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Sample records for current short bunch

  1. Measurement of short bunches

    International Nuclear Information System (INIS)

    Wang, D.X.

    1996-01-01

    In recent years, there has been increasing interest in short electron bunches for different applications such as short wavelength FELs, linear colliders, and advanced accelerators such as laser or plasma wakefield accelerators. One would like to meet various requirements such as high peak current, low momentum spread, high luminosity, small ratio of bunch length to plasma wavelength, and accurate timing. Meanwhile, recent development and advances in RF photoinjectors and various bunching schemes make it possible to generate very short electron bunches. Measuring the longitudinal profile and monitoring bunch length are critical to understand the bunching process and longitudinal beam dynamics, and to commission and operate such short bunch machines. In this paper, several commonly used measurement techniques for subpicosecond bunches and their relative advantages and disadvantages are discussed. As examples, bunch length related measurements at Jefferson Lab are presented. At Jefferson Lab, bunch lengths as short as 84 fs have been systematically measured using a zero-phasing technique. A highly sensitive Coherent Synchrotron Radiation (CSR) detector has been developed to noninvasively monitor bunch length for low charge bunches. Phase transfer function measurements provide a means of correcting RF phase drifts and reproducing RF phases to within a couple of tenths of a degree. The measurement results are in excellent agreement with simulations. A comprehensive bunch length control scheme is presented. (author)

  2. Measurement of short bunches

    International Nuclear Information System (INIS)

    Wang, D.X.

    1996-01-01

    In recent years, there has been increasing interest in short electron bunches for different applications such as short wavelength FELs, linear colliders, and advanced accelerators such as laser or plasma wakefield accelerators. One would like to meet various requirements such as high peak current, low momentum spread, high luminosity, small ratio of bunch length to plasma wavelength, and accurate timing. Meanwhile, recent development and advances in RF photoinjectors and various bunching schemes make it possible to generate very short electron bunches. Measuring the longitudinal profile and monitoring bunch length are critical to understand the bunching process and longitudinal beam dynamics, and to commission and operate such short bunch machines. In this paper, several commonly used measurement techniques for subpicosecond bunches and their relative advantages and disadvantages are discussed. As examples, bunch length related measurements at Jefferson lab are presented. At Jefferson Lab, bunch lengths s short as 84 fs have been systematically measured using a zero-phasing technique. A highly sensitive Coherent Synchrotron Radiation (CSR) detector has been developed to noninvasively monitor bunch length for low charge bunches. Phase transfer function measurements provide a means of correcting RF phase drifts and reproducing RF phases to within a couple of tenths of a degree. The measurement results are in excellent agreement with simulations. A comprehensive bunch length control scheme is presented

  3. Certain features of FELs with short bunches

    International Nuclear Information System (INIS)

    Lebedev, A.N.

    2006-01-01

    The report is devoted to physics of free electron lasers operating in the short-wave domain where the bunch length could be less than the undulator length in the proper frame. Then the current component of the signal is locked within the bunch as in a cavity, while the electromagnetic component propagates freely. In contrast with gyrotrons where this regime can be of interest only for wavelengths comparable with the bunch length, we consider short waves in a bunch of arbitrary profile. Both amplification of an external harmonic signal and SASE regime, i.e. selective amplification of proper noises, are investigated

  4. Longitudinal Diagnostics for Short Electron Beam Bunches

    Energy Technology Data Exchange (ETDEWEB)

    Loos, H.; /SLAC

    2010-06-11

    Single-pass free electron lasers require high peak currents from ultra-short electron bunches to reach saturation and an accurate measurement of bunch length and longitudinal bunch profile is necessary to control the bunch compression process from low to high beam energy. The various state-of-the-art diagnostics methods from ps to fs time scales using coherent radiation detection, RF deflection, and other techniques are presented. The use of linear accelerators as drivers for free electron lasers (FEL) and the advent of single-pass (SASE) FELs has driven the development of a wide range of diagnostic techniques for measuring the length and longitudinal distribution of short and ultra-short electron bunches. For SASE FELs the radiation power and the length of the undulator needed to achieve saturation depend strongly on the charge density of the electron beam. In the case of X-ray FELs, this requires the accelerator to produce ultra-high brightness beams with micron size transverse normalized emittances and peak currents of several kA through several stages of magnetic bunch compression. Different longitudinal diagnostics are employed to measure the peak current and bunch profile along these stages. The measurement techniques can be distinguished into different classes. Coherent methods detect the light emitted from the beam by some coherent radiation process (spectroscopic measurement), or directly measure the Coulomb field traveling with the beam (electro-optic). Phase space manipulation techniques map the time coordinate onto a transverse dimension and then use conventional transverse beam diagnostics (transverse deflector, rf zero-phasing). Further methods measure the profile or duration of an incoherent light pulse emitted by the bunch at wavelengths much shorted than the bunch length (streak camera, fluctuation technique) or modulate the electron beam at an optical wavelength and then generate a narrow bandwidth radiation pulse with the longitudinal profile of

  5. Design of BEPCII bunch current monitor system

    International Nuclear Information System (INIS)

    Zhang Lei; Ma Huizhou; Yue Junhui; Lei Ge; Cao Jianshe; Ma Li

    2008-01-01

    BEPC II is an electron-positron collider designed to run under multi-bunches and high beam current condition. The accelerator consists of an electron ring, a positron ring and a linear injector. In order to achieve the target luminosity and implement the equal bunch charge injection, the Bunch Current Monitor (BCM) system is built on BEPC II. The BCM system consists of three parts: the front-end circuit, the bunch current acquisition system and the bucket selection system. The control software of BCM is based on VxWorks and EPICS. With the help of BCM system, the bunch current in each bucket can be monitored in the Central Control Room. The BEPC II timing system can also use the bunch current database to decide which bucket needs to refill to implement 'top-off' injection. (authors)

  6. Introduction to impedance for short relativistic bunches

    International Nuclear Information System (INIS)

    Morton, P.L.

    1993-02-01

    The purpose of this paper is to introduce the concept of impedance to calculate the wake field forces left behind by a short bunch which travels at relativistic speed through a structure with discontinuities. We will try to be as intuitive as possible and leave the more rigorous derivations to the second paper on this subject by J. Wang

  7. Short bunch wake potentials for a chain of TESLA cavities

    International Nuclear Information System (INIS)

    Novokhatski, Alexander; Mosnier, Alban

    2014-01-01

    The modification of wake fields from a single cavity to a quasi-periodic structure of cavities is of great concern, especially for applications using very short bunches. We extend our former study (Novokhatski, 1997 [1]). A strong modification of wake fields along a train of cavities was clearly found for bunch lengths lower than 1 mm. In particular, the wakes induced by the bunch, as it proceeds down the successive cavities, decrease in amplitude and become more linear around the bunch center, with a profile very close to the integral of the charge density. The loss factor, decreasing also with the number of cells, becomes independent of bunch length for very short bunches and tends asymptotically to a finite value. This nice behavior of wake fields for short bunches presents good opportunity for application of very short bunches in Linear Colliders and X-ray Free Electron Lasers

  8. Improvement of bunch-by-bunch beam current detection system in Hefei light source

    International Nuclear Information System (INIS)

    Zheng Kai; Wang Junhua; Liu Zuping; Li Weimin; Zhou Zeran; Yang Yongliang; Huang Longjun; Chen Yuanbo

    2006-01-01

    Bunch-by-bunch beam current detection system is an important facility in the multibunch storage ring. In this paper, the established bunch-by-bunch beam current detection systems for the accelerator such as Cornell, SLAC and KEKB were compared and studied. The design of the bunch-by-bunch beam current detection system for HLS, which was based on the bunch-by-bunch tracing measurement system in HLS was given. Both demodulation by sine wave and square were applied in this paper, the deviation of the detect system was determined by the longitudinal oscillation. Compared the data acquired from ADC with the data from DCCT, the ADC data was scaled by the bunch current. The standard deviations of linear fit were about 1%, and the standard deviations of polynomial fit were less than 0.5% in both sine wave and square wave demodulation. Some analysis of the measurement results also had been shown in this paper. (authors)

  9. 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.

  10. 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.

  11. Short bunch length detector for ion beam with high bunch density

    International Nuclear Information System (INIS)

    Tron, A.M.; Shako, V.V.

    1993-01-01

    The secondary electron rf monitors for short ion bunch phase distribution measurements are presented. Construction particularities of the monitors, influence of space charge of both the primary and the secondary electron beams on the phase resolution, thermal regime of the target during beam-target interaction are considered

  12. 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.

  13. Electric-current-induced step bunching on Si(111)

    International Nuclear Information System (INIS)

    Homma, Yoshikazu; Aizawa, Noriyuki

    2000-01-01

    We experimentally investigated step bunching induced by direct current on vicinal Si(111)'1x1' surfaces using scanning electron microscopy and atomic force microscopy. The scaling relation between the average step spacing l b and the number of steps N in a bunch, l b ∼N -α , was determined for four step-bunching temperature regimes above the 7x7-'1x1' transition temperature. The step-bunching rate and scaling exponent differ between neighboring step-bunching regimes. The exponent α is 0.7 for the two regimes where the step-down current induces step bunching (860-960 and 1210-1300 deg. C), and 0.6 for the two regimes where the step-up current induces step bunching (1060-1190 and >1320 deg. C). The number of single steps on terraces also differs in each of the four temperature regimes. For temperatures higher than 1280 deg. C, the prefactor of the scaling relation increases, indicating an increase in step-step repulsion. The scaling exponents obtained agree reasonably well with those predicted by theoretical models. However, they give unrealistic values for the effective charges of adatoms for step-up-current-induced step bunching when the 'transparent' step model is used

  14. 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.

  15. Towards highest peak intensities for ultra-short MeV-range ion bunches

    Science.gov (United States)

    Busold, Simon; Schumacher, Dennis; Brabetz, Christian; Jahn, Diana; Kroll, Florian; Deppert, Oliver; Schramm, Ulrich; Cowan, Thomas E.; Blažević, Abel; Bagnoud, Vincent; Roth, Markus

    2015-01-01

    A laser-driven, multi-MeV-range ion beamline has been installed at the GSI Helmholtz center for heavy ion research. The high-power laser PHELIX drives the very short (picosecond) ion acceleration on μm scale, with energies ranging up to 28.4 MeV for protons in a continuous spectrum. The necessary beam shaping behind the source is accomplished by applying magnetic ion lenses like solenoids and quadrupoles and a radiofrequency cavity. Based on the unique beam properties from the laser-driven source, high-current single bunches could be produced and characterized in a recent experiment: At a central energy of 7.8 MeV, up to 5 × 108 protons could be re-focused in time to a FWHM bunch length of τ = (462 ± 40) ps via phase focusing. The bunches show a moderate energy spread between 10% and 15% (ΔE/E0 at FWHM) and are available at 6 m distance to the source und thus separated from the harsh laser-matter interaction environment. These successful experiments represent the basis for developing novel laser-driven ion beamlines and accessing highest peak intensities for ultra-short MeV-range ion bunches. PMID:26212024

  16. Towards highest peak intensities for ultra-short MeV-range ion bunches

    Science.gov (United States)

    Busold, Simon; Schumacher, Dennis; Brabetz, Christian; Jahn, Diana; Kroll, Florian; Deppert, Oliver; Schramm, Ulrich; Cowan, Thomas E.; Blažević, Abel; Bagnoud, Vincent; Roth, Markus

    2015-07-01

    A laser-driven, multi-MeV-range ion beamline has been installed at the GSI Helmholtz center for heavy ion research. The high-power laser PHELIX drives the very short (picosecond) ion acceleration on μm scale, with energies ranging up to 28.4 MeV for protons in a continuous spectrum. The necessary beam shaping behind the source is accomplished by applying magnetic ion lenses like solenoids and quadrupoles and a radiofrequency cavity. Based on the unique beam properties from the laser-driven source, high-current single bunches could be produced and characterized in a recent experiment: At a central energy of 7.8 MeV, up to 5 × 108 protons could be re-focused in time to a FWHM bunch length of τ = (462 ± 40) ps via phase focusing. The bunches show a moderate energy spread between 10% and 15% (ΔE/E0 at FWHM) and are available at 6 m distance to the source und thus separated from the harsh laser-matter interaction environment. These successful experiments represent the basis for developing novel laser-driven ion beamlines and accessing highest peak intensities for ultra-short MeV-range ion bunches.

  17. 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

  18. Bunching phase evolution of short-pulse FEL oscillator system

    CERN Document Server

    Song, S B; Choi, D I

    2000-01-01

    We studied numerically the short-pulse FEL oscillator system using properly defined bunching phase theta sub B and PSI sub B. In stable operation, we have found that the optical field 'locks' the phase to pi/2 at the trailing edge, which gives the maximum gain. Moreover, electrons can be detrapped from ponderomotive bucket due to the spatial variation of the optical field, and this detrapping effect is a major cause of the limit cycle oscillation of the system. The 'bump' of the output power during the amplification usually exists at the near-perfect cavity synchronism regime, which can be explained as the change of the matching condition between electron micropulse and optical pulse.

  19. Generation of ultra-short relativistic-electron-bunch by a laser wakefield

    NARCIS (Netherlands)

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

    2003-01-01

    The possibility of the generation of an ultra-short (about one micron long) relativistic (up to a few GeVs) electron-bunch in a moderately nonlinear laser wakefield excited in an underdense plasma by an intense laser pulse is investigated. The ultra-short bunch is formed by trapping, effective

  20. The impact of coherent synchrotron radiation on the beam transport of short bunches

    International Nuclear Information System (INIS)

    Li, R.

    1999-01-01

    Designs for next-generation accelerator, such as future linear colliders and short-wavelength FEL drivers, require beams of short (mm-length or smaller) bunches and high charge (nC-regime). As such a high charge microbunch traverses magnetic bends, the curvature effect on the bunch self-interaction, by way of coherent synchrotron radiation (CSR) and space charge force, may cause serious emittance degradation. This impact of CSR on the beam transport of short bunches has raised significant concern in the design of future machines and led to extensive investigations. This paper reviews some of the recent progress in the understanding of the CSR effect, presents analysis of and computational work on the CSR impact on short bunch transport, and addresses remaining issues

  1. Influence of laser parameters on the relativistic short electron bunches dynamics in linear accelerators based on RF-guns and development of associated diagnostics

    International Nuclear Information System (INIS)

    Vinatier, T.

    2015-01-01

    My thesis investigates dynamics and diagnostics related to short electron bunches, namely whose rms duration is not directly measurable by an electronic method locating the border at a few tens of picoseconds. The short nature of the bunch and the necessity of a high peak current for the applications imply strong space-charge forces leading to a degradation of beam properties, as its transverse emittance and duration. The main difficulty is to characterize, model and take into account these effects. The chapter 2 consists in the measurements of several properties of these bunches: charge, transverse emittance, energy and duration. The originality of my work is that I use simple methods, both on the theoretical (analytical at maximum) and technological (using only common elements of electron accelerators) point of view. I have developed a method of charge measurement from the measurement of the light intensity emitted by a scintillating screen following the interaction with an electron beam. I have also developed a method to measure the bunch mean energy with a steering magnet and a scintillating screen, via the displacement of the bunch centroid as a function of the field of the steering magnet. I have also adapted multi-parametric methods to measure the transverse emittance and duration of electron bunches. These indirect methods allow the determination of these properties from the measurement of other more accessible properties: the transverse dimensions for the transverse emittance and the energy spread for the duration. The chapter 3 consists in the comparison of the properties of short electron beams, single or longitudinally modulated, generated by 3 different methods: Injection of a short or longitudinally modulated laser pulse in an RF-gun; Magnetic compression in a chicane; and RF-compression in an accelerating structure (Velocity Bunching). I have shown that, at equal conditions of charge, the generation of short bunches thanks to a short laser pulse

  2. Transient Resistive Wall Wake for Very Short Bunches

    International Nuclear Information System (INIS)

    Stupakov, G.; SLAC

    2005-01-01

    The catch up distance for the resistive wall wake in a round pipe is approximately equal to the square of the pipe radius divided by the bunch length. The standard formulae for this wake are applicable at distances much larger than the catch up distance. In this paper, we calculate the resistive wall wake at distances compared with the catch up distance assuming a constant wall conductivity

  3. Ultra-short coherent terahertz radiation from ultra-short dips in electron bunches circulating in a storage ring

    International Nuclear Information System (INIS)

    Yamamoto, N.; Shimada, M.; Adachi, M.; Zen, H.; Tanikawa, T.; Taira, Y.; Kimura, S.; Hosaka, M.; Takashima, Y.; Takahashi, T.; Katoh, M.

    2011-01-01

    Terahertz (THz) coherent synchrotron radiation (CSR) is emitted not only from ultra-short electron bunches, but also from electron bunches with micro-structures. Formation of micro-structures at the sub-picosecond scale in electron bunches by a laser slicing technique is experimentally studied through observation of the THz CSR. The THz CSR spectrum was found to depend strongly on the intensity and the pulse width of the laser. The results agreed qualitatively with a numerical simulation. It was suggested that the evolution of the micro-structure during CSR emission is important under some experimental conditions.

  4. 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.

  5. Analytical formulas for short bunch wakes in a flat dechirper

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-15

    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 μm from one jaw in one dechirper section, one can achieve a 3 MV transverse kick differential over a 30 μm length.

  6. Analytical formulas for short bunch wakes in a flat dechirper

    International Nuclear Information System (INIS)

    Bane, Karl; Stupakov, Gennady; Zgorodnov, Igor

    2016-03-01

    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 μm from one jaw in one dechirper section, one can achieve a 3 MV transverse kick differential over a 30 μm length.

  7. Acceleration of a high-current single bunch in a linear accelerator

    International Nuclear Information System (INIS)

    Takeda, Seishi

    1984-01-01

    Some problems associated with the feasibility of an electron-positron linear collider with colliding energy of about 1x1 TeV are discussed. The first problem is related to the generation of high-current single bunch. A quasi-relativistic electron beam from an electron gun is injected into one bucket of the accelerating fields, in opposition to the longitudinal defocusing due to the space-charge effect. For generating a high-current single bunch, the beam bunching by means of the velocity modulation with a subharmonic prebuncher (SHPB) is indispensable. Three existing second generation single bunch electron linear accelerators (SLC, ANL and ISLR-Osaka Univ.) are briefly described. The results of the simulation of subharmonic-bunching is also reported. The second problem is associated with the physics of accelerating high-current single bunch. The longitudinal and transverse wake fields generated by a bunch-cavity interaction and the energy spread of the single bunch are analyzed and discussed. (Aoki, K.)

  8. Short electron bunches generated by perpendicularly crossing laser pulses.

    Czech Academy of Sciences Publication Activity Database

    Horný, Vojtěch; Petržílka, Václav; Klimo, Ondřej; Krůs, Miroslav

    2017-01-01

    Roč. 24, č. 10 (2017), č. článku 103125. ISSN 1070-664X R&D Projects: GA ČR GA15-03118S; GA MŠk(CZ) LM2015083; GA MŠk(CZ) CZ.02.1.01/0.0/0.0/16_013/0001552; GA MŠk LQ1606; GA MŠk(CZ) LD14089 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:61389021 ; RVO:68378271 Keywords : Laser pulses * Particle beam bunching * Plasma simulation * Particle acceleration * Lasers * Particle-in-cell metthod * Particle beams * Electrostatics Subject RIV: BL - Plasma and Gas Discharge Physics; BL - Plasma and Gas Discharge Physics (FZU-D) OBOR OECD: Fluids and plasma physics (including surface physics); Fluids and plasma physics (including surface physics) (FZU-D) Impact factor: 2.115, year: 2016 http://aip.scitation.org/doi/10.1063/1.5007889

  9. 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%.

  10. A multi-frequency approach to free electron lasers driven by short electron bunches

    International Nuclear Information System (INIS)

    Piovella, Nicola

    1997-01-01

    A multi-frequency model for free electron lasers (FELs), based on the Fourier decomposition of the radiation field coupled with the beam electrons, is discussed. We show that the multi-frequency approach allows for an accurate description of the evolution of the radiation spectrum, also when the FEL is driven by short electron bunches, of arbitrary longitudinal profile. We derive from the multi-frequency model, by averaging over one radiation period, the usual FEL equations modelling the slippage between radiation and particles and describing the super-radiant regime in high-gain FELs. As an example of application of the multi-frequency model, we discuss the coherent spontaneous emission (CSE) from short electron bunches

  11. Threshold current for the transverse single-bunch instability in PEP

    International Nuclear Information System (INIS)

    Wilson, P.B.; Rivkin, L.

    1982-08-01

    For a bunch with charge q moving in a storage ring under the influence of a constant dipole wake potential of amplitude W 1 and constant transverse beta-function with amplitude β/sub t/, the two-macroparticle model for the transverse single-bunch instability predicts a threshold current. When this work is completed, an absolute prediction of the threshold current will be possible, at least to the extent that the transverse impedance of the rf cavities dominates the total impedance of the ring. A preliminary estimate of the fraction of the total dipole impedance exterior to the rf cavities is the purposes of this note. 4 refs., 3 tabs

  12. 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.

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

    International Nuclear Information System (INIS)

    Pompili, R; Anania, M P; Bellaveglia, M; Biagioni, A; Castorina, G; Chiadroni, E; Croia, M; Giovenale, D Di; Ferrario, M; Gallo, A; Gatti, G; Cianchi, A; Filippi, F; Giorgianni, F; Giribono, A; Lupi, S; Mostacci, A; Petrarca, M; Piersanti, L; Li, W

    2016-01-01

    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. (paper)

  14. Controlling nonlinear longitudinal space charge oscillations for high peak current bunch train generation

    Directory of Open Access Journals (Sweden)

    P. Musumeci

    2013-10-01

    Full Text Available The evolution of picosecond modulations of the longitudinal profile of an electron beam generated in an rf photoinjector is analyzed and optimized with the goal of obtaining high peak current electron bunch trains at very high frequencies (≥THz. Taking advantage of nonlinear longitudinal space charge forces, it is found that more than 500 A peak current 1 THz bunch trains can be generated using a standard 1.6 cell SLAC/UCLA/BNL rf gun. Postacceleration is used to freeze the longitudinal phase space dynamics after one half plasma oscillation. Applications range from tunable narrow bandwidth THz radiation generation to drivers for high frequency high gradient accelerators.

  15. Time domain numerical calculations of the short electron bunch wakefields in resistive structures

    Energy Technology Data Exchange (ETDEWEB)

    Tsakanian, Andranik

    2010-10-15

    The acceleration of electron bunches with very small longitudinal and transverse phase space volume is one of the most actual challenges for the future International Linear Collider and high brightness X-Ray Free Electron Lasers. The exact knowledge on the wake fields generated by the ultra-short electron bunches during its interaction with surrounding structures is a very important issue to prevent the beam quality degradation and to optimize the facility performance. The high accuracy time domain numerical calculations play the decisive role in correct evaluation of the wake fields in advanced accelerators. The thesis is devoted to the development of a new longitudinally dispersion-free 3D hybrid numerical scheme in time domain for wake field calculation of ultra short bunches in structures with walls of finite conductivity. The basic approaches used in the thesis to solve the problem are the following. For materials with high but finite conductivity the model of the plane wave reflection from a conducting half-space is used. It is shown that in the conductive half-space the field components perpendicular to the interface can be neglected. The electric tangential component on the surface contributes to the tangential magnetic field in the lossless area just before the boundary layer. For high conducting media, the task is reduced to 1D electromagnetic problem in metal and the so-called 1D conducting line model can be applied instead of a full 3D space description. Further, a TE/TM (''transverse electric - transverse magnetic'') splitting implicit numerical scheme along with 1D conducting line model is applied to develop a new longitudinally dispersion-free hybrid numerical scheme in the time domain. The stability of the new hybrid numerical scheme in vacuum, conductor and bound cell is studied. The convergence of the new scheme is analyzed by comparison with the well-known analytical solutions. The wakefield calculations for a number of

  16. The study of the possibility to use CAMEX chips in collider experiments with short bunch crossing time

    International Nuclear Information System (INIS)

    Aulchenko, V.M.; Chilingarov, A.G.; Serbo, V.V.; Titov, V.M.

    1993-01-01

    The study of the possibility to use CAMEX chips in several systems of the detector KEDR at the e + e - collider VEPP-4M was performed. The relatively short bunch crossing time at VEPP-4M 60 ns leads to some problems with the use of CAMEX in the standard mode. The different ways to overcome these difficulties are investigated and compared. (orig.)

  17. Design Studies for a High Current Bunching System for CLIC Test Facility (CTF3) Drive Beam

    CERN Document Server

    Thiery, Y.; Le Duff, J.

    2000-01-01

    A bunching system is proposed for the initial stage of CTF3 which consists of one (two) 3 GHz prebunchers and one 3 GHz travelling wave (TW) buncher with variable phase velocities. The electron beam is emitted from a 140 KV DC gun. Since the macropulse beam current (3.5 A) at the exit of the TW buncher is rather high, inside the TW buncher one has to take the beam loading effect into consideration. By using PARMELA, it is shown numerically that the bunching system can provide the bunches whose properties satisfy the design requirement of CTF3. The 0.8 m long TW buncher working at 2pi/3 mode has two phase velocities, 0.75 and 1. The dimensions of the caities in the two phase velocity regions are proposed considering the beam loading effect. The transient beam loading effect and the multibunch transverse instabilities are studied numerically, and it is concluded that higher order mode couplers should be installed in the TW buncher with the loaded quality factor of the dipole mode lower than 80.

  18. Radiative interaction of electrons in a short electron bunch moving in an undulator

    International Nuclear Information System (INIS)

    Saldin, E. L.; Schneidmiller, E. A.; Yurkov, M. V.

    1999-01-01

    This paper presents investigations of the longitudinal radiative force in an electron bunch. The model of the electron bunch assumes line density distribution. General formulas are presented for the calculation of the radiative force in the bunch moving along an arbitrary small-angle trajectory. The case of a motion in an undulator (wiggler) has been studied in detail. Analytical solutions are obtained for a rectangular and for a Gaussian bunch shape. It is shown that the rate of the bunch energy loss due to the radiative interaction is equal to the power of the coherent radiation in the far zone. Numerical estimations presented in the paper show that the effects of induced energy spread due to the radiative interaction can be important for free electron lasers operating in the infrared wavelength range

  19. Wall-Current-Monitor based Ghost and Satellite Bunch Detection in the CERN PS and the LHC Accelerators

    CERN Document Server

    Steinhagen, R J; Belleman, J; Bohl, T; Damerau, H

    2012-01-01

    While most LHC detectors and instrumentation systems are optimised for a nominal bunch spacing of 25 ns, the LHC RF cavities themselves operate at the 10th harmonic of the maximum bunch frequency. Due to the beam production scheme and transfers in the injector chain, part of the nominally ‘empty’ RF buckets may contain particles, referred to as ghost or satellite bunches. These populations must be accurately quantified for high-precision experiments, luminosity calibration and control of parasitic particle encounters at the four LHC interaction points. This contribution summarises the wall-current-monitor based ghost and satellite bunch measurements in CERN’s PS and LHC accelerators. Instrumentation set-up, post-processing and achieved performance are discussed.

  20. Design of high current bunching system and high power fast Faraday cup for high current LEBT at VECC

    International Nuclear Information System (INIS)

    Anuraag Misra, A.; Pandit, B.V.S.; Gautam Pal, C.

    2011-01-01

    A high current microwave ion source as described is currently operational at VECC. We are able to optimize 6.4 mA of proton current in the LEBT line of ion source. The cyclotron type of accelerators accept only a fraction of DC ion beam coming from ion source so a ion beam buncher is needed to increase the accepted current into the cyclotron. The buncher described in this paper is unique in its kind as it has to handle high beam loading power upto 400 W as it is designed to bunch few mA of proton beam currents at 80 keV beam energy. A sinusoidal quarter wave RF structure has been chosen to bunch the high current beam due to high Q achievable in comparison with other configurations. This buncher has been designed using CST Microwave studio 3D advanced code since the design frequency of our buncher is 42 MHz, we have provided the RF and vacuum window near the drift tube of buncher to avoid vacuum and multipacting problems and to keep maximum volume in air region. There is a provision of multipacting interlocks to shut off amplifier during multipacting. We have carried out a detailed electromagnetic and thermal design of the buncher in CST Microwave studio and simulated values of unloaded Q was calculated be 4000. We have estimated a power of 400 W to achieve gap (designed) voltage of 10 kV. This buncher is in advanced stage of fabrication. A high power fast Faraday cup is also designed to characterize the above mentioned high current bunching system. The fast Faraday cup is designed in 50 Ω coaxial geometry to transmit fast pulse of bunched ion beam. The design of Faraday cup was completed using ANSYS HFSS and a bandwidth of 1.75 GHz was achieved this faraday cup design was different from conventional Faraday cup design as we have designed the support and cooling lines at such a place on Faraday cup which do not disturb the electrical impedance of the cup. (author)

  1. Current-horn suppression for reduced coherent-synchrotron-radiation-induced emittance growth in strong bunch compression

    Directory of Open Access Journals (Sweden)

    T. K. Charles

    2017-03-01

    Full Text Available Control of coherent synchrotron radiation (CSR-induced emittance growth is essential in linear accelerators designed to deliver very high brightness electron beams. Extreme current values at the head and tail of the electron bunch, resulting from strong bunch compression, are responsible for large CSR production leading to significant transverse projected emittance growth. The Linac Coherent Light Source (LCLS truncates the head and tail current spikes which greatly improves free electron laser (FEL performance. Here we consider the underlying dynamics that lead to formation of current spikes (also referred to as current horns, which has been identified as caustics forming in electron trajectories. We present a method to analytically determine conditions required to avoid the caustic formation and therefore prevent the current spikes from forming. These required conditions can be easily met, without increasing the transverse slice emittance, through inclusion of an octupole magnet in the middle of a bunch compressor.

  2. SHORT-RANGE WAKEFIELD IN A FLAT PILLBOX CAVITY GENERATED BY A SUB-RELATIVISTIC BEAM BUNCH

    International Nuclear Information System (INIS)

    WANG, H.; PALMER, R.B.; GALLARDO, J.

    2001-01-01

    The short-range wakefield between two parallel conducting plates generated by a sub-relativistic beam bunch has been solved analytically by the image charge method in time domain. Comparing with the traditional modal analysis in frequency domain, this algorithm simplifies the mathematics and reveals in greater details the physics of electromagnetic field generation, propagation, reflection and causality. The calculated results have an excellent agreement with MAFIA and ABC1 simulations in all range of beam velocities

  3. Longitudinal Single-Bunch Instability in the ILC Damping Rings: Estimate of Current Threshold

    International Nuclear Information System (INIS)

    Venturini, Marco; Venturini, Marco

    2008-01-01

    Characterization of single-bunch instabilities in the International Linear Collider (ILC) damping rings (DRs) has been indicated as a high-priority activity toward completion of an engineering design. In this paper we report on a first estimate of the current thresholds for the instability using numerical and analytical models of the wake potentials associated with the various machine components. The numerical models were derived (upon appropriate scaling) from designs of the corresponding components installed in existing machines. The current thresholds for instabilities were determined by numerical solution of the Vlasov equation for the longitudinal dynamics. For the DR baseline lattice as of Feb. 2007 we find the critical current for instability to be safely above the design specifications leaving room for further optimization of the choice of the momentum compaction

  4. Generation and characterization of electron bunches with ramped current profiles in a dual-frequency superconducting linear accelerator.

    Science.gov (United States)

    Piot, P; Behrens, C; Gerth, C; Dohlus, M; Lemery, F; Mihalcea, D; Stoltz, P; Vogt, M

    2012-01-20

    We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radio frequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced ~700-MeV bunches have peak currents of the order of a kilo-Ampère. Data taken for various accelerator settings demonstrate the versatility of the method and, in particular, its ability to produce current profiles that have a quasilinear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak accelerating electric fields with transformer ratios larger than 2 in dielectric-lined waveguides. © 2012 American Physical Society

  5. Upgraded D OE calorimeter electronics for short Tevatron bunch space and the effect of pile-up on the W mass measurement

    International Nuclear Information System (INIS)

    Lokos, S.

    1992-11-01

    The high luminosity and short bunch spacing time of the upgraded Tevatron force the calorimeter to replace a significant part of the present electronics. The W mass measurement was used to study the pile-up effects

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

    International Nuclear Information System (INIS)

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

    2008-01-01

    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

  7. Bunch Compression Stability Dependence on RF Parameters

    CERN Document Server

    Limberg, T

    2005-01-01

    In present designs for FEL's with high electron peak currents and short bunch lengths, higher harmonic RF systems are often used to optimize the final longitudinal charge distributions. This opens degrees of freedom for the choice of RF phases and amplitudes to achieve the necessary peak current with a reasonable longitudinal bunch shape. It had been found empirically that different working points result in different tolerances for phases and amplitudes. We give an analytical expression for the sensitivity of the compression factor on phase and amplitude jitter for a bunch compression scheme involving two RF systems and two magnetic chicanes as well numerical results for the case of the European XFEL.

  8. Coasting beam theory applied to bunches

    International Nuclear Information System (INIS)

    Hereward, H.

    1975-01-01

    It is plausible to apply coasting beam criteria to bunches if one has short wavelength disturbances of the bunch and short memory wake fields, where short means short compared with a bunch length, for then one can argue that a piece of the bunch near the middle does not even know that the bunch has ends. Some other conditions probably required to validate this approach are discussed. The local Keil-Schnell criterion is derived from the local dispersion integral

  9. Simulations of the effects of a superconducting damping wiggler on a short bunched electron beam at ANKA

    Energy Technology Data Exchange (ETDEWEB)

    Gethmann, Julian; Bernhard, Axel; Blomley, Edmund; Hillenbrand, Steffen; Mueller, Anke-Susanne; Smale, Nigel [Karlsruher Institut fuer Technologie (KIT) (Germany); Zolotarev, Konstantin [Budker Institute of Nuclear Physics (Russian Federation)

    2016-07-01

    (As a part of the CLIC collaboration) A CLIC damping wiggler prototype has been installed at the ANKA synchrotron light source in order to validate the technical design of the 3 T superconducting conduction cooled wiggler and its cryostat and to cary out studies on beam dynamical aspects including collective effects. The latter one will be the main focus in this talk. Collective effects that will occur in damping rings are an issue in ANKA's short bunch operation as well. To simulate these effects the accelerator's model including its insertion device has to be very accurate. Such a model of the ANKA storage ring in short bunch operation mode has been developed in elegant. Simulations with the damping wiggler switched on and off have been performed in order to investigate effects of the wiggler on different machine parameters. These new results will be discussed with regard to the question if on the one hand the wiggler could be used for diagnostic purposes and if on the other hand the wiggler's impact on the beam dynamics is changed by the collective effects.

  10. 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...

  11. Bunched beam neutralization

    International Nuclear Information System (INIS)

    Gammel, G.M.; Maschke, A.W.; Mobley, R.M.

    1979-01-01

    One of the steps involved in producing an intense ion beam from conventional accelerators for Heavy Ion Fusion (HIF) is beam bunching. To maintain space charge neutralized transport, neutralization must occur more quickly as the beam bunches. It has been demonstrated at BNL that a 60 mA proton beam from a 750 kV Cockcroft--Walton can be neutralized within a microsecond. The special problem in HIF is that the neutralization must occur in a time scale of nanoseconds. To study neutralization on a faster time scale, a 40 mA, 450 kV proton beam was bunched at 16 MHz. A biased Faraday cup sampled the bunched beam at the position where maximum bunching was nominally expected, about 2.5 meters from the buncher. Part of the drift region, about 1.8 meters, was occupied by a series of Gabor lenses. In addition to enhancing beam transport by transverse focussing, the background cloud of electrons in the lenses provided an extra degree of neutralization. With no lens, the best bunch factor was at least 20. Bunch factor is defined here as the ratio of the distance between bunches to the FWHM bunch length. With the lens, it was hoped that the increased plasma frequency would decrease the neutralization time and cause an increase in the bunch factor. In fact, with the lens, the instantaneous current increased about three times, but the bunch factor dropped to about 10. Even with the lens, the FWHM of the bunches at the position of maximum bunching was still comparable to or less than the oscillation period of the surrounding electron plasma. Thus, the electron density in the lens must increase before neutralization could be effective in this case, or bunching should be done at a lower frequency

  12. Overview of Alternative Bunching and Current-shaping Techniques for Low-Energy Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Piot, Philippe [Northern Illinois U.

    2015-12-01

    Techniques to bunch or shape an electron beam at low energies (E <15 MeV) have important implications toward the realization of table-top radiation sources [1] or to the design of compact multi-user free-electron lasers[2]. This paper provides an overview of alternative methods recently developed including techniques such as wakefield-based bunching, space-charge-driven microbunching via wave-breaking [3], ab-initio shaping of the electron-emission process [4], and phase space exchangers. Practical applications of some of these methods to foreseen free-electron-laser configurations are also briefly discussed [5].

  13. COMMISSIONING OF THE DIGITAL TRANSVERSE BUNCH-BY-BUNCH FEEDBACK SYSTEM FOR THE TLS

    International Nuclear Information System (INIS)

    HU, K.H.; KUO, C.H.; CHOU, P.J.; LEE, D.; HSU, S.Y.; CHEN, J.; WANG, C.J.; HSU, K.T.; KOBAYASHI, K.; NAKAMURA, T.; CHAO, A.W.; WENG, W.T.

    2006-01-01

    Multi-bunch instabilities degrade beam quality through increased beam emittance, energy spread and even beam loss. Feedback systems are used to suppress multi-bunch instabilities associated with the resistive wall of the beam ducts, cavity-like structures, and trapped ions. A new digital transverse bunch-by-bunch feedback system has recently been commissioned at the Taiwan Light Source, and has replaced the previous analog system. The new system has the advantages that it enlarges the tune acceptance and improves damping for transverse instability at high currents, such that top-up operation is achieved. After a coupled-bunch transverse instability was suppressed, more than 350 mA was successfully stored during preliminary commissioning. In this new system, a single feedback loop simultaneously suppresses both horizontal and vertical multi-bunch instabilities. Investigating the characteristics of the feedback loop and further improving the system performances are the next short-term goals. The feedback system employs the latest generation of field-programmable gate array (FPGA) processor to process bunch signals. Memory has been installed to capture up to 250 msec of bunch oscillation signal, considering system diagnostics suitable to support various beam physics studies

  14. Short and long range gain monitoring of photomultipliers by means of a light pulser and an optical fibers bunch

    International Nuclear Information System (INIS)

    Besson, P.

    1989-01-01

    The gain monitoring of 8 XP3462 photomultipliers has been studied during a period of 3 months with a spark gap as a light pulser, an optical fibres bunch and 3 reference detectors. One of the reference PM is monitored thanks to a cristal of NaI irradiated by an 241 Am radioactive source, whereas the photodiode and its associated electronic is monitored thanks to a 57 Co source directly coupled to the junction. Two experimental methods have been tested. First the short term method consists in estimating several means of charge distributions and supposes the stability of different optical parameters like quantum efficiency or photoelectrons collection efficiency. The long term method consists in estimating several variances of charge distributions and supposes the validity, at first order, of photomultipliers' equations. In spite of unpropitious experimental conditions (tension switch off, no climatisation..), our results indicate that the short term method provides a precision of about 0.5% for the relative gain value but only during a short period which has been of 20 days. The long term method provides a precision of about 1.5% but is remained available during the 3 months of our experiment. This study has been developed for the new Neutrino oscillation program taking place near the Bugey nuclear plant and using 600 photomultipliers. The conclusions mentioned above are nevertheless valid for any particle detectors using photomultipliers [fr

  15. Simulations of Bunch Precompression at High Currents in the SLC Damping Rings

    International Nuclear Information System (INIS)

    Bane, K.L.F.; Minty, M.G.; Chao, A.W.

    2011-01-01

    In the Stanford Linear Collider (SLC) each beam, after leaving a damping ring, is compressed in the Ring-to-Linac (RTL) transfer line before entering the linear accelerator. At a bunch population of 4.0 x 10 10 particles, due to the limited energy acceptance of the RTL, approximately 15% of the beam has normally been lost. During the 1996 run, however, to eliminate this loss the bunch was partially precompressed in the damping ring, just before extraction; the beam loss in the RTL was reduced to almost zero. The operation and performance of precompression are presented by Minty et al. (1999). Also given is an analysis which, however, does not include the effects of the longitudinal wakefield on the beam dynamics. In this report we extend that analysis to include these effects.

  16. Test of a non-invasive bunch shape monitor at the GSI high current LINAC

    Energy Technology Data Exchange (ETDEWEB)

    Zwicker, Benjamin; Forck, Peter; Kester, Oliver [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Institut fuer Angewandte Physik, Goethe Universitaet Frankfurt (Germany); Dorn, Christoph; Kowina, Piotr [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany)

    2014-07-01

    At the heavy ion LINAC at GSI, a novel scheme of non-invasive Bunch Shape Monitor has been tested with several ion beams at 11.4 MeV/u. Caused by the beam impact on the residual gas, secondary electrons are liberated. These electrons are accelerated by an electrostatic field, transported through a sophisticated electrostatic energy analyzer and an rf-deflector, acting as a time-to-space converter. Finally a MCP detects the electron distribution. For the applied beam settings this Bunch Shape Monitor is able to obtain longitudinal profiles down to 400 ps with a resolution of 50 ps, corresponding to 2 degree of the 36 MHz acceleration frequency. During a long shutdown period for the GSI accelerators in 2013, the monitor underwent a general technical retrofit: Influence of the beam has been significantly reduced, due enhanced electrodes, new apertures have been installed to decrease electron scattering, sophisticated stepping motors will allow better image properties, a MCP shielding plate will prevent high background. Together with these improvements the achievements of the monitor are discussed.

  17. Worst Asymmetrical Short-Circuit Current

    DEFF Research Database (Denmark)

    Arana Aristi, Iván; Holmstrøm, O; Grastrup, L

    2010-01-01

    In a typical power plant, the production scenario and the short-circuit time were found for the worst asymmetrical short-circuit current. Then, a sensitivity analysis on the missing generator values was realized in order to minimize the uncertainty of the results. Afterward the worst asymmetrical...

  18. Towards highest peak intensities for ultra-short MeV-range ion bunches

    OpenAIRE

    Simon Busold; Dennis Schumacher; Christian Brabetz; Diana Jahn; Florian Kroll; Oliver Deppert; Ulrich Schramm; Thomas E. Cowan; Abel Blažević; Vincent Bagnoud; Markus Roth

    2015-01-01

    A laser-driven, multi-MeV-range ion beamline has been installed at the GSI Helmholtz center for heavy ion research. The high-power laser PHELIX drives the very short (picosecond) ion acceleration on ?m scale, with energies ranging up to 28.4?MeV for protons in a continuous spectrum. The necessary beam shaping behind the source is accomplished by applying magnetic ion lenses like solenoids and quadrupoles and a radiofrequency cavity. Based on the unique beam properties from the laser-driven so...

  19. Oil Palm Empty Fruit Bunches (OPEFB: Existing Utilization and Current Trends Bio Refinery in Indonesia

    Directory of Open Access Journals (Sweden)

    Rame

    2018-01-01

    Full Text Available In a future carbon-constrained global economy, the use of fossil fuels will be restricted. Biomass resources will be increased demand for renewable products. Oil Palm Empty Fruit Bunches (OPEFB can be used as lignocellulose feedstock. The production of biofuels from lignocellulose feedstock can be achieved through biochemical or thermo-chemical routes. OPEFB contain chemical blocks of cellulose, hemicellulose and lignocellulose. Due to these substances, OPEFB can be converted into bio-products and chemical. Special attention to biorefinery approach that is present at relatively high potential in bio-products such as polymers, nutraceuticals, chemical building blocks, biofuels, and bioenergy. Different utilization types were considered and reviewed, and the most common and efficient process were discussed. In general, there is no single product which could be considered a solution to the utilization of managing OPEFB – in this review a number of product are more economic, effective and environmentally friendly.

  20. Oil Palm Empty Fruit Bunches (OPEFB): Existing Utilization and Current Trends Bio Refinery in Indonesia

    Science.gov (United States)

    Rame

    2018-02-01

    In a future carbon-constrained global economy, the use of fossil fuels will be restricted. Biomass resources will be increased demand for renewable products. Oil Palm Empty Fruit Bunches (OPEFB) can be used as lignocellulose feedstock. The production of biofuels from lignocellulose feedstock can be achieved through biochemical or thermo-chemical routes. OPEFB contain chemical blocks of cellulose, hemicellulose and lignocellulose. Due to these substances, OPEFB can be converted into bio-products and chemical. Special attention to biorefinery approach that is present at relatively high potential in bio-products such as polymers, nutraceuticals, chemical building blocks, biofuels, and bioenergy. Different utilization types were considered and reviewed, and the most common and efficient process were discussed. In general, there is no single product which could be considered a solution to the utilization of managing OPEFB - in this review a number of product are more economic, effective and environmentally friendly.

  1. 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.

  2. Self-bunching electron guns

    Science.gov (United States)

    Mako, Frederick M.; Len, L. K.

    1999-05-01

    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, in a microwave cavity, self-bunching, cold electron emission, long life, and tolerance to contamination. The cold process is based on secondary electron emission. FMT has studied using simulation codes the resonant bunching process which gives rise to high current densities (0.01-5 kA/cm2), high charge bunches (up to 500 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 micro-bunches at ˜20 A/cm2 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 μs-long macro-pulses. Approximately 5.8×1013 micro-bunches or 62,000 coulombs have passed through this gun and it is still working fine. The second project, the S-Band MPG, is now operational. It is functioning at a frequency of 2.85 GHz, a repetition rate of 30 Hz, with a 2 μs-long macro-pulse. It produces about 45 A in the macro-pulse. The third project is a 34.2 GHz frequency-multiplied source driven by an X-Band MPG. A point design was performed at an rf output power of 150 MW at 34.2 GHz. The resulting system efficiency is 53% and the gain is 60 dB. The system efficiency includes the input cavity efficiency, input driver efficiency (a 50 MW klystron at 11.4 GHz), output cavity efficiency, and the post-acceleration efficiency.

  3. Measurement of femtosecond electron bunches

    International Nuclear Information System (INIS)

    Wang, D. X.; Krafft, G. A.; Sinclair, C. K.

    1997-01-01

    Bunch lengths as short as 84 fs (rms) have been measured at Jefferson Lab using a zero-phasing RF technique. To the best of our knowledge, this is the first accurate bunch length measurement in this regime. In this letter, an analytical approach for computing the longitudinal distribution function and bunch length is described for arbitrary longitudinal and transverse distributions. The measurement results are presented, which are in excellent agreement with numerical simulations

  4. Bunch by bunch feedback systems

    International Nuclear Information System (INIS)

    Tobiyama, Makoto

    2006-01-01

    Outlines of bunch-by-bunch feedback systems for suppressing multibunch instabilities in electron/positron storage rings are presented. The design principles and functions of the feedback components are reviewed. Recent topics of applying very fast and dense FPGA as feedback signal processor are also shown. (author)

  5. Development of a diamond detector for temporal profile measurements of intense, short ion bunches within the LIGHT project

    Energy Technology Data Exchange (ETDEWEB)

    Jahn, Diana [Technische Universitaet Darmstadt (Germany); Traeger, Michael; Kis, Mladen [GSI Helmholtzzentrum fuer Schwerionenforschung (Germany); Collaboration: LIGHT-Collaboration

    2016-07-01

    In the context of the Laser Ion Generation, Handling and Transport (LIGHT) research project at GSI, laser-driven ion acceleration and beam shaping are explored, combining a target normal sheath acceleration (TNSA) proton source with conventional accelerator technology. In the LIGHT experimental campaign in 2015, protons were accelerated via the TNSA mechanism, an energy of 7.8 MeV was selected and collimated with a pulsed solenoid and injected into a rf cavity. Through phase focusing, temporally compressed proton bunches were generated to a pulse length of <240 ps (FWHM) with up to 5 x 10{sup 8} particles in a single bunch at a distance of 6 m from the source. An ultrafast diamond detector has been specially developed to measure the temporal profile of these bunches and will be presented.

  6. Conditioning of BPM pickup signals for operations of the Duke storage ring with a wide range of single-bunch current

    Science.gov (United States)

    Xu, Wei; Li, Jing-Yi; Huang, Sen-Lin; Z. Wu, W.; Hao, H.; P., Wang; K. Wu, Y.

    2014-10-01

    The Duke storage ring is a dedicated driver for the storage ring based oscillator free-electron lasers (FELs), and the High Intensity Gamma-ray Source (HIGS). It is operated with a beam current ranging from about 1 mA to 100 mA per bunch for various operations and accelerator physics studies. High performance operations of the FEL and γ-ray source require a stable electron beam orbit, which has been realized by the global orbit feedback system. As a critical part of the orbit feedback system, the electron beam position monitors (BPMs) are required to be able to precisely measure the electron beam orbit in a wide range of the single-bunch current. However, the high peak voltage of the BPM pickups associated with high single-bunch current degrades the performance of the BPM electronics, and can potentially damage the BPM electronics. A signal conditioning method using low pass filters is developed to reduce the peak voltage to protect the BPM electronics, and to make the BPMs capable of working with a wide range of single-bunch current. Simulations and electron beam based tests are performed. The results show that the Duke storage ring BPM system is capable of providing precise orbit measurements to ensure highly stable FEL and HIGS operations.

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

    International Nuclear Information System (INIS)

    2001-01-01

    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 (ζ = ΔQ/(Δp/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)

  8. Commissioning of an electro-optic electron bunch length monitor at FLASH

    International Nuclear Information System (INIS)

    Breunlin, Jonas

    2011-03-01

    The demands on the electron beam qualities for free-electron lasers (FEL) are challenging in terms of high peak currents. At FLASH, the high-gain FEL in Hamburg, longitudinal bunch compression is performed to achieve the requested high charge densities in short bunches. The precise control of the bunch compression process requires advanced diagnostics on the longitudinal bunch profile. The bunch length monitor presented in this thesis is based on a non-destructive detection using the electro-optic effect. The focus is on a compact and reliable system for permanent bunch diagnostics. The monitor provides single-shot measurements of the longitudinal bunch profiles with lengths of a few picoseconds by spectrally encoding their charge distribution. First measurements for characterization purpose have been performed. It has been shown that the monitor is suitable for monitoring the longitudinal bunch profile behind the first bunch compressor at FLASH. Electron bunch profiles with slopes corresponding to a full width half maximum of about 1.4 ps have been detected. That is the intrinsic resolution limit of the utilized method. (orig.)

  9. 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

  10. WAVEGUIDE COUPLER KICK TO BEAM BUNCH AND CURRENT DEPENDENCY ON SRF CAVITIES

    International Nuclear Information System (INIS)

    Genfa Wu; Haipeng Wang; Charles Reece; Robert Rimmer

    2008-01-01

    JLAB SRF cavities employ waveguide type fundamental power couplers (FPC). The FPC design for the 7-cell upgrade cavities was optimized to minimize the dipole field kick. For continuous wave (CW) operation, the forwarding RF power will be at different magnitude to drive the different beam current and cavity gradient. This introduces some deviation from optimized FPC field for varying beam loading. This article analyzes the beam behavior both in centroid kick and head-tail kick under different beam loading conditions

  11. 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.

  12. Femtosecond electron bunches, source and characterization

    International Nuclear Information System (INIS)

    Thongbai, C.; Kusoljariyakul, K.; Rimjaem, S.; Rhodes, M.W.; Saisut, J.; Thamboon, P.; Wichaisirimongkol, P.; Vilaithong, T.

    2008-01-01

    A femtosecond electron source has been developed at the Fast Neutron Research Facility (FNRF), Chiang Mai University, Thailand. So far, it has produced electron bunches as short as σ z ∼180 fs with (1-6)x10 8 electrons per microbunch. The system consists of an RF-gun with a thermionic cathode, an alpha-magnet as a magnetic bunch compressor, and a linear accelerator as a post acceleration section. Coherent transition radiation emitted at wavelengths equal to and longer than the bunch length is used in a Michelson interferometer to determine the bunch length by autocorrelation technique. The experimental setup and results of the bunch length measurement are described

  13. MEASURING TEMPORAL PHOTON BUNCHING IN BLACKBODY RADIATION

    Energy Technology Data Exchange (ETDEWEB)

    Tan, P. K.; Poh, H. S.; Kurtsiefer, C. [Center for Quantum Technologies, 3 Science Drive 2, 117543 (Singapore); Yeo, G. H.; Chan, A. H., E-mail: pengkian@physics.org, E-mail: phyck@nus.edu.sg [Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 (Singapore)

    2014-07-01

    Light from thermal blackbody radiators such as stars exhibits photon bunching behavior at sufficiently short timescales. However, with available detector bandwidths, this bunching signal is difficult to observe directly. We present an experimental technique to increase the photon bunching signal in blackbody radiation via spectral filtering of the light source. Our measurements reveal strong temporal photon bunching from blackbody radiation, including the Sun. This technique allows for an absolute measurement of the photon bunching signature g {sup (2)}(0), and thereby a direct statement on the statistical nature of a light source. Such filtering techniques may help revive the interest in intensity interferometry as a tool in astronomy.

  14. 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.

  15. Bunch lengthening in the SLC [Stanford Linear Collider] damping rings

    International Nuclear Information System (INIS)

    Bane, K.L.F.

    1990-02-01

    A high level of current dependent bunch lengthening has been observed on the North damping ring of the Stanford Linear Collider (SLC). At currents of 3 x 10 10 this behavior does not appear to degrade the machine's performance significantly. However, at the higher currents that are envisioned for the future one fears that its performance could be greatly degraded due to the phenomenon of bunch lengthening. This was the motivation for the work described in this paper. In this paper we calculate the longitudinal impedance of the damping ring vacuum chamber. More specifically, in this paper we find the response function of the ring to a short Gaussian bunch, which we call the Green function wake. In addition, we try to estimate the relative importance of the different vacuum chamber objects, in order to see how we might reduce the ring impedance. This paper also describes bunch length measurements performed on the North damping ring. We use the Green function wake, discussed above, to compute the bunch lengthening. Then we compare these results with those obtained from the measurements. In addition, we calculate the current dependence of the tune distribution

  16. 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

  17. Longitudinal single-bunch instabilities

    International Nuclear Information System (INIS)

    Migliorati, M.; Palumbo, L.; Rome Univ. La Sapienza, Rome

    2001-02-01

    After introducing the concepts of longitudinal wakefield and coupling impedance, it is reviewed the theory of longitudinal single-bunch collective effects in storage rings. From the Fokker-Planck equation it is first derived the stationary solution describing the natural single-bunch regime, and then treat the problem of microwave instability, showing the different approaches used for estimating the threshold current. The lecture is ended with the semi-empirical laws that allow everyone to obtain the single-bunch behaviour above threshold, and with a description of the simulation codes that are now reliable tools for investigating all these effects

  18. Overview of bunch length measurements

    International Nuclear Information System (INIS)

    Lumpkin, A. H.

    1999-01-01

    An overview of particle and photon beam bunch length measurements is presented in the context of free-electron laser (FEL) challenges. Particle-beam peak current is a critical factor in obtaining adequate FEL gain for both oscillators and self-amplified spontaneous emission (SASE) devices. Since measurement of charge is a standard measurement, the bunch length becomes the key issue for ultrashort bunches. Both time-domain and frequency-domain techniques are presented in the context of using electromagnetic radiation over eight orders of magnitude in wavelength. In addition, the measurement of microbunching in a micropulse is addressed

  19. Thyristor based short circuit current injection in isolated grids

    OpenAIRE

    Hoff, Bjarte; Sharma, Pawan; Østrem, Trond

    2017-01-01

    This paper proposes a thyristor based short circuit current injector for providing short circuit current in isolated and weak grids, where sufficient fault current to trigger circuit breakers may not be available. This will allow the use of conventional miniature circuit breakers, which requires high fault current for instantaneous tripping. The method has been validated through experiments.

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

    International Nuclear Information System (INIS)

    Teytelman, D.; Fox, J.; Hindi, H.; Limborg, C.; Linscott, I.; Prabhakar, S.; Sebek, J.; Young, A.; Drago, A.; Serio, M.; Barry, W.; Stover, G.

    1998-01-01

    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 DAΦNE. 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

  1. Bunch compression at the Stanford Linear Collider

    International Nuclear Information System (INIS)

    Holtzapple, R.L.; Decker, F.J.; Simopoulos, C.

    1995-08-01

    The production and measurement of short electron and positron bunches in the Stanford Linear Collider (SLC) will be presented in this paper. The bunches are compressed in a transport line between the damping rings and the linac. The electron and positron bunch distributions in the SLC linac have been measured using a Hamamatsu, model N3373-02, 500-femtosecond streak camera. The distributions were measured at the end of the SLC linac versus the bunch compressor RF voltage. The measurements are compared with simulations

  2. Theoretical estimation and experimental design of high-intensity far-infrared to MM-wave coherent synchrotron radiation generated by short electron bunches at BFEL

    International Nuclear Information System (INIS)

    Zhu Junbiao; Li Yonggui; Xie Jialin

    2000-01-01

    Broadband continuous and high-intensity coherent synchrotron radiation (CSR) emitted from 4 ps electron bunches provided by the 30 MeV RF linac of Beijing FEL is analyzed and numerically calculated using an exact series expansion for the infinite integral of fractional modified Bessel function. CSR in the mm-wave and far-IR to mm-wave regions can be respectively generated by directly using these bunches and by applying those ones compressed to ≤=1 ps. The CSR powers, approximately as 10 8 -10 9 times as the SR ones, in the range from several hundred microwatts to milliwatts are dependent on chosen electron density distribution, wavelength range, and gathering angle. The power produced by rectangular bunches is greater than that generated by Gaussian ones. The shorter the bunch, the stronger the produced CSR, the greater the energy concentrated to the far-IR end. Experiments to generate CSR and measure the bunch length are designed

  3. Bunch Length Measurements in SPEAR3

    Energy Technology Data Exchange (ETDEWEB)

    Corbett, W.J.; Fisher, A.; Huang, X.; Safranek, J.; Sebek, J.; /SLAC; Lumpkin, A.; /Argonne; Sannibale, F.; /LBL, Berkeley; Mok, W.; /Unlisted

    2007-11-28

    A series of bunch length measurements were made in SPEAR3 for two different machine optics. In the achromatic optics the bunch length increases from the low-current value of 16.6ps rms to about 30ps at 25ma/bunch yielding an inductive impedance of -0.17{Omega}. Reducing the momentum compaction factor by a factor of {approx}60 [1] yields a low-current bunch length of {approx}4ps rms. In this paper we review the experimental setup and results.

  4. Photon anti bunching versus phantom anti bunching?

    International Nuclear Information System (INIS)

    Miranowicz, A.; Ekert, A.; Ekert, A.; Bajer, J.; Leonski, W.

    1997-01-01

    Photon anti bunching defined by two-time correlation functions has hitherto, to our best knowledge, been considered to constitute a unique, well defined effect. We show explicitly that this is by no means the case. We analyze two of the most famous definitions showing that both anti bunching and bunching effects according to one definition can be accompanied by arbitrary photon correlation effects according to another. As an example we discuss a model of parametric frequency conversion. (authors)

  5. Multiple-bunch-length operating mode design for a storage ring using hybrid low alpha and harmonic cavity method

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Weiwei, E-mail: gaomqr@mail.ustc.edu.cn [College of Mathematics and Physics, Fujian University of Technology, Fuzhou 350118 (China); Wang, Lin; Li, Heting [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China)

    2017-03-11

    In this paper we design a simultaneous three bunch length operating mode at the HLS-II (Hefei Light Source II) storage ring by installing two harmonic cavities and minimizing the momentum compaction factor. The short bunches (2.6 mm) presented in this work will meet the requirement of coherent millimeter-wave and sub-THz radiation experiments, while the long bunches (20 mm) will efficiently increase the total beam current. Therefore, this multiple-bunch-length operating mode allows present synchrotron users and coherent millimeter-wave users (or sub THz users) to carry out their experiments simultaneously. Since the relatively low energy characteristic of HLS-II we achieve the multiple-bunch-length operating mode without multicell superconducting RF cavities, which is technically feasible.

  6. Single-bunch kicker pulser

    International Nuclear Information System (INIS)

    Frey, W.W.

    1983-01-01

    The single-bunch kicker magnet is powered by a capacitor discharge pulser. The ferrite-core magnet is used to kick out one of twelve proton bunches circulating in the AGS (Alternating Gradient Synchrotron) into the experimental area. The magnet current pulse has a half-sinusoid shape, with a peak current of 2800 A. The pulse current rises and falls to zero, with minimum undershoot, in 410 nsec to minimize effects on adjacent bunches. The magnet inductance is 1.0 μHy. The pulser is mounted on the kicker magnet in the AGS ring, and is exposed to ionizing radiation. The HVDC power supply, controls, monitoring, and auxiliary circuits are housed approximately 300 feet away external to the ring. A two-gap thyratron is used to discharge the energy storage capacitor. Two hydrogen diodes are series connected to function as an inverse diode

  7. Single-bunch kicker pulser

    Energy Technology Data Exchange (ETDEWEB)

    Frey, W.W.

    1983-01-01

    The single-bunch kicker magnet is powered by a capacitor discharge pulser. The ferrite-core magnet is used to kick out one of twelve proton bunches circulating in the AGS (Alternating Gradient Synchrotron) into the experimental area. The magnet current pulse has a half-sinusoid shape, with a peak current of 2800 A. The pulse current rises and falls to zero, with minimum undershoot, in 410 nsec to minimize effects on adjacent bunches. The magnet inductance is 1.0 ..mu..Hy. The pulser is mounted on the kicker magnet in the AGS ring, and is exposed to ionizing radiation. The HVDC power supply, controls, monitoring, and auxiliary circuits are housed approximately 300 feet away external to the ring. A two-gap thyratron is used to discharge the energy storage capacitor. Two hydrogen diodes are series connected to function as an inverse diode.

  8. 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.

  9. Application accelerator system having bunch control

    International Nuclear Information System (INIS)

    Wang, D.; Krafft, G.A.

    1999-01-01

    An application accelerator system for monitoring the gain of a free electron laser is disclosed. Coherent Synchrotron Radiation (CSR) detection techniques are used with a bunch length monitor for ultra short, picosec to several tens of femtosec, electron bunches. The monitor employs an application accelerator, a coherent radiation production device, an optical or beam chopping device, an infrared radiation collection device, a narrow-banding filter, an infrared detection device, and a control. 1 fig

  10. Application accelerator system having bunch control

    Science.gov (United States)

    Wang, Dunxiong; Krafft, Geoffrey Arthur

    1999-01-01

    An application accelerator system for monitoring the gain of a free electron laser. Coherent Synchrotron Radiation (CSR) detection techniques are used with a bunch length monitor for ultra short, picosec to several tens of femtosec, electron bunches. The monitor employs an application accelerator, a coherent radiation production device, an optical or beam chopping device, an infrared radiation collection device, a narrow-banding filter, an infrared detection device, and a control.

  11. Study of CSR longitudinal bunch compression cavity

    International Nuclear Information System (INIS)

    Yin Dayu; Li Peng; Liu Yong; Xie Qingchun

    2009-01-01

    The scheme of longitudinal bunch compression cavity for the Cooling Storage Ring (CSR)is an important issue. Plasma physics experiments require high density heavy ion beam and short pulsed bunch,which can be produced by non-adiabatic compression of bunch implemented by a fast compression with 90 degree rotation in the longitudinal phase space. The phase space rotation in fast compression is initiated by a fast jump of the RF-voltage amplitude. For this purpose, the CSR longitudinal bunch compression cavity, loaded with FINEMET-FT-1M is studied and simulated with MAFIA code. In this paper, the CSR longitudinal bunch compression cavity is simulated and the initial bunch length of 238 U 72+ with 250 MeV/u will be compressed from 200 ns to 50 ns.The construction and RF properties of the CSR longitudinal bunch compression cavity are simulated and calculated also with MAFIA code. The operation frequency of the cavity is 1.15 MHz with peak voltage of 80 kV, and the cavity can be used to compress heavy ions in the CSR. (authors)

  12. 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.

  13. Emittance growth of bunched beams in bends

    International Nuclear Information System (INIS)

    Carlsten, B.E.; Raubenheimer, T.O.

    1995-01-01

    Talman [Phys. Rev. Lett. 56, 1429 (1986)] has proposed a novel relativistic effect that occurs when a charged particle beam is bent in the magnetic field from an external dipole. The consequence of this effect is that the space-charge forces from the particles do not exhibit the usual inverse-square energy dependence and some part of them are, in fact, independent of energy. This led to speculation that this effect could introduce significant emittance growth for a bending electron beam. Subsequently, it was shown that this effect's influence on the beam's transverse motion is canceled for a dc beam by a potential depression within the beam (to first order in the beam radius divided by the bend radius). In this paper, we extend the analysis to include short bunch lengths (as compared to the beam pipe dimensions) and find that there is no longer the cancellation for forces both transverse to and in the direction of motion. We provide an estimate for the emittance growth as a function of bend angle, beam radius, and current, and for magnetic compression of an electron bunch

  14. Electrical short circuit and current overload tests on aircraft wiring

    Science.gov (United States)

    Cahill, Patricia

    1995-01-01

    The findings of electrical short circuit and current overload tests performed on commercial aircraft wiring are presented. A series of bench-scale tests were conducted to evaluate circuit breaker response to overcurrent and to determine if the wire showed any visible signs of thermal degradation due to overcurrent. Three types of wire used in commercial aircraft were evaluated: MIL-W-22759/34 (150 C rated), MIL-W-81381/12 (200 C rated), and BMS 1360 (260 C rated). A second series of tests evaluated circuit breaker response to short circuits and ticking faults. These tests were also meant to determine if the three test wires behaved differently under these conditions and if a short circuit or ticking fault could start a fire. It is concluded that circuit breakers provided reliable overcurrent protection. Circuit breakers may not protect wire from ticking faults but can protect wire from direct shorts. These tests indicated that the appearance of a wire subjected to a current that totally degrades the insulation looks identical to a wire subjected to a fire; however the 'fire exposed' conductor was more brittle than the conductor degraded by overcurrent. Preliminary testing indicates that direct short circuits are not likely to start a fire. Preliminary testing indicated that direct short circuits do not erode insulation and conductor to the extent that ticking faults did. Circuit breakers may not safeguard against the ignition of flammable materials by ticking faults. The flammability of materials near ticking faults is far more important than the rating of the wire insulation material.

  15. Bunch lengthening and related effects in SPEAR II

    International Nuclear Information System (INIS)

    Wilson, P.B.; Servranckx, R.; Sabersky, A.P.; Gareyte, J.; Fischer, G.E.; Chao, A.W.; Donald, M.H.R.

    1977-03-01

    In recent years, electron storage ring designers have become aware of the problems caused by the interaction of short, high current bunches with their environment. Important effects are: (1) energy loss can cause local overheating of chamber components; (2) additional rf power is required due to overall energy loss; (3) the increased energy spread requires increased aperture; (4) destructive instabilities could occur. Anomalous bunch lengthening and energy spread, the spectroscopy of longitudinal modes and the shift of synchronous phase were simultaneously measured in order to study the dynamics of the interaction. From the data obtained at SPEAR II one is led to a model of coupling impedance which should be useful in the design of any electron ring

  16. CORNELL: Bunch trains provide higher luminosity

    International Nuclear Information System (INIS)

    Anon.

    1995-01-01

    The new colliding beam technique - ''bunch trains'' - at Cornell's electron-positron Storage Ring (CESR) has led to a new world record for colliding beam luminosity - 3.3 x 10 32 cm -2 s -1 . In the bid to increase reaction rate for any particular process, this luminosity is pushed as high as possible. Once all other luminosityincreasing cards have been played, the only practical way of making a large gain in luminosity is to increase the frequency of bunch-bunch collisions by increasing the number of bunches stored in the ring. However this is not without its own problems: • If the two beams travel the same orbit, the n bunches in one beam collide with the n bunches of the other at 2n points around the ring, and the resulting cumulative nonlinear beam-beam effect (tune shift) severely limits the luminosity attainable at any interaction point. • The destabilizing wakefield effects of bunches on each other increase as the number of bunches increases and the spacing between them decreases. • The synchrotron radiation emitted by the beams becomes a severe problem as the total beam current is raised: to overcome these effects means supplying radiofrequency power to maintain the beam energy, carrying away heat from the vacuum chamber walls, pumping out desorbed gases, and controlling Xray backgrounds in the experiment. In 1979, CESR was designed to run with a single bunch of electrons and a single bunch of positrons circulating on the same orbit and colliding head-on at two diametrically opposite points in the ring, where the CLEO and CUSB experiments were then located. Ideally one could store multiple bunches and solve the multiple collision point problem by using separate rings for the two beams, as in the CERN ISR proton-proton collider and in the original DORIS two-ring configuration at DESY, Hamburg, making the two beams intersect only at the experiments. A less expensive version of this two-ring scheme was accomplished at CESR in

  17. CORNELL: Bunch trains provide higher luminosity

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1995-09-15

    The new colliding beam technique - ''bunch trains'' - at Cornell's electron-positron Storage Ring (CESR) has led to a new world record for colliding beam luminosity - 3.3 x 10{sup 32} cm{sup -2}s{sup -1}. In the bid to increase reaction rate for any particular process, this luminosity is pushed as high as possible. Once all other luminosityincreasing cards have been played, the only practical way of making a large gain in luminosity is to increase the frequency of bunch-bunch collisions by increasing the number of bunches stored in the ring. However this is not without its own problems: • If the two beams travel the same orbit, the n bunches in one beam collide with the n bunches of the other at 2n points around the ring, and the resulting cumulative nonlinear beam-beam effect (tune shift) severely limits the luminosity attainable at any interaction point. • The destabilizing wakefield effects of bunches on each other increase as the number of bunches increases and the spacing between them decreases. • The synchrotron radiation emitted by the beams becomes a severe problem as the total beam current is raised: to overcome these effects means supplying radiofrequency power to maintain the beam energy, carrying away heat from the vacuum chamber walls, pumping out desorbed gases, and controlling Xray backgrounds in the experiment. In 1979, CESR was designed to run with a single bunch of electrons and a single bunch of positrons circulating on the same orbit and colliding head-on at two diametrically opposite points in the ring, where the CLEO and CUSB experiments were then located. Ideally one could store multiple bunches and solve the multiple collision point problem by using separate rings for the two beams, as in the CERN ISR proton-proton collider and in the original DORIS two-ring configuration at DESY, Hamburg, making the two beams intersect only at the experiments. A less expensive version of this two-ring scheme was accomplished at CESR in 1983, using

  18. Beam bunch feedback

    International Nuclear Information System (INIS)

    Lambertson, G.

    1995-09-01

    When the electromagnetic fields that are excited by the passage of a bundle of charged particles persist to act upon bunches that follow, then the motions of the bunches are coupled. This action between bunches circulating on a closed orbit can generate growing patterns of bunch excursions. Such growth can often be suppressed by feedback systems that detect the excursion and apply corrective forces to the bunches. To be addressed herein is feedback that acts on motions of the bunch body centers. In addition to being useful for suppressing the spontaneous growth of coupled-bunch motions, such feedback can be used to damp transients in bunches injected into an accelerator or storage ring; for hadrons which lack strong radiation damping, feedback is needed to avoid emittance growth through decoherence. Motions excited by noise in magnetic fields or accelerating rf can also be reduced by using this feedback. Whether the action is on motions that are transverse to the closed orbit or longitudinal, the arrangement is the same. Bunch position is detected by a pickup and that signal is processed and directed to a kicker that may act upon the same bunch or some other portion of the collective beam pattern. Transverse motion is an oscillation with angular frequency ν perpendicular ω o where ω o is the orbital frequency 2π line-integral o. Longitudinal synchrotron oscillation occurs at frequency ω s = ν s ω o . The former is much more rapid, ν perpendicular being on the order of 10 while ν s is typically about 10 minus 1 to 10 minus 2

  19. Luminosity with more bunches in PEP

    International Nuclear Information System (INIS)

    Corbett, W.J.

    1990-12-01

    The near term accelerator physics program for PEP includes experiments in a collider mode with up to 9 bunches in each beam. In this memo, luminosity data from the 3 x 3 configuration is first used to calculate vertical beam size, emittance and tune shift as a function of current. The data is then used to extrapolate to the case with either 6 x 6 or 9 x 9 bunches colliding in PEP. Vertical emittance growth from the separated bunch optics and dispersion at the IP are included in the calculations. The conclusion is that given a 90 mA current drive limitation in PEP, operating with 6 x 6 bunches yields the maximum luminosity. 9 refs., 6 figs

  20. A Short-Current Control Method for Constant Frequency Current-Fed Wireless Power Transfer Systems

    Directory of Open Access Journals (Sweden)

    Yanling Li

    2017-04-01

    Full Text Available Frequency drift is a serious problem in Current-Fed Wireless Power Transfer (WPT systems. When the operating frequency is drifting from the inherent Zero Voltage Switching (ZVS frequency of resonant network, large short currents will appear and damage the switches. In this paper, an inductance-dampening method is proposed to inhibit short currents and achieve constant-frequency operation. By adding a small auxiliary series inductance in the primary resonant network, short currents are greatly attenuated to a safe level. The operation principle and steady-state analysis of the system are provided. An overlapping time self-regulating circuit is designed to guarantee ZVS running. The range of auxiliary inductances is discussed and its critical value is calculated exactly. The design methodology is described and a design example is presented. Finally, a prototype is built and the experimental results verify the proposed method.

  1. Computer modelling of bunch-by-bunch feedback for the SLAC B-factory design

    International Nuclear Information System (INIS)

    Briggs, D.; Fox, J.D.; Hosseini, W.; Klaisner, L.; Morton, P.; Pellegrin, J.L.; Thompson, K.A.; Lambertson, G.

    1991-05-01

    The SLAC B-factory design, with over 1600 high current bunches circulating in each ring, will require a feedback system to avoid coupled-bunch instabilities. A computer model of the storage ring, including the RF system, wave fields, synchrotron radiation loss, and the bunch-by-bunch feedback system is presented. The feedback system model represents the performance of a fast phase detector front end (including system noise and imperfections), a digital filter used to generate a correction voltage, and a power amplifier and beam kicker system. The combined ring-feedback system model is used to study the feedback system performance required to suppress instabilities and to quantify the dynamics of the system. Results are presented which show the time development of coupled bunch instabilities and the damping action of the feedback system. 3 refs., 5 figs., 2 tabs

  2. Bunch identification module

    International Nuclear Information System (INIS)

    Fox, J.D.

    1981-01-01

    This module provides bunch identification and timing signals for the PEP Interaction areas. Timing information is referenced to the PEP master oscillator, and adjusted in phase as a function of region. Identification signals are generated in a manner that allows observers in all interaction regions to agree on an unambiguous bunch identity. The module provides bunch identification signals via NIM level logic, upon CAMAC command, and through LED indicators. A front panel ''region select'' switch allows the same module to be used in all regions. The module has two modes of operation: a bunch identification mode and a calibration mode. In the identification mode, signals indicate which of the three bunches of electrons and positrons are interacting, and timing information about beam crossing is provided. The calibration mode is provided to assist experimenters making time of flight measurements. In the calibration mode, three distinct gating signals are referenced to a selected bunch, allowing three timing systems to be calibrated against a common standard. Physically, the bunch identifier is constructed as a single width CAMAC module. 2 figs., 1 tab

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

    International Nuclear Information System (INIS)

    Teytelman, D.; Fox, J.; Hindi, H.; Limborg, C.; Linscott, I.; Prabhakar, S.; Sebek, J.; Young, A.; Drago, A.; Serio, M.; Barry, W.; Stover, G.

    1998-01-01

    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 DAΦNE. 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 1998 American Institute of Physics

  4. To the mechanism of modulated REB current increase during its propagation through plasma

    International Nuclear Information System (INIS)

    Kiselev, V.A.; Linnik, A.F.; Maslov, V.I.; Uskov, V.V.

    2002-01-01

    The mechanism of full current increase is investigated in this paper. This current arises at transporting of the short relativistic electron bunches in the plasma,formed by them at gas of large pressure. This phenomenon is determined by the electric field, arising at motion of the relativistic electron bunches, having an angular divergence, in the plasma

  5. Temporal dynamics of the longitudinal bunch profile in a laser wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Heigoldt, Matthias

    2017-05-19

    This thesis deals with the temporal characterisation of electron bunches produced by a laser plasma accelerator. In the so-called laser wakefield acceleration (LWFA) scheme, an ultra-short high-intensity laser pulse excites a plasma wave, which can sustain accelerating electric fields of several hundred GV/m, thus exceeding the fields attainable by current state-of-the-art radio frequency (RF) accelerators by four orders of magnitude, offering the prospect of downsizing both the size and cost of such machines. Furthermore, by intrinsically confining the accelerated electron beam to the μm-scale size of the plasma wave, LWFAs provide ultra-short and highly brilliant beams, sparking great scientific interest for their application as a driver for compact sources of ultra-short X-ray pulses, e.g. Thomson-scattering, betatron sources or table-top free-electron lasers (FELs). The bunch profile is an important quantity for the application of these sources. With particular regard to the envisioned table-top FELs, it also determines the available peak current, an import input parameter for an appropriate undulator design that is optimized to support the self-amplified spontaneous emission (SASE) process. The experiments presented in this thesis comprise the measurement of the temporal profile of electron bunches produced by LWFA and further investigation of the evolution of the temporal profile in dependence of the acceleration distance and the plasma density. By measuring the intensity spectrum of coherent transition radiation (CTR) emitted by LWFA-driven electron bunches in the frequency domain, the experiments allow a reconstruction of the longitudinal bunch profiles with unprecedented resolution. Compared to earlier work, a key improvement is the single-shot coverage of a broadband spectral range of more than four octaves, which yields a time resolution of the reconstructed bunch profile in the sub-femtosecond region. This work further inspired the development of a new

  6. Temporal dynamics of the longitudinal bunch profile in a laser wakefield accelerator

    International Nuclear Information System (INIS)

    Heigoldt, Matthias

    2017-01-01

    This thesis deals with the temporal characterisation of electron bunches produced by a laser plasma accelerator. In the so-called laser wakefield acceleration (LWFA) scheme, an ultra-short high-intensity laser pulse excites a plasma wave, which can sustain accelerating electric fields of several hundred GV/m, thus exceeding the fields attainable by current state-of-the-art radio frequency (RF) accelerators by four orders of magnitude, offering the prospect of downsizing both the size and cost of such machines. Furthermore, by intrinsically confining the accelerated electron beam to the μm-scale size of the plasma wave, LWFAs provide ultra-short and highly brilliant beams, sparking great scientific interest for their application as a driver for compact sources of ultra-short X-ray pulses, e.g. Thomson-scattering, betatron sources or table-top free-electron lasers (FELs). The bunch profile is an important quantity for the application of these sources. With particular regard to the envisioned table-top FELs, it also determines the available peak current, an import input parameter for an appropriate undulator design that is optimized to support the self-amplified spontaneous emission (SASE) process. The experiments presented in this thesis comprise the measurement of the temporal profile of electron bunches produced by LWFA and further investigation of the evolution of the temporal profile in dependence of the acceleration distance and the plasma density. By measuring the intensity spectrum of coherent transition radiation (CTR) emitted by LWFA-driven electron bunches in the frequency domain, the experiments allow a reconstruction of the longitudinal bunch profiles with unprecedented resolution. Compared to earlier work, a key improvement is the single-shot coverage of a broadband spectral range of more than four octaves, which yields a time resolution of the reconstructed bunch profile in the sub-femtosecond region. This work further inspired the development of a new

  7. On measuring charged particle bunch duration in linear accelerators

    International Nuclear Information System (INIS)

    Lomize, L.G.; Malykh, N.I.; Khizhnyj, V.I.; Yampol'skij, E.S.

    1977-01-01

    The process of measuring short bunches is simulated by means of cavity resonators in which HF fields are excited by both positive and negative ion bunches flying through them. The simulation is aimed to assess optimum operation of a linear accelerator. A set of bunches of chance form and duration is simulated. Then the simulation of the process of restoring the duration and shape of a bunch according to data obtained from a limited number of resonators is realized. The use of 3-4 resonators tuned to 3, 6, 9 and 12-th harmonics of bunch repetition rate is shown to be sufficient for determining bunch duration with an accuracy of several per cent. When data on harmonic phases is available, one can obtain information on beam asymmetry

  8. Quantum beamstrahlung from gaussian bunches

    International Nuclear Information System (INIS)

    Chen, P.

    1987-08-01

    The method of Baier and Katkov is applied to calculate the correction terms to the Sokolov-Ternov radiation formula due to the variation of the magnetic field strength along the trajectory of a radiating particle. We carry the calculation up to the second order in the power expansion of B tau/B, where tau is the formation time of radiation. The expression is then used to estimate the quantum beamstrahlung average energy loss from e + e - bunches with gaussian distribution in bunch currents. We show that the effect of the field variation is to reduce the average energy loss from previous calculations based on the Sokolov-Ternov formula or its equivalent. Due to the limitation of our method, only an upper bound of the reduction is obtained. 18 refs

  9. 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)

  10. Short wavelength limits of current shot noise suppression

    International Nuclear Information System (INIS)

    Nause, Ariel; Dyunin, Egor; Gover, Avraham

    2014-01-01

    Shot noise in electron beam was assumed to be one of the features beyond control of accelerator physics. Current results attained in experiments at Accelerator Test Facility in Brookhaven and Linac Coherent Light Source in Stanford suggest that the control of the shot noise in electron beam (and therefore of spontaneous radiation and Self Amplified Spontaneous Emission of Free Electron Lasers) is feasible at least in the visible range of the spectrum. Here, we present a general linear formulation for collective micro-dynamics of e-beam noise and its control. Specifically, we compare two schemes for current noise suppression: a quarter plasma wavelength drift section and a combined drift/dispersive (transverse magnetic field) section. We examine and compare their limits of applicability at short wavelengths via considerations of electron phase-spread and the related Landau damping effect

  11. Short wavelength limits of current shot noise suppression

    Energy Technology Data Exchange (ETDEWEB)

    Nause, Ariel, E-mail: arielnau@post.tau.ac.il [Faculty of Exact Sciences, Department of Physics, Tel Aviv University, Tel Aviv (Israel); Dyunin, Egor; Gover, Avraham [Faculty of Engineering, Department of Physical Electronics, Tel Aviv University, Tel Aviv (Israel)

    2014-08-15

    Shot noise in electron beam was assumed to be one of the features beyond control of accelerator physics. Current results attained in experiments at Accelerator Test Facility in Brookhaven and Linac Coherent Light Source in Stanford suggest that the control of the shot noise in electron beam (and therefore of spontaneous radiation and Self Amplified Spontaneous Emission of Free Electron Lasers) is feasible at least in the visible range of the spectrum. Here, we present a general linear formulation for collective micro-dynamics of e-beam noise and its control. Specifically, we compare two schemes for current noise suppression: a quarter plasma wavelength drift section and a combined drift/dispersive (transverse magnetic field) section. We examine and compare their limits of applicability at short wavelengths via considerations of electron phase-spread and the related Landau damping effect.

  12. Short-run and Current Analysis Model in Statistics

    Directory of Open Access Journals (Sweden)

    Constantin Anghelache

    2006-01-01

    Full Text Available Using the short-run statistic indicators is a compulsory requirement implied in the current analysis. Therefore, there is a system of EUROSTAT indicators on short run which has been set up in this respect, being recommended for utilization by the member-countries. On the basis of these indicators, there are regular, usually monthly, analysis being achieved in respect of: the production dynamic determination; the evaluation of the short-run investment volume; the development of the turnover; the wage evolution: the employment; the price indexes and the consumer price index (inflation; the volume of exports and imports and the extent to which the imports are covered by the exports and the sold of trade balance. The EUROSTAT system of indicators of conjuncture is conceived as an open system, so that it can be, at any moment extended or restricted, allowing indicators to be amended or even removed, depending on the domestic users requirements as well as on the specific requirements of the harmonization and integration. For the short-run analysis, there is also the World Bank system of indicators of conjuncture, which is utilized, relying on the data sources offered by the World Bank, The World Institute for Resources or other international organizations statistics. The system comprises indicators of the social and economic development and focuses on the indicators for the following three fields: human resources, environment and economic performances. At the end of the paper, there is a case study on the situation of Romania, for which we used all these indicators.

  13. Short-run and Current Analysis Model in Statistics

    Directory of Open Access Journals (Sweden)

    Constantin Mitrut

    2006-03-01

    Full Text Available Using the short-run statistic indicators is a compulsory requirement implied in the current analysis. Therefore, there is a system of EUROSTAT indicators on short run which has been set up in this respect, being recommended for utilization by the member-countries. On the basis of these indicators, there are regular, usually monthly, analysis being achieved in respect of: the production dynamic determination; the evaluation of the short-run investment volume; the development of the turnover; the wage evolution: the employment; the price indexes and the consumer price index (inflation; the volume of exports and imports and the extent to which the imports are covered by the exports and the sold of trade balance. The EUROSTAT system of indicators of conjuncture is conceived as an open system, so that it can be, at any moment extended or restricted, allowing indicators to be amended or even removed, depending on the domestic users requirements as well as on the specific requirements of the harmonization and integration. For the short-run analysis, there is also the World Bank system of indicators of conjuncture, which is utilized, relying on the data sources offered by the World Bank, The World Institute for Resources or other international organizations statistics. The system comprises indicators of the social and economic development and focuses on the indicators for the following three fields: human resources, environment and economic performances. At the end of the paper, there is a case study on the situation of Romania, for which we used all these indicators.

  14. 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)

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

    International Nuclear Information System (INIS)

    Rogers, J.T.; Billing, M.G.; Dobbins, J.A.

    1996-01-01

    We have developed a time domain transverse feedback system with the high bandwidth needed to control transverse instabilities when the CESR e + e - 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)

  16. ''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)

  17. Operation and performance of bunch pre-compression for increased transmission at the SLC

    International Nuclear Information System (INIS)

    Minty, M.G.; Akre, R.; Decker, F.J.; Turner, J.

    1997-11-01

    As the beam currents at the SLC are increased, transverse aperture restrictions in the ring-to-linac transport line (RTL) become increasingly important. The RTL contains a bunch compressor which introduces a large energy variation across the bunch and hence a larger transverse beam size. Since 1994 the compressor amplitude has been operating at higher than design voltage. While advantageous for shaping the bunch distribution, this increased the bunch energy spread and therefore resulted in more beam loss. Moreover, due to current-dependent bunch lengthening in the damping ring, the higher the beam current, the more the current loss. To avoid such losses, the bunch length may be precompressed in the damping ring. Until recently, bunch precompression with high beam currents was not stable. In this paper the authors identify the reasons for the difficulties, describe the changes made to accommodate bunch precompression, and discuss performance aspects after implementation. The estimated increase in current at the interaction point is 15%

  18. Quantifying short-lived events in multistate ionic current measurements.

    Science.gov (United States)

    Balijepalli, Arvind; Ettedgui, Jessica; Cornio, Andrew T; Robertson, Joseph W F; Cheung, Kin P; Kasianowicz, John J; Vaz, Canute

    2014-02-25

    We developed a generalized technique to characterize polymer-nanopore interactions via single channel ionic current measurements. Physical interactions between analytes, such as DNA, proteins, or synthetic polymers, and a nanopore cause multiple discrete states in the current. We modeled the transitions of the current to individual states with an equivalent electrical circuit, which allowed us to describe the system response. This enabled the estimation of short-lived states that are presently not characterized by existing analysis techniques. Our approach considerably improves the range and resolution of single-molecule characterization with nanopores. For example, we characterized the residence times of synthetic polymers that are three times shorter than those estimated with existing algorithms. Because the molecule's residence time follows an exponential distribution, we recover nearly 20-fold more events per unit time that can be used for analysis. Furthermore, the measurement range was extended from 11 monomers to as few as 8. Finally, we applied this technique to recover a known sequence of single-stranded DNA from previously published ion channel recordings, identifying discrete current states with subpicoampere resolution.

  19. On the single bunch longitudinal collective effects in electron storage rings

    CERN Document Server

    Gao, J

    2002-01-01

    After giving an analytical expression for the single bunch short range wake potential of a storage ring, we have discussed separately the roles of linear and nonlinear terms of the Taylor expansion of the wake potential on the bunch longitudinal motion. The equations describing bunch lengthening and increase in energy spread are established. Applications to different operating machines are made.

  20. Optimized Bunch Compression System for the European XFEL

    CERN Document Server

    Limberg, Torsten; Brinkmann, Reinhard; Decking, Winfried; Dohlus, Martin; Flöettmann, Klaus; Kim, Yujong; Schneidmiller, Evgeny

    2005-01-01

    The European XFEL bunch compressor system has been optimized for greater flexibility in parameter space. Operation beyond the XFEL design parameters is discussed in two directions: achieving the uppermost number of photons in a single pulse on one hand and reaching the necessary peak current for lasing with a pulse as short as possible on the other. Results of start-to-end calculations including 3D-CSR effects, space charge forces and the impact on wake fields demonstrate the potential of the XFEL for further improvement or, respectively, its safety margin for operation at design values.

  1. Evolution of dense spatially modulated electron bunches

    Science.gov (United States)

    Balal, N.; Bratman, V. L.; Friedman, A.

    2018-03-01

    An analytical theory describing the dynamics of relativistic moving 1D electron pulses (layers) with the density modulation affected by a space charge has been revised and generalized for its application to the formation of dense picosecond bunches from linear accelerators with laser-driven photo injectors, and its good agreement with General Particle Tracer simulations has been demonstrated. Evolution of quasi-one-dimensional bunches (disks), for which the derived formulas predict longitudinal expansion, is compared with that for thin and long electron cylinders (threads), for which the excitation of non-linear waves with density spikes was found earlier by Musumeci et al. [Phys. Rev. Lett. 106(18), 184801 (2011)] and Musumeci et al. [Phys. Rev. Spec. Top. -Accel. Beams 16(10), 100701 (2013)]. Both types of bunches can be used for efficiency enhancement of THz sources based on the Doppler frequency up-shifted coherent spontaneous radiation of electrons. Despite the strong Coulomb repulsion, the periodicity of a preliminary modulation in dense 1D layers persists during their expansion in the most interesting case of a relatively small change in particle energy. However, the period of modulation increases and its amplitude decreases in time. In the case of a large change in electron energy, the uniformity of periodicity is broken due to different relativistic changes in longitudinal scales along the bunch: the "period" of modulation decreases and its amplitude increases from the rear to the front boundary. Nevertheless, the use of relatively long electron bunches with a proper preliminary spatial modulation of density can provide a significantly higher power and a narrower spectrum of coherent spontaneous radiation of dense bunches than in the case of initially short single bunches with the same charge.

  2. Preliminary Study on Two Possible Bunch Compression Schemes at NLCTA

    International Nuclear Information System (INIS)

    Sun, Yipeng

    2011-01-01

    In this paper, two possible bunch compression configurations are proposed and evaluated by numerical simulation in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. A bunch compression ratio up to 20 could be achieved under a perfect condition, without consideration for the timing jitter and other error sources. The NLCTA is a test accelerator built at SLAC, which is approximately 42 meters long and composed of X-band acceleration structures. The main aim of building NLCTA is to develop and demonstrate the X-band rf acceleration technologies for the next generation linear collider, with a relatively high acceleration gradient between 50 MV/m and 100 MV/m. The current operation configuration of NLCTA features a thermionic-cathode electron gun at its starting point which generates an electron beam with an energy of 5 MeV. This is followed by a roughly 1.5 meter long X-band acceleration structure which boosts the electron beam energy to 60 MeV. Then there is a four-dipole magnetic chicane which is 6 meters long and provides a first order longitudinal dispersion of R 56 = -73mm. Next the electron beam passes by several matching quadrupoles and can be accelerated further to 120 MeV through another one-meter-long X-band acceleration structure. After that, there are three small chicanes downstream, with a total first order longitudinal dispersion of R 56 = -10mm. A sketch of the main components of NLCTA is shown in Figure 1, where the total length of this accelerator is 45 meters. Free Electron Lasers (FELs), proposed by J. Madey and demonstrated for the first time at Stanford University in 1970s (2) (3), use the lasing of relativistic electron beam traveling through a magnetic undulator, which can reach high power and can be widely tunable in wavelength. Linac based FEL source can provide sufficient brightness, and a short X-ray wavelength down to angstrom scale, which promises in supporting wide range of research experiments. In order to have an electron beam

  3. 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...

  4. The free recovery of a short duration, high current discharge

    International Nuclear Information System (INIS)

    Piejak, R.

    1984-01-01

    The hold-off voltage between stainless steel electrodes has been measured as a function of time after an initial discharge. The hold-off voltage is the highest voltage that the gap will withstand without appreciable current flow. A high current (600-1200 amp), short duration (170 nsec) discharge was initiated between Rogowski profile electrodes. After a pre-determined time delay, a second pulse was applied to the discharge gap. The hold-off voltage as a function to time was determined up to the Paschen breakdown voltage. Background gas pressure between 30 and 100 torr and electrode separation of 2mm and 4mm were employed. UV preionization was introduced in some tests to create various discharge modes (glow/arc). The findings indicate significantly higher recovery rates in air than in N 2 , presumably due to attachment processes. In addition, the presence of pre-breakdown UV was found to influence the discharge mode, thus affecting the recovery rate of the gap. Hold-off voltage curves for the previously mentioned gases, background pressures and electrode spacing will be presented along with open shutter photographs of the various discharge modes

  5. Bunch-by-bunch feedback for PEP II

    International Nuclear Information System (INIS)

    Oxoby, G.; Claus, R.; Eisen, N.; Fox, J.; Hindi, H.; Hoeflich, J.; Olsen, J.; Sapozhnikov, L.; Linscott, I.

    1993-01-01

    The proposed PEP II B factory at SLAC requires a feedback to damp out longitudinal synchrotron oscillations. A time domain, downsampled, bunch-by-bunch feedback system in which each bunch is treated as an oscillator being driven by disturbances from other bunches is presented as we review the evolution of the system design. Results from a synchrotron oscillation damping experiment conducted at the SLAC/SSRL/SPEAR ring are also presented in this paper

  6. Obtaining the Bunch Shape in a Linac from Beam Spectrum Measurements

    International Nuclear Information System (INIS)

    Bane, Karl LF

    1999-01-01

    In linacs with high single-bunch charge, and tight tolerances for energy spread and emittance growth, controlling the short-range wakefield effects becomes extremely important. The effects of the wakefields, in turn, depend on the bunch length and also on the bunch shape. It was shown in the linac of the Stanford Linear Collider (SLC), for example, that by shaping the bunch, the final rms energy spread could be greatly reduced, compared to for the standard Gaussian bunch shape[1]. Therefore, in machines with high single-bunch charge, a method of measuring bunch shape can be an important beam diagnostic. In a linac with low single-bunch charge, the longitudinal bunch shape can be obtained relatively easily from a single measurement of the beam's final energy spectrum, provided that the final to initial energy ratio is large. One merely shifts the average phase of the beam, so that it rides off-crest sufficiently to induce an energy variation that is monotonic with longitudinal position. Then, by knowing the initial and final energies, the rf wave number, and the average beam phase, one can directly map the spectrum into the bunch shape. In a linac with high single-bunch charge, however, due to the effect of the longitudinal wakefield, this method either does not work at all, or it requires such a large shift in beam phase as to become impractical. In earlier work[2],[3] it was shown that, even when wakefields are important, if one measures the final beam spectrum for two different (properly chosen) values of beam phase, then one can again obtain the bunch shape, and--as a by-product--also the form of the wakefield induced voltage; this method was then illustrated using data from the linac of the SLC. These SLC measurements, however, had been performed with the machine in a special configuration, where the current was low; in addition, the noise the data was low and the measured spectra were smooth distributions. Under normal SLC conditions, however, the currents

  7. Current status of brachytherapy in cancer treatment – short overview

    Directory of Open Access Journals (Sweden)

    Janusz Skowronek

    2017-12-01

    Full Text Available Cancer incidence and mortality depend on a number of factors, including age, socio-economic status and geographical location, and its prevalence is growing around the world. Most of cancer treatments include external beam radiotherapy or brachytherapy. Brachytherapy, a type of radiotherapy with energy from radionuclides inserted directly into the tumor, is increasingly used in cancer treatment. For cervical and skin cancers, it has become a standard therapy for more than 100 years as well as an important part of the treatment guidelines for other malignancies, including head and neck, skin, breast, and prostate cancers. Compared to external beam radiotherapy, brachytherapy has the potential to deliver an ablative radiation dose over a short period of time directly to the altered tissue area with the advantage of a rapid fall-off in dose, and consequently, sparing of adjacent organs. As a result, the patient is able to complete the treatment earlier, and the risks of occurrence of another cancer are lower than in conventional radiotherapy treatment. Brachytherapy has increased its use as a radical or palliative treatment, and become more advanced with the spread of pulsed-dose-rate and high-dose-rate afterloading machines; the use of new 3D/4D planning systems has additionally improved the quality of the treatment. The aim of the present study was to present short summaries of current studies on brachytherapy for the most frequently diagnosed tumors. Data presented in this manuscript should help especially young physicians or physicists to explore and introduce brachytherapy in cancer treatments.

  8. Absolute beam-charge measurement for single-bunch electron beams

    International Nuclear Information System (INIS)

    Suwada, Tsuyoshi; Ohsawa, Satoshi; Furukawa, Kazuro; Akasaka, Nobumasa

    2000-01-01

    The absolute beam charge of a single-bunch electron beam with a pulse width of 10 ps and that of a short-pulsed electron beam with a pulse width of 1 ns were measured with a Faraday cup in a beam test for the KEK B-Factory (KEKB) injector linac. It is strongly desired to obtain a precise beam-injection rate to the KEKB rings, and to estimate the amount of beam loss. A wall-current monitor was also recalibrated within an error of ±2%. This report describes the new results for an absolute beam-charge measurement for single-bunch and short-pulsed electron beams, and recalibration of the wall-current monitors in detail. (author)

  9. Short Review: Mitigation of Current Environmental Concerns from Methanol Synthesis

    Directory of Open Access Journals (Sweden)

    Andrew Young

    2013-06-01

    Full Text Available Methanol has become a widely used and globally distributed product. Methanol is very important due to the current depletion of fossil fuels. Industrially, methanol produced from the catalytic reaction of synthetic gas composed of hydrogen, carbon monoxide, and carbon dioxide. Methanol production has brought great attention due to carbon dioxide as the main source of greenhouse gas emissions. Combined of reducing CO2 emissions and supplying an alternative fuel source has created the idea of a carbon neutral cycle called “the methanol economy”. The best catalyst for the methanol economy would show a high CO2 conversion and high selectivity for methanol production. This paper investigates research focused on catalyst development for efficient methanol synthesis from hydrogenation of carbon dioxide through added various supports and additives such as silica, zirconium, and palladium. Catalysts that displayed the highest activity included a zirconia and silicon-titanium oxide promoted Cu/Zn/Al2O3 catalyst. Alternative method of catalyst preparation, include the oxalate-gel, solid-state reaction, co-precipitation and combustion method also investigated.  © 2013 BCREC UNDIP. All rights reservedReceived: 10th October 2012; Revised: 7th February 2012; Accepted: 10th February 2013[How to Cite: Young, A., Lesmana, D., Dai, D.J., Wu, H.S. (2013. Short Review: Mitigation of Current En-vironmental Concerns from Methanol Synthesis. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (1: 1-13. (doi:10.9767/bcrec.8.1.4055.1-13][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.1.4055.1-13] | View in  |

  10. A high current, short pulse electron source for wakefield accelerators

    International Nuclear Information System (INIS)

    Ho, Ching-Hung.

    1992-01-01

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed

  11. Multi-bunch energy compensation in the NLC bunch compressor

    International Nuclear Information System (INIS)

    Zimmermann, F.; Raubenheimer, T.O.; Thomson, K.A.

    1996-06-01

    The task of the NLC bunch compressor is to reduce the length of each bunch in a train of 90 bunches from 4 mm, at extraction from the damping ring, to about 100 μm, suitable for injection into the X-band main linac. This task is complicated by longitudinal long-range wake fields and the multi-bunch beam loading in the various accelerating sections of the compressor. One possible approach to compensate the multi-bunch beam loading is to add two RF systems with slightly different frequencies (' Δf' scheme) to each accelerating section, as first proposed by Kikuchi. This paper summarizes the choice of parameters for three such compensating sections, and presents simulation results of combined single- and multi-bunch dynamics for four different NLC versions. The multi-bunch energy compensation is shown to be straightforward and its performance to be satisfactory

  12. Single bunch fast longitudinal instability

    International Nuclear Information System (INIS)

    Wang, J.M.; Pellegrini, C.

    1979-01-01

    Single bunch longitudinal instability producing an increase of the bunch area have been observed in proton synchrotron and storage rings. Signals at microwave frequencies are observed during the bunch blow-up and because of this the effect has been called the microwave instability. A similar increase in bunch area is observed also in electron storage rings, where it is usually referred to as the bunch lengthening effect. This paper is an attempt to obtain a more general theory of this effect. Here we describe the model used and the method of calculation, together with some general results. More detailed results will be given in another paper. The main result is the derivation of a condition for the existence of a fast longitudinal bunch blow-up. This condition is a generalized threshold formula, showing explicitly the dependence on the bunch energy spread and length. This condition is qualitatively in agreement with Boussard's suggestion

  13. Single bunch fast longitudinal instability

    International Nuclear Information System (INIS)

    Wang, J.M.; Pellegrini, C.

    1979-01-01

    Single bunch longitudinal instability producing an increase of the bunch areas has been observed in proton synchrotron and storage rings. Singals at microwave frequencies are observed during the bunch blow-up and because of this the effect has been called the microwave instability. A similar increase in bunch area is observed also in electron storage rings, where it is usually referred to as the bunch lengthening effect. This paper is an attempt to obtain a more general theory of this effect. Here we describe the model used and the method of calculation, together with some general results. The main result of this paper is the derivation of a condition for the existence of a fast longitudinal bunch blow-up. This condition is a generalized threshold formula, showing explicitly the dependence on the bunch energy spread and length

  14. 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.

  15. Current state and environmental impact assessment for utilizing oil palm empty fruit bunches for fuel, fiber and fertilizer – A case study of Malaysia

    International Nuclear Information System (INIS)

    Chiew, Yoon Lin; Shimada, Sohei

    2013-01-01

    This paper describes the trend of utilizing oil palm residue, i.e. the empty fruit bunches (EFB) left after extraction of the palm oil, using a case study of Malaysia, which is one of the world's major palm oil producers, and discusses the environmental performance of recycling technologies being developed in Malaysia for fuel, fiber, and fertilizer. Seven technologies are analyzed: ethanol production, methane recovery, briquette production, biofuel for combined heat and power (CHP) plants, composting, medium density fiberboard (MDF) production, and pulp and paper production. The life cycle assessment (LCA) method is used to discuss the environmental impacts of these technologies for adding value to this biomass. Sensitivity analyses are conducted to determine the land use effects for the various technologies utilizing EFB and to estimate the energy generation potential of raw EFB in CHP plants and methane production. Among the technologies for energy production, CHP plants have the best performance if the electricity generated is connected to the national grid, with superior benefits in the majority of impact categories compared to briquette, methane, and ethanol production. Overall, we find that methane recovery and composting are more environmentally friendly than other technologies, as measured by reduction of greenhouse gas emissions. Pulp and paper, and MDF production are favorable technologies for land use impacts; however, they have intense primary energy requirements, chemical use in the processes, and emissions from their waste treatment systems. Our results provide information for decision makers when planning for sustainable use of oil palm biomass. -- Highlights: ► The recent technologies that utilize oil palm empty fruit bunches in Malaysia are evaluated using LCA. ► EFB used as fuel has significant benefits to environment compared to use as fertilizer. ► EFB used for fiber production contribute benefits to land use. ► This study provides

  16. 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.

  17. 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.

  18. Application of constrained deconvolution technique for reconstruction of electron bunch profile with strongly non-Gaussian shape

    Science.gov (United States)

    Geloni, G.; Saldin, E. L.; Schneidmiller, E. A.; Yurkov, M. V.

    2004-08-01

    An effective and practical technique based on the detection of the coherent synchrotron radiation (CSR) spectrum can be used to characterize the profile function of ultra-short bunches. The CSR spectrum measurement has an important limitation: no spectral phase information is available, and the complete profile function cannot be obtained in general. In this paper we propose to use constrained deconvolution method for bunch profile reconstruction based on a priori-known information about formation of the electron bunch. Application of the method is illustrated with practically important example of a bunch formed in a single bunch-compressor. Downstream of the bunch compressor the bunch charge distribution is strongly non-Gaussian with a narrow leading peak and a long tail. The longitudinal bunch distribution is derived by measuring the bunch tail constant with a streak camera and by using a priory available information about profile function.

  19. Application of constrained deconvolution technique for reconstruction of electron bunch profile with strongly non-Gaussian shape

    International Nuclear Information System (INIS)

    Geloni, G.; Saldin, E.L.; Schneidmiller, E.A.; Yurkov, M.V.

    2004-01-01

    An effective and practical technique based on the detection of the coherent synchrotron radiation (CSR) spectrum can be used to characterize the profile function of ultra-short bunches. The CSR spectrum measurement has an important limitation: no spectral phase information is available, and the complete profile function cannot be obtained in general. In this paper we propose to use constrained deconvolution method for bunch profile reconstruction based on a priori-known information about formation of the electron bunch. Application of the method is illustrated with practically important example of a bunch formed in a single bunch-compressor. Downstream of the bunch compressor the bunch charge distribution is strongly non-Gaussian with a narrow leading peak and a long tail. The longitudinal bunch distribution is derived by measuring the bunch tail constant with a streak camera and by using a priory available information about profile function

  20. 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

    Science.gov (United States)

    Zhao, Jifei; Lu, Xiangyang; Zhou, Kui; Yang, Ziqin; Yang, Deyu; Luo, Xing; Tan, Weiwei; Yang, Yujia

    2016-06-01

    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.

  1. 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

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jifei; Lu, Xiangyang, E-mail: xylu@pku.edu.cn; Yang, Ziqin; Yang, Deyu; Tan, Weiwei; Yang, Yujia [Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, 100871 (China); Zhou, Kui; Luo, Xing [Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900 (China)

    2016-06-15

    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.

  2. 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.

  3. LASL high-current proton storage rings

    International Nuclear Information System (INIS)

    Lawrence, G.P.; Cooper, R.K.; Hudgings, D.W.; Spalek, G.; Jason, A.J.; Higgins, E.F.; Gillis, R.E.

    1980-01-01

    The Proton Storage Ring at LAMPF is a high-current accumulator designed to convert long 800-MeV linac pulses into very short high-intensity proton bunches ideally suited to driving a pulsed polyenergetic neutron source. The Ring, authorized for construction at $19 million, will operate in a short-bunch high-frequency mode for fast neutron physics and a long-bunch low-frequency mode for thermal neutron-scattering programs. Unique features of the project include charge-changing injection with initial conversion from H - to H 0 , a high repetition rate fast-risetime extraction kicker, and high-frequency and first-harmonic bunching system

  4. 30 CFR 75.601-3 - Short circuit protection; dual element fuses; current ratings; maximum values.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Short circuit protection; dual element fuses... Trailing Cables § 75.601-3 Short circuit protection; dual element fuses; current ratings; maximum values. Dual element fuses having adequate current-interrupting capacity shall meet the requirements for short...

  5. Transparent lattice characterization with gated turn-by-turn data of diagnostic bunch train

    Science.gov (United States)

    Li, Yongjun; Cheng, Weixing; Ha, Kiman; Rainer, Robert

    2017-11-01

    Methods of characterization of a storage ring's lattice have traditionally been intrusive to routine operations. More importantly, the lattice seen by particles can drift with the beam current due to collective effects. To circumvent this, we have developed a novel approach for dynamically characterizing a storage ring's lattice that is transparent to operations. Our approach adopts a dedicated filling pattern which has a short, separate diagnostic bunch train (DBT). Through the use of a bunch-by-bunch feedback system, the DBT can be selectively excited on demand. Gated functionality of a beam position monitor system is capable of collecting turn-by-turn data of the DBT, from which the lattice can then be characterized after excitation. As the DBT comprises only about one percent of the total operational bunches, the effects of its excitation are negligible to users. This approach allows us to localize the distributed quadrupolar wakefields generated in the storage ring vacuum chamber during beam accumulation. While effectively transparent to operations, our approach enables us to dynamically control the beta beat and phase beat, and unobtrusively optimize performance of the National Synchrotron Light Source-II accelerator during routine operations.

  6. 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...

  7. Generation and transport of double-bunch electron beams in the FLASH beamline

    International Nuclear Information System (INIS)

    Entrena Utrilla, Carlos Manuel

    2014-10-01

    The Free Electron Laser in Hamburg (FLASH) is part of the Deutsches Elektronen-Synchrotron (DESY) research center. Its linear accelerator produces high-quality electron bunches of up to about 1.2 GeV that are used in its undulator to generate short, intense, high-brilliance soft-X ray pulses with a wavelength from 4.2 nm to 45 nm with the SASE process. This characteristics make FLASH a leading facility worldwide in photon science and linear accelerator technologies, along with the Linac Coherent Light Source (in SLAC, Standford, USA), the FERMI rate at Elettra in Trieste (Italy) and SACLA (Japan). For several reasons, there is a substantial interest to accelerate two electron bunches with a final temporal distance of several hundreds of femtoseconds. These two bunches are generated on the photocathode within picoseconds from each other and accelerated within the same RF bucket (the same period of the RF (radio-frequency) accelerating fields). These experiments are of interest for two-color FEL for pump-probe experiments, and for the external injection of electrons in the future particle-driven plasma wakefield accelerator experiment, called FLASHForward, which will start in early 2016. This work analyzes the longitudinal dynamics of said double-bunches, from generation on the photocathode to the transport and compression through the linac. It is shown how a working point for a desired compression scenario (shape and final current of the bunches, and final distance between them) can be found with different numerical tracking procedures, and how the electrons can be experimentally generated and transported through the accelerator in the current layout, which was confirmed in a proof-of-concept experiment in late May 2014.

  8. Short Report: New use of current technology to measure rectal ...

    African Journals Online (AJOL)

    South African Journal of Sports Medicine. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 17, No 1 (2005) >. Log in or Register to get access to full text downloads.

  9. The SPS Individual Bunch Measurement System

    CERN Document Server

    Guerrero, A; Jones, R; Savioz, J J

    2001-01-01

    The Individual Bunch Measurement System (IBMS) allows the intensity of each bunch in an LHC batch to be the measured both in the PS to SPS transfer lines and in the SPS ring itself. The method is vased on measuring the peak and valley of the analogue signal supplied by a Fast Beam Current Transformer at a frequency of 40 MHz. A 12 bit acquisition system is required to obtain a 1% resolution for the intensity range of 5X10`9 to 1.7X10`11 protons per bunch, corresponding to the pilot and ultimate LHC bunch intensities. The acquisition selection and external trigger adjustment system is driven by the 200MHz RF, which is distributed using a single-mode fibre-optic link. A local oscilloscope, controlled via a GPIB interface, allows the remote adjustment of the timing signals. The low-level software consists of a real-time task and a communication server run on a VME Power PC, which is accessed using a graphical user interface. This paper describes the system as a whole and presents some recent uses and results fro...

  10. Bunch monitor for an S-band electron linear accelerator

    International Nuclear Information System (INIS)

    Otake, Yuji; Nakahara, Kazuo

    1991-01-01

    The measurement of bunch characteristics in an S-band electron linear accelerator is required in order to evaluate the quality of accelerated electron beams. A new-type bunch monitor has been developed which combines micro-stripline technology with an air insulator and wall-current monitoring technology. The obtained time resolution of the monitor was more than 150 ps. This result shows that the monitor can handle the bunch number of an S-band linac. The structure of the monitor is suitable for being installed in the vacuum area, since it is constructed of only metal and ceramic parts. It can therefore easily be employed in an actual machine

  11. SuperB Bunch-By-Bunch Feedback R&D

    Energy Technology Data Exchange (ETDEWEB)

    Drago, A.; Beretta, M.; /Frascati; Bertsche, K.; Novokhatski, A.; /SLAC; Migliorati, M.; /Rome U.

    2011-08-12

    The SuperB project has the goal to build in Italy, in the Frascati or Tor Vergata area, an asymmetric e{sup +}/e{sup -} Super Flavor Factory to achieve a peak luminosity > 10**36 cm{sup -2} s{sup -1}. The SuperB design is based on collisions with extremely low vertical emittance beams and high beam currents. A source of emittance growth comes from the bunch by bunch feedback systems producing high power correction signals to damp the beams. To limit any undesirable effect, a large R&D program is in progress, partially funded by the INFN Fifth National Scientific Committee through the SFEED (SuperB Feedback) project approved within the 2010 budget. The SuperB project [1] has the goal to build in Italy, in the Frascati or Tor Vergata area, an asymmetric e{sup +}/e{sup -} Super Flavor Factory to achieve a peak luminosity > 10**36 cm{sup -2} s{sup -1}. In the last and current years, the machine layout has been deeply modified, in particular the main rings are now shorter and an option with high currents has been foreseen. In the fig.1 the new SuperB layout is shown. From bunch-by-bunch feedback point of view, the simultaneous presence in the machine parameters, of very low emittance, of the order of 5-10 pm in the vertical plane, and very high currents, at level of 4 Ampere for the Low Energy Ring, asks for designing very carefully the bunch-by-bunch feedback systems. The parameter list is presented in Fig. 2. The bunch-by-bunch feedback design must take care of the risky and exciting challenges proposed in the SuperB specifications, but it should consider also some other important aspects: flexibility in terms of being able to cope to unexpected beam behaviours [2], [3] legacy of previous version experience [4], [5] and internal powerful diagnostics [6] as in the systems previously used in PEP-II and DAFNE [7].

  12. Emittance growth due to static and radiative space charge forces in an electron bunch compressor

    Science.gov (United States)

    Talman, Richard; Malitsky, Nikolay; Stulle, Frank

    2009-01-01

    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 (2004)PRABFM1098-440210.1103/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 , Nucl. Instrum. Methods Phys. Res., Sect. A 455, 185 (2000)NIMAER0168-900210.1016/S0168-9002(00)00729-4] 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 γx on beam width (as controlled by the lattice βx 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 , 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 2004 FEL Conference, pp. 18

  13. 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.

  14. Approximative calculation of transient short-circuit currents in power-systems

    Energy Technology Data Exchange (ETDEWEB)

    Heuck, K; Rosenberger, R; Dettmann, K D; Kegel, R

    1986-08-01

    The paper shows that it is approximatively possible to calculate the transient short-circuit currents for symmetrical and asymmetrical faults in power-systems. For that purpose a simple equivalent network is found. Its error of approximation is small. For the important maximum short-circuit current limits of error are pointed out compared to VDE 0102.

  15. Bunch length and impedance measurements in SPEAR

    International Nuclear Information System (INIS)

    Bane, K.; Donald, M.; Hofmann, A.; Jowett, J.; Lockman, W.; Morton, P.; Stege, R.; Spence, W.; Wilson, P.

    1988-05-01

    Subsequent to an extensive smoothing of the vacuum chamber a comprehensive study of the SPEAR impedance was undertaken. Bunch length, synchrotron quadrupole mode frequency, and parasitic mode loss were measured as functions of beam current. The results showed that, although the gross longitudinal impedance had indeed been reduced, the 'capacitive' component had also decreased relative to the 'inductive'--to the extent that previously compensated potential well distortion now induced bunch lengthening at low currents, and the turbulent threshold had actually been lowered. A specially designed multi-cell disc-loaded 'capacitor' cavity was shown to be capable of removing this effect by restoring the original compensation. A model of the new SPEAR impedance is also obtained. 7 refs., 6 figs

  16. Bunch length and impedance measurements in SPEAR

    International Nuclear Information System (INIS)

    Bane, K.; Donald, M.; Morton, P.; Stege, R.; Spence, W.; Wilson, P.; Hofmann, A.; Jowett, J.; Lockman, W.

    1988-01-01

    Subsequent to an extensive smoothing of the vacuum chamber a comprehensive study of the SPEAR impedance was undertaken. Bunch length, synchrotron quadrupole mode frequency, and parasitic mode loss were measured as functions of beam current. This paper shows that although the gross longitudinal impedance had indeed been reduced, the capacitive component had also decreased relative to the inductive - to the extent that previously compensated potential well distortion now induced bunch lengthening at low currents, and the turbulent threshold had actually been lowered. A specially designed multi-cell disc-loaded capacitor cavity was shown to be capable of removing this effect by restoring the original compensation. A model of the new SPEAR impedance is also obtained

  17. Creation and storage of long and flat bunches in the LHC

    Energy Technology Data Exchange (ETDEWEB)

    Damerau, H.

    2005-09-01

    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 400.8 MHz, long and flat bunches held by multiples of 40.08 MHz, 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 combine a batch of ordinary bunches into a long and flat bunch is proposed. These RF gymnastics are based on well-proven techniques such as batch compression and bunch pair merging. Their advantages and disadvantages, including optimization with respect to degradation of the longitudinal particle density, are discussed in detail. Special attention is paid to the investigation of collective effects due to the large line charge density and the influence of the beam on the RF installation is also studied. (Orig.)

  18. PF-KO system for single bunch mode operation of a storage ring

    International Nuclear Information System (INIS)

    Ohgaki, H.; Sugiyama, S.; Mikado, T.; Chiwaki, M.; Yamada, K.; Suzuki, R.; Sei, N.; Noguchi, T.; Yamazaki, T.

    1994-01-01

    A new RF-KO (RF knockout) system for the single bunch mode operation of a storage ring has been developed. The knockout signal is modulated by the sum signal of the RF acceleration frequency of the storage ring and a bunch selection signal. We do not need any special device or a timing unit with this method. We obtain a high purity of bunch structure in a short knock out time. The single bunch impurity of 0.2% has been achieved. (author)

  19. Main Ring bunch spreaders: Past, 1987/1988 fixed target run, and proposed future

    International Nuclear Information System (INIS)

    Jackson, G.P.

    1989-01-01

    During the last 1987--1988 fixed target running period beam intensity was limited many times by coherent instabilities in both the Main Ring and in the Tevatron. The intensity thresholds for instabilities are generally inversely proportional to the proton bunch length. Since fixed target operations are insensitive to the longitudinal phase space emittance of the beam, bunch spreaders are employed to increase this emittance, and hence the bunch length. As a result, more beam intensity can be delivered to the fixed target experiments. This paper starts with a short history behind the old Main Ring bunch spreader. After discussing the physics of stimulated emittance growth, the design and performance of the 1987--1988 fixed target run Main Ring bunch spreader is discussed. Finally, designs of improved Main Ring and Tevatron bunch spreaders for the next fixed target run are proposed. 23 figs

  20. Bunch Length Measurements using Coherent Radiation

    CERN Document Server

    Ischebeck, Rasmus; Barnes, Christopher; Blumenfeld, Ian; Clayton, Chris; Decker, Franz Josef; Deng, Suzhi; Hogan, Mark; Huang Cheng Kun; Iverson, Richard; Johnson, Devon K; Krejcik, Patrick; Lu, Wei; Marsh, Kenneth; Oz, Erdem; Siemann, Robert; Walz, Dieter

    2005-01-01

    The accelerating field that can be obtained in a beam-driven plasma wakefield accelerator depends on the current of the electron beam that excites the wake. In the E-167 experiment, a peak current above 10kA will be delivered at a particle energy of 28GeV. The bunch has a length of a few ten micrometers and several methods are used to measure its longitudinal profile. Among these, autocorrelation of coherent transition radiation (CTR) is employed. The beam passes a thin metallic foil, where it emits transition radiation. For wavelengths greater than the bunch length, this transition radiation is emitted coherently. This amplifies the long-wavelength part of the spectrum. A scanning Michelson interferometer is used to autocorrelate the CTR. However, this method requires the contribution of many bunches to build an autocorrelation trace. The measurement is influenced by the transmission characteristics of the vacuum window and beam splitter. We present here an analysis of materials, as well as possible layouts ...

  1. Multi-bunch feedback systems

    CERN Document Server

    Lonza, M

    2008-01-01

    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. The 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. The lecture will 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 feedbacks systems will then be presented as examples of real implementations that belong to the history of multi-bunch feedback sy...

  2. 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...

  3. Current-zero measurements of vacuum circuit breakers interrupting short-line faults

    NARCIS (Netherlands)

    Smeets, R.P.P.; Linden, van der W.A.

    2003-01-01

    Current zero measurements are performed during short-line fault interruption tests of vacuum circuit breakers. This switching cycle is characterized by a very steep transient recovery voltage. High-resolution measurements of near current-zero arc current and voltage were carried out. Various

  4. Short-Circuit Current Analysis for DFIG Wind Farm Considering the Action of a Crowbar

    Directory of Open Access Journals (Sweden)

    Yan Hong Yuan

    2018-02-01

    Full Text Available With the increasing capacity of wind farms integrated into the power grid, the short-circuit current analysis for wind farms becomes more and more important. Since the wind turbine is usually integrated into the power grid via power electronic devices, the “crowbar” is installed in the wind turbine to protect the power electronic devices and to improve the fault ride through capability. The impact of the crowbar has to be considered during the short-circuit current analysis for the wind farm. In order to fully analyze the short-circuit current characteristics of a wind farm, the short-circuit currents for a doubly-fed induction generator (DFIG wind turbine under symmetrical and asymmetrical faults considering the crowbar action characteristic are derived firstly. Then the action situation of the crowbar of a DFIG wind turbine is studied and the action area curve is obtained. Taking the crowbar action, or not, as the grouping criterion, wind turbines in the wind farm are divided into two groups, and the wind farm is aggregated into two equivalent wind turbines. Using the equivalent model, the short-circuit current of a wind farm can be calculated accurately. Finally, simulations are performed in MATLAB/Simulink which is the commercial math software produced by the MathWorks company in Natick, Massachusetts, the United States to verify the proposed short-circuit current calculation method for the DFIG wind farm.

  5. Intra-bunch-train transverse dynamics in the superconducting accelerators FLASH and European XFEL

    Energy Technology Data Exchange (ETDEWEB)

    Hellert, Thorsten

    2017-11-15

    FLASH and the European XFEL are linear accelerator driven SASE-FELs, operating in a pulsed mode with long bunch-trains. Multi-bunch FEL operation requires longitudinal and transverse stability within the bunch-train. The purpose of this work is to investigate the intra-bunch-train transverse dynamics at FLASH and XFEL. Key relationships of superconducting RF cavity operation, their misalignments and the resulting impact on the intra-bunch-train trajectory variation are described. In this thesis a numerical model is developed and simulations for different accelerating sections at FLASH and XFEL are performed. With the current operational setup significant intra-bunch-train trajectory variation must be considered, hence approaches for their reduction are discussed. The theoretical studies are compared to experimental results at FLASH. The observed trajectory variation during multi-bunch user runs is analyzed and related to causal intra-bunch-train variations of the RF and the following impact on the multi-bunch SASSE performance. Furthermore, HOM-based cavity misalignment measurements are performed and the deduction of misalignments from multi-bunch data is considered.

  6. Measurement of multi-bunch transfer functions using time-domain data and Fourier analysis

    International Nuclear Information System (INIS)

    Hindi, H.; Sapozhnikov, L.; Fox, J.; Prabhakar, S.; Oxoby, G.; Linscott, I.; Drago, A.

    1993-12-01

    Multi-bunch transfer functions are principal ingredients in understanding both the behavior of high-current storage rings as well as control of their instabilities. The measurement of transfer functions on a bunch-by-bunch basis is particularly important in the design of active feedback systems. Traditional methods of network analysis that work well in the single bunch case become difficult to implement for many bunches. We have developed a method for obtaining empirical estimates of the multi-bunch longitudinal transfer functions from the time-domain measurements of the bunches' phase oscillations. This method involves recording the response of the bunch of interest to a white-noise excitation. The transfer function can then be computed as the ratio of the fast Fourier transforms (FFTs) of the response and excitation sequences, averaged over several excitations. The calculation is performed off-line on bunch-phase data and is well-suited to the multi-bunch case. A description of this method and an analysis of its performance is presented with results obtained using the longitudinal quick prototype feedback system developed at SLAC

  7. Intra-bunch-train transverse dynamics in the superconducting accelerators FLASH and European XFEL

    International Nuclear Information System (INIS)

    Hellert, Thorsten

    2017-11-01

    FLASH and the European XFEL are linear accelerator driven SASE-FELs, operating in a pulsed mode with long bunch-trains. Multi-bunch FEL operation requires longitudinal and transverse stability within the bunch-train. The purpose of this work is to investigate the intra-bunch-train transverse dynamics at FLASH and XFEL. Key relationships of superconducting RF cavity operation, their misalignments and the resulting impact on the intra-bunch-train trajectory variation are described. In this thesis a numerical model is developed and simulations for different accelerating sections at FLASH and XFEL are performed. With the current operational setup significant intra-bunch-train trajectory variation must be considered, hence approaches for their reduction are discussed. The theoretical studies are compared to experimental results at FLASH. The observed trajectory variation during multi-bunch user runs is analyzed and related to causal intra-bunch-train variations of the RF and the following impact on the multi-bunch SASSE performance. Furthermore, HOM-based cavity misalignment measurements are performed and the deduction of misalignments from multi-bunch data is considered.

  8. Resistive theory of bunch lengthening

    International Nuclear Information System (INIS)

    Month, M.; Messerschmid, E.

    1977-01-01

    A new theory of bunch lengthening in electron storage rings is proposed. The equilibrium bunch length is that length which stabilizes the bunch against the onset of ''fast'' resistive instability, caused by the combination of many high frequency resonators such as vacuum flanges. The heat dissipated in these impedance sources follows immediately from the bunch length. It is found that the anomalous bunch length is determined by a scaling parameter g = (hVcos phi/sub s/)/I. Data taken in SPEAR I and II, data in which g extends in value by more than three orders of magnitude, can be fit with an appropriate choice of high frequency, large width coupling impedance. The impedance functions for SPEAR I and II are taken to be the same, a reflection of the fact that the high frequency sources are chamber discontinuities rather than structures connected with the rf systems. A parameter search leads to an impedance characterized by a central frequency approximately 5 GHz, a width (FWHM) approximately 1.8 GHz and a peak impedance approximately 0.2 M OMEGA. The expected and observed higher mode resistance (i.e., heat dissipated) for SPEAR are compared and found to be in agreement. Predictions are given for PEP and PETRA

  9. Bunching phase and constraints on echo enabled harmonic generation

    Science.gov (United States)

    Hemsing, E.

    2018-05-01

    A simple mathematical description is developed for the bunching spectrum in echo enabled harmonic generation (EEHG) that incorporates the effect of additional electron beam energy modulations. Under common assumptions, they are shown to contribute purely through the phase of the longitudinal bunching factor, which allows the spectral moments of the bunching to be calculated directly from the known energy modulations. In particular, the second moment (spectral bandwidth) serves as simple constraint on the amplitude of the energy modulations to maintain a transform-limited seed. We show that, in general, the impact on the spectrum of energy distortions that develop between the EEHG chicanes scales like the harmonic number compared to distortions that occur upstream. This may limit the parameters that will allow EEHG to reach short wavelengths in high brightness FELs.

  10. Enhanced coherent undulator radiation from bunched electron beams

    International Nuclear Information System (INIS)

    Berryman, K.W.; Crosson, E.R.; Ricci, K.N.; Smith, T.I.

    1996-01-01

    When energetic bunches of electrons traverse an undulator field, they can spontaneously emit radiation both coherently and incoherently. Although it has generally been assumed that undulator radiation is incoherent at wavelengths short compared to the longitudinal size of the electron bunch, several recent observations have proved this assumption false. Furthermore, the appearance of coherent radiation is often accompanied by a significant increase in radiated power. Here we report observations of strongly enhanced coherent spontaneous radiation together with direct measurements, using transition radiation techniques, of the electron distributions responsible for the coherent emission. We also report demonstrated enhancements in the predicted spontaneous radiated power by as much as 6x10 4 using electron bunch compression. copyright 1996 American Institute of Physics

  11. Transverse multibunch modes for non-rigid bunches, including mode coupling

    Energy Technology Data Exchange (ETDEWEB)

    Berg, J S; Ruth, R D [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

    1996-08-01

    A method for computing transverse multibunch growth rates and frequency shifts in rings, which has been described previously, is applied to the PEP-II B factory. The method allows multibunch modes with different internal-bunch oscillation modes to couple to one another, similar to single-bunch mode coupling. Including coupling between the multibunch modes gives effects similar to those seen in single-bunch mode coupling. These effects occur at currents that are lower than the single-bunch mode coupling threshold. (author)

  12. Acceleration of electrons at wakefield excitation by a sequence of relativistic electron bunches in dielectric resonator

    International Nuclear Information System (INIS)

    Kiselev, V.A.; Linnik, A.F.; Mirnyj, V.I.; Onishchenko, I.N.; Uskov, V.V.

    2009-01-01

    Method is proposed to divide a regular sequence of electron bunches into parts of bunches driving wakefield and witness bunches, which should be accelerated. It allows to avoid the necessity of additional electron accelerator for witness bunches producing and the necessity of precision short time techniques of injection phase adjusting. The idea concludes to the frequency detuning between bunches repetition frequency and the frequency of the fundamental mode of excited wakefield. Experiments were carried out on the linear resonant accelerator 'Almaz-2', which injected in the dielectric resonator a sequence of 6000 short bunches of relativistic electrons with energy 4.5 MeV, charge 0.16 nC and duration 60 psec each, the repetition interval 360 ps. Frequency detuning was entered by change of frequency of the master generator of the klystron within the limits of one percent so that the phase taper on the length of bunches sequence achieved 2π. Energy spectra of electrons of bunches sequence, which have been propagated through the dielectric resonator are measured and analyzed

  13. Coherent radiation from high-current electron beams of linear accelerators and its applications

    International Nuclear Information System (INIS)

    Okuda, Shuichi; Takanaka, Makoto; Nakamura, Mitsumi; Kato, Ryukou; Takahashi, Toshiharu; Nam, Soon-Kwon; Taniguchi, Ryouichi; Kojima, Takao

    2006-01-01

    The characteristics of the far-infrared light source using the coherent radiation emitted from a high-energy short electron bunch have been investigated. The coherent radiation has a continuous spectrum in a submillimeter to millimeter wavelength range and the brightness is relatively high. The spectrum of the radiation is determined by the longitudinal form factor of the electron bunch. The operational conditions of a high-current linear accelerator have been optimized using an electron bunch shape monitor. The coherent transition radiation light source has been applied to absorption spectroscopy for liquid water and to an imaging experiment for a leaf of rose

  14. 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

  15. Modelling the short-circuit current of polymer bulk heterojunction solar cells

    International Nuclear Information System (INIS)

    Geens, Wim; Martens, Tom; Poortmans, Jef; Aernouts, Tom; Manca, Jean; Lutsen, Laurence; Heremans, Paul; Borghs, Staf; Mertens, Robert; Vanderzande, Dirk

    2004-01-01

    An analytical model has been developed to estimate the short-circuit current density of conjugated polymer/fullerene bulk heterojunction solar cells. The model takes into account the solvent-dependent molecular morphology of the donor/acceptor blend, which was revealed by transmission electron microscopy. Field-effect transistors based on single and composite organic layers were fabricated to determine values for the charge carrier mobilities of such films. These values served as input parameters of the model. It is shown that the difference in short-circuit current density that was measured between toluene-cast and chlorobenzene-cast conjugated polymer/fullerene photovoltaic cells (Appl. Phys. Lett. 78 (2001) 841) could be very well simulated with the model. Moreover, the calculations illustrate how increasing the hole and electron mobilities in the photoactive blend can improve the overall short-circuit current density of the solar cell

  16. Anomalous length of electron bunches as an instability threshold

    International Nuclear Information System (INIS)

    Messerschmid, E.; Month, M.

    1976-01-01

    A mechanism for the anomalous length of electron bunches, based on the existence of a ''fast'' longitudinal instability, is proposed. The equilibrium length is obtained by requiring that the growth rate be sufficiently larger than the rate of synchrotron oscillations. The theory is used to describe the bunch length data for SPEAR at 1.5 GeV. The low voltage and/or high current regime is dominated by a set of ''low'' frequency, low Q resonators [e.g., f = 320 MHz, Δf(fwhm) = 130 MHz]. To fit the observations in the high voltage and/or low current regime, a high frequency, low Q impedance is required (e.g., f = 3.8 GHz, Δf = 1.0 GHz). The mechanism is mediated by the resistive component of the impedance. Thus, there is qualitative agreement with the observed distortion of the bunch tail. This is in contrast to the predictions of the potential well models based on a reactive impedance source. These latter theories yield large distortions of the head of the bunch. The calculated power dissipated in the assumed sources by the given electron bunch is not inconsistent with estimates made for SPEAR

  17. 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.)

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

    International Nuclear Information System (INIS)

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

    2011-08-01

    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 μm) or in long wavelength mode (45-430 μm). 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.)

  19. Transverse and longitudinal coupled bunch instabilities in trains of closely spaced bunches

    International Nuclear Information System (INIS)

    Thompson, K.A.; Ruth, R.D.

    1989-03-01

    Damping rings for the next generation of linear collider may need to contain several bunch trains within which the bunches are quire closely spaced (1 or 2 RF wavelengths). Methods are presented for studying the transverse and longitudinal coupled bunch instabilities, applicable to this problem and to other cases in which the placement of the bunches is not necessarily symmetric. 5 refs., 1 fig

  20. Short-Circuit Current Analysis for DFIG Wind Farm Considering the Action of a Crowbar

    OpenAIRE

    Yan Hong Yuan; Feng Wu

    2018-01-01

    With the increasing capacity of wind farms integrated into the power grid, the short-circuit current analysis for wind farms becomes more and more important. Since the wind turbine is usually integrated into the power grid via power electronic devices, the “crowbar” is installed in the wind turbine to protect the power electronic devices and to improve the fault ride through capability. The impact of the crowbar has to be considered during the short-circuit current analysis for the wind farm....

  1. Defects influence on short circuit current density in p-i-n silicon solar cell

    International Nuclear Information System (INIS)

    Wagah F Mohamad; Alhan M Mustafa

    2006-01-01

    The admittance analysis method has been used to calculate the collection efficiency and the short circuit current density in a-Si:H p-i-n solar cell, as a function of the thickness of i-layer. Its is evident that the results of the short circuit current can be used to determine the optimal thickness of the i-layer of a cell, and it will be more accurate in comparison with the previous studies using a constant generation rate or an empirical exponential function for the generation of charge carriers throughout the i-layer

  2. Implementation of the Electronics Chain for the Bunch by Bunch Intensity Measurement Devices for the LHC

    CERN Document Server

    Belohrad, D; Ludwig, M; Savioz, J J; Thoulet, S

    2009-01-01

    The fast beam intensity measurements for the LHC are provided by eight Fast Beam Current Transformers (FBCT). Four FBCTs installed in the LHC rings are capable of providing both bunch-by-bunch and total turn-by-turn beam intensity information. A further four FBCTs, two in each of the LHC dump lines, are used to measure the total extracted beam intensity. In addition to providing intensity information the ring FBCTs also send signals to the machine protection system. This increases the complexity of both the RF front-end and the digital acquisition parts of the signal processing chain. The aim of this paper is to discuss the implemented hardware solution for the FBCT system, in particular with respect to the signal distribution, FPGA signal processing, calibration, and interaction of the FBCTs with the machine protection chain.

  3. Bunch coalescing and bunch rotation in the Fermilab Main Ring: Operational experience and comparison with simulations

    International Nuclear Information System (INIS)

    Martin, P.S.; Wildman, D.W.

    1988-01-01

    The Fermilab Tevatron I proton-antiproton collider project requires that the Fermilab Main Ring produce intense bunches of protons and antiprotons for injection into the Tevatron. The process of coalescing a small number of harmonic number h=1113 bunches into a single bunch by bunch-rotating in a lower harmonic rf system is described.The Main Ring is also required to extract onto the antiproton production target bunches with as narrow a time spread as possible. This operation is also discussed. The operation of the bunch coalescing and bunch rotation are compared with simulations using the computer program ESME. 2 refs., 8 figs

  4. Dynamics of electron bunches at the laser–plasma interaction in the bubble regime

    Energy Technology Data Exchange (ETDEWEB)

    Maslov, V.I., E-mail: vmaslov@kipt.kharkov.ua; Svystun, O.M., E-mail: svistun_elena@mail.ru; Onishchenko, I.N.; Tkachenko, V.I.

    2016-09-01

    The multi-bunches self-injection, observed in laser–plasma accelerators in the bubble regime, affects the energy gain of electrons accelerated by laser wakefield. However, understanding of dynamics of the electron bunches formed at laser–plasma interaction may be challenging. We present here the results of fully relativistic electromagnetic particle-in-cell (PIC) simulation of laser wakefield acceleration driven by a short laser pulse in an underdense plasma. The trapping and acceleration of three witness electron bunches by the bubble-like structures were observed. It has been shown that with time the first two witness bunches turn into drivers and contribute to acceleration of the last witness bunch.

  5. 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.

  6. Bunch compression efficiency of the femtosecond electron source at Chiang Mai University

    International Nuclear Information System (INIS)

    Thongbai, C.; Kusoljariyakul, K.; Saisut, J.

    2011-01-01

    A femtosecond electron source has been developed at the Plasma and Beam Physics Research Facility (PBP), Chiang Mai University (CMU), Thailand. Ultra-short electron bunches can be produced with a bunch compression system consisting of a thermionic cathode RF-gun, an alpha-magnet as a magnetic bunch compressor, and a linear accelerator as a post acceleration section. To obtain effective bunch compression, it is crucial to provide a proper longitudinal phase-space distribution at the gun exit matched to the subsequent beam transport system. Via beam dynamics calculations and experiments, we investigate the bunch compression efficiency for various RF-gun fields. The particle distribution at the RF-gun exit will be tracked numerically through the alpha-magnet and beam transport. Details of the study and results leading to an optimum condition for our system will be presented.

  7. Bunch compression efficiency of the femtosecond electron source at Chiang Mai University

    Science.gov (United States)

    Thongbai, C.; Kusoljariyakul, K.; Saisut, J.

    2011-07-01

    A femtosecond electron source has been developed at the Plasma and Beam Physics Research Facility (PBP), Chiang Mai University (CMU), Thailand. Ultra-short electron bunches can be produced with a bunch compression system consisting of a thermionic cathode RF-gun, an alpha-magnet as a magnetic bunch compressor, and a linear accelerator as a post acceleration section. To obtain effective bunch compression, it is crucial to provide a proper longitudinal phase-space distribution at the gun exit matched to the subsequent beam transport system. Via beam dynamics calculations and experiments, we investigate the bunch compression efficiency for various RF-gun fields. The particle distribution at the RF-gun exit will be tracked numerically through the alpha-magnet and beam transport. Details of the study and results leading to an optimum condition for our system will be presented.

  8. 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.

  9. Multi-bunch Feedback Systems

    International Nuclear Information System (INIS)

    Lonza, M; Schmickler, H

    2014-01-01

    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 components of a feedback system and the related issues will also be analysed. Finally, we shall focus on digital feedback systems, their characteristics, and features, as well as on how they can be concretely exploited for both the optimization of feedback performance and for beam dynamics studies

  10. Research on resistance characteristics of YBCO tape under short-time DC large current impact

    Science.gov (United States)

    Zhang, Zhifeng; Yang, Jiabin; Qiu, Qingquan; Zhang, Guomin; Lin, Liangzhen

    2017-06-01

    Research of the resistance characteristics of YBCO tape under short-time DC large current impact is the foundation of the developing DC superconducting fault current limiter (SFCL) for voltage source converter-based high voltage direct current system (VSC-HVDC), which is one of the valid approaches to solve the problems of renewable energy integration. SFCL can limit DC short-circuit and enhance the interrupting capabilities of DC circuit breakers. In this paper, under short-time DC large current impacts, the resistance features of naked tape of YBCO tape are studied to find the resistance - temperature change rule and the maximum impact current. The influence of insulation for the resistance - temperature characteristics of YBCO tape is studied by comparison tests with naked tape and insulating tape in 77 K. The influence of operating temperature on the tape is also studied under subcooled liquid nitrogen condition. For the current impact security of YBCO tape, the critical current degradation and top temperature are analyzed and worked as judgment standards. The testing results is helpful for in developing SFCL in VSC-HVDC.

  11. Influence of wavelength on transient short-circuit current in polycrystalline silicon solar cells

    International Nuclear Information System (INIS)

    Ba, B.; Kane, M.

    1993-10-01

    The influence of the wavelength of a monochromatic illumination on transient short-circuit current in an n/p polycrystalline silicon part solar cell junction is investigated. A wavelength dependence in the initial part of the current decay is observed in the case of cells with moderate grain boundary effects. This influence is attenuated in polycrystalline cells with strong grain boundary activity. (author). 10 refs, 6 figs

  12. Verification of the short-circuit current making capability of high-voltage switching devices

    NARCIS (Netherlands)

    Smeets, R.P.P.; Linden, van der W.A.

    2001-01-01

    Switching-in of short-circuit current leads to pre-arcing in the switching device. Pre-arcing affects the ability of switchgear to close and latch. In three-phase systems, making is associated with transient voltage phenomena that may have a significant impact on the duration of the pre-arcing

  13. Short-channel drain current model for asymmetric heavily/lightly ...

    Indian Academy of Sciences (India)

    The paper presents a drain current model for double gate metal oxide semiconductor field effect transistors (DG MOSFETs) based on a new velocity saturation model that accounts for short-channel velocity saturation effect independently in the front and the back gate controlled channels under asymmetric front and back ...

  14. Dynamic behavior of HTSC opening switch models controlled by short over-critical current pulses

    International Nuclear Information System (INIS)

    Agafonov, A.V.; Krastelev, E.G.; Voronin, V.S.

    1999-01-01

    We present results of experimental research of dynamical properties of thin films of YBa 2 Cu 3 O 7 HTSC-switch models under action of short overcritical current pulses to test this method of control of fast high-power opening switches for accelerator applications

  15. Short-rotation coppicing in France. Current state of research and prospects for future development

    Energy Technology Data Exchange (ETDEWEB)

    Bonduelle, P. (Association Foret Cellulose, Trelaze (France)); Bouvarel, L. (Institut National de la Recherche Agronomique, Olivet (France). Unite Experimentale Biomasse, Forestiere et Foret Paysanne); Petit, H. (Association pour la Rationalisation et la Mecanisation de l' Exploitation Forestiere, Fontainebleau (France)); Pierson, J. (Cellulose des Ardennes, Montemedy (France)); Savanne, D. (Agence de l' Environnement et de la Maitrise de l' Energie, 75 - Paris (France)); Sourie, J.C. (Institut National de la Recherche Agronomique, Grignon (France). Station d' Economie et de Sociologie Rurales)

    1992-01-01

    This article analyzes the current context and the prospects for crop development as well as offering a number of examples of short rotation coppicing projects. The industrial outlets created through state aid remain the primary driving force behind plantations at this time. (author)

  16. The influence of gamma irradiation on short-circuit current in CuGaSe2

    International Nuclear Information System (INIS)

    Gasimoglu, I.; Mamedova, I.A.; Bagirov, A.G.

    2005-01-01

    Full text : The influence of gamma irradiation on a short-circuit current at 77 K was investigated. The appeared strip with a maximum at 1,61 ///// after irradiation in spectral dependence connected with p-type radiating defects [ru

  17. Turn-by-Turn and Bunch-by-Bunch Transverse Profiles of a Single Bunch in a Full Ring

    International Nuclear Information System (INIS)

    Kraus, R.; Fisher, A.S.

    2005-01-01

    The apparatus described in this paper can image the evolution of the transverse profile of a single bunch, isolated from a full PEP-II ring of 1500 bunches. Using this apparatus there are two methods of single bunch imaging; bunch-by-bunch beam profiling can image every bunch in the ring a single bunch at a time with the images of sequential bunches being in order, allowing one to see variations in beam size along a train. Turn-by-turn beam profiling images a single bunch on each successive turn it makes around the ring. This method will be useful in determining the effect that an injected bunch has on a stable bunch as the oscillations of the injected bunch damp out. Turn-by-turn imaging of the synchrotron light uses a system of lenses and mirrors to image many turns of both the major and minor axis of a single bunch across the photocathode of a gateable camera. The bunch-by-bunch method is simpler: because of a focusing mirror used in porting the light from the ring, the synchrotron light from the orbiting electrons becomes an image at a certain distance from the mirror; and since the camera does not use a lens, the photocathode is set exactly at this image distance. Bunch-by-bunch profiling has shown that in the Low Energy Ring (LER) horizontal bunch size decreases along a train. Turn-by-turn profiling has been able to image 100 turns of a single bunch on one exposure of the camera. The turn-by-turn setup has also been able to image 50 turns of the minor axis showing part of the damping process of an oscillating injected charge during a LER fill. The goal is to image the damping of oscillations of injected charge for 100 turns of both the major and minor axis throughout the damping process during trickle injection. With some changes to the apparatus this goal is within reach and will make turn-by-turn imaging a very useful tool in beam diagnostics

  18. Experimental investigations on the influence of the photocathode laser pulse parameters on the electron bunch quality in an RF-photoelectron source

    International Nuclear Information System (INIS)

    Haenel, Marc

    2010-06-01

    Free Electron Lasers based on the SASE principle like the European XFEL require electron bunches having peak currents of several kiloamperes as well as very low transverse emittance. While high peak currents can be generated using longitudinal bunch compression techniques, the transverse emittance must have values as low as 1mmmrad already at the source. The development of electron sources fulfilling these demanding specifications is the goal of the Photo Injector Test Facility (PITZ) in DESY, Zeuthen site. The key component of a photoinjector is the electron gun cavity where the electrons bunches are generated and immediately accelerated. The extraction of the electrons is based on the photoelectric effect of the cathode which requires a laser system having special capabilities. In the first part of the thesis, measurements are presented which were performed to investigate whether the laser and the laser transport system fulfill these requirements. The second part of the thesis is dedicated to simulations as well as experimental studies on the impact of the temporal and spatial parameters of the laser pulses on the electron bunch quality. This influence is possible because the response time of the Cs 2 Te photocathode is short compared to the laser pulse duration. Based on these investigations, suggestions for improvements are given and tolerances for the laser pulse properties are defined. (orig.)

  19. Experimental investigations on the influence of the photocathode laser pulse parameters on the electron bunch quality in an RF-photoelectron source

    Energy Technology Data Exchange (ETDEWEB)

    Haenel, Marc

    2010-07-15

    Free Electron Lasers based on the SASE principle like the European XFEL require electron bunches having peak currents of several kiloamperes as well as very low transverse emittance. While high peak currents can be generated using longitudinal bunch compression techniques, the transverse emittance must have values as low as 1mmmrad already at the source. The development of electron sources fulfilling these demanding specifications is the goal of the Photo Injector Test Facility (PITZ) in DESY, Zeuthen site. The key component of a photoinjector is the electron gun cavity where the electrons bunches are generated and immediately accelerated. The extraction of the electrons is based on the photoelectric effect of the cathode which requires a laser system having special capabilities. In the first part of the thesis, measurements are presented which were performed to investigate whether the laser and the laser transport system fulfill these requirements. The second part of the thesis is dedicated to simulations as well as experimental studies on the impact of the temporal and spatial parameters of the laser pulses on the electron bunch quality. This influence is possible because the response time of the Cs{sub 2}Te photocathode is short compared to the laser pulse duration. Based on these investigations, suggestions for improvements are given and tolerances for the laser pulse properties are defined. (orig.)

  20. Refinements to longitudinal, single bunch, coherent instability theory

    Energy Technology Data Exchange (ETDEWEB)

    Koscielniak, S R

    1995-06-01

    For the case of a bunched beam confined to a quadratic potential well, we demonstrate the necessity for considering mode-coupling to correctly obtain the threshold current for the d.c. instability. Further we find the effect upon growth rate and coherent tune shift of evaluating the impedance at a complex frequency. For the case of a bunched beam confined to a cosine potential well, we give an exact analytic expression for the dispersion integral, and calculate (with no approximations), the stability diagram for the Robinson instability taking into account Landau damping. This paper comprises extracts from a lengthy internal report. (author). 2 refs., 4 figs.

  1. Evolving bunch and retardation in the impedance formalism

    International Nuclear Information System (INIS)

    Warnock, Robert; Venturini, Marco

    2003-01-01

    The usual expression for the longitudinal wake field in terms of the impedance is exact only for the model in which the source of the field is a rigid bunch. To account for a deforming bunch one has to invoke the complete impedance, a function of both wave number and frequency. A computation of the corresponding wake field would be expensive, since it would involve integrals over frequency and time in addition to the usual sum over wave number. We treat the problem of approximating this field in an example of current interest, the case of coherent synchrotron radiation (CSR) in the presence of shielding by the vacuum chamber

  2. THE RATE OF CURRENT CHANGE DURING A SHORT CIRCUIT IN THE POWER CIRCUITS OF THE ELECTRIC ROLLING STOCK WITH REGARD TO EDDY CURRENTS

    Directory of Open Access Journals (Sweden)

    L. V. Dubinets

    2010-04-01

    Full Text Available In the article the issue of influence of vortical currents on rate of change of short circuit current is considered, a mathematical model for the calculation of short circuit currents in the traction mode in the power circuits of DC electric rolling stock is presented, and the research results are given.

  3. An Electron Bunch Compression Scheme for a Superconducting Radio Frequency Linear Accelerator Driven Light Source

    Energy Technology Data Exchange (ETDEWEB)

    C. Tennant, S.V. Benson, D. Douglas, P. Evtushenko, R.A. Legg

    2011-09-01

    We describe an electron bunch compression scheme suitable for use in a light source driven by a superconducting radio frequency (SRF) linac. The key feature is the use of a recirculating linac to perform the initial bunch compression. Phasing of the second pass beam through the linac is chosen to de-chirp the electron bunch prior to acceleration to the final energy in an SRF linac ('afterburner'). The final bunch compression is then done at maximum energy. This scheme has the potential to circumvent some of the most technically challenging aspects of current longitudinal matches; namely transporting a fully compressed, high peak current electron bunch through an extended SRF environment, the need for a RF harmonic linearizer and the need for a laser heater. Additional benefits include a substantial savings in capital and operational costs by efficiently using the available SRF gradient.

  4. Nonlinear electrostatic emittance compensation in kA, fs electron bunches

    International Nuclear Information System (INIS)

    Geer, S.B. van der; Loos, M.J. de; Botman, J.I.M.; Luiten, O.J.; Wiel, M.J. van der

    2002-01-01

    Nonlinear space-charge effects play an important role in emittance growth in the production of kA electron bunches with a bunch length much smaller than the bunch diameter. We propose a scheme employing the radial third-order component of an electrostatic acceleration field, to fully compensate the nonlinear space-charge effects. This results in minimal transverse root-mean-square emittance. The principle is demonstrated using our design simulations of a device for the production of high-quality, high-current, subpicosecond electron bunches using electrostatic acceleration in a 1 GV/m field. Simulations using the GPT code produce a bunch of 100 pC and 73 fs full width at half maximum pulse width, resulting in a peak current of about 1.2 kA at an energy of 2 MeV. The compensation scheme reduces the root-mean-square emittance by 34% to 0.4π mm mrad

  5. 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.)

  6. Development of processing procedures for advanced silicon solar cells. [antireflection coatings and short circuit currents

    Science.gov (United States)

    Scott-Monck, J. A.; Stella, P. M.; Avery, J. E.

    1975-01-01

    Ten ohm-cm silicon solar cells, 0.2 mm thick, were produced with short circuit current efficiencies up to thirteen percent and using a combination of recent technical advances. The cells were fabricated in conventional and wraparound contact configurations. Improvement in cell collection efficiency from both the short and long wavelengths region of the solar spectrum was obtained by coupling a shallow junction and an optically transparent antireflection coating with back surface field technology. Both boron diffusion and aluminum alloying techniques were evaluated for forming back surface field cells. The latter method is less complicated and is compatible with wraparound cell processing.

  7. Shielded transient self-interaction of a bunch entering a circle from a straight path

    International Nuclear Information System (INIS)

    Li, R.; Bohn, C.L.; Bisognano, J.J.

    1997-01-01

    When a short (mm-length) bunch with high (nC-regime) charge is transported through a magnetic bending system, self-interaction via coherent synchrotron radiation (CSR) and space charge may alter the bunch dynamics significantly. The authors consider a Gaussian rigid-line-charge bunch following a straight-path trajectory into a circle, with the trajectory centered between two infinite, parallel, perfectly conducting plates. Transients associated with CSR and space charge generated from source particles both on the straight path and the circle are calculated, and their net effect on the radiated power is contrasted with that of shielded steady-state CSR

  8. Few femtosecond, few kilo-ampere electron bunch produced by a laser-plasma accelerator

    International Nuclear Information System (INIS)

    Lundh, O.; Lim, J.; Rechatin, C.; Ammoura, L.; Goddet, J.P.; Malka, V.; Faure, J.; Ben-Ismail, A.; Davoine, X.; Lefebvre, E.; Gallot, G.

    2011-01-01

    Particle accelerators driven by the interaction of ultra-intense and ultrashort laser pulses with a plasma can generate accelerating electric fields of several hundred giga-volts per meter and deliver high-quality electron beams with low energy spread, low emittance and up to 1 GeV peak energy. Moreover, it is expected they may soon be able to produce bursts of electrons shorter than those produced by conventional particle accelerators, down to femtosecond durations and less. Here we present wide-band spectral measurements of coherent transition radiation which we use for temporal characterization. Our analysis shows that the electron beam, produced using controlled optical injection, contains a temporal feature that can be identified as a 15 pC, 1.4-1.8 fs electron bunch (root mean square) leading to a peak current of 3-4 kA depending on the bunch shape. We anticipate that these results will have a strong impact on emerging applications such as short-pulse and short-wavelength radiation sources, and will benefit the realization of laboratory-scale free-electron lasers. (authors)

  9. Construction and performance of the magnetic bunch compressor for the THz facility at Chiang Mai University

    International Nuclear Information System (INIS)

    Saisut, J.; Kusoljariyakul, K.; Rimjaem, S.; Kangrang, N.; Wichaisirimongkol, P.; Thamboon, P.; Rhodes, M.W.; Thongbai, C.

    2011-01-01

    The Plasma and Beam Physics Research Facility at Chiang Mai University has established a THz facility to focus on the study of ultra-short electron pulses. Short electron bunches can be generated from a system that consists of a radio-frequency (RF) gun with a thermionic cathode, an alpha magnet as a magnetic bunch compressor, and a linear accelerator as a post-acceleration section. The alpha magnet is a conventional and simple instrument for low-energy electron bunch compression. With the alpha magnet constructed in-house, several hundred femtosecond electron bunches for THz radiation production can be generated from the thermionic RF gun. The construction and performance of the alpha magnet, as well as some experimental results, are presented in this paper.

  10. Construction and performance of the magnetic bunch compressor for the THz facility at Chiang Mai University

    Science.gov (United States)

    Saisut, J.; Kusoljariyakul, K.; Rimjaem, S.; Kangrang, N.; Wichaisirimongkol, P.; Thamboon, P.; Rhodes, M. W.; Thongbai, C.

    2011-05-01

    The Plasma and Beam Physics Research Facility at Chiang Mai University has established a THz facility to focus on the study of ultra-short electron pulses. Short electron bunches can be generated from a system that consists of a radio-frequency (RF) gun with a thermionic cathode, an alpha magnet as a magnetic bunch compressor, and a linear accelerator as a post-acceleration section. The alpha magnet is a conventional and simple instrument for low-energy electron bunch compression. With the alpha magnet constructed in-house, several hundred femtosecond electron bunches for THz radiation production can be generated from the thermionic RF gun. The construction and performance of the alpha magnet, as well as some experimental results, are presented in this paper.

  11. Multi-bunch Feedback Systems

    OpenAIRE

    Lonza, M.; Schmickler, H.

    2016-01-01

    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 importa...

  12. Coherent spontaneous radiation from highly bunched electron beams

    International Nuclear Information System (INIS)

    Berryman, K.W.; Crosson, E.R.; Ricci, K.N.

    1995-01-01

    Coherent spontaneous radiation has now been observed in several FELs, and is a subject of great importance to the design of self-amplified spontaneous emission (SASE) devices. We report observations of coherent spontaneous radiation in both FIREFLY and the mid-infrared FEL at the Stanford Picosecond FEL Center. Coherent emission has been observed at wavelengths as short as 5 microns, and enhancement over incoherent levels by as much as a factor of 4x10 4 has been observed at longer wavelengths. The latter behavior was observed at 45 microns in FIREFLY with short bunches produced by off-peak acceleration and dispersive compression. We present temporal measurements of the highly bunched electron distributions responsible for the large enhancements, using both transition radiation and energy-phase techniques

  13. Beam simulations with initial bunch noise in superconducting RF proton linacs

    CERN Document Server

    Tückmantel, J

    2010-01-01

    Circular machines are plagued by coupled bunch instabilities (CBI), driven by impedance peaks, where then all cavity higher order modes (HOMs) are possible drivers. Limiting the CBI growth rate is the fundamental reason that all superconducting rf cavities in circular machines are equipped with HOM dampers. The question arises if for similar reasons HOM damping would not be imperative also in high current superconducting rf proton linacs. Therefore we have simulated the longitudinal bunched beam dynamics in such machines, also including charge and position noise on the injected bunches. Simulations were executed for a generic linac with properties close to the planned SPL at CERN, SNS, or Project X at FNAL. It was found that with strong bunch noise and monopole HOMs with high Qext large beam scatter, possibly exceeding the admittance of a receiving machine, cannot be excluded. A transverse simulation shows similar requirements. Therefore including initial bunch noise in any beam dynamic study on superconducti...

  14. Increased short circuit current in an azafullerene-based organic solar cell.

    Science.gov (United States)

    Cambarau, Werther; Fritze, Urs F; Viterisi, Aurélien; Palomares, Emilio; von Delius, Max

    2015-01-21

    We report the synthesis of a solution-processable, dodecyloxyphenyl-substituted azafullerene monoadduct (DPC59N) and its application as electron acceptor in bulk heterojunction organic solar cells (BHJ-OSCs). Due to its relatively strong absorption of visible light, DPC59N outperforms PC60BM in respect to short circuit current (JSC) and external quantum efficiency (EQE) in blends with donor P3HT.

  15. Short (

    NARCIS (Netherlands)

    Telleman, Gerdien; den Hartog, Laurens

    2013-01-01

    Aim: This systematic review assessed the implant survival rate of short (<10 mm) dental implants installed in partially edentulous patients. A case report of a short implant in the posterior region have been added. Materials and methods: A search was conducted in the electronic databases of MEDLINE

  16. Theoretical models for describing longitudinal bunch compression in the neutralized drift compression experiment

    Directory of Open Access Journals (Sweden)

    Adam B. Sefkow

    2006-09-01

    Full Text Available Heavy ion drivers for warm dense matter and heavy ion fusion applications use intense charge bunches which must undergo transverse and longitudinal compression in order to meet the requisite high current densities and short pulse durations desired at the target. The neutralized drift compression experiment (NDCX at the Lawrence Berkeley National Laboratory is used to study the longitudinal neutralized drift compression of a space-charge-dominated ion beam, which occurs due to an imposed longitudinal velocity tilt and subsequent neutralization of the beam’s space charge by background plasma. Reduced theoretical models have been used in order to describe the realistic propagation of an intense charge bunch through the NDCX device. A warm-fluid model is presented as a tractable computational tool for investigating the nonideal effects associated with the experimental acceleration gap geometry and voltage waveform of the induction module, which acts as a means to pulse shape both the velocity and line density profiles. Self-similar drift compression solutions can be realized in order to transversely focus the entire charge bunch to the same focal plane in upcoming simultaneous transverse and longitudinal focusing experiments. A kinetic formalism based on the Vlasov equation has been employed in order to show that the peaks in the experimental current profiles are a result of the fact that only the central portion of the beam contributes effectively to the main compressed pulse. Significant portions of the charge bunch reside in the nonlinearly compressing part of the ion beam because of deviations between the experimental and ideal velocity tilts. Those regions form a pedestal of current around the central peak, thereby decreasing the amount of achievable longitudinal compression and increasing the pulse durations achieved at the focal plane. A hybrid fluid-Vlasov model which retains the advantages of both the fluid and kinetic approaches has been

  17. Methods for stable recording of short-circuit current in a Na+-transporting epithelium.

    Science.gov (United States)

    Gondzik, Veronika; Awayda, Mouhamed S

    2011-07-01

    Epithelial Na(+) transport as measured by a variety of techniques, including the short-circuit current technique, has been described to exhibit a "rundown" phenomenon. This phenomenon manifests as time-dependent decrease of current and resistance and precludes the ability to carry out prolonged experiments aimed at examining the regulation of this transport. We developed methods for prolonged stable recordings of epithelial Na(+) transport using modifications of the short-circuit current technique and commercial Ussing-type chambers. We utilize the polarized MDCK cell line expressing the epithelial Na(+) channel (ENaC) to describe these methods. Briefly, existing commercial chambers were modified to allow continuous flow of Ringer solution and precise control of such flow. Chamber manifolds and associated plumbing were modified to allow precise temperature clamp preventing temperature oscillations. Recording electrodes were modified to eliminate the use of KCl and prevent membrane depolarization from KCl leakage. Solutions utilized standard bicarbonate-based buffers, but all gasses were prehydrated to clamp buffer osmolarity. We demonstrate that these modifications result in measurements of current and resistance that are stable for at least 2 h. We further demonstrate that drifts in osmolarity similar to those obtained before prior to our modifications can lead to a decrease of current and resistance similar to those attributed to rundown.

  18. Femtosecond electron bunches from an RF-gun

    International Nuclear Information System (INIS)

    Rimjaem, Sakhorn; Farias, Ruy; Thongbai, Chitrlada; Vilaithong, Thiraphat; Wiedemann, Helmut

    2004-01-01

    Sub-picosecond electron pulses become a tool of increasing importance to study dynamics at an atomic level. Such electron pulses can be used directly or be converted into intense coherent far infrared radiation or equally short X-ray pulses. In principle, sub-picosecond electron pulses can be obtained in large, high-energy electron linear accelerator systems by repeatedly applying an energy slew and magnetic compression. Another process is the production of short electron pulses at low energies from an RF-gun with a thermionic cathode together with a bunch compressing α-magnet. In this paper, we present a systematic analysis of capabilities and limits of sub-picosecond electron pulses from such a source. We discuss particular parameter choices as well as the impact of geometric and electric specifications on the 6-dimensional phase space electron distribution. Numerical beam simulations with the computer code PARMELA are performed including effects and limitations due to space charge forces. While the production of femtosecond electron bunches is of primary concern, we also consider the preservation of such short bunches along a beam transport line

  19. 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.

  20. Theory of longitudinal instability for bunched electron and proton beams

    International Nuclear Information System (INIS)

    Ruggiero, A.G.

    1977-01-01

    A discussion is given of an original approach for the treatment of the longitudinal stability of high-intensity proton and electron bunches. The general analysis is divided in three steps. First, a search is made for a stationary bunch distribution which is matched to the external rf forces as well as to the current dependent induced fields. The existence of such distribution is questioned. Second, the stability of the stationary solution is checked by applying a small perturbation and observing whether this is initially damped or not. At this point a stability condition is derived in terms of current, surrounding impedance and bunch size. In the last step one should question what happens to the beam in case the stability condition is not satisfied. The problem here is the determination of the final bunch configuration. The originality of the approach stays in the combination of the three steps. All previous theories either consider only the first step or combine the second and third ones but disregard the first

  1. Association between Early Attention-Deficit/Hyperactivity Symptoms and Current Verbal and Visuo-Spatial Short-Term Memory

    Science.gov (United States)

    Gau, Susan Shur-Fen; Chiang, Huey-Ling

    2013-01-01

    Deficits in short-term memory are common in adolescents with attention-deficit/hyperactivity disorder (ADHD), but their current ADHD symptoms cannot well predict their short-term performance. Taking a developmental perspective, we wanted to clarify the association between ADHD symptoms at early childhood and short-term memory in late childhood and…

  2. An origin for short gamma-ray bursts unassociated with current star formation.

    Science.gov (United States)

    Barthelmy, S D; Chincarini, G; Burrows, D N; Gehrels, N; Covino, S; Moretti, A; Romano, P; O'Brien, P T; Sarazin, C L; Kouveliotou, C; Goad, M; Vaughan, S; Tagliaferri, G; Zhang, B; Antonelli, L A; Campana, S; Cummings, J R; D'Avanzo, P; Davies, M B; Giommi, P; Grupe, D; Kaneko, Y; Kennea, J A; King, A; Kobayashi, S; Melandri, A; Meszaros, P; Nousek, J A; Patel, S; Sakamoto, T; Wijers, R A M J

    2005-12-15

    Two short (gamma-ray bursts (GRBs) have recently been localized and fading afterglow counterparts detected. The combination of these two results left unclear the nature of the host galaxies of the bursts, because one was a star-forming dwarf, while the other was probably an elliptical galaxy. Here we report the X-ray localization of a short burst (GRB 050724) with unusual gamma-ray and X-ray properties. The X-ray afterglow lies off the centre of an elliptical galaxy at a redshift of z = 0.258 (ref. 5), coincident with the position determined by ground-based optical and radio observations. The low level of star formation typical for elliptical galaxies makes it unlikely that the burst originated in a supernova explosion. A supernova origin was also ruled out for GRB 050709 (refs 3, 31), even though that burst took place in a galaxy with current star formation. The isotropic energy for the short bursts is 2-3 orders of magnitude lower than that for the long bursts. Our results therefore suggest that an alternative source of bursts--the coalescence of binary systems of neutron stars or a neutron star-black hole pair--are the progenitors of short bursts.

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

    International Nuclear Information System (INIS)

    Steffen, B.R.

    2007-07-01

    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.)

  4. 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.)

  5. High ion charge states in a high-current, short-pulse, vacuum ARC ion sources

    International Nuclear Information System (INIS)

    Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

    1996-01-01

    Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1-4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several μs) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution

  6. High ion charge states in a high-current, short-pulse, vacuum arc ion source

    International Nuclear Information System (INIS)

    Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

    1995-09-01

    Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1--4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several micros) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution

  7. The effect of different solar simulators on the measurement of short-circuit current temperature coefficients

    Science.gov (United States)

    Curtis, H. B.; Hart, R. E., Jr.

    1982-01-01

    Gallium arsenide solar cells are considered for several high temperature missions in space. Both near-Sun and concentrator missions could involve cell temperatures on the order of 200 C. Performance measurements of cells at elevated temperatures are usually made using simulated sunlight and a matched reference cell. Due to the change in bandgap with increasing temperature at portions of the spectrum where considerable simulated irradiance is present, there are significant differences in measured short circuit current at elevated temperatures among different simulators. To illustrate this, both experimental and theoretical data are presented for gallium arsenide cells.

  8. Variations in the electrical short-circuit current decay for recombination lifetime and velocity measurements

    Science.gov (United States)

    Jung, Tae-Won; Lindholm, Fredrik A.; Neugroschel, Arnost

    1987-01-01

    An improved measurement system for electrical short-circuit current decay is presented that extends applicability of the method to silicon solar cells having an effective lifetime as low as 1 microsec. The system uses metal/oxide/semiconductor transistors as voltage-controlled switches. Advances in theory developed here increase precision and sensitivity in the determination of the minority-carrier recombination lifetime and recombination velocity. A variation of the method, which exploits measurements made on related back-surface field and back-ohmic contact devices, further improves precision and sensitivity. The improvements are illustrated by application to 15 different silicon solar cells.

  9. Femtosecond X-ray Pulses from a Spatially Chirped Electron Bunch in a SASE FEL

    Energy Technology Data Exchange (ETDEWEB)

    Emma, P.

    2003-01-14

    We propose a simple method to produce short x-ray pulses using a spatially chirped electron bunch in a SASE FEL. The spatial chirp is generated using an rf deflector which produces a transverse offset (in y and/or y') correlated with the longitudinal bunch position. Since the FEL gain is very sensitive to an initial offset in the transverse phase space at the entrance of the undulator, only a small portion of the electron bunch with relatively small transverse offset will interact significantly with the radiation, resulting in an x-ray pulse length much shorter than the electron bunch length. The x-ray pulse is also naturally phase locked to the rf deflector and so allows high precision timing synchronization. We discuss the generation and transport of such a spatially chirped electron beam and show that tens of femtosecond long pulse can be generated for the linac coherent light source (LCLS).

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

    International Nuclear Information System (INIS)

    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 μm 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 μsec macro-pulse is estimated to be about 480 sec. Simulations experimental setup and results will be discussed

  11. Anticrab cavities for the removal of spurious vertical bunch rotations caused by crab cavities

    Directory of Open Access Journals (Sweden)

    G. Burt

    2008-09-01

    Full Text Available Many particle accelerators are proposing the use of crab cavities to correct for accelerator crossing angles or for the production of short bunches in light sources. These cavities produce a rotation to the bunch in a well-defined polarization plane. If the plane of the rotation does not align with the horizontal axis of the accelerator, the bunch will receive a small amount of spurious vertical bunch rotation. For accelerators with small vertical beam sizes and large beam-beam effects, this can cause significant unwanted effects. In this paper we propose the use of a 2nd smaller crab cavity in the vertical plane in order to cancel this effect and investigate its use in numerical simulations.

  12. Observation of the non colliding bunch parameters evolution in the LHC

    CERN Document Server

    Trad, G

    2012-01-01

    On the 6th and the 7th of June 2011, the LHC was filled so to have twelve additional non-colliding bunches per ring. In this note a detailed observation of the bunch parameters (current, emittances and length) is presented, focusing on the differences in the behaviour between colliding and non-colliding bunches. Lifetimes for the residual gas interaction were estimated. Simulations were compared to the experimental data collected in the MD. Some conclusions are drawn and suggestions for future MD are discussed.

  13. TRANSVERSE MODES FOR FLAT INTER-BUNCH WAKES*

    CERN Document Server

    Burov, A

    2013-01-01

    If inter-bunch wake fields are flat, i.e. their variations over a bunch length can be neglected, all coherent modes have the same coupled-bunch structure, provided the bunches can be treated as identical by their inner qualities (train theorem). If a flat feedback is strong enough, the transverse modes are single-bunch, provided the inter-bunch wakes are also flat (damper theorem).

  14. 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 + ...

  15. 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

  16. Femtosecond single electron bunch generation by rotating longitudinal bunch phase space in magnetic field

    International Nuclear Information System (INIS)

    Yang, J.; Kondoh, T.; Kan, K.; Kozawa, T.; Yoshida, Y.; Tagawa, S.

    2006-01-01

    A femtosecond (fs) electron bunching was observed in a photoinjector with a magnetic compressor by rotating the bunch in longitudinal phase space. The bunch length was obtained by measuring Cherenkov radiation of the electron beam with a femtosecond streak camera technique. A single electron bunch with rms bunch length of 98 fs was observed for a 32 MeV electron beam at a charge of 0.17 nC. The relative energy spread and the normalized transverse emittance of the electron beam were 0.2% and 3.8 mm-mrad, respectively. The effect of space charge on the bunch compression was investigated experimentally for charges from 0.17 to 1.25 nC. The dependences of the relative energy spread and the normalized beam transverse emittance on the bunch charge were measured

  17. Spatially resolved determination of the short-circuit current density of silicon solar cells via lock-in thermography

    International Nuclear Information System (INIS)

    Fertig, Fabian; Greulich, Johannes; Rein, Stefan

    2014-01-01

    We present a spatially resolved method to determine the short-circuit current density of crystalline silicon solar cells by means of lock-in thermography. The method utilizes the property of crystalline silicon solar cells that the short-circuit current does not differ significantly from the illuminated current under moderate reverse bias. Since lock-in thermography images locally dissipated power density, this information is exploited to extract values of spatially resolved current density under short-circuit conditions. In order to obtain an accurate result, one or two illuminated lock-in thermography images and one dark lock-in thermography image need to be recorded. The method can be simplified in a way that only one image is required to generate a meaningful short-circuit current density map. The proposed method is theoretically motivated, and experimentally validated for monochromatic illumination in comparison to the reference method of light-beam induced current.

  18. Adrenomedullin increases the short-circuit current in the mouse seminal vesicle: actions on chloride secretion.

    Science.gov (United States)

    Liao, S B; Cheung, K H; O, W S; Tang, Fai

    2014-08-01

    Adrenomedullin (ADM) may regulate seminal vesicle fluid secretion, and this may affect sperm quality. In this study, we investigated the effect of ADM on chloride secretion in the mouse seminal vesicle. The presence of ADM in mouse seminal vesicle was confirmed using immunostaining, and the molecular species was determined using gel filtration chromatography coupled with enzyme-linked assay for ADM. The effects of ADM on chloride secretion were studied by short-circuit current technique in a whole-mount preparation of mouse seminal vesicle in an Ussing chamber. The effects of specific ADM and calcitonin gene-related peptide (CGRP) receptor antagonists were investigated. Whether the ADM effect depended on the cAMP- and/or calcium-activated chloride channel was also studied using specific chloride channel blockers. The results showed that ADM was present in seminal vesicle epithelial cells. The major molecular species was precursor in the mouse seminal vesicle. ADM increased short-circuit current through the calcium-activated chloride channel in mouse seminal vesicle, and CGRP receptor was involved. We conclude that ADM may regulate chloride and fluid secretion from the seminal vesicle, which may affect the composition of the seminal plasma bathing the sperm and, hence, fertility. © 2014 by the Society for the Study of Reproduction, Inc.

  19. Curvature radiation by bunches of particles

    International Nuclear Information System (INIS)

    Saggion, A.

    1975-01-01

    A bunch of relativistic particles moving on a curved trajectory is considered. The coherent emission of curvature radiation is described with particular regard to the role played by the 'shape' of the bunch as a function of its dimensions. It is found that the length of the bunch strongly affects the spectrum of the radiation emitted, with no effect on its polarization. For wavelengths shorter than the length of the bunch, the emitted intensity as a function of frequency shows recurrent maxima and minima, the height of the maxima being proportional to νsup(-5/3). The bunch dimensions perpendicular to the plane of the orbit affect both the spectral intensity and the polarization of the radiation. (orig./BJ) [de

  20. Feedback control of coupled-bunch instabilities

    International Nuclear Information System (INIS)

    Fox, J.D.; Eisen, N.; Hindi, H.; Linscott, I.; Oxoby, G.; Sapozhnikov, L.; Serio, M.

    1993-05-01

    The next generation of synchrotron light sources and particle accelerators will require active feedback systems to control multi-bunch instabilities. Stabilizing hundreds or thousands of potentially unstable modes in these accelerator designs presents many technical challenges. Feedback systems to stabilize coupled-bunch instabilities may be understood in the frequency domain (mode-based feedback) or in the time domain (bunch-by-bunch feedback). In both approaches an external amplifier system is used to create damping fields that prevent coupled-bunch oscillations from growing without bound. The system requirements for transverse (betatron) and longitudinal (synchrotron) feedback are presented, and possible implementation options developed. Feedback system designs based on digital signal-processing techniques are described. Experimental results are shown from a synchrotron oscillation damper in the SSRL/SLAC storage ring SPEAR that uses digital signal-processing techniques

  1. Measurements of impedances for determinating the minimum short-circuit current in main systems 500 V of underground mining establishments

    Energy Technology Data Exchange (ETDEWEB)

    Rittinghaus, D

    1981-09-01

    The complex short-circuit impedances of energized low-voltage main systems were measured with a double-bridge in underground mining operation. The magnitude of the short-circuit currents depends on these impedances. Customary calculations of such currents depend on empirical approximations. To verify the accuracy of these approximations, the measured impedances of 61 nodes in three different main systems were compared with the results of the calculations. The comparison made between the short-circuit currents determined by measurable quantities and the values calculated according to VDE 0118 shows that the stipulated coefficients for calculating the minimum short-circuit currents lie very far on the safe side. An amendment for calculating the short-circuit in accordance with VDE 0118 is therefore suggested.

  2. Preservation of low slice emittance in bunch compressors

    Directory of Open Access Journals (Sweden)

    S. Bettoni

    2016-03-01

    Full Text Available Minimizing the dilution of the electron beam emittance is crucial for the performance of accelerators, in particular for free electron laser facilities, where the length of the machine and the efficiency of the lasing process depend on it. Measurements performed at the SwissFEL Injector Test Facility revealed an increase in slice emittance after compressing the bunch even for moderate compression factors. The phenomenon was experimentally studied by characterizing the dependence of the effect on beam and machine parameters relevant for the bunch compression. The reproduction of these measurements in simulation required the use of a 3D beam dynamics model along the bunch compressor that includes coherent synchrotron radiation. Our investigations identified transverse effects, such as coherent synchrotron radiation and transverse space charge as the sources of the observed emittance dilution, excluding other effects, such as chromatic effects on single slices or spurious dispersion. We also present studies, both experimental and simulation based, on the effect of the optics mismatch of the slices on the variation of the slice emittance along the bunch. After a corresponding reoptimization of the beam optics in the test facility we reached slice emittances below 200 nm for the central slices along the longitudinal dimension with a moderate increase up to 300 nm in the head and tail for a compression factor of 7.5 and a bunch charge of 200 pC, equivalent to a final current of 150 A, at about 230 MeV energy.

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

    International Nuclear Information System (INIS)

    Bock, Marie Kristin

    2013-03-01

    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.

  4. 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.

  5. Bunch-motion feedback for B-factories

    International Nuclear Information System (INIS)

    Lambertson, G.R.

    1992-09-01

    The colliding electron and positron beams in a B-factory must have average current of one ampere or more to produce the required luminosity. The high current interacts with structures in the beam tube to drive strong coupled-bunch (c.b.) instabilities. To suppress these instabilities requires negative feedback of the bunch motions. Beam impedances arising from strong rf cavity modes should first be reduced to make the required feedback damping rate practical and the cost economical. In what follows, control of transverse motions will be discussed first, then longitudinal. We shall use the parameters of the 3.1 GeV ring of PEP-II to illustrate the general requirements

  6. A 40 MHz Bunch by Bunch Intensity Measurement for the CERN SPS and LHC

    CERN Document Server

    Jakob, H; Jones, R; Jensen, L

    2003-01-01

    A new acquisition system has been developed to allow the measurement of the individual intensity of each bunch in a 40MHz bunch train. Such a system will be used for the measurement of LHC type beams after extraction from the CERN-PS right through to the dump lines of the CERN-LHC. The method is based on integrating the analogue signal supplied by a Fast Beam Current Transformer at a frequency of 40MHz. This has been made possible with the use of a fast integration ASIC developed by the University of Clermont-Ferrand, France, for the LHC-b pre-shower detector. The output of the integrator is digitised using a 12-bit ADC and fed into a Digital Acquisition Board (DAB) that was originally developed by TRIUMF, Canada, for use in the LHC orbit system. A full system set-up was commissioned during 2002 in the CERN-SPS, and following its success will now be extended in 2003 to cover the PS to SPS transfer lines and the new TT40 LHC extraction channel.

  7. 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...... in a narrow bias current range. The analysis of the soliton modes provides an explanation of recent experimental observations....

  8. Wakefield excitation in plasma resonator by a sequence of relativistic electron bunches

    International Nuclear Information System (INIS)

    Kiselev, V.A.; Linnik, A.F.; Mirny, V.I.; Onishchenko, I.N.; Uskov, V.V.

    2008-01-01

    Wakefield excitation in a plasma resonator by a sequence of relativistic electron bunches with the purpose to increase excited field amplitude in comparison to waveguide case is experimentally investigated. A sequence of short electron bunches is produced by the linear resonant accelerator. Plasma resonator is formed at the beam-plasma discharge in rectangular metal waveguide filled with gas and closed by metal foil at entrance and movable short-circuited plunger at exit. Measurements of wakefield amplitude are performed showing considerably higher wakefield amplitude for resonator case

  9. Short fiber-reinforced composite restorations: A review of the current literature.

    Science.gov (United States)

    Garoushi, Sufyan; Gargoum, Ausama; Vallittu, Pekka K; Lassila, Lippo

    2018-02-25

    A newly-recommended method for restoring large cavities is the biomimetic approach of using short fiber-reinforced composite (SFRC) as dentine-replacing material. The aim of the current review was to present an overview of SFRC and to give the clinician a detailed understanding of this new material and treatment strategy based on available-literature review. A thorough literature search was done up to December 2017. The range of relevant publications was surveyed using PubMed and Google Scholar. From the search results, articles related to our search terms were only considered. The search terms used were "short fiber-reinforced composite", "everX posterior", and "fiber-reinforced composite restorations". Of the assessed articles selected (N = 70), most were laboratory-based research with various test specimen designs prepared according to the ISO standard or with extracted teeth; only four articles were clinical reports. A common finding was that by combining the SFRC as a bulk base with conventional composite, the load-bearing capacity and failure mode of the material combination were improved, as compared to plain conventional composite restoration. In the reviewed studies, the biomimetic restoration technique of using SFRC showed promising characteristics, and therefore, might be recommended as an alternative treatment option for large cavities. © 2018 John Wiley & Sons Australia, Ltd.

  10. Emittance control and RF bunch compression in the NSRRC photoinjector

    International Nuclear Information System (INIS)

    Lau, W.K.; Hung, S.B.; Lee, A.P.; Chou, C.S.; Huang, N.Y.

    2011-01-01

    The high-brightness photoinjector being constructed at the National Synchrotron Radiation Research Center is for testing new accelerator and light-source concepts. It is the so-called split photoinjector configuration in which a short solenoid magnet is used for emittance compensation. The UV-drive laser pulses are also shaped to produce uniform cylindrical bunches for further reduction of beam emittance. However, limited by the available power from our microwave power system, the nominal accelerating gradient in the S-band booster linac is set at 18 MV/m. A simulation study with PARMELA shows that the linac operating at this gradient fails to freeze the electron beam emittance at low value. A background solenoid magnetic field is applied for beam emittance control in the linac during acceleration. A satisfactory result that meets our preliminary goal has been achieved with the solenoid magnetic field strength at 0.1 T. RF bunch compression as a means to achieve the required beam brightness for high-gain free-electron laser experiments is also examined. The reduction of bunch length to a few hundred femtoseconds can be obtained.

  11. 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...

  12. [Materials/Biomaterials in Clinical Practice - a Short Review and Current Trends].

    Science.gov (United States)

    Bolle, T; Meyer, F; Walcher, F; Lohmann, C; Jockenhövel, S; Gries, T; Hoffmann, W

    2017-04-01

    Biomaterials play a major role in interventional medicine and surgery. However, the development of biomaterials is still in its early phases in spite of the huge progress made within the last decades. On the one hand, this is because our knowledge of the molecular and cellular processes associated with biomaterials is still increasing exponentially. On the other hand, a wide variety of advanced materials with highly interesting properties is being developed currently. This review provides a short introduction into the variety of materials in use as well as their application in interventional medicine and surgery. Also the importance of biomaterials for tissue engineering in the field of regenerative medicine and the functionalisation of biomaterials, including sterilisation methods are discussed. For the future, an even broader interdisciplinary scientific collaboration is necessary in order to develop novel biomaterials and facilitate their translation into clinical practice. Georg Thieme Verlag KG Stuttgart · New York.

  13. Short-circuit current improvement in thin cells with a gridded back contact

    Science.gov (United States)

    Giuliano, M.; Wohlgemuth, J.

    1980-01-01

    The use of gridded back contact on thin silicon solar cells 50 micrometers was investigated. An unexpected increase in short circuit current of almost 10 percent was experienced for 2 cm x 2 cm cells. Control cells with the standard continuous contact metallization were fabricated at the same time as the gridded back cells with all processes identical up to the formation of the back contact. The gridded back contact pattern was delineated by evaporation of Ti-Pd over a photo-resist mask applied to the back of the wafer; the Ti-Pd film on the controls was applied in the standard fashion in a continuous layer over the back of the cell. The Ti-Pd contacts were similarly applied to the front of the wafer, and the grid pattern on both sides of the cell was electroplated with 8-10 micrometers of silver.

  14. Short circuit current changes in electron irradiated GaAlAs/GaAs solar cells

    Science.gov (United States)

    Walker, G. H.; Conway, E. J.

    1978-01-01

    Heteroface p-GaAlAs/p-GaAs/n-GaAs solar cells with junction depths of 0.8, 1.5, and 4 microns were irradiated with 1 MeV electrons. The short-circuit current for the 4 micron junction depth cells is significantly reduced by the electron irradiation. Reduction of the junction depth to 1.5 microns improves the electron radiation resistance of the cells while further reduction of the junction depth to 0.8 microns improves the stability of the cells even more. Primary degradation is in the blue region of the spectrum. Considerable recovery of lost response is obtained by annealing the cells at 200 C. Computer modeling shows that the degradation is caused primarily by a reduction in the minority carrier diffusion length in the p-GaAs.

  15. Several problems of algorithmization in integrated computation programs on third generation computers for short circuit currents in complex power networks

    Energy Technology Data Exchange (ETDEWEB)

    Krylov, V.A.; Pisarenko, V.P.

    1982-01-01

    Methods of modeling complex power networks with short circuits in the networks are described. The methods are implemented in integrated computation programs for short circuit currents and equivalents in electrical networks with a large number of branch points (up to 1000) on a computer with a limited on line memory capacity (M equals 4030 for the computer).

  16. The 'Fresh-Bunch' technique in FELs

    International Nuclear Information System (INIS)

    Ben-Zvi, I.; Yang, K.M.; Yu, L.H.

    1991-01-01

    The 'Fresh Bunch' technique is being proposed as a method of increasing the gain and power of FEL amplifiers in which the length of the optical radiation pulse is shorter than the length of the electron bunch. In multi-stage FEL, electron beam energy spread is increased by the FEL interaction in the early stages. In the 'Fresh Bunch' technique, the low energy spread of the electron beam is recovered by shifting the radiation pulse to an undisturbed part of the electron bunch, thus improving the gain and trapping fraction in later stages. A test case for the application of the Fresh Bunch method is demonstrated by numerical simulation. In this particular example we examine a subharmonically seeded VUV Free-Electron Laser. We begin with the generation of harmonic radiation, which takes place over one part of the electron bunch. Then the radiation is shifted by means of a strong dispersive section to a fresh part of the bunch for exponential amplification and tapered wiggler amplification. By starting over with a new ensemble of electrons, the energy spread introduced by the bunching in the fundamental is removed, leading to an increased gain. Furthermore, it is possible to use a much stronger seed in the fundamental without incurring the penalty of a large energy spread later on. We note that more than a single application of the 'Fresh Bunch' method may be done in a single FEL multiplier-amplifier. Thus x-ray wavelengths may be reached by successive multiplication in a chain of FEL amplifiers starting from a tunable seed laser. 5 refs., 2 figs., 2 tabs

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

    Energy Technology Data Exchange (ETDEWEB)

    Kirby, Neil; /SLAC

    2009-10-30

    Plasma-based accelerators use the propagation of a drive bunch through plasma to create large electric fields. Recent plasma wakefield accelerator (PWFA) experiments, carried out at the Stanford Linear Accelerator Center (SLAC), successfully doubled the energy for some of the 42 GeV drive bunch electrons in less than a meter; this feat would have required 3 km in the SLAC linac. This dissertation covers one phenomenon associated with the PWFA, electron trapping. Recently it was shown that PWFAs, operated in the nonlinear bubble regime, can trap electrons that are released by ionization inside the plasma wake and accelerate them to high energies. These trapped electrons occupy and can degrade the accelerating portion of the plasma wake, so it is important to understand their origins and how to remove them. Here, the onset of electron trapping is connected to the drive bunch properties. Additionally, the trapped electron bunches are observed with normalized transverse emittance divided by peak current, {epsilon}{sub N,x}/I{sub t}, below the level of 0.2 {micro}m/kA. A theoretical model of the trapped electron emittance, developed here, indicates that the emittance scales inversely with the square root of the plasma density in the non-linear 'bubble' regime of the PWFA. This model and simulations indicate that the observed values of {epsilon}{sub N,x}/I{sub t} result from multi-GeV trapped electron bunches with emittances of a few {micro}m and multi-kA peak currents. These properties make the trapped electrons a possible particle source for next generation light sources. This dissertation is organized as follows. The first chapter is an overview of the PWFA, which includes a review of the accelerating and focusing fields and a survey of the remaining issues for a plasma-based particle collider. Then, the second chapter examines the physics of electron trapping in the PWFA. The third chapter uses theory and simulations to analyze the properties of the trapped

  18. Maximizing the short circuit current of organic solar cells by partial decoupling of electrical and optical properties

    Science.gov (United States)

    Qarony, Wayesh; Hossain, Mohammad I.; Jovanov, Vladislav; Knipp, Dietmar; Tsang, Yuen Hong

    2018-03-01

    The partial decoupling of electronic and optical properties of organic solar cells allows for realizing solar cells with increased short circuit current and energy conversion efficiency. The proposed device consists of an organic solar cell conformally prepared on the surface of an array of single and double textured pyramids. The device geometry allows for increasing the optical thickness of the organic solar cell, while the electrical thickness is equal to the nominal thickness of the solar cell. By increasing the optical thickness of the solar cell, the short circuit current is distinctly increased. The quantum efficiency and short circuit current are determined using finite-difference time-domain simulations of the 3D solar cell structure. The influence of different solar cell designs on the quantum efficiency and short circuit current is discussed and optimal device dimensions are proposed.

  19. Sensitive beam-bunch phase detector

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, S; Shepard, K W

    1984-11-15

    A sensitive heavy-ion beam-bunch phase detector has been developed by first examining the relationship between the sensitivity of an rf resonant cavity as a particle bunch detector and the shunt impedance of the same cavity as an accelerating structure. Then the various high shunt impedance rf cavities previously developed for accelerating heavy ions were evaluated for use as bunch detectors. A spiral-loaded geometry was chosen, built, and tested with beam. The sensitivity obtained, 14 V per electrical nA of beam, is a factor 3 higher than previously reported. (orig.).

  20. Sensitive beam-bunch phase detector

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, S; Shepard, K W [Argonne National Lab., IL (USA). Physics Div.

    1984-11-15

    A sensitive heavy-ion beam-bunch phase detector has been developed by first examining the relationship between the sensitivity of an RF resonant cavity as a particle bunch detector and the shunt impedance of the same cavity as an accelerating structure. Then the various high shunt impedance RF cavities previously developed for accelerating heavy ions were evaluated for use as bunch detectors. A spiral-loaded geometry was chosen, built, and tested with beam. The sensitivity obtained, 14 ..mu.. V per electrical nA of beam, is a factor 3 higher than previously reported.

  1. Down sampled signal processing for a B Factory bunch-by-bunch feedback system

    International Nuclear Information System (INIS)

    Hindi, H.; Hosseini, W.; Briggs, D.; Fox, J.; Hutton, A.

    1992-03-01

    A bunch-by-bunch feedback scheme is studied for damping coupled bunch synchrotron oscillations in the proposed PEP II B Factory. The quasi-linear feedback systems design incorporates a phase detector to provide a quantized measure of bunch phase, digital signal processing to compute an error correction signal and a kicker system to correct the energy of the bunches. A farm of digital processors, operating in parallel, is proposed to compute correction signals for the 1658 bunches of the B Factory. This paper studies the use of down sampled processing to reduce the computational complexity of the feedback system. We present simulation results showing the effect of down sampling on beam dynamics. Results show that down sampled processing can reduce the scale of the processing task by a factor of 10

  2. Longitudinal bunch deformation of a multi-bunched beam in the TRISTAN Accumulation Ring

    International Nuclear Information System (INIS)

    Obina, T.; Satoh, K.; Kasuga, T.; Funakoshi, Y.; Tobiyama, M.

    1997-01-01

    A remarkable bunch deformation has been observed in the TRISTAN Accumulation Ring (AR) during multi-bunch operations. When two bunches that have different populations are stored in the ring, the bunch length of the weaker bunch is longer than that of the stronger one. The phenomenon can be explained as an effect of wake fields due to higher-order modes (HOMs) of accelerating cavities. We tried to find out the frequency of the mode and the strength of the wake field, and introduced a new technique called a test bunch measurement. The estimated field strength from the experiment shows a reasonable agreement with the calculation of HOM impedance. copyright 1997 American Institute of Physics

  3. Measurements of Compression and Emittance Growth after the First LCLS Bunch Compressor Chicane

    International Nuclear Information System (INIS)

    Emma, P.

    2007-01-01

    The Linac Coherent Light Source (LCLS) is a SASE xray free-electron laser project presently under construction at SLAC. The injector section from RF photocathode gun through first bunch compressor chicane was installed during the fall of 2006. The first bunch compressor is located at 250 MeV and nominally compresses a 1-nC electron bunch from an rms length of about 1 mm to 0.2 mm. Transverse phase space and bunch length diagnostics are located immediately after the chicane. We present preliminary measurements and simulations of the longitudinal and transverse phase space after the chicane in various beam conditions, including extreme compression with micron-scale current spikes

  4. Microbial Production of Short Chain Fatty Acids from Lignocellulosic Biomass: Current Processes and Market

    Directory of Open Access Journals (Sweden)

    Ivan Baumann

    2016-01-01

    Full Text Available Biological production of organic acids from conversion of biomass derivatives has received increased attention among scientists and engineers and in business because of the attractive properties such as renewability, sustainability, degradability, and versatility. The aim of the present review is to summarize recent research and development of short chain fatty acids production by anaerobic fermentation of nonfood biomass and to evaluate the status and outlook for a sustainable industrial production of such biochemicals. Volatile fatty acids (VFAs such as acetic acid, propionic acid, and butyric acid have many industrial applications and are currently of global economic interest. The focus is mainly on the utilization of pretreated lignocellulosic plant biomass as substrate (the carbohydrate route and development of the bacteria and processes that lead to a high and economically feasible production of VFA. The current and developing market for VFA is analyzed focusing on production, prices, and forecasts along with a presentation of the biotechnology companies operating in the market for sustainable biochemicals. Finally, perspectives on taking sustainable product of biochemicals from promise to market introduction are reviewed.

  5. Optical effects of shadow masks on short circuit current of organic photovoltaic devices.

    Science.gov (United States)

    Lin, Chi-Feng; Lin, Bing-Hong; Liu, Shun-Wei; Hsu, Wei-Feng; Zhang, Mi; Chiu, Tien-Lung; Wei, Mau-Kuo; Lee, Jiun-Haw

    2012-03-21

    In this paper, we have employed different shadow masks attached on top of organic photovoltaic (OPV) devices to study the optical effects of the former on the short circuit current (J(SC)). To rule out possible lateral electrical conduction and simplify the optical effects inside the device, a small-molecular heterojunction OPV device with a clear donor/acceptor interface was employed with a hole extraction layer exhibiting high resistance intentionally. Careful calibration with a shadow mask was employed. By attaching two layers of opaque masks in combination with a suitable holder design to shield the light from the edges and backside, the value of J(SC) approached that of the dark current, even under 1-sun radiation. With different illumination areas, we found that the photons illuminating the non-active region of the device contributed to 40% of the J(SC) by optical effect within the width of about 1 mm around the active region. When illuminating the non-active area with 12 mm to the active area, a 5.6 times improvement in the J(SC) was observed when the incident angle was 75°. With the introduction of a microstructured film onto the OPV device and an increase in the reflection from the non-active region, a 15% enhancement of the J(SC) compared to the control device was achieved.

  6. Operational performance of a bunch by bunch digital damper in the Fermilab Main Injector

    International Nuclear Information System (INIS)

    Adamson, P.; Ashmanskas, W.J.; Foster, G.W.; Hansen, S.; Marchionni, A.; Nicklaus, D.; Semenov, A.; Wildman, D.; Kang, H.

    2005-01-01

    We have implemented a transverse and longitudinal bunch by bunch digital damper system in the Fermilab Main Injector, using a single digital board for all 3 coordinates. The system has been commissioned over the last year, and is now operational in all MI cycles, damping beam bunched at both 53MHz and 2.5MHz. We describe the performance of this system both for collider operations and high-intensity running for the NuMI project

  7. Observations of bunch-by-bunch losses in the 2010 LHC proton physics operation

    CERN Document Server

    Papotti, G

    2011-01-01

    This document summarizes the bunch-by-bunch loss observations carried out during the 2010 proton physics run at the LHC. These observations proved beneficial to the improvement of operations, in particular in the early days of nominal intensity per bunch operation: then the plots initiated the removal of the tune split and motivated the modification of a filling scheme to remove parasitic encounters that heightened the losses on selected bunches. Along with plots from sample physics fills, summary plots for the year are shown. The colour coding is always chosen so to highlight the dependence of the losses on the filling scheme.

  8. Bunch-by-bunch longitudinal feedback system for PEP-II

    International Nuclear Information System (INIS)

    Oxoby, G.; Claus, R.; Fox, J.

    1994-06-01

    This paper describes the implementation of the bunch-by-bunch longitudinal feedback system for the PEP-II B Factory. Bunch spacing down to 2 ns is achieved using 500 Megasamples per second A/D and D/A converters, and AT ampersand T 1610 Digital Signal Processors are integrated to run a downsampled feedback algorithm for each bunch in parallel. This general purpose programmable system, packaged in VXI and VME, is modular and scalable to offer portability to other accelerator rings. The control and monitoring hardware and software architecture have been developed to provide ease of operation as well as diagnostic tools for machine physics

  9. Considerations of bunch-spacing options for multi-bunch operation of the Tevatron Collider

    International Nuclear Information System (INIS)

    Dugan, G.

    1989-01-01

    This discussion will consider a number of points relevant to limitations, advantages and disadvantages of various arrangements of bunches in the Tevatron proton-antiproton collider. The considerations discussed here will be limited to: (a) bunch spacing symmetry and relation to the relative luminosity at B0 and D0 and the beam-beam interaction with separated beams; (b) bunch spacing constraints imposed by Main Ring RF coalescing and the optics of beam separation at B0 and D0; and (c) bunch spacing constraints imposed by injection and abort kicker timing requirements, and by the Antiproton Source RF unstacking process. 20 figs., 17 tabs

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

    International Nuclear Information System (INIS)

    Rui Li

    2008-01-01

    Within the realm of classical electrodynamics, 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. As an application of this canonical formulation, in this paper, for an electron distribution moving ultrarelativistically in a bending system, the dynamics of the particles in the distribution is derived from the Hamiltonian of the particles 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. Our study demonstrates clearly the time delay (or retardation) of the behavior of the effective longitudinal CSR force on a bunch in responding to the change of the bunch length in a magnetic bend. Our result also shows that the effective longitudinal CSR force for a bunch under full compression can have sensitive dependence on the transverse position of the test particle in the bunch for certain parameter regimes

  11. High short-circuit current density CdTe solar cells using all-electrodeposited semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Echendu, O.K., E-mail: oechendu@yahoo.com; Fauzi, F.; Weerasinghe, A.R.; Dharmadasa, I.M.

    2014-04-01

    CdS/CdTe and ZnS/CdTe n–n heterojunction solar cells have been fabricated using all-electrodeposited semiconductors. The best devices show remarkable high short-circuit current densities of 38.5 mAcm{sup −2} and 47.8 mAcm{sup −2}, open-circuit voltages of 630 mV and 646 mV and conversion efficiencies of 8.0% and 12.0% respectively. The major strength of these device structures lies in the combination of n–n heterojunction with a large Schottky barrier at the n-CdTe/metal back contact which provides the required band bending for the separation of photo-generated charge carriers. This is in addition to the use of a high quality n-type CdTe absorber layer with high electron mobility. The potential barrier heights estimated for these devices from the current–voltage characteristics exceed 1.09 eV and 1.13 eV for CdS/CdTe and ZnS/CdTe cells respectively. The diode rectification factors of both devices are in excess of four orders of magnitude with reverse saturation current densities of 1.0 × 10{sup −7} Acm{sup −2} and 4.0 × 10{sup −7} Acm{sup −2} respectively. These all-electrodeposited solar cell device structures are currently being studied and developed as an alternative to the well-known p–n junction structures which utilise chemical bath-deposited CdS. The preliminary material growth, device fabrication and assessment results are presented in this paper. - Highlights: • Two-electrode deposition. • High J{sub sc} Schottky barrier solar cells. • CdCl{sub 2} + CdF{sub 2} treatment.

  12. 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.

  13. Single bunched beam generation without subharmonic prebuncher

    International Nuclear Information System (INIS)

    Kobayashi, T.; Tagawa, S.

    1995-01-01

    The intensity of the accelerated single bunched electron beam depends on the performance of the electron gun and the fast cathode pulser. The electron beam is emitted by a Y-796 cathode assembly with a cathode of 2 cm 2 (8 A/cm 2 ), and an extracted voltage of 90 kV. The maximum charge of the single bunched beam was attained at 1.5 nC/pulse using SHB. Recently, a single bunched beam has been generated by an ultrafast cathode pulser (rise and fall time <100 ps pulse height -2 kV at 50 Ω) without SHB. The charge of the accelerated electron beam is about 40 pC/pulse (pulse width <10 ps) without the production of a satellite beam. This result show that a single bunched beam can be produced by the linear accelerator without SHB. ((orig.))

  14. CERN: The best of the bunch

    Energy Technology Data Exchange (ETDEWEB)

    Gagliardi, F.

    1992-10-15

    As other factors governing the electron-positron collision rate in CERN's LEP 27-kilometre storage ring reach their limit, one way of coaxing the collision rate higher is to increase the number of bunches stored in the ring.

  15. Three-Phase Short-Circuit Current Calculation of Power Systems with High Penetration of VSC-Based Renewable Energy

    Directory of Open Access Journals (Sweden)

    Niancheng Zhou

    2018-03-01

    Full Text Available Short-circuit current level of power grid will be increased with high penetration of VSC-based renewable energy, and a strong coupling between transient fault process and control strategy will change the fault features. The full current expression of VSC-based renewable energy was obtained according to transient characteristics of short-circuit current. Furtherly, by analyzing the closed-loop transfer function model of controller and current source characteristics presented in steady state during a fault, equivalent circuits of VSC-based renewable energy of fault transient state and steady state were proposed, respectively. Then the correctness of the theory was verified by experimental tests. In addition, for power grid with VSC-based renewable energy, superposition theorem was used to calculate AC component and DC component of short-circuit current, respectively, then the peak value of short-circuit current was evaluated effectively. The calculated results could be used for grid planning and design, short-circuit current management as well as adjustment of relay protection. Based on comparing calculation and simulation results of 6-node 500 kV Huainan power grid and 35-node 220 kV Huaisu power grid, the effectiveness of the proposed method was verified.

  16. 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.

  17. Two-nucleon electromagnetic current in chiral effective field theory: One-pion exchange and short-range contributions

    International Nuclear Information System (INIS)

    Koelling, S.; Epelbaum, E.; Krebs, H.; Meissner, U.-G.

    2011-01-01

    We derive the leading one-loop contribution to the one-pion exchange and short-range two-nucleon electromagnetic current operator in the framework of chiral effective field theory. The derivation is carried out using the method of unitary transformation. Explicit results for the current and charge densities are given in momentum and coordinate space.

  18. An alternative explanation for the occurrence of short circuit current increases in the small intestine following challenge by bacterial enterotoxins.

    Science.gov (United States)

    Lucas, M L

    2013-10-01

    Secretory diarrhoeal disease due to enterotoxins is thought to arise from the enhancement to pathologically high rates of normally occurring chloride ion and therefore fluid secretion from enterocytes. In support of this concept, many enterotoxins increase intestinal short-circuit current, regarded now as faithfully reflecting the increased chloride ion secretion. Contradicting this assumption, STa reduces absorption but does not cause secretion in vivo although short-circuit current is increased in vitro. There is therefore a mismatch between an assumed enterocyte mediated secretory event that should but does not cause net fluid secretion and an undoubtedly increased short-circuit current. It is proposed here that short-circuit current increases are not themselves secretory events but result from interrupted fluid absorption. A noteworthy feature of compounds that inhibit the increase in short-circuit current is that the majority are vasoactive, neuroactive or both. In general, vasodilator substances increase current. An alternative hypothesis for the origin of short-circuit current increases is that these result from reflex induction of electrogenic fluid absorption. This reflex enhances a compensatory response that is also present at a cellular level. An intestinal reflex is therefore proposed by which decreases in interstitial and intravascular volume or pressure within the intestine initiate an electrogenic fluid absorption mechanism that compensates for the loss of electrically neutral fluid absorption. This hypothesis would explain the apparently complex pharmacology of short-circuit current increases since many depressor substances have receptors in common with enterocytes and enteric nerves. The proposed alternative view of the origin of short-circuit current increases assumes that these do not represent chloride secretion from the enterocytes. This view may therefore aid the successful development of anti-diarrhoeal drugs to overcome a major cause of

  19. Dissipative NEGF methodology to treat short range Coulomb interaction: Current through a 1D nanostructure.

    Science.gov (United States)

    Martinez, Antonio; Barker, John R; Di Prieto, Riccardo

    2018-06-13

    A methodology describing Coulomb blockade in the Non-equilibrium Green Function formalism is presented. We carried out ballistic and dissipative simulations through a 1D quantum dot using an Einstein phonon model. Inelastic phonons with different energies have been considered. The methodology incorporates the short-range Coulomb interaction between two electrons through the use of a two-particle Green's function. Unlike previous work, the quantum dot has spatial resolution i.e. it is not just parameterized by the energy level and coupling constants of the dot. Our method intends to describe the effect of electron localization while maintaining an open boundary or extended wave function. The formalism conserves the current through the nanostructure. A simple 1D model is used to explain the increase of mobility in semi-crystalline polymers as a function of the electron concentration. The mechanism suggested is based on the lifting of energy levels into the transmission window as a result of the local electron-electron repulsion inside a crystalline domain. The results are aligned with recent experimental findings. Finally, as a proof of concept, we present a simulation of a low temperature resonant structure showing the stability diagram in the Coulomb blockade regime. . © 2018 IOP Publishing Ltd.

  20. Investigation of the extraction of short diffusion lengths from simulated electron-beam induced current

    Energy Technology Data Exchange (ETDEWEB)

    Wee, D.; Parish, G.; Nener, B. [Microelectronics Research Group, The University of Western Australia, 35 Stirling Highway, 6009 Crawley (Perth) (Australia)

    2010-10-15

    This paper reports on the investigations via 2-D simulation into the accuracy of diffusion length extraction from scanning electron-beam induced current measurements when the diffusion length, L is very short. L is extracted by using the direct method proposed by Chan et al.[1] and later refined by Kurniawan and Ong[2] to take finite junction depth into account. The 2-D simulations were undertaken using Synopsys {sup registered} Sentaurus TCAD and a realistic electron-hole pair generation volume was created using CASINO v2.42[3], a Monte Carlo Scanning Electron Microscope interaction simulation software, and imported into Sentaurus. The voltage and diameter of the electron beam and diffusion length and surface recombination velocity of the semiconductor materials were varied in the simulations to determine the errors in the diffusion length extracted from the EBIC signals as a function of these parameters. The results of the simulation show that the accuracy of the method proposed in[1] is reasonably accurate and that the beam voltage and spot size do not have significant effects on the accuracy (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Investigation of the extraction of short diffusion lengths from simulated electron-beam induced current

    International Nuclear Information System (INIS)

    Wee, D.; Parish, G.; Nener, B.

    2010-01-01

    This paper reports on the investigations via 2-D simulation into the accuracy of diffusion length extraction from scanning electron-beam induced current measurements when the diffusion length, L is very short. L is extracted by using the direct method proposed by Chan et al.[1] and later refined by Kurniawan and Ong[2] to take finite junction depth into account. The 2-D simulations were undertaken using Synopsys registered Sentaurus TCAD and a realistic electron-hole pair generation volume was created using CASINO v2.42[3], a Monte Carlo Scanning Electron Microscope interaction simulation software, and imported into Sentaurus. The voltage and diameter of the electron beam and diffusion length and surface recombination velocity of the semiconductor materials were varied in the simulations to determine the errors in the diffusion length extracted from the EBIC signals as a function of these parameters. The results of the simulation show that the accuracy of the method proposed in[1] is reasonably accurate and that the beam voltage and spot size do not have significant effects on the accuracy (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Solar Cell Short Circuit Current Errors and Uncertainties During High Altitude Calibrations

    Science.gov (United States)

    Snyder, David D.

    2012-01-01

    High altitude balloon based facilities can make solar cell calibration measurements above 99.5% of the atmosphere to use for adjusting laboratory solar simulators. While close to on-orbit illumination, the small attenuation to the spectra may result in under measurements of solar cell parameters. Variations of stratospheric weather, may produce flight-to-flight measurement variations. To support the NSCAP effort, this work quantifies some of the effects on solar cell short circuit current (Isc) measurements on triple junction sub-cells. This work looks at several types of high altitude methods, direct high altitude meas urements near 120 kft, and lower stratospheric Langley plots from aircraft. It also looks at Langley extrapolation from altitudes above most of the ozone, for potential small balloon payloads. A convolution of the sub-cell spectral response with the standard solar spectrum modified by several absorption processes is used to determine the relative change from AMO, lscllsc(AMO). Rayleigh scattering, molecular scatterin g from uniformly mixed gases, Ozone, and water vapor, are included in this analysis. A range of atmosph eric pressures are examined, from 0. 05 to 0.25 Atm to cover the range of atmospheric altitudes where solar cell calibrations a reperformed. Generally these errors and uncertainties are less than 0.2%

  3. Temporal characterization of ultrashort linearly chirped electron bunches generated from a laser wakefield accelerator

    Directory of Open Access Journals (Sweden)

    C. J. Zhang

    2016-06-01

    Full Text Available A new method for diagnosing the temporal characteristics of ultrashort electron bunches with linear energy chirp generated from a laser wakefield accelerator is described. When the ionization-injected bunch interacts with the back of the drive laser, it is deflected and stretched along the direction of the electric field of the laser. Upon exiting the plasma, if the bunch goes through a narrow slit in front of the dipole magnet that disperses the electrons in the plane of the laser polarization, it can form a series of bunchlets that have different energies but are separated by half a laser wavelength. Since only the electrons that are undeflected by the laser go through the slit, the energy spectrum of the bunch is modulated. By analyzing the modulated energy spectrum, the shots where the bunch has a linear energy chirp can be recognized. Consequently, the energy chirp and beam current profile of those bunches can be reconstructed. This method is demonstrated through particle-in-cell simulations and experiment.

  4. Association between early attention-deficit/hyperactivity symptoms and current verbal and visuo-spatial short-term memory.

    Science.gov (United States)

    Gau, Susan Shur-Fen; Chiang, Huey-Ling

    2013-01-01

    Deficits in short-term memory are common in adolescents with attention-deficit/hyperactivity disorder (ADHD), but their current ADHD symptoms cannot well predict their short-term performance. Taking a developmental perspective, we wanted to clarify the association between ADHD symptoms at early childhood and short-term memory in late childhood and adolescence. The participants included 401 patients with a clinical diagnosis of DSM-IV ADHD, 213 siblings, and 176 unaffected controls aged 8-17 years (mean age, 12.02 ± 2.24). All participants and their mothers were interviewed using the Chinese Kiddie Epidemiologic version of the Schedule for Affective Disorders and Schizophrenia to obtain information about ADHD symptoms and other psychiatric disorders retrospectively, at an earlier age first, then currently. The participants were assessed with the Wechsler Intelligence Scale for Children--3rd edition, including Digit Span, and the Spatial working memory task of the Cambridge Neuropsychological Test Automated Battery. Multi-level regression models were used for data analysis. Although crude analyses revealed that inattention, hyperactivity, and impulsivity symptoms significantly predicted deficits in short-term memory, only inattention symptoms had significant effects (all pshort-term memory at the current assessment. Therefore, our findings suggest that earlier inattention symptoms are associated with impaired verbal and visuo-spatial short-term memory at a later development stage. Impaired short-term memory in adolescence can be detected earlier by screening for the severity of inattention in childhood. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. The Effect of Current-Limiting Reactors on the Tripping of Short Circuits in High-Voltage Electrical Equipment

    International Nuclear Information System (INIS)

    Volkov, M. S.; Gusev, Yu. P.; Monakov, Yu. V.; Cho, Gvan Chun

    2016-01-01

    The insertion of current-limiting reactors into electrical equipment operating at a voltage of 110 and 220 kV produces a change in the parameters of the transient recovery voltages at the contacts of the circuit breakers for disconnecting short circuits, which could be the reason for the increase in the duration of the short circuit, damage to the electrical equipment and losses in the power system. The results of mathematical modeling of the transients, caused by tripping of the short circuit in a reactive electric power transmission line are presented, and data are given on the negative effect of a current-limiting resistor on the rate of increase and peak value of the transient recovery voltages. Methods of ensuring the standard requirements imposed on the parameters of the transient recovery voltages when using current-limiting reactors in the high-voltage electrical equipment of power plants and substations are proposed and analyzed

  6. Vasotocin- and mesotocin-induced increases in short-circuit current across tree frog skin.

    Science.gov (United States)

    Takada, Makoto; Fujimaki-Aoba, Kayo; Hokari, Shigeru

    2011-02-01

    In adult amphibian skin, Na(+) crosses from outside to inside. This Na(+) transport can be measured as the amiloride-blockable short-circuit current (SCC) across the skin. We investigated the effects of arginine vasotocin (AVT) and mesotocin (MT), and those of antagonists of the vasopressin and oxytocin receptors, on the SCC across Hyla japonica skin. (1) Both AVT (100 pmol/L or more) and MT (1 nmol/L or more) increased the SCC. (2) The AVT- and MT-induced increases in SCC recovered with time (downregulation). (3) These AVT/MT-induced effects were blocked by application of OPC-31260 (vasopressin V(2)-receptor antagonist). (4) The OPC-31260 concentration needed to block the AVT-induced response was lower upon post-application (after application of agonist) than upon pre-application (before application of agonist), suggesting the number of receptors may have decreased after AVT application. (5) Upon repeated application of AVT (100 pmol/L), the induced SCC increase did not differ significantly between the 1st and 2nd applications. (6) The time to reach the half-maximum value of the AVT-induced or MT-induced increase in SCC was not significantly different between washout and post-application of OPC-31260, suggesting that post-application of OPC-31260 cleared AVT and MT from their receptors. The effects of AVT, MT, and their antagonists in H. japonica, which is adapted to a terrestrial habitat, are compared with our previously published data on Rana catesbeiana (=Lithobates catesbeianus), which is adapted to a semiaquatic habitat.

  7. cAMP Stimulates Transepithelial Short-Circuit Current and Fluid Transport Across Porcine Ciliary Epithelium.

    Science.gov (United States)

    Cheng, Angela King-Wah; Civan, Mortimer M; To, Chi-Ho; Do, Chi-Wai

    2016-12-01

    To investigate the effects of cAMP on transepithelial electrical parameters and fluid transport across porcine ciliary epithelium. Transepithelial electrical parameters were determined by mounting freshly isolated porcine ciliary epithelium in a modified Ussing chamber. Similarly, fluid movement across intact ciliary body was measured with a custom-made fluid flow chamber. Addition of 1, 10, and 100 μM 8-Br-cAMP (cAMP) to the aqueous side (nonpigmented ciliary epithelium, NPE) induced a sustained increase in short-circuit current (Isc). Addition of niflumic acid (NFA) to the aqueous surface effectively blocked the cAMP-induced Isc stimulation. The administration of cAMP to the stromal side (pigmented ciliary epithelium, PE) triggered a significant stimulation of Isc only at 100 μM. No additive effect was observed with bilateral application of cAMP. Likewise, forskolin caused a significant stimulation of Isc when applied to the aqueous side. Concomitantly, cAMP and forskolin increased fluid transport across porcine ciliary epithelium, and this stimulation was effectively inhibited by aqueous NFA. Depleting Cl- in the bathing solution abolished the baseline Isc and inhibited the subsequent stimulation by cAMP. Pretreatment with protein kinase A (PKA) blockers (H89/KT5720) significantly inhibited the cAMP- and forskolin-induced Isc responses. Our results suggest that cAMP triggers a sustained stimulation of Cl- and fluid transport across porcine ciliary epithelium; Cl- channels in the NPE cells are potentially a cellular site for this PKA-sensitive cAMP-mediated response.

  8. Direct current induced short-term modulation of the left dorsolateral prefrontal cortex while learning auditory presented nouns

    Directory of Open Access Journals (Sweden)

    Meyer Martin

    2009-07-01

    Full Text Available Abstract Background Little is known about the contribution of transcranial direct current stimulation (tDCS to the exploration of memory functions. The aim of the present study was to examine the behavioural effects of right or left-hemisphere frontal direct current delivery while committing to memory auditory presented nouns on short-term learning and subsequent long-term retrieval. Methods Twenty subjects, divided into two groups, performed an episodic verbal memory task during anodal, cathodal and sham current application on the right or left dorsolateral prefrontal cortex (DLPFC. Results Our results imply that only cathodal tDCS elicits behavioural effects on verbal memory performance. In particular, left-sided application of cathodal tDCS impaired short-term verbal learning when compared to the baseline. We did not observe tDCS effects on long-term retrieval. Conclusion Our results imply that the left DLPFC is a crucial area involved in short-term verbal learning mechanisms. However, we found further support that direct current delivery with an intensity of 1.5 mA to the DLPFC during short-term learning does not disrupt longer lasting consolidation processes that are mainly known to be related to mesial temporal lobe areas. In the present study, we have shown that the tDCS technique has the potential to modulate short-term verbal learning mechanism.

  9. Effect of cAMP on short-circuit current in isolated human ciliary body.

    Science.gov (United States)

    Wu, Ren-yi; Ma, Ning; Hu, Qian-qian

    2013-07-01

    Cyclic adenosine monophosphate (cAMP) could activate chloride channels in bovine ciliary body and trigger an increase in the ionic current (short-circuit current, Isc) across the ciliary processes in pigs. The purpose of this study was to investigate how cAMP modulates Isc in isolated human ciliary processes and the possible involvement of chloride transport across the tissue in cAMP-induced Isc change. In an Ussing-type chamber system, the Isc changes induced by the cAMP analogue 8-bromo-cAMP and an adenylyl cyclase activator forskolin in isolated human ciliary processes were assessed. The involvement of Cl(-) component in the bath solution was investigated. The effect of Cl(-) channel (10 µmol/L niflumic acid and 1 mmol/L 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)), K(+) channel (10 mmol/L tetraethylammonium chloride (TEA)), or Na(+) channel blockers (1 mmol/L amiloride) on 8-bromo-cAMP-induced Isc change was also studied. Dose-dependently, 8-bromo-cAMP (10 nmol/L-30 µmol/L) or forskolin (10 nmol/L-3 µmol/L) increased Isc across the ciliary processes with an increase in negative potential difference on the non-pigmented epithelium (NPE) side of the tissue. Isc increase induced by 8-bromo-cAMP was more pronounced when the drug was applied on the NPE side than on the pigmented epithelium side. When the tissue was bathed in low Cl(-) solutions, the Isc increase was significantly inhibited. Finally, niflumic acid and DIDS, but not TEA or amiloride, significantly prevented the Isc increase induced by 8-bromo-cAMP. cAMP stimulates stroma-to-aqueous anionic transport in isolated human ciliary processes. Chloride is likely to be among the ions, the transportation of which across the tissue is triggered by cAMP, suggesting the potential role of cAMP in the process of aqueous humor formation in human eyes.

  10. The short-circuit current of the ileum, but not the colon, is altered in the streptozotocin diabetic rat.

    Science.gov (United States)

    Forrest, Abigail; Makwana, Rajesh; Parsons, Mike

    2006-02-01

    Ion transport in control and streptozotocin-diabetic rat colon and ileum was studied using the Ussing chamber technique. No differences were observed between control and diabetic colonic mucosal short-circuit current under either basal or carbachol (100 nmol/L-1 micromol/L)-stimulated or prostaglandin E2 (100 nmol/L-1 micromol/L)-stimulated conditions. Similarly to colonic tissues, no differences in the short circuit current in either carbachol-stimulated or prostaglandin E2-stimulated tissues were observed between control and diabetic ileal mucosa. The basal diabetic ileal short circuit current (99.58 +/- 22.67 microA) was significantly greater than that of control ileal tissues (29.67 +/- 4.45 microA). This difference was abolished by the sodium-glucose-cotransporter inhibitor, phloridzin (50 micromol/L) (118.00 +/- 28.09 microA vs. 25.60 +/- 4.59 microA) and was also prevented by the replacement of glucose with mannitol in the buffer bathing the apical side of the tissue (control: 17.05 +/- 5.85 microA vs. 17.90 +/- 3.10 microA). Acetazolamide (450 micromol/L; a carbonic anhydrase inhibitor), amiloride, and bumetanide (100 micromol/L each; Na+-channel blockers), piroxicam (50 micromol/L; a COX1 cyclooxygenase inhibitor), and ouabain (1 mmol/L; a K+ transport inhibitor) had no effect on the basal short circuit current of either control or diabetic ileal tissues. This indicated that the alteration in the basal short circuit current of diabetic ileal tissues was due to a change in cellular glucose transport, whereas the evoked changes in short circuit current were unaffected by the diabetic state.

  11. Bunch compression for an FEL at NLCTA

    International Nuclear Information System (INIS)

    Zimmermann, F.

    1997-04-01

    As part of the design effort for a free electron laser driven by the Next Linear Collider Test Accelerator (NLCTA), the author reports studies of bunch-length compression utilizing the existing infrastructure and hardware. In one possible version of the NLCTA FEL, bunches with 900-microm FWHM length, generated by an S-band photo-injector, would be compressed to an rms length of 60--120 microm before entering the FEL undulator. It is shown that, using the present magnetic chicane, the bunch compression is essentially straightforward, and that almost all emittance-diluting effects, e.g. wakefields, chromaticity, or space charge in the bending magnets, are small. The only exception to this finding is the predicted increase of the horizontal emittance due to coherent synchrotron radiation (CSR). Estimates based on existing theories of coherent synchrotron radiation suggest a tripling or quadrupling of the initial emittance, which seems to preclude bunch compression during regular FEL operation. Serendipitously, the magnitude of the predicted emittance growth would, on the other hand, make the NLCTA chicane an excellent tool for measuring the effects of coherent synchrotron radiation. This will be of considerable interest to many future projects, in particular to the Linac Coherent Light Source (LCLS). As an aside, it is shown that coherent synchrotron radiation in a bending magnet gives rise to a minimum possible bunch length, which is very reminiscent of the Oide limit on the vertical spot size at the interaction point of a linear collider

  12. Technical Study on Improvement of Endurance Capability of Limit Short-circuit Current of Charge Control SMART Meter

    Science.gov (United States)

    Li, W. W.; Du, Z. Z.; Yuan, R. m.; Xiong, D. Z.; Shi, E. W.; Lu, G. N.; Dai, Z. Y.; Chen, X. Q.; Jiang, Z. Y.; Lv, Y. G.

    2017-10-01

    Smart meter represents the development direction of energy-saving smart grid in the future. The load switch, one of the core parts of smart meter, should be of high reliability, safety and endurance capability of limit short-circuit current. For this reason, this paper discusses the quick simulation of relationship between attraction and counterforce of load switch without iteration, establishes dual response surface model of attraction and counterforce and optimizes the design scheme of load switch for charge control smart meter, thus increasing electromagnetic attraction and spring counterforce. In this way, this paper puts forward a method to improve the withstand capacity of limit short-circuit current.

  13. Focusing of relativistic electron bunch, moving in cylindrical plasma waveguide

    International Nuclear Information System (INIS)

    Amatuni, A.Ts.; Ehlbakyan, S.S.; Sekhpossyan, E.V.

    1994-01-01

    The problem on the focusing of electron bunches moving with the relativistic velocity along the axis of cylindrical overdense plasma waveguide with the conducting internal surface is considered. The existence of periodic and nonperiodic components of the fields, generated in the plasma is shown. The conditions of electron bunch self-focusing by transverse electrical field and azimuthal magnetic field are derived. The possibility of the acceleration and focusing of electron or positron bunches by driving electron bunch wake field is discussed. The conditions, when the bunch in plasma waveguide moves without wake fields generating are obtained, which could be of the interest for the transport of relativistic electron (positron) bunches. 5 refs

  14. Method and apparatus for control of coherent synchrotron radiation effects during recirculation with bunch compression

    Science.gov (United States)

    Douglas, David R; Tennant, Christopher

    2015-11-10

    A modulated-bending recirculating system that avoids CSR-driven breakdown in emittance compensation by redistributing the bending along the beamline. The modulated-bending recirculating system includes a) larger angles of bending in initial FODO cells, thereby enhancing the impact of CSR early on in the beam line while the bunch is long, and 2) a decreased bending angle in the final FODO cells, reducing the effect of CSR while the bunch is short. The invention describes a method for controlling the effects of CSR during recirculation and bunch compression including a) correcting chromatic aberrations, b) correcting lattice and CSR-induced curvature in the longitudinal phase space by compensating T.sub.566, and c) using lattice perturbations to compensate obvious linear correlations x-dp/p and x'-dp/p.

  15. Bunch length measurements using electro-optical sampling at the SLS linac

    International Nuclear Information System (INIS)

    Winter, A.

    2004-07-01

    A mode-locked titanium-sapphire laser with 15 fs pulse width is used to determine the time profile of the picosecond electron bunches in the Swiss light source linac of the Paul Scherrer Institute, Villigen Switzerland. This was done using the electro-optic effect in Zinc-Telluride crystals and sampling the change induced by coherent transition radiation with the TiSa laser. The development, implementation and results of an analogue synchronisation system to synchronise the repetition rate of the TiSa laser to the radio frequency of the accelerator with a short term stability of 40 fs is presented. The experimental setup of the bunch length measurements is described and results are presented on the coincidence measurements between the laser pulses and the coherent transition radiation pulses generated by the electron bunches. (orig.)

  16. Short-circuit current density imaging of crystalline silicon solar cells via lock-in thermography: Robustness and simplifications

    International Nuclear Information System (INIS)

    Fertig, Fabian; Greulich, Johannes; Rein, Stefan

    2014-01-01

    Spatially resolved determination of solar cell parameters is beneficial for loss analysis and optimization of conversion efficiency. One key parameter that has been challenging to access by an imaging technique on solar cell level is short-circuit current density. This work discusses the robustness of a recently suggested approach to determine short-circuit current density spatially resolved based on a series of lock-in thermography images and options for a simplified image acquisition procedure. For an accurate result, one or two emissivity-corrected illuminated lock-in thermography images and one dark lock-in thermography image have to be recorded. The dark lock-in thermography image can be omitted if local shunts are negligible. Furthermore, it is shown that omitting the correction of lock-in thermography images for local emissivity variations only leads to minor distortions for standard silicon solar cells. Hence, adequate acquisition of one image only is sufficient to generate a meaningful map of short-circuit current density. Beyond that, this work illustrates the underlying physics of the recently proposed method and demonstrates its robustness concerning varying excitation conditions and locally increased series resistance. Experimentally gained short-circuit current density images are validated for monochromatic illumination in comparison to the reference method of light-beam induced current

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

    International Nuclear Information System (INIS)

    Delsim-Hashemi, Hossein

    2008-09-01

    The longitudinal profile of electron bunches plays an important role in the design of single-pass free electron lasers and future linear e + e - 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 μJ) 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.)

  18. 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.)

  19. Critical current degradation of short YBa2Cu3O7-δ coated conductor due to an unprotected quench

    International Nuclear Information System (INIS)

    Wang, X; Trociewitz, U P; Schwartz, J

    2011-01-01

    The critical current of a short YBa 2 Cu 3 O 7-δ (YBCO) coated conductor sample degrades in an unprotected quench performed in a nearly adiabatic environment at 30 K. The conductor has Cu stabilizers on both surfaces. The quench is initiated by a heater attached to the sample surface. The amplitude of the transport current is fixed as 91% of the sample's initial critical current. The duration of the current is increased to simulate an unprotected quench and to reach increasing and controlled voltage and temperature levels. A peak temperature of 490 ± 50 K and a heating rate of 1800 K s -1 are measured when the critical current degrades by ∼ 5%. The applied thermal strain on the YBCO layer from 30 to 490 K is estimated to be 0.31% and is applied at a strain rate of ∼ 1% s -1 . The rate of temperature change and the time to reach a certain peak temperature, determined by the current density in the Cu stabilizer, are estimated assuming adiabatic conditions based on the short sample case. For a Cu stabilizer current density ranging from 1000 to 2000 A mm -2 , achieved in commercial conductors currently available, the quench detection and protection requires a response time -2 may challenge the existing detection and protection techniques for the same 200 K limit. Integrating the substrate as part of the stabilizer may help reduce the stabilizer current density to gain more time for quench detection and protection while maintaining the engineering current density.

  20. BBAT: Bunch and bucket analysis tool

    International Nuclear Information System (INIS)

    Deng, D.P.

    1995-01-01

    BBAT is written to meet the need of an interactive graphical tool to explore the longitudinal phase space. It is driven for testing new ideas or new tricks quickly. It is especially suitable for machine physicists or operation staff as well both in the control room during machine studies or off-line to analyze the data. The heart of the package contains a set of c-routines to do the number crunching. The graphics part is wired with scripting language tcl/tk and BLT. The c-routines are general enough that one can write new applications such as animation of the bucket as a machine parameter varies via a sliding scale. BBAT deals with single rf system. For double rf system, one can use Dr. BBAT, which stands for Double rf Bunch and Bucket Analysis Tool. One usage of Dr. BBAT is to visualize the process of bunch coalescing and flat bunch creation

  1. Note on polarized RHIC bunch arrangement

    International Nuclear Information System (INIS)

    Underwood, D.

    1996-01-01

    We discuss what combinations of bunch polarization in the two RHIC rings are necessary to do the physics measurements at various interaction regions. We also consider the bunches for both the pion inclusive and p-p elastic polarization measurements. Important factors to consider are the direction of the polarization with respect to the momentum in each bunch, the beam gas backgrounds, and the simulation of zero - polarization in one beam by averaging + and - helicity, and luminosity monitoring for normalization. These considerations can be addressed by setting the relative number of each of the 9 combinations possible at each of the 6 interaction regions. The combinations are (+ empty -) yellow X (+ empty -)blue, where yellow and blue are the counter-rotating rings

  2. Generation of relativistic electron bunches in plasma synchrotron Gyrac-x for hard x-ray production

    International Nuclear Information System (INIS)

    Andreev, V.V.; Umnov, A.M.

    2000-01-01

    Experiment performed on plasma synchrotron Gyrac-X operating on synchrotron gyromagnetic autoresonance (SGA) is described. Gyrac-X is a compact plasma x-ray source in which kinetic energy of relativistic electrons obtained under SGA converts into x-ray by falling e-bunches on to a heavy metal target. The plasma synchrotron acts in a regime of a magnetic field pulse packet under constant level of microwave power. Experiments and numerical modeling of the process showed that such a regime allowed obtaining dense short lived relativistic electron bunches with average electron energy of 500 keV - 4.5 MeV. Parameters of the relativistic electron bunch (energy, density and volume) and dynamics of the electron bunches can be controlled by varying the parameters of the SGA process. Possibilities of x-ray intensity increase are also discussed

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

    International Nuclear Information System (INIS)

    Fox, John D

    1999-01-01

    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, DAΦNE, 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

  4. Bunch coalescing in the Fermilab Main Ring

    International Nuclear Information System (INIS)

    Wildman, D.; Martin, P.; Meisner, K.; Miller, H.W.

    1987-01-01

    A new RF system has been installed in the Fermilab Main Ring to coalesce up to 13 individual bunches of protons or antiprotons into a single high-intensity bunch. The coalescing process consists of adiabatically reducing the h=1113 Main Ring RF voltage from 1 MV to less than 1 kV, capturing the debunched beam in a linearized h=53 and h=106 bucket, rotating for a quarter of a synchrotron oscillation period, and then recapturing the beam in a single h=1113 bucket. The new system is described and the results of recent coalescing experiments are compared with computer-generated particle tracking simulations

  5. Bunch heating by coherent synchrotron radiation

    International Nuclear Information System (INIS)

    Heifets, S.A.; Zolotorev, M.

    1995-10-01

    The authors discuss here effects which define the steady-state rms energy spread of a microbunch in a storage ring. It is implied that the longitudinal microwave instability is controlled by low α lattice. In this case the coherent synchrotron radiation, if exists, may be the main factor defining the bunch temperature. Another effect comes from the fact that a nonlinear momentum compaction of such lattices makes Haissinskii equation not applicable, and the coherent synchrotron radiation may effect not only bunch lengthening but the energy spread as well

  6. Mode of the short circuit in the direct current electric traction network with different feed charts of fyder area

    Directory of Open Access Journals (Sweden)

    P. Mihalichenko

    2012-12-01

    Full Text Available In the article the results of mathematical design of the system of electric traction of direct current are represented in the mode of short circuit and different feed charts of fyder area: two-sided; one-sided. Comparison of transitional electric sizes which characterize electromagnetic processes during these malfunctions is analysed and executed.

  7. Sub-fs electron bunch generation with sub-10-fs bunch arrival-time jitter via bunch slicing in a magnetic chicane

    Directory of Open Access Journals (Sweden)

    J. Zhu

    2016-05-01

    Full Text Available The generation of ultrashort electron bunches with ultrasmall bunch arrival-time jitter is of vital importance for laser-plasma wakefield acceleration with external injection. We study the production of 100-MeV electron bunches with bunch durations of subfemtosecond (fs and bunch arrival-time jitters of less than 10 fs, in an S-band photoinjector by using a weak magnetic chicane with a slit collimator. The beam dynamics inside the chicane is simulated by using two codes with different self-force models. The first code separates the self-force into a three-dimensional (3D quasistatic space-charge model and a one-dimensional coherent synchrotron radiation (CSR model, while the other one starts from the first principle with a so-called 3D sub-bunch method. The simulations indicate that the CSR effect dominates the horizontal emittance growth and the 1D CSR model underestimates the final bunch duration and emittance because of the very large transverse-to-longitudinal aspect ratio of the sub-fs bunch. Particularly, the CSR effect is also strongly affected by the vertical bunch size. Due to the coupling between the horizontal and longitudinal phase spaces, the bunch duration at the entrance of the last dipole magnet of the chicane is still significantly longer than that at the exit of the chicane, which considerably mitigates the impact of space charge and CSR effects on the beam quality. Exploiting this effect, a bunch charge of up to 4.8 pC in a sub-fs bunch could be simulated. In addition, we analytically and numerically investigate the impact of different jitter sources on the bunch arrival-time jitter downstream of the chicane, and define the tolerance budgets assuming realistic values of the stability of the linac for different bunch charges and compression schemes.

  8. Development of bunch by bunch transverse feedback system at Hefei light source

    International Nuclear Information System (INIS)

    Wang Junhua; Zheng Kai; Li Weimin; Yang Yongliang; Huang Longjun; Chen Yuanbo; Zhou Zeran; Wang Lin; Liu Zeping; Sun Baogen; Ma Li; Cao Jianshe; Yue Junhui; Liu Dekang; Ye Kairong

    2008-01-01

    This paper has introduced the development of the transverse bunch-by-bunch measurement and feedback system, including the experiment of damping the coupled bunch instability. Some key technologies on the system have been introduced: the vector calculation module as a signal processing module used to adjust the phase of the feedback signals, the feedback kicker cavity and the notch filter used to filter the DC component and revolution frequencies component in a signal and save the feedback power. The result of the feedback experiment is mentioned: the instability oscillation was damped when the feedback system was on. (authors)

  9. Results of Preliminary Tests of PAR Bunch Cleaning

    CERN Document Server

    Yao, Chihyuan; Grelick, Arthur; Lumpkin, Alex H; Sereno, Nicholas S

    2005-01-01

    A particle accumulator ring (PAR) is used at the Advanced Photon Source (APS) to collect multiple linac bunches and compress them into a 0.3-ns (rms) single bunch for booster injection. A 9.77-MHz fundamental rf system and a 117.3-MHz harmonic rf system are employed for initial beam capture and bunch length compression. Satellite bunches with very low charge form due to rf phase drifts or beam loading change. These satellites, when injected into the booster and then into the storage ring (SR), cause bunch impurity at three buckets from the target bucket. Storage ring and booster bunch cleaning was tried but proved to be difficult due to the top-up mode of operation in the storage ring and tune drift in the booster synchrotron. Recently we implemented a PAR bunch-cleaning system with tune-modulated harmonic rf knockout. Preliminary tests gave a measured SR bunch purity of better than 10

  10. Quality Assessment of Soaps Produced from Palm Bunch Ash ...

    African Journals Online (AJOL)

    Quality Assessment of Soaps Produced from Palm Bunch Ash-Derived Alkali and ... Journal of Applied Sciences and Environmental Management ... The remedial process involved subjecting the dried palm bunch matter to total combustion, ...

  11. Theory of coherent transition radiation generated by ellipsoidal electron bunches

    NARCIS (Netherlands)

    Root, op 't W.P.E.M.; Smorenburg, P.W.; Oudheusden, van T.; Wiel, van der M.J.; Luiten, O.J.

    2007-01-01

    We present the theory of coherent transition radiation (CTR) generated by ellipsoidal electron bunches. We calculate analytical expressions for the electric field spectrum, the power spectrum, and the temporal electric field of CTR, generated by cylindrically symmetric ellipsoidal electron bunches

  12. 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.

  13. High bandwidth beam current monitor

    International Nuclear Information System (INIS)

    Baltrusaitis, R.M.; Ekdahl, C.A.; Cooper, R.G.; Peterson, E.; Warn, C.E.

    1993-01-01

    A stripline directional coupler beam current monitor capable of measuring the time structure of a 30-ps electron beam bunch has been developed. The time response performance of the monitor compares very well with Cherenkov light produced in quartz by the electron beam. The four-pickup monitor is now used on a routine basis for measuring the beam duration, tuning for optimized beam bunching, and centering the bunch in the beam pipe

  14. 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.

  15. Effect of notch depth of modified current collector on internal-short-circuit mitigation for lithium-ion battery

    Science.gov (United States)

    Wang, Meng; Noelle, Daniel J.; Shi, Yang; Le, Anh V.; Qiao, Yu

    2018-01-01

    Formation of internal short circuit (ISC) may result in catastrophic thermal runaway of lithium-ion battery (LIB). Among LIB cell components, direct contact between cathode and anode current collectors is most critical to the ISC behavior, yet is still relatively uninvestigated. In the current study, we analyze the effect of heterogeneity of current collector on the temperature increase of LIB cells subjected to mechanical abuse. The cathode current collector is modified by surface notches, so that it becomes effectively brittle and the ISC site can be isolated. Results from impact tests on LIB cells with modified current collectors suggest that their temperature increase can be negligible. The critical parameters include the failure strain and the failure work of modified current collector, both of which are related to the notch depth.

  16. The Case: Bunche-Da Vinci Learning Partnership Academy

    Science.gov (United States)

    Eisenberg, Nicole; Winters, Lynn; Alkin, Marvin C.

    2005-01-01

    The Bunche-Da Vinci case described in this article presents a situation at Bunche Elementary School that four theorists were asked to address in their evaluation designs (see EJ791771, EJ719772, EJ791773, and EJ792694). The Bunche-Da Vinci Learning Partnership Academy, an elementary school located between an urban port city and a historically…

  17. 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.

  18. No effect of transcranial direct current stimulation of the dorsolateral prefrontal cortex on short-term memory.

    Science.gov (United States)

    Wang, Jing; Wen, Jian-Bing; Li, Xiao-Li

    2018-01-01

    Short-term memory refers to the capacity for holding information in mind for a short period of time with conscious memorization. It is an important ability for daily life and is impaired in several neurological and psychiatric disorders. Anodal transcranial direct current stimulation (tDCS) applied to the dorsolateral prefrontal cortex (DLPFC) was reported to enhance the capability of short-term memory in healthy subjects. However, results were not consistent and what is the possible impact factor is not known. One important factor that may significantly influence the effect of tDCS is the timing of tDCS administration. In order to explore whether tDCS impact short-term memory and the optimal timing of tDCS administration, we applied anodal tDCS to the left DLPFC to explore the modulatory effect of online and off-line tDCS on digit span as well as visual short-term memory performance in healthy subjects. Results showed tDCS of the left DLPFC did not influence intentional digit span memory performance, whether before the task or during the task. In addition, tDCS of the DLPFC administered before the task showed no effect on visual short-term memory, while there was a trend of increase in false alarm when tDCS of the DLPFC administered during the task. These results did not provide evidence for the enhancement of short-term memory by tDCS of the left DLPFC in healthy subjects, but it suggested an importance of administration time for visual short-term memory. Further studies are required to taking into account the baseline performance of subjects and time-dependence feature of tDCS. © 2017 John Wiley & Sons Ltd.

  19. Single bunch stability in the ESRF

    International Nuclear Information System (INIS)

    Farvacque, L.

    1990-01-01

    The longitudinal wake potential/impedance and bunch lengthening/stability in ESRF were studied. A cylindrical approximation of individual components of the vacuum chamber were studied. The results are wake potential and loss parameters. Measurements are necessary when the cylindrical approximation is not realistic. The coaxial wire method which is used gives a wake potential that can be substituted for the computed wake in the analysis. A measurement bench is presently being tested at ESRF. Wake potentials (computed or measured) are added before modeling or approximation is made. The impedance model used is the broad-band resonator model. Equations are derived for the longitudinal potential well. The bunch shape can be estimated knowing the first moments of the line density function. Mode coupling cannot explain the turbulent instability threshold. The threshold has then to be estimated by crude assumptions on potential well or bunch shape distortions. In the ESRF case, this threshold corresponds to a value of asymmetry s (th) = 0.6. Above the threshold the bunch lengthens with this constant asymmetry value

  20. CERN: The best of the bunch

    International Nuclear Information System (INIS)

    Gagliardi, F.

    1992-01-01

    As other factors governing the electron-positron collision rate in CERN's LEP 27-kilometre storage ring reach their limit, one way of coaxing the collision rate higher is to increase the number of bunches stored in the ring

  1. Current results for the NRC's short cracks in piping and piping welds research program

    International Nuclear Information System (INIS)

    Wilkowski, G.; Krishnaswamy, P. Brust, F.; Francini, R.; Ghadiali, N.; Kilinski, T.; Marschall, C.; Rahman, S.; Rosenfield, A.; Scott, P.

    1994-01-01

    The overall objective of the Short Cracks in Piping and Piping Welds Program is to verify and improve engineering analyses to predict the fracture behavior of circumferentially cracked pipe under quasi-static loading with particular attention to crack lengths typically used in LBB or flaw evaluation criteria. The program consists of 8 technical tasks as listed below. Task 1 Short through-wall-cracked (TWC) pipe evaluations. Task 2 Short surface-cracked pipe evaluations. Task 3 Bi-metallic weld crack evaluations. Task 4 Dynamic strain aging and crack instabilities. Task 5 Fracture evaluations of anisotropic pipe. Task 6 Crack-opening-area evaluations. Task 7 NRCPIPE Code improvements. Task 8 Additional efforts. Since the last WRSM meeting several additional tasks have been initiated in this program. These are discussed in Task 8. Based on results to date, the first seven tasks have also been modified as deemed necessary. The most significant accomplishments in each of these tasks since the last WRSIM meeting are discussed below. The details of all the results presented here are published in the semiannual reports from this program

  2. Independent component analysis applied to long bunch beams in the Los Alamos Proton Storage Ring

    Science.gov (United States)

    Kolski, Jeffrey S.; Macek, Robert J.; McCrady, Rodney C.; Pang, Xiaoying

    2012-11-01

    Independent component analysis (ICA) is a powerful blind source separation (BSS) method. Compared to the typical BSS method, principal component analysis, ICA is more robust to noise, coupling, and nonlinearity. The conventional ICA application to turn-by-turn position data from multiple beam position monitors (BPMs) yields information about cross-BPM correlations. With this scheme, multi-BPM ICA has been used to measure the transverse betatron phase and amplitude functions, dispersion function, linear coupling, sextupole strength, and nonlinear beam dynamics. We apply ICA in a new way to slices along the bunch revealing correlations of particle motion within the beam bunch. We digitize beam signals of the long bunch at the Los Alamos Proton Storage Ring with a single device (BPM or fast current monitor) for an entire injection-extraction cycle. ICA of the digitized beam signals results in source signals, which we identify to describe varying betatron motion along the bunch, locations of transverse resonances along the bunch, measurement noise, characteristic frequencies of the digitizing oscilloscopes, and longitudinal beam structure.

  3. Independent component analysis applied to long bunch beams in the Los Alamos Proton Storage Ring

    Directory of Open Access Journals (Sweden)

    Jeffrey S. Kolski

    2012-11-01

    Full Text Available Independent component analysis (ICA is a powerful blind source separation (BSS method. Compared to the typical BSS method, principal component analysis, ICA is more robust to noise, coupling, and nonlinearity. The conventional ICA application to turn-by-turn position data from multiple beam position monitors (BPMs yields information about cross-BPM correlations. With this scheme, multi-BPM ICA has been used to measure the transverse betatron phase and amplitude functions, dispersion function, linear coupling, sextupole strength, and nonlinear beam dynamics. We apply ICA in a new way to slices along the bunch revealing correlations of particle motion within the beam bunch. We digitize beam signals of the long bunch at the Los Alamos Proton Storage Ring with a single device (BPM or fast current monitor for an entire injection-extraction cycle. ICA of the digitized beam signals results in source signals, which we identify to describe varying betatron motion along the bunch, locations of transverse resonances along the bunch, measurement noise, characteristic frequencies of the digitizing oscilloscopes, and longitudinal beam structure.

  4. Transverse blowup along bunch train caused by electron cloud in BEPC

    International Nuclear Information System (INIS)

    Liu Yudong; Guo Zhiyuan; Qin Qing; Wang Jiuqing; Zhao Zheng

    2006-01-01

    Electron cloud instability (ECI) may take place in a storage ring when the machine is operated with a multi-bunch positively charged beam. Transverse blowup due to electron cloud has been observed in some machines and is considered to be a major limit factor in the development of high current and high luminosity electron positron colliders. With a streak camera, the transverse blowup along the bunch train was first observed in an experiment at the Beijing Electron-Positron Collider (BEPC) and the simulation results were used to compared with the observation. (authors)

  5. Results on the interaction of an intense bunched electron beam with resonant cavities at 35 GHz

    CERN Document Server

    Gardelle, J; Rullier, J L; Vermare, C; Wuensch, Walter; Lidia, S M; Westenskow, G A; Donohue, J T; Meurdesoif, Y; Lekston, J M; MacKay, W W

    1999-01-01

    The Two-Beam Accelerator (TBA) concept is currently being investigated both at Lawrence Berkeley National Laboratory (LBNL) and at CERN. As part of this program, a 7 MeV, 1-kA electron beam produced by the PIVAIR accelerator at CESTA has been used to power a free electron laser (FEL) amplifier at 35 GHz. At the FEL exit, the bunched electron beam is transported and focused into a resonant cavity built by the CLIC group at CERN. The power and frequency of the microwave output generated when the bunched beam traverses two different cavities are measured. (7 refs).

  6. Design of bunch compressing system with suppression of coherent synchrotron radiation for ATF upgrade

    International Nuclear Information System (INIS)

    Jing, Yichao; Fedurin, Mikhail; Stratakis, Diktys

    2015-01-01

    One of the operation modes for Accelerator Test Facility (ATF) upgrade is to provide high peak current, high quality electron beam for users. Such operation requires a bunch compressing system with a very large compression ratio. The CSR originating from the strong compressors generally could greatly degrade the quality of the electron beam. In this paper, we present our design for the entire bunch compressing system that will limit the effect of CSR on the e-beam@s quality. We discuss and detail the performance from the start to end simulation of such a compressor for ATF.

  7. Space-charge effects on bunching of electrons in the CEBAF injector

    International Nuclear Information System (INIS)

    Liu, H.

    1997-01-01

    The main injector for the 4 GeV CEBAF accelerator at Thomas Jefferson national accelerator facility was designed to deliver simultaneously three CW electron beams for nuclear physics research. The maximum design current for a single beam from the injector is 100 μA, or 0.2 pC per microbunch at a repetition rate of 499 MHz. It was found through computer simulation that space charge even at a subpicocoulomb level can spoil the bunching of electrons significantly, and some unexpected phenomena observed experimentally could be explained accordingly. This problem arises because of the low-momentum tilt allowed for bunching to preserve low-momentum spread. In this paper, we analyze in detail the space-charge effects on bunching of electrons with the CEBAF injector as an example. Conditions for effective matching of longitudinal phase space in the presence of space charge are discussed. (orig.)

  8. On the quantitative prediction of bunch lengthening in high energy electron storage rings

    International Nuclear Information System (INIS)

    Weiland, T.

    1981-12-01

    The longitudinal current dependent electromagnetic interaction between a bunch of charged particles and accelerator components can be described by a Green's Function in time domain or by an impedance in frequency domain. The aim of this paper is to describe a procedure which yields an approximate Green's Function for cylindrically symmetric objects. Once this Green's Function is quantitatively known the equation of motion for the particles can be solved easily by a turn-by-turn tracking code on a computer. Thus it is possible to predict the bunch length and width as a function of charge per bunch for future accelerators and storage rings based on pure geometrical data of the accelerator components. Results are presented for PETRA and LEP. A comparison between measurements at PETRA and computations shows an excellent agreement. (orig.)

  9. Emittance simulation for a different electron bunch charges with upgraded PITZ setup

    Energy Technology Data Exchange (ETDEWEB)

    Vashchenko, Grygorii [DESY, Platanenallee 6, 15738 Zeuthen (Germany)

    2013-07-01

    The photo injector test facility at DESY, Zeuthen site (PITZ) was invented with an aim to develop, characterize and optimize the electron sources for linac driven free electron lasers like FLASH and European XFEL. As a prerequisite for a successful experimental emittance optimization, emittance dependencies on the majority of linac parameters have to be studied in simulations. Despite that the nominal electron bunch charge for the operation of FLASH and XFEL is 1nC, there is an interest of the community to operate with other bunch charges. Emittance dependencies on such machine parameters like laser spot size on the photo cathode, laser pulse length, gun launching phase, focusing solenoid current and first accelerating structure gradient are simulated for different electron bunch charges. Based on the simulations data the systematic errors caused by detuning of the different machine parameters from their optimum values are estimated.

  10. Controlling multi-bunches by a fast phase switching

    International Nuclear Information System (INIS)

    Decker, F.J.; Jobe, R.K.; Merminga, N.; Thompson, K.A.

    1990-09-01

    In linear accelerators with two or more bunches the beam loading of one bunch will influence the energy and energy spread the following bunches. This can be corrected by quickly changing the phase of a traveling wave-structure, so that each bunch receives a slightly different net phase. At the SLAC Linear Collider (SLC) three bunches, two (e + ,e - ) for the high energy collisions and one (e - -scavenger) for producing positrons should sit at different phases, due to their different tasks. The two e - -bunches are extracted from the damping ring at the same cycle time about 60 ns apart. Fast phase switching of the RF to the bunch length compressor in the Ring-To-Linac (RTL) section can produce the necessary advance of the scavenger bunch (about 6 degree in phase). This allows a low energy spread of this third bunch at the e + -production region at 2/3 of the linac length, while the other bunches are not influenced. The principles and possible other applications of this fast phase switching as using it for multi-bunches, as well as the experimental layout for the actual RTL compressor are presented

  11. Extra-high short-circuit current for bifacial solar cells in sunny and dark-light conditions.

    Science.gov (United States)

    Duan, Jialong; Duan, Yanyan; Zhao, Yuanyuan; He, Benlin; Tang, Qunwei

    2017-09-05

    We present here a symmetrically structured bifacial solar cell tailored by two fluorescent photoanodes and a platinum/titanium/platinum counter electrode, yielding extra-high short-circuit current densities as high as 28.59 mA cm -2 and 119.9 μA cm -2 in simulated sunlight irradiation (100 mW cm -2 , AM1.5) and dark-light conditions, respectively.

  12. Compensation of the magnetization current induced sextupole error at LHC injection field by short lumped permanent sextupole magnets, incorporated into the end configuration of superconducting dipoles

    CERN Document Server

    Asner, A

    1985-01-01

    Compensation of the magnetization current induced sextupole error at LHC injection field by short lumped permanent sextupole magnets, incorporated into the end configuration of superconducting dipoles

  13. Nonrelativistic electron bunch train for coherently enhanced terahertz radiation sources

    International Nuclear Information System (INIS)

    Li Yuelin; Kim, Kwang-Je

    2008-01-01

    We propose to generate a train of prebunched electron beams for producing coherently enhanced Smith-Purcell radiation [S. J. Smith and E. M. Purcell, Phys. Rev. 92, 1069 (1953)] in the terahertz wavelength range. In this scheme, a train of picosecond laser pulses is produced to drive a photoemission gun to generate a train of 50 keV electron pulses. The parameters are chosen so that the space-charge effect does not destroy the pulse time structure. Smith-Purcell radiation from the electron pulse train is enhanced due both to the short length of the individual electron bunch and to the repetitive structure of the beam. Example systems producing coherent terahertz power at about 1 mW are described

  14. The dependence of the short circuit current with γ-radiation in CuGaSe2

    International Nuclear Information System (INIS)

    Gasimoglu, I.; Mamedova, I.A.; Bagirov, A.G.

    2005-01-01

    Full text: The A I B III C IV semiconducting compounds are of interest for semiconducting devising. In particular the presence of the birefringence makes the compounds as a perspective materials for using in nonlinear optical transformers. Besides, the complex generation-recombination processes in these compounds are due to the local states in the band gap, which is also due to the complex chemical structure of these compounds. In this report the results of the influence of γ-radiation on the short circuit current in CuGaSe 2 are presented. The Co 6 0 with the quantum energy of 1.25 MeV was a source of radiation. The resistance was 10 2 kΩ at 300 K. The In-Ga eutectic was used as a contact. The measurements have been carried out at 77 K. The electrometer B7-30 was used for the short circuit current measurements, sensitivity of which is 10 -15 A. The intensity of γ-rays was 20 R/s, durability of radiation was 15 min. The spectrometer SPM-2 was used as a source of radiation of monoxrmator light. The spectral dependence of short circuit current of non radiated CuGaSe 2 crystal has a maximum at λ=700 nm (0.77 eV) with the half width of 0.26 eV. The maximum of short circuit current is in good agreement with the value 1.8 eV at 300 K. That is why one can assume that observed peak in J sc ∼∼f(λ) dependence with the maximum at 1.77 eV is due to electronic transitions from the valence band to conduction band. After radiation of CuGaSe 2 crystal new maximum is observed in the spectral dependence of short circuit current at λ=770 nm (1.61 eV) at 77 K. Splitting between the peaks is 0.13 eV. The appearance of the second peak maybe is due to the formation of radiation defects of acceptor type, which are located for 0.13 eV above than the top of valence band. The peak at 1.59 eV, which is due the donor-acceptor recombination, is observed in photoluminescence spectra. It is assumed that, Se vacancy forms the donor levels, Cu vacancy -acceptor levels

  15. A probabilistic method for the estimation of ocean surface currents from short time series of HF radar data

    Science.gov (United States)

    Guérin, Charles-Antoine; Grilli, Stéphan T.

    2018-01-01

    We present a new method for inverting ocean surface currents from beam-forming HF radar data. In contrast with the classical method, which inverts radial currents based on shifts of the main Bragg line in the radar Doppler spectrum, the method works in the temporal domain and inverts currents from the amplitude modulation of the I and Q radar time series. Based on this principle, we propose a Maximum Likelihood approach, which can be combined with a Bayesian inference method assuming a prior current distribution, to infer values of the radial surface currents. We assess the method performance by using synthetic radar signal as well as field data, and systematically comparing results with those of the Doppler method. The new method is found advantageous for its robustness to noise at long range, its ability to accommodate shorter time series, and the possibility to use a priori information to improve the estimates. Limitations are related to current sign errors at far-ranges and biased estimates for small current values and very short samples. We apply the new technique to a data set from a typical 13.5 MHz WERA radar, acquired off of Vancouver Island, BC, and show that it can potentially improve standard synoptic current mapping.

  16. Influence of Waveform and Current Direction on Short-Interval Intracortical Facilitation

    DEFF Research Database (Denmark)

    Delvendahl, Igor; Lindemann, Hannes; Jung, Nikolai H

    2014-01-01

    -posterior (AP) current direction (AP-AP or PA-PA), whereas current direction was reversed between first and second pulse for half-sine paired-pulse stimulation (PA-AP and AP-PA). RESULTS: Monophasic AP-AP stimulation resulted in stronger early SICF at 1.4 ms relative to late SICF at 2.8 and 4.4 ms, whereas...... monophasic PA-PA stimulation produced SICF of comparable size at all three peaks. With half-sine stimulation the third SICF peak was reduced for PA-AP current orientation compared with AP-PA. CONCLUSION: SICF elicited using monophasic as well as half-sine pulses is affected by current direction at clearly......BACKGROUND: Transcranial magnetic stimulation (TMS) of the human primary motor hand area (M1-HAND) can produce multiple descending volleys in fast-conducting corticospinal neurons, especially so-called indirect waves (I-waves) resulting from trans-synaptic excitation. Facilitatory interaction...

  17. Current distribution in LV networks during 1-phase MV short-circuit

    NARCIS (Netherlands)

    Waes, van J.B.M.; Provoost, F.; Merwe, van der J.; Cobben, J.F.G.; Deursen, van A.P.J.; van Riet, M.J.M.; Laan, van der P.C.T.

    2000-01-01

    This paper describes the consequences of a fault in a medium voltage network on the grounding systems at the LV-side. To study the current distribution and to verify the models, we deliberately introduced one phase to ground faults in the 10 kV floating MV network. The selected site was the end of a

  18. Fast transient current response to switching events in short chains of molecular islands

    Czech Academy of Sciences Publication Activity Database

    Kalvová, Anděla; Špička, Václav; Velický, B.

    2013-01-01

    Roč. 26, č. 4 (2013), s. 773-777 ISSN 1557-1939 R&D Projects: GA ČR GAP204/12/0897 Institutional support: RVO:68378271 Keywords : nonequilibrium * molecular islands * initial correlations * transient currents Subject RIV: BE - Theoretical Physics Impact factor: 0.930, year: 2013

  19. Single bunch instabilities in an SSC

    International Nuclear Information System (INIS)

    Ruth, R.D.

    1984-01-01

    In this note coherent instability thresholds are estimated for the SSC and discuss some of the subsequent design restrictions. The various instabilities are set out in a block diagram with the essential features of each. The assumption is made that long wavelength coupled bunch effects can be cured effectively by a feedback system (both longitudinal and transverse) and that the impedance of the feedback system is such as to cancel that of the environment (at low frequency). Alternatively, the long wake field is assumed to be exactly canceled, on the average, by a feedback wake field. This leaves only single bunch effects. Thresholds for fast-blowup are discussed both in the longitudinal and transverse and the transverse mode coupling instability more familiar in electron/positron storage rings is covered. The impedances considered are a broadband impedance and the resistive wall impedance

  20. Halo formation in three-dimensional bunches

    International Nuclear Information System (INIS)

    Gluckstern, R.L.; Fedotov, A.V.; Kurennoy, S.; Ryne, R.

    1998-01-01

    We have constructed, analytically and numerically, a class of self-consistent six-dimensional (6D) phase space stationary distributions. Stationary distributions allow us to study the halo development mechanism without it being obscured by beam redistribution and its effect on halo formation. The beam is then mismatched longitudinally and/or transversely, and we explore the formation of longitudinal and transverse halos in 3D axisymmetric beam bunches. We find that the longitudinal halo forms first for comparable longitudinal and transverse mismatches because the longitudinal tune depression is more severe than the transverse one for elongated bunches. Of particular importance is the result that, due to the coupling between longitudinal and transverse motion, a longitudinal or transverse halo is observed for a mismatch less than 10% if the mismatch in the other plane is large. copyright 1998 The American Physical Society

  1. Beam induced heating reduction by bunch flattening

    CERN Document Server

    Argyropoulos, T; Esteban Müller, JF; Jakobsen, S; Mastoridis, T; Metral, E; Mounet, N; Papotti, G; Pieloni, T; Salvant, B; Shaposhnikova, E; Timko, H

    2014-01-01

    The main purpose of this MD was to modify the beam induced heating on some critical LHC components by flattening the bunch distribution by applying an RF phase modulation. In this way, the beam spectrum was modified so that the power spectral density is reduced at low frequencies (below 1.1 GHz), which is the band of frequencies where the beam interaction with different component impedances is most critical. We present temperature measurements showing the beneficial effect of this latter distribution on some of the monitored devices. Longitudinal peak detected Schottky spectrum was also acquired during the first part of the MD with the intention of estimating the synchrotron frequency shift due to the reactive part of the longitudinal impedance. In the second part of the MD, an attempt to cure the transverse instability during the beta-squeeze was done by reducing the RF voltage to lengthen the bunches and enhance Landau Damping.

  2. Intracellular Na+ concentration influences short-term plasticity of glutamate transporter-mediated currents in neocortical astrocytes.

    Science.gov (United States)

    Unichenko, Petr; Myakhar, Olga; Kirischuk, Sergei

    2012-04-01

    Fast synaptic transmission requires a rapid clearance of the released neurotransmitter from the extracellular space. Glial glutamate transporters (excitatory amino acid transporters, EAATs) strongly contribute to glutamate removal. In this work, we investigated the paired-pulse plasticity of synaptically activated, glutamate transporter-mediated currents (STCs) in cortical layer 2/3 astrocytes. STCs were elicited by local electrical stimulation in layer 4 in the presence of ionotropic glutamate (AMPA and NMDA), GABAA, and GABAB receptor antagonists. In experiments with low [Na(+)]i (5 mM) intrapipette solution, STCs elicited by paired-pulse stimulation demonstrated paired-pulse facilitation (PPF) at short (astrocytic [Na(+)]i, reduced the mean STC amplitude, decreased PPF at short ISIs, and slowed STC kinetics. All GABA-induced changes were blocked by NO-711 and SNAP-5114, GABA transporter (GATs) antagonists. In experiments with the low intrapipette solution, GAT blockade under control conditions decreased PPF at short ISIs both at room and at near physiological temperatures. Dialysis of single astrocyte with low [Na(+)]i solution increased the amplitude and reduced PPR of evoked field potentials recorded in the vicinity of the astrocyte. We conclude that (1) endogenous GABA via GATs may influence EAAT functioning and (2) astrocytic [Na(+)]i modulates the short-term plasticity of STCs and in turn the efficacy of glutamate removal. Copyright © 2012 Wiley Periodicals, Inc.

  3. 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.

  4. A combined source of electron bunches and microwave power

    International Nuclear Information System (INIS)

    Xie, J.L.; Wang, F.Y.; Yang, X.P.; Shen, B.; Gu, W.; Zhang, L.W.

    2003-01-01

    In this article, the possibility of using a high power klystron amplifier simultaneously as a microwave power source as usual and an electron bunches source by extracting the spent beam with a magnet and also as an oscillator by feedback is investigated. The purpose of this study is to demonstrate the feasibility of constructing a very compact electron linear accelerator or for other applications of electron bunches. The feasibility of the idea was first examined by computer simulation of the electron motion in a 5 MW klystron and the characteristics of the klystron spent beam. Experimental study was then carried out by installing a radio frequency cavity and a Faraday cage in sequence at the exit end of a bending magnet located at the top of the klystron collector. The energy and current of the chopped spent electron beam can then be measured. By properly choosing the feedback circuit elements, the frequency stability of the klystron in oscillator mode was proved to be good enough for linac operation. According to the results presented in this article, it is evident that an extremely compact linac for research and education with better affordability can be constructed to promote the applications of linacs

  5. Shielded transient self-interaction of a bunch entering a circle from a straight path

    International Nuclear Information System (INIS)

    Li, R.; Bohn, C.L.; Bisognano, J.J.

    1997-01-01

    Recent developments in electron-gun and injector technologies enable production of short (mm-length), high-charge (nC-regime) bunches. In this parameter regime, the curvature effect on the bunch self-interaction, by way of coherent synchrotron radiation (CSR) and space-charge forces as the beam traverses magnet bends, may cause serious emittance degradation. In this paper, the authors study an electron bunch orbiting between two infinite, parallel conducting plates. The bunch moves on a trajectory from a straight path to a circular orbit and begins radiating. Transient effects, arising from CSR and space-charge forces generated from source particles both on the bend and on the straight path prior to the bend, are analyzed using Lienard-Wiechert fields, and their overall net effect is obtained. The influence of the plates on the transients is contrasted to their shielding of the steady-state radiated power. Results for emittance degradation induced by this self-interaction are also presented

  6. ELECTRON BUNCH CHARACTERIZATION WITH SUBPICOSECOND RESOLUTION USING ELECTRO-OPTIC TECHNIQUE

    International Nuclear Information System (INIS)

    SEMERTZIDIS, Y.K.; CASTILLO, V.; LARSEN, R.; LAZARUS, D.M.; NIKAS, D.; OZBEN, C.; SRINIVASAN-RAO, T.; STILLMAN, A.; TSANG, T.; KOWALSKI, L.

    2001-01-01

    In the past decade, the bunch lengths of electrons in accelerators have decreased dramatically and are in the range off a few millimeters. Measurement of the length as well as the longitudinal profile of these short bunches have been a topic of research in a number of institutions. One of the techniques uses the electric field induced by the passage of electrons in the vicinity of a birefringent crystal to change its optical characteristics. Well-established electro-optic techniques can then be used to measure the temporal characteristics of the electron bunch. The inherent fast response of the crystal facilitates the measurement to femtosecond time resolution. However, the resolution in experiments so far has been limited to 70 ps, by the bandwidth of the detection equipment. Use of a streak camera can improve this resolution to a few picoseconds. In this paper we present a novel, non-invasive, single-shot approach to improve the resolution to tens of femtoseconds so that sub mm bunch length can be measured

  7. Special features of the current-voltage characteristics of short superconducting bridges

    International Nuclear Information System (INIS)

    Zhilinskii, S.; Latyshev, Y.; Nad', F.

    1981-01-01

    A study was made of variable-thickness superconducting bridges made of tin and indium. The current-voltage characteristics were determined for these bridges as a function of their length and width. The characteristics exhibited a linear region as well as an inflection. The temperature of the appearance of such an inflection depended on the length of the bridge but was independent of the bridge material

  8. Current research efforts at JILA to test the equivalence principle at short ranges

    International Nuclear Information System (INIS)

    Faller, J.E.; Niebauer, T.M.; McHugh, M.P.; Van Baak, D.A.

    1988-01-01

    We are presently engaged in three different experiments to search for a possible breakdown of the equivalence principle at short ranges. The first of these experiments, which has been completed, is our so-called Galilean test in which the differential free-fall of two objects of differing composition was measured using laser interferometry. We observed that the differential acceleration of two test bodies was less than 5 parts in 10 billion. This experiment set new limits on a suggested baryon dependent ''Fifth Force'' at ranges longer than 1 km. With a second experiment, we are investigating substance dependent interactions primarily for ranges up to 10 meters using a fluid supported torsion balance; this apparatus has been built and is now undergoing laboratory tests. Finally, a proposal has been made to measure the gravitational signal associated with the changing water level at a large pumped storage facility in Ludington, Michigan. Measuring the gravitational signal above and below the pond will yield the value of the gravitational constant, G, at ranges from 10-100 m. These measurements will serve as an independent check on other geophysical measurements of G

  9. Stability of longitudinal modes in a bunched beam with mode coupling

    International Nuclear Information System (INIS)

    Satoh, K.

    1981-06-01

    In this paper we study a longitudinal coherent bunch instability in which the growth time is comparable to or less than the period of synchrotron oscillations. Both longitudinal and transverse bunch instabilities have been studied. In most treatments, however, the coherent force is assumed to be small and is treated as a perturbation compared with the synchrotron force. This makes the problem simpler because an individual synchrotron mode is decoupled. As bunch current increases, the coherent force is no longer small and the mode frequency shift becomes significant compared with the synchrotron frequency. Therefore in this case it is necessary to include coupling of the synchrotron modes. Recently a fast blow-up instability which comes from mode coupling was studied. Their method is to derive a dispersion relation for a bunched beam using the Vlasov equation and to analyze it as in a coasting beam. They showed that if mode coupling is included the Vlasov equation predicts a fast microwave instability with a stability condition similar to that for a coasting beam. In this paper we will partly follow their method and present a formalism which includes coupling between higher-order radial modes as well as coupling between synchrotron modes. The formalism is considered to be generalization of the Sacherer formalism without mode coupling. This theory predicts that instability is induced not only by coupling between different synchrotron modes, but also by coupling between positive and negative modes, since negative synchrotron modes are included in the theory in a natural manner. This formalism is to be used for a Gaussian bunch and a parabolic bunch, and is also useful for transverse problems

  10. Spatio-temporal dynamics of relativistic electron bunches during the micro bunching instability: study of the Synchrotron Soleil and UVSOR storage rings

    International Nuclear Information System (INIS)

    Roussel, Eleonore

    2014-01-01

    Relativistic electron bunches circulating in storage rings are used to produce intense radiation from far-infrared to X-rays. However, above a density threshold value, the interaction between the electron bunch and its own radiation can lead to a spatio-temporal instability called micro bunching instability. This instability is characterized by a strong emission of coherent THz radiation (typically 105 times stronger than the classical synchrotron radiation) which is a signature of the presence of microstructures (at mm scale) in the electron bunch. This instability is known to be a fundamental limitation of the operation of synchrotron light sources at high beam current. In this thesis, we have focused on this instability from a nonlinear dynamics point of view by combining experimental studies carried out at the Synchrotron Soleil and UVSOR storage rings with numerical studies mainly based on the Vlasov-Fokker-Planck equation. In a first step, due to the very indirect nature of the experimental observations, we have sought to deduce information on the microstructure wavenumber either by looking at the temporal evolution of the THz signal emitted during the instability or by studying the response of the electron bunch to a laser perturbation. In a second step, we have achieved direct, real time observations of the microstructures dynamics through two new, very different, detection techniques: a thin-film superconductor-based detector at UVSOR, and a spectrally-encoded electro-optic detection technique at Soleil. These new available experimental observations have allowed severe comparisons with the theoretical models. (author)

  11. Pharmacological modulation of the short-lasting effects of antagonistic direct current-stimulation over the human motor cortex

    Directory of Open Access Journals (Sweden)

    Leila eChaieb

    2012-07-01

    Full Text Available Combined administration of transcranial direct current stimulation (tDCS with either pergolide (PGL or D-cycloserine (D-CYC can prolong the excitability-diminishing effects of cathodal, or the excitability enhancing effect of anodal stimulation for up to 24hrs poststimulation. However, it remains unclear whether the potentiation of the observed aftereffects is dominated by the polarity and duration of the stimulation, or the dual application of combined stimulation and drug administration. The present study looks at whether the aftereffects of oral administration of PGL (a D1/D2 agonist or D-CYC (a partial NMDA receptor agonist, in conjunction with the short duration antagonistic application of tDCS (either 5 min cathodal followed immediately by 5 min anodal or vice versa, that alone only induces short lasting aftereffects, can modulate cortical excitability in healthy human subjects, as revealed by a single-pulse MEP (motor-evoked-potential paradigm. Results indicate that the antagonistic application of DC currents induces short-term neuroplastic aftereffects that are dependent upon the polarity of the second application of short-duration tDCS. The application of D-cycloserine resulted in a reversal of this trend and so consequently a marked inhibition of cortical excitability with the cathodal-anodal stimulation order was observed. The administration of pergolide showed no significant aftereffects in either case. These results emphasise that the aftereffects of tDCS are dependent upon the stimulation orientation, and mirror the findings of other studies reporting the neuroplasticity inducing aftereffects of tDCS, and their prolongation when combined with the administration of CNS active drugs.

  12. A low-cost non-intercepting beam current and phase monitor for heavy ions

    International Nuclear Information System (INIS)

    Bogaty, J.M.; Clifft, B.E.

    1995-01-01

    A low cost ion beam measurement system has been developed for use at ATLAS. The system provides nondestructive phase and intensity measurement of passing ion beam bunches by sensing their electric fields. Bunches traverse a short tubular electrode thereby inducing displacement currents. These currents are brought outside the vacuum jacket where a lumped inductance resonates electrode capacitance at one of the bunching harmonic frequencies. This configuration yields a basic sensitivity of a few hundred millivolts signal per microampere of beam current. Beam induced radiofrequency signals are summed against an offset frequency generated by the master oscillator. The resulting difference frequency conveys beam intensity and bunch phase information which is sent to separate processing channels. One channel utilizes a phase locked loop to stabilize phase readings during microsecond beam drop outs. The other channel uses a linear full-wave active rectifier circuit which converts sine wave signal amplitude to a DC voltage representing beam current. Plans are in progress to install this new diagnostic at several locations in ATLAS which should help shorten the tuning cycle of new ion species

  13. SHORT OVERVIEW OF CLINICAL TRIALS WITH CURRENT IMMUNOTHERAPEUTIC TOOLS FOR CANCER TREATMENT

    Directory of Open Access Journals (Sweden)

    T. S. Nepomnyashchikh

    2017-01-01

    Full Text Available Over last decade, a substantial progress has been made, with respect to understanding of cancer biology and its interplay with the host immune system. Different immunotherapeutic drugs based on recombinant cytokines and monoclonal antibodies are widely used in cancer therapy, and a large number of experimental cancer treatments have been developed, many of which are currently undergoing various stages of clinical trials. Recent endorsement of a recombinant oncolytic herpesvirus T-VEC for the treatment of melanoma was an important step towards a more safe and efficient anticancer therapeutics. In this review, we shall mention only some of the most promising cancer immunotherapy strategies, namely, immune checkpoint inhibitors, cellular therapy and oncolytic viruses. 

  14. Enhancement of short-circuit current density in polymer bulk heterojunction solar cells comprising plasmonic silver nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yuzhao; Lin, Xiaofeng; Ou, Jiemei; Chen, Xudong, E-mail: cescxd@mail.sysu.edu.cn, E-mail: stszx@mail.sysu.edu.cn, E-mail: chenyj69@mail.sysu.edu.cn [Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education of China, Sun Yat-sen University, Guangzhou 510275 (China); Qing, Jian; Zhong, Zhenfeng; Zhou, Xiang, E-mail: cescxd@mail.sysu.edu.cn, E-mail: stszx@mail.sysu.edu.cn, E-mail: chenyj69@mail.sysu.edu.cn; Chen, Yujie, E-mail: cescxd@mail.sysu.edu.cn, E-mail: stszx@mail.sysu.edu.cn, E-mail: chenyj69@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Hu, Chenglong [Key Laboratory of Optoelectronic Chemical Materials and Devices of Ministry of Education, Jianghan University, Wuhan 430056 (China)

    2014-03-24

    We demonstrate that the influence of plasmonic effects based on silver nanowires (Ag NWs) on the characteristics of polymer solar cells (PSCs). The solution-processed Ag NWs are situated at the interface of anode buffer layer and active layer, which could enhance the performance especially the photocurrent of PSCs by scattering, localized surface plasmon resonance, and surface plasmon polaritons. Plasmonic effects are confirmed by the enhancement of extinction spectra, external quantum efficiency, and steady state photoluminescence. Consequently, the short-circuit current density (J{sub sc}) and power conversion efficiency enhance about 24% and 18%, respectively, under AM1.5 illumination when Ag NWs plasmonic nanostructure incorporated into PSCs.

  15. Small-bandgap polymer solar cells with unprecedented short-circuit current density and high fill factor.

    Science.gov (United States)

    Choi, Hyosung; Ko, Seo-Jin; Kim, Taehyo; Morin, Pierre-Olivier; Walker, Bright; Lee, Byoung Hoon; Leclerc, Mario; Kim, Jin Young; Heeger, Alan J

    2015-06-03

    Small-bandgap polymer solar cells (PSCs) with a thick bulk heterojunction film of 340 nm exhibit high power conversion efficiencies of 9.40% resulting from high short-circuit current density (JSC ) of 20.07 mA cm(-2) and fill factor of 0.70. This remarkable efficiency is attributed to maximized light absorption by the thick active layer and minimized recombination by the optimized lateral and vertical morphology through the processing additive. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Gridded thermionic gun and integral superconducting ballistic bunch compression cavity

    Energy Technology Data Exchange (ETDEWEB)

    Schultheiss, Thomas [Advanced Energy Systems, Inc., Medford, NY (United States)

    2015-11-16

    Electron-Ion colliders such as the Medium energy Electron Ion Collider (MEIC) being developed by JLAB require high current electrons with low energy spread for electron cooling of the collider ring. Accelerator techniques for improving bunch charge, average current, emittance, and energy spread are required for Energy Recovery Linacs (ERLs) and Circulator Rings (CR) for next generation colliders for nuclear physics experiments. Example candidates include thermionic-cathode electron guns with RF accelerating structures. Thermionic cathodes are known to produce high currents and have excellent lifetime. The success of the IR and THz Free-Electron Laser (FEL) designed and installed by Advanced Energy Systems at the Fritz Haber Institute (FHI) of the Max Planck Society in Berlin [1,2] demonstrates that gridded thermionic cathodes and rf systems be considered for next generation collider technology. In Phase 1 Advanced Energy Systems (AES) developed and analyzed a design concept using a superconducting cavity pair and gridded thermionic cathode. Analysis included Beam Dynamics and thermal analysis to show that a design of this type is feasible. The latest design goals for the MEIC electron cooler were for electron bunches of 420 pC at a frequency of 952.6 MHz with a magnetic field on the cathode of 2kG. This field magnetizes the beam imparting angular momentum that provides for helical motion of the electrons in the cooling solenoid. The helical motion increases the interaction time and improves the cooling efficiency. A coil positioned around the cathode providing 2kG field was developed. Beam dynamics simulations were run to develop the particle dynamics near the cathode and grid. Lloyd Young added capability to Tstep to include space charge effects between two plates and include image charge effects from the grid. He also added new pepper-pot geometry capability to account for honeycomb grids. These additions were used to develop the beam dynamics for this gun. The

  17. Short-term and long-term Vadose zone monitoring: Current technologies, development, and applications

    International Nuclear Information System (INIS)

    Faybishenko, Boris

    1999-01-01

    At Hanford, Savannah River, Oak Ridge, Idaho National Engineering and Environmental Laboratory (INEEL), and other DOE sites, field vadose zone observations have shown complex water seepage and mass transport behavior in a highly heterogeneous, thick vadose zone on a variety of scales. Recent investigation showed that severe contamination of soils and groundwater by organic contaminant and nuclear waste occurred because of water seepage and contaminant transport along localized, preferential, fast flow within the heterogeneous vadose zone. However, most of the existing characterization and monitoring methods are not able to locate these localized and persistent preferential pathways associated with specific heterogeneous geologic features, such as clastic dikes, caliche layers, or fractures. In addition, changes in the chemical composition of moving and indigenous solutes, particularly sodium concentration, redox conditions, biological transformation of organic materials, and high temperature, may significantly alter water, chemicals, and bio-transformation exchange between the zones of fast flow and the rest of the media. In this paper, using the data from Hanford and INEEL sites, we will (1) present evidence that central problems of the vadose zone investigations are associated with preferential, fast flow phenomena and accelerated migration of organic and radioactive elements, (2) identify gaps in current characterization and monitoring technologies, and (3) recommend actions for the development of advanced vadose zone characterization and monitoring methods using a combination of hydrologic, geochemical, and geophysical techniques

  18. Influence of short-term solar disturbances on the fair weather conduction current

    Directory of Open Access Journals (Sweden)

    Elhalel Gal

    2014-01-01

    Full Text Available The fair weather atmospheric electrical current (Jz couples the ionosphere to the lower atmosphere and thus provides a route by which changes in solar activity can modify processes in the lower troposphere. This paper examines the temporal variations and spectral characteristics of continuous measurements of Jz conducted at the Wise Observatory in Mitzpe-Ramon, Israel (30°35′ N, 34°45′ E, during two large CMEs, and during periods of increased solar wind density. Evidence is presented for the effects of geomagnetic storms and sub-storms on low latitude Jz during two coronal mass ejections (CMEs, on 24–25th October 2011 and 7–8th March 2012, when the variability in Jz increased by an order of magnitude compared to normal fair weather conditions. The dynamic spectrum of the increased Jz fluctuations exhibit peaks in the Pc5 frequency range. Similar low frequency characteristics occur during periods of enhanced solar wind proton density. During the October 2011 event, the periods of increased fluctuations in Jz lasted for 7 h and coincided with fluctuations of the inter-planetary magnetic field (IMF detected by the ACE satellite. We suggest downward mapping of ionospheric electric fields as a possible mechanism for the increased fluctuations.

  19. The current and short term outlook for offshore exploration and development in the UK

    International Nuclear Information System (INIS)

    Precious, R.G.

    1992-01-01

    The United Kingdom offshore oil and gas industry began with the first North Sea discoveries in 1965. Of the total estimated hydrocarbon resources, 34% of the 32 billion bbl of oil and gas liquids and 23% of the 124 trillion ft 3 of natural gas have already been produced, and an additional 22% and 23% respectively are currently producing or under development. Average discovery size has declined as the region matures; nevertheless drilling activity has remained high. Low oil prices, increasing operating costs, and the worldwide recession have caused many companies to cut back on capital expenditures. The outlook for North Sea exploration is for smaller, more complex prospects and in areas with greater exploration potential. The outlook for development is for smaller, often economically marginal new fields and existing fields that are increasingly expensive to operate. In new fields, costs can be reduced by simplification and standardization of facilities, using horizontal drilling, lighter modular platforms, subsea technology, and multiphase pipelines. Examples of such developments at Shell/Esso's Osprey and Gannet fields are described. In existing fields, emphasis is on upgrading of facilites for extended field life; simplification and automation of facilities is also being carried out to reduce costs. Examples are provided from Shell/Esso's Brent and Leman fields. Other factors affecting future development are outlined. Total U.K. gas demand is forecast to rise to 7-8 billion ft 3 d by the late 1990s; imports may be required to meet total U.K. demand at that time. U.K. oil and liquids production is forecast to increase to a new peak of 2.7 million bbl/d in 1995. 13 figs

  20. Where current pharmacological therapies fall short in COPD: symptom control is not enough

    Directory of Open Access Journals (Sweden)

    N. Roche

    2007-09-01

    Full Text Available Chronic obstructive pulmonary disease (COPD is a common and progressive condition that is currently the fourth leading cause of death worldwide. There is now a large body of evidence indicating that both pulmonary and systemic inflammation are present in patients with stable COPD and may underlie both respiratory symptoms and common comorbidities of this disease. Smoking cessation and long-term oxygen therapy have been shown to change the course of COPD and recent results obtained with the combination of fluticasone and salmeterol have indicated that it could decrease mortality and slow the decline in lung function in patients with this disease. However, some pharmacological treatments can significantly improve dyspnoea, exercise tolerance, limitations in activity, rate of exacerbations and quality of life (e.g. long-acting bronchodilators and inhaled corticosteroids combined with a long-acting beta2-agonist. The ability of these agents to modify the rate of disease progression remains to be firmly established in large-scale, long-term trials. The concept of disease modification itself in COPD may need to be revisited and more precisely defined in terms of markers and clinical outcomes, including extrarespiratory manifestations: agents that durably affect symptoms, activities, exacerbations and quality of life should probably be considered as disease modifiers. It is also reasonable to suggest that early diagnosis and treatment of patients with COPD might be the first and potentially most important disease-modifying intervention. There is clearly a need for new therapies that directly target the specific inflammatory processes underlying chronic obstructive pulmonary disease and its pulmonary and extrapulmonary manifestations.

  1. More Options for the NLC Bunch Compressors (LCC-0035)

    International Nuclear Information System (INIS)

    Emma, P.

    2004-01-01

    The present bunch compressor design for the NLC allows control of the final bunch length by way of changes to the horizontal betatron phase advance of the 180 o -turnaround arc. This adjustability requirement significantly constrains the design and cost optimization of the system and excludes the possibility of using permanent magnet quadrupoles in the arc. To relieve this constraint, and to avoid the very strong arc focusing required at the upper limits of the bunch length range, we explore an option of bunch length control using the first compressor stage, with the arc optics fixed

  2. Ply tensile properties of banana stem and banana bunch fibres

    African Journals Online (AJOL)

    2012-03-01

    Mar 1, 2012 ... BANANA BUNCH FIBRES REINFORCED NATURAL RUBBER. COMPOSITE ... National Institute for Interdisciplinary Science and Technology, (NIIST) CSIR Trivandrum, India. ..... Handbook of Ceramics and Composites,. Vol.

  3. Bunch length measurements in the SLC damping ring

    International Nuclear Information System (INIS)

    Decker, F.J.; Limberg, T.; Minty, M.; Ross, M.

    1993-05-01

    The synchrotron light of the SLC damping ring was used to measure the bunch length with a streak camera at different times in the damping cycle. There are bunch length oscillations after injection, different equilibrium length during the cycle due to rf manipulations to avoid microwave instability oscillations, and just before extraction there is a longitudinal phase space rotation (bunch muncher) to shorten the bunch length. Measurements under these different conditions are presented and compared with BPM pulse height signals. Calibration and adjustment issues and the connection of the streak camera to the SLC control system are also discussed

  4. POSITION DETERMINATION OF CLOSELY SPACED BUNCHES USING CAVITY BPMs

    CERN Document Server

    Joshi, N; Cullinan, F; Lyapin, A

    2011-01-01

    Radio Frequency (RF) Cavity Beam Position Monitor (BPM) systems form a major part of precision position measurement diagnostics for linear accelerators with low emittance beams. Using cavity BPMs, a position resolution of less than 100 nm has been demonstrated in single bunch mode operation. In the case of closely spaced bunches, where the decay time of the cavity is comparable to the time separation between bunches, the BPM signal from a bunch is polluted by the signal induced by the previous bunches in the same bunch-train. This paper discusses our ongoing work to develop the methods to extract the position of closely spaced bunches using cavity BPMs. A signal subtraction code is being developed to remove the signal pollution from previous bunches and to determine the individual bunch position. Another code has been developed to simulate the BPM data for the cross check. Performance of the code is studied on the experimental and simulated data. Application of the analysis techniques to the linear colliders,...

  5. Commissioning of FPGA-based Transverse and Longitudinal Bunch-by-Bunch Feedback System for the TLS

    International Nuclear Information System (INIS)

    Hu, K. H.; Kuo, C. H.; Lau, W. K.; Yeh, M. S.; Hsu, S. Y.; Chou, P. J.; Wang, M. H.; Lee, Demi; Chen, Jenny; Wang, C. J.; Hsu, K. T.; Kobayashi, K.; Nakamura, T.; Dehler, M.

    2006-01-01

    Multi-bunch instabilities deteriorate beam quality, increasing beam emittance, or even causing beam loss in the synchrotron light source. The feedback system is essential to suppress multi-bunch instabilities caused by the impedances of beam ducts, and trapped ions. A new FPGA based transverse and longitudinal bunch-by-bunch feedback system have been commissioned at the Taiwan Light Source recently, A single feedback loop is used to simultaneously suppress the horizontal and the vertical multi-bunch instabilities. Longitudinal instabilities caused by cavity-like structures are suppressed by the longitudinal feedback loop. The same FPGA processor is employed in the transverse feedback and the longitudinal feedback system respectively. Diagnostic memory is included in the system to capture the bunch oscillation signal, which supports various studies

  6. Analyzing gigahertz bunch length instabilities with a digital signal processor

    International Nuclear Information System (INIS)

    Stege, R.E. Jr.; Krejcik, P.; Minty, M.G.

    1992-11-01

    A bunch length instability, nicknamed the ''sawtooth'', because of its transient behavior, has been observed at high current running in the Stanford Linear Collider (SLC) electron damping ring. The incompatibility of this instability with successful SLC naming prompted its study using a high bandwidth real-time spectrum analyzer, the Tektronix 3052 digital signal processor (DSP) system. This device has been used to study energy ramping in storage rings but this is the first time it has been used to study transient instability phenomena. It is a particularly valuable tool for use in understanding non-linear, multiple frequency phenomena. The frequency range of this device has been extended through the use of radio frequency (RF) down converters. This paper describes the measurement setup and presents some of the results

  7. Electron bunch compression and coherent effects at the SDL

    International Nuclear Information System (INIS)

    Loos, Henrik; Carr, G. Lawrence; Doyuran, Adnan; Graves, William S.; Johnson, Eric D.; Krinsky, Samuel; Rose, James; Sheehy, Brian; Shaftan, Timur V.; Skaritka, John; Yu Lihua

    2002-01-01

    The DUVFEL accelerator in the Source Development Lab of NSLS/BNL generates a high brightness electron beam from a laser driven electron source and a magnetic bunch compressor. This beam is used for different FEL experiments in SASE and future HGHG configurations. The compression of the electron beam to high peak current while preserving the transverse properties is of great importance to the performance goals of these FELs. In this paper we report on the experimental methods to characterize the longitudinal properties of the electron beam and the measured results for various settings of the DUVFEL accelerator. The observed effects on the electron beam spectra and time profiles during compression are most likely due to coherent effects while their exact origin is still subject of ongoing investigation

  8. Phase measurement and control of bunched beams

    International Nuclear Information System (INIS)

    Lewis, R.N.

    1978-01-01

    An ion bean buncher was developed at ANL for bunching all ion species through a tandem accelerator. Transit time variations through the tandem, caused by ripple and fluctuations in the injection and lens power supplies and terminal voltage, and to varying voltage distributions in the accelerating tube, cause a beam-phase variation at the output of the tandem. A beam-phase measurement and control system was designed and installed in conjunction with the ion beam buncher to control beam phase at the tandem output. That system is described

  9. Condition for a single bunch high frequency fast blow-up

    International Nuclear Information System (INIS)

    Wang, J.M.; Pellegrini, C.

    1980-01-01

    We study the longitudinal stability of a single particle bunch in a storage ring using Vlasov equation. We show that the Vlasov equation has solutions corresponding to a fast, microwave instability if a condition on the beam current, qualitatively similar to the stability condition for a coasting beam, is satisfied. This condition can be used to define a threshold current, and to discuss its dependence on the longitudinal coupling impedance

  10. On bunch lengthening using the fourth harmonic cavity in the NSLS VUV ring

    International Nuclear Information System (INIS)

    Wachtel, J.M.

    1988-02-01

    It has been suggested that the phase of the beam excited voltage in the harmonic cavity can be controlled by detuning its resonant frequency from the beam current harmonic. Unfortunately the detuning needed to flatten the acceleration waveform also corresponds to the region of Robinson instability for the harmonic cavity. Therefore, lengthening the bunch may be followed by large amplitude synchrotron oscillation of the bunch center of mass. Bunch lengthening is discussed in this note from several points of view. There follows a simple review of single electron oscillations in a quartic potential. Then equations are developed for the coupled oscillations of a cavity and a rigid bunch as a fully nonlinear, time dependent initial value problem. Next, a computer program that solves these equations for one, two or more cavities, with and without externally driven fields, is described and some simulations of the harmonic cavity interaction are shown. Finally, the fully nonlinear equations are linearized to derive a dispersion relation for the case of beam excitation in the harmonic cavity. 6 refs., 5 figs

  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. Negative-mass mitigation of Coulomb repulsion for terahertz undulator radiation of electron bunches

    Energy Technology Data Exchange (ETDEWEB)

    Balal, N.; Magory, E. [Ariel University, Ariel 40700 (Israel); Bandurkin, I. V. [Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Bratman, V. L. [Ariel University, Ariel 40700 (Israel); Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Savilov, A. V. [Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 23 Gagarin Avenue, Nizhny Novgorod 603950 (Russian Federation)

    2015-10-19

    It is proposed to utilize the effect of negative mass for stabilization of the effective axial size of very dense and short electron bunches produced by photo-injector guns by using combined undulator and strong uniform magnetic fields. It has been shown that in the “abnormal” regime, an increase in the electron energy leads to a decrease in the axial velocity of the electron; due to the negative-mass effect, the Coulomb repulsion of electrons leads to their attraction and formation of a fairly stable and compact bunch “nucleus.” An undulator with a strong uniform magnetic field providing the negative-mass effect is designed for an experimental source of terahertz radiation. The use of the negative-mass regime in this experiment should result in a long-pulse coherent spontaneous undulator emission from a short dense moderately relativistic (5.5 MeV) photo-injector electron bunch with a high (up to 20%) efficiency and a narrow frequency spectrum.

  13. 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.

  14. RF acceleration of intense laser generated proton bunches

    Energy Technology Data Exchange (ETDEWEB)

    Almomani, Ali

    2012-07-13

    With respect to laser-accelerated beams, the high current capability of the CH-DTL cavity has been investigated. Beam simulations have demonstrated that 10{sup 10} protons per bunch can be accelerated successfully and loss free along the structure. It was shown that, the maximum number of protons per bunch that can be accelerated in the first cavity by exploiting about 1% of the stored field energy is 2.02 x 10{sup 11} protons. One further aspect is the total number of protons arriving at the linac entrance. One main aspect of an rf postacceleration experiment is the rf operation stability under these beam load conditions. Detailed simulations from the target along the solenoid and down to the linac entrance were presented, applying adapted software. Special care was taken on the time steps, especially close to the target, and on the collective phenomena between electron and proton distributions. The effect of comoving electrons on the beam dynamics has been investigated in detail. A CH-linac with high space charge limit and large transverse and longitudinal acceptance was designed to accept a maximum fraction of the laser generated proton bursts. Due to well-known transformations of the injected beam emittances along the CH-cavity, it is aimed to derive parameters of the laser generated beam by measuring the beam properties behind of the CH-cavity. With respect to the linac development it is intended to realize the first cavity of the proposed CH-DTL and to demonstrate the acceleration of a laser generated proton bunch with the LIGHT project. The first cavity consists of 7 gaps within a total length of about 668 mm. It is operated at 325 MHz and has an effective accelerating field gradient of about 12.6 MV/m. The study on the surface electric field for this cavity shows, that maximum surface fields of about 94 MV/m and 88 MV/m on the third and sixth drift tubes are reachable, respectively.

  15. Tensile Mechanical Property of Oil Palm Empty Fruit Bunch Fiber Reinforced Epoxy Composites

    Science.gov (United States)

    Ghazilan, A. L. Ahmad; Mokhtar, H.; Shaik Dawood, M. S. I.; Aminanda, Y.; Ali, J. S. Mohamed

    2017-03-01

    Natural, short, untreated and randomly oriented oil palm empty fruit bunch fiber reinforced epoxy composites were manufactured using vacuum bagging technique with 20% fiber volume composition. The performance of the composite was evaluated as an alternative to synthetic or conventional reinforced composites. Tensile properties such as tensile strength, modulus of elasticity and Poisson’s ratio were compared to the tensile properties of pure epoxy obtained via tensile tests as per ASTM D 638 specifications using Universal Testing Machine INSTRON 5582. The tensile properties of oil palm empty fruit bunch fiber reinforced epoxy composites were lower compared to plain epoxy structure with the decrement in performances of 38% for modulus of elasticity and 61% for tensile strength.

  16. On some properties of longitudinal and transverse coupled-bunch instabilities

    International Nuclear Information System (INIS)

    Kamiya, Yukihide.

    1983-02-01

    Some properties of longitudinal and transverse coupled-bunch instabilities have been investigated theoretically and computationally, mainly based on a rigid-bunch model. In this report, we will study Robinson's stability, sum rules of the instabilities and the cure of instabilities by producing the oscillation frequencies different from bunch to bunch, and also give the numerical examples for KEK-PF storage ring. KEYWORD: storage ring, accelerator, bunched beam, longitudinal instability, transverse instability, coupled-bunch instability. (author)

  17. Short- and long-term inhibition of cardiac inward-rectifier potassium channel current by an antiarrhythmic drug bepridil.

    Science.gov (United States)

    Ma, Fangfang; Takanari, Hiroki; Masuda, Kimiko; Morishima, Masaki; Ono, Katsushige

    2016-07-01

    Bepridil is an effective antiarrhythmic drug on supraventricular and ventricular arrhythmias, and inhibitor of calmodulin. Recent investigations have been elucidating that bepridil exerts antiarrhythmic effects through its acute and chronic application for patients. The aim of this study was to identify the efficacy and the potential mechanism of bepridil on the inward-rectifier potassium channel in neonatal rat cardiomyocytes in acute- and long-term conditions. Bepridil inhibited inward-rectifier potassium current (I K1) as a short-term effect with IC50 of 17 μM. Bepridil also reduced I K1 of neonatal cardiomyocytes when applied for 24 h in the culture medium with IC50 of 2.7 μM. Both a calmodulin inhibitor (W-7) and an inhibitor of calmodulin-kinase II (KN93) reduced I K1 when applied for 24 h as a long-term effect in the same fashion, suggesting that the long-term application of bepridil inhibits I K1 more potently than that of the short-term application through the inhibition of calmodulin kinase II pathway in cardiomyocytes.

  18. 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.

  19. 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.

  20. 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 ...

  1. 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...

  2. 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....

  3. Production of Mineral Water Using Palm Bunch Ash (PBA) From ...

    African Journals Online (AJOL)

    A public health strategy for increasing the potassium and magnesium intake of the population was explored. These electrolytes have been confirmed by epidemiological studies to have some health benefits. A process for production of mineral water using palm bunch ash was developed. The composition of the palm bunch ...

  4. 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.

  5. Simulation of the longitudinal instabilities of the asymmetric bunches

    International Nuclear Information System (INIS)

    Dai Jianping; Zhao Zhentang

    2002-01-01

    The computational model of the code used to simulate the longitudinal instabilities of the asymmetric bunches was introduced. The growth rates of the longitudinal instabilities of the symmetric bunches got by this code were compared with those got by the code ZAP, and they were almost the same. As an example, the simulation results of the BEPC-II were presented

  6. Laser induced non-monotonic degradation in short-circuit current of triple-junction solar cells

    Science.gov (United States)

    Dou, Peng-Cheng; Feng, Guo-Bin; Zhang, Jian-Min; Song, Ming-Ying; Zhang, Zhen; Li, Yun-Peng; Shi, Yu-Bin

    2018-06-01

    In order to study the continuous wave (CW) laser radiation effects and mechanism of GaInP/GaAs/Ge triple-junction solar cells (TJSCs), 1-on-1 mode irradiation experiments were carried out. It was found that the post-irradiation short circuit current (ISC) of the TJSCs initially decreased and then increased with increasing of irradiation laser power intensity. To explain this phenomenon, a theoretical model had been established and then verified by post-damage tests and equivalent circuit simulations. Conclusion was drawn that laser induced alterations in the surface reflection and shunt resistance were the main causes for the observed non-monotonic decrease in the ISC of the TJSCs.

  7. Current status and a short history of grey literature. Focusing on the international conference on grey literature

    International Nuclear Information System (INIS)

    Ikeda, Kiyoshi

    2010-01-01

    'Grey literature' is a loosely defined term whose application is rather complex, but it is also an important source of information for academic researchers. Today, the spread of the Internet has led to changes not only in the circulation but also in the role and definition of 'grey literature'. This article therefore presents a short history of the definition of 'grey literature', with central focus on topics discussed by the International Conference on Grey Literature. After this, the current status and future prospects of 'grey literature' in the digital society are described. Finally, the article introduces the JAEA Library's activities on 'grey literature', particularly the acquisition of proceedings and the editing and dissemination of the JAEA Reports (technical reports of JAEA). (author)

  8. Transcranial direct current stimulation improves short-term memory in an animal model of attention-deficit/hyperactivity disorder.

    Science.gov (United States)

    Leffa, Douglas Teixeira; de Souza, Andressa; Scarabelot, Vanessa Leal; Medeiros, Liciane Fernandes; de Oliveira, Carla; Grevet, Eugenio Horacio; Caumo, Wolnei; de Souza, Diogo Onofre; Rohde, Luis Augusto Paim; Torres, Iraci L S

    2016-02-01

    Attention deficit hyperactivity disorder (ADHD) is characterized by impairing levels of hyperactivity, impulsivity and inattention. However, different meta-analyses have reported disruptions in short and long-term memory in ADHD patients. Previous studies indicate that mnemonic dysfunctions might be the result of deficits in attentional circuits, probably due to ineffective dopaminergic modulation of hippocampal synaptic plasticity. In this study we aimed to evaluate the potential therapeutic effects of a neuromodulatory technique, transcranial direct current stimulation (tDCS), in short-term memory (STM) deficits presented by the spontaneous hypertensive rats (SHR), the most widely used animal model of ADHD. Adult male SHR and Wistar Kyoto rats (WKY) were subjected to a constant electrical current of 0.5 mA intensity applied on the frontal cortex for 20 min/day during 8 days. STM was evaluated with an object recognition test conducted in an open field. Exploration time and locomotion were recorded, and brain regions were dissected to determine dopamine and BDNF levels. SHR spent less time exploring the new object when compared to WKY, and tDCS improved object recognition deficits in SHR without affecting WKY performance. Locomotor activity was higher in SHR and it was not affected by tDCS. After stimulation, dopamine levels were increased in the hippocampus and striatum of both strains, while BDNF levels were increased only in the striatum of WKY. These findings suggest that tDCS on the frontal cortex might be able to improve STM deficits present in SHR, which is potentially related to dopaminergic neurotransmission in the hippocampus and striatum of those animals. Copyright © 2016. Published by Elsevier B.V.

  9. Longitudinal Bunch Position Control for the Super-B Accelerator

    International Nuclear Information System (INIS)

    Bertsche, Kirk; Rivetta, Claudio; Sullivam, Michael K.; SLAC; Drago, Alessandro; Frascati

    2009-01-01

    The use of normal conducting cavities and an ion-clearing gap will cause a significant RF accelerating voltage gap transient and longitudinal phase shift of the individual bunches along the bunch train in both rings of the SuperB accelerator. Small relative centroid position shifts between bunches of the colliding beams will have a large adverse impact on the luminosity due to the small β* y at the interaction point (IP). We investigate the possibility of minimizing the relative longitudinal position shift between bunches by reducing the gap transient in each ring and matching the longitudinal bunch positions of the two rings at the IP using feedback/feedforward techniques in the LLRF. The analysis is conducted assuming maximum use of the klystron power installed in the system

  10. A bunch clock for the Advanced Photon Source

    International Nuclear Information System (INIS)

    Lenkszus, F.R.; Laird, R.J.

    1997-01-01

    A bunch clock timing module has been developed for use by Advanced Photon Source beamlines. The module provides bunch pattern and timing information that can be used to trigger beamline data collection equipment. The module is fully integrated into the control system software (EPICS) which automatically loads it with the storage ring fill pattern at injection time. Fast timing outputs (1 ns FWHM) for each stored bunch are generated using the storage ring low-level rf and revolution clock as input references. Fiber-optic-based transmitters and receivers are used to transmit a 352-MHz low-level rf reference to distributed bunch clock modules. The bunch clock module is a single-width VME module and may be installed in a VME crate located near beamline instrumentation. A prototype has been in use on the SRI CAT beamline for over a year. The design and integration into the control system timing software along with measured performance results are presented

  11. Effects of bunch rot (Botrytis cinerea) and powdery mildew (Erysiphe necator) fungal diseases on wine aroma

    Science.gov (United States)

    Lopez Pinar, Angela; Rauhut, Doris; Ruehl, Ernst; Buettner, Andrea

    2017-03-01

    This study aimed to characterize the effects of bunch rot and powdery mildew on the primary quality parameter of wine, the aroma. The influence of these fungal diseases was studied by comparative Aroma Extract Dilution Analyses (AEDA) and sensory tests. The effect of bunch rot was investigated on three grape varieties, namely White Riesling, Red Riesling and Gewürztraminer and that of powdery mildew on the hybrid Gm 8622-3; thereby, samples were selected that showed pronounced cases of infection to elaborate potential currently unknown effects. Both infections revealed aromatic differences induced by these fungi. The sensory changes were not associated with one specific compound only, but were due to quantitative variations of diverse substances. Bunch rot predominantly induced an increase in the intensities of peach-like/fruity, floral and liquor-like/toasty aroma notes. These effects were found to be related to variations in aroma substance composition as monitored via AEDA, mainly an increase in the FD factors of lactones and a general moderate increase of esters and alcohols. On the other hand, powdery mildew decreased the vanilla-like character of the wine while the remaining sensory attributes were rather unaffected. Correspondingly, FD factors of the main aroma constituents were either the same or only slightly modified by this disease. Moreover, bunch rot influenced the aroma profiles of the three varieties studied to a different degree. In hedonic evaluation, bunch rot-affected samples were rated as being more pleasant in comparison to their healthy controls in all three varieties while the powdery mildew-affected sample was rated as being less pleasant than its healthy control.

  12. Simulations of the ILC Electron Gun and Electron Bunching System

    International Nuclear Information System (INIS)

    Haakonsen, C.B.; McGill U.

    2006-01-01

    The International Linear Collider (ILC) is a proposed electron-positron collider, expected to provide insight into important questions in particle physics. A part of the global R and D effort for the ILC is the design of its electron gun and electron bunching system. The present design of the bunching system has two sub-harmonic bunchers, one operating at 108 MHz and one at 433MHz, and two 5-cell 1.3 GHz (L-band) bunchers. This bunching system has previously been simulated using the Phase and Radial Motion in Electron Linear Accelerators (PARMELA) software, and those simulations indicated that the design provides sufficient bunching and acceleration. Due to the complicated dynamics governing the electrons in the bunching system we decided to verify and expand the PARMELA results using the more recent and independent simulation software General Particle Tracer (GPT). GPT tracks the motion and interactions of a set of macro particles, each of which represent a number of electrons, and provides a variety of analysis capabilities. To provide initial conditions for the macro particles, a method was developed for deriving the initial conditions from detailed simulations of particle trajectories in the electron gun. These simulations were performed using the Egun software. For realistic simulation of the L-band bunching cavities, their electric and magnetic fields were calculated using the Superfish software and imported into GPT. The GPT simulations arrived at similar results to the PARMELA simulations for sub-harmonic bunching. However, using GPT it was impossible to achieve an efficient bunching performance of the first L-band bunching cavity. To correct this, the first L-band buncher cell was decoupled from the remaining 4 cells and driven as an independent cavity. Using this modification we attained results similar to the PARMELA simulations. Although the modified bunching system design performed as required, the modifications are technically challenging to implement

  13. Bunch mode specific rate corrections for PILATUS3 detectors

    Energy Technology Data Exchange (ETDEWEB)

    Trueb, P., E-mail: peter.trueb@dectris.com [DECTRIS Ltd, 5400 Baden (Switzerland); Dejoie, C. [ETH Zurich, 8093 Zurich (Switzerland); Kobas, M. [DECTRIS Ltd, 5400 Baden (Switzerland); Pattison, P. [EPF Lausanne, 1015 Lausanne (Switzerland); Peake, D. J. [School of Physics, The University of Melbourne, Victoria 3010 (Australia); Radicci, V. [DECTRIS Ltd, 5400 Baden (Switzerland); Sobott, B. A. [School of Physics, The University of Melbourne, Victoria 3010 (Australia); Walko, D. A. [Argonne National Laboratory, Argonne, IL 60439 (United States); Broennimann, C. [DECTRIS Ltd, 5400 Baden (Switzerland)

    2015-04-09

    The count rate behaviour of PILATUS3 detectors has been characterized for seven bunch modes at four different synchrotrons. The instant retrigger technology of the PILATUS3 application-specific integrated circuit is found to reduce the dependency of the required rate correction on the synchrotron bunch mode. The improvement of using bunch mode specific rate corrections based on a Monte Carlo simulation is quantified. PILATUS X-ray detectors are in operation at many synchrotron beamlines around the world. This article reports on the characterization of the new PILATUS3 detector generation at high count rates. As for all counting detectors, the measured intensities have to be corrected for the dead-time of the counting mechanism at high photon fluxes. The large number of different bunch modes at these synchrotrons as well as the wide range of detector settings presents a challenge for providing accurate corrections. To avoid the intricate measurement of the count rate behaviour for every bunch mode, a Monte Carlo simulation of the counting mechanism has been implemented, which is able to predict the corrections for arbitrary bunch modes and a wide range of detector settings. This article compares the simulated results with experimental data acquired at different synchrotrons. It is found that the usage of bunch mode specific corrections based on this simulation improves the accuracy of the measured intensities by up to 40% for high photon rates and highly structured bunch modes. For less structured bunch modes, the instant retrigger technology of PILATUS3 detectors substantially reduces the dependency of the rate correction on the bunch mode. The acquired data also demonstrate that the instant retrigger technology allows for data acquisition up to 15 million photons per second per pixel.

  14. Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields

    Science.gov (United States)

    Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei

    2018-01-01

    High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (Hc2) and critical temperature (Tc). The critical current (Ic) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new Ic measurement system that can carry out accurate Ic measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The Ic measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa2Cu3O7-x(YBCO) tapes Ic determination with different temperatures and magnetic fields.

  15. Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields.

    Science.gov (United States)

    Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei

    2018-01-01

    High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (H c2 ) and critical temperature (T c ). The critical current (I c ) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new I c measurement system that can carry out accurate I c measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The I c measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa 2 Cu 3 O 7-x (YBCO) tapes I c determination with different temperatures and magnetic fields.

  16. Demonstration of cathode emittance dominated high bunch charge beams in a DC gun-based photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Gulliford, Colwyn, E-mail: cg248@cornell.edu; Bartnik, Adam, E-mail: acb20@cornell.edu; Bazarov, Ivan; Dunham, Bruce; Cultrera, Luca [CLASSE, Cornell University, 161 Synchrotron Drive Ithaca, New York 14853-8001 (United States)

    2015-03-02

    We present the results of transverse emittance and longitudinal current profile measurements of high bunch charge (≥100 pC) beams produced in the DC gun-based Cornell energy recovery linac photoinjector. In particular, we show that the cathode thermal and core beam emittances dominate the final 95% and core emittances measured at 9–9.5 MeV. Additionally, we demonstrate excellent agreement between optimized 3D space charge simulations and measurement, and show that the quality of the transverse laser distribution limits the optimal simulated and measured emittances. These results, previously thought achievable only with RF guns, demonstrate that DC gun based photoinjectors are capable of delivering beams with sufficient single bunch charge and beam quality suitable for many current and next generation accelerator projects such as Energy Recovery Linacs and Free Electron Lasers.

  17. Little field evidence of direct acute and short-term effects of current pesticides on the grey partridge.

    Science.gov (United States)

    Millot, Florian; Berny, Philippe; Decors, Anouk; Bro, Elisabeth

    2015-07-01

    Direct lethal and sublethal effects of pesticides on farmland birds' populations are recurring questions and largely debated. In this context, we conducted an innovative study combining radiotelemetry, farmer surveys, residue analyses on carcasses and modelling to assess the unintentional effects of pesticides on terrestrial birds. We chose the grey partridge Perdix perdix as a case study because this typical bird of European cereal ecosystems is highly exposed to pesticides. In this paper we focused on acute and short-term impacts of pesticides on adult mortality during spring and summer in a one-substance approach (multiple exposure were not studied here) but for a large variety of active substances (a.s.) actually used in cultivated farmland of Northern France. The fate and the location of 529 partridges were monitored twice a day from early March to late August 2010 and 2011 on 12 sites (14,500 ha). Their daily potential exposure to 183 a.s. was determined by overlapping birds' habitat use and daily pesticide application data. Based on this procedure, we calculated mortality rates within 10 days following a potential exposure for 157 different a.s.. 5 a.s. were associated with a "10-day mortality rate" higher than 10% but a single one (thiacloprid) is reported to be highly toxic to birds. We recorded 261 mortalities among which 94 carcasses were in suitable condition for residue analyses. We detected at least one a.s in 39.4% of carcasses. However, only 2 mortality cases were attributed to poisoning (carbofuran). Furthermore, modelling results showed that these lethal pesticide-related poisonings decreased the population growth rate by less than 1%. In conclusion, we did not point out important direct acute and short-term effects of pesticides currently used by farmers during the breeding season on the grey partridge. This is discussed with regards to the complexity of potential effects in operational conditions. Copyright © 2015 Elsevier Inc. All rights

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

    Directory of Open Access Journals (Sweden)

    J. G. H. Franssen

    2017-07-01

    Full Text Available 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.

  19. Emittance growth due to static and radiative space charge forces in an electron bunch compressor

    CERN Document Server

    Talman, Richard; Stulle, Frank

    2009-01-01

    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 (2004); 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 (2000)] and elegant [M. Borland, Argonne National Laboratory...

  20. Analytical model and error analysis of arbitrary phasing technique for bunch length measurement

    Science.gov (United States)

    Chen, Qushan; Qin, Bin; Chen, Wei; Fan, Kuanjun; Pei, Yuanji

    2018-05-01

    An analytical model of an RF phasing method using arbitrary phase scanning for bunch length measurement is reported. We set up a statistical model instead of a linear chirp approximation to analyze the energy modulation process. It is found that, assuming a short bunch (σφ / 2 π → 0) and small relative energy spread (σγ /γr → 0), the energy spread (Y =σγ 2) at the exit of the traveling wave linac has a parabolic relationship with the cosine value of the injection phase (X = cosφr|z=0), i.e., Y = AX2 + BX + C. Analogous to quadrupole strength scanning for emittance measurement, this phase scanning method can be used to obtain the bunch length by measuring the energy spread at different injection phases. The injection phases can be randomly chosen, which is significantly different from the commonly used zero-phasing method. Further, the systematic error of the reported method, such as the influence of the space charge effect, is analyzed. This technique will be especially useful at low energies when the beam quality is dramatically degraded and is hard to measure using the zero-phasing method.

  1. 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.)

  2. Investigation of the phase space distribution of electron bunches at the FLASH-linac using a transverse deflecting structure

    International Nuclear Information System (INIS)

    Roehrs, M.

    2008-06-01

    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 μm (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 μm. 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.)

  3. Bunching and phase focusing of laser generated proton beams

    Energy Technology Data Exchange (ETDEWEB)

    Schumacher, Dennis; Hofmann, Ingo; Blazevic, Abel; Deppert, Oliver [GSI Helmholtzzentrum fuer Schwerionenforschung (Germany); Busold, Simon; Roth, Markus; Boine-Frankenheim, Oliver [TU Darmstadt (Germany); Brabetz, Christian [Universitaet Frankfurt, Frankfurt am Main (Germany); Zielbauer, Bernhard [HI Jena (Germany); Collaboration: LIGHT-Collaboration

    2013-07-01

    Laser accelerated proton beams can reach very high intensities and very low emittances. Therefore they are suitable as ion sources for many applications. One is the coupling into common ion accelerator structures to replace pre accelerators that are used so far. The LIGHT (Laser Ion Generation, Handling and Transport) collaboration has been founded to develop ion optics and targets and optimize laser parameter to make this coupling most efficient. In a first step a short pulse beam line for the PHELIX-laser at GSI to the experiment site Z6 has been build in order to laser accelerate protons here. In a second step a pulsed solenoid has been established to collimate the divergent ion beam. In a third step this collimated beam will be coupled into a bunching unit, which consists of a spiral resonator with three gaps which leads to an overall acceleration voltage of 1 MV. With this cavity it is not only possible to avoid the broadening of the pulse, but also to phase focus it. This talk presents also the progress towards the operation of the spiral resonator as buncher for a laser accelerated ion beam e.g. simulations, tests and performance data and shows the next steps of the beam shaping efforts.

  4. A longitudinal bunch monitoring system using LabVIEW reg-sign and high-speed oscilloscopes

    International Nuclear Information System (INIS)

    Barsotti, E.L.

    1994-10-01

    A new longitudinal bunch monitoring system has been installed at Fermilab for the Tevatron and Main Ring. For each machine, a signal from a broadband wall current monitor is sampled and digitized by a high-speed oscilloscope. A Macintosh computer, running LabVIEW-based software, controls the scopes and CAMAC timing modules and analyzes the acquired data. The resulting bunch parameters are used for a variety of purposes, including Tevatron collider luminosity calculation and injection analysis. This paper examines the system in detail

  5. 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.

  6. Mode-coupling theory and bunch lengthening in SPEAR II

    International Nuclear Information System (INIS)

    Suzuki, T.; Chin, Y.; Satoh, K.

    1983-01-01

    A mode-coupling theory of bunched-beam instabilities is developed for a Gaussian bunch. The theory converts Sacherer's integral equation with mode coupling into a matrix eigenvalue problem. The present theory assumes well-defined azimuthal modes and takes into account radial modes which are expressed as superpositions of orthogonal functions. The theory is applied to bunch lengthening observed at SPEAR II. The theory explains qualitative features of the experimental results fairly well, but quantitative agreement is not too good. This is ascribed to insufficient knowledge of the coupling impedance of SPEAR II or to the possibility that such effects as radiation damping and quantum excitation should be included. (author)

  7. Multiple bunch-splitting in the PS results and plans

    CERN Document Server

    Garoby, R

    2001-01-01

    The nominal longitudinal characteristics of the PS proton beam for the LHC were attained during the year 2000, using a sequence of triple- and double-splittings to divide each PS Booster (PSB) bunch into 12. This method minimizes longitudinal emittance blow-up and preserves a gap, free of particles, in the bunch train. Some of the ideas for alternative bunch trains have also been tested. The performance achieved is described and the sources of limitations are discussed together with the foreseen improvements.

  8. Developing electron beam bunching technology for improving light sources

    International Nuclear Information System (INIS)

    Carlsten, B.E.; Chan, K.C.D.; Feldman, D.W.

    1997-01-01

    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

  9. Electron Bunch Length Diagnostic With Coherent Smith-Purcell Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, D.C.

    1997-05-12

    The authors have designed a new technique for measuring subpicosecond electron bunch lengths using coherent Smith-Purcell radiation. This new diagnostic technique involves passing the electron beam in close proximity of a grating with a period comparable to the electron bunch length. The emitted Smith-Purcell radiation will have a coherent component whose angular position and distribution are directly related to the electron bunch length and longitudinal profile, respectively. This new diagnostic technique is inherently simple, inexpensive and non-intercepting. The authors show that the new technique is also scaleable to femtosecond regime.

  10. Function of bunching segment in multi-cell RF gun

    International Nuclear Information System (INIS)

    Yang Xingfan; Xu Zhou Liu Xisan

    2001-01-01

    With a bunching segment and a shortened first cell, the 4 + 1/2 cell RF gun produced in CAEP has been proved experimentally to be effective in reducing electron back bombardment. The analysis of the electric field distribution and electron motion in bunching segment of multi-cell RF gun is presented. The electron capture efficiency and electron trajectory with different initial phase are calculated using Runge-Kutta method. The function of the bunching segment is discussed. The calculated parameters of the 4 + 1/2 cell RF gun agree well with the experimental results

  11. Transverse-Longitudinal Coupling Effect in Laser Bunch Slicing

    International Nuclear Information System (INIS)

    Shimada, M.; Katoh, M.; Adachi, M.; Kimura, S.; Tanikawa, T.; Hosaka, M.; Yamamoto, N.; Takashima, Y.; Takahashi, T.

    2009-01-01

    We report turn-by-turn observation of coherent synchrotron radiation (CSR) produced by the laser bunch slicing technique at an electron storage ring operated with a small momentum compaction factor. CSR emission was intermittent, and its interval depended strongly on the betatron tune. This peculiar behavior of the CSR could be interpreted as a result of coupling between the transverse and longitudinal motion of the electrons. This is the first observation of such an effect, which would be important not only for controlling the CSR emission but also for generating and transporting ultrashort electron bunches or electron bunches with microdensity structures in advanced accelerators.

  12. Electron Bunch Length Diagnostic With Coherent Smith-Purcell Radiation

    International Nuclear Information System (INIS)

    Nguyen, D.C.

    1997-01-01

    The authors have designed a new technique for measuring subpicosecond electron bunch lengths using coherent Smith-Purcell radiation. This new diagnostic technique involves passing the electron beam in close proximity of a grating with a period comparable to the electron bunch length. The emitted Smith-Purcell radiation will have a coherent component whose angular position and distribution are directly related to the electron bunch length and longitudinal profile, respectively. This new diagnostic technique is inherently simple, inexpensive and non-intercepting. The authors show that the new technique is also scaleable to femtosecond regime

  13. Longitudinal Electron Bunch Diagnostics Using Coherent Transition Radiation

    CERN Document Server

    Mihalcea, Daniel; Happek, Uwe; Regis-Guy Piot, Philippe

    2005-01-01

    The longitudinal charge distribution of electron bunches in the Fermilab A0 photo-injector was determined by using the coherent transition radiation produced by electrons passing through a thin metallic foil. The auto-correlation of the transition radiation signal was measured with a Michelson type interferometer. The response function of the interferometer was determined from measured and simulated power spectra for low electron bunch charge and maximum longitudinal compression. Kramers-Kroning technique was used to determine longitudinal charge distribution. Measurements were performed for electron bunch lengths in the range from 0.3 to 2 ps (rms).

  14. Chicane and wiggler based bunch compressors for future linear colliders

    International Nuclear Information System (INIS)

    Raubenheimer, T.O.; Emma, P.; Kheifets, S.

    1993-05-01

    In this paper, we discuss bunch compressors for future linear colliders. In the past, the bunch compression optics has been based upon achromatic cells using strong sextupoles to correct the dispersive and betatron chromaticity. To preserve the very small emittances required in most future collider designs, these schemes tend to have very tight alignment tolerances. Here, we describe bunch compressors based upon magnetic chicanes or wigglers which do need sextupoles to correct the chromatic emittance dilution. The dispersive chromaticity cancels naturally and the betatron chromaticity is not a significant source of emittance dilution. Thus, these schemes allow for substantially reduced alignment tolerances. Finally, we present a detailed design for the NLC linear collider

  15. New diagnostics and cures for coupled-bunch instabilities

    International Nuclear Information System (INIS)

    Prabhakar, S.

    2000-01-01

    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 instability

  16. X-ray emission reduction and photon dose lowering by energy loss of fast electrons induced by return current during the interaction of a short-pulse high-intensity laser on a metal solid target

    Science.gov (United States)

    Compant La Fontaine, A.

    2018-04-01

    During the interaction of a short-pulse high-intensity laser with the preplasma produced by the pulse's pedestal in front of a high-Z metal solid target, high-energy electrons are produced, which in turn create an X-ray source by interacting with the atoms of the converter target. The current brought by the hot electrons is almost completely neutralized by a return current j → driven by the background electrons of the conductive target, and the force exerted on the hot electrons by the electric field E → which induces Ohmic heating j → .E → , produced by the background electrons, reduces the energy of the hot electrons and thus lowers the X-ray emission and photon dose. This effect is analyzed here by means of a simple 1-D temperature model which contains the most significant terms of the relativistic Fokker-Planck equation with electron multiple scattering, and the energy equations of ions, hot, and cold electrons are then solved numerically. This Ohmic heating energy loss fraction τOh is introduced as a corrective term in an improved photon dose model. For instance, for a ps laser pulse with 10 μm spot size, the dose obtained with a tantalum target is reduced by less than about 10% to 40% by the Ohmic heating, depending upon the plasma scale length, target thickness, laser parameters, and in particular its spot size. The laser and plasma parameters may be optimized to limit the effect of Ohmic heating, for instance at a small plasma scale length or small laser spot size. Conversely, others regimes not suitable for dose production are identified. For instance, the resistive heating is enhanced in a foam target or at a long plasma scale length and high laser spot size and intensity, as the mean emission angle θ0 of the incident hot electron bunch given by the ponderomotive force is small; thus, the dose produced by a laser interacting in a gas jet may be inhibited under these circumstances. The resistive heating may also be maximized in order to reduce

  17. Simultaneous improvement in short circuit current, open circuit voltage, and fill factor of polymer solar cells through ternary strategy.

    Science.gov (United States)

    An, Qiaoshi; Zhang, Fujun; Li, Lingliang; Wang, Jian; Sun, Qianqian; Zhang, Jian; Tang, Weihua; Deng, Zhenbo

    2015-02-18

    We present a smart strategy to simultaneously increase the short circuit current (Jsc), the open circuit voltage (Voc), and the fill factor (FF) of polymer solar cells (PSCs). A two-dimensional conjugated small molecule photovoltaic material (SMPV1), as the second electron donor, was doped into the blend system of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C71-butyric acid methyl (PC71BM) to form ternary PSCs. The ternary PSCs with 5 wt % SMPV1 doping ratio in donors achieve 4.06% champion power conversion efficiency (PCE), corresponding to about 21.2% enhancement compared with the 3.35% PCE of P3HT:PC71BM-based PSCs. The underlying mechanism on performance improvement of ternary PSCs can be summarized as (i) harvesting more photons in the longer wavelength region to increase Jsc; (ii) obtaining the lower mixed highest occupied molecular orbital (HOMO) energy level by incorporating SMPV1 to increase Voc; (iii) forming the better charge carrier transport channels through the cascade energy level structure and optimizing phase separation of donor/acceptor materials to increase Jsc and FF.

  18. Small-Molecule Solar Cells with Simultaneously Enhanced Short-Circuit Current and Fill Factor to Achieve 11% Efficiency.

    Science.gov (United States)

    Nian, Li; Gao, Ke; Jiang, Yufeng; Rong, Qikun; Hu, Xiaowen; Yuan, Dong; Liu, Feng; Peng, Xiaobin; Russell, Thomas P; Zhou, Guofu

    2017-08-01

    High-efficiency small-molecule-based organic photovoltaics (SM-OPVs) using two electron donors (p-DTS(FBTTh 2 ) 2 and ZnP) with distinctively different absorption and structural features are reported. Such a combination works well and synergically improves device short-circuit current density (J sc ) to 17.99 mA cm -2 and fill factor (FF) to 77.19%, yielding a milestone efficiency of 11%. To the best of our knowledge, this is the highest power conversion efficiency reported for SM-OPVs to date and the first time to combine high J sc over 17 mA cm -2 and high FF over 77% into one SM-OPV. The strategy of using multicomponent materials, with a selecting role of balancing varied electronic and structural necessities can be an important route to further developing higher performance devices. This development is important, which broadens the dimension and versatility of existing materials without much chemistry input. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Radial direct bandgap p-i-n GaNP microwire solar cells with enhanced short circuit current

    Energy Technology Data Exchange (ETDEWEB)

    Sukrittanon, Supanee [Graduate Program of Materials Science and Engineering, University of California, San Diego, La Jolla, California 92037 (United States); Liu, Ren; Pan, Janet L. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92037 (United States); Breeden, Michael C. [Department of Nanoengineering, University of California, San Diego, La Jolla, California 92037 (United States); Jungjohann, K. L. [Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Tu, Charles W., E-mail: ctu@ece.ucsd.edu, E-mail: sdayeh@ece.ucsd.edu; Dayeh, Shadi A., E-mail: ctu@ece.ucsd.edu, E-mail: sdayeh@ece.ucsd.edu [Graduate Program of Materials Science and Engineering, University of California, San Diego, La Jolla, California 92037 (United States); Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92037 (United States)

    2016-08-07

    We report the demonstration of dilute nitride heterostructure core/shell microwire solar cells utilizing the combination of top-down reactive-ion etching to create the cores (GaP) and molecular beam epitaxy to create the shells (GaNP). Systematic studies of cell performance over a series of microwire lengths, array periods, and microwire sidewall morphologies examined by transmission electron microscopy were conducted to shed light on performance-limiting factors and to optimize the cell efficiency. We show by microscopy and correlated external quantum efficiency characterization that the open circuit voltage is degraded primarily due to the presence of defects at the GaP/GaNP interface and in the GaNP shells, and is not limited by surface recombination. Compared to thin film solar cells in the same growth run, the microwire solar cells exhibit greater short circuit current but poorer open circuit voltage due to greater light absorption and number of defects in the microwire structure, respectively. The comprehensive understanding presented in this work suggests that performance benefits of dilute nitride microwire solar cells can be achieved by further tuning of the epitaxial quality of the underlying materials.

  20. Current-day precision oncology: from cancer prevention, screening, drug development, and treatment - have we fallen short of the promise?

    Science.gov (United States)

    Morgan, Gilberto; Aftimos, Philippe; Awada, Ahmad

    2016-09-01

    Precision oncology has been a strategy of prevention, screening, and treatment. Although much has been invested, have the results fallen so far short of the promise? The advancement of technology and research has opened new doors, yet a variety of pitfalls are present. This review presents the successes, failures, and opportunities of precision oncology in the current landscape. The use of targeted gene sequencing and the overwhelming results of superresponders have generated much excitement and support for precision oncology from the medical community. Despite notable successes, many challenges still pave the way of precision oncology: intratumoral heterogeneity, the need for serial biopsies, availability of treatments, target prioritization, ethical issues with germline incidental findings, medical education, clinical trial design, and costs. Precision oncology shows much potential through the use of next-generation sequencing and molecular advances, but does this potential warrant the investment? There are many obstacles on the way of this technology that should make us question if the investment (both monetary and man-hours) will live up to the promise. The review aims to not criticize this technology, but to give a realistic view of where we are, especially regarding cancer treatment and prevention.

  1. A short review of our current understanding of the development of ring faults during collapse caldera formation

    Directory of Open Access Journals (Sweden)

    Adelina eGeyer

    2014-09-01

    Full Text Available The term collapse caldera refers to those volcanic depressions resulting from the sinking of the chamber roof due to the rapid withdrawal of magma during the course of an eruption. During the last three decades, collapse caldera dynamics has been the focus of attention of numerous, theoretical, numerical and experimental studies. Nonetheless, even if there is a tendency to go for a general and comprehensive caldera dynamics model, some key aspects remain unclear, controversial or completely unsolved. This is the case of ring fault nucleation points and propagation and dip direction. Since direct information on calderas’ deeper structure comes mainly from partially eroded calderas or few witnessed collapses, ring faults layout at depth remains still uncertain. This has generated a strong debate over the detailed internal fault and fracture configuration of a caldera collapse and, in more detail, how ring faults initiate and propagate. We offer here a very short description of the main results obtained by those analogue and theoretical/mathematical models applied to the study of collapse caldera formation. We place special attention on those observations related to the nucleation and propagation of the collapse-controlling ring faults. This summary is relevant to understand the current state-of-the-art of this topic and it should be taken under consideration in future works dealing with collapse caldera dynamics.

  2. Microwave measurements of energy lost to longitudinal modes by single electron bunches traversing periodic structures

    International Nuclear Information System (INIS)

    Wang, J.W.; Loew, G.A.; Weaver, J.N.; Wilson, P.B.

    1981-10-01

    In the design of future linear colliders, it will be important to minimize the loss of beam energy due to the excitation of higher-order modes in the accelerator structure by single bunches of electrons or positrons. This loss is not only detrimental in itself but also gives rise to energy spectrum widening and transverse emittance growth. Microwave measurements made on disk-loaded and alternating-spoke structures to determine the loss to the longitudinal modes are described. In these measurements the Gaussian bunch is simulated by a current pulse of the same shape transmitted through the structure on an axial center conductor. Results to date are presented for the total longitudinal loss parameter per period K in volts per picocoulomb

  3. 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.

  4. Feedback for suppression of single-bunch transverse instability in electron-positron storage rings

    International Nuclear Information System (INIS)

    Smaluk, V; Sukhanov, D; Oreshonok, V; Cherepanov, V; Kiselev, V

    2012-01-01

    Transverse head-tail instability is a severe limitation of a single-bunch beam current in circular accelerators. Applicability and efficiency of feedbacks for suppression of the instability is analyzed. Both chromatic and nonlinear effects have been taken into account to understand the processes of excitation and damping of the instability. Analytical estimations are compared with the results of experiments and numerical simulations. A feedback system has been developed, installed and commissioned at the VEPP-4M electron-positron collider. An original scheme of the kicker powering has been developed to provide the necessary performance with minimal expenses. Real-time digital data processing performed by a code running in an FPGA module provides high efficiency and flexibility of the system. During the system commissioning, a more than threefold increase of intensity of the VEPP-4M single-bunch beam has been achieved.

  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. Architectures and Algorithms for Control and Diagnostics of Coupled-Bunch Instabilities in Circular Accelerators

    International Nuclear Information System (INIS)

    Teytelman, Dmitry

    2003-01-01

    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

  7. Effects of emittance and space-charge in femtosecond bunch compression

    International Nuclear Information System (INIS)

    Kan, K.; Yang, J.; Kondoh, T.; Norizawa, K.; Yoshida, Y.

    2008-01-01

    Ultrashort electron bunches of the order of <100fs are essential for the study of ultrafast reactions and phenomena by means of time-resolved pump-probe experiments. In order to generate such an electron bunch, the effects of emittance, space-charge (SC) and coherent synchrotron radiation (CSR) on the bunch length in a femtosecond magnetic bunch compressor were studied theoretically. It was observed that the bunch length is dominated by the emittance, SC and CSR effects when the electron bunch is compressed into a femtosecond electron bunch. The increases in bunch length due to the transverse emittance, SC and CSR effects in the bunch compressor were 1.7 fs/mm mrad, 107 fs/nC and 72 fs/nC, respectively. Finally, the simulated bunch length was compared with the experimental results.

  8. Bunched soliton states in weakly coupled sine-Gordon systems

    International Nuclear Information System (INIS)

    Gronbech-Jensen, N.; Samuelsen, M.R.; Lomdahl, P.S.; Blackburn, J.A.

    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

  9. Three bunch energy stabilization for the SLC injector

    International Nuclear Information System (INIS)

    Sheppard, J.C.; Almog, I.; Bambade, P.S.; Clendenin, J.E.; Jobe, R.K.; Phinney, N.; Shoaee, H.; Stiening, R.F.; Thompson, K.A.

    1986-09-01

    Slow feedback has been developed to control the energy and energy spread of the beams which are injected into the SLC damping rings. Within a single RF pulse, two bunches of electrons and one bunch of positrons are accelerated to an energy of 1.21 GeV in the injector of the SLC. The two electron bunches are deflected into the north damping ring while the positrons are targeted into the south ring. In order to fit into the acceptance of the rings, the composite energy deviation and energy spread of the beams must be less than 2% full width. Control of the beam energy characteristics is accomplished with a set of computer controlled feedback loops which monitor the parameters of the three bunches and make adjustments to the available RF energy, RF phasing, and RF timing. This paper presents an overview of the feedback algorithms and of the special hardware developments, and reports on the operational status of the processes

  10. Review of Coupled Bunch Instabilities in the LHC

    CERN Document Server

    Angal-Kalinin, Deepa

    2002-01-01

    In order to reach the required luminosity, the LHC will have a large number of high intensity bunches. Coupled bunch instabilities can therefore be excited by the higher order modes (HOMs)of the RF cavities, by parasitic cavities and by the transverse resistive wall effect. This report summarises the growth times of the coupled bunch instabilities taking into account the HOMs (damped or undamped)relevant for the 200 MHz normal conducting cavities, the 400 MHz superconducting cavities, as well as other parasitic cavities. It is shown that, with the damped HOMs of the RF cavities, the coupled bunch instabilities remain within control for the LHC operation.As far as the transverse resistive wall effect at injection disconcerned,it is demonstrated that the corresponding growth times can be safely compensated by the proposed transverse feedback system [1].

  11. Method of controlling coherent synchroton radiation-driven degradation of beam quality during bunch length compression

    Science.gov (United States)

    Douglas, David R [Newport News, VA; Tennant, Christopher D [Williamsburg, VA

    2012-07-10

    A method of avoiding CSR induced beam quality defects in free electron laser operation by a) controlling the rate of compression and b) using a novel means of integrating the compression with the remainder of the transport system: both are accomplished by means of dispersion modulation. A large dispersion is created in the penultimate dipole magnet of the compression region leading to rapid compression; this large dispersion is demagnified and dispersion suppression performed in a final small dipole. As a result, the bunch is short for only a small angular extent of the transport, and the resulting CSR excitation is small.

  12. Can coherent Smith-Purcell radiation be used to determine the shape of an electron bunch?

    International Nuclear Information System (INIS)

    Doria, A.; Gallerano, G.P.; Giovenale, E.; Messina, G.; Doucas, G.; Kimmitt, M.F.; Andrews, H.L.; Brownell, J.H.

    2002-01-01

    Recent measurements at Frascati of the Smith-Purcell radiation emitted from the interaction of a 2.3 MeV (total) electron beam with a 2.5 mm grating show clear evidence of coherent enhancement of the radiation, with power levels exceeding 100 mW at emission angles around 90 deg. relative to the beam direction. The experimental results are in reasonable agreement with theoretical predictions and suggest that Smith-Purcell radiation may offer a simple way of determining the shape and duration of short (picosecond) electron bunches

  13. Bunch by bunch beam monitoring in 3rd and 4th generation light sources by means of single crystal diamond detectors and quantum well devices

    Science.gov (United States)

    Antonelli, M.; Di Fraia, M.; Tallaire, A.; Achard, J.; Carrato, S.; Menk, R. H.; Cautero, G.; Giuressi, D.; Jark, W. H.; Biasiol, G.; Ganbold, T.; Oliver, K.; Callegari, C.; Coreno, M.; De Sio, A.; Pace, E.

    2012-10-01

    New generation Synchrotron Radiation (SR) sources and Free Electron Lasers (FEL) require novel concepts of beam diagnostics to keep photon beams under surveillance, asking for simultaneous position and intensity monitoring. To deal with high power load and short time pulses provided by these sources, novel materials and methods are needed for the next generation BPMs. Diamond is a promising material for the production of semitransparent in situ X-ray BPMs withstanding the high dose rates of SR rings and high energy FELs. We report on the development of freestanding, single crystal CVD diamond detectors. Performances in both low and radio frequency SR beam monitoring are presented. For the former, sensitivity deviation was found to be approximately 2%; a 0.05% relative precision in the intensity measurements and a 0.1-μm precision in the position encoding have been estimated. For the latter, single-shot characterizations revealed sub-nanosecond rise-times and spatial precisions below 6 μm, which allowed bunch-by-bunch monitoring in multi-bunch operation. Preliminary measurements at the Fermi FEL have been performed with this detector, extracting quantitative intensity and position information for FEL pulses (~ 100 fs, energy 12 ÷ 60 eV), with a long-term spatial precision of about 85 μm results on FEL radiation damages are also reported. Due to their direct, low-energy band gap, InGaAs quantum well devices too may be used as fast detectors for photons ranging from visible to X-ray. Results are reported which show the capability of a novel InGaAs/InAlAs device to detect intensity and position of 100-fs-wide laser pulses.

  14. Coupled-bunch instabilities in the APS ring

    International Nuclear Information System (INIS)

    Emery, L.

    1991-01-01

    A study of coupled bunch instabilities for the APS storage ring is presented. The instabilities are driven by the higher-order modes of the fifteen 352-MHz single-cell RF cavities. These modes are modeled using the 2-D cavity program URMEL. The program ZAP is then used to estimate the growth time of the instabilities for an equally-spaced bunch pattern. The cavity modes most responsible for the instabilities will be singles out for damping. 7 refs., 5 tabs

  15. Nonlinear space charge effect of bunched beam in linac

    International Nuclear Information System (INIS)

    Chen Yinbao

    1992-02-01

    The nonlinear space charge effect due to the nonuniform particle density distribution in bunched beam of a linac is discussed. The formulae of nonlinear space charge effect and nonlinear focusing forces were derived for the bunched beam with Kapchinskij-Vladimirskij (K-V) distribution, waterbag (WB) distribution, parabolic (PA) distribution, and Gauss (GA) distribution in both of the space charge disk model and space charge cylinder model in the waveguide of a linac

  16. Performance Analysis of a Bunch and Track Identifier Prototype (BTI) for the CMS Barrel Muon Drift Chambers; Estudio de las Prestaciones de un Prototipo de Bunch and Track Identifier (BTI) para las Camaras de Deriva de CMS

    Energy Technology Data Exchange (ETDEWEB)

    Puerta Pelayo, J.

    2001-07-01

    This note contains a short description of the first step in the first level trigger applied to the barrel muon drift chambers of CMS: the Bunch and Track Identifier (BTI). The test beam results obtained with a BTI prototype have been also analysed BTI performance for different incidence angles and in presence of external magnetic field has been tested, as well as BTI capability as trigger device and track reconstructor. (Author) 30 refs.

  17. Increase in short-term memory capacity induced by down-regulating individual theta frequency via transcranial alternating current stimulation.

    Science.gov (United States)

    Vosskuhl, Johannes; Huster, René J; Herrmann, Christoph S

    2015-01-01

    Working memory (WM) and short-term memory (STM) supposedly rely on the phase-amplitude coupling (PAC) of neural oscillations in the theta and gamma frequency ranges. The ratio between the individually dominant gamma and theta frequencies is believed to determine an individual's memory capacity. The aim of this study was to establish a causal relationship between the gamma/theta ratio and WM/STM capacity by means of transcranial alternating current stimulation (tACS). To achieve this, tACS was delivered at a frequency below the individual theta frequency. Thereby the individual ratio of gamma to theta frequencies was changed, resulting in an increase of STM capacity. Healthy human participants (N = 33) were allocated to two groups, one receiving verum tACS, the other underwent a sham control protocol. The electroencephalogram (EEG) was measured before stimulation and analyzed with regard to the properties of PAC between theta and gamma frequencies to determine individual stimulation frequencies. After stimulation, EEG was recorded again in order to find after-effects of tACS in the oscillatory features of the EEG. Measures of STM and WM were obtained before, during and after stimulation. Frequency spectra and behavioral data were compared between groups and different measurement phases. The tACS- but not the sham stimulated group showed an increase in STM capacity during stimulation. WM was not affected in either groups. An increase in task-related theta amplitude after stimulation was observed only for the tACS group. These augmented theta amplitudes indicated that the manipulation of individual theta frequencies was successful and caused the increase in STM capacity.

  18. Increase in short-term memory capacity induced by down-regulating individual theta frequency via transcranial alternating current stimulation

    Directory of Open Access Journals (Sweden)

    Johannes eVosskuhl

    2015-05-01

    Full Text Available Working memory (WM and short-term memory (STM supposedly rely on the phase-amplitude coupling of neural oscillations in the theta and gamma frequency ranges. The ratio between the individually dominant gamma and theta frequencies is believed to determine an individual’s memory capacity. The aim of this study was to establish a causal relationship between the gamma/theta ratio and WM/STM capacity by means of transcranial alternating current stimulation (tACS. To achieve this, tACS was delivered at a frequency below the individual theta frequency. Thereby the individual ratio of gamma to theta frequencies was changed, resulting in an increase of STM capacity. Healthy human participants (N=33 were allocated to two groups, one receiving verum tACS, the other underwent a sham control protocol. The electroencephalogram (EEG was measured before stimulation and analyzed with regard to the properties of phase-amplitude coupling between theta and gamma frequencies to determine individual stimulation frequencies. After stimulation, EEG was recorded again in order to find after-effects of tACS in the oscillatory features of the EEG. Measures of STM and WM were obtained before, during and after stimulation. Frequency spectra and behavioral data were compared between groups and different measurement phases. The tACS- but not the sham stimulated group showed an increase in STM capacity during stimulation. WM was not affected in either groups. An increase in task-related theta amplitude after stimulation was observed only for the tACS group. These augmented theta amplitudes indicated that the manipulation of individual theta frequencies was successful and caused the increase in STM capacity.

  19. The effect of acute hypoxia on short-circuit current and epithelial resistivity in biopsies from human colon.

    Science.gov (United States)

    Carra, Graciela E; Ibáñez, Jorge E; Saraví, Fernando D

    2013-09-01

    In isolated colonic mucosa, decreases in short-circuit current (ISC) and transepithelial resistivity (RTE) occur when hypoxia is either induced at both sides or only at the serosal side of the epithelium. We assessed in human colon biopsies the sensitivity to serosal-only hypoxia and mucosal-only hypoxia and whether Na, K-ATPase blockade with ouabain interacts with hypoxia. Biopsy material from patients undergoing colonoscopy was mounted in an Ussing chamber for small samples (1-mm2 window). In a series of experiments we assessed viability and the electrical response to the mucolytic, dithiothreitol (1 mmol/l). In a second series, we explored the effect of hypoxia without and with ouabain. In a third series, we evaluated the response to a cycle of hypoxia and reoxygenation induced at the serosal or mucosal side while keeping the oxygenation of the opposite side. 1st series: Dithiothreitol significantly decreased the unstirred layer and ISC but increased RTE. 2nd series: Both hypoxia and ouabain decreased ISC, but ouabain increased RTE and this effect on RTE prevailed even during hypoxia. 3rd series: Mucosal hypoxia caused lesser decreases of ISC and RTE than serosal hypoxia; in the former, but not in the latter, recovery was complete upon reoxygenation. In mucolytic concentration, dithiothreitol modifies ISC and RTE. Oxygen supply from the serosal side is more important to sustain ISC and RTE in biopsy samples. The different effect of hypoxia and Na, K-ATPase blockade on RTE suggests that their depressing effect on ISC involves different mechanisms.

  20. Bunch arrival time monitors; Concepts towards improving the sensitivity for low charge operation for FLASH II and XFEL

    Energy Technology Data Exchange (ETDEWEB)

    Penirschke, Andreas; Angelovski, Aleksandar; Jakoby, Rolf [TU Darmstadt, Institut fuer Mikrowellentechnik und Photonik, Merckstr. 25, 64283 Darmstadt (Germany); Sydlo, Cezary; Bousonville, Michael; Czwalinna, Marie Kristin; Schlarb, Holger [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kuhl, Alexander [University of Hamburg, Physics Department, Accelerator Physics Group (Germany); Weiland, Thomas [Technische Univ. Darmstadt (Germany). Inst. fuer Theorie Elektromagnetischer Felder

    2013-07-01

    High gain Free-Electron Lasers can generate ultra short X-ray pulses in the femtosecond range. For a stable operation of the FEL, the precise knowledge of the bunch arrival time is crucial. A novel high bandwidth Bunch Arrival time Monitor was recently installed at FLASH to allow a low charge operation mode with a sub-10 fs resolution for bunch charges of 20 pC or more. The BAM is equipped with cone shaped pickups for the precise measurement of both, the high and low bunch charge operation mode. For the extension of FLASH facility to FLASH II new pickups for the high bandwidth BAMs need to be developed. The new BAM needs to maximize the voltage level of the beam induced signal for low charge operation mode in order to provide sufficient signal strength for the subsequent electronics. In this talk, we present concepts to improve the signal strength at the electro-optic modulators for low charge operation at FLASH II and XFEL.

  1. State orthogonality, boson bunching parameter and bosonic enhancement factor

    International Nuclear Information System (INIS)

    Marchewka, A.; Granot, E.

    2016-01-01

    Bosons bunching is the tendency of bosons to bunch together with respect to distinguishable particles. It is emphasized that the bunching parameter β = p_B/p_D, i.e. the ratio between the probability to measure 2 bosons and 2 distinguishable particles at the same state, is a constant of motion and depends only on the overlap between the initial wavefunctions. This ratio is equal to β = 2/(1 + l"2), where l is the overlap integral between the initial wavefunctions. That is, only when the initial wavefunctions are orthogonal this ratio is equal to 2, however, this bunching ratio can be reduced to 1, when the two wavefunctions are identical. This simple equation explains the experimental evidences of a beam splitter. A straightforward conclusion is that by measuring the local bunching parameter β (at any point in space and time) it is possible to evaluate a global parameter l (the overlap between the initial wavefunctions). The bunching parameter is then generalized to arbitrary number of particles, and in an analogy to the two-particles scenario, the well-known bosonic enhancement appears only when all states are orthogonal

  2. Bunches of random cross-correlated sequences

    International Nuclear Information System (INIS)

    Maystrenko, A A; Melnik, S S; Pritula, G M; Usatenko, O V

    2013-01-01

    The statistical properties of random cross-correlated sequences constructed by the convolution method (likewise referred to as the Rice or the inverse Fourier transformation) are examined. We clarify the meaning of the filtering function—the kernel of the convolution operator—and show that it is the value of the cross-correlation function which describes correlations between the initial white noise and constructed correlated sequences. The matrix generalization of this method for constructing a bunch of N cross-correlated sequences is presented. Algorithms for their generation are reduced to solving the problem of decomposition of the Fourier transform of the correlation matrix into a product of two mutually conjugate matrices. Different decompositions are considered. The limits of weak and strong correlations for the one-point probability and pair correlation functions of sequences generated by the method under consideration are studied. Special cases of heavy-tailed distributions of the generated sequences are analyzed. We show that, if the filtering function is rather smooth, the distribution function of generated variables has the Gaussian or Lévy form depending on the analytical properties of the distribution (or characteristic) functions of the initial white noise. Anisotropic properties of statistically homogeneous random sequences related to the asymmetry of a filtering function are revealed and studied. These asymmetry properties are expressed in terms of the third- or fourth-order correlation functions. Several examples of the construction of correlated chains with a predefined correlation matrix are given. (paper)

  3. 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...

  4. Optimization of the short-circuit current in an InP nanowire array solar cell through opto-electronic modeling.

    Science.gov (United States)

    Chen, Yang; Kivisaari, Pyry; Pistol, Mats-Erik; Anttu, Nicklas

    2016-09-23

    InP nanowire arrays with axial p-i-n junctions are promising devices for next-generation photovoltaics, with a demonstrated efficiency of 13.8%. However, the short-circuit current in such arrays does not match their absorption performance. Here, through combined optical and electrical modeling, we study how the absorption of photons and separation of the resulting photogenerated electron-hole pairs define and limit the short-circuit current in the nanowires. We identify how photogenerated minority carriers in the top n segment (i.e. holes) diffuse to the ohmic top contact where they recombine without contributing to the short-circuit current. In our modeling, such contact recombination can lead to a 60% drop in the short-circuit current. To hinder such hole diffusion, we include a gradient doping profile in the n segment to create a front surface barrier. This approach leads to a modest 5% increase in the short-circuit current, limited by Auger recombination with increased doping. A more efficient approach is to switch the n segment to a material with a higher band gap, like GaP. Then, a much smaller number of holes is photogenerated in the n segment, strongly limiting the amount that can diffuse and disappear into the top contact. For a 500 nm long top segment, the GaP approach leads to a 50% higher short-circuit current than with an InP top segment. Such a long top segment could facilitate the fabrication and contacting of nanowire array solar cells. Such design schemes for managing minority carriers could open the door to higher performance in single- and multi-junction nanowire-based solar cells.

  5. Performance Analysis of a Bunch and Track Identifier Prototype (BTI) for the CMS Barrel Muon Drift Chambers

    International Nuclear Information System (INIS)

    Puerta Pelayo, J.

    2001-01-01

    This note contains a short description of the first step in the first level trigger applied to the barrel muon drift chambers of CMS: the Bunch and Track Identifier (BTI). The test beam results obtained with a BTI prototype have been also analysed BTI performance for different incidence angles and in presence of external magnetic field has been tested, as well as BTI capability as trigger device and track reconstructor. (Author) 30 refs

  6. Peculiarities of the coherent spontaneous synchrotron radiation of dense electron bunches

    International Nuclear Information System (INIS)

    Balal, N.; Bratman, V. L.; Savilov, A. V.

    2014-01-01

    In a short section of homogeneous magnetic field, quasi-plane electron bunches from linear accelerators with laser-driven photo-injectors at moderate particle energies can generate strongly directed, very short and powerful terahertz electromagnetic pulses with a broad frequency spectrum. The formulas for radiation fields, their spectra and efficiency of radiation are presented in a very simple analytical form using expressions for the fields of an arbitrary moving charged plane. The self-action and mutual interaction of thin electron layers are estimated. It is shown that the radiation with frequencies of up to (1–3) THz can be effectively generated by electrons with energies (4–6) MeV in a short and relatively weak magnetic field of (4–10) kOe

  7. Peculiarities of the coherent spontaneous synchrotron radiation of dense electron bunches

    Energy Technology Data Exchange (ETDEWEB)

    Balal, N. [Ariel University, Ariel (Israel); Bratman, V. L. [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod (Russian Federation); Savilov, A. V., E-mail: savilov@appl.sci-nnov.ru [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod (Russian Federation); Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod (Russian Federation)

    2014-02-15

    In a short section of homogeneous magnetic field, quasi-plane electron bunches from linear accelerators with laser-driven photo-injectors at moderate particle energies can generate strongly directed, very short and powerful terahertz electromagnetic pulses with a broad frequency spectrum. The formulas for radiation fields, their spectra and efficiency of radiation are presented in a very simple analytical form using expressions for the fields of an arbitrary moving charged plane. The self-action and mutual interaction of thin electron layers are estimated. It is shown that the radiation with frequencies of up to (1–3) THz can be effectively generated by electrons with energies (4–6) MeV in a short and relatively weak magnetic field of (4–10) kOe.

  8. 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.

  9. 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...

  10. Virtual photon impulse of bunch, beampipe response, coherent RF Beamstrahlung; and BEPC bunch length, BES jam, virtual acceleration

    International Nuclear Information System (INIS)

    Jing Shen

    1993-01-01

    A brief EEE view of signal QED is presented. The research has been concentrated on the virtual photon modes of ultra relativistic shock wave in a bunch-beampipe system, and real photon modes of Coherent RF Beamstrahlung CRFB. Physically, the virtual photons emitted by a bunch were treated as a travelling pseudo wave packet in a flight coaxial cavity constructed by bunch-wakefield core and beampipe. Mathematically, it is a boundary solution of shock wave excited by ultra relativistic impulse of bunch. The new modes of solution: VTA, VTEM, VTM, VLE are virtual photon packets and RTE, RTM, RTEM are real photon modes of CRFB. By these results the author measured and corrected BEPC bunch length from signals of : (1) TOF reference of BES, (2) BPM of BEPC, (3) Colliding CRFB of BEPC - BES coupling signal, as well as (4) the ordinary method of Synchrotron Radiation. All results of the measured bunch lengths are in accordance with the design length of BEPC, and were verified by the BES data of vertex reconstruction of hadron events. The author also found that CRFB is the unknown jam source of BES electronics. VLE virtual photons can accelerate particles

  11. Analysis of the high frequency longitudinal instability of bunched beams using a computer model

    International Nuclear Information System (INIS)

    Messerschmid, E.; Month, M.

    1976-01-01

    The effects of high frequency longitudinal forces on bunched beams are investigated using a computer model. These forces are thought to arise from the transfer of energy between the beam and various structures in the vacuum chamber, this coupling being characterized by a longitudinal impedance function. The simulation is performed with a passive cavity-like element. It is found that the instability can be generated if three conditions are fulfilled: (1) the impedance must be sufficiently large, (2) the induced field must have a fast wake, and (3) the frequency of the induced field must be high enough. In particular, it is shown that the coasting beam threshold criterion for the longitudinal impedance accurately describes the onset of instability, if local values along the bunch of energy spread and current are used. It is also found that the very fast initial growth rate is in good agreement with linear theory and that the coasting beam overshoot expression may be used as a rough guide of the limiting growth for unstable bunches. Concerning the wake field, it is shown how the instability tends to disappear as the fields persist longer. It is furthermore demonstrated that as the wavelength of the unstable mode is increased, initially unstable conditions begin to weaken and vanish. This, it should be emphasized, is primarily a result of the strong correlation between the unstable mode frequency and the time rate of attenuation of the induced fields. ISR parameters are used throughout and a correspondence between the microwave instability observed in the ISR bunches and the simulated instability is suggested. (Auth.)

  12. Fast polycrystalline CdTe detectors for bunch-by-bunch luminosity monitoring in the LHC

    CERN Document Server

    Brambilla, A; Jolliot, M; Bravin, E

    2008-01-01

    The luminosity at the four interaction points of the Large Hadron Collider (LHC) must be continuously monitored in order to provide an adequate tool for the control and optimisation of beam parameters. Polycrystalline cadmium telluride (CdTe) detectors have previously been tested, showing their high potential to fulfil the requirements of luminosity measurement in the severe environment of the LHC interaction regions. Further, the large signal yield and the fast response time should allow bunch-by-bunch measurement of the luminosity at 40 MHz with high accuracy. Four luminosity monitors with two rows of five polycrystalline CdTe detectors each have been fabricated and will be installed at both sides of the low-luminosity interaction points ALICE and LHC-b. A detector housing was specially designed to meet the mechanical constraints in the LHC. A series of elementary CdTe detectors were fabricated and tested, of which 40 were selected for the luminosity monitors. A sensitivity of 104 electrons per minimum ioni...

  13. The role of space charge in the performance of the bunching system for the ATLAS Positive Ion Injector

    International Nuclear Information System (INIS)

    Pardo, R.C.; Smith, R.

    1995-01-01

    The bunching system of the ATLAS Positive Ion Injector consists of a four-frequency harmonic buncher, a beam-tail removing chopper, and a 24.25 MHz spiral resonator sine-wave rebuncher. The system is designed to efficiently create beam pulses of approximately 0.25 nsec FWHM for injection into mid acceleration by the ATLAS superconducting linac. Studies of the effect of space charge on the performance of the system have been undertaken and compared to simulations as part of the design process for a new bunching system to be developed for a second ion source. Results of measurements and modeling studies indicate that the present system suffers significant bunching performance deterioration at beam currents as low as 5 eμA for 238 U 26+ at a velocity of β=0.0085. The low beam current tolerance of the present system is in reasonable agreement with computer simulation. Studies of two alternatives to the present bunching system are discussed and their limitations are explored

  14. Grapevine bunch rots: impacts on wine composition, quality, and potential procedures for the removal of wine faults.

    Science.gov (United States)

    Steel, Christopher C; Blackman, John W; Schmidtke, Leigh M

    2013-06-05

    Bunch rot of grape berries causes economic loss to grape and wine production worldwide. The organisms responsible are largely filamentous fungi, the most common of these being Botrytis cinerea (gray mold); however, there are a range of other fungi responsible for the rotting of grapes such as Aspergillus spp., Penicillium spp., and fungi found in subtropical climates (e.g., Colletotrichum spp. (ripe rot) and Greeneria uvicola (bitter rot)). A further group more commonly associated with diseases of the vegetative tissues of the vine can also infect grape berries (e.g., Botryosphaeriaceae, Phomopsis viticola ). The impact these fungi have on wine quality is poorly understood as are remedial practices in the winery to minimize wine faults. Compounds found in bunch rot affected grapes and wine are typically described as having mushroom, earthy odors and include geosmin, 2-methylisoborneol, 1-octen-3-ol, 2-octen-1-ol, fenchol, and fenchone. This review examines the current state of knowledge about bunch rot of grapes and how this plant disease complex affects wine chemistry. Current wine industry practices to minimize wine faults and gaps in our understanding of how grape bunch rot diseases affect wine production and quality are also identified.

  15. Controlled Conjugated Backbone Twisting for an Increased Open-Circuit Voltage while Having a High Short-Circuit Current in Poly(hexylthiophene) Derivatives

    KAUST Repository

    Ko, Sangwon; Hoke, Eric T.; Pandey, Laxman; Hong, Sanghyun; Mondal, Rajib; Risko, Chad; Yi, Yuanping; Noriega, Rodrigo; McGehee, Michael D.; Bré das, Jean-Luc; Salleo, Alberto; Bao, Zhenan

    2012-01-01

    and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone-due to an increase in the polymer ionization potential-while the short-circuit current decreased

  16. Prospective single and multi-phase short-circuit current levels in the Dutch transmission, sub-transmission and distribution grids

    NARCIS (Netherlands)

    Janssen, A.L.J.; van Riet, M.J.M.; Smeets, R.P.P.; Kanters, J.; van den Akker, W.F.; Aanhaanen, G.L.P.

    2012-01-01

    As elsewhere in the world, also in the Netherlands utilities face an increase in the actual and future short-circuit current levels at all voltages. This development is provoked by the required increase in transmission capacity as well as the concentration of power generation capacity. Large

  17. The factors influencing nonlinear characteristics of the short-circuit current in dye-sensitized solar cells investigated by a numerical model.

    Science.gov (United States)

    Shi, Yushuai; Dong, Xiandui

    2013-06-24

    A numerical model for interpretation of the light-intensity-dependent nonlinear characteristics of the short-circuit current in dye-sensitized solar cells is suggested. The model is based on the continuity equation and includes the influences of the nongeminate recombination between electrons and electron acceptors in the electrolyte and the geminate recombination between electrons and oxidized dye molecules. The influences of the order and rate constant of the nongeminate recombination reaction, the light-absorption coefficient of the dye, the film thickness, the rate constant of geminate recombination, and the regeneration rate constant on the nonlinear characteristics of the short-circuit current are simulated and analyzed. It is proposed that superlinear and sublinear characteristics of the short-circuit current should be attributed to low electron-collection efficiency and low dye-regeneration efficiency, respectively. These results allow a deep understanding of the origin of the nonlinear characteristics of the short-circuit current in solar cells. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. 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.

  19. Superthermal photon bunching in terms of simple probability distributions

    Science.gov (United States)

    Lettau, T.; Leymann, H. A. M.; Melcher, B.; Wiersig, J.

    2018-05-01

    We analyze the second-order photon autocorrelation function g(2 ) with respect to the photon probability distribution and discuss the generic features of a distribution that results in superthermal photon bunching [g(2 )(0 ) >2 ]. Superthermal photon bunching has been reported for a number of optical microcavity systems that exhibit processes such as superradiance or mode competition. We show that a superthermal photon number distribution cannot be constructed from the principle of maximum entropy if only the intensity and the second-order autocorrelation are given. However, for bimodal systems, an unbiased superthermal distribution can be constructed from second-order correlations and the intensities alone. Our findings suggest modeling superthermal single-mode distributions by a mixture of a thermal and a lasinglike state and thus reveal a generic mechanism in the photon probability distribution responsible for creating superthermal photon bunching. We relate our general considerations to a physical system, i.e., a (single-emitter) bimodal laser, and show that its statistics can be approximated and understood within our proposed model. Furthermore, the excellent agreement of the statistics of the bimodal laser and our model reveals that the bimodal laser is an ideal source of bunched photons, in the sense that it can generate statistics that contain no other features but the superthermal bunching.

  20. Simulations of Bunch Merging in a Beta Beam Decay Ring

    CERN Document Server

    Heinrich, Daniel Christopher; Chance, Antoine

    2011-01-01

    To further study neutrino oscillation properties a Beta Beam facility has been proposed. Beta decaying ions with high kinetic energy are stored in a storage ring ("Decay Ring") with straight sections to create pure focused (anti) electron neutrino beams. However to reach high sensitivity to neutrino oscillation parameters in the experiment the bunched beam intensity and duty cycle in the DR have to be optimized. The first CERN-based scenario, using 6He and 18Ne as neutrino sources, has been studied using a bunch merging RF scheme. Two RF cavities at different frequencies are used to capture newly injected bunches and then merge them into the stored bunches. It was shown that this scheme could satisfy the requirements on intensity and duty cycle set by the experiment. This merging scheme has now been revised with new simulation software providing new results for 6He and 18Ne. Furthermore bunch merging has been studied for the second CERN-based scenario using 8Li and 8B.

  1. Destructive interferences results in bosons anti bunching: refining Feynman's argument

    Science.gov (United States)

    Marchewka, Avi; Granot, Er'el

    2014-09-01

    The effect of boson bunching is frequently mentioned and discussed in the literature. This effect is the manifestation of bosons tendency to "travel" in clusters. One of the core arguments for boson bunching was formulated by Feynman in his well-known lecture series and has been frequently used ever since. By comparing the scattering probabilities of two bosons and of two distinguishable particles, he concluded: "We have the result that it is twice as likely to find two identical Bose particles scattered into the same state as you would calculate assuming the particles were different" [R.P. Feynman, R.B. Leighton, M. Sands, The Feynman Lectures on Physics: Quantum mechanics (Addison-Wesley, 1965)]. This argument was rooted in the scientific community (see for example [C. Cohen-Tannoudji, B. Diu, F. Laloë, Quantum Mechanics (John Wiley & Sons, Paris, 1977); W. Pauli, Exclusion Principle and Quantum Mechanics, Nobel Lecture (1946)]), however, while this sentence is completely valid, as is proved in [C. Cohen-Tannoudji, B. Diu, F. Laloë, Quantum Mechanics (John Wiley & Sons, Paris, 1977)], it is not a synonym of bunching. In fact, as it is shown in this paper, wherever one of the wavefunctions has a zero, bosons can anti-bunch and fermions can bunch. It should be stressed that zeros in the wavefunctions are ubiquitous in Quantum Mechanics and therefore the effect should be common. Several scenarios are suggested to witness the effect.

  2. Micro-bunching diagnostics for the IFEL by coherent transition radiation

    International Nuclear Information System (INIS)

    Liu, Y.; Cline, D.B.

    1996-10-01

    Here, we propose an effective method for detecting micro-bunching effects (10 fs bunch length) produced by the IFEL interaction, by measuring the CTR spectrum. The pre-bunching of an initially energy- modulated c- beam passing through a wiggler (IFEL interaction) is studied. Simulation shows that more than 40% of electrons are pre- bunched in the micro-bunches. The longitudinal distribution of an optically pre-bunched beam is Fourier analyzed to find the dominant harmonics contributing to the CTR. The CTR spectrum is calculated analytically for the IFEL situation. A detection system has been built to demonstrate this technique

  3. Performance of the transverse coupled-bunch feedback system in the SRRC

    International Nuclear Information System (INIS)

    Hsu, K.T.; Kuo, C.C.; Kuo, C.H.; Lin, K.K.; Ueng, T.S.; Weng, W.T.

    1996-01-01

    A transverse feedback system has been implemented and commissioned in the SRRC storage ring to suppress transverse coupled-bunch oscillations of the electron beam. The system includes transverse oscillation detectors, notch filter, baseband quadrature processing circuitry, power amplifiers, and kickers. To control a large number of transverse coupled-bunch modes, the system is broad-band, bunch-by- bunch in nature. Because the system is capable of bunch-by-bunch correction, it can also be useful for suppressing instabilities introduced by ions. The sextupole strength was then reduced to improve dynamic aperture and hence lifetime of the storage ring

  4. Formation and acceleration of uniformly filled ellipsoidal electron bunches obtained via space-charge-driven expansion from a cesium-telluride photocathode

    Directory of Open Access Journals (Sweden)

    P. Piot

    2013-01-01

    Full Text Available We report the experimental generation, acceleration, and characterization of a uniformly filled electron bunch obtained via space-charge-driven expansion (often referred to as “blow-out regime” in an L-band (1.3-GHz radiofrequency photoinjector. The beam is photoemitted from a cesium-telluride semiconductor photocathode using a short (<200  fs ultraviolet laser pulse. The produced electron bunches are characterized with conventional diagnostics and the signatures of their ellipsoidal character are observed. We especially demonstrate the production of ellipsoidal bunches with charges up to ∼0.5  nC corresponding to a ∼20-fold increase compared to previous experiments with metallic photocathodes.

  5. Development of a high brightness, high current SRF photo-electron source for ERL applications

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, Axel [Helmholtz-Zentrum Berlin (Germany); Collaboration: bERLinPro Team

    2016-07-01

    Energy recovery linacs (ERL) offer the potential to combine major beam properties of the two main domains of particle accelerators: The low emittance of linear accelerators and the high average beam current of storage rings, while also allowing to compress to short bunches below the ps regime. This makes among other applications ERLs an ideal candidate for future light sources. The beam properties of the ERL are given by the performance of the injection section and hence of the beam source. Helmholtz-Zentrum Berlin is currently designing and building a high average current all superconducting CW driven ERL as a prototype to demonstrate low normalized beam emittance of 1 mm*mrad at 100 mA and short pulses of about 2 ps. In this contribution we discuss the development of this class of a high brightness, high current SRF photo-electron source and present recent commissioning results. Also, alternative approaches at other laboratories are shortly reviewed.

  6. Understanding and controlling the step bunching instability in aqueous silicon etching

    Science.gov (United States)

    Bao, Hailing

    Chemical etching of silicon has been widely used for more than half a century in the semiconductor industry. It not only forms the basis for current wafer cleaning processes, it also serves as a powerful tool to create a variety of surface morphologies for different applications. Its potential for controlling surface morphology at the atomic scale over micron-size regions is especially appealing. In spite of its wide usage, the chemistry of silicon etching is poorly understood. Many seemingly simple but fundamental questions have not been answered. As a result, the development of new etchants and new etching protocols are based on expensive and tedious trial-and-error experiments. A better understanding of the etching mechanism would direct the rational formulation of new etchants that produce controlled etch morphologies. Particularly, micron-scale step bunches spontaneously develop on the vicinal Si(111) surface etched in KOH or other anisotropic aqueous etchants. The ability to control the size, orientation, density and regularity of these surface features would greatly improve the performance of microelectromechanical devices. This study is directed towards understanding the chemistry and step bunching instability in aqueous anisotropic etching of silicon through a combination of experimental techniques and theoretical simulations. To reveal the cause of step-bunching instability, kinetic Monte Carlo simulations were constructed based on an atomistic model of the silicon lattice and a modified kinematic wave theory. The simulations showed that inhomogeneity was the origin of step-bunching, which was confirmed through STM studies of etch morphologies created under controlled flow conditions. To quantify the size of the inhomogeneities in different etchants and to clarify their effects, a five-parallel-trench pattern was fabricated. This pattern used a nitride mask to protect most regions of the wafer; five evenly spaced etch windows were opened to the Si(110

  7. Fast cooling of bunches in compton storage rings*

    CERN Document Server

    Bulyak, E; Zimmermann, F

    2011-01-01

    We propose an enhancement of laser radiative cooling by utilizing laser pulses of small spatial and temporal dimensions, which interact only with a fraction of an electron bunch circulating in a storage ring. We studied the dynamics of such electron bunch when laser photons scatter off the electrons at a collision point placed in a section with nonzero dispersion. In this case of ‘asymmetric cooling’, the stationary energy spread is much smaller than under conditions of regular scattering where the laser spot size is larger than the electron beam; and the synchrotron oscillations are damped faster. Coherent oscillations of large amplitude may be damped within one synchrotron period, so that this method can support the rapid successive injection of many bunches in longitudinal phase space for stacking purposes. Results of extensive simulations are presented for the performance optimization of Compton gamma-ray sources and damping rings.

  8. Improved Bunch Splitting for the 75ns LHC Beam

    CERN Document Server

    Damerau, H

    2011-01-01

    The 75ns variant was added to the PS arsenal of LHC-type beams by adapting the 20MHz cavity used to produce the 25 and 50ns variants to operate at a switchable 13MHz. This permitted splitting from harmonic 14 to 28, but at a cost in adiabaticity compared with the h=2142 splitting of the other two cases. Consequently, a delicate empirical optimization was necessary to bring the 75ns beam inside specification. More recently the speed at which the bunches, once fully distinct, are moved apart has been revisited and further optimization achieved. As a by-product, deliberately degrading the splitting by moving the bunches apart too quickly led to sufficient coherent motion in the resultant bunch pair to permit a voltage calibration of the 13MHz cavity by means of the influence on convergence of the rf voltage input into the iterative algorithm of the Tomoscope [1,2].

  9. Electro-Magnetic Bunch Length Measurement in LEP

    CERN Document Server

    Vos, L

    1998-01-01

    Bunch lengths between 3 and 12 mm have been measured routinely in LEP in 1997 with a small (7 mm diameter) button electrode. The measurement method is based on the spectral analysis of the electrode signal and relies on the fact that the transfer function of the complete set-up, including the signal cable, can be computed rather exactly thus eliminating the need for external calibration. The information of beam intensity is recovered as a by-product. It provides an interesting internal validation of the measurement by comparison with the normal intensity measurement. The system has been used to detect subtle but real bunch length changes with bunch intensity which can be attributed to the inductive impedance in LEP. A value for the imaginary (inductive) longitudinal impedance is derived from the observations. An indication for the resistive part of the impedance is given as well.

  10. Thresholds of a bunched beam longitudinal instability in proton synchrotrons

    International Nuclear Information System (INIS)

    Balbekov, V.I.; Ivanov, S.V.

    1986-01-01

    The formulas and graphs for calculating instability thresholds arising during the interaction of a bunched proton beam with narrow-band resonator are given. The instabilities of three types with oscillations of a definite multipolarity, oscillations of some bound multipoles and with microwave oscillations arising as a result of addition of a great number of multipoles. The analysis of the above data shows that the increase of oscillations nonlinearity is accompanied by the growth of instability threshold only in the zone of separated and weakly bound multipoles. The increase of spread of synchrotron frequencies reduces the zone separated multipoles owing to which the microwave bunch instability can be caused by more and more low-frequency resonators. In the microwave zone practically there is no stabilizing effect of synchrotron frequencies spread. The instability threshold of the bunched beam now - where exceeds the microwave level

  11. The Limitations of Short-Term Orthodontics and Why We Still Need Specialists – A Review of the Current Literature.

    Science.gov (United States)

    Luqmani, Sana

    2017-01-01

    Short-term orthodontics (STO) serves to align anterior teeth. It has become popular in cosmetic dentistry as an alternative to destructive veneers and lengthy conventional orthodontics. The aim of this article is to raise awareness of the clinical limitations of STO and highlight some of the difficulties encountered with orthodontic retention. It also gives an overview of accredited training available to dentists who wish to develop their orthodontic skills. Clinical relevance: Greater awareness of the clinical limitations of short-term orthodontics will aid GDPs in appropriately selecting their cases and obtaining informed consent from patients. In addition, the article serves as encouragement for those GDPs wishing to develop their orthodontic skills and pursue further accredited training.

  12. Self-seeded operation of the LCLS hard X-ray FEL in the long-bunch mode

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2010-12-15

    Self-seeding options for the LCLS baseline were recently investigated using a scheme which relies on a single-crystal monochromator in Bragg-transmission geometry. The LCLS low-charge (0.02 nC) mode of operation was considered in order to demonstrate the feasibility of the proposed scheme. The wakefield effects from the linac and from the undulator vacuum chamber are much reduced at such low charge, and can be ignored. In this paper we extend our previous investigations to the case of the LCLS mode of operation with nominal charge. Based on the LCLS start-to-end simulation for an electron beam charge of 0.25 nC, and accounting for the wakefields from the undulator vacuum chamber we demonstrate that the same simplest self-seeding system (two undulators with a single-crystal monochromator in between) is appropriate not only for short (few femtosecond) bunches, but for longer bunches too. (orig.)

  13. Self-seeded operation of the LCLS hard X-ray FEL in the long-bunch mode

    International Nuclear Information System (INIS)

    Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

    2010-12-01

    Self-seeding options for the LCLS baseline were recently investigated using a scheme which relies on a single-crystal monochromator in Bragg-transmission geometry. The LCLS low-charge (0.02 nC) mode of operation was considered in order to demonstrate the feasibility of the proposed scheme. The wakefield effects from the linac and from the undulator vacuum chamber are much reduced at such low charge, and can be ignored. In this paper we extend our previous investigations to the case of the LCLS mode of operation with nominal charge. Based on the LCLS start-to-end simulation for an electron beam charge of 0.25 nC, and accounting for the wakefields from the undulator vacuum chamber we demonstrate that the same simplest self-seeding system (two undulators with a single-crystal monochromator in between) is appropriate not only for short (few femtosecond) bunches, but for longer bunches too. (orig.)

  14. Emission of ultrashort electromagnetic pulses from electron bunches formed and accelerated by laser beams with tilted amplitude fronts

    International Nuclear Information System (INIS)

    Galkin, A.L.; Korobkin, V.V.; Romanovsky, M.Yu.; Shiryaev, O.B.; Trofimov, V.A.

    2013-01-01

    The dynamics of an electron in a standing wave generated by a pair of counterpropagating linearly polarized relativistically intense laser pulses and the emission of electromagnetic radiation by the electron are analyzed. The pulses are assumed to have tilted amplitude fronts and asymmetric focal spots. The analysis of the dynamics is performed by solving numerically the Newton equation with the corresponding Lorentz force, and the emission of radiation is simulated based on the Lienard-Wiechert potentials. The electrons are accelerated by the direct action of the standing wave field and are shown to form a small short bunch. For relativistic intensities, the energies gained by the electrons reach several GeV. It is demonstrated that the radiation emitted by the electrons in the bunch is a single electromagnetic pulse confined to a narrow solid angle and having an attosecond duration. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Experimental Observation of Generation of Superradiance Pulses in the Process of Backscattering of Pump Wave on the Intense Electron Bunch

    CERN Document Server

    Ginzburg, N S; Denisov, G G; Rozental, R M; Sergeev, A; Zotova, I V

    2005-01-01

    Recently significant progress was archived in the generation of multimegawatt subnanosecond pulses in millimeter wave band utilizing the cyclotron and Cherenkov mechanisms of superradiance (SR) [1,2]. We study the novel mechanism of SR when the powerful pumping wave undergoes the stimulated back scattering on the intense electron bunch. Due to the Doppler up shift the radiation frequency can significantly exceed the frequency of the pumping wave. With the relativistic microwave generator as a pumping wave source such a mechanism can be used for generation of the powerful pulse radiation in the short millimeter and submillimeter wave bands. Experiments on the observation of the stimulated scattering in the superradiance regime were carried out at Institute of Electrophysics RAS with two synchronized accelerators. The 4 ns electron beam from the first accelerator is used for generation of the 38 GHz 100 MW pumping wave which subsequently scattered on the subnanosecond 250 keV 1 kA electron bunch produced by the...

  16. Electron beam acceleration and compression for short wavelength FELs

    International Nuclear Information System (INIS)

    Raubenheimer, T.O.

    1994-11-01

    A single pass UV or X-ray FEL will require a low emittance electron beam with high peak current and relatively high beam energy, a few hundred MeV to many GeV. To achieve the necessary peak current and beam energy, the beams must be bunch compressed and they must be accelerated in long transport lines where dispersive and wakefield emittance dilutions are important. In this paper, we will describe the sources and significance of the dilutions during acceleration, bunch compression, and transport through the undulator. In addition, we will discuss sources of jitter, especially effects arising from the bunch compressions, and the possible cancellation techniques

  17. Multiple beam envelope equations for electron injectors using a bunch segmentation model

    Directory of Open Access Journals (Sweden)

    A. Mizuno

    2012-06-01

    Full Text Available A new semianalytical method of investigating the beam dynamics for electron injectors was developed. In this method, a short bunched electron beam is assumed to be an ensemble of several segmentation pieces in both the longitudinal and the transverse directions. The trajectory of each electron in the segmentation pieces is solved by the beam envelope equations while taking into account the space charge fields produced by all the pieces, the electromagnetic fields of an rf cavity, and the image charge fields at a cathode surface. The shape of the entire bunch is consequently calculated, and thus the emittances can be obtained from weighted mean values of the solutions for the obtained electron trajectories. The advantage of this method is its unique assumption for the beam parameters. We assume that each segmentation slice is not warped in the calculations. Although if the beam energy is low and the charge density is large, this condition is not satisfied, in practice, this condition is usually satisfied. We have performed beam dynamics calculations to obtain traces in free space and in the BNL-type rf gun cavity by comparing the analytical solutions with those obtained by simulation. In most cases, the emittances obtained by the simulation become closer to those obtained analytically with increasing the number of particles used in the simulation. Therefore, the analytically obtained emittances are expected to coincide with converged values obtained by the simulation. The applicable range of the analytical method for the BNL-type rf gun cavity is under 0.5 nC per bunch. This range is often used in recently built x-ray free electron laser facilities.

  18. 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...

  19. 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.

  20. Transient analysis of a bunched beam free electron laser

    International Nuclear Information System (INIS)

    Wang, J.M.; Yu, L.H.

    1985-01-01

    The problem of the bunched beam operation of a free electron laser was studied. Assuming the electron beam to be initially monoenergetic, the Maxwell-Vlasov equations describing the system reduce to a third order partial differential equation for the envelope of the emitted light. The Green's function corresponding to an arbitrary shape of the electron bunch, which describes the transient behavior of the system, is obtained. The Green's function was used to discuss the start up problem as well as the power output and the power specrum of a self-amplified spontaneous emission

  1. 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.

  2. 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.

  3. Emittance Growth during Bunch Compression in the CTF-II

    Energy Technology Data Exchange (ETDEWEB)

    Raubenheimer, Tor O

    1999-02-26

    Measurements of the beam emittance during bunch compression in the CLIC Test Facility (CTF-II) are described. The measurements were made with different beam charges and different energy correlations versus the bunch compressor settings which were varied from no compression through the point of full compression and to over-compression. Significant increases in the beam emittance were observed with the maximum emittance occurring near the point of full (maximal) compression. Finally, evaluation of possible emittance dilution mechanisms indicate that coherent synchrotron radiation was the most likely cause.

  4. Design of the ALS transverse coupled-bunch feedback system

    International Nuclear Information System (INIS)

    Barry, W.; Byrd, J.M.; Corlett, J.N.; Hinkson, J.; Johnson, J.; Lambertson, G.R.; Fox, J.D.

    1993-05-01

    Calculations of transverse coupled bunch growth rates in the Advanced Light Source (ALS), a 1.5 GeV electron storage ring for producing synchrotron radiation, indicate the need for damping via a transverse feedback (TFB) system. We present the design of such a system. The maximum bunch frequency is 500 MHz, requiring that the FB system have a broadband response of at least 250 MHz. We described, in detail, the choice of broadband components such as kickers, pickups, power amplifiers, and electronics

  5. Cancellation Effects in CSR Induced Bunch Transverse Dynamics in Bends

    International Nuclear Information System (INIS)

    Li, R.

    2002-01-01

    The partial cancellation between the effect of centrifugal space charge force on transverse bunch dynamics and the potential energy effect has been a long-standing controversial issue in the study of coherent synchrotron radiation (CSR) induced bunch dynamics in bends. In this paper, we clarify our definition of the ''centrifugal space charge force,'' and discuss the meaning of the ''cancellation effect'' and its general application. We further use simulation to demonstrate the cancellation in both steady state and transient regimes, and show the behavior of the effective transverse force

  6. Acceleration of electrons by the wake field of proton bunches

    International Nuclear Information System (INIS)

    Ruggiero, A.G.

    1986-01-01

    This paper discusses a novel idea to accelerate low-intensity bunches of electrons (or positrons) by the wake field of intense proton bunches travelling along the axis of a cylindrical rf structure. Accelerating gradients in excess of 100 MeV/m and large ''transformer ratios'', which allow for acceleration of electrons to energies in the TeV range, are calculated. A possible application of the method is an electron-positron linear collider with luminosity of 10 33 cm -2 s -1 . The relatively low cost and power consumption of the method is emphasized

  7. Broadband impedance calculations and single bunch instabilities estimations of of the HLS-II storage ring

    Science.gov (United States)

    Zhang, Qing-Kun; Wang, Lin; Li, Wei-Min; Gao, Wei-Wei

    2015-12-01

    The upgrade project of the Hefei Light Source storage ring is under way. In this paper, the broadband impedances of resistive wall and coated ceramic vacuum chamber are calculated using the analytic formula, and the wake fields and impedances of other designed vacuum chambers are simulated by CST code, and then a broadband impedance model is obtained. Using the theoretical formula, longitudinal and transverse single bunch instabilities are discussed. With the carefully-designed vacuum chamber, we find that the thresholds of the beam instabilities are higher than the beam current goal. Supported by Natural Science Foundation of China (11175182, 11175180)

  8. Isolation of Nanocrystalline Cellulose from oil palm empty fruit bunch – A response surface methodology study

    Directory of Open Access Journals (Sweden)

    Song Yee Kai

    2016-01-01

    Full Text Available The research work studied the extraction of Nano Crystalline Cellulose (NCC from oil palm empty fruit bunch (EFB, with aid of Response Surface Methodology (RSM. Particle size analysis using Malvern Zetasizer had confirmed the extracted NCC fall within the desired nano scaled range. The impact of three input parameters, namely concentration of NaOH solution during alkaline treatment, concentration of H2SO4 solution during acid hydrolysis, and duration for acid hydrolysis on NCC particle were investigated. From ANOVA study, it had suggested that the current RSM model is significant to interpret the interaction among the all three input parameters.

  9. Bunch-shape monitor for a picosecond single-bunch beam of a 35 MeV electron linear accelerator

    International Nuclear Information System (INIS)

    Hosono, Yoneichi; Nakazawa, Masaharu; Iguchi, Tetsuo

    1995-01-01

    A non-interactive-type bunch-shape and beam intensity monitor for a 35 MeV electron linear accelerator (linac) has been developed. The monitor consists of an electric SMA-type connector and an Al pipe of 50 mm inner diameter. Test measurements of the present monitor have been made under the conditions of the accelerated charges of lower than 27 nC/pulse and the pulse width ranging from 6 to 30 ps (Full Width at Half Maximum). The results show that the present monitor is applicable to bunch-shape measurement of the picosecond single-bunch beam. The monitor output is also found to be proportional to the beam intensity of more than 0.05 nC/pulse. (author)

  10. Observation of coherent Smith-Purcell and transition radiation driven by single bunch and micro-bunched electron beams

    Science.gov (United States)

    Liang, Yifan; Du, Yingchao; Su, Xiaolu; Wang, Dan; Yan, Lixin; Tian, Qili; Zhou, Zheng; Wang, Dong; Huang, Wenhui; Gai, Wei; Tang, Chuanxiang; Konoplev, I. V.; Zhang, H.; Doucas, G.

    2018-01-01

    Generation of coherent Smith-Purcell (cSPr) and transition/diffraction radiation using a single bunch or a pre-modulated relativistic electron beam is one of the growing research areas aiming at the development of radiation sources and beam diagnostics for accelerators. We report the results of comparative experimental studies of terahertz radiation generation by an electron bunch and micro-bunched electron beams and the spectral properties of the coherent transition and SP radiation. The properties of cSPr spectra are investigated and discussed, and excitations of the fundamental and second harmonics of cSPr and their dependence on the beam-grating separation are shown. The experimental and theoretical results are compared, and good agreement is demonstrated.

  11. Flat bunch creation and acceleration: a possible path for the LHC luminosity upgrade

    International Nuclear Information System (INIS)

    Bhat, C.M.

    2009-01-01

    Increasing the collider luminosity by replacing bunches having Gaussian line-charge distribution with flat bunches, but with same beam-beam tune shift at collision, has been studied widely in recent years. But, creation of 'stable' flat bunches (and their acceleration) using a multiple harmonic RF system has not been fully explored. Here, we review our experience with long flat bunches in the barrier RF buckets at Fermilab.We presentsome preliminary results from beam dynamics simulations and recent beam studies in the LHC injectors to create stable flat bunches using double harmonic RF systems. The results deduced from these studies will be used to model the necessary scheme for luminosity upgrade in the LHC. We have also described a viable (and economical) way for creation and acceleration of flat bunches in the LHC. The flat bunch scheme may have many advantages over the LHC baseline scenario, particularly because of the reduced momentum spread of the bunch for increased intensities.

  12. Increased short circuit current in organic photovoltaic using high-surface area electrode based on ZnO nanowires decorated with CdTe quantum dots.

    Science.gov (United States)

    Aga, R S; Gunther, D; Ueda, A; Pan, Z; Collins, W E; Mu, R; Singer, K D

    2009-11-18

    A photosensitized high-surface area transparent electrode has been employed to increase the short circuit current of a photovoltaic device with a blend of poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM) as the active layer. This is achieved by directly growing ZnO nanowires on indium tin oxide (ITO) film via a physical vapor method. The nanowire surface is then decorated with CdTe quantum dots by pulsed electron-beam deposition (PED). The nanowires alone provided a 20-fold increase in the short circuit current under visible light illumination. This was further increased by a factor of approximately 1.5 by the photosensitization effect of CdTe, which has an optical absorption of up to 820 nm.

  13. Concurrent Validity and Feasibility of Short Tests Currently Used to Measure Early Childhood Development in Large Scale Studies.

    Directory of Open Access Journals (Sweden)

    Marta Rubio-Codina

    Full Text Available In low- and middle-income countries (LIMCs, measuring early childhood development (ECD with standard tests in large scale surveys and evaluations of interventions is difficult and expensive. Multi-dimensional screeners and single-domain tests ('short tests' are frequently used as alternatives. However, their validity in these circumstances is unknown. We examined the feasibility, reliability, and concurrent validity of three multi-dimensional screeners (Ages and Stages Questionnaires (ASQ-3, Denver Developmental Screening Test (Denver-II, Battelle Developmental Inventory screener (BDI-2 and two single-domain tests (MacArthur-Bates Short-Forms (SFI and SFII, WHO Motor Milestones (WHO-Motor in 1,311 children 6-42 months in Bogota, Colombia. The scores were compared with those on the Bayley Scales of Infant and Toddler Development (Bayley-III, taken as the 'gold standard'. The Bayley-III was given at a center by psychologists; whereas the short tests were administered in the home by interviewers, as in a survey setting. Findings indicated good internal validity of all short tests except the ASQ-3. The BDI-2 took long to administer and was expensive, while the single-domain tests were quickest and cheapest and the Denver-II and ASQ-3 were intermediate. Concurrent validity of the multi-dimensional tests' cognitive, language, and fine motor scales with the corresponding Bayley-III scale was low below 19 months. However, it increased with age, becoming moderate-to-high over 30 months. In contrast, gross motor scales' concurrence was high under 19 months and then decreased. Of the single-domain tests, the WHO-Motor had high validity with gross motor under 16 months, and the SFI and SFII expressive scales showed moderate correlations with language under 30 months. Overall, the Denver-II was the most feasible and valid multi-dimensional test and the ASQ-3 performed poorly under 31 months. By domain, gross motor development had the highest concurrence

  14. Analysis of the impact of connecting a larger number of small hydroelectric power plants to the short-circuit currents values and relay protection system of distribution network

    Directory of Open Access Journals (Sweden)

    Sučević Nikola

    2017-01-01

    Full Text Available In this paper the influence of a large number of small hydro power plants on the short-circuit currents is analysed, as well as the operation of the relay protection system within the real distribution network in Serbia. The necessary modification of the existing protection functions, as well as the implementation of the new proposed protection functions, are presented and discussed. Network modeling and analysis are performed using the program tool DIgSILENT PowerFactory.

  15. Controlled Conjugated Backbone Twisting for an Increased Open-Circuit Voltage while Having a High Short-Circuit Current in Poly(hexylthiophene) Derivatives

    KAUST Repository

    Ko, Sangwon

    2012-03-21

    Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-circuit voltages in solar cells, though with decreased short-circuit current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-circuit voltage and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone-due to an increase in the polymer ionization potential-while the short-circuit current decreased as a result of a larger optical gap and lower hole mobility. A controlled, moderate degree of twist along the poly(3,4-dihexyl-2,2′:5′,2′′- terthiophene) (PDHTT) conjugated backbone led to a 19% enhancement in the open-circuit voltage (0.735 V) vs poly(3-hexylthiophene)-based devices, while similar short-circuit current densities, fill factors, and hole-carrier mobilities were maintained. These factors resulted in a power conversion efficiency of 4.2% for a PDHTT:[6,6]-phenyl-C 71-butyric acid methyl ester (PC 71BM) blend solar cell without thermal annealing. This simple approach reveals a molecular design avenue to increase open-circuit voltage while retaining the short-circuit current. © 2012 American

  16. Controlled conjugated backbone twisting for an increased open-circuit voltage while having a high short-circuit current in poly(hexylthiophene) derivatives.

    Science.gov (United States)

    Ko, Sangwon; Hoke, Eric T; Pandey, Laxman; Hong, Sanghyun; Mondal, Rajib; Risko, Chad; Yi, Yuanping; Noriega, Rodrigo; McGehee, Michael D; Brédas, Jean-Luc; Salleo, Alberto; Bao, Zhenan

    2012-03-21

    Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-circuit voltages in solar cells, though with decreased short-circuit current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-circuit voltage and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone--due to an increase in the polymer ionization potential--while the short-circuit current decreased as a result of a larger optical gap and lower hole mobility. A controlled, moderate degree of twist along the poly(3,4-dihexyl-2,2':5',2''-terthiophene) (PDHTT) conjugated backbone led to a 19% enhancement in the open-circuit voltage (0.735 V) vs poly(3-hexylthiophene)-based devices, while similar short-circuit current densities, fill factors, and hole-carrier mobilities were maintained. These factors resulted in a power conversion efficiency of 4.2% for a PDHTT:[6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM) blend solar cell without thermal annealing. This simple approach reveals a molecular design avenue to increase open-circuit voltage while retaining the short-circuit current.

  17. Observation of the substructure in the electron bunch on the ACO storage ring

    International Nuclear Information System (INIS)

    Bergher, M.; Velghe, M.; Mialocq, J.P.

    1984-09-01

    In the future, one interesting point of the SRFEL at Orsay will be the microtemporal analysis of the laser beam correlated with that of the electron bunch. In a first time, we have only analysed the temporal structure of the electron bunch with an Electrophotonic streak camera. The first results seem to indicate that the bunch is not an homogeneous bunch but presents a substructure. We discuss with details this data

  18. Hybrid solar cells with outstanding short-circuit currents based on a room temperature soft-chemical strategy: the case of P3HT:Ag2S.

    Science.gov (United States)

    Lei, Yan; Jia, Huimin; He, Weiwei; Zhang, Yange; Mi, Liwei; Hou, Hongwei; Zhu, Guangshan; Zheng, Zhi

    2012-10-24

    P3HT:Ag(2)S hybrid solar cells with broad absorption from the UV to NIR band were directly fabricated on ITO glass by using a room temperature, low energy consumption, and low-cost soft-chemical strategy. The resulting Ag(2)S nanosheet arrays facilitate the construction of a perfect percolation structure with organic P3HT to form ordered bulk heterojunctions (BHJ); without interface modification, the assembled P3HT:Ag(2)S device exhibits outstanding short-circuit current densities (J(sc)) around 20 mA cm(-2). At the current stage, the optimized device exhibited a power conversion efficiency of 2.04%.

  19. On-current modeling of short-channel double-gate (DG) MOSFETs with a vertical Gaussian-like doping profile

    International Nuclear Information System (INIS)

    Dubey, Sarvesh; Jit, S.; Tiwari Pramod Kumar

    2013-01-01

    An analytic drain current model is presented for doped short-channel double-gate MOSFETs with a Gaussian-like doping profile in the vertical direction of the channel. The present model is valid in linear and saturation regions of device operation. The drain current variation with various device parameters has been demonstrated. The model is made more physical by incorporating the channel length modulation effect. Parameters like transconductance and drain conductance that are important in assessing the analog performance of the device have also been formulated. The model results are validated by numerical simulation results obtained by using the commercially available ATLAS™, a two dimensional device simulator from SILVACO. (semiconductor devices)

  20. Development of a safety case for the use of current limiting devices to manage short circuit currents on electrical distribution networks. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    The original objective of this study was to review the safety issues associated with the use of current limiting devices and to write a risk assessment in accordance with good practice. But, when legislative procedures became apparent, the scope was changed to include involvement with the HSE, the DTI and Ofgem. It turned out that it would have been very difficult to write a safety case that would satisfy all of the agencies, or a risk assessment that would cover all applications. The scope of the study was therefore changed to focus on how the existing barriers should be tackled and the implications of the existing legislation. The approach to the study is described; it included reviews of background information and literature, questionnaires to manufacturers, a review of the reliability and hazards of the devices, and a review of UK safety legislation. The Final Report describes all this and includes discussion on the consequences of failure of fault current limiting devices, control measures which could be used to minimise risk, and recommendations for a way forward.