing model, identify some missing SPS impedance and to obtain its possible dependence on frequency.

  8. Correlations of leaf area with length and width measurements of leaves of black oak, white oak, and sugar maple

    Science.gov (United States)

    Philip M. Wargo

    1978-01-01

    Correlations of leaf area with length, width, and length times width of leaves of black oak, white oak, and sugar maple were determined to see if length and/or width could be used as accurate estimators of leaf area. The correlation of length times width with leaf area was high (r > + .95) for all three species. The linear equation Y = a + bX, where X = length times...

  9. Natural Fiber Cut Machine Semi-Automatic Linear Motion System for Empty Fiber Bunches: Re-designing for Local Use

    Science.gov (United States)

    Asfarizal; Kasim, Anwar; Gunawarman; Santosa

    2017-12-01

    Empty Palm bunches of fiber is local ingredient in Indonesia that easy to obtain. Empty Palm bunches of fiber can be obtained from the palm oil industry such as in West Pasaman. The character of the empty Palm bunches of fiber that is strong and pliable has high-potential for particle board. To transform the large quantities of fiber become particles in size 0-10 mm requires a specially designed cut machine. Therefore, the machine is designed in two-stage system that is mechanical system, structure and cutting knife. Components that have been made, assembled and then tested to reveal the ability of the machine to cut. The results showed that the straight back and forth motion cut machine is able to cut out the empty oil palm bunches of fiber with a length 0-1 cm, 2 cm, 8 cm and the surface of the cut is not stringy. The cutting capacity is at a length of 2 cm in the result 24.4 (kg/h) and 8 cm obtained results of up to 84 (kg/h)

  10. The accuracy of three-dimensional fused deposition modeling (FDM) compared with three-dimensional CT-Scans on the measurement of the mandibular ramus vertical length, gonion-menton length, and gonial angle

    Science.gov (United States)

    Savitri, I. T.; Badri, C.; Sulistyani, L. D.

    2017-08-01

    Presurgical treatment planning plays an important role in the reconstruction and correction of defects in the craniomaxillofacial region. The advance of solid freeform fabrication techniques has significantly improved the process of preparing a biomodel using computer-aided design and data from medical imaging. Many factors are implicated in the accuracy of the 3D model. To determine the accuracy of three-dimensional fused deposition modeling (FDM) models compared with three-dimensional CT scans in the measurement of the mandibular ramus vertical length, gonion-menton length, and gonial angle. Eight 3D models were produced from the CT scan data (DICOM file) of eight patients at the Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Indonesia, Cipto Mangunkusumo Hospital. Three measurements were done three times by two examiners. The measurements of the 3D CT scans were made using OsiriX software, while the measurements of the 3D models were made using a digital caliper and goniometry. The measurement results were then compared. There is no significant difference between the measurements of the mandibular ramus vertical length, gonion-menton length, and gonial angle using 3D CT scans and FDM 3D models. FDM 3D models are considered accurate and are acceptable for clinical applications in dental and craniomaxillofacial surgery.

  11. Stature estimation based on the length of tibia and fibula measured by digital X-ray in Chinese Han teenagers.

    Science.gov (United States)

    Wang, Yu-Zhuo; Huang, Yun; Zhou, Xiao-Rong; Deng, Zhen-Hua

    2012-12-01

    To derive regression formulae for stature estimation using forensic radiography from the tibia and fibula of Chinese Han teenagers in Sichuan Province. To construct equations, measurements were conducted on the training sample (412 adults, 201 males and 211 females). The whole length of the fibula and four measurements of tibia were determined using CR radiography, rectified through theoretical magnification. The regression formulae were relatively constructed to the real stature measured in an erect position. Through using the testing sample (40 adults) for the regression formulae, the reliability of the regression formulae was assessed. The range of correlation coefficients of four measurements for tibia was 0.880-0.895 in the sex-unknown group, 0.869-0.893 in the male, and 0.845-0.855 in the female. The five measurements were found to be better correlated with stature in the male than in the female. The digital X-ray of the tibia and fibula for stature estimation is proved to be effective in forensic individual identification; therefore, these equations can be of great assistance to the stature estimation of the contemporary Chinese Han teenagers.

  12. Length and base composition of PCR-amplified nucleic acids using mass measurements from electrospray ionization mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Muddiman, D.C.; Anderson, G.A.; Hofstadler, S.A.; Smith, R.D. [Pacific Northwest National Lab., Richland, WA (United States)

    1997-04-15

    A generally applicable algorithm has ben developed to allow base composition of polymerase chain reaction (PCR) products to be determined from mass spectrometrically measured molecular weights and the complementary nature of DNA. Mass measurements of arbitrary precision for single-stranded DNA species are compatible with an increasingly large number of possible base compositions as molecular weight increases. For example, the number of base compositions that are consistent with a molecular weight of 35000 is nearly 6000, based on a mass measurement precision of 0.01%. However, given the low misincorporation rate of standard DNA polymerses, mass measurement of both of the complementary single strands produced in the PCR reduces the number of possibilities to less then 100 at 0.01% mass precision, and the base composition is uniquely defined at 0.001% mass precision. Taking into account the low misincorporation rate of standard DNA polymerases and the fact that the final PCR product also contains primers of known sequence (generally 15-20 mer in size, which flank the targeted region), this reduces the number of possible base combinations to only nearly 3 at MW = 35000. In addition, the number of base pairs (i.e., length of the DNA molecule) is uniquely defined. We show that the use of modified bases in PCR or post-PCR modification chemistry allows unique solutions for the base composition of the PCR product with only modest mass measurement precision. 31 refs., 5 figs., 1 tab.

  13. Windowing UWB microwave, mm-wave multi-port S-parameter measurements using open-ended excess electrical length

    Directory of Open Access Journals (Sweden)

    Gholamreza Askari

    2017-05-01

    Full Text Available Multi-port measurements are a big challenge in circuits' verification, especially when the frequency increases. This study presents a new technique for measuring S-parameters of multi-port ultra-wideband (UWB microwave and mm-wave circuits. The concepts are based on direct or indirect applying modulated UWB impulse radio in desired bandwidth to the one port of the modified multi-port circuit and gathering the reflected signal in the same port and the output signal in the second port in time domain, and the other ports are left opened with a special designed added electrical length. Then by applying intelligent windowing in time domain to the gathering data, and using fast Fourier transform, the desired S-parameters are extracted. Validation of this technique is verified by design and fabrication of a three-port UWB Wilkinson power divider in 22–30 GHz. The simulation and measurement results of the reflection and transmission S-parameters by using this new technique are very close to those are extracted with the conventional vector network analysers S-parameters measurements and show the ability and the accuracy of this technique.

  14. Estimation of age by measuring the Root Length of Mandibular Premolars & Permanent Mandibular Molar - A Digital Radiographic Technique

    Directory of Open Access Journals (Sweden)

    R Vishwanath

    2004-01-01

    Full Text Available Developing teeth have been considered as a good indicator for determination of age of an individual with unknown birth data. The common methods employed have been radiographic subjective assessment of tooth development and subsequent comparisons with dental charts. The accuracy of these methods has been questioned since the distribution around an estimated age has been more than ±2 years between 10th and 90th percentile. In an attempt to avoid the short coming associated with the subjective methods, a study of objective measurement of root length of mandibular 2nd premolar and permanent 1st molar by intraoral digital radiographic technique was conducted in the age group of 10-14 years and analyzed statistically using stepwise multiple regression models. It is found that the mandibular premolars can be used for age estimation with fair degree of accuracy between the age of 10-14 years.

  15. Reliability of the two-point measurement of the spatial correlation length from Gaussian-shaped fluctuating signals in fusion-grade plasmas

    CERN Document Server

    Kim, Jaewook; Lampert, M; Ghim, Y -c

    2016-01-01

    A statistical method for the estimation of spatial correlation lengths of Gaussian-shaped fluctuating signals with two measurement points is examined to quantitatively evaluate its reliability (variance) and accuracy (bias error). The standard deviation of the correlation value is analytically derived for randomly distributed Gaussian shaped fluctuations satisfying stationarity and homogeneity, allowing us to evaluate, as a function of fluctuation-to-noise ratios, sizes of averaging time windows and ratios of the distance between the two measurement points to the true correlation length, the goodness of the two-point measurement for estimating the spatial correlation length. Analytic results are confirmed with numerically generated synthetic data and real experimental data obtained with the KSTAR beam emission spectroscopy diagnostic. Our results can be applied to Gaussian-shaped fluctuating signals where a correlation length must be measured with only two measurement points.

  16. NEW DIAGNOSTICS AND CURES FOR COUPLED-BUNCH INSTABILITIES

    Energy Technology Data Exchange (ETDEWEB)

    Teytelman, Dmitry

    2002-08-06

    As circular accelerators move towards larger numbers of bunches and higher beam currents, the task of diagnosing and curing coupled-bunch instabilities becomes ever harder. This paper describes the use of phase space tracking, i.e. reconstruction of bunch phase space trajectories, as a comprehensive instability diagnostic. A new instability cure is also presented, based on recent insights into the dynamics of unevenly-filled rings. Data is shown from PEP-II and the ALS, where ''optimally shaped'' uneven fills have yielded significant increases in instability thresholds.

  17. Developing electron beam bunching technology for improving light sources

    Energy Technology Data Exchange (ETDEWEB)

    Carlsten, B.E.; Chan, K.C.D.; Feldman, D.W. [and others

    1997-08-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project was to develop a new electron bunch compression technology, experimentally demonstrate subpicosecond compression of bunches with charges on the order of 1 nC, and to theoretically investigate fundamental limitations to electron bunch compression. All of these goals were achieved, and in addition, the compression system built for this project was used to generate 22 nm light in a plasma-radiator light source.

  18. Interaction of an ion bunch with a plasma slab

    Energy Technology Data Exchange (ETDEWEB)

    Krasovitskiy, V. B., E-mail: krasovit@mail.ru [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation); Turikov, V. A. [Peoples’ Friendship University of Russia (Russian Federation)

    2016-11-15

    Charge neutralization of a short ion bunch passing through a plasma slab is studied by means of numerical simulation. It is shown that a fraction of plasma electrons are trapped by the bunch under the action of the collective charge separation field. The accelerated electrons generated in this process excite beam−plasma instability, thereby violating the trapping conditions. The process of electron trapping is also strongly affected by the high-frequency electric field caused by plasma oscillations at the slab boundaries. It is examined how the degree of charge neutralization depends on the parameters of the bunch and plasma slab.

  19. The impact of crown-rump length measurement error on combined Down syndrome screening: a simulation study.

    Science.gov (United States)

    Salomon, L J; Bernard, M; Amarsy, R; Bernard, J P; Ville, Y

    2009-05-01

    To evaluate the impact of a 5-mm error in the measurement of crown-rump length (CRL) in a woman undergoing ultrasound and biochemistry sequential combined screening for Down syndrome. Based on existing risk calculation algorithms, we simulated the case of a 35-year-old-woman undergoing combined screening based on nuchal translucency (NT) measurement and early second-trimester maternal serum markers (human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP) expressed as multiples of the median (MoM)). Two measurement errors were considered (+ or - 5 mm), for four different CRLs (50, 60, 70 and 80 mm), with five different NT measurements (1, 1.5, 2, 2.5 and 3 mm) in a patient undergoing biochemistry testing at 14 + 4, 15, 16, 17 or 18 weeks' gestation. Four different values for each maternal serum marker were tested (1, 1.5, 2 and 2.5 MoM for hCG, and 0.5, 0.8, 1 and 1.5 MoM for AFP), leading to a total of 3200 simulations of the impact of measurement error. In all cases the ratio between the risk as assessed with or without the measurement error was calculated (measurement error-related risk ratio (MERR)). Over 3200 simulated cases, MERR ranged from 0.53 to 2.14. In 586 simulations (18.3%), it was 1.33. Based on a risk cut-off of 1/300, women would have been misclassified in 112 simulations (3.5%). This would go up to 33 (27.5%) out of the 120 simulations in women with 'borderline' risk, with 1.5 MoM for hCG and 0.5 MoM for AFP, and NT measurement of 1 or 2mm. Down syndrome screening may be highly sensitive to measurement errors in CRL. Quality control of CRL measurement should be performed together with quality control of NT measurement in order to provide the highest standard of care.

  20. Estimating age from recapture data: integrating incremental growth measures with ancillary data to infer age-at-length

    Science.gov (United States)

    Eaton, Mitchell J.; Link, William A.

    2011-01-01

    Estimating the age of individuals in wild populations can be of fundamental importance for answering ecological questions, modeling population demographics, and managing exploited or threatened species. Significant effort has been devoted to determining age through the use of growth annuli, secondary physical characteristics related to age, and growth models. Many species, however, either do not exhibit physical characteristics useful for independent age validation or are too rare to justify sacrificing a large number of individuals to establish the relationship between size and age. Length-at-age models are well represented in the fisheries and other wildlife management literature. Many of these models overlook variation in growth rates of individuals and consider growth parameters as population parameters. More recent models have taken advantage of hierarchical structuring of parameters and Bayesian inference methods to allow for variation among individuals as functions of environmental covariates or individual-specific random effects. Here, we describe hierarchical models in which growth curves vary as individual-specific stochastic processes, and we show how these models can be fit using capture–recapture data for animals of unknown age along with data for animals of known age. We combine these independent data sources in a Bayesian analysis, distinguishing natural variation (among and within individuals) from measurement error. We illustrate using data for African dwarf crocodiles, comparing von Bertalanffy and logistic growth models. The analysis provides the means of predicting crocodile age, given a single measurement of head length. The von Bertalanffy was much better supported than the logistic growth model and predicted that dwarf crocodiles grow from 19.4 cm total length at birth to 32.9 cm in the first year and 45.3 cm by the end of their second year. Based on the minimum size of females observed with hatchlings, reproductive maturity was estimated

  1. A software program to measure the three-dimensional length of the spine from radiographic images: Validation and reliability assessment for adolescent idiopathic scoliosis.

    Science.gov (United States)

    Berger, Steve; Hasler, Carol-Claudius; Grant, Caroline A; Zheng, Guoyan; Schumann, Steffen; Büchler, Philippe

    2017-01-01

    The aim of this study was to validate a new program which aims at measuring the three-dimensional length of the spine's midline based on two calibrated orthogonal radiographic images. The traditional uniplanar T1-S1 measurement method is not reflecting the actual three dimensional curvature of a scoliotic spine and is therefore not accurate. The Spinal Measurement Software (SMS) is an alternative to conveniently measure the true spine's length. The validity, inter- and intra-observer variability and usability of the program were evaluated. The usability was quantified based on a subjective questionnaire filled by eight participants using the program for the first time. The validity and variability were assessed by comparing the length of five phantom spines measured based on CT-scan data and on radiographic images with the SMS. The lengths were measured independently by each participant using both techniques. The SMS is easy and intuitive to use, even for non-clinicians. The SMS measured spinal length with an error below 2 millimeters compared to length obtained using CT scan datasets. The inter- and intra-observer variability of the SMS measurements was below 5 millimeters. The SMS provides accurate measurement of the spinal length based on orthogonal radiographic images. The software is easy to use and could easily integrate the clinical workflow and replace current approximations of the spinal length based on a single radiographic image such as the traditional T1-S1 measurement. Crown Copyright © 2016. Published by Elsevier Ireland Ltd. All rights reserved.

  2. Measurement of the mass of the top quark using the transverse decay length and lepton transverse momentum techniques

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Christian

    2014-05-02

    A measurement of the mass of the top quark using the transverse momentum of the lepton and decay length of the B-Hadron has been presented. The result is m{sub Top}=(170.4±1.1{sub stat.}±2.3{sub syst.}) GeV. This is compatible with previous measurements of the mass of the top quark, done by either the ATLAS collaboration or other experiments. The total uncertainty on the result of this analysis, Δ{sup total}m{sub Top}=2.6 GeV is larger than results by other measurements. However, with an jet energy scale uncertainty of only Δ{sup Jes}m{sub Top}=0.3 GeV it has one of the smallest uncertainties caused by this source. In a combination of results this will help reducing the total uncertainty on the mass of the top quark. The value of 0.42 on the strength on final state radiation indicates that the simulation underestimates the strength of final state radiation. There is currently work ongoing aiming to publish the results found in this thesis in the context of an official ATLAS publication. Additionally the uncertainties can be compared with those one would obtain by using only one of the two variables. If one considers only the transverse decay length, a statistical error of Δm{sub Top}{sup stat.}=1.7 GeV and a systematic uncertainty of Δm{sub Top}{sup stat.}=7.8 GeV is obtained, dominated by the uncertainty on initial and final state radiation. The statistical uncertainty obtained by using the transverse momentum of the lepton is with Δm{sub Top}{sup stat.}=1.4 GeV a bit lower than the one obtained by the transverse decay length alone but still larger than the one of the presented measurement. The systematic uncertainty obtained is Δm{sub Top}{sup stat.}=2.7 GeV. Combining the two variables is therefore worthwhile compared with using only the transverse momentum of the lepton alone. The dominant uncertainties on the measurement are caused by imperfect knowledge of the simulation parameters, especially the choice of Monte-Carlo generator. Other large

  3. Energy loss and longitudinal wakefield of relativistic short proton bunches in electron clouds

    Directory of Open Access Journals (Sweden)

    O. Boine-Frankenheim

    2012-05-01

    Full Text Available The aim of our study is the numerical computation of the wakefield and energy loss per unit length for relativistic, short (<10  ns proton bunches interacting with an electron cloud inside the beam pipe. We present analytical expressions for the energy loss in the impulse kick approximation. For the simulation of the wakefields a 2D self-consistent, electrostatic particle-in-cell (PIC code is employed. Results for the energy loss and for the wakefields are presented for the parameter scope of the CERN LHC and SPS. For selected parameters the results are compared to a three-dimensional (3D electromagnetic PIC code.

  4. High Charge PHIN Photo Injector at CERN with Fast Phase switching within the Bunch Train for Beam Combination

    CERN Document Server

    Csatari Divall, M; Bolzon, B; Bravin, E; Chevallay, E; Dabrowski, A; Doebert, S; Drozdy, A; Fedosseev, V; Hessler, C; Lefevre, T; Livesley, S; Losito, R; Olvegaard, M; Petrarca, M; Rabiller, A N; Egger, D; Mete, O

    2011-01-01

    The high charge PHIN photo-injector was developed within the framework of the European CARE program to provide an alternative to the drive beam thermionic gun in the CTF3 (CLIC Test Facility) at CERN. In PHIN 1908 electron bunches are delivered with bunch spacing of 1.5 GHz and 2.33 nC charge per bunch. Furthermore the drive beam generated by CTF3 requires several fast 180 deg phase-shifts with respect to the 1.5 GHz bunch repetition frequency in order to allow the beam combination scheme developed at CTF3. A total of 8 subtrains, each 140 ns long and shifted in phase with respect to each other, have to be produced with very high phase and amplitude stability. A novel fiber modulator based phase-switching technique developed on the laser system provides this phase-shift between two consecutive pulses much faster and cleaner than the base line scheme, where a thermionic electron gun and sub-harmonic bunching are used. The paper describes the fiber-based switching system and the measurements verifying the schem...

  5. The Fast Vertical Single-Bunch Instability after Injection into the CERN Super Proton Synchrotron

    CERN Document Server

    Métral, Elias; Bohl, Thomas; Burkhardt, Helmut; Rumolo, Giovanni; Spataro, Bruno; CERN. Geneva

    2006-01-01

    Since 2003, high-intensity single-bunch proton beams with low longitudinal emittance have been affected by heavy losses after less than one synchrotron period after injection. The effects of the resonance frequency of the responsible impedance, longitudinal emittance and chromaticity on the intensity threshold were already discussed in detail in 2004, comparing analytical predictions with simulation results. In this paper the evolution of the instability between injection and the time of beam loss is our main concern. Measurements are compared with HEADTAIL simulations. A travellingwave pattern propagating along the bunch, which is the signature of a Beam Break-Up or Transverse Mode Coupling Instability (TMCI), is clearly identified. The oscillating frequency, near ~1 GHz, is in good agreement with the usual broad-band impedance model deduced from beam-based measurements like the head-tail growth rate vs. chromaticity.

  6. Investigation of transient processes at the DELTA electron storage ring using a digital bunch-by-bunch feedback system

    Energy Technology Data Exchange (ETDEWEB)

    Hoener, Markus

    2015-07-01

    At the 1.5-GeV synchrotron radiation source DELTA, operated by the TU Dortmund University, intensive synchrotron radiation in the spectral range from hard X-rays to THz radiation is generated by the circular deflection of highly relativistic electron bunches. Interacting with the vacuum chamber wall, the electron bunches create electric fields, which can act back on subsequent bunches. With increasing beam current, the excitation is enhanced so that the electron beam is unstable, which means that the electron bunches oscillate longitudinally or transversely relative to their reference position. The oscillations reduce the quality of the synchrotron radiation and limit the maximum storable beam current. Within the scope of this thesis, the beam instabilities at the storage ring were systematically investigated. A digital bunch-by-bunch feedback system was installed and commissioned, which allows to detect and digitize the position of each electron bunch at each turn. Based on the input signal, a correction signal is calculated in order to suppress transverse and longitudinal oscillation of the bunches. In addition, it is possible to excite dedicated bunches. The systematic excitation of all coupled-bunch modes allowed for the first time to determine the damping rates of all 192 eigenmodes of the electron beam. The current dependence of the damping rates was investigated and an instability threshold was found. Besides the investigation of multibunch instabilities, single-bunch instabilities are discussed. In addition, the acquisition unit of the digital feedback system can be triggered on external events. This was used to investigate the injection process and beam losses. It was shown that the transverse feedback system increases the injection efficiency. Another aspect of this thesis is the improvement of the signal quality of ultrashort coherent synchrotron radiation pulses, which are generated by the short-pulse facility at DELTA. The short-pulse facility is based

  7. Temporal intensity interferometry: photon bunching in three bright stars

    Science.gov (United States)

    Guerin, W.; Dussaux, A.; Fouché, M.; Labeyrie, G.; Rivet, J.-P.; Vernet, D.; Vakili, F.; Kaiser, R.

    2017-12-01

    We report the first intensity correlation measured with starlight since the historical experiments of Hanbury Brown and Twiss. The photon bunching g(2)(τ, r = 0), obtained in the photon-counting regime, was measured for three bright stars: α Boo, α CMi and β Gem. The light was collected at the focal plane of a 1-m optical telescope, transported by a multi-mode optical fibre, split into two avalanche photodiodes and correlated digitally in real time. For total exposure times of a few hours, we obtained contrast values around 2 × 10-3, in agreement with the expectation for chaotic sources, given the optical and electronic bandwidths of our set-up. Comparing our results with the measurement of Hanbury Brown et al. for α CMi, we argue for the timely opportunity to extend our experiments to measuring the spatial correlation function over existing and/or foreseen arrays of optical telescopes diluted over several kilometres. This would enable microarcsec long-baseline interferometry in the optical, especially in the visible wavelengths, with a limiting magnitude of 10.

  8. Phase modulation of the bucket stops bunch oscillations at the Fermilab Tevatron

    Energy Technology Data Exchange (ETDEWEB)

    Tan, C.Y.; Burov, A.; /Fermilab

    2012-04-02

    Bunches in the Tevatron are known to exhibit longitudinal oscillations which persist indefinitely. These oscillations are colloquially called 'dancing bunches.' Although the dancing proton bunches do not cause single bunch emittance growth or beam loss at injection, they lead to bunch lengthening at collisions. In Tevatron operations, a longitudinal damper has been built which stops this dance and damps out coupled bunch modes. Recent theoretical work predicts that the dance can also be stopped by an appropriate change in the bunch distribution. This paper describes the Tevatron experiments which support this theory.

  9. Wake excited in plasma by an ultrarelativistic pointlike bunch

    Science.gov (United States)

    Stupakov, G.; Breizman, B.; Khudik, V.; Shvets, G.

    2016-10-01

    We study propagation of a relativistic electron bunch through a cold plasma assuming that the transverse and longitudinal dimensions of the bunch are much smaller than the plasma collisionless skin depth. Treating the bunch as a point charge and assuming that its charge is small, we derive a simplified system of equations for the plasma electrons and show that, through a simple rescaling of variables, the bunch charge can be eliminated from the equations. The equations demonstrate an ion cavity formed behind the driver. They are solved numerically and the scaling of the cavity parameters with the driver charge is obtained. A numerical solution for the case of a positively charged driver is also found.

  10. Precision Control of the Electron Longitudinal Bunch Shape Using an Emittance-Exchange Beam Line.

    Science.gov (United States)

    Ha, G; Cho, M H; Namkung, W; Power, J G; Doran, D S; Wisniewski, E E; Conde, M; Gai, W; Liu, W; Whiteford, C; Gao, Q; Kim, K-J; Zholents, A; Sun, Y-E; Jing, C; Piot, P

    2017-03-10

    We report on the experimental generation of relativistic electron bunches with a tunable longitudinal bunch shape. A longitudinal bunch-shaping (LBS) beam line, consisting of a transverse mask followed by a transverse-to-longitudinal emittance exchange (EEX) beam line, is used to tailor the longitudinal bunch shape (or current profile) of the electron bunch. The mask shapes the bunch's horizontal profile, and the EEX beam line converts it to a corresponding longitudinal profile. The Argonne wakefield accelerator rf photoinjector delivers electron bunches into a LBS beam line to generate a variety of longitudinal bunch shapes. The quality of the longitudinal bunch shape is limited by various perturbations in the exchange process. We develop a simple method, based on the incident slope of the bunch, to significantly suppress the perturbations.

  11. Effect of pre-analytic variables on the reproducibility of qPCR relative telomere length measurement.

    Directory of Open Access Journals (Sweden)

    Casey L Dagnall

    Full Text Available Telomeres, long nucleotide repeats and a protein complex at chromosome ends, shorten with each cell division and are susceptible to oxidative damage. Quantitative PCR (qPCR is a widely-used technique to measure relative telomere length (RTL in DNA samples but is challenging to optimize and significant lab-to-lab variability has been reported. In this study, we evaluated factors that may contribute to qPCR RTL measurement variability including DNA extraction methods, methods used for removing potential residual PCR inhibitors, sample storage conditions, and sample location in the PCR plate. Our results show that the DNA extraction and purification techniques, as well as sample storage conditions introduce significant variability in qPCR RTL results. We did not find significant differences in results based on sample location in the PCR plate or qPCR instrument used. These data suggest that lack of reproducibility in published association studies of RTL could be, in part, due to methodological inconsistencies. This study illustrates the importance of uniform sample handling, from DNA extraction through data generation and analysis, in using qPCR to determine RTL.

  12. Measurement and Analysis of Axial End Forces in a Full-Length Prototype of LHC Main Dipole Magnets

    CERN Document Server

    Artoos, K; Savary, F; Valbuena, R; Vlogaert, J

    2000-01-01

    A full-length, twin aperture prototype (MBP2N1) dipole magnet for the LHC project was assembled at CERN with collared coils delivered by industry. The design of this prototype is close to that foreseen for the dipole series manufacture as far the coil geometry and that of the yoke components are concerned. The bolts that transfer the axial magnetic forces from the coil ends to the cold mass end plates were instrumented to verify the axial coil support. These axial forces were initially measured after partial assembly, during a standard and an accelerated cool down Introduction to 1.9 K, and during magnet excitation up to 9.2 T. High force levels were observed, triggering a comparison with analytical models and measurements routinely made on 1-m single aperture dipole models. The prototype magnet was re-assembled with lower initial axial force settings and with additional instrumentation, to monitor these forces during the entire assembly process, and re-tested, to possibly correlate axial forces with training...

  13. Dependence of bunch energy loss in cavities on beam velocity

    Directory of Open Access Journals (Sweden)

    Sergey S. Kurennoy

    1999-03-01

    Full Text Available Beam energy loss in a cavity can be easily computed for a relativistic bunch using time-domain codes like MAFIA or ABCI. However, for nonrelativistic beams the problem is more complicated because of difficulties with its numerical formulation in the time domain. We calculate the cavity loss factors for a bunch in frequency domain as a function of its velocity and compare results with the relativistic case.

  14. Transverse C-band deflecting structure for longitudinal electron-bunch-diagnosis in XFEL “SACLA”

    Energy Technology Data Exchange (ETDEWEB)

    Ego, H., E-mail: ego@spring8.or.jp [Japan Synchrotron Radiation Research Institute (JASRI), Kouto, Sayo, Hyogo (Japan); Maesaka, H.; Sakurai, T.; Otake, Y. [RIKEN SPring-8 Center, Kouto, Sayo, Hyogo (Japan); Hashirano, T.; Miura, S. [Mitsubishi Heavy Industries, Ltd. (MHI), Itozaki, Mihara, Hiroshima (Japan)

    2015-09-21

    In the 8 GeV compact X-ray FEL “SACLA,” a single bunch of electrons is compressed to a duration of approximately 30 fs to yield a peak current of 3 kA, which creates brilliant self-amplified spontaneous emission. To measure the longitudinal profile of an ultrashort electron bunch and verify the compression, we developed a high-gradient C-band RF deflecting structure 1.8 m long and periodically loaded with racetrack-shaped irises. The irises generated a high deflection gradient for the vertically deflecting HEM11-5π/6 dipole mode and suppressed rotation of the deflection plane. The two structures were fabricated and generated a stable total deflecting voltage exceeding 60 MV and revealed the longitudinal electron-bunch profile with an effective time resolution of approximately 10 fs.

  15. Bunched release of gases from oxide targets

    CERN Document Server

    Ravn, H L; Evensen, A H M; Jonsson, O C; Kugler, E; Lettry, Jacques; Tengblad, O; Barker, J; Drumm, P V; Hagebø, E; Hoff, P; Steffensen, K

    1997-01-01

    Targets made out of oxides of the alkaline earth metals have been shown at ISOLDE to be among the fastest targets for production of radioactive beams of the rare gas elements. In addition oxide target materials release nitrogen and seem to be the only ones which may release the element carbon due to its oxidation to the high temperature stable CO gas. Thick targets of MgO and CaO have been studied in connection with their use at the 1GeV pulsed proton beam from the PS-BOOSTER synchrotron. It is shown that the 2.4$\\mu$s short proton pulse causes a pronounced bunched release with short delay of these elements which gives rise to 100-200 ms wide pulses of radioactive ion beams. Pulse shapes and overall yields of ion beams of He, Ne and Ar isotopes are studied as function of temperature and proton pulse intensity. For carbon and nitrogen also the release as function of the observed ionic species C$^+$, CO$^+$, N$^+$ and N$_2^+$ is discussed.

  16. The LHC Transverse Coupled-Bunch Instability

    CERN Document Server

    Mounet, Nicolas; Métral, Elias

    In this thesis, the problem of the transverse coupled-bunch instabilities created by the Large Hadron Collider (LHC) beam-coupling impedance, that can possibly limit the machine operation, is addressed thanks to several new theories and tools. A rather complete vision of the problem is proposed here, going from the calculation of the impedances and wake functions of individual machine elements, to the beam dynamics study. Firstly, new results are obtained in the theory of the beam-coupling impedance for an axisymmetric two-dimensional structure, generalizing Zotter's theories, and a new general theory is derived for the impedance of an infinite flat two-dimensional structure. Then, a new approach has been found to compute the wake functions from such analytically obtained beam-coupling impedances, over-coming limitations that could be met with standard discrete Fourier transform procedures. Those results are then used to obtain an impedance and wake function model of the LHC, based on the (resistive-) wall im...

  17. Architecture and technology of 500 Msample/s feedback systems for control of coupled-bunch instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Teytelman, Dmitry

    2000-03-30

    Feedback control of coupled-bunch instabilities presents many challenges. Control bandwidths up to 250 MHz are required to damp all of the unstable coupled-bunch modes in recent accelerators. A digital parallel-processing array with 80 DSPs has been developed to control longitudinal instabilities in PEP-II/ALS/DA NE machines. Here the authors present a description of the architecture as well as the technologies used to implement 500 Msample/s real-time control system with 2,000 FIR filtering channels. Algorithms for feedback control, data acquisition, and analysis are described and measurements from ALS are presented.

  18. Development of a high-speed digital signal process system for bunch-by-bunch feedback systems

    Directory of Open Access Journals (Sweden)

    Makoto Tobiyama

    2000-01-01

    Full Text Available High-speed digital filter systems for bunch-by-bunch feedback systems have been developed at KEK. A two-tap finite impulse response filter with simple hardware realizes the functions of a 90° phase shift, suppression of the static component and digital delay of up to a few hundred turns for the KEKB rings. Difficulties in the circuit board, such as the trimming of the timing skews or the problem of long-term reliability, have been solved using custom GaAs large-scale integrated circuits which demultiplex and multiplex fast parallel-digital data coming from the analog-to-digital converter and going to the digital-to-analog converter. Two major applications of the filter board, the bunch current monitor and the bunch oscillation recorder with 20 MB memories for transient-domain analysis of the instabilities, are also described.

  19. Electron bunch timing with femtosecond precision in a superconducting free-electron laser.

    Science.gov (United States)

    Löhl, F; Arsov, V; Felber, M; Hacker, K; Jalmuzna, W; Lorbeer, B; Ludwig, F; Matthiesen, K-H; Schlarb, H; Schmidt, B; Schmüser, P; Schulz, S; Szewinski, J; Winter, A; Zemella, J

    2010-04-09

    High-gain free-electron lasers (FELs) are capable of generating femtosecond x-ray pulses with peak brilliances many orders of magnitude higher than at other existing x-ray sources. In order to fully exploit the opportunities offered by these femtosecond light pulses in time-resolved experiments, an unprecedented synchronization accuracy is required. In this Letter, we distributed the pulse train of a mode-locked fiber laser with femtosecond stability to different locations in the linear accelerator of the soft x-ray FEL FLASH. A novel electro-optic detection scheme was applied to measure the electron bunch arrival time with an as yet unrivaled precision of 6 fs (rms). With two beam-based feedback systems we succeeded in stabilizing both the arrival time and the electron bunch compression process within two magnetic chicanes, yielding a significant reduction of the FEL pulse energy jitter.

  20. A linear radiofrequency quadrupole ion trap for the cooling and bunching of radioactive ion beams

    CERN Document Server

    Kellerbauer, A G; Dilling, J; Henry, S; Herfurth, F; Kluge, H J; Lamour, E; Moore, R B; Scheidenberger, C; Schwarz, S; Sikler, G; Szerypo, J

    2002-01-01

    A linear radiofrequency quadrupole ion guide and beam buncher has been installed at the ISOLTRAP mass spectrometry experiment at the ISOLDE facility at CERN. The apparatus is being used as a beam cooling, accumulation, and bunching system. It operates with a buffer gas that cools the injected ions and converts the quasicontinuous 60- keV beam from the ISOLDE facility to 2.5-keV beam pulses with improved normalized transverse emittance. Recent measurements suggest a capture efficiency of the ion guide of up to 40% and a cooling and bunching efficiency of at least 12% which is expected to still be increased. The improved ISOLTRAP setup has so far been used very successfully in three on-line experiments. (12 refs).

  1. Cervical length measurement for the prediction of preterm birth in multiple pregnancies : a systematic review and bivariate meta-analysis

    NARCIS (Netherlands)

    Lim, A. C.; Hegeman, M. A.; In 't Veld, M. A. Huis; Opmeer, B. C.; Bruinse, H. W.; Mol, B. W. J.

    Objectives To review the literature on cervical length as a predictor of preterm birth in asymptomatic women with a multiple pregnancy. Methods We searched MEDLINE, Embase and reference lists of included articles to identify all studies that reported on the accuracy of cervical length for predicting

  2. Inter-laboratory validation of the measurement of follicle stimulating hormone (FSH after various lengths of frozen storage

    Directory of Open Access Journals (Sweden)

    Behr Barry

    2010-11-01

    Full Text Available Abstract Background Serum follicle stimulating hormone (FSH levels are used clinically to evaluate infertility, pituitary and gonadal disorders. With increased frequency of research collaborations across institutions, it is essential that inter-laboratory validation is addressed. Methods An inter-laboratory validation of three commercial FSH immunoassays was performed with human serum samples of varying frozen storage length (2 batches of 15 samples each at -25 degree C. Percentage differences and Bland-Altman limits of agreement were calculated. Results The inter- and intra-laboratory consistency of FSH values with the same assay manufacturer was much higher after shorter-term storage (frozen for less than 11 months, mean percentage degradation less than 4% than after long-term storage (2-3 years, mean percentage degradation = 23%. Comparing assay results from different manufacturers, there was similar overall long term degradation as seen with the same manufacturer (-25%, however the degradation was greater when the original FSH was greater than 20 mIU/mL relative to less than 10 mIU/mL (p Conclusion The findings suggest that degradation of serum samples stored between 11 months and 2-3 years at -25 degrees C can lead to unstable FSH measurements. Inter-laboratory variability due to frozen storage time and manufacturer differences in assay results should be accounted for when designing and implementing research or clinical quality control activities involving serum FSH at multiple study sites.

  3. Neural measures of a Japanese consonant length discrimination by Japanese and American English listeners: Effects of attention.

    Science.gov (United States)

    Hisagi, Miwako; Shafer, Valerie L; Strange, Winifred; Sussman, Elyse S

    2015-11-11

    This study examined automaticity of discrimination of a Japanese length contrast for consonants (miʃi vs. miʃʃi) in native (Japanese) and non-native (American-English) listeners using behavioral measures and the event-related potential (ERP) mismatch negativity (MMN). Attention to the auditory input was manipulated either away from the auditory input via a visual oddball task (Visual Attend), or to the input by asking the listeners to count auditory deviants (Auditory Attend). Results showed a larger MMN when attention was focused on the consonant contrast than away from it for both groups. The MMN was larger for consonant duration increments than decrements. No difference in MMN between the language groups was observed, but the Japanese listeners did show better behavioral discrimination than the American English listeners. In addition, behavioral responses showed a weak, but significant correlation with MMN amplitude. These findings suggest that both acoustic-phonetic properties and phonological experience affects automaticity of speech processing. This article is part of a Special Issue entitled SI: Prediction and Attention. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Optimization of a train of bunches for plasma wakefield acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Martorelli, Roberto

    2016-05-10

    Particle accelerators are a fundamental instrument for the understanding of fundamental mechanism in nature. The need of always higher energies for the particle beams requires a huge increase of the sizes of the accelerators using the actual technology. Moreover the highest energies are achieved nowadays by circular colliders, not perfectly suitable for acceleration of electrons and positrons due to the radiation losses. In order to overcome this problem a new branch of physics studying alternative technique for particle acceleration has been developed. Among the various alternatives a promising one is the plasma wakefield acceleration (PWFA), in which a driver bunch interacts with a cold background plasma, exciting a plasma wave. The electric field of the plasma wave is then used for the acceleration of a second bunch. Such a mechanism allows to reach fields strength far beyond currently available, limited by the dielectric strength of the material. Among the different driver configurations, a promising one is the use of a modulated beam, namely a train of bunches, that provides a coherent interference among the electric fields generated by the single bunches. Such mechanism is subjected to a renewed interest in view of the forthcoming AWAKE experiment at CERN in which the long proton beam produced at the SPS facility is used as a driver. This possibility is achieved thanks to the onset of the self-modulation instability that modulates the long beam in a train of approximately 100 bunches. In order to accelerate the witness bunch to high energies is necessary on the other hand an efficient exchange of energy from the driver to the accelerated bunch, as well as a long duration of the driver so that can propagates for kilometers. This thesis deals with this two last aspects. The aim of this work is to provide an optimization for the modulated driver in order to improve specific features of the PWFA. This work shows the possibility to achieve an improved efficiency

  5. Architectures and Algorithms for Control and Diagnostics of Coupled-Bunch Instabilities in Circular Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Teytelman, Dmitry

    2003-07-08

    Modern light sources and circular colliders employ large numbers of high-intensity particle bunches in order to achieve high luminosity. The electromagnetic coupling of bunches via resonant structures causes coherent instabilities at high beam currents. Achieving high luminosity requires the control of such unstable motion. Feedback control is challenging due to wideband nature of the problem with up to 250 MHz bandwidths required. This thesis presents digital signal processing architectures and diagnostic techniques for control of longitudinal and transverse coupled-bunch instabilities. Diagnostic capabilities integrated into the feedback system allow one to perform fast transient measurements of unstable dynamics by perturbing the beam from the controlled state via feedback and recording the time-domain response. Such measurements enable one to thoroughly characterize plant (beam) dynamics as well as performance of the feedback system. Beam dynamics can change significantly over the operating range of accelerator currents and energies . Here we present several methods for design of robust stabilizing feedback controllers. Experimental results from several accelerators are presented. A new baseband architecture for transverse feedback is described that compactly implements the digital processing functions using field-programmable gate array devices. The architecture is designed to be software configurable so that the same hardware can be used for instability control in different accelerators.

  6. Path length resolved Doppler measurements of multiple scattered photons in turbid media for various absorptions using phase modulated low-coherence interferometry

    Science.gov (United States)

    Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G.; Steenbergen, Wiendelt

    2006-04-01

    We report the development of non-invasive, path length resolved Doppler measurements of the multiply scattered light in turbid media, for different absorptions using phase modulated Mach-Zehnder low coherence interferometer, with separate fibers for illumination and detection. A Doppler broadened phase modulation interference peak is observed that shows an increase in the average Doppler shift with optical path length, independent of absorption. The estimated path length distributions indicate suppression and narrowing for increasing absorption and can be related by Lambert-Beer's law.

  7. Investigation of the phase space distribution of electron bunches at the FLASH-linac using a transverse deflecting structure

    Energy Technology Data Exchange (ETDEWEB)

    Roehrs, M.

    2008-06-15

    The operation of a high-gain free-electron laser (FEL) puts stringent demands on the peak current, transverse emittance and energy spread of the electron beam. At the Free Electron Laser in Hamburg (FLASH), a transverse deflecting structure (TDS) has been installed to investigate these electron beam parameters. The radio-frequency electromagnetic field in the TDS is utilized to deflect the beam electrons vertically as a function of time so that the charge distribution in the longitudinal-horizontal plane can be imaged with optical transition radiation screens. Using this technique, the single-bunch current profile was measured with an unprecedented resolution of about 10 {mu}m (30 fs) under FEL operating conditions. A precise single-shot measurement of the energy distribution along a bunch was accomplished by using the TDS in combination with an energy spectrometer. Appropriate variations of the focal strengths of quadrupole magnets allowed for the measurement of the horizontal emittance as a function of the longitudinal position within a bunch (slice emittance) with a longitudinal resolution in the order of 10 {mu}m. While the slice emittance in the peak current region was measured to be significantly larger than deduced from properties of the FEL radiation, tomographic methods revealed a bunch region of small horizontal emittance and high current. The observed increase in slice emittance in the peak current region was found to be caused by coherent emission of synchrotron radiation within bending magnets. (orig.)

  8. Length of Utterance, in Morphemes or in Words?: MLU3-w, a Reliable Measure of Language Development in Early Basque

    Directory of Open Access Journals (Sweden)

    Maria-José Ezeizabarrena

    2018-01-01

    Full Text Available The mean length of utterace (MLU, which was proposed by Brown (1973 as a better index for language development in children than age, has been regularly reported in case studies as well as in cross-sectional studies on early spontaneous language production. Despite the reliability of MLU as a measure of (morpho-syntactic development having been called into question, its extensive use in language acquisition studies highlights its utility not only for intra- and inter-individual comparison in monolingual language acquisition, but also for cross-linguistic assessment and comparison of bilinguals' early language development (Müller, 1993; Yip and Matthews, 2006; Meisel, 2011. An additional issue concerns whether MLU should be measured in words (MLU-w or morphemes (MLU-m, the latter option being the most difficult to gauge, since new challenges have arisen regarding how to count zero morphemes, suppletive and fused morphemes. The different criteria have consequences, especially when comparing development in languages with diverging morphological complexity. A variant of MLU, the MLU3, which is calculated out of the three longest sentences produced (MLU3-w and MLU3-m, is included among the subscales of expressive language development in CDI parental reports (Fenson et al., 1993, 2007. The aim of the study is to investigate the consistency and utility of MLU3-w and MLU3-m as a measure for (morpho-syntactic development in Basque, an agglutinative language. To that end, cross-sectional data were obtained using either the Basque CDI-2 instrument (16- to 30-month-olds or the Basque CDI-3 (30- to 50-month-olds. The results of analyzing reports on over 1,200 children show three main findings. First, MLU3-w and MLU3-m can report equally well on very young children's development. Second, the strong correlations found between MLU3 and expressive vocabulary in the Basque CDI-2 and CDI-3 instruments, as well as between MLU3 and both nominal and verbal morphology

  9. Early transverse decoherence of bunches with space charge

    Directory of Open Access Journals (Sweden)

    Ivan Karpov

    2016-12-01

    Full Text Available The transverse decoherence of injected bunches is an important phenomenon in synchrotrons and storage rings. The initial stage of this process determines the transverse emittance blowup, which should be taken into account for the design of feedback systems, for example. The interplay of different high-intensity effects can strongly affect the initial decoherence stage. We present a model that explains decoherence and emittance growth with chromaticity, space charge, and image charges within the first synchrotron period. We compare the model for different combinations of parameters with self-consistent particle tracking simulations and measurements in the SIS18 synchrotron at GSI Darmstadt. Generally, space charge slows down the decoherence process and can cause the loss of decoherence. Chromaticity and image charges can partly compensate this loss and restore the decoherence. We also analyze the single-particle excitation driven by space charge during the decoherence process. Particles gain large amplitudes from the coherent beam oscillation, which leads to halo buildup and losses.

  10. Application of Metal-Semiconductor-Metal (MSM) Photodetectors for Transverse and Longitudinal Intra-Bunch Beam Diagnostics

    CERN Document Server

    Steinhagen, R J; Boland, M J; Lucas, T G; Rassool, R P

    2013-01-01

    The performance reach of modern accelerators is often governed by the ability to reliably measure and control the beam stability. In high-brightness lepton and high-energy hadron accelerators, the use of optical diagnostic techniques is becoming more widespread as the required bandwidth, resolution and high RF beam power level involved limit the use of traditional electro-magnetic RF pick-up based methods. This contribution discusses the use of fibre-coupled ultra-fast Metal-Semiconductor-Metal Photodetectors (MSM-PD) as an alternative, dependablemeans to measure signals derived from electro-optical and synchrotron-light based diagnostics systems. It describes the beam studies performed at CERN’s CLIC Test Facility (CTF3) and the Australian Synchrotron to assess the feasibility of this technology as a robust, wide-band and sensitive technique for measuring transverse intra-bunch and bunch-by-bunch beam oscillations, longitudinal beam profiles, un-bunched beam population and beam-halo profiles. The amplifica...

  11. Step Bunching: Influence of Impurities and Solution Flow

    Science.gov (United States)

    Chernov, A. A.; Vekilov, P. G.; Coriell, S. R.; Murray, B. T.; McFadden, G. B.

    1999-01-01

    Step bunching results in striations even at relatively early stages of its development and in inclusions of mother liquor at the later stages. Therefore, eliminating step bunching is crucial for high crystal perfection. At least 5 major effects causing and influencing step bunching are known: (1) Basic morphological instability of stepped interfaces. It is caused by concentration gradient in the solution normal to the face and by the redistribution of solute tangentially to the interface which redistribution enhances occasional perturbations in step density due to various types of noise; (2) Aggravation of the above basic instability by solution flowing tangentially to the face in the same directions as the steps or stabilization of equidistant step train if these flows are antiparallel; (3) Enhanced bunching at supersaturation where step velocity v increases with relative supersaturation s much faster than linear. This v(s) dependence is believed to be associated with impurities. The impurities of which adsorption time is comparable with the time needed to deposit one lattice layer may also be responsible for bunching; (4) Very intensive solution flow stabilizes growing interface even at parallel solution and step flows; (5) Macrosteps were observed to nucleate at crystal corners and edges. Numerical simulation, assuming step-step interactions via surface diffusion also show that step bunching may be induced by random step nucleation at the facet edge and by discontinuity in the step density (a ridge) somewhere in the middle of a face. The corresponding bunching patterns produce the ones observed in experiment. The nature of step bunching generated at the corners and edges and by dislocation step sources, as well as the also relative importance and interrelations between mechanisms 1-5 is not clear, both from experimental and theoretical standpoints. Furthermore, several laws controlling the evolution of existing step bunches have been suggested, though

  12. Simple method for generating adjustable trains of picosecond electron bunches

    Directory of Open Access Journals (Sweden)

    P. Muggli

    2010-05-01

    Full Text Available A simple, passive method for producing an adjustable train of picosecond electron bunches is demonstrated. The key component of this method is an electron beam mask consisting of an array of parallel wires that selectively spoils the beam emittance. This mask is positioned in a high magnetic dispersion, low beta-function region of the beam line. The incoming electron beam striking the mask has a time/energy correlation that corresponds to a time/position correlation at the mask location. The mask pattern is transformed into a time pattern or train of bunches when the dispersion is brought back to zero downstream of the mask. Results are presented of a proof-of-principle experiment demonstrating this novel technique that was performed at the Brookhaven National Laboratory Accelerator Test Facility. This technique allows for easy tailoring of the bunch train for a particular application, including varying the bunch width and spacing, and enabling the generation of a trailing witness bunch.

  13. Minimizing Slope and Kick of Intermediate Bunches for Electron Cooling

    Science.gov (United States)

    Dotson, Andrew

    2017-09-01

    Ions in the Jefferson Lab Electron-Ion Collider (JLEIC) will have transverse energy, which limits the beams density. Electron cooling is a process by which a beam of bunched electrons with small transverse kinetic energy is directed along the ion beam with the same velocity. The ions transfer their transverse kinetic energy to the electron bunches, making the ions lose transverse energy. Electron bunches will be supplied by an electron gun. The required current needed to cool the ion beam can be reached by reusing electrons and incorporating RF kicker cavities to supply a pulsed electric field that kicks every 11th bunch out of the cooling ring. This provides an exact solution that yields zero kick and slope to all intermediate bunches in the cooling ring, which is described by a cosine series with 11 terms. The goal of this project is to determine if solutions exist that are sufficiently close to zero kick and slope, but require less than 4 kicker cavities. The method used to find these solutions is minimizing an objective function through Sequential Least Squares Programming (SLSQP). A Pareto front then demonstrated the average kick vs. average slope when using 1 through 4 kickers.

  14. Investigating the Feasibility of a Travelling-wave Chopper for the Clean Separation of 10 MHz Bunches at HIE-ISOLDE

    CERN Document Server

    Mukhopadhyay, A; Calaga, R; Caspers, F; Paoluzzi, M

    2014-01-01

    The feasibility of cleanly separating the main 10.128MHz bunches from the 101.28MHz satellite bunches with a travelling-wave type chopper at HIE-ISOLDE was investigated using a simple model comprising a chain of synchronised capacitors pulsed at high-voltage. Even with a relatively large transverse aperture of 30mm it appears feasible to remove the satellite bunches spaced at 75mm without significantly perturbing the main bunch. We estimate that for a chopping voltage of 1.2 kV a string of 20 capacitors is required to impart the required deflection of 4 mrad to beams with A=q = 4:5 and the mechanical length of the system can be kept under 0.5 m. The deflection imparted on the main pulse is . 1% of that received by the discarded satellite bunches and the transverse emittance growth of the beam is small if the rise/fall times are kept below 5 ns. The HIE-ISOLDE specification is similar to the specification of the meander strip-line chopper developed at CERN for Linac4 and the application of this technology at ...

  15. New method of estimating wavelength-dependent optical path length ratios for oxy- and deoxyhemoglobin measurement using near-infrared spectroscopy.

    Science.gov (United States)

    Umeyama, Shinji; Yamada, Toru

    2009-01-01

    In near-infrared spectroscopy (NIRS), concentration changes in oxy- and deoxyhemoglobin are calculated using an attenuation change of the measurement light and by solving a linear equation based on the modified Lambert-Beer law. While solving this equation, we need to know the wavelength-dependent mean optical path lengths of the measurement lights. However, it is very difficult to know these values by a continuous-wave-type (CW-type) system. We propose a new method of estimating wavelength-dependent optical path length ratios of the measurement lights based on the data obtained by a triple wavelength CW-type NIRS instrument. The proposed method does not give a path length itself, but it gives a path length ratio. Thus, it is possible to obtain the accurate hemoglobin concentration changes without cross talk, although the method cannot contribute to the quantification of the absolute magnitude of hemoglobin changes. The method is based on the principle that two possible estimations of hemoglobin concentration changes calculated using a triple-wavelength measurement system should be identical. The method was applied to the experimental data of human subjects' foreheads. The estimated path length ratios were very similar to literature values obtained by using picosecond laser pulses and a streak camera detector [M. Essenpreis et al., Appl. Opt. 32(4), 418-425 (1993)].

  16. Discrimination between Doppler-shifted and non-shifted light in coherence domain path length resolved measurements of multiply scattered light.

    Science.gov (United States)

    Varghese, B; Rajan, V; van Leeuwen, T G; Steenbergen, W

    2007-10-01

    We show a novel technique to distinguish between Doppler shifted and unshifted light in multiple scattering experiments on mixed static and dynamic media. With a phase modulated low coherence Mach- Zehnder interferometer, optical path lengths of shifted and unshifted light and path length dependent Doppler broadening are measured in a two-layer tissue phantom, with a superficial static layer of different thickness covering a semi-infinite dynamic medium having identical optical properties. No Doppler broadening is observed until a certain optical path length depending on the thickness of the superficial static layer. From the minimum optical path length corresponding to the Doppler-shifted light the thickness of the static layer that overlies the dynamic layer can be estimated. Validation of the experimentally determined thickness of the static layer is done with the Doppler Monte Carlo technique. This approach has potential applications in discriminating between statically and dynamically scattered light in the perfusion signal and in determining superficial burn depths.

  17. Emittance growth due to static and radiative space charge forces in an electron bunch compressor

    Directory of Open Access Journals (Sweden)

    Richard Talman

    2009-01-01

    Full Text Available Evolution of short intense electron bunches passing through bunch-compressing beam lines is studied using the UAL (Unified Accelerator Libraries string space charge formulation [R. Talman, Phys. Rev. ST Accel. Beams 7, 100701 (2004PRABFM1098-440210.1103/PhysRevSTAB.7.100701; N. Malitsky and R. Talman, in Proceedings of the 9th European Particle Accelerator Conference, Lucerne, 2004 (EPS-AG, Lucerne, 2004; R. Talman, Accelerator X-Ray Sources (Wiley-VCH, Weinheim, 2006, Chap. 13]. Three major configurations are studied, with the first most important and studied in greatest detail (because actual experimental results are available and the same results have been simulated with other codes: (i Experimental bunch compression results were obtained at CTF-II, the CERN test facility for the “Compact Linear Collider” using electrons of about 40 MeV. Previous simulations of these results have been performed (using TraFiC4* [A. Kabel et al., Nucl. Instrum. Methods Phys. Res., Sect. A 455, 185 (2000NIMAER0168-900210.1016/S0168-9002(0000729-4] and ELEGANT [M. Borland, Argonne National Laboratory Report No. LS-287, 2000]. All three simulations are in fair agreement with the data except that the UAL simulation predicts a substantial dependence of horizontal emittance ϵ_{x} on beam width (as controlled by the lattice β_{x} function at the compressor location. This is consistent with the experimental observations, but inconsistent with other simulations. Excellent agreement concerning dependence of bunch energy loss on bunch length and magnetic field strength [L. Groening et al., in Proceedings of the Particle Accelerator Conference, Chicago, IL, 2001 (IEEE, New York, 2001, http://groening.home.cern/groening/csr_00.htm] confirms our understanding of the role played by coherent synchrotron radiation (CSR. (ii A controlled comparison is made between the predictions of the UAL code and those of CSRTrack [M. Dohlus and T. Limberg, in Proceedings of the

  18. Measuring sperm whales from their clicks: stability of interpulse intervals and validation that they indicate whale length.

    Science.gov (United States)

    Rhinelander, Marcus Q; Dawson, Stephen M

    2004-04-01

    Multiple pulses can often be distinguished in the clicks of sperm whales (Physeter macrocephalus). Norris and Harvey [in Animal Orientation and Navigation, NASA SP-262 (1972), pp. 397-417] proposed that this results from reflections within the head, and thus that interpulse interval (IPI) is an indicator of head length, and by extrapolation, total length. For this idea to hold, IPIs must be stable within individuals, but differ systematically among individuals of different size. IPI stability was examined in photographically identified individuals recorded repeatedly over different dives, days, and years. IPI variation among dives in a single day and days in a single year was statistically significant, although small in magnitude (it would change total length estimates by whales (12.3 to 15.3 m). These discrepancies probably arise from the paucity of large (12-16 m) whales in data used in published regressions. A new regression is offered for this size range.

  19. Space-charge dynamics in ultra-cold ion bunches

    Science.gov (United States)

    Scholten, Robert; Murphy, Dene; Speirs, Rory; Thompson, Daniel; Sparkes, Benjamin; McCulloch, Andrew

    2014-05-01

    Cold ion sources based on photoionisation of laser cooled atoms provide a unique system for investigating Coulomb interactions within complex charged particle bunches. Space-charge driven expansion in charged particle beams is of critical importance for applications including electron and ion microscopy, mass spectrometry, synchrotrons and x-ray free electron lasers, and in electron diffraction where space-charge effects constrain the capacity to obtain diffraction information. Self-field effects are often difficult to observe because of thermal diffusion with traditional sources. Cold atom sources produce ions with temperatures of a few mK, such that subtle space-charge effects are apparent. We illustrate the capabilities through detailed investigation of a complex ion bunch shape, showing collective behaviour including high density caustics and shockwave structures arising from long-range interactions between small charge bunches.

  20. Nonlinear bunch motion in an accelerator with reactive impedance

    CERN Document Server

    Shaposhnikova, Elena

    1996-01-01

    Closed form solutions have been found for single particle and bunch motion in an accelerator with reactive (space charge or inductive wall) impedance. The problem is solved for the particular initial longitudinal distribution corresponding to a parabolic line density. In the case with RF off the system of equations in phase space is the same as that describing motion of a body under a gravitational force with integrals of motion similar to Kepler's laws. With RF on this model allows the amplitude and frequency of coherent bunch shape oscillations to be calculated for a bunch of any intensity far away from equilibrium. The results have been used to estimate the low-frequency impedance of the CERN SPS.

  1. Flame Length

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — Flame length was modeled using FlamMap, an interagency fire behavior mapping and analysis program that computes potential fire behavior characteristics. The tool...

  2. The accuracy of preoperative imaging in measuring the length of the ileocolic segment affected by Crohn's disease: a prospective cohort study.

    Science.gov (United States)

    Brouquet, A; Rangheard, A-S; Ifergan, J; Lazure, T; Carbonnel, F; Penna, C; Benoist, S

    2017-05-01

    The study aimed to evaluate the accuracy of imaging for measurement of the length of the ileocolic segment affected by Crohn's disease. Fifty-four consecutive patients who underwent resection between 2011 and 2014 for ileocolic Crohn's disease were prospectively studied. All had preoperative MR or CT enterography. Two independent radiologists measured the length of the diseased intestinal segment. The measurements were compared with the length of disease assessed on pathology of the non-fixed surgical specimen. The median preoperative length of the Crohn's disease segment on imaging was 20.5 (2-73) cm and 20 (3-90) cm, as measured by the two radiologists. Interobserver agreement was substantial (κ = 0.69) with a correlation coefficient (r) of 0.82 (P Crohn's disease segment on pathological examination was 16.5 (2-75) cm and was closely correlated with the radiological measurement (r = 0.76, P Crohn's disease segment on imaging was correct to within 5 cm of the value on pathology. It was correct in 30 (55%) patients and was underestimated and overestimated in 6 (11.1%) and 18 (33.3%). A length of disease of less than 20 cm found on imaging in 26 patients was confirmed in 25 (96%) on pathology, whereas a length of more than 20 cm found on imaging in 28 patients was confirmed in 18 (64%) on pathology. The sensitivity, specificity, positive predictive value, negative predictive value and overall accuracy of imaging for predicting a length of less than 20 cm were 71%, 95%, 96%, 64% and 79%. Imaging accurately identifies the length of the ileocolic segment of Crohn's disease when it is 20 cm or less on pathological examination. In patients with more extensive disease, imaging tends to overestimate the length and should be interpreted with caution. Colorectal Disease © 2016 The Association of Coloproctology of Great Britain and Ireland.

  3. Optical plasma torch electron bunch generation in plasma wakefield accelerators

    Directory of Open Access Journals (Sweden)

    G. Wittig

    2015-08-01

    Full Text Available A novel, flexible method of witness electron bunch generation in plasma wakefield accelerators is described. A quasistationary plasma region is ignited by a focused laser pulse prior to the arrival of the plasma wave. This localized, shapeable optical plasma torch causes a strong distortion of the plasma blowout during passage of the electron driver bunch, leading to collective alteration of plasma electron trajectories and to controlled injection. This optically steered injection is more flexible and faster when compared to hydrodynamically controlled gas density transition injection methods.

  4. Gyrophase-bunched Electrons: Cluster Observations and Simulations

    Science.gov (United States)

    Gurgiolo, C.; Vinas, A. F.; Goldstein, Melvyn L.

    2003-01-01

    The interaction of the solar wind with the Earth's bow shock is responsible for a number of phenomena both upstream and downstream. One of the least understood and studied of these is the generation of gyrophase-bunched electrons. We will describe initial work searching for and analyzing such events in (Plasma Electron And Current Experiment (PEACE) data from CLUSTER. Plasma simulations will complement the data analysis. Recent analyses suggest that gyrophase-bunched electrons are present rather frequently in the upstream region, due either to energization in the reflection off the shock front or, more likely, to phase trapping in locally produced whistler wave fields.

  5. Measurements on the influence of the length of the daily submergence time on the condition and appearence of mussels (

    NARCIS (Netherlands)

    Basal, M.

    1972-01-01

    Mussels (Mytilus edulis) living at different intertidal levels (viz. about 40, 10 and 0% of time exposed to the air) were compared as to length distribution, meat and shell weight, and linear dimensions. The long-exposed mussels were found to be on average smaller, to contain less meat, to

  6. Chord length distributions measurements during agglomeration of gas hydrate from a water-in-oil emulsion under laminar flow : simulation and experimentation

    Energy Technology Data Exchange (ETDEWEB)

    Le Ba, H.; Cameirao, A.; Herri, J.M. [Ecole des Mine de Saint Etienne, Saint-Etienne (France). Centre SPIN; Darbouret, M. [IFP, Lyon (France). Dept. of Fluid Mechanics; Peytavy, J.L.; Glenat, P. [Total, Pau (France)

    2008-07-01

    Flow loop experiments were conducted to study methane hydrate formation. A focused beam reflectance measurement (FBRM) was used to analyze in situ particle size and chord length distributions during the crystallization process. The aim of the study was to estimate the fractal parameters of gas hydrate aggregates circulating in a pressurized loop. Results of the analysis showed that hydrate aggregates that appeared during the crystallization of water droplets formed as a result of contact between primary particles and water droplets. The agglomeration process was associated with changes in the mean chord length as well as the appearance of shoulders in the chord length distribution. The agglomerates were modelled as fractal objects comprised of spherical primary particles. An algorithm was developed to simulate chord length distributions of random agglomerates characterized by fractal dimension, primary particle diameter and the number of primary particles. Results of the study showed that the diameter of the primary particles is related to sharp peaks in distribution that corresponded to the mode of the smallest chord lengths. Shoulders in larger chords indicated the compactness of the aggregates through its fractal dimensions and the maximum chord length of the number of primary particles within each agglomerate. 9 refs., 1 tab., 17 figs.

  7. A Bunch-By-Bunch and Turn-By-Turn Instrumentation Hardware Upgrade for CESR-c

    CERN Document Server

    Palmer, Mark A; Strohman, Charles R; Tanke, Eugene

    2005-01-01

    A key factor in the colliding beam performance of the Cornell Electron Storage Ring (CESR) is the impact of parasitic beam-beam interactions between bunches in the two beams as they follow their electrostatically separated orbits in a single vacuum chamber. In order to better investigate the differential performance of bunches in CESR, instrumentation electronics has been developed to allow acquisition of turn-by-turn data from multiple bunches simultaneously. The electronics consists of a standardized digital board centered around an Analog Devices TigerSHARC family digital signal processor, a communications interface, and an interface to the CESR Precision Timing System. Mated to these components is an analog front end and digitizer board which is customized for the particular diagnostic device of interest. Front ends have been developed for beam position monitor, luminosity monitor, and beam profile monitor applications. We describe the design and characterization of this new hardware.

  8. Space-charge effects in ultrahigh current electron bunches generated by laser-plasma accelerators

    National Research Council Canada - National Science Library

    Grüner, F. J; Schroeder, C. B; Maier, A. R; Becker, S; Mikhailova, J. M

    2009-01-01

    ...) generated in laser-plasma accelerators. At low electron energies such peak currents are expected to cause space-charge effects such as bunch expansion and induced energy variations along the bunch, potentially hindering the FEL process...

  9. Interferometric focal length measurement of positive and negative lenses using a lateral-shearing cyclic path optical configuration setup and polarization phase-shifting interferometry.

    Science.gov (United States)

    Kumar, Y Pavan; Negi, Sarvendra Singh; Kamath, M Pandurang; Chatterjee, Sanjib; Sharma, S D; Joshi, A S

    2017-10-20

    We present a simple interferometric focal length measurement technique for measuring the focal length of positive and negative lenses using a lateral-shearing cyclic path optical configuration (CPOC) setup and polarization phase-shifting interferometry (PPSI). The technique requires an auxiliary lens, whose focal length need not be known accurately, for generating a focused point source at its focal plane. The focal point of the test lens is adjusted to be in the vicinity of the focus of the auxiliary lens. The radii of the resulting spherical wave fronts emerging from the test lens, due to the defocus, for two different longitudinal shifted positions of the test lens are measured using the lateral-shearing CPOC setup and PPSI. Focal length of the test lens is determined from the known longitudinal shift and from the measured radii of the spherical wave fronts. Results obtained for 200.0 mm convex and 100.0 mm concave test lenses are presented.

  10. [Are ultrasound measurements of the cervical length and fetal head-perineum distance predictive of delivery outcome in post-term pregnancies?].

    Science.gov (United States)

    Vernet, T; Rivaux, G; Deruelle, P

    2016-06-01

    Post-term pregnancy is frequently associated with higher fetal and maternal morbidity and mortality. Its management essentially depends on clinical cervical characteristics as evaluated by the Bishop score (BS). However, BS is poorly predictive of the delivery outcome. We sought to demonstrate that ultrasound measurement of cervical length and evaluation of fetal height could predict the outcome in post-term pregnancies. A prospective single center study was undertaken between the 21st of January and the 1st of June 2013. Fetal height was measured using a transperineal technique and cervical length was evaluated by a vaginal ultrasound on patients consulting and their term date. C-section rates were considered to be the primary judgment criteria. A total of 136 patients were included. C-section rates in this population was 19%. Fetal height and cervical length were not different between the C-section group and the vaginal delivery group. Our study demonstrates that ultrasound measurement of cervical length and fetal height do not show better results than BS in predicting the outcome of post-term pregnancy. Combining these ultrasound measurements has already been suggested in other studies and promising results have been shown. More studies are necessary to further these results. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  11. Measurement of the penetration depth and coherence length of MgB2 in all directions using transmission electron microscopy

    DEFF Research Database (Denmark)

    Loudon, J. C.; Yazdi, Sadegh; Kasama, Takeshi

    2015-01-01

    We demonstrate that images of flux vortices in a superconductor taken with a transmission electron microscope can be used to measure the penetration depth and coherence length in all directions at the same temperature and magnetic field. This is particularly useful for MgB2, where these quantitie...

  12. Development and reliability of the Achilles Tendon Length Measure and comparison with the Achilles Tendon Resting Angle on patients with an Achilles tendon rupture.

    Science.gov (United States)

    Hansen, Maria Swennergren; Barfod, Kristoffer Weisskirchner; Kristensen, Morten Tange

    2017-12-01

    There is a need for a valid, reliable, and easily applicable clinical measure of the length of the Achilles tendon (AT) after rupture. This study examines the reliability of a new ruler based measurement, the Achilles Tendon Length Measure (ATLM) in comparison with the goniometer-based Achilles Tendon Resting Angle (ATRA). Measurements were performed by two independent physiotherapists eight weeks after AT rupture on 28 patients treated non-operatively. The mean (SD) injured ATLM was 56.5 (2.3)cm, ICC2.1 0.91(CI [0.72-0.97]), SEM 0.7cm (SEM% 1.2), MDC 1.9cm (MDC% 3.4). Corresponding data for the injured ATRA was mean 64.4° (3.9°), ICC2.1 0.84 (CI [0.68-0-92]), SEM 1.5° (SEM% 2.4), MDC 4.3° (MDC% 6.6). Both ATLM and ATRA showed excellent inter-rater reliability with low measurement error. Both measurements seem easy to use in clinical practice and potentially providing an indirect measure of the length of the AT after rupture. Copyright © 2016 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.

  13. Use of high-boiling point organic solvents for pulping oil palm empty fruit bunches.

    Science.gov (United States)

    Rodríguez, Alejandro; Serrano, Luis; Moral, Ana; Pérez, Antonio; Jiménez, Luis

    2008-04-01

    Oil palm empty fruit bunches were used as an alternative raw material to obtain cellulosic pulp. Pulping was done by using high-boiling point organic solvents of decreased polluting power relative to classical (Kraft, sulphite) solvents but affording operation at similar pressure levels. The holocellulose, alpha-cellulose and lignin contents of oil palm empty fruit bunches (viz. 66.97%, 47.91% and 24.45%, respectively) are similar to those of some woody raw materials such as pine and eucalyptus, and various non-wood materials including olive tree prunings, wheat straw and sunflower stalks. Pulping tests were conducted by using ethyleneglycol, diethyleneglycol, ethanolamine and diethanolamine under two different sets of operating conditions, namely: (a) a 70% solvent concentration, 170 degrees C and 90 min; and (b) 80% solvent, 180 degrees C and 150 min. The solid/liquid ratio was six in both cases. The amine solvents were found to provide pulp with better properties than did the glycol solvents. Ethanolamine pulp exhibited the best viscosity and drainage index (viz. 636 mL/g and 17 degrees SR, respectively), and paper made from it the best breaking length (1709 m), stretch (1.95%), burst index (0.98 kN/g) and tear index (0.33 mNm(2)/g). Operating costs can be reduced by using milder conditions, which provide similar results. In any case, the amines are to be preferred to the glycols as solvents for this purpose.

  14. The beam bunching and transport system of the Argonne positive ion injector

    Energy Technology Data Exchange (ETDEWEB)

    Den Hartog, P.K.; Bogaty, J.M.; Bollinger, L.M.; Clifft, B.E.; Pardo, R.C.; Shepard, K.W.

    1989-01-01

    A new positive ion injector (PII) is currently under construction at Argonne that will replace the existing 9-MV tandem electrostatic accelerator as an injector into ATLAS. It consists of an electron-cyclotron resonance-ion source on a 350-kV platform injecting into a superconducting linac optimized for very slow (..beta.. less than or equal to .007 c) ions. This combination can potentially produce even higher quality heavy-ion beams than are currently available from the tandem since the emittance growth within the linac is largely determined by the quality of the bunching and beam transport. The system we have implemented uses a two-stage bunching system, composed of a 4-harmonic gridded buncher located on the ECR high-voltage platform and a room temperature spiral-loaded buncher of novel design. A sinusoidal beam chopper is used for removal of tails. The beam transport is designed to provide mass resolution of M/..delta..M > 250 and a doubly-isochronous beamline is used to minimize time spread due to path length differences. 4 refs., 2 figs.

  15. Physical and Mechanical Properties of Palm Oil Frond and Stem Bunch for Developing Pruner and Harvester Machinery Design

    Directory of Open Access Journals (Sweden)

    Yazid Ismi Intara

    2013-06-01

    Full Text Available A development of oil palm pruner and harvester machinery design implemented in the field still faces a problem due to the lack of effective and efficient design which is need to be solved. It was noted that in order to develop the design, an early data and information of physical and mechanical properties of palm oil frond and stem fruits is critically important. The objective of the research was to obtain the physical and mechanical properties of palm oil frond and stem in order to develop the design of pruner and harvester machinery. The result showed that tool machinery was been advantageous by the physical properties of the plant i.e. the total weight of frond and leaf which enable to support the cutting process. The average of total weight of frond and leaf was 16.8 kg. The diagonal cutting trajectory was been more advantageous because of total weight and frond shape toward to the different of the plant tissue area. The measurement result shows that cutting curve follows the time required for cutting. The comparison among cutting curve shows differences in cutting thickness or length. In this case, the thickness is linear with cutting time. Besides, those curves show differences at the height which determine the maximum value of tested material cutting resistance. Alternative solution for machinery development design is pruner-harvester for height plant below 6 m and among 6 to 12 m. For below 6 m, pruner-harvester was designed by incorporating motor as power source and cutter-disc as the knife cutter. That condition was relied on that estate which was maintenance intensively commonly used cutter-disc. Pruner-harvester above 6 m and up to 12 m was improved based on manual egrek-designed by adding fresh fruit bunch alley supply glide in order to keep the fruits still in intact form. The consideration was based on affectivity and efficiency. It also considers homogenous ecological of palm oil plant which should be maintained to reduce global

  16. Upright MRI measurement of mechanical axis and frontal plane alignment as a new technique: a comparative study with weight bearing full length radiographs

    Energy Technology Data Exchange (ETDEWEB)

    Liodakis, Emmanouil; Kenawey, Mohamed; Doxastaki, Iosifina; Krettek, Christian; Haasper, Carl; Hankemeier, Stefan [Medical School Hannover, Department of Trauma Surgery, Hannover (Germany)

    2011-07-15

    The purpose of this prospective study was to investigate the practicality, accuracy, and reliability of upright MR imaging as a new radiation-free technique for the measurement of mechanical axis. We used upright MRI in 15 consecutive patients (30 limbs, 44.7 {+-} 20.6 years old) to measure mechanical axis deviation (MAD), hip-knee-ankle (HKA) angle, leg length, and all remaining angles of the frontal plane alignment according to Paley (mLPFA, mLDTA, mMPTA, mLDTA, JLCA). The measurements were compared to weight bearing full length radiographs, which are considered to be the standard of reference for planning corrective surgery. FDA-approved medical planning software (MediCAD) was used for the above measurements. Intra- and inter-observer reproducibility using mean absolute differences was also calculated for both methods. The correlation coefficient between angles determined with upright MRI and weight bearing full length radiographs was high for mLPFA, mLDTA, mMPTA, mLDTA, and the HKA angle (r > 0.70). Mean interobserver and intraobserver agreements for upright MRI were also very high (r > 0.89). The leg length and the MAD were significantly underestimated by MRI (-3.2 {+-} 2.2 cm, p < 0.001 and -6.2 {+-} 4.4 mm, p = 0.006, respectively). With the exception of underestimation of leg length and MAD, upright MR imaging measurements of the frontal plane angles are precise and produce reliable, reproducible results. (orig.)

  17. Acceleration of a trailing positron bunch in a plasma wakefield accelerator.

    Science.gov (United States)

    Doche, A; Beekman, C; Corde, S; Allen, J M; Clarke, C I; Frederico, J; Gessner, S J; Green, S Z; Hogan, M J; O'Shea, B; Yakimenko, V; An, W; Clayton, C E; Joshi, C; Marsh, K A; Mori, W B; Vafaei-Najafabadi, N; Litos, M D; Adli, E; Lindstrøm, C A; Lu, W

    2017-10-27

    High gradients of energy gain and high energy efficiency are necessary parameters for compact, cost-efficient and high-energy particle colliders. Plasma Wakefield Accelerators (PWFA) offer both, making them attractive candidates for next-generation colliders. In these devices, a charge-density plasma wave is excited by an ultra-relativistic bunch of charged particles (the drive bunch). The energy in the wave can be extracted by a second bunch (the trailing bunch), as this bunch propagates in the wake of the drive bunch. While a trailing electron bunch was accelerated in a plasma with more than a gigaelectronvolt of energy gain, accelerating a trailing positron bunch in a plasma is much more challenging as the plasma response can be asymmetric for positrons and electrons. We report the demonstration of the energy gain by a distinct trailing positron bunch in a plasma wakefield accelerator, spanning nonlinear to quasi-linear regimes, and unveil the beam loading process underlying the accelerator energy efficiency. A positron bunch is used to drive the plasma wake in the experiment, though the quasi-linear wake structure could as easily be formed by an electron bunch or a laser driver. The results thus mark the first acceleration of a distinct positron bunch in plasma-based particle accelerators.

  18. Ponderomotive scattering of an electron-bunch before injection into a laser wakefield

    NARCIS (Netherlands)

    Khachatryan, A.G.; Luttikhof, M.J.H.; van Goor, F.A.; Boller, Klaus J.

    2006-01-01

    For the purpose of laser wakefield acceleration, it turned out that also the injection of electron bunches longer than a plasma wavelength can generate accelerated femtosecond bunches with relatively low energy spread. This is of high interest because such injecting bunches can be provided, e.g., by

  19. First Commissioning Results of the ELETTRA Transverse Multi-Bunch Feedback

    CERN Document Server

    Bulfone, D; Bressanutti, R; Carniel, A; Cautero, G; Fabris, A; Gambitta, A; Giuressi, D; Loda, G; Lonza, M; Mazzolini, F; Mian, G; Pangos, N; Sergo, R; Smaluk, V; Tommasini, R; Tosi, L; Zambon, L

    2001-01-01

    A wide-band bunch-by-bunch Transverse Multi-Bunch Feedback, developed in collaboration with the Swiss Light Source (SLS), has been installed at ELETTRA. After a description of the main hardware/software components, the first commissioning results and the present status of the system are given.

  20. Multiple frequency generation by bunched solitons in Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Lomdahl, P. S.; Sørensen, O. H.; Christiansen, Peter Leth

    1981-01-01

    A detailed numerical study of a long Josephson tunnel junction modeled by a perturbed sine-Gordon equation demonstrates the existence of a variety of bunched soliton configurations. Thus, on the third zero-field step of the V-I characteristic, two simultaneous adjacent frequencies are generated...

  1. Single Bunch Stability in LER of PEP II

    Energy Technology Data Exchange (ETDEWEB)

    Heifets, S.; /SLAC; Sabbi, G.; /Fermilab

    2011-10-11

    The note describes results of studies of the single bunch stability in the low energy ring (LER) of the PEP-II B-factory. Simulations describe the potential well distortion (PWD) obtained by numerical solution of the Haiisinski equation and results on the beam stability obtained with the code TRISIM. Both longitudinal and transverse wake fields are taken into account. Preliminary estimates indicate that single bunch in the LER of the PEP-II B-factory has to be stable, both longitudinally and transversely, at the maximum design bunch current 1.8 mA (beam current 3A). However, realistic wakes of the machine has been constructed only recently using results of the extensive numerical simulations of the vacuum components of the ring. Additional to that, the code TRISIM, a simulation program for single-bunch collective effects written by one of the authors (G. S.), became recently available. This allows us to study beam stability in a more reliable way than it is possible analytically.

  2. BUNCHED BEAM STOCHASTIC COOLING SIMULAITONS AND COMPARISON WITH DATA

    Energy Technology Data Exchange (ETDEWEB)

    BLASKIEWICZ,M.; BRENNAN, J.M.

    2007-09-10

    With the experimental success of longitudinal, bunched beam stochastic cooling in RHIC it is natural to ask whether the system works as well as it might and whether upgrades or new systems are warranted. A computer code, very similar to those used for multi-particle coherent instability simulations, has been written and is being used to address these questions.

  3. Analytical treatment of single bunch stability in a linac

    CERN Document Server

    Guignard, Gilbert

    1998-01-01

    Single bunch stability is analysed by solving the equation of motion of the particles travelling in a linac, for a Gaussian distribution of charge, a linear variation of the transverse wakefield along the bunch, a smooth focusing and negligible acceleration. The treatment is based on a non-standard perturbation expansion that has been specifically developed for this study and preserves at each order the intrinsic detuning likely to stabilise the resonant beam break-up. It provides a closed expression for the tune shift along the bunch resulting from BNS damping and autophasing, methods proposed in the past to control the emittance, and a first­order solution for the transverse off­sets within the bunch. The analytic result obtained makes it possible to study the behaviour of the solution and compute the emittance dilution in specific cases. The present theory is a useful complement to the numerical simulations done with the MUSTAFA code in the Compact Linear Collider scheme (CLIC). It also gives an interest...

  4. Palm oil fresh fruit bunch ripeness grading identification using color ...

    African Journals Online (AJOL)

    This research investigates the ripeness grading identification of the palm oil FFB using color features that are color histogram, color moment and color correlogram. Palm is harvested during the optimum stage of its ripeness since it improves the FFB oil quality and quantity. Harvesting wrong bunches decreases the oil ...

  5. Bunch Frequency Multiplication by RF Injection into an Isochronous Ring

    CERN Document Server

    Royer, P

    2003-01-01

    The Compact LInear Collider (CLIC)collaboration studies the possibility of building a multi-TeV (3 TeV centre-of-mass), high-luminosity electron-positron collider for particle physics. The CLIC scheme is based on high-frequency (30 GHz) linear accelerators powered by a low-energy, high-intensity drive beam running parallel to the main linear accelerators (Two-Beam Acceleration concept). One of the main challenges to realize this scheme is to generate the drive beam in a low-frequency accelerator and to achieve the required high-frequency bunch structure needed for the final acceleration. In order to provide bunch frequency multiplication, the main manipulation consists in sending the beam through an isochronous combiner ring using radio-frequency (RF) deflectors to inject and combine electron bunches. However, such a scheme has never been used before, and the first stage of the CLIC Test Facility 3 (CTF3) project aims at a low-charge demonstration of the bunch frequency multiplication by RF injection into an ...

  6. Effects of composted oil palm bunch wastes and chemical fertilizer ...

    African Journals Online (AJOL)

    A greenhouse study was conducted at the University of Nigeria, Nsukka to compare the effects of sole and integrated use of composted oil palm bunch waste and chemical fertilizer for improving the growth of oil palm seedlings under water stress condition. The experiment was a 3x3x4 factorial in a completely randomized ...

  7. Tax Bunching, Income Shifting and Self-employment

    DEFF Research Database (Denmark)

    le Maire, Christian Daniel; Schjerning, Bertel

    shifting was neglected in this case, we would conclude that taxable incomes were highly sensitive to changes in marginal tax rates. We show, however, that more than half of the observed bunching in taxable income for the self-employed is driven by intertemporal income shifting, implying a structural...

  8. LHC Report: 1,033 bunches per beam and counting

    CERN Multimedia

    Jorg Wenninger for the LHC team

    2015-01-01

    Following the second technical stop, the first beams were injected into the LHC in the early evening of Saturday, 5 September. About ten days later, the machine was operated with around 1,000 bunches per beam.    Evolution of the stored energy per LHC beam, over time.   The first step after a technical stop consists of running through a full LHC cycle, from injection to collisions and beam dump, with a low-intensity bunch (“probe”) to check all machine settings and equipment. This is followed by a series of collimation and absorber validation tests at different points in the LHC cycle. Low-intensity beams – typically the equivalent of three nominal bunches (3 x 1011 protons) – are expanded transversely or longitudinally, or de-bunched to verify that the collimators and absorbers are correctly intercepting lost particles. The techniques for those validations have been progressively improved, and t...

  9. Felling and bunching small timber on steep slopes.

    Science.gov (United States)

    Rodger A. Arola; Edwin S. Miyata; John A. Sturos; Helmuth M. Steinhilb

    1981-01-01

    Discusses the results of a field test of the unique Menzi Muck machine for felling and bunching small trees on steep slopes. Includes the analysis of a detailed time study to determine the productivity, costs, and economic feasibility of this unusual machine.

  10. String formulation of space charge forces in a deflecting bunch

    Directory of Open Access Journals (Sweden)

    Richard Talman

    2004-10-01

    Full Text Available The force between two moving point charges, because of its inverse square law singularity, cannot be applied directly in the numerical simulation of bunch dynamics; radiative effects make this especially true for short bunches being deflected by magnets. This paper describes a formalism circumventing this restriction in which the basic ingredient is the total force on a point charge comoving with a longitudinally aligned, uniformly charged string. Bunch evolution can then be treated using direct particle-to-particle, intrabeam scattering, with no need for an intermediate, particle-in-cell, step. Electric and magnetic fields do not appear individually in the theory. Since the basic formulas are both exact (in paraxial approximation and fully relativistic, they are applicable to beams of all particle types and all energies. But the theory is expected to be especially useful for calculating the emittance growth of the ultrashort electron bunches of current interest for energy recovery linacs and free-electron lasers. The theory subsumes coherent synchrotron radiation and centrifugal space charge force. Renormalized, on-axis, longitudinal field components are in excellent agreement with values from Saldin et al. [DESY Report No. DESY-TESLA-FEL-96-14, 1995; Nucl. Instrum. Methods Phys. Res., Sect. A 417, 158 (1998.NIMAER0168-900210.1016/S0168-9002(9800623-8

  11. Production of Mineral Water Using Palm Bunch Ash (PBA) From ...

    African Journals Online (AJOL)

    The composition of the palm bunch ash derived from oil palm Elaeis guineensis was determined and it was(PBA) found to contain potassium and magnesium in significant amounts. The ash solution was used to produce mineral water that has ionic composition comparable to those of some brands of bottled mineral water.

  12. Perception of a Japanese Vowel Length Contrast by Japanese and American English listeners: Behavioral and Electrophysiological Measures

    OpenAIRE

    Hisagi, Miwako; Shafer, Valerie L.; Strange, Winifred; Sussman, Elyse S.

    2010-01-01

    This study examined the role of automatic selective perceptual processes in native and non-native listeners' perception of a Japanese vowel length contrast (tado vs. taado), using multiple, natural-speech tokens of each category as stimuli in a “categorial oddball” design. Mismatch Negativity (MMN) was used to index discrimination of the temporally-cued vowel contrast by naïve adult American listeners and by a native Japanese-speaking control group in two experiments in which attention to the...

  13. Chlorophyll fluorescence imaging for the noninvasive assessment of anthocyanins in whole grape (Vitis vinifera L.) bunches.

    Science.gov (United States)

    Agati, Giovanni; Traversi, Maria Laura; Cerovic, Zoran G

    2008-01-01

    The distribution of anthocyanins in grape (Vitis vinifera L.) bunches from the Sangiovese cultivar was measured nondestructively by chlorophyll fluorescence imaging using two excitation light bands at 550 and 650 nm in sequence. The pixel intensity in the derived logarithm of the fluorescence excitation ratio image was directly related, by an exponential function (r2 = 0.93), to the anthocyanin concentration of berry extracts. The method will be useful for the assessment of the heterogeneity of anthocyanin accumulation in berries that is known to depend on physiologic and climatic factors. It can also represent a new, rapid and noninvasive technique for the assessment of grape ripening and the appropriate time of harvest.

  14. Effects of different storage and measuring methods on larval length values for the blow flies (Diptera: Calliphoridae) Lucilia sericata and Calliphora vicina.

    Science.gov (United States)

    Bugelli, Valentina; Campobasso, Carlo Pietro; Verhoff, Marcel A; Amendt, Jens

    2017-05-01

    In forensic entomology, the methods of sampling, killing, and storing entomological samples can affect larval age estimation, and, hence, the estimation of the minimum post-mortem interval. In the existing manuals, there is a certain amount of heterogeneity regarding methods and the recommendations for best practice in forensic entomology are insufficiently validated. This study evaluated three different length-measurement methods for larval stages and examined the influence of different killing and storing methods on the larval length of two forensically important blow flies, Lucilia sericata and Calliphora vicina. The three different measuring methods were a) a ruler with a 0.1mm scale, b) a geometrical micrometer, and c) a computer-aided stereomicroscope. They were used to measure the length of L 1 -L 3 C. vicina larvae and detect no significant differences. This supports the view that a simple tool like a geometrical micrometer can produce reliable results in forensic entomology. Newly hatched larvae of L. sericata and C. vicina were killed with hot water (HW) and divided into two equal subsamples. Lengths of all larvae were measured immediately after killing, then every 24h until day 4, and once more after 7days of storage in ≥70%-ethanol. L. sericata larvae only showed significant changes in length in the HW group stored at room temperature. After 4 and 7days of storage, these 24-h- and 72-h-old larvae showed a significant decrease in length compared with those in a fridge at 6°C. This decrease can, however, be considered a negligible natural variation without forensically relevant consequences for larval age estimation of L. sericata samples. For C. vicina, an increase in length was observed over time. This was significant only for younger larvae (24-48h old) stored in 70%-ethanol. This variance in length can lead to a wrong estimation of age; however, only for larvae stored in 70%-ethanol, not for those stored in 96%-ethanol. We examined the influence of

  15. First observation of $\\pi^{-}K^+$ and $\\pi^{+}K^-$ atoms, their lifetime measurement and $\\pi K$ scattering lengths evaluation

    CERN Document Server

    Afanasyev, Leonid

    2016-01-01

    The Low Energy QCD allows to calculate the ππ and π K scattering lengths with high precision. There are accurate relations between these scattering lengths and π + π − , π − K + , π + K − atoms lifetimes. The experiment on the first observation of π − K + and π + K − atoms is described. The atoms were generated in Nickel and Platinum targets hit by the PS CERN proton beam with momentum of 24 GeV/ c . Moving in the target, part of atoms break up producing characteristic π K pairs (atomic pairs) with small relative momentum Q in their c.m.s. In the experiment, we detected n A = 349 ± 62 (5.6 standard deviations) π − K + and π + K − atomic pairs. The main part of π K pairs are produced in free state. The majority of such particles are generated directly or from short-lived sources as ρ , ω and similar resonances. The electromagnetic interactions in the final state create Coulomb pairs with a known sharp dependence on Q . This effect allows to evaluate the number of these Coulomb pai...

  16. Neutron interferometric measurement of the scattering length difference between the triplet and singlet states of n-$^3$He

    CERN Document Server

    Huber, M G; Chen, W C; Gentile, T R; Hussey, D S; Black, T C; Pushin, D A; Shahi, C B; Wietfeldt, F E; Yang, L

    2014-01-01

    We report a determination of the n-$^3$He scattering length difference $\\Delta b^{\\prime} = b_{1}^{\\prime}-b_{0}^{\\prime} = $ ($-5.411$ $\\pm$ $0.031$ (statistical) $\\pm$ $0.039$ (systematic)) fm between the triplet and singlet states using a neutron interferometer. This revises our previous result $\\Delta b^{\\prime} = $ (-5.610 $\\pm$ $0.027$ (statistical) $\\pm$ $0.032$ (systematic) fm obtained using the same technique in 2008. This revision is due to a re-analysis of the 2008 experiment that includes a more robust treatment of the phase shift caused by magnetic field gradients near the $^3$He cell. Furthermore, we more than doubled our original data set from 2008 by acquiring six months of additional data in 2013. Both the new data set and a re-analysis of the older data are in good agreement. Scattering lengths of low Z isotopes are valued for use in few-body nuclear effective field theories, provide important tests of modern nuclear potential models and in the case of $^3$He aid in the interpretation of neu...

  17. Palpebral fissure length measurement: accuracy of the FAS facial photographic analysis software and inaccuracy of the ruler.

    Science.gov (United States)

    Astley, Susan J

    2015-01-01

    Accurate fetal alcohol spectrum disorder diagnoses require accurate facial measurement. The Fetal Alcohol Syndrome (FAS) Facial Photographic Analysis Software was developed to overcome measurement error known to occur with ruler measurement of the PFL. Recent publications have queried the Software's accuracy. 1) Demonstrate the Software's ability to accurately measure a PFL from a 2-dimensional digital facial photograph. 2) Demonstrate the frequency and magnitude of error when the PFL is measured directly by clinicians using a ruler. Objective 1: PFLs of mannequins were measured using the Software and a sliding digital caliper, with the latter serving as the gold-standard accurate measure. Mannequins allowed the caliper prongs to be placed directly on the landmarks that define the PFL. Objective 2: PFLs of 1,027 patients evaluated at the University of Washington FAS Diagnostic & Prevention Network were measured with the Software and directly by one or two clinicians using a ruler. Objective 1: The Software derived PFLs that were identical to or within 0.2 mm of the caliper measures. Objective 2: There was tremendous inter-rater variability in PFLs measured by clinicians using a hand held ruler. Seventy-seven percent of patients had their PFLs measured incorrectly (greater than 1 mm error) by at least one of the two clinicians using a ruler. The FAS Facial Photographic Analysis Software measures the PFL with the same accuracy as a sliding digital caliper, as it was programmed to do. Direct measurement of the PFL with a ruler is very prone to error.

  18. Alkali suppression within laser ion-source cavities and time structure of the laser ionized ion-bunches

    CERN Document Server

    Lettry, Jacques; Köster, U; Georg, U; Jonsson, O; Marzari, S; Fedosseev, V

    2003-01-01

    The chemical selectivity of the target and ion-source production system is an asset for Radioactive Ion-Beam (RIB) facilities equipped with mass separators. Ionization via laser induced multiple resonant steps Ionization has such selectivity. However, the selectivity of the ISOLDE Resonant Ionization Laser Ion-Source (RILIS), where ionization takes place within high temperature refractory metal cavities, suffers from unwanted surface ionization of low ionization potential alkalis. In order to reduce this type of isobaric contaminant, surface ionization within the target vessel was used. On-line measurements of the efficiency of this method is reported, suppression factors of alkalis up to an order of magnitude were measured as a function of their ionization potential. The time distribution of the ion bunches produced with the RILIS was measured for a variety of elements and high temperature cavity materials. While all ions are produced within a few nanoseconds, the ion bunch sometimes spreads over more than 1...

  19. Short-bunch generation from an rf photoinjector with injection phase compensation

    Directory of Open Access Journals (Sweden)

    F. H. Chao

    2015-05-01

    Full Text Available A radio-frequency photoinjector is widely used for generating picosecond-femtosecond electron bunches. During particle acceleration, the electron bunch shape varies under the influence of both the acceleration fields and space charge fields. To restore a distorted electron bunch, we propose an injection phase compensation technique for the electrons by illuminating the photocathode with a pulse-front-corrected laser pulse. Using an S-band 1.6-cell photoinjector as an example, our study shows that the proposed technique can generate nearly undistorted electron bunches up to a bunch rate of a few hundred terahertz.

  20. Sequential control of step-bunching during graphene growth on SiC (0001)

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Jianfeng; Kusunoki, Michiko [Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8603 (Japan); Yasui, Osamu; Norimatsu, Wataru, E-mail: w-norimatsu@imass.nagoya-u.ac.jp; Matsuda, Keita [Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan)

    2016-08-22

    We have investigated the relation between the step-bunching and graphene growth phenomena on an SiC substrate. We found that only a minimum amount of step-bunching occurred during the graphene growth process with a high heating rate. On the other hand, a large amount of step-bunching occurred using a slow heating process. These results indicated that we can control the degree of step-bunching during graphene growth by controlling the heating rate. We also found that graphene coverage suppressed step bunching, which is an effective methodology not only in the graphene technology but also in the SiC-based power electronics.

  1. Measurement of Dead Space Fraction Upon ICU Admission Predicts Length of Stay and Clinical Outcomes Following Bidirectional Cavopulmonary Anastomosis.

    Science.gov (United States)

    Cigarroa, Claire L; van den Bosch, Sarah J; Tang, Xiaoqi; Gauvreau, Kimberlee; Baird, Christopher W; DiNardo, James A; Kheir, John Nagi

    2018-01-01

    saturation were linearly associated with prolonged ICU length of stay, hospital length of stay, duration of mechanical ventilation, and duration of thoracic drainage (p space fraction in excess of 0.28 or arterial oxyhemoglobin saturation less than 78% upon ICU admission indicates an increased likelihood of requiring intervention prior to hospital discharge. Increasing alveolar dead space fraction and decreasing arterial oxyhemoglobin saturation are associated with increased lengths of stay.

  2. SPARC Working Point Optimization for a Bunch with Gaussian Temporal Profile

    CERN Document Server

    Boscolo, Manuela; Fusco, Valeria; Migliorati, Mauro; Reiche, Sven; Ronsivalle, Concetta

    2005-01-01

    We present the optimization of the working point for the SPARC photoinjector with a Gaussian temporal profile. The implications of a Gaussian temporal profile are discussed here for the standard working conditions and for the RF compressor case in comparison with the nominal working point performances of a 10ps flat top pulse with rise time of 1ps. Comparisons with the upgraded version of the HOMDYN code including arbitrary bunch temporal profiles are also reported. Advantages and drawbacks of the Gaussian and flat top pulse shapes are discussed. For the standard working point, it is shown that the two cases provide the same saturation length and average power, but the higher current in the beam core of the Gaussian pulse gives a higher peak radiation power. As the laser pulse shape could be Gaussian at the first stage of the SPARC operation, it is clear the importance of these simulation results.

  3. arXiv A Method to Determine the Maximum Defocused Proton Radius of a Self-Modulated Proton Bunch in AWAKE

    CERN Document Server

    Turner, Marlene; Muggli, Patric

    The AWAKE experiment at CERN aims to drive GV/m plasma wakefields with a self-modulated proton drive bunch, and to use them for electron acceleration. During the self-modulation process, protons are defocused by the transverse plasma wakefields and form a halo around the focused bunch core. The two-screen setup integrated in AWAKE measures the transverse, time-integrated proton bunch distribution downstream the \\unit[10]{m} long plasma to detect defocused protons. By measuring the maximum radius of the defocused protons we attempt calculate properties of the self-modulation. In this article, we develop a routine to identify the maximum radius of the defocused protons, based on a standard contour method. We compare the maximum radius obtained from the contour to the logarithmic lineouts of the image to show that the determined radius identifies the edge of the distribution.

  4. Impact of acid diffusion length on resist LER and LWR measured by CD-AFM and CD-SEM

    Science.gov (United States)

    Foucher, J.; Pikon, A.; Andes, C.; Thackeray, J.

    2007-03-01

    The improvement of devices performances is due to many factors such as new architectures, new materials and better lithography resolution. Resist chemical components play a key role in the final performance of a specific resist. In addition to resist characteristics such as: resolution, etching selectivity, the final resist line edge roughness (LER) and line width roughness (LWR) becomes a critical issue because it can degrade resolution and linewidth accuracy and causes fluctuations of transistors performances 1,2. LER and LWR are currently calculated with top-down view SEM images. With chemically amplified resists, we can play on photoacid generator size to partially control acid diffusion length during the post exposure bake. In this paper we propose to compare two techniques, the CD-AFM and CD SEM in order to study the impact of various acid diffusion lengths on LER and LWR. The results show that globally the two techniques agree on most of the results and show the same trends. However, when the profiles vary the linearity between the two techniques can vary drastically. In addition, as a complementary technique to the CD-SEM technique, the CD-AFM gives additional information such as height (top loss), top rounding and sidewall angle which allow us to understand more deeply the impact of PAG size. Therefore, these additional information have a non negligible impact on near term new resist development and lithography processes development. As an illustration of this work, we will present the latest resist development coming from this understanding and leading to very low LER and LWR. Finally, we will propose strengths and weakness of each technique.

  5. Radiobiological Effectiveness of Ultrashort Laser-Driven Electron Bunches: Micronucleus Frequency, Telomere Shortening and Cell Viability.

    Science.gov (United States)

    Andreassi, Maria Grazia; Borghini, Andrea; Pulignani, Silvia; Baffigi, Federica; Fulgentini, Lorenzo; Koester, Petra; Cresci, Monica; Vecoli, Cecilia; Lamia, Debora; Russo, Giorgio; Panetta, Daniele; Tripodi, Maria; Gizzi, Leonida A; Labate, Luca

    2016-09-01

    Laser-driven electron accelerators are capable of producing high-energy electron bunches in shorter distances than conventional radiofrequency accelerators. To date, our knowledge of the radiobiological effects in cells exposed to electrons using a laser-plasma accelerator is still very limited. In this study, we compared the dose-response curves for micronucleus (MN) frequency and telomere length in peripheral blood lymphocytes exposed to laser-driven electron pulse and X-ray radiations. Additionally, we evaluated the effects on cell survival of in vitro tumor cells after exposure to laser-driven electron pulse compared to electron beams produced by a conventional radiofrequency accelerator used for intraoperative radiation therapy. Blood samples from two different donors were exposed to six radiation doses ranging from 0 to 2 Gy. Relative biological effectiveness (RBE) for micronucleus induction was calculated from the alpha coefficients for electrons compared to X rays (RBE = alpha laser/alpha X rays). Cell viability was monitored in the OVCAR-3 ovarian cancer cell line using trypan blue exclusion assay at day 3, 5 and 7 postirradiation (2, 4, 6, 8 and 10 Gy). The RBE values obtained by comparing the alpha values were 1.3 and 1.2 for the two donors. Mean telomere length was also found to be reduced in a significant dose-dependent manner after irradiation with both electrons and X rays in both donors studied. Our findings showed a radiobiological response as mirrored by the induction of micronuclei and shortening of telomere as well as by the reduction of cell survival in blood samples and cancer cells exposed in vitro to laser-generated electron bunches. Additional studies are needed to improve preclinical validation of the radiobiological characteristics and efficacy of laser-driven electron accelerators in the future.

  6. Phase space linearization and external injection of electron bunches into laser-driven plasma wakefields at REGAE

    Energy Technology Data Exchange (ETDEWEB)

    Zeitler, Benno Michael Georg [Hamburg Univ. (Germany). Fakultaet fuer Mathematik, Informatik und Naturwissenschaften

    2017-01-15

    beam control achievable in conventional electron sources is combined with the huge gradients of a plasma booster stage. In this thesis, the concept of the external injection experiment at REGAE is presented. The physical foundations are illustrated and combined into an extensive start-to-end design study. Using the key constraints from this results, the required beam line design is developed. An injection into a plasma wave with the aim of diagnosing the accelerating field inevitably requires electron bunches which are much shorter then the period of the plasma wavelength. This reference length is typically on the order of a few ten microns. The conventionally accelerated particle distribution must therefore be compressed. At REGAE the so-called ballistic bunching scheme is applied, leading to bunches with a longitudinal extent of about 3 μm. Even better results can be obtained if nonlinearities arising in the compression are compensated. A novel method to achieve this, based on the controlled beam expansion, is the stretcher mode. It is developed and described in detail in the second part of this thesis. Simulations that verify the analytic model presented in the thesis suggest a possible decrease in bunch length by a factor of ten and more compared to the design parameters of REGAE. Electron bunch lengths below 300 nm, i.e., below one femtosecond (1 fs=10{sup -15} s) duration, can be produced. In addition, an energy spread compensation leading to quasi mono-energetic beams can be achieved by this method. Importantly, the approach is not restricted to Regae or similar machines, but can be generalized to a variety of accelerators.

  7. The flexibility of low molecular weight double-stranded DNA as a function of length. I. Light scattering measurements and the estimation of persistence lengths from light scattering, sedimentation and viscosity.

    Science.gov (United States)

    Godfrey, J E; Eisenberg, H

    1976-09-01

    In the preceding paper are described the isolation and physical characterization of seven narrowly disperse fractions of calf thymus DNA in the molecular weight range 0.3 to 1.3 X 10(6) daltons. Herein, we have determined by light scattering the molecular weights and root mean square radii of these fractions in a solvent comprising 0.2 M NaCl, 2 mM EDTA, 2mM Na-PO4,pH7. Measurements were made in a modified Wippler-Scheibling photometer to a 20 degree lower limit of scattering angle on solutions rendered virtually dust-free by procedures described. The optical anisotropies of the DNA fractions were measured permitting the experimental molecular weights and root mean square radii to be corrected to their true values. From these values, with appropriate polydispersity corrections, we calculate a Kratky-Porod persistence length, a, of 54.0 +/- 5.6 nm which is invariant over the molecular range examined. From the sedimentation coefficients (preceding paper) and the theory of Yamakawa and Fujii, we calculate a to be 66 nm, a value found to apply equally well to several DNA samples of various origins whose sedimentation rates are known in themolecular weight range from about 4 X 10(4) to 10(8) daltons. Similarly, from the intrinsic viscosities and the theory of Yamakawa and Fujii, we calculate a to be 59 nm, which again adequately applies to a number of DNA samples whose viscosities have been measured by other workers in the molecular wieght range 3 X 10(5) to 10(8) daltons. The Flory-Mandelkern paramerter, beta, was found to vary with molecular weight in the manner predicted by the theory of Yamakawa and Fujii. The average value of a from the three sets of measurements is 60 +/- 6nm, which we believe applies to double-stranded DNA molecules, independent of chain length, over the whole range of molecular weights from which reliable data exist.

  8. First measurements of subpicosecond electron beam structure by autocorrelation of coherent diffraction radiation

    CERN Document Server

    Lumpkin, Alex H; Rule, D W

    2001-01-01

    We report the initial measurements of subpicosecond electron beam structure using a nonintercepting technique based on the autocorrelation of coherent diffraction radiation (CDR). A far infrared (FIR) Michelson interferometer with a Golay detector was used to obtain the autocorrelation. The radiation was generated by a thermionic rf gun beam at 40 MeV as it passed through a 5-mm-tall slit/aperture in a metal screen whose surface was at 45 deg. to the beam direction. For the observed bunch lengths of about 450 fs (FWHM) with a shorter time spike on the leading edge, peak currents of about 100 A are indicated. Also a model was developed and used to calculate the CDR from the back of two metal strips separated by a 5-mm vertical gap. The demonstrated nonintercepting aspect of this method could allow on-line bunch length characterizations to be done during free-electron laser experiments.

  9. Fast High-Intensity Single-Bunch Transverse Coherent Instability in Synchrotrons due to a Broad-Band Resonator Impedance

    CERN Document Server

    Métral, Elias

    2001-01-01

    The instability rise-time is computed when it is faster than the synchrotron period, using the mode-coupling formalism. The case is treated of a bunch interacting with a broad-band resonator impedance, and whose length is greater than the inverse of twice the resonance frequency. The formula is compared to the one obtained by Brandt and Gareyte in a beam break-up approach, and to the one first obtained by Ruth and Wang in a fast blow-up theory, and later re-derived by Kernel et al. in a post-head-tail formalism. Stabilisation by synchrotron oscillation is also discussed.

  10. Vertebrae length and ultra-structure measurements of collagen fibrils and mineral content in the vertebrae of lordotic gilthead seabreams (Sparus aurata).

    Science.gov (United States)

    Berillis, Panagiotis; Panagiotopoulos, Nikolaos; Boursiaki, Vaia; Karapanagiotidis, Ioannis T; Mente, Eleni

    2015-08-01

    Skeletal deformities of gilthead seabream (Sparus aurata) are a major factor affecting the production cost, the external morphology and survival and growth of the fish. Adult individuals of S. aurata were collected from a commercial fish farm in Greece and were divided into two groups: one with the presence of lordosis, a skeletal deformity, and one without any skeletal deformity. Fishes were X-rayed, and cervical, abdominal and caudal vertebrae lengths were measured. Vertebrae were taken from the site of the vertebral column where lordosis occurred. One part was decalcified and prepared for collagen examination with transmission electron microscopy, and the rest were incinerated, and the Ca and P contents were measured. The stoichiometries of the samples were obtained by EDS (Energy Dispersive Spectroscopy). The same procedure was followed for fish without skeletal deformities (vertebrae were taken from the middle region of the vertebral column). The decalcified vertebrae parts were examined with TEM, collagen micrographs were taken and the fibrils' periods and diameters were measured. There were no significant differences for both Ca and P or the collagen fibrils' periods between the two fish groups. The mean lengths of the cervical, abdominal and caudal vertebrae where lordosis occurred were similar to the lengths of the respective regions of the individuals without the skeletal deformity. The TEM examination showed a significantly smaller mean vertebrae collagen fibril diameter from the fishes with lordosis compared with those from the controls, revealing the significance of collagen to bone structure. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Technical measures without enforcement tools: is there any sense? A methodological approach for the estimation of passive net length in small scale fisheries

    Directory of Open Access Journals (Sweden)

    A. LUCCHETTI

    2014-09-01

    Full Text Available Passive nets are currently among the most important fishing gears largely used along the Mediterranean coasts by the small scale fisheries sector. The fishing effort exerted by this sector is strongly correlated with net dimensions. Therefore, the use of passive nets is worldwide managed by defining net length and net drop. The EC Reg. 1967/2006 reports that the length of bottom-set and drifting nets may be also defined considering their weight or volume; however, no practical suggestions for fisheries inspectors are yet available. Consequently,  even if such technical measures are reasonable from a theoretical viewpoint, they are hardly suitable as a management tool, due to the difficulties in harbour control. The overall objective of this paper is to provide a quick methodological approach for the gross estimation of passive net length (by net type on the basis of net volume. The final goal is to support fisheries managers with suitable advice for enforcement and control purposes. The results obtained are important for the management of the fishing effort exerted by small scale fisheries. The methodology developed in this study should be considered as a first attempt to tackle the tangled problem of net length estimation that can be easily applied in other fisheries and areas in order to improve the precision of the models developed herein.

  12. New Technique for Luminosity Measurement Using 3D Pixel Modules in the ATLAS IBL Detector

    CERN Document Server

    Liu, Peilian; The ATLAS collaboration

    2017-01-01

    The Insertable b-Layer ( IBL ) is the innermost layer of the ATLAS tracking system. It consists of planar pixel modules in the central region and 3D modules at two extremities. We use the cluster length distributions in 3D sensor modules of the IBL to determine the number of primary charged particles per event and suppress backgrounds. This Pixel Cluster Counting ( PCC ) algorithm provides a bunch-by-bunch luminosity measurement. An accurate luminosity measurement is a key component for precision measurements at the Large Hadron Collider and one of the largest uncertainties on the luminosity determination in ATLAS arises from the long-term stability of the measurement technique. The comparison of the PCC algorithm with other existing algorithms provides key insights in assessing and reducing such uncertainty.

  13. Direct high-precision measurement of the effective optical path length of multi-pass cell with optical frequency domain reflectometer.

    Science.gov (United States)

    Du, Z H; Gao, H; Cao, X H

    2016-01-11

    Multi-pass cells (MPCs) are commonly used in trace-gas detection and weak spectrum measurement. It is essential to accomplish a high-precision measurement of MPCs' effective optical path length (EOPL). A direct high-precision measuring method of MPCs' EOPL with optical frequency domain reflectometer (OFDR) was reported and demonstrated in this paper. Several important parameters of a MPC, such as EOPL and base length, were derived with high-precision by identifying the complicated signal of OFDR. The MPC's EOPL was also verified with the prevailing absorbance method. The results showed that the MPC's EOPL measured by each of these two methods is highly consistent. However, the relative uncertainty with the OFDR dramatically decreased 2 orders of magnitude (about 0.0085%) than that with the absorbance method. It demonstrated that the OFDR method with fewer measurement links is more conducive to a direct measurement. The performances of beam spread and stray light in the White-cell were also evaluated with the method.

  14. Emittance preservation during bunch compression with a magnetized beam

    Energy Technology Data Exchange (ETDEWEB)

    Stratakis, Diktys [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-09-02

    The deleterious effects of coherent synchrotron radiation (CSR) on the phase-space and energy spread of high-energy beams in accelerator light sources can significantly constrain the machine design and performance. In this paper, we present a simple method to preserve the beam emittance by means of using magnetized beams that exhibit a large aspect ratio on their transverse dimensions. The concept is based on combining a finite solenoid field where the beam is generated together with a special optics adapter. Numerical simulations of this new type of beam source show that the induced phase-space density growth can be notably suppressed to less than 1% for any bunch charge. This work elucidates the key parameters that are needed for emittance preservation, such as the required field and aspect ratio for a given bunch charge.

  15. MD210 Note: Creation of Hollow Bunches in the PSB

    CERN Document Server

    Oeftiger, Adrian; Findlay, Alan James; Hancock, Steven; Rumolo, Giovanni; CERN. Geneva. ATS Department

    2016-01-01

    MD210 aims for the creation of longitudinally hollow bunches in the CERN PS Booster. The first three sessions have been carried out using the radial loop feedback system in order to drive the beam on a dipolar parametric resonance (instead of the phase loop). It has been found that the damping by the phase loop inhibits the excitation of the resonance to a major extent. The hollow distributions generated under these circumstances fail to reach a satisfying bunching factor. Nonetheless, proving the principally successful application of this technique to the PS Booster promises good results once the phase loop system supports trim functions. The approach, actions and detailed results of the first three MD sessions are presented in this paper.

  16. Compensating tune spread induced by space charge in bunched beams

    Energy Technology Data Exchange (ETDEWEB)

    Litvinenko, V.; Wang, G.

    2015-05-03

    The effects of space charge play a significant role in modern-day accelerators, frequently constraining the beam parameters attainable in an accelerator or in an accelerator chain. They also can limit the luminosity of hadron colliders operating either at low energies or with sub-TeV high-brightness hadron beams. The latter is applied for strongly cooled proton and ion beams in eRHIC – the proposed future electron-ion collider at Brookhaven National Laboratory. Using an appropriate electron beam would compensate both the tune shift and the tune spread in the hadron beam in a coasting beam. But these methods cannot compensate space charge tune spread in a bunched hadron beam. In this paper we propose and evaluate a novel idea of using a co-propagating electron bunch with mismatched longitudinal velocity to compensate the space charge induced tune-shift and tune spread.

  17. Effective composting of empty fruit bunches using potential Trichoderma strains

    OpenAIRE

    Shafiquzzaman Siddiquee; Saili Nur Shafawati; Laila Naher

    2017-01-01

    Oil palm fibres are easy to degrade, eco-friendly in nature and once composted, they can be categorized under nutrient-enriched biocompost. Biocompost is not only a good biofertilizer but also a good biocontrol agent against soil-borne pathogens. In this research, experimental works on the composting of empty fruit bunches (EFB) from the oil palm industry were conducted using two potential Trichoderma strains. Analysis of pH initially found the soils to be slightly acidic. However, after comp...

  18. Perception of a Japanese vowel length contrast by Japanese and American English listeners: behavioral and electrophysiological measures.

    Science.gov (United States)

    Hisagi, Miwako; Shafer, Valerie L; Strange, Winifred; Sussman, Elyse S

    2010-11-11

    This study examined the role of automatic selective perceptual processes in native and non-native listeners' perception of a Japanese vowel length contrast (tado vs. taado), using multiple, natural-speech tokens of each category as stimuli in a "categorial oddball" design. Mismatch negativity (MMN) was used to index discrimination of the temporally-cued vowel contrast by naïve adult American listeners and by a native Japanese-speaking control group in two experiments in which attention to the auditory input was manipulated: in Exp 1 (Visual-Attend), listeners silently counted deviants in a simultaneously-presented visual categorial oddball shape discrimination task; in Exp 2 (Auditory-Attend), listeners attended to the auditory input and implicitly counted target deviants. MMN results showed effects of language experience and attentional focus: MMN amplitudes were smaller for American compared to Japanese listeners in the Visual-Attend Condition and for the American listeners in the Visual compared to Auditory-Attend Condition. Subtle differences in topography were also seen, specifically in that the Japanese group showed more robust responses than the American listeners at left hemisphere scalp sites that probably index activity from the superior temporal gyrus. Follow-up behavioral discrimination tests showed that Americans discriminated the contrast well above chance, but more poorly than did Japanese listeners. This pattern of electrophysiological and behavioral results supports the conclusion that early experience with phonetic contrasts of a language results in changes in neural representations in the auditory cortex that allow for more robust automatic, phonetic processing of native-language speech input. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. Ion bunch stacking in a Penning trap after purification in an electrostatic mirror trap

    CERN Document Server

    Rosenbusch, M; Blaum, K; Borgmann, Ch; Kreim, S; Lunney, D; Manea, V; Schweikhard, L; Wienholtz, F; Wolf, R N

    2014-01-01

    The success of many measurements in analytical mass spectrometry as well as in precision mass determinations for atomic and nuclear physics is handicapped when the ion sources deliver ``contaminations'', i.e., unwanted ions of masses similar to those of the ions of interest. In particular, in ion-trapping devices, large amounts of contaminant ions result in significant systematic errors-if the measurements are possible at all. We present a solution for such cases: The ions from a quasi-continuous source are bunched in a linear radio-frequency-quadrupole ion trap, separated by a multi-reflection time-of-flight section followed by a Bradbury-Nielsen gate, and then captured in a Penning trap. Buffer-gas cooling is used to damp the ion motion in the latter, which allows a repeated opening of the Penning trap for a stacking of mass-selected ion bunches. Proof-of-principle demonstrations have been performed with the ISOLTRAP setup at ISOLDE/CERN, both with Cs-133(+) ions from an off-line ion source and by applicati...

  20. Creation of Hollow Bunches using a Double Harmonic RF system

    CERN Document Server

    Carli, Christian

    2001-01-01

    The main motivation for the creation of hollow bunches in the PSB is to increase the bunching factor at transfer to the PS. Due to the reduction of the peak current and direct transverse space charge forces, one expects less blow up and losses at low energy in the PS. Thus, it does not matter when the hollow distribution in longitudinal phase space is created in the PSB cycle. We propose methods involving the h=1 and h=2 RF systems available in the PSB. The first method is based on controlled blow up by recombination of the bunch in one bucket, with another empty bucket. By appropriate adjustment of the phase between the two RF systems, more empty phase space can be inserted close to the centre creating a hollow distribution. The second method is based on a redistribution of phase space. The beam is transferred from one h=2 sub-bucket to the other and, during that process, regions from the centre with high density and from the periphery are exchanged. Simulations of both methods, based on tracking of particle...