A large area CsI RICH Detector in ALICE at LHC

CERN Document Server

Di Bari, D; Davenport, Martyn; Di Mauro, A; Elia, D; Ghidini, B; Grimaldi, A; Martinengo, P; Monno, E; Morsch, Andreas; Nappi, E; Paic, G; Piuz, François; Posa, F; Santiard, Jean-Claude; Stucchi, S; Tomasicchio, G; Williams, T D

1999-01-01

A 1m2 CsI RICH prototype has been successfully tested in a hadron beam at CERN SPS. The prototype, fully equipped with 15k electronic channels, has been used to identify particles coming from pi-Be interactions. Track reconstruction has been performed by using a telescope consisting of four gas pad chambers. A detailed description of the detector will be presented and results from the test will be discussed.List of figuresFigure 1 Expected proton and antiproton yields including jet quenching mechanism in central Pb-Pb collisions at LHC.Figure 2 Schematic view of the HMPID CsI-RICHFigure 3 Experimental layout used at the SPS/H4 test beamFigure 4 Distributions of the mean number, per ring, of pad hits (Npad), electrons (Ntot) and Cherenkov photoelectrons (Nres) as a function of the single-electron mean pulse heightFigure 5 Mean single-electron pulse height as a function of high voltage measured at the centre of each of the four photocathodesFigure 6 Evaluation of the uniformity of the chamber gain for the photo...

Photocathode development

International Nuclear Information System (INIS)

Hinrichs, C.K.; Estrella, R.M.

1979-01-01

A research program for the development of photocathodes for use in streak image tubes is described. This is one task in the development of a high-resolution, high-speed x-ray streak camera system whose primary application is for diagnostics in underground nuclear testing. There are three objectives in the photocathode development program: (1) the development of new x-ray photocathodes compatible with the requirements of streak tubes; (2) the development of the capability to process high-quality visible light photocathodes as well as x-ray photocathodes; and (3) the design and construction of a transfer photocathode system. Design and construction of all the major components of the transfer photocathode system were completed. Assembly should be completed in early FY 80

Photocathode

Energy Technology Data Exchange (ETDEWEB)

Opachich, Yekaterina; MacPhee, Andrew

2017-12-05

A photocathode designs that leverage the grazing incidence geometry yield improvements through the introduction of recessed structures, such as cones, pyramids, pillars or cavities to the photocathode substrate surface. Improvements in yield of up to 20 times have been shown to occur in grazing incidence geometry disclosed herein due to a larger path length of the X-ray photons which better matches the secondary electron escape depth within the photocathode material. A photocathode includes a substrate having a first side and a second side, the first side configured to receive x-ray energy and the second side opposing the first side. A structured surface is associated with the second side of the substrate such that the structured surface includes a plurality of recesses from the second side of the substrate into the substrate.

Masked Photocathode for Photoinjector

International Nuclear Information System (INIS)

Qiang, Ji

2010-01-01

In this research note, we propose a scheme to insert a photocathode inside a photoinjector for generating high brightness electron beam. Instead of mounting the photocathode onto the electrode, a masked electrode with small hole is used to shield the photocathode from the accelerating vacuum chamber. Using such a masked photocathode will make the replacement of photocathode material very simple by rotating the photocathode behind the mask into the hole. This will significantly increase the usage lifetime of a photocathode. Furthermore, this also helps reduce the dark current or secondary electron emission from the photocathode. The hole on the mask also provides a transverse cut-off to the Gaussian laser profile which can be beneficial from the beam dynamics point of view.

Quantum efficiency of cesium iodide photocathodes in the 120-220 nm spectral range traceable to a primary detector standard

CERN Document Server

Rabus, H; Richter, M; Ulm, G; Friese, J; Gernhäuser, R; Kastenmüller, A; Maier-Komor, P; Zeitelhack, K

1999-01-01

Differently prepared CsI samples have been investigated in the 120-220 nm spectral range for their quantum efficiency, spatial uniformity and the effect of radiation aging. The experiments were performed at the PTB radiometry laboratory at the Berlin synchrotron radiation facility BESSY. A calibrated GaAsP Schottky photodiode was used as transfer detector standard to establish traceability to the primary detector standard, because this type of photodiode - unlike silicon p-on-n photodiodes - proved to be of sufficiently stable response when exposed to vacuum ultraviolet radiation. The paper reviews the experimental procedures that were employed to characterize and calibrate the GaAsP photodiode and reports the results that were obtained on the investigated CsI photocathodes.

CSI cardiac prevent 2015

Directory of Open Access Journals (Sweden)

S Ramakrishnan

2015-01-01

Full Text Available The CSI Cardiac Prevent 2015 was held at Hotel Taj Palace, New Delhi, on September 25-27, 2015. The major challenge was to create interest among cardiologists and physicians on preventive cardiology, a neglected area. The theme of the conference was "Innovations in Heart Disease Prevention.′′ This conference included "CSI at WHF Roadmap Workshop, Inauguration Ceremony, scientific program, plenary sessions, Nursing/Dietician track, Industry Exhibition, Social Events," Great India blood pressure Survey, and CSI Smart Heart App. A total of 848 delegates/faculties attended this conference against a total of 1140 people registered for the meeting.

Polarization and charge limit studies of strained GaAs photocathodes

International Nuclear Information System (INIS)

Saez, P.J.

1997-03-01

This thesis presents studies on the polarization and charge limit behavior of electron beams produced by strained GaAs photocathodes. These photocathodes are the source of high-intensity, high-polarization electron beams used for a variety of high-energy physics experiments at the Stanford Linear Accelerator Center. Recent developments on P-type, biaxially-strained GaAs photocathodes have produced longitudinal polarization in excess of 80% while yielding beam intensities of ∼ 2.5 A/cm 2 at an operating voltage of 120 kV. The SLAC Gun Test Laboratory, which has a replica of the SLAC injector, was upgraded with a Mott polarimeter to study the polarization properties of photocathodes operating in a high-voltage DC gun. Both the maximum beam polarization and the maximum charge obtainable from these photocathodes have shown a strong dependence on the wavelength of illumination, on the doping concentration, and on the negative electron affinity levels. The experiments performed for this thesis included studying the effects of temperature, cesiation, quantum efficiency, and laser intensity on the polarization of high-intensity beams. It was found that, although low temperatures have been shown to reduce the spin relaxation rate in bulk semiconductors, they don't have a large impact on the polarization of thin photocathodes. It seems that the short active region in thin photocathodes does not allow spin relaxation mechanisms enough time to cause depolarization. Previous observations that lower QE areas on the photocathode yield higher polarization beams were confirmed. In addition, high-intensity, small-area laser pulses were shown to produce lower polarization beams. Based on these results, together with some findings in the existing literature, a new proposal for a high-intensity, high-polarization photocathode is given. It is hoped that the results of this thesis will promote further investigation on the properties of GaAs photocathodes

CSI cardiac prevent 2015

OpenAIRE

S Ramakrishnan; Manisha Kaushik

2015-01-01

The CSI Cardiac Prevent 2015 was held at Hotel Taj Palace, New Delhi, on September 25-27, 2015. The major challenge was to create interest among cardiologists and physicians on preventive cardiology, a neglected area. The theme of the conference was "Innovations in Heart Disease Prevention.′′ This conference included "CSI at WHF Roadmap Workshop, Inauguration Ceremony, scientific program, plenary sessions, Nursing/Dietician track, Industry Exhibition, Social Events," Great India blood pressur...

A Masked Photocathode in a Photoinjector

OpenAIRE

Qiang, Ji

2011-01-01

In this paper, we propose a masked photocathode inside a photoinjector for generating high brightness electron beam. Instead of mounting the photocathode onto an electrode, an electrode with small hole is used as a mask to shield the photocathode from the accelerating vacuum chamber. Using such a masked photocathode will make the replacement of photocathode material easy by rotating the photocathode behind the electrode into the hole. Furthermore, this helps reduce the dark current or seconda...

Carbon nanotube based photocathodes

International Nuclear Information System (INIS)

Hudanski, Ludovic; Minoux, Eric; Schnell, Jean-Philippe; Xavier, Stephane; Pribat, Didier; Legagneux, Pierre; Gangloff, Laurent; Teo, Kenneth B K; Robertson, John; Milne, William I

2008-01-01

This paper describes a novel photocathode which is an array of vertically aligned multi-walled carbon nanotubes (MWCNTs), each MWCNT being associated with one p-i-n photodiode. Unlike conventional photocathodes, the functions of photon-electron conversion and subsequent electron emission are physically separated. Photon-electron conversion is achieved with p-i-n photodiodes and the electron emission occurs from the MWCNTs. The current modulation is highly efficient as it uses an optically controlled reconfiguration of the electric field at the MWCNT locations. Such devices are compatible with high frequency and very large bandwidth operation and could lead to their application in compact, light and efficient microwave amplifiers for satellite telecommunication. To demonstrate this new photocathode concept, we have fabricated the first carbon nanotube based photocathode using silicon p-i-n photodiodes and MWCNT bunches. Using a green laser, this photocathode delivers 0.5 mA with an internal quantum efficiency of 10% and an I ON /I OFF ratio of 30

Photocathode non-uniformity contribution to the energy resolution of scintillators

International Nuclear Information System (INIS)

Mottaghian, M.; Koohi-Fayegh, R.; Ghal-Eh, N.; Etaati, G. R.

2010-01-01

This paper introduces the basics of the light transport simulation in scintillators and the wavelength-dependencies in the process. The non-uniformity measurement of the photocathode surface is undertaken, showing that for the photocathode used in this study the quantum efficiency falls to about 4% of its maximum value, especially in areas far from the centre. The wavelength-and position-dependent quantum efficiency is implemented in the Monte Carlo light transport code, showing that, the contribution of the photocathode non-uniformity to the energy resolution is estimated to be around 18%, when all position-and wavelength-dependencies are included. (authors)

Proton magnetic resonance chemical shift imaging (1H CSI)-directed stereotactic biopsy

International Nuclear Information System (INIS)

Son, B.-C.; Kim, B.-C.; Kang, J.-K.; Choi, B.-G.; Kim, E.-N.; Baik, H.-M.; Choe, B.-Y.; Naruse, S.

2001-01-01

Introduction. To add metabolic information during stereotactic biopsy target selection, the authors adopted proton chemical shift imaging ( 1 H CSI)-directed stereotactic biopsy. Currently, proton single voxel spectroscopy (SVS) technique has been reported in stereotactic biopsy. We performed 1 H CSI in combination with a stereotactic headframe and selected targets according to local metabolic information, and evaluated the pathological results. Patients and Method. The 1 H CSI-directed stereotactic biopsy was performed in four patients. 1 H CSI and conventional Gd-enhancement stereotactic MRI were performed simultaneously after the fitting of a stereotactic frame. After reconstructing the metabolic maps of N-acetylaspartate (NAA)/phosphocreatine (Cr), phosphocholine (Cho)/Cr, and Lactate/Cr ratios, focal areas of increased Cho/Cr ratio and Lac/Cr ratios were selected as target sites in the stereotactic MR images. Result. 1 H CSI is possible with the stereotactic headframe in place. No difficulty was experienced performing 1 H CSI or making a diagnosis. Pathological samples taken from areas of increased Cho/Cr ratios and decreased NAA/Cr ratios provided information upon increased cellularity, mitoses and cellular atypism, and facilitated diagnosis. Pathological samples taken from areas of increased Lac/ Cr ratio snowed predominant feature of necrosis. Conclusion. 1 H CSI was feasible with the stereotactic headframe in place. The final pathological results obtained were concordant with the local metabolic information from 1 H CSI. We believe that 1 H CSI-directed stereotactic biopsy has the potential to significantly improve the accuracy of stereotactic biopsy targeting. (author)

Absorption of optical power in an S-20 photocathode

CERN Document Server

Harmer, S W

2003-01-01

By considering a monochromatic plane wave obliquely incident upon a planar layer of S-20 photocathode material, deposited upon a non-absorbing glass substrate, the distribution of optical power absorbed within the layer can be resolved. This is important to the question of photocathode efficiency, as the absorbed light excites photoelectrons within the photocathode which then may pass from the photocathode into the vacuum of the photomultiplier tube and be collected and multiplied. The calculation uses the measured complex permittivity of an extended red S-20 photocathode in the wavelength range, 375-900 nm. The results show that thin film effects are important within the photocathode, as they give rise to interesting power absorption profiles. This information is invaluable in predicting optimum photocathode thickness for wavelength selective applications. Electromagnetic waves that are obliquely incident upon the photocathode are also considered in both transverse electric and transverse magnetic polarizati...

S1 photocathode image converter tubes

International Nuclear Information System (INIS)

Gex, F.; Bauduin, P.; Hammes, C.; Horville, P.; Fleurot, N.; Nail, M.

1984-08-01

The S1 photocathode was the first cathode available for practical applications; in spite of this its mechanism of photoemission has remained enigmatic. S1 semi-transparent photocathode is the only one that can be used to study the 1.06 μm neodynium laser pulses of less than 10 ps duration. This recent application and the difficulties to manufacture stable and sensitive S1 photocathode at this wavelength gave rise to new researches which aim is to have a better knowledge of this structure. We first review the recent results obtained at the Paris Observatory (research sponsored by the CEA) and report on the lifetime in the 1-μm range of the photocathodes processed four years ago. In a second part we will try to analyse the researches which have been investigated during these last ten years in different laboratories to determine the role of the main constituants (silver particles, Co oxydes) and their contributions to photoemission in order to improve the sensitivity and the stability of S1 photocathode

Amorphous NEA Silicon Photocathodes - A Robust RF Gun Electron Source. Final Report

International Nuclear Information System (INIS)

Mulhollan, Gregory A.

2009-01-01

Amorphous silicon (a-Si) has been shown to have great promise as a negative electron affinity visible wavelength photocathode suitable for radio frequency (RF) gun systems. The specific operating wavelength can be shifted by growing it as a germanium alloy (a-Si(1-x)Ge(x)) rather than as pure silicon. This class of photoemitters has been shown to possess a high degree of immunity to charged particle flux. Such particle flux can be a significant problem in the operation of other photocathodes in RF gun systems. Its emission characteristics in the form of current per unit area, or current density, and emission angle, or beam spread are well matched for use in RF guns. Photocathodes made of a-Si can be fabricated on a variety of substrates including those most commonly employed in RF gun systems. Such photocathodes can be made for operation in either transmission or reflection mode. By growing them utilizing radio frequency plasma enhanced chemical vapor deposition, the unit cost is quite low, the quality is high and it is straightforward to grow custom size substrates and full or limited regions to confine the electron emission to the desired area. Quality emitters have been fabricated on tantalum, molybdenum, tungsten, titanium, copper, stainless steel, float glass, borosilicate glass and gallium arsenide. In addition to performing well in dedicated test chambers, a-Si photocathodes have been shown to function well in self-contained vacuum tubes. In this employment, they are subjected to a strenuous environment. Successful operation in this configuration provides additional confidence in their application to high energy linac photoinjectors and potentially as part of reliable, low cost photocathode driven RF gun systems that could become ready replacements for the diode and triode guns used on medical accelerators. Their applications in stand-alone vacuum tubes is just beginning to be explored.

CSI Index Of Customer's Satisfaction Applied In The Area Of Public Transport

Science.gov (United States)

Poliaková, Adela

2015-06-01

In Western countries, the new visions are applied in quality control for an integrated public transport system. Public transport puts the customer at the centre of our decision making in achieving customer satisfaction with provided service. Sustainable surveys are kept among customers. A lot of companies are collecting huge databases containing over 30,000 voices of customers, which demonstrates the current satisfaction levels across the public transport service. Customer satisfaction with a provided service is a difficult task. In this service, the quality criteria are not clearly defined, and it is therefore difficult to define customer satisfaction. The paper introduces a possibility of CSI index application in conditions of the Slovak Republic transport area.

A Monte Carlo study of backscattering effects in the photoelectron emission from CsI into CH$_{4}$ and Ar-CH$_{4}$ mixtures

CERN Document Server

Escada, J; Rachinhas, P J B M; Lopes, J A M; Santos, F P; Távora, L M N; Conde, C A N; Stauffer, A D

2007-01-01

Monte Carlo simulation is used to investigate photoelectron backscattering effects in the emission from a CsI photocathode into CH4 and Ar-CH4 mixtures for incident monochromatic photons with energies Eph in the range 6.8 eV to 9.8 eV (182 nm to 127 nm), and photons from a continuous VUV Hg(Ar) lamp with a spectral distribution peaked at Eph = 6.7 eV (185 nm), considering reduced applied electric fields E/N in the 0.1 Td to 40 Td range. The addition of CH4 to a noble gas efficiently increases electron transmission and drift velocity, due to vibrational excitation of the molecules at low electron energies. Results are presented for the photoelectron transmission efficiencies f, where f is the fraction of the number of photoelectrons emitted from CsI which are transmitted through the gas as compared to vacuum. The dependence of f on Eph, E/N, and mixture composition is analyzed and explained in terms of electron scattering in the different gas media, and results are compared with available measurements. Electro...

Graphene shield enhanced photocathodes and methods for making the same

Science.gov (United States)

Moody, Nathan Andrew

2014-09-02

Disclosed are graphene shield enhanced photocathodes, such as high QE photocathodes. In certain embodiments, a monolayer graphene shield membrane ruggedizes a high quantum efficiency photoemission electron source by protecting a photosensitive film of the photocathode, extending operational lifetime and simplifying its integration in practical electron sources. In certain embodiments of the disclosed graphene shield enhanced photocathodes, the graphene serves as a transparent shield that does not inhibit photon or electron transmission but isolates the photosensitive film of the photocathode from reactive gas species, preventing contamination and yielding longer lifetime.

High-brightness electron beam evolution following laser-based cleaning of a photocathode

Directory of Open Access Journals (Sweden)

F. Zhou

2012-09-01

Full Text Available Laser-based techniques have been widely used for cleaning metal photocathodes to increase quantum efficiency (QE. However, the impact of laser cleaning on cathode uniformity and thereby on electron beam quality are less understood. We are evaluating whether this technique can be applied to revive photocathodes used for high-brightness electron sources in advanced x-ray free-electron laser (FEL facilities, such as the Linac Coherent Light Source (LCLS at the SLAC National Accelerator Laboratory. The laser-based cleaning was applied to two separate areas of the current LCLS photocathode on July 4 and July 26, 2011, respectively. The QE was increased by 8–10 times upon the laser cleaning. Since the cleaning, routine operation has exhibited a slow evolution of the QE improvement and comparatively rapid improvement of transverse emittance, with a factor of 3 QE enhancement over five months, and a significant emittance improvement over the initial 2–3 weeks following the cleaning. Currently, the QE of the LCLS photocathode is holding constant at about 1.2×10^{-4}, with a normalized injector emittance of about 0.3  μm for a 150-pC bunch charge. With the proper procedures, the laser-cleaning technique appears to be a viable tool to revive the LCLS photocathode. We present observations and analyses for the QE and emittance evolution in time following the laser-based cleaning of the LCLS photocathode, and comparison to the previous studies, the measured thermal emittance versus the QE and comparison to the theoretical model.

Optical telescopes for COMPASS RICH1 up-grade

CERN Document Server

Sulc, M; Alekseev, M; Angerer, H; Appolonio, M; Birsa, R; Bordalo, P; Bradamante, F; Bressan, A; Busso, L; Chiosso, V M; Ciliberti, P; Colantoni, M L; Costa, S; Dibiase, N; Dafni, T; Dalla Torre, S; Diaz, V; Duic, V; Delagnes, E; Deschamps, H; Eyrich, W; Faso, D; Ferrero, A; Finger, M; Finger, M Jr; Fischer, H; Gerassimov, S; Giorgi, M; Gobbo, B; Hagemann, R; von Harrach, D; Heinsius, F H; Joosten, R; Ketzer, B; Königsmann, K; Kolosov, V N; Konorov, I; Kramer, D; Kunne, F; Levorato, S; Maggiora, A; Magnon, A; Mann, A; Martin, A; Menon, G; Mutter, A; Nähle, O; Neyret, D; Nerling, F; Pagano, P; Paul, S; Panebianco, S; Panzieri, D; Pesaro, G; Pizzolotto, C; Polak, J; Rebourgeard, P; Rocco, E; Robinet, F; Schiavon, P; Schill, C; Schoenmeier, P; Silva, L; Slunecka, M; Steiger, L; Sozzi, F; Svec, M; Tessarotto, F; Teufel, A; Wollny, H

2006-01-01

The central photon detection area of the Ring Imaging Cherenkov detector at COMPASS, a particle physics experiment at CERN SPS dedicated to hadron physics, has been upgraded from the previous system formed by wire chambers with CsI layers to a very fast UV extended multi anode photo multiplier tube array (MAPMT), including 576 tubes. The active area covered by the MAPMTs is 7.3 times smaller than the one previously equipped with CsI photocathodes, so 576 optical concentrators transforming the image from the old system focal plane to the new photocathode plane were needed. The telescope system formed by two fused silica lenses was designed, produced and assembled. The first prismatic plano-convex field lens is placed in the focal plane of the RICH mirrors. The second condenser lens is off centered and tilted and has one aspherical surface. All lenses have antireflection coating.

Stable Solar-Blind Ultraviolet III-Nitride Photocathode for Astronomy Applications

Science.gov (United States)

Bell, Lloyd

In this effort, we propose to develop a new type of cesium-free photocathode using III- nitride materials (GaN, AlN, and their alloys) to achieve highly efficient, solar blind, and stable ultraviolet (UV) response. Currently, detectors used in UV instruments utilize a photocathode to convert UV photons into electrons that are subsequently detected by microchannel plate or CCD. The performance of these detectors critically depends on the efficiency and stability of their photocathodes. In particular, photocathode instability is responsible for many of the fabrication difficulties commonly experienced with this class of detectors. In recent years, III-nitride (in particular GaN) photocathodes have been demonstrated with very high quantum efficiency (>50%) in parts of UV spectral range; however, these photocathodes still rely on cesiation for activation. The proposed photocathode structure will achieve activation through methods for band structure engineering such as delta- doping and polarization field engineering. Compared to the current state-of-the-art in flight-ready microchannel plate/Cs2Te sealed tubes, photocathodes based on III-nitride materials will increase the quantum efficiency by nearly an order of magnitude and significantly enhance both fabrication yield and reliability, since they will not require cesium or other highly reactive materials for activation. This performance will enable a next-generation UV spectroscopic and imaging mission that is of high scientific priority for NASA. This photocathode uses near-surface band-structure engineering to create a permanently activated surface, with high efficiency and air-stable UV response. We will combine this III-nitride structure with our unique III-nitride processing technology to optimize the efficiency and uniformity of the photocathode. In addition, through our design, growth, and processing techniques, we will extend the application of these photocathodes into far UV for both semitransparent and

Proceedings of the workshop on photocathodes for polarized electron sources for accelerators

International Nuclear Information System (INIS)

Chatwell, M.; Clendenin, J.; Maruyama, T.; Schultz, D.

1994-04-01

Application of the GaAs polarized electron source to studies of surface magnetism; thermal stability of Cs on NES III-V-Photocathodes and its effect on quantum efficiency; AFEL accelerator; production and detection of SPIN polarized electrons; emittance measurements on a 100-keV beam from a GaAs photocathode electron gun; modern theory of photoemission and its applications to practical photocathodes; experimental studies of the charge limit phenomenon in GaAs photocathodes; new material for photoemission electron source; semiconductor alloy InGaAsP grown on GaAs substrate; NEA photocathode surface preparation; technology and physics; metalorganic chemical vapor deposition of GaAs-GaAsP spin-polarized photocathodes; development of photocathodes injectors for JLC-ATF; effect of radiation trapping on polarization of photoelectrons from semiconductors; and energy analysis of electrons emitted by a semiconductor photocathode

CSI Index Of Customer’s Satisfaction Applied In The Area Of Public Transport

Directory of Open Access Journals (Sweden)

Poliaková Adela

2015-06-01

Full Text Available In Western countries, the new visions are applied in quality control for an integrated public transport system. Public transport puts the customer at the centre of our decision making in achieving customer satisfaction with provided service. Sustainable surveys are kept among customers. A lot of companies are collecting huge databases containing over 30,000 voices of customers, which demonstrates the current satisfaction levels across the public transport service. Customer satisfaction with a provided service is a difficult task. In this service, the quality criteria are not clearly defined, and it is therefore difficult to define customer satisfaction. The paper introduces a possibility of CSI index application in conditions of the Slovak Republic transport area.

Imaging Hybrid Photon Detectors with a Reflective Photocathode

CERN Document Server

Ferenc, D

2000-01-01

Modern epitaxially grown photocathodes, like GaAsP, bring a very high inherent quantum efficiency, but are rather expensive due to the complicated manufacturing and mounting process. We argue that such photocathodes could be used in reflective mode, in order to avoid the risky and expensive removal of the epitaxial growth substrate. Besides that the quantum efficiency should increase considerably. In this paper we present results of the development of large imaging Hybrid Photon Detectors (HPDs), particularly designed for such reflective photocathodes.

A Stable, Non-Cesiated III-Nitride Photocathode for Ultraviolet Astronomy Application

Science.gov (United States)

Bell, Lloyd

In this effort, we propose to develop a new type of cesium-free photocathode using III-nitride (III-N) materials (GaN, AlN, and their alloys) and to achieve highly efficient, solar blind, and stable UV response. Currently, detectors used in UV instruments utilize a photocathode to convert UV photons into electrons that are subsequently detected by microchannel plate or CCD. The performance of these detectors critically depends on the efficiency and stability of their photocathodes. In particular, photocathode instability is responsible for many of the fabrication difficulties commonly experienced with this class of detectors. In recent years, III-N (in particular GaN) photocathodes have been demonstrated with very high QE (>50%) in parts of UV spectral range. Moreover, due to the wide bandgaps of III-nitride materials, photocathode response can be tailored to be intrinsically solar-blind. However, these photocathodes still rely on cesiation for activation, necessitating all-vacuum fabrication and sealed-tube operation. The proposed photocathode structure will achieve activation through methods for band structure engineering such as delta-doping and polarization field engineering. Compared to the current state-of-the-art in flight-ready microchannel plate sealed tubes, photocathodes based on III-N materials will yield high QE and significantly enhance both fabrication yield and reliability, since they do not require cesium or other highly reactive materials for activation. This performance will enable a ~4 meter medium class UV spectroscopic and imaging mission that is of high scientific priority for NASA. This work will build on the success of our previous APRA-funded effort. In that work, we demonstrated III-nitride photocathode operation without the use of cesium and stable response with respect to time. These accomplishments represent major improvements to the state-of-the-art for photocathode technologies. In the proposed effort, we will implement III

Jefferson Lab IR demo FEL photocathode quantum efficiency scanner

CERN Document Server

Gubeli, J; Grippo, A; Jordan, K; Shinn, M; Siggins, T

2001-01-01

Jefferson Laboratory's Free Electron Laser (FEL) incorporates a cesiated gallium arsenide (GaAs) DC photocathode gun as its electron source. By using a set of scanning mirrors, the surface of the GaAs wafer is illuminated with a 543.5nm helium-neon laser. Measuring the current flow across the biased photocathode generates a quantum efficiency (QE) map of the 1-in. diameter wafer surface. The resulting QE map provides a very detailed picture of the efficiency of the wafer surface. By generating a QE map in a matter of minutes, the photocathode scanner has proven to be an exceptional tool in quickly determining sensitivity and availability of the photocathode for operation.

RF gun using laser-triggered photocathode

International Nuclear Information System (INIS)

Akiyama, H.; Otake, Y.; Naito, T.; Takeuchi, Y.; Yoshioka, M.

1992-01-01

An RF gun using laser-triggered photocathode has many advantages as an injector of the linear colliders since it can generate a low emittance and high current pulsed beam. The experimental facility for the RF gun, such as an RF system, a laser system and a photocathode have been fabricated to study the fundamental characteristics. The dynamics of the RF gun has also studied by the 1D sheet beam model. (author)

Kelvin probe studies of cesium telluride photocathode for AWA photoinjector

Energy Technology Data Exchange (ETDEWEB)

Wisniewski, Eric E., E-mail: ewisniew@anl.gov [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Velazquez, Daniel [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Yusof, Zikri, E-mail: zyusof@hawk.iit.edu [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Spentzouris, Linda; Terry, Jeff [Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Sarkar, Tapash J. [Rice University, 6100 Main, Houston, TX 77005 (United States); Harkay, Katherine [Accelerator Science Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States)

2013-05-21

Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch (≈50nC) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating. -- Highlights: ► The correlation between Quantum Efficiency (QE) and work function. ► How QE and work function evolve together. ► Rejuvenation of the photocathode via heating and the effect on work function. ► The effects on the work function due to exposure to UV light.

Proceedings of the workshop on photocathodes for polarized electron sources for accelerators. Revision

Energy Technology Data Exchange (ETDEWEB)

Chatwell, M.; Clendenin, J.; Maruyama, T.; Schultz, D. [eds.

1994-04-01

Application of the GaAs polarized electron source to studies of surface magnetism; thermal stability of Cs on NES III-V-Photocathodes and its effect on quantum efficiency; AFEL accelerator; production and detection of SPIN polarized electrons; emittance measurements on a 100-keV beam from a GaAs photocathode electron gun; modern theory of photoemission and its applications to practical photocathodes; experimental studies of the charge limit phenomenon in GaAs photocathodes; new material for photoemission electron source; semiconductor alloy InGaAsP grown on GaAs substrate; NEA photocathode surface preparation; technology and physics; metalorganic chemical vapor deposition of GaAs-GaAsP spin-polarized photocathodes; development of photocathodes injectors for JLC-ATF; effect of radiation trapping on polarization of photoelectrons from semiconductors; and energy analysis of electrons emitted by a semiconductor photocathode.

Performance of photocathode rf gun electron accelerators

International Nuclear Information System (INIS)

Ben-Zvi, I.

1993-01-01

In Photo-Injectors (PI) electron guns, electrons are emitted from a photocathode by a short laser pulse and then accelerated by intense rf fields in a resonant cavity. The best known advantage of this technique is the high peak current with a good emittance (high brightness). This is important for short wavelength Free-Electron Lasers and linear colliders. PIs are in operation in many electron accelerator facilities and a large number of new guns are under construction. Some applications have emerged, providing, for example, very high pulse charges. PIs have been operated over a wide range of frequencies, from 144 to 3000 MHz (a 17 GHz gun is being developed). An exciting new possibility is the development of superconducting PIs. A significant body of experimental and theoretical work exists by now, indicating the criticality of the accelerator elements that follow the gun for the preservation of the PI's performance as well as possible avenues of improvements in brightness. Considerable research is being done on the laser and photocathode material of the PI, and improvement is expected in this area

SSRL photocathode RF gun test stand

International Nuclear Information System (INIS)

Hernandez, M.; Baltay, M.; Boyce, A.

1995-01-01

A photocathode RF gun test stand designed for the production and study of high brightness electron beams will be constructed at SSRL. The beam will be generated from a laser driven third generation photocathode RF gun being developed in collaboration with BNL, LBL, and UCLA. The 3-5 [MeV] beam from the gun will be accelerated using a SLAC three meter S-band accelerator section, in order to achieve the desired low emittance beam, emittance compensation with solenoidal focusing will be employed

Development of a high current 250 kV photocathode dc gun

International Nuclear Information System (INIS)

Nishimori, Nobuyuki; Nagai, Ryoji; Sawamura, Masaru; Hajima, Ryoichi

2016-01-01

We have developed a high current photocathode dc gun at JAEA for the next generation light sources such as an energy recovery linac and high-repetition rate X-ray free electron laser. The gun is equipped with a multialkali photocathode preparation system. Quantum efficiency of 0.37% at 532 nm was obtained for a Cs_3Sb photocathode. The gun was high voltage conditioned up to 230 kV with a cathode electrode. Beam generation test from the multialkali photocathode will be performed by the end of FY2015. (author)

Field assisted photoemission by silicon photocathodes

International Nuclear Information System (INIS)

Aboubacar, A.; Dupont, M.; El Manouni, A.; Querrou, M.; Says, L.P.

1991-01-01

Silicon photocathodes with arrays of tips have been prepared using microlithographic techniques. Current emission due to field effect has been measured in the case of heavy and weakly doped boron Silicon. An Argon continuous laser has been used to produce photocurrent. An instantaneous current (600 μA) with a moderate laser power (83 mW), has been produced on weakly doped photocathodes. This current corresponds to an average quantum yield (purely photoelectric) of about 1.7%, and a local current density in the range of a few 10 6 A m -2

Improved reconstruction for IDEAL spiral CSI

DEFF Research Database (Denmark)

Hansen, Rie Beck; Mariager, Christian; Laustsen, Christoffer

2017-01-01

In this study we demonstrate how reconstruction for IDEAL spiral CSI (spectroscopic imaging scheme developed for hyperpolarized dynamic metabolic MR imaging) can be improved by using regularization with a sparsity constraint. By exploiting sparsity of the spectral domain, IDEAL spiral CSI can...

Correlation of CsK2Sb photocathode lifetime with antimony thickness

Energy Technology Data Exchange (ETDEWEB)

Mamun, M. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Hernandez-Garcia, C. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Poelker, M. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Elmustafa, A. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA

2015-06-01

CsK2Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

Correlation of CsK2Sb photocathode lifetime with antimony thickness

Directory of Open Access Journals (Sweden)

M. A. Mamun

2015-06-01

Full Text Available CsK2Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

Cold electron beams from cryocooled, alkali antimonide photocathodes

Directory of Open Access Journals (Sweden)

L. Cultrera

2015-11-01

Full Text Available In this paper we report on the generation of cold electron beams using a Cs_{3}Sb photocathode grown by codeposition of Sb and Cs. By cooling the photocathode to 90 K we demonstrate a significant reduction in the mean transverse energy validating the long-standing speculation that the lattice temperature contributes to limiting the mean transverse energy or intrinsic emittance near the photoemission threshold, opening new frontiers in generating ultrabright beams. At 90 K, we achieve a record low intrinsic emittance of 0.2  μm (rms per mm of laser spot diameter from an ultrafast (subpicosecond photocathode with quantum efficiency greater than 7×10^{−5} using a visible laser wavelength of 690 nm.

Analyses of CsI aerosol deposition tests in WIND project with ART and VICTORIA codes

International Nuclear Information System (INIS)

Yuchi, Y.; Shibazaki, H.; Kudo, T.

2000-01-01

Deposition behavior of cesium iodide (CsI) was analyzed with ART and VICTORIA-92 codes for a test of the aerosol re-vaporization test series performed in WIND project at JAERI. In the test analyzed, CsI aerosol was injected into piping of test section where metaboric acid (HBO 2 ) was placed in advance on the floor area. It was confirmed in the present analysis that similar results on the CsI deposition were obtained between ART and VICTORIA when influences of chemical interactions were negligibly small. The analysis with VICTORIA agreed satisfactorily with the test results in analytical cases that cesium metaborate (CsBO 2 ) was injected into the test section instead of CsI to simulate the pre-existence of HBO 2 effect. (author)

SWCNT photocathodes sensitised with InP/ZnS core–shell nanocrystals

OpenAIRE

Macdonald, Thomas J.; Tune, Daniel D.; Dewi, Melissa R.; Bear, Joseph C.; McNaughter, Paul D.; Mayes, Andrew G.; Skinner, William M.; Parkin, Ivan P.; Shapter, Joseph G.; Nann, Thomas

2016-01-01

Increasing the light harvesting efficiency of photocathodes is an integral part of optimising the future efficiencies of solar technologies. In contrast to the more extensively studied photoanode systems, current state-of-the-art photocathodes are less efficient and are commonly replaced with rare and expensive materials such as platinum group metals. The significance of photocathodes is in the development of tandem electrodes, enhancing the performance of existing devices. Carbon nanotubes a...

SWCNT photocathodes sensitised with InP/ZnS core-shell nanocrystals

OpenAIRE

Macdonald, T. J.; Tune, D. D.; Dewi, M. R.; Bear, J. C.; McNaughter, P. D.; Mayes, A. G.; Skinner, W. M.; Parkin, I. P.; Shapter, J. G.; Nann, T.

2016-01-01

Increasing the light harvesting efficiency of photocathodes is an integral part of optimising the future efficiencies of solar technologies. In contrast to the more extensively studied photoanode systems, current state-of-the-art photocathodes are less efficient and are commonly replaced with rare and expensive materials such as platinum group metals. The significance of photocathodes is in the development of tandem electrodes, enhancing the performance of existing devices. Carbon nanotubes a...

Deposition of CsI aerosol in horizontal straight pipes in WIND project

International Nuclear Information System (INIS)

Sugimoto, J.; Maruyama, Y.; Igarashi, M.; Hidaka, A.; Maeda, A.; Harada, Y.; Hashimoto, K.

1996-01-01

In the WIND Project at Japan Atomic Energy Research Institute, the aerosol behaviors such as deposition, revaporization and resuspension have been investigated under the severe accident conditions. The present paper describes the deposition of CsI aerosol in horizontal straight pipes. The test results showed that the aerosol deposition depended on thermo-fluid dynamic characteristics of the carrier gas. In the test with the temperature gradient of the pipe, the deposition of CsI was remarkable within the downstream side, where the temperature of the gas was higher than that of the pipe wall. It is thus supposed that the major mechanism of the deposition was thermophoresis caused by the temperature gradient within the gas phase. However, circumferential distribution of the deposited CsI was influenced by the argon flow rate. In laminar flow case, larger amount of CsI was deposited on the ceiling than the floor area. Three-dimensional thermo-fluid dynamic analysis suggested that much sharper radial temperature gradient was developed within the gas near the ceiling area due to the formation of a natural convective secondary flow. This could result in the promotion of the thermophoretic aerosol deposition. On the other hand, slight circumferential distribution was observed in case of the high flow rate, probably due to a uniform temperature field. It was also found that the close coupling of the FP behavior and the detailed thermohydraulic analyses is essential in order to accurately predict the CsI deposition in the pipe. The findings on aerosol behaviors will also be utilized for the evaluation of sodium aerosol behaviors of fast reactors. (author)

Development of the CsI Calorimeter Subsystem for AMEGO

Science.gov (United States)

Grove, J. Eric; Woolf, Richard; Johnson, W. Neil; Phlips, Bernard

2018-01-01

We report on the development of the thallium-doped cesium iodide (CsI:Tl) calorimeter subsystem for the All-Sky Medium-Energy Gamma-ray Observatory (AMEGO). The CsI calorimeter is one of the three main subsystems that comprise the AMEGO instrument suite; the others include the double-sided silicon strip detector (DSSD) tracker/converter and a cadmium zinc telluride (CZT) calorimeter. Similar to the LAT instrument on Fermi, the hodoscopic calorimeter consists of orthogonally layered CsI bars. Unlike the LAT, which uses PIN photodiodes, the scintillation light readout from each end of the CsI bar is done with recently developed large-area silicon photomultiplier (SiPM) arrays. We currently have an APRA program to develop the calorimeter technology for a larger, future space-based gamma-ray observatory. Under this program, we are building and testing a prototype calorimeter consisting of 24 CsI bars (16.7 mm x 16.7 mm x 100 mm) arranged in 4 layers with 6 bars per layer. The ends of each bar are read out with a 2 x 2 array of 6 mm x 6 mm SensL J series SiPMs. Signal readout and processing is done with the IDEAS SIPHRA (IDE3380) ASIC. Performance testing of this prototype will be done with laboratory sources, a beam test, and a balloon flight in conjunction with the other subsystems led by NASA GSFC. Additionally, we will test 16.7 mm x 16.7 mm x 450 mm CsI bars with SiPM readout to understand the performance of longer bars in advance of the developing the full instrument.Acknowledgement: This work was sponsored by the Chief of Naval Research (CNR) and NASA-APRA (NNH15ZDA001N-APRA).

Fabrication and Measurement of Low Work Function Cesiated Dispenser Photocathodes

CERN Document Server

Moody, Nathan A; Jensen, Kevin

2005-01-01

Photoinjector performance is a limiting factor in the continued development of high powered FELs and electron beam-based accelerators. Presently available photocathodes are plagued with limited efficiency and short lifetime in an RF-gun environment, due to contamination or evaporation of a photosensitive surface layer. An ideal photocathode should have high efficiency at long wavelengths, long lifetime in practical vacuum environments, and prompt emission. Cathodes with high efficiency typically have limited lifetime, and vice versa, and the needs of the photocathode are generally at odds with those of the drive laser. A potential solution is the low work function dispenser cathode, where lifetime issues are overcome by periodic in situ regeneration that restores the photosensitive surface layer, analogous to those used in the microwave power tube industry. This work reports on the fabrication techniques and performance of cesiated metal photocathodes and cesiated dispenser cathodes, with a focus on understan...

Polarized Photocathode R&D for Future Linear Collliders

Energy Technology Data Exchange (ETDEWEB)

Zhou, F; Brachmann, A.; Maruyama, T.; Sheppard, J.C.; /SLAC

2009-01-23

It is a challenge to generate full charge electrons from the electron sources without compromising polarization for the proposed ILC and CLIC. It is essential to advance polarized photocathodes to meet the requirements. SLAC has worldwide unique dedicated test facilities, Cathode Test System and dc-Gun Test Laboratory, to fully characterize polarized photocathodes. Recent systematic measurements on a strained-well InAlGaAs/AlGaAs cathode at the facilities show that 87% polarization and 0.3% QE are achieved. The QE can be increased to {approx}1.0% with atomic hydrogen cleaning. The surface charge limit at a very low current intensity and the clear dependence of the polarization on the surface charge limit are observed for the first time. On-going programs to develop photocathodes for the ILC and CLIC are briefly introduced.

Correlation of CsK{sub 2}Sb photocathode lifetime with antimony thickness

Energy Technology Data Exchange (ETDEWEB)

Mamun, M. A., E-mail: mmamu001@odu.edu; Elmustafa, A. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States); The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Hernandez-Garcia, C.; Poelker, M. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

2015-06-01

CsK{sub 2}Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

Observation of Significant Quantum Efficiency Enhancement from a Polarized Photocathode with Distributed Bragg Reflector

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shukui [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Poelker, Matthew [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Stutzman, Marcy L. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Chen, Yiqiao [SVT Associates, Inc., Eden Prairie, MN (United States); Moy, Aaron [SVT Associates, Inc., Eden Prairie, MN (United States)

2015-09-01

Polarized photocathodes with higher Quantum efficiency (QE) would help to reduce the technological challenge associated with producing polarized beams at milliampere levels, because less laser light would be required, which simplifies photocathode cooling requirements. And for a given amount of available laser power, higher QE would extend the photogun operating lifetime. The distributed Bragg reflector (DBR) concept was proposed to enhance the QE of strained-superlattice photocathodes by increasing the absorption of the incident photons using a Fabry-Perot cavity formed between the front surface of the photocathode and the substrate that includes a DBR, without compromising electron polarization. Here we present recent results showing QE enhancement of a GaAs/GaAsP strained-superlattice photocathode made with a DBR structure. Typically, a GaAs/GaAsP strained-superlattice photocathode without DBR provides a QE of 1%, at a laser wavelength corresponding to peak polarization. In comparison, the GaAs/GaAsP strained-superlattice photocathodes with DBR exhibited an enhancement of over 2 when the incident laser wavelength was tuned to meet the resonant condition for the Fabry-Perot resonator.

A comparison of surface properties of metallic thin film photocathodes

CERN Document Server

Mistry, Sonal; Valizadeh, Reza; Jones, L.B; Middleman, Keith; Hannah, Adrian; Militsyn, B.L; Noakes, Tim

2017-01-01

In this work the preparation of metal photocathodes by physical vapour deposition magnetron sputtering has been employed to deposit metallic thin films onto Cu, Mo and Si substrates. The use of metallic cathodes offers several advantages: (i) metal photocathodes present a fast response time and a relative insensitivity to the vacuum environment (ii) metallic thin films when prepared and transferred in vacuum can offer smoother and cleaner emitting surfaces. The photocathodes developed here will ultimately be used in S-band Normal Conducting RF (NCRF) guns such as that used in VELA (Versatile Electron Linear Accelerator) and the proposed CLARA (Compact Linear Accelerator for Research and Applications) Free Electron Laser test facility. The samples grown on Si substrates were used to investigate the morphology and thickness of the film. The samples grown onto Cu and Mo substrates were analysed and tested as photocathodes in a surface characterisation chamber, where X-Ray Photoelectron spectroscopy (XPS) was emp...

Advanced 3D Photocathode Modeling and Simulations Final Report

International Nuclear Information System (INIS)

Dimitre A Dimitrov; David L Bruhwiler

2005-01-01

High brightness electron beams required by the proposed Next Linear Collider demand strong advances in photocathode electron gun performance. Significant improvement in the production of such beams with rf photocathode electron guns is hampered by the lack high-fidelity simulations. The critical missing piece in existing gun codes is a physics-based, detailed treatment of the very complex and highly nonlinear photoemission process

The effects of electromagnetic space-charge fields in RF photocathode guns

International Nuclear Information System (INIS)

Park, C.S.; Hess, M.

2010-01-01

In high-brightness rf photocathode guns, the effects of space-charge are important for electron bunches with high bunch charge. In an effort to accurately simulate the effects of these space-charge fields without the presence of numerical grid dispersion, a Green's function based code called IRPSS (Indiana Rf Photocathode Source Simulator) was developed. In this paper, we show the results of numerical simulations of the Argonne Wakefield Accelerator photocathode gun using IRPSS, and compare them with the results of an electrostatic Green's function version of IRPSS.

The TiO2 Refraction Film for CsI Scintillator

OpenAIRE

C. C. Chen; C. W. Hun; C. J. Wang; C. Y. Chen; J. S. Lin; K. J. Huang

2015-01-01

Cesium iodide (CsI) melt was injected into anodic aluminum oxide (AAO) template and was solidified to CsI column. The controllable AAO channel size (10~500 nm) can makes CsI column size from 10 to 500 nm in diameter. In order to have a shorter light irradiate from each singe CsI column top to bottom the AAO template was coated a TiO2 nano-film. The TiO2 film acts a refraction film and makes X-ray has a shorter irradiation path in the CsI crystal making a stronger the photo-electron signal. Wh...

Quality Assurance on Undoped CsI Crystals for the Mu2e Experiment

Science.gov (United States)

Atanov, N.; Baranov, V.; Budagov, J.; Davydov, Yu. I.; Glagolev, V.; Tereshchenko, V.; Usubov, Z.; Cervelli, F.; Di Falco, S.; Donati, S.; Morescalchi, L.; Pedreschi, E.; Pezzullo, G.; Raffaelli, F.; Spinella, F.; Colao, F.; Cordelli, M.; Corradi, G.; Diociaiuti, E.; Donghia, R.; Giovannella, S.; Happacher, F.; Martini, M.; Miscetti, S.; Ricci, M.; Saputi, A.; Sarra, I.; Echenard, B.; Hitlin, D. G.; Hu, C.; Miyashita, T.; Porter, F.; Zhang, L.; Zhu, R.-Y.; Grancagnolo, F.; Tassielli, G.; Murat, P.

2018-02-01

The Mu2e experiment is constructing a calorimeter consisting of 1,348 undoped CsI crystals in two disks. Each crystal has a dimension of 34 x 34 x 200 mm, and is readout by a large area silicon PMT array. A series of technical specifications was defined according to physics requirements. Preproduction CsI crystals were procured from three firms: Amcrys, Saint-Gobain and Shanghai Institute of Ceramics. We report the quality assurance on crystal's scintillation properties and their radiation hardness against ionization dose and neutrons. With a fast decay time of 30 ns and a light output of more than 100 p.e./MeV measured with a bi-alkali PMT, undoped CsI crystals provide a cost-effective solution for the Mu2e experiment.

Photoemission characteristics of thin GaAs-based heterojunction photocathodes

Energy Technology Data Exchange (ETDEWEB)

Feng, Cheng; Zhang, Yijun, E-mail: zhangyijun423@126.com; Qian, Yunsheng [Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094 (China); Shi, Feng [Science and Technology on Low-Light-Level Night Vision Laboratory, Xi' an 710065 (China); Zou, Jijun [Engineering Research Center of Nuclear Technology Application (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Zeng, Yugang [Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

2015-01-14

To better understand the different photoemission mechanism of thin heterojunction photocathodes, the quantum efficiency models of reflection-mode and transmission-mode GaAs-based heterojunction photocathodes are revised based on one-dimensional continuity equations, wherein photoelectrons generated from both the emission layer and buffer layer are taken into account. By comparison of simulated results between the revised and conventional models, it is found that the electron contribution from the buffer layer to shortwave quantum efficiency is closely related to some factors, such as the thicknesses of emission layer and buffer layer and the interface recombination velocity. Besides, the experimental quantum efficiency data of reflection-mode and transmission-mode AlGaAs/GaAs photocathodes are well fitted to the revised models, which confirm the applicability of the revised quantum efficiency models.

Developments on RICH detectors

International Nuclear Information System (INIS)

Besson, P.; Bourgeois, P.

1996-01-01

The RICH (ring imaging Cherenkov) detector which is dedicated to Cherenkov radiation detection is described. An improvement made by replacing photo sensible vapor with solid photocathode is studied. A RICH detector prototype with a CsI photocathode has been built in Saclay and used with Saturne. The first results are presented. (A.C.)

Engineering Design and Fabrication of an Ampere-Class Superconducting Photocathode Electron Gun

International Nuclear Information System (INIS)

Ben-Zvi, I.

2008-01-01

Over the past three years, Advanced Energy Systems and Brookhaven National Laboratory (BNL) have been collaborating on the design of an Ampere- class superconducting photocathode electron gun. BNL performed the physics design of the overall system and RF cavity under prior programs. Advanced Energy Systems (AES) is currently responsible for the engineering design and fabrication of the electron gun under contract to BNL. We will report on the engineering design and fabrication status of the superconducting photocathode electron gun. The overall configuration of the cryomodule will be reviewed. The layout of the hermitic string, space frame, shielding package, and cold mass will be discussed. The engineering design of the gun cavity and removable cathode will be presented in detail and areas of technical risk will be highlighted. Finally, the fabrication sequence and fabrication status of the gun cavity will be discussed

Surface science analysis of GaAs photocathodes following sustained electron beam delivery

Directory of Open Access Journals (Sweden)

V. Shutthanandan

2012-06-01

Full Text Available Degradation of the photocathode materials employed in photoinjectors represents a challenge for sustained operation of nuclear physics accelerators and high power free electron lasers (FEL. Photocathode quantum efficiency degradation is due to residual gases in the electron source vacuum system being ionized and accelerated back to the photocathode. These investigations are a first attempt to characterize the nature of the photocathode degradation, and employ multiple surface and bulk analysis techniques to investigate damage mechanisms including sputtering of the Cs-oxidant surface monolayer, other surface chemistry effects, and ion implantation. Surface and bulk analysis studies were conducted on two GaAs photocathodes, which were removed from the JLab FEL DC photoemission gun after delivering electron beam, and two control samples. The analysis techniques include helium ion microscopy, Rutherford backscattering spectrometry (RBS, atomic force microscopy, and secondary ion mass spectrometry (SIMS. In addition, two high-polarization strained superlattice GaAs photocathode samples, one removed from the continuous electron beam accelerator facility (CEBAF photoinjector and one unused, were also analyzed using transmission electron microscopy (TEM and SIMS. It was found that heat cleaning the FEL GaAs wafer introduces surface roughness, which seems to be reduced by prolonged use. The bulk GaAs samples retained a fairly well organized crystalline structure after delivering beam but show evidence of Cs depletion on the surface. Within the precision of the SIMS and RBS measurements, the data showed no indication of hydrogen implantation or lattice damage from ion back bombardment in the bulk GaAs wafers. In contrast, SIMS and TEM measurements of the strained superlattice photocathode show clear crystal damage in the wafer from ion back bombardment.

Evaluation of the photocathode laser transverse distribution

Energy Technology Data Exchange (ETDEWEB)

Saisa-ard, Chaipattana [DESY, Zeuthen (Germany); Chiang Mai Univ., Chiang Mai (Thailand); Krasilnikov, Mikhail; Vashchenko, Grygorii [DESY, Zeuthen (Germany)

2016-07-01

Many years experience of electron source developments at the photo injector test facility at DESY in Zeuthen (PITZ) show that the photocathode laser is the one of major tools to produce high brightness electron beams. The transverse distribution of the laser on the photocathode plays a significant role in the high brightness photo injector optimization. However, the imperfections in the laser beam profile according to the deviation from a radially homogeneous profile directly result in transversely distorted charged particle distributions. This includes inhomogeneous core as well as transverse halo which is due to not sharp edges around the core. The laser transverse distribution is measured at PITZ using a virtual cathode:this is a CCD camera located at the position which is optically equivalent to the photocathode position (so called virtual cathode). An algorithm is developed for the evaluation of the experimentally obtained transverse profiles. It fits a flat-top or an inhomogeneous rotational symmetric core with exponentially decaying tails to an experimental distribution. The MATLAB script with implemented algorithm is applied to a set of measured transverse laser distributions. Results of the analysis will be presented.

MIMO channel capacity with full CSI at Low SNR

KAUST Repository

Tall, Abdoulaye

2012-10-01

In this paper, we characterize the ergodic capacity of Multiple Input Multiple Output (MIMO) Rayleigh fading channels with full channel state information (CSI) at both the transmitter (CSI-T) and the receiver (CSI-R) at asymptotically low signal-to-noise ratio (SNR). A simple analytical expression of the capacity is derived for any number of transmit and receive antennas. This characterization clearly shows the substantial gain in terms of capacity over the no CSI-T case and gives a good insight on the effect of the number of antennas used. In addition, an On-Off transmission scheme is proposed and is shown to be asymptotically capacity-achieving. © 2012 IEEE.

Photocathode Optimization for a Dynamic Transmission Electron Microscope: Final Report

Energy Technology Data Exchange (ETDEWEB)

Ellis, P; Flom, Z; Heinselman, K; Nguyen, T; Tung, S; Haskell, R; Reed, B W; LaGrange, T

2011-08-04

The Dynamic Transmission Electron Microscope (DTEM) team at Harvey Mudd College has been sponsored by LLNL to design and build a test setup for optimizing the performance of the DTEM's electron source. Unlike a traditional TEM, the DTEM achieves much faster exposure times by using photoemission from a photocathode to produce electrons for imaging. The DTEM team's work is motivated by the need to improve the coherence and current density of the electron cloud produced by the electron gun in order to increase the image resolution and contrast achievable by DTEM. The photoemission test setup is nearly complete and the team will soon complete baseline tests of electron gun performance. The photoemission laser and high voltage power supply have been repaired; the optics path for relaying the laser to the photocathode has been finalized, assembled, and aligned; the internal setup of the vacuum chamber has been finalized and mostly implemented; and system control, synchronization, and data acquisition has been implemented in LabVIEW. Immediate future work includes determining a consistent alignment procedure to place the laser waist on the photocathode, and taking baseline performance measurements of the tantalum photocathode. Future research will examine the performance of the electron gun as a function of the photoemission laser profile, the photocathode material, and the geometry and voltages of the accelerating and focusing components in the electron gun. This report presents the team's progress and outlines the work that remains.

Performance of the Brookhaven photocathode rf gun

International Nuclear Information System (INIS)

Batchelor, K.; Ben-Zvi, I.; Fernow, R.C.; Fischer, J.; Fisher, A.S.; Gallardo, J.; Ingold, G.; Kirk, H.G.; Leung, K.P.; Malone, R.; Pogorelsky, I.; Srinivasan-Rao, T.; Rogers, J.; Tsang, T.; Sheehan, J.; Ulc, S.; Woodle, M.; Xie, J.; Zhang, R.S.; Lin, L.Y.; McDonald, K.T.; Russell, D.P.; Hung, C.M.; Wang, X.J.

1991-01-01

The Brookhaven Accelerator Test Facility (ATF) uses a photocathode rf gun to provide a high-brightness electron beam intended for FEL and laser-acceleration experiments. The rf gun consists of 1 1/2 cells driven at 2856 MHz in π-mode with a maximum cathode field of 100 MV/m. To achieve long lifetimes, the photocathode development concentrates on robust metals such as copper, yttrium and samarium. We illuminate these cathodes with a 10-ps, frequency-quadrupled Nd:YAG laser. We describe the initial operation of the gun, including measurements of transverse and longitudinal emittance, quantum efficiencies, and peak current. The results are compared to models

Ion Back-Bombardment of GaAs Photocathodes Inside DC High Voltage Electron Guns

CERN Document Server

Grames, Joseph M; Brittian, Joshua; Charles, Daniel; Clark, Jim; Hansknecht, John; Lynn Stutzman, Marcy; Poelker, Matthew; Surles-Law, Kenneth E

2005-01-01

The primary limitation for sustained high quantum efficiency operation of GaAs photocathodes inside DC high voltage electron guns is ion back-bombardment of the photocathode. This process results from ionization of residual gas within the cathode/anode gap by the extracted electron beam, which is subsequently accelerated backwards to the photocathode. The damage mechanism is believed to be either destruction of the negative electron affinity condition at the surface of the photocathode or damage to the crystal structure by implantation of the bombarding ions. This work characterizes ion formation within the anode/cathode gap for gas species typical of UHV vacuum chambers (i.e., hydrogen, carbon monoxide and methane). Calculations and simulations are performed to determine the ion trajectories and stopping distance within the photocathode material. The results of the simulations are compared with test results obtained using a 100 keV DC high voltage GaAs photoemission gun and beamline at currents up to 10 mA D...

Iterative Equalization and Interference Alignment for Multiuser MIMO HetNets with Imperfect CSI

Directory of Open Access Journals (Sweden)

Daniel Castanheira

2015-01-01

Full Text Available In this paper we consider a scenario, where several small-cells work under the same coverage area and spectrum of a macrocell. The signals stemming from the small-cell (macrocell users if not carefully dealt with will generate harmful interference into the macrocell (small-cell. To tackle this problem interference alignment and iterative equalization techniques are considered. By using IA all interference generated by the small-cell (macrocell users is aligned along a low dimensional subspace, at the macrocell (small-cells. This reduces considerably the amount of resources allocated, to enable the coexistence of the two systems. However, perfect IA requires the availability of error-free channel state information (CSI at the transmitters. Due to CSI errors one can have substantial performance degradation due to imperfect alignments. Since in this work the IA precoders are based on imperfect CSI, an efficient iterative space-frequency equalization is designed at the receiver side to cope with the residual aligned interference. The results demonstrate that iterative equalization is robust to imperfect CSI and removes efficiently the interference generated by the poorly aligned interference. Close to matched filter bound performance is achieved, with a very few number of iterations.

Cs2Te normal conducting photocathodes in the superconducting rf gun

CERN Document Server

Xiang, R; Buettig, H; Janssen, D; Justus, M; Lehnert, U; Michel, P; Murcek, P; Schamlott, A; Schneider, Ch; Schurig, R; Staufenbiel, F; Teichert, J

2010-01-01

The superconducting radio frequency photoinjector (SRF gun) is one of the latest applications of superconducting rf technology in the accelerator field. Since superconducting photocathodes with high quantum efficiency are yet unavailable, normal conducting cathode material is the main choice for SRF photoinjectors. However, the compatibility between the photocathode and the cavity is one of the challenges for this concept. Recently, a SRF gun with Cs2Te cathode has been successfully operated in Forschungszentrum Dresden-Rossendorf. In this paper, we will present the physical properties of Cs2Te photocathodes in the SC cavity, such as the quantum efficiency, the lifetime, the rejuvenation, the charge saturation, and the dark current.

Photocathode operation of a thermionic RF gun

International Nuclear Information System (INIS)

Thorin, S.; Cutic, N.; Lindau, F.; Werin, S.; Curbis, F.

2009-01-01

The thermionic RF gun using a BaO cathode at the MAX-lab linac injector has been successfully commissioned for additional operation as a photocathode gun. By retaining the BaO cathode, lowering the temperature below thermal emission and illuminating it with a UV (263 nm) 9 ps laser pulse a reduced emittance and enhanced emission control has been achieved. Measurements show a normalised emittance of 5.5 mm mrad at 200 pC charge and a maximum quantum efficiency of 1.1x10 -4 . The gun is now routinely switched between storage ring injections in thermionic mode and providing a beam for the MAX-lab test FEL in photocathode mode.

Relay Precoder Optimization in MIMO-Relay Networks With Imperfect CSI

KAUST Repository

Pandarakkottilil, Ubaidulla

2011-11-01

In this paper, we consider robust joint designs of relay precoder and destination receive filters in a nonregenerative multiple-input multiple-output (MIMO) relay network. The network consists of multiple source-destination node pairs assisted by a MIMO-relay node. The channel state information (CSI) available at the relay node is assumed to be imperfect. We consider robust designs for two models of CSI error. The first model is a stochastic error (SE) model, where the probability distribution of the CSI error is Gaussian. This model is applicable when the imperfect CSI is mainly due to errors in channel estimation. For this model, we propose robust minimum sum mean square error (SMSE), MSE-balancing, and relay transmit power minimizing precoder designs. The next model for the CSI error is a norm-bounded error (NBE) model, where the CSI error can be specified by an uncertainty set. This model is applicable when the CSI error is dominated by quantization errors. In this case, we adopt a worst-case design approach. For this model, we propose a robust precoder design that minimizes total relay transmit power under constraints on MSEs at the destination nodes. We show that the proposed robust design problems can be reformulated as convex optimization problems that can be solved efficiently using interior-point methods. We demonstrate the robust performance of the proposed design through simulations. © 2011 IEEE.

Comparative research on the transmission-mode GaAs photocathodes of exponential-doping structures

International Nuclear Information System (INIS)

Chen Liang; Qian Yun-Sheng; Zhang Yi-Jun; Chang Ben-Kang

2012-01-01

Early research has shown that the varied doping structures of the active layer of GaAs photocathodes have been proven to have a higher quantum efficiency than uniform doping structures. On the basis of our early research on the surface photovoltage of GaAs photocathodes, and comparative research before and after activation of reflection-mode GaAs photocathodes, we further the comparative research on transmission-mode GaAs photocathodes. An exponential doping structure is the typical varied doping structure that can form a uniform electric field in the active layer. By solving the one-dimensional diffusion equation for no equilibrium minority carriers of transmission-mode GaAs photocathodes of the exponential doping structure, we can obtain the equations for the surface photovoltage (SPV) curve before activation and the spectral response curve (SRC) after activation. Through experiments and fitting calculations for the designed material, the body-material parameters can be well fitted by the SPV before activation, and proven by the fitting calculation for SRC after activation. Through the comparative research before and after activation, the average surface escape probability (SEP) can also be well fitted. This comparative research method can measure the body parameters and the value of SEP for the transmission-mode GaAs photocathode more exactly than the early method, which only measures the body parameters by SRC after activation. It can also help us to deeply study and exactly measure the parameters of the varied doping structures for transmission-mode GaAs photocathodes, and optimize the Cs-O activation technique in the future. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Cs_{2}Te normal conducting photocathodes in the superconducting rf gun

Directory of Open Access Journals (Sweden)

R. Xiang

2010-04-01

Full Text Available The superconducting radio frequency photoinjector (SRF gun is one of the latest applications of superconducting rf technology in the accelerator field. Since superconducting photocathodes with high quantum efficiency are yet unavailable, normal conducting cathode material is the main choice for SRF photoinjectors. However, the compatibility between the photocathode and the cavity is one of the challenges for this concept. Recently, a SRF gun with Cs_{2}Te cathode has been successfully operated in Forschungszentrum Dresden-Rossendorf. In this paper, we will present the physical properties of Cs_{2}Te photocathodes in the SC cavity, such as the quantum efficiency, the lifetime, the rejuvenation, the charge saturation, and the dark current.

Photocathodes for High Repetition Rate Light Sources

Energy Technology Data Exchange (ETDEWEB)

Ben-Zvi, Ilan [Stony Brook Univ., NY (United States). Dept. of Physics and Astronomy. Center for Accelerator Science and Education

2014-04-20

This proposal brought together teams at Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL) and Stony Brook University (SBU) to study photocathodes for high repetition rate light sources such as Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). Below details the Principal Investigators and contact information. Each PI submits separately for a budget through his corresponding institute. The work done under this grant comprises a comprehensive program on critical aspects of the production of the electron beams needed for future user facilities. Our program pioneered in situ and in operando diagnostics for alkali antimonide growth. The focus is on development of photocathodes for high repetition rate Free Electron Lasers (FELs) and Energy Recovery Linacs (ERLs), including testing SRF photoguns, both normal-­conducting and superconducting. Teams from BNL, LBNL and Stony Brook University (SBU) led this research, and coordinated their work over a range of topics. The work leveraged a robust infrastructure of existing facilities and the support was used for carrying out the research at these facilities. The program concentrated in three areas: a) Physics and chemistry of alkali-­antimonide cathodes (BNL – LBNL) b) Development and testing of a diamond amplifier for photocathodes (SBU -­ BNL) c) Tests of both cathodes in superconducting RF photoguns (SBU) and copper RF photoguns (LBNL) Our work made extensive use of synchrotron radiation materials science techniques, such as powder-­ and single-­crystal diffraction, x-­ray fluorescence, EXAFS and variable energy XPS. BNL and LBNL have many complementary facilities at the two light sources associated with these laboratories (NSLS and ALS, respectively); use of these will be a major thrust of our program and bring our understanding of these complex materials to a new level. In addition, CHESS at Cornell will be used to continue seamlessly throughout the NSLS dark period and

JAERI 200 kV electron gun with an NEA-GaAs photocathode

International Nuclear Information System (INIS)

Nishitani, Tomohiro; Minehara, Eisuke J.; Hajima, Ryoichi; Nagai, Ryoji; Sawamura, Masaru; Nishimori, Nobuyuki; Kikuzawa, Nobuhiro; Yamauchi, Toshihiko

2004-01-01

The photocathode DC-gun with high average current, low beam emittance and long operational lifetime is considered to be indispensable for ERL-FEL. We have started the development program of a 200 keV electron gun with the NEA-GaAs photocathode for the first time in JAERI. In order to long an NEA surface lifetime, the JAERI 200 kV electron gun system consists of a 200 kV DC-gun chamber on extreme high vacuum condition and an NEA activation chamber with load-lock system. We report the goal of photocathode DC-gun R and D and the schedule of a developmental program. (author)

Single-side electron multipacting at the photocathode in rf guns

Directory of Open Access Journals (Sweden)

Jang-Hui Han

2008-01-01

Full Text Available Multiple electron impacting (multipacting can take place in rf fields when the rf components are composed of materials with a secondary electron yield greater than one. In rf gun cavities, multipacting may change the properties of the vacuum components or even damage them. First systematic measurements of the multipacting occurring in a photocathode rf gun were made at the Fermilab/NICADD Photoinjector Laboratory in 2000. The multipacting properties were found to depend on the cathode material and the solenoid field configuration. In this study, we measure the multipacting properties in more detail and model the secondary electron generation for numerical simulation. Measurements and simulations for the photoinjectors at Fermilab and DESY are compared. The multipacting takes place at the photocathode in rf guns and is categorized as single-side multipacting. In a low rf field, the electrons emitted from the cathode area do not leave the gun cavity within one rf cycle and have an opportunity to travel back and hit the cathode. The solenoid field distribution in the vicinity of the cathode changes the probability of electron bombardment of the cathode and makes a major contribution to the multipacting behavior.

Advanced laser technologies for high-brightness photocathode electron gun

International Nuclear Information System (INIS)

Tomizawa, Hiromitsu

2012-01-01

A laser-excited photocathode RF gun is one of the most reliable high-brightness electron beam sources for XFELs. Several 3D laser shaping methods have been developed as ideal photocathode illumination sources at SPring-8 since 2001. To suppress the emittance growth caused by nonlinear space-charge forces, the 3D cylindrical UV-pulse was optimized spatially as a flattop and temporally as squarely stacked chirped pulses. This shaping system is a serial combination of a deformable mirror that adaptively shapes the spatial profile with a genetic algorithm and a UV-pulse stacker that consists of four birefringent α-BBO crystal rods for temporal shaping. Using this 3D-shaped pulse, a normalized emittance of 1.4 πmm mrad was obtained in 2006. Utilizing laser's Z-polarization, Schottky-effect-gated photocathode gun was proposed in 2006. The cathode work functions are reduced by a laser-induced Schottky effect. As a result of focusing a radially polarized laser pulse with a hollow lens in vacuum, the Z-field (Z-polarization) is generated at the cathode. (author)

Advanced Laser Technologies for High-brightness Photocathode Electron Gun

Science.gov (United States)

Tomizawa, Hiromitsu

A laser-excited photocathode RF gun is one of the most reliable high-brightness electron beam sources for XFELs. Several 3D laser shaping methods have been developed as ideal photocathode illumination sources at SPring-8 since 2001. To suppress the emittance growth caused by nonlinear space-charge forces, the 3D cylindrical UV-pulse was optimized spatially as a flattop and temporally as squarely stacked chirped pulses. This shaping system is a serial combination of a deformable mirror that adaptively shapes the spatial profile with a genetic algorithm and a UV-pulse stacker that consists of four birefringent α-BBO crystal rods for temporal shaping. Using this 3D-shaped pulse, a normalized emittance of 1.4 π mm mrad was obtained in 2006. Utilizing laser's Z-polarization, Schottky-effect-gated photocathode gun was proposed in 2006. The cathode work functions are reduced by a laser-induced Schottky effect. As a result of focusing a radially polarized laser pulse with a hollow lens in vacuum, the Z-field (Z-polarization) is generated at the cathode.

High quantum efficiency photocathode simulation for the investigation of novel structured designs

Energy Technology Data Exchange (ETDEWEB)

Opachich, Y. P., E-mail: opachiyp@nv.doe.gov; Ross, P. W.; Huffman, E.; Koch, J. A. [National Security Technologies LLC, Livermore, California 94550 (United States); MacPhee, A. G.; Nagel, S. R.; Bell, P. M.; Bradley, D. K.; Landen, O. L. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Hilsabeck, T. J. [General Atomics, San Diego, California 92121 (United States)

2014-11-15

A computer model in CST Studio Suite has been developed to evaluate several novel geometrically enhanced photocathode designs. This work was aimed at identifying a structure that would increase the total electron yield by a factor of two or greater in the 1–30 keV range. The modeling software was used to simulate the electric field and generate particle tracking for several potential structures. The final photocathode structure has been tailored to meet a set of detector performance requirements, namely, a spatial resolution of <40 μm and a temporal spread of 1–10 ps. We present the details of the geometrically enhanced photocathode model and resulting static field and electron emission characteristics.

First operation of cesium telluride photocathodes in the TTF injector RF gun

CERN Document Server

Sertore, D; Flöttmann, K; Stephan, F; Zapfe, K; Michelato, P

2000-01-01

During the run 1998/1999 a new injector based on a laser-driven RF gun was brought in operation at the TESLA Test Facility (TTF) linac at DESY, in order to produce the beam structure and quality required either by TeV collider and SASE FEL experiments. High quantum efficiency cesium telluride photocathodes, prepared at Milano and transferred to DESY, have been successfully operated in the RF gun. A bunch charge of 50 nC, only limited by space charge effects, was achieved. The photocathodes have shown an operative lifetime of several months. A new cathode surface finishing has showed a promising decrease of the photocathode dark current. Measurements of dark current, quantum efficiency and lifetime are reported.

Review of sustainability indices and indicators: Towards a new City Sustainability Index (CSI)

Energy Technology Data Exchange (ETDEWEB)

Mori, Koichiro, E-mail: kmori@iis.u-tokyo.ac.jp [Institute of Industrial Science, University of Tokyo (Japan); Christodoulou, Aris, E-mail: aris.christodoulou@ucl.ac.uk [Centre for Transport Studies, University College London (United Kingdom)

2012-01-15

The purpose of this paper is to discuss conceptual requirements for a City Sustainability Index (CSI) and to review existing major sustainability indices/indicators in terms of the requirements. The following indices are reviewed: Ecological Footprint (EF), Environmental Sustainability Index (ESI), Dashboard of Sustainability (DS), Welfare Index, Genuine Progress Indicator (GPI), Index of Sustainable Economic Welfare, City Development Index, emergy/exergy, Human Development Index (HDI), Environmental Vulnerability Index (EVI), Environmental Policy Index (EPI), Living Planet Index (LPI), Environmentally-adjusted Domestic Product (EDP), Genuine Saving (GS), and some applications of composite indices or/and multivariate indicators to local or regional context as case studies. The key conceptual requirements for an adequate CSI are: (i) to consider environmental, economic and social aspects (the triple bottom line of sustainability) from the viewpoint of strong sustainability; (ii) to capture external impacts (leakage effects) of city on other areas beyond the city boundaries particularly in terms of environmental aspects; (iii) to create indices/indicators originally for the purpose of assessing city sustainability; and (iv) to be able to assess world cities in both developed and developing countries using common axes of evaluation. Based on the review, we conclude that it is necessary to create a new CSI that enables us to assess and compare cities' sustainability performance in order to understand the global impact of cities on the environment and human life as compared with their economic contribution. In the future, the CSI will be able to provide local authorities with guidance toward sustainable paths. - Highlights: Black-Right-Pointing-Pointer We derive the four key requirements for a new City Sustainability Index (CSI) system. Black-Right-Pointing-Pointer First, the triple bottom line must be considered in terms of strong sustainability. Black

Review of sustainability indices and indicators: Towards a new City Sustainability Index (CSI)

International Nuclear Information System (INIS)

Mori, Koichiro; Christodoulou, Aris

2012-01-01

The purpose of this paper is to discuss conceptual requirements for a City Sustainability Index (CSI) and to review existing major sustainability indices/indicators in terms of the requirements. The following indices are reviewed: Ecological Footprint (EF), Environmental Sustainability Index (ESI), Dashboard of Sustainability (DS), Welfare Index, Genuine Progress Indicator (GPI), Index of Sustainable Economic Welfare, City Development Index, emergy/exergy, Human Development Index (HDI), Environmental Vulnerability Index (EVI), Environmental Policy Index (EPI), Living Planet Index (LPI), Environmentally-adjusted Domestic Product (EDP), Genuine Saving (GS), and some applications of composite indices or/and multivariate indicators to local or regional context as case studies. The key conceptual requirements for an adequate CSI are: (i) to consider environmental, economic and social aspects (the triple bottom line of sustainability) from the viewpoint of strong sustainability; (ii) to capture external impacts (leakage effects) of city on other areas beyond the city boundaries particularly in terms of environmental aspects; (iii) to create indices/indicators originally for the purpose of assessing city sustainability; and (iv) to be able to assess world cities in both developed and developing countries using common axes of evaluation. Based on the review, we conclude that it is necessary to create a new CSI that enables us to assess and compare cities' sustainability performance in order to understand the global impact of cities on the environment and human life as compared with their economic contribution. In the future, the CSI will be able to provide local authorities with guidance toward sustainable paths. - Highlights: ► We derive the four key requirements for a new City Sustainability Index (CSI) system. ► First, the triple bottom line must be considered in terms of strong sustainability. ► Second, environmental leakage effects beyond city boundaries should

Pulsed laser deposition of yttrium photocathode suitable for use in radio-frequency guns

Science.gov (United States)

Lorusso, A.; Trovò, M.; Demidovich, A.; Cinquegrana, P.; Gontad, F.; Broitman, E.; Chiadroni, E.; Perrone, A.

2017-12-01

Yttrium (Y) thin film was grown by pulsed laser deposition (PLD) on a copper (Cu) polycrystalline substrate. Ex situ morphological and structural characterisations of the circular Y film of 1.2 µm thickness and 3 mm diameter have shown a very low droplet density on the film surface and a crystalline feature with a preferred orientation along the Y (100) plane. Moreover, Y thin film resulted in being very adherent to the Cu substrate and more scratch resistant than Cu bulk. A twin thin film was deposited also on a Cu backflange of a radio-frequency (RF) gun to test the suitability of the metallic thin film as photocathode. It was observed that the Y-coated photocathode was characterised by a quantum efficiency ( QE) higher than that of the Cu bulk photocathode even if the presence of space charge effects didn't allow deriving the absolute maximum value of QE of Y photocathode.

Perception-Induced Effects of Corporate Social Irresponsibility (CSiR) for Stereotypical and Admired Firms.

Science.gov (United States)

Voliotis, Seraphim; Vlachos, Pavlos A; Epitropaki, Olga

2016-01-01

How do stakeholders react to Corporate Social Irresponsibility (CSiR)? What are the emotional mechanisms and behavioral outcomes following CSiR perception? The psychology of CSR literature has yet to address these important questions and has largely considered CSR and CSiR as the opposite poles of the same continuum. In contrast, we view CSR and CSiR as distinct constructs and theorize about the cognitive (perceptual), emotional, and behavioral effects of CSiR activity on observers (i.e., primary and secondary stakeholders) building on theories of intergroup perception. Specifically, building on the Stereotype Content Model (SCM; Fiske et al., 2002) and the BIAS map (i.e., Behaviors from Intergroup Affect and Stereotypes; Cuddy et al., 2007)-which extends the SCM by predicting behavioral responses-we make predictions on potential stakeholder reactions to CSiR focusing on two practice-relevant cases: (a) a typical for-profit firm that engages in a CSiR activity, (b) an atypical admired firm that engages in CSiR activity.

Ultrathin MoS2-coated Ag@Si nanosphere arrays as an efficient and stable photocathode for solar-driven hydrogen production.

Science.gov (United States)

Zhou, Qingwei; Su, Shaoqiang; Hu, Die; Lin, Lin; Yan, Zhibo; Gao, Xingsen; Zhang, Zhang; Liu, Jun-Ming

2018-01-30

Solar-driven photoelectrochemical (PEC) water splitting has attracted a great deal of attention recently. Silicon (Si) is an ideal light absorber for solar energy conversion. However, the poor stability and inefficient surface catalysis of Si photocathodes for the hydrogen evolution reaction (HER) have remained key challenges. Alternatively, MoS 2 has been reported to exhibit excellent catalysis performance if sufficient active sites for the HER are available. Here, ultrathin MoS 2 nanoflakes are directly synthesized to coat arrays of Ag-core Si-shell nanospheres (Ag@Si NSs) by using chemical vapor deposition. Due to the high surface area ratio and large curvature of these NSs, the as-grown MoS 2 nanoflakes can accommodate more active sites. In addition, the high-quality coating of MoS 2 nanoflakes on the Ag@Si NSs protects the photocathode from damage during the PEC reaction. An photocurrent density of 33.3 mA cm -2 at a voltage of -0.4 V is obtained versus the reversible hydrogen electrode. The as-prepared nanostructure as a hydrogen photocathode is evidenced to have high stability over 12 h PEC performance. This work opens up opportunities for composite photocathodes with high activity and stability using cheap and stable co-catalysts.

Ultra-thin MoS2 coated Ag@Si nanosphere arrays as efficient and stable photocathode for solar-driven hydrogen production.

Science.gov (United States)

Zhou, Qingwei; Su, Shaoqiang; Hu, Die; Lin, Lin; Yan, Zhibo; Gao, Xingsen; Zhang, Zhang; Liu, Junming

2018-01-02

Solar-driven photoelectrochemical (PEC) water splitting has recently attracted much attention. Silicon (Si) is an ideal light absorber for solar energy conversion. However, the poor stability and inefficient surface catalysis of Si photocathode for hydrogen evolution reaction (HER) have been remained as the key challenges. Alternatively, MoS2 has been reported to exhibit the excellent catalysis performance if sufficient active sites for the HER are available. Here, ultra-thin MoS2 nanoflakes are directly synthesized to coat on the arrays of Ag-core Si-shell nanospheres (Ag@Si NSs) using the chemical vapor deposition (CVD). Due to the high surface area ratio and large curvature of these NSs, the as-grown MoS2 nanoflakes can accommodate more active sites. Meanwhile, the high-quality coating of MoS2 nanoflakes on the Ag@Si NSs protects the photocathode from damage during the PEC reaction. A high efficiency with a photocurrent of 33.3 mA cm-2 at a voltage of -0.4 V vs. the reversible hydrogen electrode is obtained. The as-prepared nanostructure as hydrogen photocathode is evidenced to have high stability over 12 hour PEC performance. This work opens opportunities for composite photocathode with high activity and stability using cheap and stable co-catalysts. © 2017 IOP Publishing Ltd.

Langley's CSI evolutionary model: Phase O

Science.gov (United States)

Belvin, W. Keith; Elliott, Kenny B.; Horta, Lucas G.; Bailey, Jim P.; Bruner, Anne M.; Sulla, Jeffrey L.; Won, John; Ugoletti, Roberto M.

1991-01-01

A testbed for the development of Controls Structures Interaction (CSI) technology to improve space science platform pointing is described. The evolutionary nature of the testbed will permit the study of global line-of-sight pointing in phases 0 and 1, whereas, multipayload pointing systems will be studied beginning with phase 2. The design, capabilities, and typical dynamic behavior of the phase 0 version of the CSI evolutionary model (CEM) is documented for investigator both internal and external to NASA. The model description includes line-of-sight pointing measurement, testbed structure, actuators, sensors, and real time computers, as well as finite element and state space models of major components.

High Brightness Injectors Based On Photocathode DC Gun

International Nuclear Information System (INIS)

B. Yunn

2001-01-01

Sample results of new injector design method based on a photocathode dc gun are presented, based on other work analytically proving the validity of the emittance compensation scheme for the case even when beam bunching is involved. We have designed several new injectors appropriate for different bunch charge ranges accordingly. Excellent beam quality produced by these injectors clearly shows that a photocathode dc gun can compete with a rf gun on an equal footing as the source of an electron beam for the bunch charge ranging up to 2 nano Coulomb (nC). This work therefore elevates a dc gun based injector to the preferred choice for many ongoing high brightness accelerator projects considering the proven operational stability and high average power capability of the dc gun

Preliminary Results from a Superconducting Photocathode Sample Cavity

CERN Document Server

Kneisel, Peter; Lipski, Andrzej; Sekutowicz, Jacek

2005-01-01

Pure niobium has been proposed as a photocathode material and recently a successful test has been conducted with a niobium single cell cavity to extract photo-currents from the surface of this cavity. However, the quantum efficiency of niobium is ~2·10-4, whereas electrodeposited lead has a ~15 times higher quantum efficiency. We have designed and tested a photo-injector niobium cavity, which can be used to insert photo-cathodes made of different materials in the high electric field region of the cavity. Experiments have been conducted with niobium and lead, which show that neither the Q- values of the cavity nor the obtainable surface fields are significantly lowered. This paper reports about the results from these tests.

First attempts to combine capillary tubes with photocathodes

CERN Document Server

Peskov, Vladimir; Sokolova, T; Radionov, I

1999-01-01

We describe our efforts to combine glass capillary plates, operating as a gas amplification structure at approx 1 atm, with photocathodes sensitive to visible light. Such capillary tubes are a by-product of the manufacture of Microchannel Plates and are commercially available. Preliminary tests indicate that gas gains >10 sup 3 could be achieved without photon feedback. With two capillary plates in tandem (double-step multiplication) overall gains up to 10 sup 5 were possible at counting rate <100 Hz/mm sup 2. This approach may open new possibilities for detection of visible photons by gaseous detectors. Potential advantages are: high gains, large sensitive area, high granularity, and insensitivity to magnetic fields.

Clinical application of 1H-chemical-shift imaging (CSI) to brain diseases

International Nuclear Information System (INIS)

Naruse, Shoji; Furuya, Seiichi; Ide, Mariko

1992-01-01

An H-1 chemical shift imaging (CSI) was developed as part of the clinical MRI system, by which magnetic resonance spectra (MRS) can be obtained from multiple small voxels and metabolite distribution in the brain can be visualized. The present study was to determine the feasibility and clinical potential of using an H-1 CSI. The device used was a Magnetom H 15 apparatus. The study population was comprised of 25 healthy subjects, 20 patients with brain tumor, 4 with ischemic disease, and 6 with miscellaneous degenerative disease. The H-1 CSI was obtained by the 3-dimensional Fourier transformation. After suppressing the lipid signal by the inversion-recovery method and the water signal by the chemical-shift selective pulse with a following dephasing gradient, 2-directional 16 x 16 phase encodings were applied to the 16 x 16∼18 x 18 cm field of view, in which a 8 x 8 x 2∼10 x 10 x 2 cm area was selected by the stimulated echo or spin-echo method. The metabolite mapping and its contour mapping were created by using the curve-fitted area, with interpolation to the 256 x 256 matrix. In the healthy group, high resolution spectra for N-acetyl aspartate (NAA), creatine, choline (Cho), and glutamine/glutamate were obtained from each voxel; and metabolite mapping and contour mapping also clearly showed metabolite distribution in the brain. In the group of brain tumor, an increased Cho and lactate and loss of NAA were observed, along with heterogeneity within the tumor and changes in the surrounding tissue; and there was a good correlation between lactate peak and tumor malignancy. The group of ischemic and degenerative disease had a decreased NAA and increased lactate on both spectra and metabolite mapping, depending on disease stage. These findings indicated that H-1 CSI is helpful for detecting spectra over the whole brain, as well as for determining metabolite distribution. (N.K.)

Characterization of diamond film and bare metal photocathodes as a function of temperature and surface preparation

Energy Technology Data Exchange (ETDEWEB)

Shurter, R P; Moir, D C; Devlin, D J [Los Alamos National Laboratory, Los Alamos, NM (United States)

1997-12-31

High current photocathodes using bare metal and polycrystalline diamond films illuminated by ultraviolet lasers are being developed at Los Alamos for use in a new generation of linear induction accelerators. These photocathodes must be able to produce multiple 60 ns pulses separated by several to tens of nanoseconds. The vacuum environment in which the photocathodes must operate is {sup 1}0-5 torr. (author). 9 figs., 10 refs.

Effect of Sb thickness on the performance of bialkali-antimonide photocathodes

Energy Technology Data Exchange (ETDEWEB)

Mamun, Md Abdullah A., E-mail: mmamu001@odu.edu; Elmustafa, Abdelmageed A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529 and The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Hernandez-Garcia, Carlos; Mammei, Russell; Poelker, Matthew [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

2016-03-15

The alkali species Cs and K were codeposited using an effusion source, onto relatively thick layers of Sb (50 nm to ∼7 μm) grown on GaAs and Ta substrates inside a vacuum chamber that was baked and not-vented, and also baked and vented with clean dry nitrogen but not rebaked. The characteristics of the Sb films, including sticking probability, surface roughness, grain size, and crystal properties were very different for these conditions, yet comparable values of photocathode yield [or quantum efficiency (QE)] at 284 V were obtained following codeposition of the alkali materials. Photocathodes manufactured with comparatively thick Sb layers exhibited the highest QE and the best 1/e lifetime. The authors speculate that the alkali codeposition enabled optimized stoichiometry for photocathodes manufactured using thick Sb layers, which could serve as a reservoir for the alkali materials.

Study of silicon tip photocathodes in DC and RF photo-injectors

International Nuclear Information System (INIS)

Jaber, Zakaria

1999-01-01

Nowadays the electron beams with a high intensity are particularly interesting in research and the applied physics. Producing such beams for which high intensity and low emittance are synonyms with efficiency, means developing new high luminosity electron sources, i.e. the photocathodes. This thesis, essentially experimental, is oriented in this way. After an introduction of Clermont-Ferrand and the LAL of Orsay experimental apparatus where the experiments took place, the chapter one presents the field emission and the photo-field emission. Then, we prove that the quantum efficiency of the photocathodes with silicon tips is higher for wavelengths near 800 nm. This fact is essential because it allows the use of lasers in the fundamental wavelength - Titan-Saphir for instance. In the chapter 2, we remind how the silicon tips are realized and how to improve surface conditions. Procedures and the surface analysis with the SEM and XPS are described. With a Nd-Yag laser, pumped with laser diode setting up with the participation of IRCOM Opticians of Limoges, the photocathode supplied 1 Ampere per pulse at a quantum efficiency of 0.25%. The description of this experiment and the results are the object of the chapter 3. The space charge outside the photocathode space prevents the electrons to go through. The Child-Langmuir formula limits the current with the DC gun at about 30 Ampere. To improve this result we have to use a photo-injector. In chapter 4 we prove that the silicon tip photocathode are compatible with RF gun requirements by PRIAM modeling and low level measure in a cold model of CANDELA RF gun. Technical department of CERN helped us to prepare this very sensitive experiment. (author)

ATDM LANL FleCSI: Topology and Execution Framework

Energy Technology Data Exchange (ETDEWEB)

Bergen, Benjamin Karl [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-11-06

FleCSI is a compile-time configurable C++ framework designed to support multi-physics application development. As such, FleCSI attempts to provide a very general set of infrastructure design patterns that can be specialized and extended to suit the needs of a broad variety of solver and data requirements. This means that FleCSI is potentially useful to many different ECP projects. Current support includes multidimensional mesh topology, mesh geometry, and mesh adjacency information, n-dimensional hashed-tree data structures, graph partitioning interfaces, and dependency closures (to identify data dependencies between distributed-memory address spaces). FleCSI introduces a functional programming model with control, execution, and data abstractions that are consistent with state-of-the-art task-based runtimes such as Legion and Charm++. The model also provides support for fine-grained, data-parallel execution with backend support for runtimes such as OpenMP and C++17. The FleCSI abstraction layer provides the developer with insulation from the underlying runtimes, while allowing support for multiple runtime systems, including conventional models like asynchronous MPI. The intent is to give developers a concrete set of user-friendly programming tools that can be used now, while allowing flexibility in choosing runtime implementations and optimizations that can be applied to architectures and runtimes that arise in the future. This project is essential to the ECP Ristra Next-Generation Code project, part of ASC ATDM, because it provides a hierarchically parallel programming model that is consistent with the design of modern system architectures, but which allows for the straightforward expression of algorithmic parallelism in a portably performant manner.

A pulsed electron injector using a metal photocathode irradiated by an excimer laser

International Nuclear Information System (INIS)

Kauppila, T.J.; Builta, L.A.; Crutcher, J.K.; Elliott, J.C.; Moir, D.C.

1987-01-01

The hot cathode of an electron gun is replaced by a metallic photocathode driven by an excimer laser. The current, current density, and emittance of the 500-kV electron beam produced by the photoelectron source are presented. In addition, the temperature of the photocathode is varied to study the possibility of a hybrid source

Engineering MoSx/Ti/InP Hybrid Photocathode for Improved Solar Hydrogen Production.

Science.gov (United States)

Li, Qiang; Zheng, Maojun; Zhong, Miao; Ma, Liguo; Wang, Faze; Ma, Li; Shen, Wenzhong

2016-07-19

Due to its direct band gap of ~1.35 eV, appropriate energy band-edge positions, and low surface-recombination velocity, p-type InP has attracted considerable attention as a promising photocathode material for solar hydrogen generation. However, challenges remain with p-type InP for achieving high and stable photoelectrochemical (PEC) performances. Here, we demonstrate that surface modifications of InP photocathodes with Ti thin layers and amorphous MoSx nanoparticles can remarkably improve their PEC performances. A high photocurrent density with an improved PEC onset potential is obtained. Electrochemical impedance analyses reveal that the largely improved PEC performance of MoSx/Ti/InP is attributed to the reduced charge-transfer resistance and the increased band bending at the MoSx/Ti/InP/electrolyte interface. In addition, the MoSx/Ti/InP photocathodes function stably for PEC water reduction under continuous light illumination over 2 h. Our study demonstrates an effective approach to develop high-PEC-performance InP photocathodes towards stable solar hydrogen production.

CsI Calorimeter for a Compton-Pair Telescope

Science.gov (United States)

Grove, Eric J.

We propose to build and test a hodoscopic CsI(Tl) scintillating-crystal calorimeter for a medium-energy γ-ray Compton and pair telescope. The design and technical approach for this calorimeter relies deeply on heritage from the Fermi LAT CsI Calorimeter, but it dramatically improves the low-energy performance of that design by reading out the scintillation light with silicon photomultipliers (SiPMs), making the technology developed for Fermi applicable in the Compton regime. While such a hodoscopic calorimeter is useful for an entire class of medium-energy γ-ray telescope designs, we propose to build it explicitly to support beam tests and balloon flight of the Proto-ComPair telescope, the development and construction of which was funded in a four-year APRA program beginning in 2015 ("ComPair: Steps to a Medium Energy γ-ray Mission" with PI J. McEnery of GSFC). That award did not include funding for its CsI calorimeter subsystem, and this proposal is intended to cover that gap. ComPair is a MIDEX-class instrument concept to perform a high-sensitivity survey of the γ-ray sky from 0.5 MeV to 500 MeV. ComPair is designed to provide a dramatic increase in sensitivity relative to previous instruments in this energy range (predominantly INTEGRAL/SPI and Compton COMPTEL), with the same transformative sensitivity increase - and corresponding scientific return- that the Fermi Large Area Telescope provided relative to Compton EGRET. To enable transformative science over a broad range of MeV energies and with a wide field of view, ComPair is a combined Compton telescope and pair telescope employing a silicon-strip tracker (for Compton scattering and pair conversion and tracking) and a solid-state CdZnTe calorimeter (for Compton absorption) and CsI calorimeter (for pair calorimetry), surrounded by a plastic scintillator anti-coincidence detector. Under the current proposal, we will complete the detailed design, assembly, and test of the CsI calorimeter for the risk

Graphene-based copper oxide thin film nanostructures as high-efficiency photocathode for p-type dye-sensitized solar cells

Science.gov (United States)

Kilic, Bayram; Turkdogan, Sunay; Astam, Aykut; Baran, Sümeyra Seniha; Asgin, Mansur; Cebeci, Hulya; Urk, Deniz

2017-10-01

Graphene-based p-type dye-sensitized solar cells (p-DSSCs) have been proposed and fabricated using copper oxide urchin-like nanostructures (COUN) as photocathode with an FeS2 counter electrode (CE). COUN composed of Cu2O core sphere and CuO shell nanorods with overall diameters of 2 to 4 μm were grown by a simple hydrothermal method with self-assemble nucleation. It was figured out that the formation of copper oxide core/shell structures could be adjusted by an ammonia additive leading to pH change of the precursor solution. In addition to a photocathode, we also demonstrated FeS2 thin films as an efficient CE material alternative to the conventional Pt CEs in DSSCs. FeS2 nanostructures, with diameters of 50 to 80 nm, were synthesized by a similar hydrothermal approach. FeS2 nanostructures are demonstrated to be an outstanding CE material in p-DSSCs. We report graphene/COUN as photocathode and Pt/FeS2 as CE in p-DSSCs, and results show that the synergetic combination of electrodes in each side (increased interconnectivity between COUN and graphene layer, high surface area, and high catalytic activity of FeS2) increased the power conversion efficiency from 1.56% to 3.14%. The excellent performances of COUN and FeS2 thin film in working and CEs, respectively, make them unique choices among the various photocathode and CE materials studied.

A DFT study on NEA GaN photocathode with an ultrathin n-type Si-doped GaN cap layer

Science.gov (United States)

Xia, Sihao; Liu, Lei; Kong, Yike; Diao, Yu

2016-10-01

Due to the drawbacks of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, a new-type NEA GaN photocathodes with heterojunction surface dispense with Cs activation are proposed. This structure can be obtained through the coverage of an ultrathin n-type Si-doped GaN cap layer on the p-type Mg-doped GaN emission layer. The influences of the cap layer on the photocathode are calculated using DFT. This study indicates that the n-type cap layer can promote the photoemission characteristics of GaN photocathode and demonstrates the probability of the preparation of a NEA GaN photocathode with an n-type cap layer.

Photocathodes in accelerator applications

International Nuclear Information System (INIS)

Fraser, J.S.; Sheffield, R.L.; Gray, E.R.; Giles, P.M.; Springer, R.W.; Loebs, V.A.

1987-01-01

Some electron accelerator applications require bursts of short pulses at high microscopic repetition rates and high peak brightness. A photocathode, illuminated by a mode-locked laser, is well suited to filling this need. The intrinsic brightness of a photoemitter beam is high; experiments are under way at Los Alamos to study the brightness of short bunches with high space charge after acceleration. A laser-illuminated Cs 3 Sb photoemitter is located in the first rf cavity of an injector linac. Diagnostics include a pepper-pot emittance analyzer, a magnetic spectrometer, and a streak camera

Status of COMPASS RICH-1 Upgrade with MPGD-based Photon Detectors

Directory of Open Access Journals (Sweden)

Alexeev M.

2018-01-01

Full Text Available A Set of new MPGD-based Photon Detectors is being built for the upgrade of COMPASS RICH-1. The detectors cover a total active area of 1.4 m2 and are based on a hybrid architecture consisting of two THGEM layers and a Micromegas. A CsI film on one THGEM acts as a reflective photocathode. The characteristics of the detector, the production of the components and their validation tests are described in detail.

Methanol sensor for integration with GaP nanowire photocathode

Science.gov (United States)

Novák, J.; Laurenčíková, A.; Hasenohrl, S.; Eliáš, P.; Kováč, J.

2017-05-01

We proposed a new type of the methanol concentration sensor that may be integrated directly to the GaP nanostructured photocathode. Necessary attribute for this design is the possibility to make it compatible with p-type of semiconductor. This condition follows from the fact that photocathodes for the CO2 splitting are exclusively prepared from p-type of semiconductors. Design of methanol sensor emanates from this principle. On the GaP substrate is deposited thin Pt supporting layer (100-200 nm thick).This layer is covered by 500 nm thick Nafion membrane that serves as proton filter. On the top of Nafion layer is deposited top Pt contact layer covered by thin nanostructured Pt layer layer with various thickness (0.5 -5 nm). This nanostructured Pt is formed into small islands. It serves as an absorption layer for methanol. Sensor detection properties were estimated from monitoring of I-V characteristics. They were measured in dark and under various methanol concentrations. Dark current values are in order 10-9 A, and this current increases up to order of microamps for methanol of concentration more than 95%.These measurements proved high sensitivity of the GaP compatible sensor structure. Methanol sensors were realized in form of narrow stripe on the side of the photocathode.

Dark Current and Multipacting in the Photocathode RF Guns at PITZ

CERN Document Server

Hui-Han, Jang; Flöttmann, Klaus; Grabosch, H J; Hartrott, Michael; Krasilnikov, Mikhail; Michelato, Paolo; Miltchev, Velizar; Monaco, Laura; Oppelt, Anne; Petrosyan, Bagrat; Riemann, S; Roensch, Juliane; Schreiber, Siegfried; Sertore, Daniele; Staykov, Lazar; Stephan, Frank

2005-01-01

For photocathode rf guns, the amount of dark current depends on the cavity surface and the photocathodes. Smooth conditioning reduces the amount of dark current. Mechanical damages of the cathodes induce high dark current and chemical pollution changes emission properties of the cathode. Multipacting in the gun cavity changes the surface status of the cathodes and sometimes makes the gun operation impossible due to vacuum interlocks. In this paper, dark current and multipacting features of the rf gun are presented including experimental and simulation studies.

Characterization of a superconducting Pb photocathode in a superconducting rf photoinjector cavity

CERN Document Server

Barday, R; Jankowiak, A; Kamps, T; Knobloch, J; Kugeler, O; Matveenko, A; Neumann, A; Schmeißer, M; Volker, J; Kneisel, P; Nietubyc, R; Schubert S; Smedley J; Sekutowicz, J; Will, I

2014-01-01

Photocathodes are a limiting factor for the next generation of ultrahigh brightness photoinjectors. We studied the behavior of a superconducting Pb cathode in the cryogenic environment of a superconducting rf gun cavity to measure the quantum efficiency, its spatial distribution, and the work function. We will also discuss how the cathode surface contaminants modify the performance of the photocathode as well as the gun cavity and we discuss the possibilities to remove these contaminants.

The adsorption of Sr(II) and Cs(I) ions by irradiated Saccharomyces cerevisiae

International Nuclear Information System (INIS)

Yiming Tan; Jundong Feng; Liang Qiu; Zhentian Zhao; Xiaohong Zhang; Haiqian Zhang

2017-01-01

Adsorption behavior and mechanism of Sr(II) and Cs(I) in single and binary solutions using irradiated Saccharomyces cerevisiae was investigated. The effects of several environmental factors on Sr(II) and Cs(I) adsorption to irradiated Saccharomyces cerevisiae was determined. The equilibrium experimental data were simulated by different kinetic models and isotherm models. The combined effect of Sr(II) and Cs(I) on Saccharomyces cerevisiae is generally antagonistic. SEM and EDS analyses indicate that crystals formed on the cell surface are precipitate of Sr(II) and Cs(I), respectively. (author)

Spectral response variation of a negative-electron-affinity photocathode in the preparation process

International Nuclear Information System (INIS)

Liu Lei; Du Yujie; Chang Benkang; Yunsheng Qian

2006-01-01

In order to research the spectral response variation of a negative electron affinity (NEA) photocathode in the preparation process, we have done two experiments on a transmission-type GaAs photocathode.First, an automatic spectral response recording system is described, which is used to take spectral response curves during the activation procedure of the photocathode. By this system, the spectral response curves of a GaAs:Cs-Ophotocathode measured in situ are presented. Then, after the cathode is sealed with a microchannel plate and a fluorescence screen into the image tube, we measure the spectral response of the tube by another measurement instrument. By way of comparing and analyzing these curves, we can find the typical variation in spectral-responses.The reasons for the variation are discussed. Based on these curves, spectral matching factors of a GaAs cathode for green vegetation and rough concrete are calculated. The visual ranges of night-vision goggles under specific circumstances are estimated. The results show that the spectral response of the NEA photocathode degraded in the sealing process, especially at long wavelengths. The variation has also influenced the whole performance of the intensifier tube

CsI calorimeter of the CMD-3 detector

International Nuclear Information System (INIS)

Aulchenko, V.M.; Bondar, A.E.; Erofeev, A.L.; Kovalenko, O.A.; Kozyrev, A.N.; Kuzmin, A.S.; Logashenko, I.B.; Razuvaev, G.P.; Ruban, A.A.; Shebalin, V.E.; Shwartz, B.A.; Talyshev, A.A.; Titov, V.M.; Yudin, Yu.V.; Epifanov, D.A.

2015-01-01

The VEPP-2000 e + e − collider has been operated at Budker Institute of Nuclear Physics since 2010. The experiments are performed with two detectors CMD-3 and SND. The calorimetry at the CMD-3 detector is based on three subsystems, two coaxial barrel calorimeters—Liquid Xenon Calorimeter and crystal CsI calorimeter, and endcap calorimeter with BGO crystals. This paper describes the CsI calorimeter of the CMD-3 detector. The calorimeter design, its electronics and calibration procedures are discussed

Effects of Surface Nonuniformities on the Mean Transverse Energy from Photocathodes

Science.gov (United States)

Karkare, Siddharth; Bazarov, Ivan

2015-08-01

The performance of photoinjectors is limited by the lowest value of the mean transverse energy of the electrons obtained from photocathodes. The factors that influence the mean transverse energy are poorly understood. In this paper, we develop models to calculate the effect of spatial work-function variations and subnanometer-scale roughness and surface defects on the mean transverse energy. We show that these can limit the lowest value of mean transverse energy achieved and that atomically perfect surfaces will be required to further reduce the mean transverse energy obtained from photocathodes.

Nonepitaxial Thin-Film InP for Scalable and Efficient Photocathodes.

Science.gov (United States)

Hettick, Mark; Zheng, Maxwell; Lin, Yongjing; Sutter-Fella, Carolin M; Ager, Joel W; Javey, Ali

2015-06-18

To date, some of the highest performance photocathodes of a photoelectrochemical (PEC) cell have been shown with single-crystalline p-type InP wafers, exhibiting half-cell solar-to-hydrogen conversion efficiencies of over 14%. However, the high cost of single-crystalline InP wafers may present a challenge for future large-scale industrial deployment. Analogous to solar cells, a thin-film approach could address the cost challenges by utilizing the benefits of the InP material while decreasing the use of expensive materials and processes. Here, we demonstrate this approach, using the newly developed thin-film vapor-liquid-solid (TF-VLS) nonepitaxial growth method combined with an atomic-layer deposition protection process to create thin-film InP photocathodes with large grain size and high performance, in the first reported solar device configuration generated by materials grown with this technique. Current-voltage measurements show a photocurrent (29.4 mA/cm(2)) and onset potential (630 mV) approaching single-crystalline wafers and an overall power conversion efficiency of 11.6%, making TF-VLS InP a promising photocathode for scalable and efficient solar hydrogen generation.

On Line Stator Resistance Tuning of DTC Control CSI Fed IM Drives

OpenAIRE

PANNEER SELVAM

2012-01-01

Current source inverter (CSI) fed drives are employed in high power applications. The conventional CSI drives suffer from drawbacks such as harmonic resonance, unstable operation at low speed ranges, and torque pulsation. CSI fed drives with Direct Torque Control (DTC) has drawn the attention of the motor drives designers because its implementation requires no position sensor. Crucial to the success of this scheme is the estimation of electromagnetic torque and stator flux linkages using the ...

Electrostatic X-ray image recording device with mesh-base photocathode photoelectron discriminator means

International Nuclear Information System (INIS)

1977-01-01

An electrostatic X-ray image recording device having a pair of spaced electrodes with a gas-filled gap therebetween, and including discrimination means, having a conductive mesh supporting a photocathodic material, positioned in the gas-filled gap between a first electrode having a layer of ultraviolet-emitting fluorescent material and a second electrode having a plastic sheet adjacent thereto for receiving photoelectrons emitted by the photocathodic material and accelerated to the second electrode by an applied field. The photoconductor-mesh element discriminates against fast electrons, produced by direct impingement of X-rays upon the photocathode to substantially reduce secondary electron production and amplification, thereby increasing both the signal-to-noise and contrast ratios. The electrostatic image formed on the plastic sheet is developed by zerographic techniques after exposure. (Auth.)

Quantum efficiency and thermal emittance of metal photocathodes

Directory of Open Access Journals (Sweden)

David H. Dowell

2009-07-01

Full Text Available Modern electron beams have demonstrated the brilliance needed to drive free electron lasers at x-ray wavelengths with major advances occurring since the invention of the photocathode gun and the realization of emittance compensation. These state-of-the-art electron beams are now becoming limited by the intrinsic thermal emittance of the cathode. In both dc and rf photocathode guns details of the cathode emission physics strongly influence the quantum efficiency and the thermal emittance. Therefore improving cathode performance is essential to increasing the brightness of beams. It is especially important to understand the fundamentals of cathode quantum efficiency and thermal emittance. This paper investigates the relationship between the quantum efficiency and the thermal emittance for metal cathodes using the Fermi-Dirac model for the electron distribution. We use a consistent theory to derive the quantum efficiency and thermal emittance, and compare our results to those of others.

Enhanced quantum efficiency for CsI grown on a graphite-based substrate coating

CERN Document Server

Friese, J; Homolka, J; Kastenmüller, A; Maier-Komor, P; Peter, M; Zeitelhack, K; Kienle, P; Körner, H J

1999-01-01

Quantum efficiencies (QE) in the vacuum ultraviolet (VUV) wavelength region have been measured for solid CsI layers on various substrates. The CsI films were deposited applying electron beam evaporation. The QE measurements were performed utilizing synchrotron radiation as well as light from a deuterium lamp. A GaAsP diode with a sensitivity calibration traceable to a primary radiation standard was used for normalization. For CsI layers grown on resin-stabilized graphite films a significant enhancement of QE was observed. Substrates suitable for gas detector applications and aging properties were investigated. The procedures to prepare and reproduce high quantum efficient CsI layers are described.

Sources of Emittance in RF Photocathode Injectors

Energy Technology Data Exchange (ETDEWEB)

Dowell, David [SLAC National Accelerator Lab., Menlo Park, CA (United States)

2016-12-11

Advances in electron beam technology have been central to creating the current generation of x-ray free electron lasers and ultra-fast electron microscopes. These once exotic devices have become essential tools for basic research and applied science. One important beam technology for both is the electron source which, for many of these instruments, is the photocathode RF gun. The invention of the photocathode gun and the concepts of emittance compensation and beam matching in the presence of space charge and RF forces have made these high-quality beams possible. Achieving even brighter beams requires a taking a finer resolution view of the electron dynamics near the cathode during photoemission and the initial acceleration of the beam. In addition, the high brightness beam is more sensitive to degradation by the optical aberrations of the gun’s RF and magnetic lenses. This paper discusses these topics including the beam properties due to fundamental photoemission physics, space charge effects close to the cathode, and optical distortions introduced by the RF and solenoid fields. Analytic relations for these phenomena are derived and compared with numerical simulations.

The Status of GLAST CsI Calorimeter

Energy Technology Data Exchange (ETDEWEB)

Chekhtman, A.

2003-09-18

GLAST is a gamma-ray observatory for celestial sources in the energy range from 20 MeV to 300 GeV. This is NASA project with launch anticipated in 2006. The principal instrument of the GLAST mission is the Large Area Telescope (LAT), consisting of an Anti Coincidence Detector (ACD), a silicon-strip detector Tracker (TKR) and a hodoscopic CsI Calorimeter (CAL). It consists of 16 identical modules arranged in a 4 x 4 array. Each module has horizontal dimensions 38 x 38 cm{sup 2} and active thickness 8.5 radiation length. It contains 96 CsI (Tl) crystals arranged in 8 layers with 12 crystals per layer. The scintillation light is measured by PIN photodiodes mounted on both ends of each crystal. The sum of signals at the two ends of the crystal provides the energy measurement. The difference in these signals provides the position measurement along the crystal. The calorimeter was designed to meet the goals of good energy resolution (better than 10% for photon energies 100 MeV-100 GeV), position resolution of {approx} 1 mm for photon energies > 1 GeV, and a rejection factor of > 100 for charged cosmic rays, under limitations on calorimeter weight (95 kg per module) and power consumption (6 W per module). The Monte Carlo simulation and prototype beam test results confirm that proposed design meets the requirements. Calorimeter production is planned to start in 2003.

Femtosecond response time measurements of a Cs2Te photocathode

Science.gov (United States)

Aryshev, A.; Shevelev, M.; Honda, Y.; Terunuma, N.; Urakawa, J.

2017-07-01

Success in design and construction of a compact, high-brightness accelerator system is strongly related to the production of ultra-short electron beams. Recently, the approach to generate short electron bunches or pre-bunched beams in RF guns directly illuminating a high quantum efficiency semiconductor photocathode with femtosecond laser pulses has become attractive. The measurements of the photocathode response time in this case are essential. With an approach of the interferometer-type pulse splitter deep integration into a commercial Ti:Sa laser system used for RF guns, it has become possible to generate pre-bunched electron beams and obtain continuously variable electron bunch separation. In combination with a well-known zero-phasing technique, it allows us to estimate the response time of the most commonly used Cs2Te photocathode. It was demonstrated that the peak-to-peak rms time response of Cs2Te is of the order of 370 fs, and thereby, it is possible to generate and control a THz sequence of relativistic electron bunches by a conventional S-band RF gun. This result can also be applied for investigation of other cathode materials and electron beam temporal shaping and further opens a possibility to construct wide-range tunable, table-top THz free electron laser.

DC photogun vacuum characterization through photocathode lifetime studies

International Nuclear Information System (INIS)

Marcy Stutzman; Joseph Grames; Matt Poelker; Kenneth Surles-Law; Philip Adderley

2007-01-01

Excellent vacuum is essential for long photocathode lifetimes in DC high voltage photoelectron guns. Vacuum Research at Thomas Jefferson National Accelerator Facility has focused on characterizing the existing vacuum systems at the CEBAF polarized photoinjector and on quantifying improvements for new systems. Vacuum chamber preprocessing, full activation of NEG pumps and NEG coating the chamber walls should improve the vacuum within the electron gun, however, pressure measurement is difficult at pressures approaching the extreme-high-vacuum (XHV) region and extractor gauge readings are not significantly different between the improved and original systems. The ultimate test of vacuum in a DC high voltage photogun is the photocathode lifetime, which is limited by the ionization and back-bombardment of residual gasses. Discussion will include our new load-locked gun design as well as lifetime measurements in both our operational and new photo-guns, and the correlations between measured vacuum and lifetimes will be investigated

Double-layered NiO photocathodes for p-type DSSCs with record IPCE

Energy Technology Data Exchange (ETDEWEB)

Li, Lin; Qin, Peng; Gorlov, Mikhail [Center of Molecular Devices School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm (Sweden); Gibson, Elizabeth A.; Boschloo, Gerrit [Department of Physical and Analytical Chemistry, Uppsala University (Sweden); Hagfeldt, Anders [Center of Molecular Devices School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm (Sweden); Department of Physical and Analytical Chemistry, Uppsala University (Sweden); DUT-KTH Joint Education and Research Center of Molecular Devices, State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT), Dalian (China); Sun, Licheng [Center of Molecular Devices School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm (Sweden); DUT-KTH Joint Education and Research Center of Molecular Devices, State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT), Dalian (China)

2010-04-18

A way to achieve a high-efficiency dye-sensitized solar cell is to combine an n-type TiO{sub 2}-based photoanode with a p-type photocathode in a tandem configuration. The development of an efficient photocathode is, at present, the key target. We have optimized the NiO, I{sub 3}{sup -}/I{sup -} p-DSSC system to obtain record photocurrent, giving 64% incident photon-to-current conversion efficiency (IPCE) and 5.48 mAcm{sup -2} J{sub SC}. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Automated installation for several photomultiplier photocathode activation by means of one vacuum facility

International Nuclear Information System (INIS)

Beschastnov, P.M.; Peryshkin, A.I.; Pyata, E.Eh.; Usov, Yu.V.

1989-01-01

An automated installation for simultaneous activation of up to four photocathodes of several photomultipliers by means of one vacuum station with the common furnace is described. Production technology of producing multialkaline photocathode makes up the basis for creating automated technology. The installation is produced on the base of the R110B industrial station and the Electronica-60 microcomputer. Software written in FORTRAN providing for control over all process stages is developed. 6 refs.; 2 figs

The Quantum Efficiency and Thermal Emittance of Metal Photocathodes

International Nuclear Information System (INIS)

Dowell, D.

2009-01-01

Modern electron beams have demonstrated the brilliance needed to drive free electron lasers at x-ray wavelengths, with the principle improvements occurring since the invention of the photocathode gun. The state-of-the-art normalized emittance electron beams are now becoming limited by the thermal emittance of the cathode. In both DC and RF photocathode guns, details of the cathode emission physics strongly influence the quantum efficiency and the thermal emittance. Therefore improving cathode performance is essential to increasing the brightness of beams. It is especially important to understand the fundamentals of cathode quantum efficiency and thermal emittance. This paper investigates the relationship between the quantum efficiency and the thermal emittance of metal cathodes using the Fermi-Dirac model for the electron distribution. We derive the thermal emittance and its relationship to the quantum efficiency, and compare our results to those of others

Technology to Establish a Factory for High QE Alkali Antimonide Photocathodes

Energy Technology Data Exchange (ETDEWEB)

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

2015-11-16

Intense electron beams are key to a large number of scientific endeavors, including electron cooling of hadron beams, electron-positron colliders, secondary-particle beams such as photons and positrons, sub-picosecond ultrafast electron diffraction (UED), and new high gradient accelerators that use electron-driven plasmas. The last decade has seen a considerable interest in pursuit and realization of novel light sources such as Free Electron Lasers [1] and Energy Recovery Linacs [2] that promise to deliver unprecedented quality x-ray beams. Many applications for high-intensity electron beams have arisen in recent years in high-energy physics, nuclear physics and energy sciences, such as recent designs for an electron-hadron collider at CERN (LHeC) [3], and beam coolers for hadron beams at LHC and eRHIC [4,5]. Photoinjectors are used at the majority of high-brightness electron linacs today, due to their efficiency, timing structure flexibility and ability to produce high power, high brightness beams. The performance of light source machines is strongly related to the brightness of the electron beam used for generating the x-rays. The brightness of the electron beam itself is mainly limited by the physical processes by which electrons are generated. For laser based photoemission sources this limit is ultimately related to the properties of photocathodes [6]. Most facilities are required to expend significant manpower and money to achieve a workable, albeit often non-ideal, compromise photocathode solution. If entirely fabricated in-house, the photocathode growth process itself is laborious and not always reproducible: it involves the human element while requiring close adherence to recipes and extremely strict control of deposition parameters. Lack of growth reliability and as a consequence, slow adoption of viable photoemitter types, can be partly attributed to the absence of any centralized facility or commercial entity to routinely provide high peak current

Tuning the colors of c-Si solar cells by exploiting plasmonic effects

Science.gov (United States)

Peharz, G.; Grosschädl, B.; Prietl, C.; Waldhauser, W.; Wenzl, F. P.

2016-09-01

The color of a crystalline silicon (c-Si) solar cell is mainly determined by its anti-reflective coating. This is a lambda/4 coating made from a transparent dielectric material. The thickness of the anti-reflective coating is optimized for maximal photocurrent generation, resulting in the typical blue or black colors of c-Si solar cells. However, for building-integrated photovoltaic (BiPV) applications the color of the solar cells is demanded to be tunable - ideally by a cheap and flexible coating process on standard (low cost) c-Si solar cells. Such a coating can be realized by applying plasmonic coloring which is a rapidly growing technology for high-quality color filtering and rendering for different fields of application (displays, imaging,…). In this contribution, we present results of an approach for tuning the color of standard industrial c-Si solar cells that is based on coating them with metallic nano-particles. In particular, thin films (green and brownish/red. The position of the resonance peak in the reflection spectrum was found to be almost independent from the angle of incidence. This low angular sensitivity is a clear advantage compared to alternative color tuning methods, for which additional dielectric thin films are deposited on c-Si solar cells.

Highly stable copper oxide composite as an effective photocathode for water splitting via a facile electrochemical synthesis strategy

KAUST Repository

Zhang, Zhonghai; Wang, Peng

2012-01-01

focused on n-type metal oxide semiconductors as photoanodes, whereas studies of p-type metal oxide semiconductors as photocathodes where hydrogen is generated are scarce. In this paper, highly efficient and stable copper oxide composite photocathode

The development of gaseous detectors with solid photocathodes for low temperature applications

CERN Document Server

Periale, L.; Iacobaeus, C.; Francke, T.; Lund-Jensen, B.; Pavlopoulos, N.; Picchi, P.; Pietropaolo, F.

2004-01-01

There are several applications and fundamental research areas which require the detection of VUV light at cryogenic temperatures. For these applications we have developed and successfully tested special designs of gaseous detectors with solid photocathodes able to operate at low temperatures: sealed gaseous detectors with MgF2 windows and windowless detectors. We have experimentally demonstrated, that both primary and secondary (due to the avalanche multiplication inside liquids) scintillation lights could be recorded by photosensitive gaseous detectors. The results of this work may allow one to significantly improve the operation of some noble liquid gas TPCs.

An in-situ photocathode loading system for the SLC Polarized Electron Gun

International Nuclear Information System (INIS)

Kirby, R.E.; Collet, G.J.; Skarpaas, K.

1992-12-01

An ultra-high vacuum loadlock system capable of operating at high voltage has been added to the SLC Polarized Electron Gun. The unit incorporates facilities for heat cleaning, activating and measuring the quantum efficiency of photocathodes. A tray of up to four photocathodes can be exchanged without bringing the activation unit or gun up to atmosphere. Low voltage quantum efficiencies of 20% have been obtained for bulk GaAs at 633 nm and 6% for a 0.3 micron GaAs layer at 755 nm. Results for other cathodes as well as operational characteristics are discussed

Polarized Light Sources for photocathode electron guns at SLAC

International Nuclear Information System (INIS)

Woods, M.; Frisch, J.; Witte, K.; Zolotorev, M.

1992-12-01

We describe current and future Polarized Light Sources at SLAC for use with photocathode electron guns to produce polarized electron beams. The SLAC experiments SLD and E142 are considered, and are used to define the required parameters for the Polarized Light Sources

Decay-time measurements on 'pure' CsI scintillators prepared by different methods

International Nuclear Information System (INIS)

Keszthelyi-Landori, S.; Foeldvari, I.; Voszka, R.; Fodor, Z.; Seres, Z.

1990-05-01

The discovery of the fast decay time of the pure CsI and the various results of the measured samples led to the investigation of decay time of CsI crystals prepared by different methods. Carefully grown or prepared pure CsI behaves as fast scintillators with well or totally suppressed slow decay component. The estimated fast/slow or fast/total ratio is related to the preparation method and to the remaining built-in contamination of the samples. The fast decay of pure CsI consists of two components with decay times of ≅1 and ≅10 ns - with an intensity ratio of 0.3 and 0.65 for gamma and for alpha radiation, respectively. This new ≅1 ns component and the ≅0.8 fast/total ratio may achieve an important role in many applications where fast timing properties are needed, substituting BaF 2 . (author) 18 refs.; 8 figs.; 3 tabs

Progress on Lead Photocathodes for Superconducting Injectors

CERN Document Server

Smedley, John; Langner, Jerzy; Lefferts, Richard; Lipski, Andrzej; Rao, Triveni; Sekutowicz, Jacek; Strzyzewski, P

2005-01-01

We present the results of our investigation of bulk, electroplated and vacuum deposited lead as suitable photocathode materials for superconducting RF injectors. The quantum efficiency of each sample is presented as a function of the wavelength of the incident light, from 310 nm to 190 nm. Quantum efficiencies of 0.3% have been obtained. Production of a niobium cavity with a lead-plated cathode is underway.

{Ni4O4} Cluster Complex to Enhance the Reductive Photocurrent Response on Silicon Nanowire Photocathodes

Directory of Open Access Journals (Sweden)

Yatin J. Mange

2017-02-01

Full Text Available Metal organic {Ni4O4} clusters, known oxidation catalysts, have been shown to provide a valuable route in increasing the photocurrent response on silicon nanowire (SiNW photocathodes. {Ni4O4} clusters have been paired with SiNWs to form a new photocathode composite for water splitting. Under AM1.5 conditions, the combination of {Ni4O4} clusters with SiNWs gave a current density of −16 mA/cm2, which corresponds to an increase in current density of 60% when compared to bare SiNWs. The composite electrode was fully characterised and shown to be an efficient and stable photocathode for water splitting.

Studies on a laser driven photoemissive high-brightness electron source and novel photocathodes

International Nuclear Information System (INIS)

Geng Rongli; Song Jinhu; Yu Jin

1997-01-01

A laser driven photoemissive high-brightness electron source at Beijing University is reported. Through a DC accelerating gap of 100 kV voltage, the device is capable of delivering high-brightness electron beam of 35-100 ps pulse duration when irradiated with a mode-locked YAG laser. The geometry of the gun is optimized with the aid of simulation codes EGUN and POISSON. The results of experimental studies on ion implanted photocathode and cesium telluride photocathode are given. The proposed laser driven superconducting RF gun is also discussed

Thermal Emittance Measurement of the Cs2Te Photocathode in FZD Superconducting RF

CERN Document Server

Xiang, R; Michel, P; Murcek, P; Teichert, J

2010-01-01

The thermal emittance of the photocathode is an interesting physical property for the photoinjector, because it decides the minimum emittance the photoinjector can finally achieve. In this paper we will report the latest results of the thermal emittance of the Cs2Te photocathode in FZD Superconducting RF gun. The measurement is performed with solenoid scan method with very low bunch charge and relative large laser spot on cathode, in order to reduce the space charge effect as much as possible, and meanwhile to eliminate the wake fields and the effect from beam halos.

CSI-EPT in Presence of RF-Shield for MR-Coils.

Science.gov (United States)

Arduino, Alessandro; Zilberti, Luca; Chiampi, Mario; Bottauscio, Oriano

2017-07-01

Contrast source inversion electric properties tomography (CSI-EPT) is a recently developed technique for the electric properties tomography that recovers the electric properties distribution starting from measurements performed by magnetic resonance imaging scanners. This method is an optimal control approach based on the contrast source inversion technique, which distinguishes itself from other electric properties tomography techniques for its capability to recover also the local specific absorption rate distribution, essential for online dosimetry. Up to now, CSI-EPT has only been described in terms of integral equations, limiting its applicability to homogeneous unbounded background. In order to extend the method to the presence of a shield in the domain-as in the recurring case of shielded radio frequency coils-a more general formulation of CSI-EPT, based on a functional viewpoint, is introduced here. Two different implementations of CSI-EPT are proposed for a 2-D transverse magnetic model problem, one dealing with an unbounded domain and one considering the presence of a perfectly conductive shield. The two implementations are applied on the same virtual measurements obtained by numerically simulating a shielded radio frequency coil. The results are compared in terms of both electric properties recovery and local specific absorption rate estimate, in order to investigate the requirement of an accurate modeling of the underlying physical problem.

High polarization photocathode R ampersand D at SLAC

International Nuclear Information System (INIS)

Maruyama, Takashi; Garwin, E.L.; Prepost, R.; Zaplac, G.H.

1993-01-01

This paper describes recent progress on the development of high polarization photocathodes for polarized electron sources. A strained InGaAs cathode has achieved a maximum electron-spin polarization of 71% and has demonstrated the strain enhancement of polarization for the first time. Strained GaAs cathodes have yielded polarizations as high as 90% with much higher quantum efficiency

A UV sensitive integrated micromegas with timepix readout

NARCIS (Netherlands)

Melai, J.; Breskin, Amos; Cortesi, Marco; Bilevych, Y.; Bilevych, Yevgen; Fransen, Martin; van der Graaf, Harry; Visschers, Jan; Blanco Carballo, V.M.; Salm, Cora; Schmitz, Jurriaan

2010-01-01

This article presents a detector system consisting of three components, a CMOS imaging array, a gaseous-detector structure with a Micromegas layout, and a UV-photon sensitive CsI reflective photocathode. All three elements have been monolithically integrated using simple post-processing steps. The

Simulated UO{sub 2} fuel containing CsI by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Wangle, T. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Břehová 7, Praha 1, 115 19 (Czech Republic); Tyrpekl, V. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Cologna, M., E-mail: marco.cologna@ec.europa.eu [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Somers, J. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany)

2015-11-15

Herein, an innovative preparation procedure has been deployed enabling, for the first time, the incorporation of volatile fission product simulant into highly dense nuclear fuel pellets. Highly volatile fission products were embedded in a dense UO{sub 2} matrix in the form of CsI by simply mixing starting materials and consolidation in a Spark Plasma Sintering step at 1000 °C with a 5 min dwell time. CsI particles were evenly distributed throughout the pellet and were located at the grain boundaries. The sintering rate is dependent on the O/U ratio of the powder. Addition of CsI also acts as a sintering aid, reducing the temperature of maximum densification. - Highlights: • A new method was developed to incorporation of volatile fission products simulants into dense nuclear fuel pellets. • CsI doped UO{sub 2} pellets were synthetized for the first time, by Spark Plasma Sintering. • The sintering rate in Spark Plasma Sintering is dependent on the O/U ratio of UO{sub 2+x}.

Equivalent Method of Solving Quantum Efficiency of Reflection-Mode Exponential Doping GaAs Photocathode

International Nuclear Information System (INIS)

Jun, Niu; Zhi, Yang; Ben-Kang, Chang

2009-01-01

The mathematical expression of the electron diffusion and drift length L DE of exponential doping photocathode is deduced. In the quantum efficiency equation of the reffection-mode uniform doping cathode, substituting L DE for L D , the equivalent quantum efficiency equation of the reffection-mode exponential doping cathode is obtained. By using the equivalent equation, theoretical simulation and experimental analysis shows that the equivalent index formula and formula-doped cathode quantum efficiency results in line. The equivalent equation avoids complicated calculation, thereby simplifies the process of solving the quantum efficiency of exponential doping photocathode

Experimental study on the CsI (Tl) crystal anti-compton detector in CDEX

International Nuclear Information System (INIS)

Liu Shukui; Yue Qian; Tang Changjian

2012-01-01

CDEX (China Dark matter Experiment) Collaboration will carry out direct search for dark matter with Ultra-Low Energy Threshold High Purity germanium (ULE-HPGe) detector at CJPL (China Jinping deep underground Laboratory). Before underground research, some experiments of the CsI (Tl) crystal Anti-Compton detector have been done on the ground, including light guide choice, wrapping material choice, height uniformity of CsI (Tl) crystal, side uniformity of CsI (Tl) crystal and the test results of all the crystals. Through the preliminary work on the ground, we have got some knowledge of the anti-compton detector and prepared for the underground experiment. (authors)

Visualization of a City Sustainability Index (CSI: Towards Transdisciplinary Approaches Involving Multiple Stakeholders

Directory of Open Access Journals (Sweden)

Koichiro Mori

2015-09-01

Full Text Available We have developed a visualized 3-D model of a City Sustainability Index (CSI based on our original concept of city sustainability in which a sustainable city is defined as one that maximizes socio-economic benefits while meeting constraint conditions of the environment and socio-economic equity on a permanent basis. The CSI is based on constraint and maximization indicators. Constraint indicators assess whether a city meets the necessary minimum conditions for city sustainability. Maximization indicators measure the benefits that a city generates in socio-economic aspects. When used in the policy-making process, the choice of constraint indicators should be implemented using a top-down approach. In contrast, a bottom-up approach is more suitable for defining maximization indicators because this technique involves multiple stakeholders (in a transdisciplinary approach. Using different materials of various colors, shapes, sizes, we designed and constructed the visualized physical model of the CSI to help people evaluate and compare the performance of different cities in terms of sustainability. The visualized model of the CSI can convey complicated information in a simple and straightforward manner to diverse stakeholders so that the sustainability analysis can be understood intuitively by ordinary citizens as well as experts. Thus, the CSI model helps stakeholders to develop critical thinking about city sustainability and enables policymakers to make informed decisions for sustainability through a transdisciplinary approach.

Secrecy performance analysis of SIMO underlay cognitive radio systems with outdated CSI

KAUST Repository

Lei, Hongjiang; Zhang, Jianming; Park, Kihong; Ansari, Imran Shafique; Pan, Gaofeng; Alouini, Mohamed-Slim

2017-01-01

This study investigates the secrecy outage performance of a single-input multiple-output underlay cognitive radio network (CRN) with outdated channel state information (CSI). The confidential messages are transmitted from transmitter to the destination, while a multi-antenna eavesdropper exists. The maximal ratio combining and selection combining schemes are utilised at the receivers to improve the quality of the received signal-to-noise ratio. The exact and asymptotic closed-form expressions of secrecy outage probability are derived, and simulation results are provided to verify the authors' proposed analytical results. The results reveal that imperfect CSI of main channels deteriorates the secrecy outage performance while that of eavesdropping and interfering channels has contrary effect, and only a unity diversity order can be obtained in underlay CRNs with imperfect CSI.

Secrecy performance analysis of SIMO underlay cognitive radio systems with outdated CSI

KAUST Repository

Lei, Hongjiang

2017-06-13

This study investigates the secrecy outage performance of a single-input multiple-output underlay cognitive radio network (CRN) with outdated channel state information (CSI). The confidential messages are transmitted from transmitter to the destination, while a multi-antenna eavesdropper exists. The maximal ratio combining and selection combining schemes are utilised at the receivers to improve the quality of the received signal-to-noise ratio. The exact and asymptotic closed-form expressions of secrecy outage probability are derived, and simulation results are provided to verify the authors\\' proposed analytical results. The results reveal that imperfect CSI of main channels deteriorates the secrecy outage performance while that of eavesdropping and interfering channels has contrary effect, and only a unity diversity order can be obtained in underlay CRNs with imperfect CSI.

Production and Studies of Photocathodes for High Intensity Electron Beams

CERN Document Server

Chevallay, E; Legros, P; Suberlucq, Guy; Trautner, H

2000-01-01

For short, high-intensity electron bunches, alkali-tellurides have proved to be a reliable photo-cathode material. Measurements of lifetimes in an rf gun of the CLIC Test Facility II at field strengths greater than 100 MV/m are presented. Before and after using them in this gun, the spectral response of the CS-Te and Rb-Te cathodes were determined with the help of an optical parametric oscillator. The behaviour of both materials can be described by Spicer's 3-step model. Whereas during the use the threshold for photo-emission in Cs-Te was shifted to higher proton energies, that of Rb-Te did not change. Our latest investigations on the stoichiometric ratio of the components are shown. The preparation of the photo-cathodes was monitored with 320 nm wavelength light , with the aim of improving the measurement sensitivity. The latest results on the protection of Cs-Te cathode surfaces with CsBr against pollution are summarized. New investigations on high mean current production are presented.,

A novel scaling law relating the geometrical dimensions of a photocathode radio frequency gun to its radio frequency properties

Science.gov (United States)

Lal, Shankar; Pant, K. K.; Krishnagopal, S.

2011-12-01

Developing a photocathode RF gun with the desired RF properties of the π-mode, such as field balance (eb) ˜1, resonant frequency fπ = 2856 MHz, and waveguide-to-cavity coupling coefficient βπ ˜1, requires precise tuning of the resonant frequencies of the independent full- and half-cells (ff and fh), and of the waveguide-to-full-cell coupling coefficient (βf). While contemporary electromagnetic codes and precision machining capability have made it possible to design and tune independent cells of a photocathode RF gun for desired RF properties, thereby eliminating the need for tuning, access to such computational resources and quality of machining is not very widespread. Therefore, many such structures require tuning after machining by employing conventional tuning techniques that are iterative in nature. Any procedure that improves understanding of the tuning process and consequently reduces the number of iterations and the associated risks in tuning a photocathode gun would, therefore, be useful. In this paper, we discuss a method devised by us to tune a photocathode RF gun for desired RF properties under operating conditions. We develop and employ a simple scaling law that accounts for inter-dependence between frequency of independent cells and waveguide-to-cavity coupling coefficient, and the effect of brazing clearance for joining of the two cells. The method has been employed to successfully develop multiple 1.6 cell BNL/SLAC/UCLA type S-band photocathode RF guns with the desired RF properties, without the need to tune them by a tiresome cut-and-measure process. Our analysis also provides a physical insight into how the geometrical dimensions affect the RF properties of the photo-cathode RF gun.

New Antimony Selenide/Nickel Oxide Photocathode Boosts the Efficiency of Graphene Quantum-Dot Co-Sensitized Solar Cells.

Science.gov (United States)

Kolay, Ankita; Kokal, Ramesh K; Kalluri, Ankarao; Macwan, Isaac; Patra, Prabir K; Ghosal, Partha; Deepa, Melepurath

2017-10-11

A novel assembly of a photocathode and a photoanode is investigated to explore their complementary effects in enhancing the photovoltaic performance of a quantum-dot solar cell (QDSC). While p-type nickel oxide (NiO) has been used previously, antimony selenide (Sb 2 Se 3 ) has not been used in a QDSC, especially as a component of a counter electrode (CE) architecture that doubles as the photocathode. Here, near-infrared (NIR) light-absorbing Sb 2 Se 3 nanoparticles (NPs) coated over electrodeposited NiO nanofibers on a carbon (C) fabric substrate was employed as the highly efficient photocathode. Quasi-spherical Sb 2 Se 3 NPs, with a band gap of 1.13 eV, upon illumination, release photoexcited electrons in addition to other charge carriers at the CE to further enhance the reduction of the oxidized polysulfide. The p-type conducting behavior of Sb 2 Se 3 , coupled with a work function at 4.63 eV, also facilitates electron injection to polysulfide. The effect of graphene quantum dots (GQDs) as co-sensitizers as well as electron conduits is also investigated in which a TiO 2 /CdS/GQDs photoanode structure in combination with a C-fabric CE delivered a power-conversion efficiency (PCE) of 5.28%, which is a vast improvement over the 4.23% that is obtained by using a TiO 2 /CdS photoanode (without GQDs) with the same CE. GQDs, due to a superior conductance, impact efficiency more than Sb 2 Se 3 NPs do. The best PCE of a TiO 2 /CdS/GQDs-nS 2- /S n 2- -Sb 2 Se 3 /NiO/C-fabric cell is 5.96% (0.11 cm 2 area), which, when replicated on a smaller area of 0.06 cm 2 , is seen to increase dramatically to 7.19%. The cell is also tested for 6 h of continuous irradiance. The rationalization for the channelized photogenerated electron movement, which augments the cell performance, is furnished in detail in these studies.

Enhanced photoelectrochemical water splitting by oxides heterojunction photocathode coupled with Ag.

Science.gov (United States)

Lu, Xue; Liu, Zhifeng

2017-08-14

A novel one-dimensional Co 3 O 4 /CuO/Ag composite structure film was directly grown on indium tin oxide glass substrate by a simple hydrothermal method and electrodeposition method. The film was employed for the first time as a photocathode for photoelectrochemical (PEC) water splitting to generate hydrogen. The photocurrent density of the Co 3 O 4 /CuO/Ag composite structure achieved -5.13 mA cm -2 at -0.2 V vs. RHE, which is roughly 12.8 times that of 1D Co 3 O 4 nanowires and 3.31 times Co 3 O 4 /CuO heterojunction photocathodes. The enhanced PEC performance of this Co 3 O 4 /CuO/Ag composite structure ascribes increased light-harvesting and light-absorption, distensible photoresponse range, decreased interface charge transfer resistance, and improved photogenerated electron-hole pairs transfer and separation.

Performance Analysis of Communications under Energy Harvesting Constraints with noisy CSI

KAUST Repository

Znaidi, Mohamed Ridha Ali

2016-01-06

In energy harvesting communications, the transmitters have to adapt transmission to availability of energy harvested during the course of communication. The performance of the transmission depends on the channel conditions which vary randomly due to environmental changes. In this work, we consider the problem of power allocation taking into account the energy arrivals over time and the degree of channel state information (CSI) available at the transmitter, to maximize the throughput. Differently from previous work, the CSI at the transmitter is not perfect and may include estimation errors. We solve this problem with respect to the Energy Harvesting constraints. We determine the optimal power in the case where the channel is assumed to be perfectly known at the receiver. Also, we obtain the power policy when the transmitter has no CSI. Furthermore, we analyze the asymptotic average throughput in a system where the average recharge rate goes asymptotically to zero and when it is very high.

Design and fabrication of prototype 6×6 cm2 microchannel plate photodetector with bialkali photocathode for fast timing applications

International Nuclear Information System (INIS)

Xie, Junqi; Byrum, Karen; Demarteau, Marcel; Gregar, Joseph; May, Edward; Virgo, Mathew; Wagner, Robert; Walters, Dean; Wang, Jingbo; Xia, Lei; Zhao, Huyue

2015-01-01

Planar microchannel plate-based photodetectors with a bialkali photocathode are able to achieve photon detection with very good time and position resolution. A 6×6 cm 2 photodetector production facility was designed and built at Argonne National Laboratory. Small form-factor MCP-based photodetectors completely constructed out of glass were designed and prototypes were successfully fabricated. Knudsen effusion cells were incorporated in the photocathode growth chamber to achieve uniform and high quantum efficiency photocathodes. The thin film uniformity was simulated and measured for an antimony film deposition, showing uniformity of better than 10%. Several prototype devices with bialkali photocathodes have been fabricated with the described system and their characteristics were evaluated in the large signal (multi-PE) limit. A typical prototype device exhibits time-of-flight resolution of ~27 psec and differential time resolution of ~9 psec, corresponding to spatial resolution of ~0.65 mm

Advances in DC photocathode electron guns

International Nuclear Information System (INIS)

Dunham M, Bruce; Heartmann, P.; Reza Kazimi; Hongxiu Liu; Poelker, B.M.; Price, J.S.; Rutt, P.M.; Schneider, W.J.; Sinclair K, Charles

1998-01-01

At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughout. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion back-bombardment, and precise control of all of the electrons emitted from the cathode. In this paper, the authors will review recent results and discuss implications for future photocathode guns

Advances in DC photocathode electron guns

International Nuclear Information System (INIS)

Dunham, B. M.; Hartmann, P.; Kazimi, R.; Liu, H.; Poelker, B. M.; Price, J. S.; Rutt, P. M.; Schneider, W. J.; Sinclair, C. K.

1999-01-01

At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughput. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion backbombardment, and precise control of all of the electrons emitted from the cathode. In this paper, we will review recent results and discuss implications for future photocathode guns

Measurements of Photocathode Operational Lifetime at Beam Currents up to 10 mA using an Improved DC High Voltage GaAs Photogun

International Nuclear Information System (INIS)

Grames, J.; Poelker, M.; Adderley, P.; Brittian, J.; Clark, J.; Hansknecht, J.; Machie, D.; Stutzman, M. L.; Surles-Law, K.

2007-01-01

This work extends past research at Jefferson Lab aimed at better appreciating the mechanisms that limit photocathode operational lifetime at high current (> 1 mA). Specifically, the performance of an improved 100 kV DC high voltage load locked photogun will be described. Although difficult to measure directly, we believe the new gun has better vacuum conditions compared to the original gun, as indicated by enhanced photocathode lifetimes exceeding 2000 C using a 1.55 mm diameter drive laser spot at the photocathode. In addition, the dependence of the lifetime on the laser spot size at the photocathode was measured and a charge density lifetime exceeding 106 C/cm2 was measured with a 0.32 mm laser spot diameter

Measurements of photocathode operational lifetime at beam currents up to 10-mA using an improved DC high voltage GaAs photogun

International Nuclear Information System (INIS)

J. Grames; M. Poelker; P. Adderley; J. Brittian; J. Clark; J. Hansknecht; D. Machie; M.L. Stutzman; K. Surles-Law

2007-01-01

This work extends past research at Jefferson Lab aimed at better appreciating the mechanisms that limit photocathode operational lifetime at high current (> 1 mA). Specifically, the performance of an improved 100 kV DC high voltage load locked photogun will be described. Although difficult to measure directly, we believe the new gun has better vacuum conditions compared to the original gun, as indicated by enhanced photocathode lifetimes exceeding 2000 C using a 1.55 mm diameter drive laser spot at the photocathode. In addition, the dependence of the lifetime on the laser spot size at the photocathode was measured and a charge density lifetime exceeding 10 6 C/cm 2 was measured with a 0.32 mm laser spot diameter

Synchrotron x-ray study of a low roughness and high efficiency K2CsSb photocathode during film growth

International Nuclear Information System (INIS)

Xie, Junqi; Demarteau, Marcel; Wagner, Robert; Schubert, Susanne; Gaowei, Mengjia; Attenkofer, Klaus; Walsh, John; Smedley, John; Ben-Zvi, Ilan; Wong, Jared; Feng, Jun; Padmore, Howard; Ruiz-Oses, Miguel; Ding, Zihao; Liang, Xue; Muller, Erik

2017-01-01

Reduction of roughness to the nm level is critical of achieving the ultimate performance from photocathodes used in high gradient fields. The thrust of this paper is to explore the evolution of roughness during sequential growth, and to show that deposition of multilayer structures consisting of very thin reacted layers results in an nm level smooth photocathode. Synchrotron x-ray methods were applied to study the multi-step growth process of a high efficiency K 2 CsSb photocathode. A transition point of the Sb film grown on Si was observed at the film thickness of ∼40 Å with the substrate temperature at 100 °C and the growth rate at 0.1 Å s −1 . The final K 2 CsSb photocathode exhibits a thickness of around five times that of the total deposited Sb film regardless of how the Sb film was grown. The film surface roughening process occurs first at the step when K diffuses into the crystalline Sb. The photocathode obtained from the multi-step growth exhibits roughness in an order of magnitude lower than the normal sequential process. X-ray diffraction measurements show that the material goes through two structural changes of the crystalline phase during formation, from crystalline Sb to K 3 Sb and finally to K 2 CsSb. (paper)

Distributed cognitive two-way relay beamformer designs under perfect and imperfect CSI

KAUST Repository

Pandarakkottilil, Ubaidulla

2011-09-01

In this paper, we present distributed two-way relay beamformer designs for a cognitive radio network (CRN) in which a pair of cognitive (or secondary) transceiver nodes communicate with each other assisted by a set of cognitive two-way relay nodes. The secondary nodes share the spectrum with a licensed primary user (PU) node, and each node is assumed to be equipped with a single transmit/receive antenna. The interference to the PU resulting from the transmission from the cognitive nodes is kept below a specified limit. First, we consider relay beamformer designs assuming the availability of perfect channel state information (CSI). For this case, a mean-square error (MSE)-constrained beamformer that minimizes the total relay transmit power, and an MSE-balancing beamformer with a constraint on the total relay transmit power are proposed. Next, we consider relay beamformer designs assuming that the available CSI is imperfect. For this case too, we consider the same problems as those in the case of perfect CSI, and propose beamformer designs that are robust to the errors in the CSI. We show that the proposed designs can be reformulated as convex optimization problems that can be solved efficiently. Through numerical simulations, we illustrate the performance of the proposed designs. © 2011 IEEE.

Heat load of a GaAs photocathode in an SRF electron gun

International Nuclear Information System (INIS)

Wang Erdong; Zhao Kui; Jorg Kewisch; Ilan Ben-Zvi; Andrew Burrill; Trivini Rao; Wu Qiong; Animesh Jain; Ramesh Gupta; Doug Holmes

2011-01-01

A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved by using a superconducting radio frequency (SRF) electron gun, which delivers beams of a higher brightness than that from DC guns because the field gradient at the cathode is higher. SRF guns with metal and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since a bulk gallium arsenide (GaAs) photocathode is normal conducting, a problem arises from the heat load stemming from the cathode. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and verification by measuring the quality factor of the gun with and without the cathode at 2 K. We simulate heat generation and flow from the GaAs cathode using the ANSYS program. By following the findings with the heat load model, we designed and fabricated a new cathode holder (plug) to decrease the heat load from GaAs. (authors)

Charter Schools Indicators: A Report from the Center on Educational Governance University of Southern California. CSI-USC 2010

Science.gov (United States)

Center on Educational Governance, 2010

2010-01-01

CSI-USC continues to make sense of what the California statewide data system provides. This fourth annual report gauges multiple measures of academic and financial performance, probing well beyond mere test scores. Ratings in familiar green, yellow, and red cover four areas: financial resources and investment, school quality, student performance…

CSI : Alaska

International Nuclear Information System (INIS)

Letwin, S.

2005-01-01

This presentation emphasized the need for northern gas supply at a time when conventional natural gas supplies are decreasing and demand is growing. It highlighted the unique qualifications of Enbridge Inc. in creating an infrastructure to move the supply to where it is in most demand. Enbridge has substantial northern experience and has a unique approach for the construction of the Alaskan Gas Pipeline which entails cooperation, stability and innovation (CSI). Enbridge's role in the joint venture with AltaGas and Inuvialuit Petroleum was discussed along with its role in the construction of the first Canadian pipeline in 1985. The 540 mile pipeline was buried in permafrost. A large percentage of Enbridge employees are of indigenous descent. Enbridge recognizes that the amount of capital investment and the associated risk needed for the Alaska Gas Pipeline will necessitate a partnership of producers, pipeline companies, Native organizations, the State of Alaska, market participants and other interested parties. 9 figs

Photoemission spectroscopy study of a multi-alkali photocathode

CERN Document Server

Ettema, A R H

2000-01-01

In this paper a photoemission study of the highest core levels of the elements and the electron escape barrier (work function) in a multi-alkali photocathode are presented. The core levels indicate that the alkali atoms are in an oxidized state and therefore the compound Na sub 2 KSb can be regarded as an ionic semiconductor. The measured escape barrier of the Cs sub 2 O surface layer is determined as 2.3 eV.

Study of residual gas adsorption on GaN nanowire arrays photocathode

Energy Technology Data Exchange (ETDEWEB)

Xia, Sihao; Liu, Lei, E-mail: liu1133_cn@sina.com.cn; Diao, Yu; Kong, Yike

2017-05-01

Highlights: • H{sub 2}O is more easily to absorb on the nanowire surface. • The work function increase after residual gas adsorption. • Bandgaps of the nanowire increase slightly. • Absorption coefficient is reduced and moves to higher energy side. - Abstract: In order to find out the influences of residual gas on GaN nanowire arrays photocathode, the optoelectronic properties of adsorption system are calculated on the basis of first principles. Results suggest that the residual gas adsorption will increase the work function and introduce a dipole moment with a direction from the nanowire to the adsorbates. The surface structures are changed and electrons transfer from nanowire to gas molecule. The bandgaps are enhanced after adsorption. Besides, the peak of absorption coefficients is reduced and moves to higher energy side. It is discovered that residual gas will drastically degrade the characteristics and lifetime of GaN nanowire arrays photocathode.

Investigating CSI: portrayals of DNA testing on a forensic crime show and their potential effects.

Science.gov (United States)

Ley, Barbara L; Jankowski, Natalie; Brewer, Paul R

2012-01-01

The popularity of forensic crime shows such as CSI has fueled debate about their potential social impact. This study considers CSI's potential effects on public understandings regarding DNA testing in the context of judicial processes, the policy debates surrounding crime laboratory procedures, and the forensic science profession, as well as an effect not discussed in previous accounts: namely, the show's potential impact on public understandings of DNA and genetics more generally. To develop a theoretical foundation for research on the "CSI effect," it draws on cultivation theory, social cognitive theory, and audience reception studies. It then uses content analysis and textual analysis to illuminate how the show depicts DNA testing. The results demonstrate that CSI tends to depict DNA testing as routine, swift, useful, and reliable and that it echoes broader discourses about genetics. At times, however, the show suggests more complex ways of thinking about DNA testing and genetics.

Tight comparison of Mg and Y thin film photocathodes obtained by the pulsed laser deposition technique

Energy Technology Data Exchange (ETDEWEB)

Lorusso, A. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Gontad, F., E-mail: francisco.gontad@le.infn.it [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Solombrino, L. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Chiadroni, E. [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, 00044 Frascati (Italy); Broitman, E. [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping (Sweden); Perrone, A. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy)

2016-11-11

In this work Magnesium (Mg) and Yttrium (Y) thin films have been deposited on Copper (Cu) polycrystalline substrates by the pulsed laser ablation technique for photocathode application. Such metallic materials are studied for their interesting photoemission properties and are proposed as a good alternative to the Cu photocathode, which is generally used in radio-frequency guns. Mg and Y films were uniform with no substantial differences in morphology; a polycrystalline structure was found for both of them. Photoemission measurements of such cathodes based on thin films were performed, revealing a quantum efficiency higher than Cu bulk. Photoemission theory according to the three-step model of Spicer is invoked to explain the superior photoemission performance of Mg with respect to Y. - Highlights: • Mg and Y thin film photocathodes were successfully prepared by pulsed laser deposition. • Mg quantum efficiency is higher than Y, despite its higher work function. • The three-step model of Spicer justify the difference in quantum efficiency.

Multifractal property of Chinese stock market in the CSI 800 index based on MF-DFA approach

Science.gov (United States)

Zhu, Huijian; Zhang, Weiguo

2018-01-01

CSI 800 index consists of CSI 500 index and CSI 300 index, aiming to reflect the performance of stocks with large, mid and small size of China A share market. In this paper we analyze the multifractal structure of Chinese stock market in the CSI 800 index based on the multifractal detrended fluctuation analysis (MF-DFA) method. We find that the fluctuation of the closing logarithmic returns have multifractal properties, the shape and width of multifractal spectrum are depended on the weighing order q. More interestingly, we observe a bigger market crash in June-August 2015 than the one in 2008 based on the local Hurst exponents. The result provides important information for further study on dynamic mechanism of return fluctuation and whether it would trigger a new financial crisis.

Advances in DC photocathode electron guns

International Nuclear Information System (INIS)

Dunham, B.M.; Hartmann, P.; Kazimi, R.; Liu, H.; Poelker, B.M.; Price, J.S.; Rutt, P.M.; Schneider, W.J.; Sinclair, C.K.

1999-01-01

At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughput. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion backbombardment, and precise control of all of the electrons emitted from the cathode. In this paper, we will review recent results and discuss implications for future photocathode guns. copyright 1999 American Institute of Physics

A polarized photoluminescence study of strained layer GaAs photocathodes

International Nuclear Information System (INIS)

Mair, R.A.

1996-07-01

Photoluminescence measurements have been made on a set of epitaxially grown strained GaAs photocathode structures. The photocathodes are designed to exhibit a strain-induced enhancement of the electron spin polarization obtainable by optical pumping with circularly polarized radiation of near band gap energy. For the case of non-strained GaAs, the degree of spin polarization is limited to 50% by crystal symmetry. Under an appropriate uniaxial compression or tension, however, the valence band structure near the gap minimum is modified such that a spin polarization of 100% is theoretically possible. A total of nine samples with biaxial compressive strains ranging from zero to ∼0.8% are studied. X-ray diffraction analysis, utilizing Bragg reflections, is used to determine the crystal lattice structure of the samples. Luminescence spectra and luminescence circular polarization data are obtained at room temperature, ∼78 K and ∼12 K. The degree of luminescence circular polarization is used as a relative measure of the photo-excited electron spin polarization. The room temperature luminescence circular polarization data is compared with the measured electron spin polarization when the samples are used as electron photo-emitters with a negative electron affinity surface preparation. The luminescence data is also analyzed in conjunction with the crystal structure data with the goal of understanding the strain dependent valence band structure, optical pumping characteristics and spin depolarization mechanisms of the photocathode structures. A simple model is used to describe the luminescence data, obtained for the set of samples. Within the assumptions of the model, the deformation potentials a, b and d for GaAs are determined. The measured values are a = -10.16±.21 eV, b = -2.00±.05 eV and d = -4.87±.29 eV. Good agreement with published values of the deformation potentials provides support for the model used to describe the data

CdTeO3 Deposited Mesoporous NiO Photocathode for a Solar Cell

Directory of Open Access Journals (Sweden)

Chuan Zhao

2014-01-01

Full Text Available Semiconductor sensitized NiO photocathodes have been fabricated by successive ionic layer adsorption and reaction (SILAR method depositing CdTeO3 quantum dots onto mesoscopic NiO films. A solar cell using CdTeO3 deposited NiO mesoporous photocathode has been fabricated. It yields a photovoltage of 103.7 mV and a short-circuit current density of 0.364 mA/cm2. The incident photon to current conversion efficiency (IPCE value is found to be 12% for the newly designed NiO/CdTeO3 solar cell. It shows that the p-type NiO/CdTeO3 structure could be successfully utilized to fabricate p-type solar cell.

Observation of Cherenkov rings using a low-pressure parallel-plate chamber and a solid cesium-iodide photocathode

International Nuclear Information System (INIS)

Lockyer, N.S.; Millan, J.E.; Lu, C.; McDonald, K.T.; Lopez, A.

1993-01-01

We have observed Cherenkov rings from minimum-ionizing particles using a low-pressure, parallel-plate pad-chamber with a cesium-iodide solid photocathode. This detector is blind to minimum-ionizing particles, and sensitive to Cherenkov photons of wavelengths 170-210 nm. An average of 5 photoelectrons per Cherenkov ring were detected using a 2-cm-thick radiator of liquid C 6 F 14 . This paper reports on the chamber construction, photocathode preparation and testbeam results. (orig.)

CSI 3.0: a web server for identifying secondary and super-secondary structure in proteins using NMR chemical shifts.

Science.gov (United States)

Hafsa, Noor E; Arndt, David; Wishart, David S

2015-07-01

The Chemical Shift Index or CSI 3.0 (http://csi3.wishartlab.com) is a web server designed to accurately identify the location of secondary and super-secondary structures in protein chains using only nuclear magnetic resonance (NMR) backbone chemical shifts and their corresponding protein sequence data. Unlike earlier versions of CSI, which only identified three types of secondary structure (helix, β-strand and coil), CSI 3.0 now identifies total of 11 types of secondary and super-secondary structures, including helices, β-strands, coil regions, five common β-turns (type I, II, I', II' and VIII), β hairpins as well as interior and edge β-strands. CSI 3.0 accepts experimental NMR chemical shift data in multiple formats (NMR Star 2.1, NMR Star 3.1 and SHIFTY) and generates colorful CSI plots (bar graphs) and secondary/super-secondary structure assignments. The output can be readily used as constraints for structure determination and refinement or the images may be used for presentations and publications. CSI 3.0 uses a pipeline of several well-tested, previously published programs to identify the secondary and super-secondary structures in protein chains. Comparisons with secondary and super-secondary structure assignments made via standard coordinate analysis programs such as DSSP, STRIDE and VADAR on high-resolution protein structures solved by X-ray and NMR show >90% agreement between those made with CSI 3.0. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

High time resolution beam-based measurement of the rf-to-laser jitter in a photocathode rf gun

Directory of Open Access Journals (Sweden)

Zhen Zhang

2014-03-01

Full Text Available Characterizing the rf-to-laser jitter in the photocathode rf gun and its possible origins is important for improving the synchronization and beam quality of the linac based on the photocathode rf gun. A new method based on the rf compression effect in the photocathode rf gun is proposed to measure the rf-to-laser jitter in the gun. By taking advantage of the correlation between the rf compression and the laser injection phase, the error caused by the jitter of the accelerating field in the gun is minimized and thus 10 fs time resolution is expected. Experimental demonstration at the Tsinghua Thomson scattering x-ray source with a time resolution better than 35 fs is reported in this paper. The experimental results are successfully used to obtain information on the possible cause of the jitter and the accompanying drifts.

Experimental studies of the charge limit phenomenon in NEA GaAs photocathodes

International Nuclear Information System (INIS)

Tang, H.; Alley, R.K.; Aoyagi, H.; Clendenin, J.E.; Frisch, J.C.; Mulhollan, G.A.; Saez, P.J.; Schultz, D.C.; Turner, J.L.

1994-06-01

Negative electron affinity GaAs photocathodes have been in continuous use at SLAC for generating polarized electron beams since early 1992. If the quantum efficiency of a GaAs cathode is below a critical value, the maximum photoemitted charge with photons of energies close to the band gap in a 2-ns pulse is found to be limited by the intrinsic properties of the cathode instead of by the space charge limit. We have studied this novel charge limit phenomenon in a variety of GaAs photocathodes of different structures and doping densities. We find that the charge limit is strongly dependent on the cathode's quantum efficiency and the extraction electric field, and to a lesser degree on the excitation laser wavelength. In addition, we show that the temporal behavior of the charge limit depends critically on the doping density

Secure Communication for Two-Way Relay Networks with Imperfect CSI

Directory of Open Access Journals (Sweden)

Cong Sun

2017-09-01

Full Text Available This paper considers a two-way relay network, where two legitimate users exchange messages through several cooperative relays in the presence of an eavesdropper, and the Channel State Information (CSI of the eavesdropper is imperfectly known. The Amplify-and-Forward (AF relay protocol is used. We design the relay beamforming weights to minimize the total relay transmit power, while requiring the Signal-to-Noise-Ratio (SNRs of the legitimate users to be higher than the given thresholds and the achievable rate of the eavesdropper to be upper-bounded. Due to the imperfect CSI, a robust optimization problem is summarized. A novel iterative algorithm is proposed, where the line search technique is applied, and the feasibility is preserved during iterations. In each iteration, two Quadratically-Constrained Quadratic Programming (QCQP subproblems and a one-dimensional subproblem are optimally solved. The optimality property of the robust optimization problem is analyzed. Simulation results show that the proposed algorithm performs very close to the non-robust model with perfect CSI, in terms of the obtained relay transmit power; it~achieves higher secrecy rate compared to the existing work. Numerically, the proposed algorithm converges very quickly, and more than 85% of the problems are solved optimally.

Development of Thin Film Amorphous Silicon Tandem Junction Based Photocathodes Providing High Open-Circuit Voltages for Hydrogen Production

Directory of Open Access Journals (Sweden)

F. Urbain

2014-01-01

Full Text Available Hydrogenated amorphous silicon thin film tandem solar cells (a-Si:H/a-Si:H have been developed with focus on high open-circuit voltages for the direct application as photocathodes in photoelectrochemical water splitting devices. By temperature variation during deposition of the intrinsic a-Si:H absorber layers the band gap energy of a-Si:H absorber layers, correlating with the hydrogen content of the material, can be adjusted and combined in a way that a-Si:H/a-Si:H tandem solar cells provide open-circuit voltages up to 1.87 V. The applicability of the tandem solar cells as photocathodes was investigated in a photoelectrochemical cell (PEC measurement set-up. With platinum as a catalyst, the a-Si:H/a-Si:H based photocathodes exhibit a high photocurrent onset potential of 1.76 V versus the reversible hydrogen electrode (RHE and a photocurrent of 5.3 mA/cm2 at 0 V versus RHE (under halogen lamp illumination. Our results provide evidence that a direct application of thin film silicon based photocathodes fulfills the main thermodynamic requirements to generate hydrogen. Furthermore, the presented approach may provide an efficient and low-cost route to solar hydrogen production.

Integrated MoSe2 with n+p-Si photocathodes for solar water splitting with high efficiency and stability

Science.gov (United States)

Huang, Guanping; Mao, Jie; Fan, Ronglei; Yin, Zhihao; Wu, Xi; Jie, Jiansheng; Kang, Zhenhui; Shen, Mingrong

2018-01-01

Many earth-abundant transition metal dichalcogenides (TMDs) have been employed as catalysts for H2 evolution reaction (HER); however, their impactful integration onto photocathodes for photoelectrochemical (PEC) HER is less developed. In this study, we directly sputtered a MoSe2 catalyst onto an n+p-Si photocathode for efficient and stable PEC-HER. An onset potential of 0.4 V vs. RHE, a saturated photocurrent of 29.3 mA/cm2, a fill factor of 0.32, and an energy conversion efficiency of 3.8% were obtained under 100 mA/cm2 Xe lamp illumination. Such superior PEC properties were ascribed to the nearly vertically standing two dimensional MoSe2 rough surface layer and the sharp interface between Si and MoSe2 with small charge transfer resistance. The balance between the reflectivity of the electrode surface and the absorptivity of MoSe2 was also discussed. In addition, the MoSe2 layer can protect the n+p-Si photocathode with a 120 h stability due to its initial growth on Si with high flatness and compactness. This study provides a path to the effective and scalable growth of TMDs onto the Si photocathode aiming for high efficiency and stability.

Beam Dynamics Simulation of Photocathode RF Electron Gun at the PBP-CMU Linac Laboratory

Science.gov (United States)

Buakor, K.; Rimjaem, S.

2017-09-01

Photocathode radio-frequency (RF) electron guns are widely used at many particle accelerator laboratories due to high quality of produced electron beams. By using a short-pulse laser to induce the photoemission process, the electrons are emitted with low energy spread. Moreover, the photocathode RF guns are not suffered from the electron back bombardment effect, which can cause the limited electron current and accelerated energy. In this research, we aim to develop the photocathode RF gun for the linac-based THz radiation source. Its design is based on the existing gun at the PBP-CMU Linac Laboratory. The gun consists of a one and a half cell S-band standing-wave RF cavities with a maximum electric field of about 60 MV/m at the centre of the full cell. We study the beam dynamics of electrons traveling through the electromagnetic field inside the RF gun by using the particle tracking program ASTRA. The laser properties i.e. transverse size and injecting phase are optimized to obtain low transverse emittance. In addition, the solenoid magnet is applied for beam focusing and emittance compensation. The proper solenoid magnetic field is then investigated to find the optimum value for proper emittance conservation condition.

Two-way CSI-assisted AF relaying with HPA nonlinearity

KAUST Repository

Qi, Jian; Aissa, Sonia; Alouiniz, Mohamed-Slim

2015-01-01

In this paper, we investigate half-duplex two-way dual-hop channel state information (CSI)-assisted amplify-andforward (AF) relaying in the presence of high-power amplifier (HPA) nonlinearity at relays. The expression for the end-toend signal

Radiation damage in undoped CsI and CsI(Tl)

International Nuclear Information System (INIS)

Woody, C.L.; Kierstead, J.A.; Levy, P.W.; Stoll, S.

1992-01-01

Radiation damage has been studied in undoped CsI and CsI(TI) crystals using 60 Co gamma radiation for doses up to ∼ 4.2 x 10 6 . Samples from various manufacturers were measured ranging in size from 2.54 cm long cylinders to a 30 cm long block. Measurements were made on the change in optical transmission and scintillation light output as a function of dose. Although some samples showed a small change in transmission, a significant change in light output was observed for all samples. Recovery from damage was also studied as a function of time and exposure to UV light. A short lived phosphorescence was observed in undoped CsI, similar to the phosphorescence seen in CsI(TI)

High-performance a -Si/c-Si heterojunction photoelectrodes for photoelectrochemical oxygen and hydrogen evolution

KAUST Repository

Wang, Hsin Ping

2015-05-13

Amorphous Si (a-Si)/crystalline Si (c-Si) heterojunction (SiHJ) can serve as highly efficient and robust photoelectrodes for solar fuel generation. Low carrier recombination in the photoelectrodes leads to high photocurrents and photovoltages. The SiHJ was designed and fabricated into both photoanode and photocathode with high oxygen and hydrogen evolution efficiency, respectively, by simply coating of a thin layer of catalytic materials. The SiHJ photoanode with sol-gel NiOx as the catalyst shows a current density of 21.48 mA/cm2 at the equilibrium water oxidation potential. The SiHJ photocathode with 2 nm sputter-coated Pt catalyst displays excellent hydrogen evolution performance with an onset potential of 0.640 V and a solar to hydrogen conversion efficiency of 13.26%, which is the highest ever reported for Si-based photocathodes. © 2015 American Chemical Society.

S-11 and S-20 photocathode research activity. Rev. 1

International Nuclear Information System (INIS)

Gex, F.; Huen, T.; Kalibjian, R.

1984-01-01

The S-1 semi-transparent photocathode is the only one that can be used to study the 1.06 μm neodynium laser pulses of less than 10 ps duration. We first reviewed the recent results obtained at the Paris Observatory (research sponsored by the CEA), and then we tried to determine the role of the main constituents and their contributions in photoemission

Behind the Nature of Titanium Oxide Excellent Surface Passivation and Carrier Selectivity of c-Si

DEFF Research Database (Denmark)

Plakhotnyuk, Maksym; Crovetto, Andrea; Hansen, Ole

We present an expanded study of the passivation properties of titanium dioxide (TiO2) on p-type crystalline silicon (c-Si). We report a low surface recombination velocity (16 cm/s) for TiO2 passivation layers with a thin tunnelling oxide interlayer (SiO2 or Al2O3) on p-type crystalline silicon (c-Si......), and post-deposition annealing temperature were investigated. We have observed that that SiO2 and Al2O3 interlayers enhance the TiO2 passivation of c-Si. TiO2 thin film passivation layers alone result in lower effective carrier lifetime. Further annealing at 200  ̊C in N2 gas enhances the surface...

Achievable Rates of Cognitive Radio Networks Using Multi-Layer Coding with Limited CSI

KAUST Repository

Sboui, Lokman

2016-03-01

In a Cognitive Radio (CR) framework, the channel state information (CSI) feedback to the secondary transmitter (SU Tx) can be limited or unavailable. Thus, the statistical model is adopted in order to determine the system performance using the outage concept. In this paper, we adopt a new approach using multi-layer-coding (MLC) strategy, i.e., broadcast approach, to enhance spectrum sharing over fading channels. First, we consider a scenario where the secondary transmitter has no CSI of both the link between SU Tx and the primary receiver (cross-link) and its own link. We show that using MLC improves the cognitive rate compared to the rate provided by a singlelayer- coding (SLC). In addition, we observe numerically that 2-Layer coding achieves most of the gain for Rayleigh fading. Second, we analyze a scenario where SU Tx is provided by partial CSI about its link through quantized CSI. We compute its achievable rate adopting the MLC and highlight the improvement over SLC. Finally, we study the case in which the cross-link is perfect, i.e., a cooperative primary user setting, and compare the performance with the previous cases. We present asymptotic analysis at high power regime and show that the cooperation enhances considerably the cognitive rate at high values of the secondary power budget.

Corporate social investment and a company’s image: A case of a CSI initiative in a South African low income community

Directory of Open Access Journals (Sweden)

Paul-Francois Muzindutsi

2015-11-01

Full Text Available One of the goals of corporate social investment (CSI is to ensure that a company becomes a responsible entity which acts as a conscientious citizen within a society. CSI plays an important role in enhancing how a company is perceived within the community it operates in. This paper used a combination of qualitative and quantitative research designs to investigate the effect of a specific CSI initiative on a company’s image within a low income community in South Africa. Semi-structured interviews and survey questionnaire were used to collect data from community members in the township of Bophelong, South Africa. Results show that, if adequately managed, CSI initiatives tend to enhance company’s image as well as its relations with the community it operates in. However, if not adequately managed CSI can created unreachable expectations that can negatively affect a company’s image. Thus, companies better manage their CSI initiatives have an increased opportunity to enhance their reputation within the community they operate in.

Approaching total absorption of graphene strips using a c-Si subwavelength periodic membrane

Science.gov (United States)

Sang, Tian; Wang, Rui; Li, Junlang; Zhou, Jianyu; Wang, Yueke

2018-04-01

Approaching total absorption of graphene strips at near infrared using a crystalline-silicon (c-Si) subwavelength periodic membrane (SPM) is presented. The absorption in graphene strips in a c-Si SPM is enhanced by a resonant tip, which is resulted from the coupling between the guided mode and the radiation mode through symmetry breaking of the structure at near-normal incidence. The enhancement of the electric field intensity is increased 1939 times and the group velocity of light is decreased to 3.55 ×10-4c at resonance, and 99.3% absorption in graphene strips can be achieved by critical coupling at the incident angle of 2°. High absorption of the graphene strips can be maintained as the etching thickness, the strip width, and the period are altered. When this type of c-Si SPM with graphene strips is used in refractive index sensors, it shows excellent sensing properties due to its stable near-unity absorption.

TOTAL NUCLEAR-REACTION PROBABILITY OF 270 TO 390 N-14 IONS IN SI AND CSI

NARCIS (Netherlands)

WARNER, RE; CARPENTER, CL; FETTER, JM; WAITE, WF; WILSCHUT, HW; HOOGDUIN, JM

A magnetic spectrograph and position-sensitive detectors were used to measure the total nuclear reaction probability eta(R) for alpha + CsI at 116 MeV, N-14 + CsI at 265 and 385 MeV, and N-14 + Si at 271 and 390 MeV. From these eta(R)'s, average reaction cross sections sigma(R) were deduced for

Highly efficient holograms based on c-Si metasurfaces in the visible range.

Science.gov (United States)

Martins, Augusto; Li, Juntao; da Mota, Achiles F; Wang, Yin; Neto, Luiz G; do Carmo, João P; Teixeira, Fernando L; Martins, Emiliano R; Borges, Ben-Hur V

2018-04-16

This paper reports on the first hologram in transmission mode based on a c-Si metasurface in the visible range. The hologram shows high fidelity and high efficiency, with measured transmission and diffraction efficiencies of ~65% and ~40%, respectively. Although originally designed to achieve full phase control in the range [0-2π] at 532 nm, these holograms have also performed well at 444.9 nm and 635 nm. The high tolerance to both fabrication and wavelength variations demonstrate that holograms based on c-Si metasurfaces are quite attractive for diffractive optics applications, and particularly for full-color holograms.

Test Results of the ALICE-HMPID Detector Commissioning

CERN Document Server

Volpe, G

2008-01-01

The ALICE High Momentum Particle Identification Detector (HMPID) consists of seven identical proximity focusing RICH counters. It covers in total 11 m2, exploiting large area CsI photocathodes for Cherenkov light imaging. The detector is installed in the ALICE solenoid, ready for the data acquisition. By means of the Detector Control System, the Front-end (FEE) and the Readout (R/O) electronics, the MWPC high voltages, the cooling and the gas system have been tested. The HMPID module gas pressure, temperature, current and voltage trends have been monitored and archived in the ORACLE database. In this paper a comprehensive review on the test results is presented.

A review of radio-frequency photocathode electron sources

International Nuclear Information System (INIS)

Stovall, J.

1992-01-01

A review of this topic at the last conference in this series reported considerable progress in R and D programs aimed at producing high-current low-emittance electron beams using photocathode rf guns. At present at least 20 such projects are under way world wide and at least 6 photoinjectors are presently in operation. This paper reviews some of the choices that must be made in optimizing the design of the accelerating structure for a photoinjector based on the current state of knowledge. (Author) 5 refs., 9 figs., 3 tabs

The Communication Styles Inventory (CSI): a six-dimensional behavioral model of communication styles and its relation with personality

NARCIS (Netherlands)

de Vries, R.E.; Bakker-Pieper, A.; Konings, F.E.; Schouten, B.

2013-01-01

In this study, a six-dimensional model of communication styles is proposed and operationalized using the Communication Styles Inventory (CSI). The CSI distinguishes between six domain-level communicative behavior scales, Expressiveness, Preciseness, Verbal Aggressiveness, Questioningness,

Novel Control Strategy for VSI and CSI Active Filters and Comparing These Two Types of Filters

Directory of Open Access Journals (Sweden)

Gholam Reza Arab

2014-10-01

Full Text Available Recently to eliminate the harmonics and improve the power factor of the power networks, much attention has been attracted to active filters. The advantages of these filters are lower volume and their better compensating characteristics than the passive filters. In conventional sliding mode controllers, the source current waveform is fluctuated in near to zero values. In this paper, using a new sliding technique, lower Total Harmonic Distortion (THD in source current is obtained and the current waveform is improved. As well as, two novel control strategies for two types of active filters, VSI and CSI is proposed and then these two types of filters are compared to reduce THD value of source current.The proposed controlled strategies are simulated by MATLAB/Simulink. The Simulation results confirm that the proposed strategies reduce the THD of source current more than other strategies, and active filter based on CSI has a better performance than active filter based on VSI with a dead time area (for avoiding short circuit of the source in high powers.

Influence of boron vapor on transport behavior of deposited CsI during heating test simulating a BWR severe accident condition

Energy Technology Data Exchange (ETDEWEB)

Sato, Isamu, E-mail: sato.isamu@jaea.go.jp; Onishi, Takashi; Tanaka, Kosuke; Iwasaki, Maho; Koyama, Shin-ichi

2015-06-15

In order to evaluate influence of B on the release and transport of Cs and I during severe accidents, basic experiments have been performed on the interaction between deposited Cs/I compounds and vapor/aerosol B compounds. CsI and B{sub 2}O{sub 3} were utilized as a Cs/I compound and a B compound, respectively. Deposited CsI on the thermal gradient tube (TGT) at temperatures ranging from 423 K to 1023 K was reacted with vapor/aerosol B{sub 2}O{sub 3}, and then observed how it changed Cs/I deposition profiles. As a result, vapor/aerosol B{sub 2}O{sub 3} stripped a portion of deposited CsI within a temperature range from 830 K to 920 K to make gaseous CsBO{sub 2} and I{sub 2}. In addition, gaseous I{sub 2} was re-deposited at a temperature range from 530 K to 740 K, while CsBO{sub 2} travelled through the sampling tubes and filters without deposition. It is evident that B enables Cs compounds such as CsBO{sub 2} to transport Cs to the colder regions.

Generation of a femtosecond electron microbunch train from a photocathode using twofold Michelson interferometer

Directory of Open Access Journals (Sweden)

M. Shevelev

2017-10-01

Full Text Available The interest in producing ultrashort electron bunches has risen sharply among scientists working on the design of high-gradient wakefield accelerators. One attractive approach generating electron bunches is to illuminate a photocathode with a train of femtosecond laser pulses. In this paper we describe the design and testing of a laser system for an rf gun based on a commercial titanium-sapphire laser technology. The technology allows the production of four femtosecond laser pulses with a continuously variable pulse delay. We also use the designed system to demonstrate the experimental generation of an electron microbunch train obtained by illuminating a cesium-telluride semiconductor photocathode. We use conventional diagnostics to characterize the electron microbunches produced and confirm that it may be possible to control the main parameter of an electron microbunch train.

Generation of a femtosecond electron microbunch train from a photocathode using twofold Michelson interferometer

Science.gov (United States)

Shevelev, M.; Aryshev, A.; Terunuma, N.; Urakawa, J.

2017-10-01

The interest in producing ultrashort electron bunches has risen sharply among scientists working on the design of high-gradient wakefield accelerators. One attractive approach generating electron bunches is to illuminate a photocathode with a train of femtosecond laser pulses. In this paper we describe the design and testing of a laser system for an rf gun based on a commercial titanium-sapphire laser technology. The technology allows the production of four femtosecond laser pulses with a continuously variable pulse delay. We also use the designed system to demonstrate the experimental generation of an electron microbunch train obtained by illuminating a cesium-telluride semiconductor photocathode. We use conventional diagnostics to characterize the electron microbunches produced and confirm that it may be possible to control the main parameter of an electron microbunch train.

Uplink Contention-based CSI Feedback with Prioritized Layers for a Multi-Carrier System

DEFF Research Database (Denmark)

Kaneko, Megumi; Hayashi, Kazunori; Popovski, Petar

2012-01-01

, several works have considered contention-based CSI feedback in the UL control channel. We propose such a feedback scheme for a generic MC system, based on the idea of variable collision protection, where the probability that a feedback information experiences a collision depends on its importance......Optimized resource allocation of the Downlink (DL) in wireless systems utilizing Multi-Carrier (MC) transmission requires Channel State Information (CSI) feedback for each user/subchannel to the Base Station (BS), consuming a high amount of Uplink (UL) radio resources. To alleviate this problem...

A surfeit of science: The "CSI effect" and the media appropriation of the public understanding of science.

Science.gov (United States)

Cole, Simon A

2015-02-01

Over the past decade, popular media has promulgated claims that the television program CSI and its spinoffs and imitators have had a pernicious effect on the public understanding of forensic science, the so-called "CSI effect." This paper analyzes those media claims by documenting the ways in which the media claims that CSI "distorts" an imagined "reality." It shows that the media appropriated the analytic stance usually adopted by science advocates, portraying the CSI effect as a social problem in science communication. This appropriation was idiosyncratic in that it posited, as a social problem, a "surfeit" of knowledge and positive imagery about science, rather than the more familiar "deficits." In addition, the media simultaneously appropriated both "traditional" and "critical" PUS discourses. Despite this apparent contradiction, the paper concludes that, in both discourses, the media and its expert informants insist upon their hegemony over "the public" to articulate the "reality" of forensic science. © The Author(s) 2013.

Ab initio study of the effects of thin CsI coatings on the work function of graphite cathodes

Science.gov (United States)

Vlahos, Vasilios; Booske, John H.; Morgan, Dane

2007-10-01

Cesium-iodide (CsI)-coated graphite cathodes are promising electron sources for high power microwave generators, but the mechanism driving the improved emission is not well understood. Therefore, an ab initio modeling investigation on the effects of thin CsI coatings on graphite has been carried out. It is demonstrated that the CsI coatings reduce the work function of the system significantly through a mechanism of induced dipoles. The results suggest that work function modification is a major contribution to the improved emission seen when CsI coatings are applied to C.

Effect of non-magnetic intermediate layer on film structure, magnetic properties, and noise characteristics of FeCSi soft magnetic multilayers

International Nuclear Information System (INIS)

Kawano, Hiroyasu; Morikawa, Takeshi; Matsumoto, Koji; Shono, Keiji

2004-01-01

The film structures, magnetic properties, and noise characteristics of soft magnetic multilayers with alternately stacked FeCSi soft magnetic layers and non-magnetic intermediate layers were investigated. The FeCSi layers in an as-deposited multilayer with C or Ta intermediate layers had the same nano-sized fine crystalline grains and low media noise as an as-deposited FeCSi monolayer. Amorphous C intermediate layers suppressed the amplitude of spike noise especially well. In contrast, FeCSi layers in an as-deposited multilayer with Cr or Ti intermediate layers were composed of coarse crystalline grains, which increased the media noise. The crystallographic match at the interface between the layers in a multilayer could explain these phenomena. The similarity of the atomic arrangement at the interface between layers and the crystallographic match of less than a few percent for the distance between atoms crystallized FeCSi layers with nano-sized fine crystalline grains into ones with coarse crystalline grains during deposition

Minimax robust power split in AF relays based on uncertain long-term CSI

KAUST Repository

Nisar, Muhammad Danish

2011-09-01

An optimal power control among source and relay nodes in presence of channel state information (CSI) is vital for an efficient amplify and forward (AF) based cooperative communication system. In this work, we study the optimal power split (power control) between the source and relay node in presence of an uncertainty in the CSI. The prime contribution is to solve the problem based on an uncertain long-term knowledge of both the first and second hop CSI (requiring less frequent updates), and under an aggregate network-level power constraint. We employ the minimax optimization methodology to arrive at the minimax robust optimal power split, that offers the best possible guarantee on the end-to-end signal to noise ratio (SNR). The derived closed form analytical expressions admit simple intuitive interpretations and are easy to implement in real-world AF relaying systems. Numerical results confirm the advantages of incorporating the presence of uncertainty into the optimization problem, and demonstrate the usefulness of the proposed minimax robust optimal power split. © 2011 IEEE.

3D ZnIn2S4 nanosheet/TiO2 nanowire arrays and their efficient photocathodic protection for 304 stainless steel

Science.gov (United States)

Sun, Wenxia; Wei, Na; Cui, Hongzhi; Lin, Yuan; Wang, Xinzhen; Tian, Jian; Li, Jian; Wen, Jing

2018-03-01

A well-designed heterostructure engineered ZnIn2S4 nanosheet/TiO2 nanowire arrays photoanode is investigated for photocathodic protection. The ZnIn2S4 nanosheets are distributed uniformly on the surface of the TiO2 nanowire by a hydrothermal method. The stem-and-leaf-like ZnIn2S4 nanosheet/TiO2 nanowire arrays exhibit excellent photoelectrochemical properties, owing to the energy band structure and large surface area. A maximum photocurrent density of 2 mA cm-2 is achieved for the ZnIn2S4 nanosheet/TiO2 nanowire composite film for a 6 h reaction time under white illumination. Moreover, the potential of the 304 stainless steel coupled with the composite film immediately shifts negatively to -1.17 V (vs. SCE), which is significantly lower than the corrosion potential (-0.201 V vs. SCE). Thus, the composite film offers a superior photocathodic protection for stainless steel against corrosion by a NaCl solution. This study provides a promising approach for the design and synthesis of composite films with enhanced photoelectrochemical performance.

Contrast source inversion (CSI) method to cross-hole radio-imaging (RIM) data - Part 2: A complex synthetic example and a case study

Science.gov (United States)

Li, Yongxing; Smith, Richard S.

2018-03-01

We present two examples of using the contrast source inversion (CSI) method to invert synthetic radio-imaging (RIM) data and field data. The synthetic model has two isolated conductors (one perfect conductor and one moderate conductor) embedded in a layered background. After inversion, we can identify the two conductors on the inverted image. The shape of the perfect conductor is better resolved than the shape of the moderate conductor. The inverted conductivity values of the two conductors are approximately the same, which demonstrates that the conductivity values cannot be correctly interpreted from the CSI results. The boundaries and the tilts of the upper and the lower conductive layers on the background can also be inferred from the results, but the centre parts of conductive layers in the inversion results are more conductive than the parts close to the boreholes. We used the straight-ray tomographic imaging method and the CSI method to invert the RIM field data collected using the FARA system between two boreholes in a mining area in Sudbury, Canada. The RIM data include the amplitude and the phase data collected using three frequencies: 312.5 kHz, 625 kHz and 1250 kHz. The data close to the ground surface have high amplitude values and complicated phase fluctuations, which are inferred to be contaminated by the reflected or refracted electromagnetic (EM) fields from the ground surface, and are removed for all frequencies. Higher-frequency EM waves attenuate more quickly in the subsurface environment, and the locations where the measurements are dominated by noise are also removed. When the data are interpreted with the straight-ray method, the images differ substantially for different frequencies. In addition, there are some unexpected features in the images, which are difficult to interpret. Compared with the straight-ray imaging results, the inversion results with the CSI method are more consistent for different frequencies. On the basis of what we learnt

Intense electron beams from GaAs photocathodes as a tool for molecular and atomic physics

International Nuclear Information System (INIS)

Krantz, Claude

2009-01-01

We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at usable cathode lifetimes of 24 h or more. The benefits of the cold electron beam with respect to its application to electron cooling and electron-ion recombination experiments are discussed. Benchmark experiments demonstrate the superior cooling force and energy resolution of the photoelectron beam compared to its thermionic counterparts. The long period of operation allowed to study the long-time behaviour of the GaAs samples during multiple usage cycles at the Electron Target and repeated in-vacuum surface cleaning by atomic hydrogen exposure. An electron emission spectroscopy setup has been implemented at the photocathode preparation chamber of the Electron Target. Among others, this new facility opened the way to a novel application of GaAs (Cs) photocathodes as robust, ultraviolet-driven electron emitters. Based on this principle, a prototype of an electron gun, designed for implementation at the HITRAP setup at GSI, has been built and taken into operation successfully. (orig.)

Intense electron beams from GaAs photocathodes as a tool for molecular and atomic physics

Energy Technology Data Exchange (ETDEWEB)

Krantz, Claude

2009-10-28

We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at usable cathode lifetimes of 24 h or more. The benefits of the cold electron beam with respect to its application to electron cooling and electron-ion recombination experiments are discussed. Benchmark experiments demonstrate the superior cooling force and energy resolution of the photoelectron beam compared to its thermionic counterparts. The long period of operation allowed to study the long-time behaviour of the GaAs samples during multiple usage cycles at the Electron Target and repeated in-vacuum surface cleaning by atomic hydrogen exposure. An electron emission spectroscopy setup has been implemented at the photocathode preparation chamber of the Electron Target. Among others, this new facility opened the way to a novel application of GaAs (Cs) photocathodes as robust, ultraviolet-driven electron emitters. Based on this principle, a prototype of an electron gun, designed for implementation at the HITRAP setup at GSI, has been built and taken into operation successfully. (orig.)

Corporate Social Irresponsibility (CSI): Everything you say, or not say, can be held against you

OpenAIRE

Jonsson, Veronica; Stéen, Josefine

2016-01-01

Corporate social irresponsibility (CSI), as an opposite of corporate social responsibility (CSR), refers to corporation’s failure to act responsibly. To address the actions connected to CSR and CSI, corporations need to overcome the challenges of communicating to their stakeholders and to be transparent. Stakeholders have become more skeptical regarding if the corporations are actually living up to the communicated standards. In other words, if corporations are ‘doing as they say’ and if they...

Study on the effect of deposition rate and concentration of Eu on the fluorescent lifetime of CsI: Tl thin film

Energy Technology Data Exchange (ETDEWEB)

Xie, Yijun; Guo, Lina [University of Electronic Science and Technology of China, State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, Chengdu 610054 (China); Liu, Shuang, E-mail: shuangliu@uestc.edu.cn [University of Electronic Science and Technology of China, State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, Chengdu 610054 (China); Wang, Qianfeng; Zhang, Shangjian; Liu, Yong [University of Electronic Science and Technology of China, State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, Chengdu 610054 (China); Zhong, Zhiyong [University of Electronic Science and Technology of China, State Key Laboratory of Electronic Thin Films and Integrated Devices, Chengdu 610054 (China)

2017-06-21

Although there are many new scintillators being developed recently, CsI: Tl is still very efficient among them. The fluorescent lifetime is a very important parameter of CsI: Tl thin film and two series of experiments have been conducted to learn about it. Our experiments, however, have demonstrated that the deposition rate and the codoping of Eu{sup 2+} will significantly influence its fluorescent lifetime. In order to increase the efficiency of the imaging system, we intend to obtain a higher fluorescent lifetime for CsI: Tl thin film by controlling these two conditions. - Highlights: • We used vacuum vapor deposition method to grow the high-quality thin films. • The relationship between the deposition rate and the fluorescent lifetime of CsI: Tl thin film was tested. • Concentration of Eu on fluorescent lifetime of the CsI: Tl thin film was studied.

Performance of a DC GaAs photocathode gun for the Jefferson lab FEL

CERN Document Server

Siggins, T; Bohn, C L; Bullard, D; Douglas, D; Grippo, A; Gubeli, J; Krafft, G A; Yunn, B

2001-01-01

The performance of the 320 kV DC photocathode gun has met the design specifications for the 1 kW IR Demo FEL at Jefferson Lab. This gun has shown the ability to deliver high average current beam with outstanding lifetimes. The GaAs photocathode has delivered 135 pC per bunch, at a bunch repetition rate of 37.425 MHz, corresponding to 5 mA average CW current. In a recent cathode lifetime measurement, 20 h of CW beam was delivered with an average current of 3.1 mA and 211 C of total charge from a 0.283 cm sup 2 illuminated spot. The cathode showed a 1/e lifetime of 58 h and a 1/e extracted charge lifetime of 618 C. We have achieved quantum efficiencies of 5% from a GaAs wafer that has been in service for 13 months delivering in excess 2400 C with only three activation cycles.

Heat load of a P-doped GaAs photocathode in SRF electron gun

International Nuclear Information System (INIS)

Wang, E.; Ben-Zvi, I.; Kewisch, J.; Burrill, A.; Rao, T.; Wu, Q.; Jain, A.; Gupta, R.; Holmes, D.

2010-01-01

Many efforts were made over the last decades to develop a better polarized electron source for the high energy physics. Several laboratories operate DC guns with the Gallium-Arsenide photo-cathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved using a Superconducting RF electron gun, which delivers beams of higher brightness than DC guns does, because the field gradient at the cathode is higher. SRF guns with metal cathodes and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since the cathode will be normal conducting, the problem about the heat load stemming from the cathode arises. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and the verification by measuring the quality factor of the gun with and without cathode.

Photocurrent Enhancement by a Rapid Thermal Treatment of Nanodisk-Shaped SnS Photocathodes.

Science.gov (United States)

Patel, Malkeshkumar; Kumar, Mohit; Kim, Joondong; Kim, Yu Kwon

2017-12-21

Photocathodes made from the earth-abundant, ecofriendly mineral tin monosulfide (SnS) can be promising candidates for p/n-type photoelectrochemical cells because they meet the strict requirements of energy band edges for each individual photoelectrode. Herein we fabricated SnS-based cell that exhibited a prolonged photocurrent for 3 h at -0.3 V vs the reversible hydrogen electrode (RHE) in a 0.1 M HCl electrolyte. An enhancement of the cathodic photocurrent from 2 to 6 mA cm -2 is observed through a rapid thermal treatment. Mott-Schottky analysis of SnS samples revealed an anodic shift of 0.7 V in the flat band potential under light illumination. Incident photon-to-current conversion efficiency (IPCE) analysis indicates that an efficient charge transfer appropriate for solar hydrogen generation occurs at the -0.3 V vs RHE potential. This work shows that SnS is a promising material for photocathode in PEC cells and its performance can be enhanced via simple postannealing.

Picosecond electron bunches from GaAs/GaAsP strained superlattice photocathode

International Nuclear Information System (INIS)

Jin, Xiuguang; Matsuba, Shunya; Honda, Yosuke; Miyajima, Tsukasa; Yamamoto, Masahiro; Utiyama, Takashi; Takeda, Yoshikazu

2013-01-01

GaAs/GaAsP strained superlattices are excellent candidates for use as spin-polarized electron sources. In the present study, picosecond electron bunches were successfully generated from such a superlattice photocathode. However, electron transport in the superlattice was much slower than in bulk GaAs. Transmission electron microscopy observations revealed that a small amount of variations in the uniformity of the layers was present in the superlattice. These variations lead to fluctuations in the superlattice mini-band structure and can affect electron transport. Thus, it is expected that if the periodicity of the superlattice can be improved, much faster electron bunches can be produced. - Highlights: • GaAs/GaAsP strained superlattices are excellent candidates for spin-polarized electron beam. • Pulse spin-polarized electron beam is required for investigating the magnetic domain change. • Picosecond electron bunches were achieved from GaAs/GaAsP superlattice photocathode. • TEM observation revealed a small disorder of superlattice layers. • Improvement of superlattice periodicity can achieve much faster electron bunches

Novel Robust Optimization and Power Allocation of Time Reversal-MIMO-UWB Systems in an Imperfect CSI

Directory of Open Access Journals (Sweden)

Sajjad Alizadeh

2013-03-01

Full Text Available Time Reversal (TR technique is an attractive solution for a scenario where the transmission system employs low complexity receivers with multiple antennas at both transmitter and receiver sides. The TR technique can be combined with a high data rate MIMO-UWB system as TR-MIMO-UWB system. In spite of TR's good performance in MIMO-UWB systems, it suffers from performance degradation in an imperfect Channel State Information (CSI case. In this paper, at first a robust TR pre-filter is designed together with a MMSE equalizer in TR-MIMO-UWB system where is robust against channel imperfection conditions. We show that the robust pre-filter optimization technique, considerably improves the BER performance of TR-MIMO-UWB system in imperfect CSI, where temporal focusing of the TR technique is kept, especially for high SNR values. Then, in order to improve the system performance more than ever, a power loading scheme is developed by minimizing the average symbol error rate in an imperfect CSI. Numerical and simulation results are presented to confirm the performance advantage attained by the proposed robust optimization and power loading in an imperfect CSI scenario.

Examination of the "CSI Effect" on Perceptions of Scientific and Testimonial Evidence in a Hong Kong Chinese Sample.

Science.gov (United States)

Hui, Cora Y T; Lo, T Wing

2017-05-01

Television is a powerful medium through which to convey information and messages to the public. The recent proliferation of forensic science and criminal justice information throughout all forms of media, coupled with raised expectations toward forensic evidence, has led some to suspect that a "CSI effect" ( Crime Scene Investigation effect) is taking place. The present study contributes to the literature addressing the CSI effect in two ways. First, it examines whether the CSI effect exists in the Chinese population of Hong Kong. Second, using a mock-jury paradigm, it empirically examines a more integrative perspective of the CSI effect. It was found that, although the amount of media coverage involving forensic evidence does influence participants' perception of legal evidence to some degree, such a perception does not affect participants' legal decision making. Viewers of forensic dramas were not more likely to convict the defendant when forensic evidence was presented and not less likely to convict when only testimonial evidence was presented. The only significant predictor of the defendant's culpability when scientific evidence was presented was participants' ratings of the reliability of scientific evidence. Results from the present study lend no support to the existence of the CSI effect in Hong Kong.

Improved Electron Yield and Spin-Polarization from III-V Photocathodes via Bias Enhanced Carrier Drift: Final Report

International Nuclear Information System (INIS)

Mulhollan, Gregory A.

2006-01-01

In this DOE STTR program, Saxet Surface Science, with the Stanford Linear Accelerator Center as partner, designed, built and tested photocathode structures such that optimal drift-enhanced spin-polarization from GaAs based photoemitters was achieved with minimal bias supply requirements. The forward bias surface grid composition was optimized for maximum polarization and yield, together with other construction parameters including doping profile. This program has culminated in a cathode bias structure affording increased electron spin polarization when applied to III-V based photocathodes. The optimized bias structure has been incorporated into a cathode mounting and biasing design for use in a polarized electron gun.

Opportunistic Energy-Aware Amplify-and-Forward Cooperative Systems with Imperfect CSI

KAUST Repository

Amin, Osama; Bedeer, Ebrahim; Ahmed, Mohamed Hossam; Dobre, Octavia; Alouini, Mohamed-Slim

2015-01-01

an energyefficient relay assisted communication system based on estimated channel state information (CSI). It employs amplify-andforward relaying and switches between different communication schemes, which are known as direct-transmission, two-hop and cooperative

SU-E-I-11: Cascaded Linear System Model for Columnar CsI Flat Panel Imagers with Depth Dependent Gain and Blur

International Nuclear Information System (INIS)

Peng, B; Lubinsky, A; Zheng, H; Zhao, W; Teymurazyan, A

2014-01-01

Purpose: To implement a depth dependent gain and blur cascaded linear system model (CLSM) for optimizing columnar structured CsI indirect conversion flat panel imager (FPI) for advanced imaging applications. Methods: For experimental validation, depth dependent escape efficiency, e(z), was extracted from PHS measurement of different CsI scintillators (thickness, substrate and light output). The inherent MTF and DQE of CsI was measured using high resolution CMOS sensor. For CLSM, e(z) and the depth dependent MTF(f,z), were estimated using Monte Carlo simulation (Geant4) of optical photon transport through columnar CsI. Previous work showed that Monte Carlo simulation for CsI was hindered by the non-ideality of its columnar structure. In the present work we allowed variation in columnar width with depth, and assumed diffusive reflective backing and columns. Monte Carlo simulation was performed using an optical point source placed at different depth of the CsI layer, from which MTF(z,f) and e(z) were computed. The resulting e(z) with excellent matching with experimental measurements were then applied to the CLSM, Monte Carlo simulation was repeated until the modeled MTF, DQE(f) also match experimental measurement. Results: For a 150 micron FOS HL type CsI, e(z) varies between 0.56 to 0.45, and the MTF at 14 cycles/mm varies between 62.1% to 3.9%, from the front to the back of the scintillator. The overall MTF and DQE(f) at all frequencies are in excellent agreement with experimental measurements at all frequencies. Conclusion: We have developed a CLSM for columnar CsI scintillators with depth dependent gain and MTF, which were estimated from Monte Carlo simulation with novel optical simulation settings. Preliminary results showed excellent agreement between simulation results and experimental measurements. Future work is aimed at extending this approach to optimize CsI screen optic design and sensor structure for achieving higher DQE(f) in cone-beam CT, which uses

Generation of CsI cluster ions for mass calibration in matrix-assisted laser desorption/ionization mass spectrometry

NARCIS (Netherlands)

Lou, X.; Dongen, van J.L.J.; Meijer, E.W.

2010-01-01

A simple method was developed for the generation of cesium iodide (CsI) cluster ions up to m/z over 20,000 in matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Calibration ions in both positive and negative ion modes can readily be generated from a single MALDI spot of CsI(3)

Comparison of blue-green response between transmission-mode GaAsP- and GaAs-based photocathodes grown by molecular beam epitaxy

Science.gov (United States)

Gang-Cheng, Jiao; Zheng-Tang, Liu; Hui, Guo; Yi-Jun, Zhang

2016-04-01

In order to develop the photodetector for effective blue-green response, the 18-mm-diameter vacuum image tube combined with the transmission-mode Al0.7Ga0.3As0.9 P 0.1/GaAs0.9 P 0.1 photocathode grown by molecular beam epitaxy is tentatively fabricated. A comparison of photoelectric property, spectral characteristic and performance parameter between the transmission-mode GaAsP-based and blue-extended GaAs-based photocathodes shows that the GaAsP-based photocathode possesses better absorption and higher quantum efficiency in the blue-green waveband, combined with a larger surface electron escape probability. Especially, the quantum efficiency at 532 nm for the GaAsP-based photocathode achieves as high as 59%, nearly twice that for the blue-extended GaAs-based one, which would be more conducive to the underwater range-gated imaging based on laser illumination. Moreover, the simulation results show that the favorable blue-green response can be achieved by optimizing the emission-layer thickness in a range of 0.4 μm-0.6 μm. Project supported by the National Natural Science Foundation of China (Grant No. 61301023) and the Science and Technology on Low-Light-Level Night Vision Laboratory Foundation, China (Grant No. BJ2014001).

Psychometric Evaluation of a Coping Strategies Inventory Short-Form (CSI-SF in the Jackson Heart Study Cohort

Directory of Open Access Journals (Sweden)

Herman Taylor

2007-12-01

Full Text Available This study sought to establish the psychometric properties of a Coping Strategies Inventory Short Form (CSISF by examining coping skills in the Jackson Heart Study cohort. We used exploratory and confirmatory factor analysis, Pearson’s correlation, and Cronbach Alpha to examine reliability and validity in the CSI-SF that solicited responses from 5302 African American men and women between the ages of 35 and 84. One item was dropped from the 16-item CSI-SF, making it a 15-item survey. No significant effects were found for age and gender, strengthening the generalizability of the CSI-SF. The internal consistency reliability analysis revealed reliability between alpha = 0.58-0.72 for all of the scales, and all of the fit indices used to examine the CSI-SF provided support for its use as an adequate measure of coping. This study provides empirical support for utilizing this instrument in future efforts to understand the role of coping in moderating health outcomes.

Integration of Transients in Axisymmetrical Cavities for Accelerators: Formulation and applications to BNL Photocathode Gun

International Nuclear Information System (INIS)

Parsa, Z.; Serafini, L.

1992-04-01

This note provides a sketch of the formalism used for the Integration of Transients in Axisymmetrical Cavities for Accelerators, (ITACA). Application to study the BNL Photocathode Gun via the code ITACA is also included

CSI flight experiment projects of the Naval Research Laboratory

Science.gov (United States)

Fisher, Shalom

1993-02-01

The Naval Research Laboratory (NRL) is involved in an active program of CSI flight experiments. The first CSI flight experiment of the Naval Research Laboratory, the Low Power Atmospheric Compensation Experiment (LACE) dynamics experiment, has successfully measured vibrations of an orbiting satellite with a ground-based laser radar. The observations, made on January 7, 8 and 10, 1991, represent the first ever measurements of this type. In the tests, a narrowband heterodyne CO2 laser radar, operating at a wavelength of 10.6 microns, detected vibration induced differential-Doppler signatures of the LACE satellite. Power spectral densities of forced oscillations and modal frequencies and damping rates of free-damped vibrations were obtained and compared with finite element structural models of the LACE system. Another manifested flight experiment is the Advanced Controls Technology Experiment (ACTEX) designed to demonstrate active and passive damping with piezo-electric (PZT) sensors and actuators. This experiment was developed under the management of the Air Force Phillips Laboratory with integration of the experiment at NRL. It is to ride as a secondary, or 'piggyback,' experiment on a future Navy satellite.

On some regularities of metal oxide solubility in molten CsI at T = 973 K

Energy Technology Data Exchange (ETDEWEB)

Cherginets, V.L., E-mail: v_cherginets@ukr.net [Institute for Scintillation Materials, National Academy of Sciences of Ukraine, Lenin Avenue, 60, Kharkov 61001 (Ukraine); National Technical University ' Kharkiv Polytechnical Institute' , 21 Frunze St., 61002 Kharkov (Ukraine); Rebrova, T.P.; Datsko, Yu.N.; Shtitelman, V.A. [Institute for Scintillation Materials, National Academy of Sciences of Ukraine, Lenin Avenue, 60, Kharkov 61001 (Ukraine); Bryleva, E.Yu. [State Scientific Organization STC ' Institute for Single Crystals' , National Academy of Sciences of Ukraine, Lenin Avenue, 60, Kharkov 61001 (Ukraine)

2011-08-15

Highlights: > CdO, ZnO, NiO, and EuO are insoluble in CsI melt at 973 K. > The oxide solubilities are lower than those in chloride melts. > The oxide solubilities reduce with the cation radius. > ZnO, NiO, and EuO are suitable for scavenging CsO from oxide ion traces. - Abstract: Solubility products of CdO (pK{sub s,CdO} = 6.80 {+-} 0.2), ZnO (pK{sub s,ZnO} = 10.0 {+-} 0.5), NiO (pK{sub s,NiO} = 11.2 {+-} 0.2) and EuO (pK{sub s,EuO} = 13.1 {+-} 0.2) in molten CsI at T = 973 K are determined by potentiometric titration of (0.02 to 0.03) mol . kg{sup -1} solutions of the corresponding metal chlorides by strong base (KOH) using a membrane oxygen electrode Pt(O{sub 2})|ZrO{sub 2}(Y{sub 2}O{sub 3}) as an indicator. On the basis of pK{sub s,MeO} values, all the oxides studied are referred to practically insoluble in molten CsI. The values of the oxide solubility in CsI melt are lower than the corresponding values in molten alkali metal chlorides. This can be explained by 'softer' basic properties of I{sup -} as compared with Cl{sup -} in the frames of the Pearson 'hard' and 'soft' acid-base concept. In the oxide samples studied, the values of the solubility fall with the decreasing cation radius. The correlation between pK{sub s,MeO} and the polarizing action by Goldshmidt (Zr{sub Me{sup 2+}}{sup -2}) of the cation is practically linear and may be proposed for estimation of the solubility of s- and d- element oxides in molten CsI on the basis of their cation radii.

High voltage switch triggered by a laser-photocathode subsystem

Science.gov (United States)

Chen, Ping; Lundquist, Martin L.; Yu, David U. L.

2013-01-08

A spark gap switch for controlling the output of a high voltage pulse from a high voltage source, for example, a capacitor bank or a pulse forming network, to an external load such as a high gradient electron gun, laser, pulsed power accelerator or wide band radar. The combination of a UV laser and a high vacuum quartz cell, in which a photocathode and an anode are installed, is utilized as triggering devices to switch the spark gap from a non-conducting state to a conducting state with low delay and low jitter.

Lasertron, a pulsed RF-source using laser triggered photocathode

International Nuclear Information System (INIS)

Yoshioka, Masakazu.

1988-12-01

A new pulsed RF-source, 'Lasertron', are being developed as a possible RF-power source for future electron-positron linear colliders. In a series of systematic study, a prototype lasertron has been fabricated and tested. A peak power of 80 kW is attained at 2.856 GHz RF-frequency in 1-μs time duration. This paper describes the experimental results of the lasertron including the developments of the photocathode and the laser system. Test results are compared with the analysis of beam dynamics in the lasertron. (author)

Unbiased, complete solar charging of a neutral flow battery by a single Si photocathode

DEFF Research Database (Denmark)

Wedege, Kristina; Bae, Dowon; Dražević, Emil

2018-01-01

Solar redox flow batteries have attracted attention as a possible integrated technology for simultaneous conversion and storage of solar energy. In this work, we review current efforts to design aqueous solar flow batteries in terms of battery electrolyte capacity, solar conversion efficiency...... and depth of solar charge. From a materials cost and design perspective, a simple, cost-efficient, aqueous solar redox flow battery will most likely incorporate only one semiconductor, and we demonstrate here a system where a single photocathode is accurately matched to the redox couples to allow...... for a complete solar charge. The single TiO2 protected Si photocathode with a catalytic Pt layer can fully solar charge a neutral TEMPO-sulfate/ferricyanide battery with a cell voltage of 0.35 V. An unbiased solar conversion efficiency of 1.6% is obtained and this system represents a new strategy in solar RFBs...

The High Momentum Particle IDentification (HMPID) detector PID performance and its contribution to the ALICE physics program

Science.gov (United States)

Volpe, Giacomo; ALICE Collaboration

2017-12-01

The ALICE apparatus is dedicated to study the properties of strongly interacting matter under extremely high temperature and energy density conditions. For this, enhanced particle identification (PID) capabilities are required. Among the PID ALICE detectors, the ALICE-HMPID (High Momentum Particle IDentification) detector is devoted to the identification of charged hadrons, exploiting the Cherenkov effect. It consists of seven identical RICH modules, with liquid C6F14 as Cherenkov radiator (n ≈1.298 at λ=175 nm). Photon and charged particle detection is performed by a MWPC, coupled with a pad segmented CsI coated photo-cathode. The total CsI active area is 10.3 m2. The HMPID provides 3 sigma separation for pions and kaons up to pT = 3 GeV / c and for kaons and (anti-)protons up to pT = 5 GeV / c . A review of the HMPID PID performance, in particular in the challenging central Pb-Pb collisions, and its contribution to the ALICE physics program, using the LHC RUN1 (2010-2013) and RUN2 (2015) data, are presented.

Use of the Central Sensitization Inventory (CSI) as a treatment outcome measure for patients with chronic spinal pain disorder in a functional restoration program.

Science.gov (United States)

Neblett, Randy; Hartzell, Meredith M; Williams, Mark; Bevers, Kelley R; Mayer, Tom G; Gatchel, Robert J

2017-12-01

The Central Sensitization Inventory (CSI) is a valid and reliable patient-reported instrument designed to identify patients whose presenting symptoms may be related to central sensitization (CS). Part A of the CSI measures a full array of 25 somatic and emotional symptoms associated with CS, and Part B asks if patients have previously been diagnosed with one or more specific central sensitivity syndromes (CSSs) and related disorders. The CSI has previously been validated in a group of patients with chronic pain who were screened by a trained psychiatrist for specific CSS diagnoses. It is currently unknown if the CSI can be a useful treatment-outcome assessment tool for patients with chronic spinal pain disorder (CSPD) who are not screened for comorbid CSSs. It is known, however, that previous studies have identified CS-related symptoms, and comorbid CSSs, in subsets of patients with CSPDs. Studies have also shown that CS-related symptoms can be influenced by cognitive and psychosocial factors, including abuse history in both childhood and adulthood, sleep disturbance, catastrophic and fear-avoidant cognitions, and symptoms of depression and anxiety. This study aimed to evaluate CSI scores, and their associations with other clinically relevant psychosocial variables, in a cohort of patients with CSPD who entered and completed a functional restoration program. A retrospective study of prospectively collected data from a cohort study of patients with CSPD, who completed the CSI at admission to, and discharge from, an interdisciplinary function restoration program (FRP) was carried out. A cohort of 763 patients with CSPD comprised the study sample. Clinical interviews evaluated mood disorders and abuse history. A series of self-reported measures evaluated comorbid psychosocial symptoms, including pain intensity, pain-related anxiety, depressive symptoms, somatization symptoms, perceived disability, and sleep disturbance, at FRP admission and discharge. Patients were

Theoretical study of the Cs isotope exchange reaction of CsI + Cs' → Cs + ICs' (Contract research)

International Nuclear Information System (INIS)

Kobayashi, Takanori; Hashimoto, Masashi; Yokoyama, Keiichi

2015-12-01

To discuss the exchange reaction of Cs isotope by CsI + Cs' → Cs + ICs', the structure and chemical properties of Cs 2 I intermediate and potential energy surface of the entrance reaction are calculated using M06/def2-TZVPPD density functional calculation. The calculation shows that the reaction to the intermediate has no barrier and the two Cs-I bonds of Cs 2 I are chemically equivalent. These results suggest that the rate of the Cs exchange reaction of CsI + Cs' → Cs + ICs' is as high as the collision rate. (author)

Performance Analysis of Communications under Energy Harvesting Constraints with noisy CSI

KAUST Repository

Znaidi, Mohamed Ridha; Rezki, Zouheir; Tembine, Hamidou; Alouini, Mohamed-Slim

2016-01-01

to environmental changes. In this work, we consider the problem of power allocation taking into account the energy arrivals over time and the degree of channel state information (CSI) available at the transmitter, to maximize the throughput. Differently from

Novel p-n heterojunction copper phosphide/cuprous oxide photocathode for solar hydrogen production.

Science.gov (United States)

Chen, Ying-Chu; Chen, Zhong-Bo; Hsu, Yu-Kuei

2018-08-01

A Copper phosphide (Cu 3 P) micro-rod (MR) array, with coverage by an n-Cu 2 O thin layer by electrodeposition as a photocathode, has been directly fabricated on copper foil via simple electro-oxidation and phosphidation for photoelectrochemical (PEC) hydrogen production. The morphology, structure, and composition of the Cu 3 P/Cu 2 O heterostructure are systematically analyzed using a scanning electron microscope (SEM), X-ray diffraction and X-ray photoelectron spectra. The PEC measurements corroborate that the p-Cu 3 P/n-Cu 2 O heterostructural photocathode illustrates efficient charge separation and low charge transfer resistance to achieve the highest photocurrent of 430 μA cm -2 that is greater than other transition metal phosphide materials. In addition, a detailed energy diagram of the p-Cu 3 P/n-Cu 2 O heterostructure was investigated using Mott-Schottky analysis. Our study paves the way to explore phosphide-based materials in a new class for solar energy applications. Copyright © 2018 Elsevier Inc. All rights reserved.

Trojan horse underdense plasma photocathode acceleration

Energy Technology Data Exchange (ETDEWEB)

Karger, Oliver [Hamburg Univ. (Germany). Inst. fuer Experimentalphysik; DESY, FLA Arbeitsbereich Beschleunigerphysik, Hamburg (Germany); Koenigstein, Thomas; Pretzler, Georg [Duesseldorf Univ. (Germany). Inst. fuer Laser- und Plasmaphysik; Rosenzweig, James B. [California Univ., Los Angeles, CA (United States). Dept. of Physics and Astronomy; Hidding, Bernhard [Hamburg Univ. (Germany). Inst. fuer Experimentalphysik; DESY, FLA Arbeitsbereich Beschleunigerphysik, Hamburg (Germany); California Univ., Los Angeles, CA (United States). Dept. of Physics and Astronomy

2013-07-01

Relativistic electron beams with small emittance and size are needed for advanced applications such as free electron lasers (FEL) and other coherent light sources in the X-ray regime. Present laser plasma acceleration schemes are hardly able to provide electron beams of sufficient quality on a stable level. The concept of underdense plasma photocathode acceleration uses a beam-driven plasma wave in a two component gas mixture consisting a low ionisation threshold medium (LIT) and a high ionisation threshold medium (HIT) and a low-energy laser pulse. Shapeable electron bunches with sub-fs-length and unprecedented normalized emittance down to 10{sup -9} m rad can be produced. Based on this method, laboratory-sized-experimental setups may enable performance much better than today's conventional coherent hard X-ray sources. The presentation discusses the basic concept, shows recent numero-analytical results and the R and D towards experimental realization.

Modified Grid-Connected CSI for Hybrid PV/Wind Power Generation System

Directory of Open Access Journals (Sweden)

D. Amorndechaphon

2012-01-01

Full Text Available The principle of a power conditioning unit for hybrid PV/wind power generation system is proposed. The proposed power conditioner is based on the current source inverter (CSI topology. All energy sources are connected in parallel with a DC-bus through the modified wave-shaping circuits. To achieve the unity power factor at the utility grid, the DC-link current can be controlled via the wave-shaping circuits with the sinusoidal PWM scheme. In this work, the carrier-based PWM scheme is also proposed to minimize the utility current THD. The power rating of the proposed system can be increased by connecting more PV/wind modules through their wave-shaping circuits in parallel with the other modules. The details of the operating principles, the system configurations, and the design considerations are described. The effectiveness of the proposed CSI is demonstrated by simulation results.

Characterization of quantum well structures using a photocathode electron microscope

Science.gov (United States)

Spencer, Michael G.; Scott, Craig J.

1989-01-01

Present day integrated circuits pose a challenge to conventional electronic and mechanical test methods. Feature sizes in the submicron and nanometric regime require radical approaches in order to facilitate electrical contact to circuits and devices being tested. In addition, microwave operating frequencies require careful attention to distributed effects when considering the electrical signal paths within and external to the device under test. An alternative testing approach which combines the best of electrical and optical time domain testing is presented, namely photocathode electron microscope quantitative voltage contrast (PEMQVC).

Chemical Shift Imaging (CSI) by precise object displacement

OpenAIRE

Leclerc, Sebastien; Trausch, Gregory; Cordier, Benoit; Grandclaude, Denis; Retournard, Alain; Fraissard, Jacques; Canet, Daniel

2006-01-01

International audience; A mechanical device (NMR lift) has been built for displacing vertically an object (typically a NMR sample tube) inside the NMR probe with an accuracy of 1 Μm. A series of single pulse experiments are performed for incremented vertical positions of the sample. With a sufficiently spatially selective rf field, one obtains chemical shift information along the displacement direction (one dimensional Chemical Shift Imaging – CSI). Knowing the vertical radio-frequency (rf) f...

Hierarchical Cu2O foam/g-C3N4 photocathode for photoelectrochemical hydrogen production

Science.gov (United States)

Ma, Xinzhou; Zhang, Jingtao; Wang, Biao; Li, Qiuguo; Chu, Sheng

2018-01-01

Solar photoelectrochemical (PEC) hydrogen production is a promising way for solving energy and environment problems. Earth-abundant Cu2O is a potential light absorber for PEC hydrogen production. In this article, hierarchical porous Cu2O foams are prepared by thermal oxidation of the electrochemically deposited Cu foams. PEC performances of the Cu2O foams are systematically studied and discussed. Benefiting from their higher light harvesting and more efficient charge separation, the Cu2O foams demonstrate significantly enhanced photocurrents and photostability compared to their film counterparts. Moreover, by integrating g-C3N4, hierarchical Cu2O foam/g-C3N4 composites are prepared with further improved photocurrent and photostability, appearing to be potential photocathodes for solar PEC hydrogen production. This study may provide a new and useful insight for the development of Cu2O-based photocathodes for PEC hydrogen production.

Atomic-layer deposited passivation schemes for c-Si solar cells

NARCIS (Netherlands)

van de Loo, B.W.H.; Macco, B.; Melskens, J.; Verheijen, M.A.; Kessels, W.M.M.E.

2016-01-01

A review of recent developments in the field of passivation of c-Si surfaces is presented, with a particular focus on materials that can be prepared by atomic layer deposition (ALD). Besides Al2O3, various other novel passivation schemes have recently been developed, such as Ga2O3, Ta2O5,

Simulations of the BNL/SLAC/UCLA 1.6 cell emittance compensated photocathode RF gun low energy beam line

International Nuclear Information System (INIS)

Palmer, D.T.; Miller, R.H.; Winick, H.

1995-01-01

A dedicated low energy (2 to 10 MeV) experimental beam line is now under construction at Brookhaven National Laboratories Accelerator Test Facility (BNL/ATF) for photocathode RF gun testing and photoemission experiments. The design of the experimental line, using the 1.6 cell photocathode RF gun developed by the BNL/SLAC/UCLA RF gun collaboration is presented. Detailed beam dynamics simulations were performed for the 1.6 cell RF gun injector using a solenoidal emittance compensation technique. An experimental program for testing the 1.6 cell RF gun is presented. This program includes beam loading caused by dark current, higher order mode field measurements, integrated and slice emittance measurements using a pepper-pot and RF kicker cavity

Radicals and ions controlling by adjusting the antenna-substrate distance in a-Si:H deposition using a planar ICP for c-Si surface passivation

Energy Technology Data Exchange (ETDEWEB)

Zhou, H.P., E-mail: haipzhou@uestc.edu.cn [School of Energy Science and Engineering, University of Electronic Science and Technology of China, 2006 Xiyuan Ave., West High-Tech Zone, Chengdu, Sichuan, 611731 (China); Plasma Sources and Application Center, NIE, and Institute of Advanced Studies, Nanyang Technological University, 637616 (Singapore); Xu, S., E-mail: shuyan.xu@nie.edu.sg [Plasma Sources and Application Center, NIE, and Institute of Advanced Studies, Nanyang Technological University, 637616 (Singapore); Xu, M. [Key Laboratory of Information Materials of Sichuan Province & School of Electrical and Information Engineering, Southwest University for Nationalities, Chengdu, 610041 (China); Xu, L.X.; Wei, D.Y. [Plasma Sources and Application Center, NIE, and Institute of Advanced Studies, Nanyang Technological University, 637616 (Singapore); Xiang, Y. [School of Energy Science and Engineering, University of Electronic Science and Technology of China, 2006 Xiyuan Ave., West High-Tech Zone, Chengdu, Sichuan, 611731 (China); Xiao, S.Q. [Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education), Department of Electronic Engineering, Jiangnan University, Wuxi, 214122 (China)

2017-02-28

Highlights: • A planar ICP was used to grow a-Si:H films for c-Si surface passivation. • The direct- and remote-plasma was compared for high-quality c-Si surface passivation. • The remote ICP with controlled plasma species and ion bombardments is preferable for the surface passivation of c-Si. - Abstract: Being a key issue in the research and fabrication of silicon heterojunction (SHJ) solar cells, crystalline silicon (c-Si) surface passivation is theoretically and technologically intricate due to its complicate dependence on plasma characteristics, material properties, and plasma-material interactions. Here amorphous silicon (a-Si:H) grown by a planar inductively coupled plasma (ICP) reactor working under different antenna-substrate distances of d was used for the surface passivation of low-resistivity p-type c-Si. It is found that the microstructures (i.e., the crystallinity, Si-H bonding configuration etc.) and passivation function on c-Si of the deposited a-Si:H were profoundly influenced by the parameter of d, which primarily determines the types of growing precursors of SiH{sub n}/H contributing to the film growth and the interaction between the plasma and growing surface. c-Si surface passivation is analyzed in terms of the d-dependent a-Si:H properties and plasma characteristics. The controlling of radical types and ion bombardment on the growing surface through adjusting parameter d is emphasized.

An analysis of the sectorial influence of CSI300 stocks within the directed network

Science.gov (United States)

Mai, Yong; Chen, Huan; Meng, Lei

2014-02-01

This paper uses the Partial Correlation Planar maximally filtered Graph (PCPG) method to construct a directed network for the constituent stocks underlying the China Securities Index 300 (CSI300). We also analyse the impact of individual stocks. We find that the CSI300 market is a scale-free network with a relatively small power law exponent. The volatility of the stock prices has significant impact on other stocks. In the sectorial network, the industrial sector is the most influential one over other sectors, the financial sector only has a modest influence, while the telecommunication services sector’s influence is marginal. In addition, such inter-sector influence displays quarterly stability.

Design and modeling of a 17 GHz photocathode RF gun

International Nuclear Information System (INIS)

Lin, C.L.; Chen, S.C.; Wurtele, J.S.; Temkin, R.; Danly, B.

1991-01-01

The performance of a high-frequency (17 GHz), high accelerating gradient (250 MV/m) photocathode RF gun is studied with the particle-in-cell code MAGIC. For the parameter regime of interest, i.e. bunch charge smaller than 1 nC and bunch length shorter than 2 ps, space-charge forces and finite bunch length effects are less significant in determining the beam quality than nonlinear RF forces are. The cavity geometry, RF phase for photoemission, cathode size, and current density are being optimized to obtain high quality beams. Preliminary results are presented

Cu2O/CuO Bilayered Composite as a High-Efficiency Photocathode for Photoelectrochemical Hydrogen Evolution Reaction

Science.gov (United States)

Yang, Yang; Xu, Di; Wu, Qingyong; Diao, Peng

2016-10-01

Solar powered hydrogen evolution reaction (HER) is one of the key reactions in solar-to-chemical energy conversion. It is desirable to develop photocathodic materials that exhibit high activity toward photoelectrochemical (PEC) HER at more positive potentials because a higher potential means a lower overpotential for HER. In this work, the Cu2O/CuO bilayered composites were prepared by a facile method that involved an electrodeposition and a subsequent thermal oxidation. The resulting Cu2O/CuO bilayered composites exhibited a surprisingly high activity and good stability toward PEC HER, expecially at high potentials in alkaline solution. The photocurrent density for HER was 3.15 mA·cm-2 at the potential of 0.40 V vs. RHE, which was one of the two highest reported at the same potential on copper-oxide-based photocathode. The high photoactivity of the bilayered composite was ascribed to the following three advantages of the Cu2O/CuO heterojunction: (1) the broadened light absorption band that made more efficient use of solar energy, (2) the large space-charge-region potential that enabled a high efficiency for electron-hole separation, and (3) the high majority carrier density that ensured a faster charge transportation rate. This work reveals the potential of the Cu2O/CuO bilayered composite as a promising photocathodic material for solar water splitting.

Transmission photocathodes based on stainless steel mesh and quartz glass coated with N-doped DLC thin films prepared by reactive magnetron sputtering

Science.gov (United States)

Balalykin, N. I.; Huran, J.; Nozdrin, M. A.; Feshchenko, A. A.; Kobzev, A. P.; Arbet, J.

2016-03-01

The influence was investigated of N-doped diamond-like carbon (DLC) films properties on the quantum efficiency of a prepared transmission photocathode. N-doped DLC thin films were deposited on a silicon substrate, a stainless steel mesh and quartz glass (coated with 5 nm thick Cr adhesion film) by reactive magnetron sputtering using a carbon target and gas mixture Ar, 90%N2+10%H2. The elements' concentration in the films was determined by RBS and ERD. The quantum efficiency was calculated from the measured laser energy and the measured cathode charge. For the study of the vectorial photoelectric effect, the quartz type photocathode was irradiated by intensive laser pulses to form pin-holes in the DLC film. The quantum efficiency (QE), calculated at a laser energy of 0.4 mJ, rose as the nitrogen concentration in the DLC films was increased and rose dramatically after the micron-size perforation in the quartz type photocathodes.

Hydrogen Production Using a Molybdenum Sulfide Catalyst on a Titanium-Protected n+p-Silicon Photocathode

DEFF Research Database (Denmark)

Seger, Brian; Laursen, Anders Bo; Vesborg, Peter Christian Kjærgaard

2012-01-01

A low-cost substitute: A titanium protection layer on silicon made it possible to use silicon under highly oxidizing conditions without oxidation of the silicon. Molybdenum sulfide was electrodeposited on the Ti-protected n+p-silicon electrode. This electrode was applied as a photocathode for wat...

Degradation of Alkali-Based Photocathodes from Exposure to Residual Gases: A First-Principles Study

International Nuclear Information System (INIS)

Wang, Gaoxue; Batista, Enrique R.

2017-01-01

Photocathodes are a key component in the production of electron beams in systems such as X-ray free-electron lasers and X-ray energy-recovery linacs. Alkali-based materials display high quantum efficiency (QE), however, their QE undergoes degradation faster than metal photocathodes even in the high vacuum conditions where they operate. The high reactivity of alkali-based surfaces points to surface reactions with residual gases as one of the most important factors for the degradation of QE. In order to advance the understanding on the degradation of the QE, we investigated the surface reactivity of common residual gas molecules (e.g., O 2 , CO 2 , CO, H 2 O, N 2 , and H 2 ) on one of the best-known alkali-based photocathode materials, cesium antimonide (Cs 3 Sb), using first-principles calculations based on density functional theory. Furthermore, the reaction sites, adsorption energy, and effect in the local electronic structure upon reaction of these molecules on (001), (110), and (111) surfaces of Cs 3 Sb were computed and analyzed. The adsorption energy of these molecules on Cs3Sb follows the trend of O 2 (-4.5 eV) > CO 2 (-1.9 eV) > H 2 O (-1.0 eV) > CO (-0.8 eV) > N 2 (-0.3 eV) ≈ H 2 (-0.2 eV), which agrees with experimental data on the effect of these gases on the degradation of QE. The interaction strength is determined by the charge transfer from the surfaces to the molecules. The adsorption and dissociation of O containing molecules modify the surface chemistry such as the composition, structure, charge distribution, surface dipole, and work function of Cs 3 Sb, resulting in the degradation of QE with exposure to O 2 , CO 2 , H 2 O, and CO.

Atomic hydrogen cleaning of GaAs photocathodes

International Nuclear Information System (INIS)

Poelker, M.; Price, J.; Sinclair, C.

1997-01-01

It is well known that surface contaminants on semiconductors can be removed when samples are exposed to atomic hydrogen. Atomic H reacts with oxides and carbides on the surface, forming compounds that are liberated and subsequently pumped away. Experiments at Jefferson lab with bulk GaAs in a low-voltage ultra-high vacuum H cleaning chamber have resulted in the production of photocathodes with high photoelectron yield (i.e., quantum efficiency) and long lifetime. A small, portable H cleaning apparatus also has been constructed to successfully clean GaAs samples that are later removed from the vacuum apparatus, transported through air and installed in a high-voltage laser-driven spin-polarized electron source. These results indicate that this method is a versatile and robust alternative to conventional wet chemical etching procedures usually employed to clean bulk GaAs

Immobilized nickel hexacyanoferrate on activated carbons for efficient attenuation of radio toxic Cs(I) from aqueous solutions

International Nuclear Information System (INIS)

Lalhmunsiama; Lalhriatpuia, C.; Tiwari, Diwakar; Lee, Seung-Mok

2014-01-01

Highlights: • Rice hulls and areca nut wastes are utilized to obtain activated carbons. • Nickel hexacyanoferrate is immobilized on activated carbon samples. • Materials are characterized by SEM–EDX and XRD data. • Materials are employed in attenuation of Cs(I) under batch and column studies. • Possible mechanism is deduced at solid/solution interface. - Abstract: The aim of this study is to immobilize nickel hexacyanoferrate onto the large surface of activated carbons (ACs) precursor to rice hulls and areca nut waste materials. These nickel hexacyanoferrate immobilized materials are then assessed in the effective attenuation of radio logically important cesium ions from aqueous solutions. The solid samples are characterized by the XRD analytical method and surface morphology is obtained from the SEM images. The batch reactor experiments show that an increase in sorptive pH (2.0–10.0) apparently not affecting the high percent uptake of Cs(I). Equilibrium modeling studies suggest that the data are reasonably and relatively fitted well to the Langmuir adsorption isotherm. Kinetic studies show that sorption process is fairly rapid and the kinetic data are fitted well to the pseudo-second order rate model. Increasing the background electrolyte concentration from 0.001 to 0.1 mol/L NaCl causes insignificant decrease in Cs(I) removal which infers the higher selectivity of these materials for Cs(I) from aqueous solutions. Further, the column reactor operations enable to obtain the breakthrough data which are then fitted to the Thomas non-linear equation as to obtain the loading capacity of column for Cs(I). The results show that the modified materials show potential applicability in the attenuation of radio toxic cesium from aqueous solution

Effect of gold photocathode contamination on a flat spectral response X-ray diode

Science.gov (United States)

Wang, Kun-lun; Zhang, Si-qun; Zhou, Shao-tong; Huang, Xian-bin; Ren, Xiao-dong; Dan, Jia-kun; Xu, Qiang

2018-03-01

A detector with an approximately flat spectral response is important for diagnosing intense thermal X-ray flux. A flat-spectral-response X-ray diode (FSR-XRD) utilizes a gold photocathode X-ray diode and a specially configured gold filter to give rise to a nearly flat spectral response in the photon energy range of 100-4000 eV. It has been observed that the spectral responses of several FSR-XRDs changed after a few shots of z-pinch experiments on the Primary Test Stand facility. This paper presents an analysis of the changes by fitting the spectral responses of the gold photocathodes using a model with a free parameter which characterizes the thickness of the contamination. The spectral responses of FSR-XRDs were calibrated with synchrotron radiation, and several cleaning methods were tested with the calibration. Considering the results of model and cleaning, it may be anticipated that contamination was the major reason of the response changing. Contamination worsened the flatness of the spectral response of the FSR-XRD and decreased the averaged response, hence it is important to avoid contamination. Current results indicate a requirement of further study of the contamination.

Hot Hole Collection and Photoelectrochemical CO2 Reduction with Plasmonic Au/p-GaN Photocathodes.

Science.gov (United States)

DuChene, Joseph S; Tagliabue, Giulia; Welch, Alex J; Cheng, Wen-Hui; Atwater, Harry A

2018-04-11

Harvesting nonequilibrium hot carriers from plasmonic-metal nanostructures offers unique opportunities for driving photochemical reactions at the nanoscale. Despite numerous examples of hot electron-driven processes, the realization of plasmonic systems capable of harvesting hot holes from metal nanostructures has eluded the nascent field of plasmonic photocatalysis. Here, we fabricate gold/p-type gallium nitride (Au/p-GaN) Schottky junctions tailored for photoelectrochemical studies of plasmon-induced hot-hole capture and conversion. Despite the presence of an interfacial Schottky barrier to hot-hole injection of more than 1 eV across the Au/p-GaN heterojunction, plasmonic Au/p-GaN photocathodes exhibit photoelectrochemical properties consistent with the injection of hot holes from Au nanoparticles into p-GaN upon plasmon excitation. The photocurrent action spectrum of the plasmonic photocathodes faithfully follows the surface plasmon resonance absorption spectrum of the Au nanoparticles and open-circuit voltage studies demonstrate a sustained photovoltage during plasmon excitation. Comparison with Ohmic Au/p-NiO heterojunctions confirms that the vast majority of hot holes generated via interband transitions in Au are sufficiently hot to inject above the 1.1 eV interfacial Schottky barrier at the Au/p-GaN heterojunction. We further investigated plasmon-driven photoelectrochemical CO 2 reduction with the Au/p-GaN photocathodes and observed improved selectivity for CO production over H 2 evolution in aqueous electrolytes. Taken together, our results offer experimental validation of photoexcited hot holes more than 1 eV below the Au Fermi level and demonstrate a photoelectrochemical platform for harvesting hot carriers to drive solar-to-fuel energy conversion.

On the Secrecy Capacity Region of the Block-Fading BCC with Limited CSI Feedback

KAUST Repository

Hyadi, Amal

2017-02-07

In this work, we examine the secrecy capacity region of the block-fading broadcast channel with confidential messages (BCC) when the transmitter has limited knowledge of the channel. In particular, we consider a two-user communication system where the transmitter has one common message to be transmitted to both users and one confidential message intended to only one of them. The confidential message has to be kept secret from the other user to whom the information is not intended. The transmitter is not aware of the channel state information (CSI) of neither channel and is only provided by limited CSI feedback sent at the beginning of each fading block. Assuming an error-free feedback link, we characterize the secrecy capacity region of this channel and show that even with a 1-bit CSI feedback, a positive secrecy rate can still be achieved. Then, we look at the case where the feedback link is not error- free and is rather a binary erasure channel (BEC). In the latter case, we provide an achievable secrecy rate region and show that as long as the erasure event is not a probability 1 event, the transmitter can still transmit the confidential information with a positive secrecy rate.

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.

Biosorption of Cd(II) and Cs(I) from aqueous solution by live and dead cells of Saccharomyces carlsbergensis PTCC 5051.

Science.gov (United States)

Sayyadi, Shayan; Ahmady-Asbchin, Salman; Kamali, Kasra

2018-02-01

The biosorption characteristics of Cd(II) and Cs(I) using live and dead cells of Saccharomyces carlsbergensis PTCC 5051 as biosorbents have been investigated in the present research. The influence of different experimental parameters such as initial pH (pHi), shaking rate, sorption time and initial metal concentration was evaluated. The optimum pH was obtained as 4 for Cd(II) and 7 for Cs(I). The experimental adsorption data were fitted to the Langmuir linear equation adsorption model. The highest metal uptake values of 0.593 and 0.473 mmol g -1 were calculated for Cd(II) and Cs(I), respectively. The results of Fourier transform infrared analysis suggested the involvement of amine, carboxyl and hydroxyl groups during the biosorption process and also indicated that more functional groups were involved in the biosorption process of live adsorbents, compared with those linked to dead biomass. The results showed that the biomass of S. carlsbergensis PTCC 5051 is a suitable biosorbent for the removal of Cd(II) and Cs(I) from the aqueous solutions.

Surface-plasmon enhanced photoemission of a silver nano-patterned photocathode

Science.gov (United States)

Zhang, Z.; Li, R.; To, H.; Andonian, G.; Pirez, E.; Meade, D.; Maxson, J.; Musumeci, P.

2017-09-01

Nano-patterned photocathodes (NPC) take advantage of plasmonic effects to resonantly increase absorption of light and localize electromagnetic field intensity on metal surfaces leading to surface-plasmon enhanced photoemission. In this paper, we report the status of NPC research at UCLA including in particular the optimization of the dimensions of a nanohole array on a silver wafer to enhance plasmonic response at 800 nm light, the development of a spectrally-resolved reflectivity measurement setup for quick nanopattern validation, and of a novel cathode plug to enable high power tests of NPCs on single crystal substrates in a high gradient radiofrequency gun.

High power testing of a 17 GHz photocathode RF gun

International Nuclear Information System (INIS)

Chen, S.C.; Danly, B.G.; Gonichon, J.

1995-01-01

The physics and technological issues involved in high gradient particle acceleration at high microwave (RF) frequencies are under study at MIT. The 17 GHz photocathode RF gun has a 1 1/2 cell (π mode) room temperature cooper cavity. High power tests have been conducted at 5-10 MW levels with 100 ns pulses. A maximum surface electric field of 250 MV/m was achieved. This corresponds to an average on-axis gradient of 150 MeV/m. The gradient was also verified by a preliminary electron beam energy measurement. Even high gradients are expected in our next cavity design

Achievable Rates of Cognitive Radio Networks Using Multi-Layer Coding with Limited CSI

KAUST Repository

Sboui, Lokman; Rezki, Zouheir; Alouini, Mohamed-Slim

2016-01-01

In a Cognitive Radio (CR) framework, the channel state information (CSI) feedback to the secondary transmitter (SU Tx) can be limited or unavailable. Thus, the statistical model is adopted in order to determine the system performance using

Opportunistic Energy-Aware Amplify-and-Forward Cooperative Systems with Imperfect CSI

KAUST Repository

Amin, Osama

2015-07-29

Recently, much attention has been paid to the green design of wireless communication systems using energy efficiency (EE) metrics that should capture all energy consumption sources to deliver the required data. In this paper, we design an energyefficient relay assisted communication system based on estimated channel state information (CSI). It employs amplify-andforward relaying and switches between different communication schemes, which are known as direct-transmission, two-hop and cooperative-transmission schemes, using the estimated CSI in order to maximize the EE. Two estimation strategies are assumed, namely disintegrated channel estimation and cascaded channel estimation. To formulate an accurate EE metric for the proposed opportunistic amplify-and-forward system, the channel estimation cost is reflected on the EE metric by including its impact in the signal-to-noise ratio term and in the energy consumption during the channels estimation phase. Based on the formulated EE metric, we propose an adaptive power allocation algorithm to maximize the EE of the proposed opportunistic amplify-andforward system with channel estimation. Furthermore, we study the impact of the estimation parameters on the proposed system via simulation examples.

Study of the interface in n{sup +}{mu}c-Si/p-type c-Si heterojunctions: role of the fluorine chemistry in the interface passivation

Energy Technology Data Exchange (ETDEWEB)

Losurdo, M.; Grimaldi, A.; Sacchetti, A.; Capezzuto, P.; Ambrico, M.; Bruno, G.; Roca, Francesco

2003-03-03

Investigation of n-p heterojunction solar cells obtained by depositing a n-type thin silicon films either amorphous or microcrystalline on p-type c-Si is carried out. The study is focused on the improvement of the c-Si surface and emitter layer/c-Si substrate interface. The peculiarity is the use of SiF{sub 4}-based plasmas for the in situ dry cleaning and passivation of the c-Si surface and for the PECVD deposition of the emitter layer that can be either amorphous (a-Si:H,F) or microcrystalline ({mu}c-Si). The use of SiF{sub 4} instead of the conventional SiH{sub 4} results in a lower hydrogen content in the film and in a reduction of the interaction of the c-Si surface with hydrogen atoms. Furthermore, the dependence of the heterojunction solar cell photovoltaic parameters on the insertion of an intrinsic buffer layer between the n-type thin silicon layer and the p-type c-Si substrate is discussed.

Development status of a test stand for semiconductor photocathodes with 60 keV spin-polarized beamline

Energy Technology Data Exchange (ETDEWEB)

Kurichijanil, Neeraj; Enders, Joachim; Espig, Martin; Fritzsche, Yuliya; Heichelt, Dominic; Kaiser, Andreas; Roesch, Heidi; Wagner, Markus [Institut fuer Kernphysik, TU Darmstadt (Germany)

2016-07-01

A test facility for Photo-Cathode Activation, Test and Cleaning using atomic-Hydrogen (Photo-CATCH) is being constructed at TU Darmstadt's Institute for Nuclear Physics (IKP) which houses the Superconducting Darmstadt Linear Accelerator (S-DALINAC). In order to improve the performance of the SDALINAC's photoelectron source based on GaAs, systematic studies in terms of quantum efficiency (QE), cathode rejuvenation, lifetimes and polarization (P) have to be conducted on different photocathode types. These factors strongly depend on handling of the cathode, the vacuum condition in the chambers, cathode surface cleaning as well as preservation of stoichiometry, negative electron affinity (NEA) activation of the cathode and the type and structure of the semiconductor material. With Photo-CATCH, experiments such as atomic-hydrogen cleaning, multi-alkali and oxidant NEA activation of the cathode and tests of QE, P and lifetimes can be performed in an improved vacuum. Additionally, experiments with polarized-electron beams of up to 60 keV are foreseen.

Adsorption and revaporisation studies of thin iodine oxide and CsI aerosol deposits from containment surface materials in LWRs

Energy Technology Data Exchange (ETDEWEB)

Tietze, S.; Foreman, M.; Ekberg, C. [Chalmers Univ. of Technology, Goeteborg (Sweden); Kaerkelae, T.; Auvinen, A.; Tapper, U.; Jokiniemi, J. [VTT Technical Research Centre of Finland, Espoo (Finland)

2013-07-15

speciation of the particles. The formation of HIO{sub 3} was verified with Raman analysis regardless of the reaction temperature. Furthermore, elemental iodine was also observed in the measured Raman spectra. Probably, iodine oxide particles had reacted with air humidity forming iodic acid and elemental iodine. IOx and CsI particles that were deposited on various sample surfaces were synthesized at 120 deg. C. According to XPS analysis, it seemed that IOx particles were mainly in form of HIO{sub 3} on the metal and on the painted surfaces. The XPS spectrum of CsI was observed on all metal and painted samples on which CsI particles were deposited. However, the CsI particles seemed to have dissolved at least partially by air humidity. Iodine was observed at areas outside the caesium iodide deposits on metal and on painted surfaces. According to the XPS analyses, iodine was in oxidised form. The measurements indicated that iodine may have reacted with the oxidized metal surfaces to form metal iodates. Only trace amounts of oxidized iodine were detected on the painted surfaces. An interesting result in the XPS analysis was that a part of the acquired signal from CsI on the painted surfaces seemed to originate deeper from the structure of the paint when it was pre-treated either with heat or gamma irradiation. SEM analysis revealed that heat and gamma irradiation treatment increased the porosity of the paint. Therefore, dissolved CsI may have been transported into the matrix of the paint. Besides copper the studied metal surfaces underwent slow reactions with the iodine of the aerosol deposits which showed in the high revaporisation rates at room temperature and elevated temperatures. On the copper and paint samples it could be shown that these surfaces react more easily with the iodine from cesium iodide deposits. From the chemically converted metal iodides only copper iodide remained on the surfaces after exposure to hot humid air and as well after immersion in boiling water

Adsorption and revaporisation studies of thin iodine oxide and CsI aerosol deposits from containment surface materials in LWRs

International Nuclear Information System (INIS)

Tietze, S.; Foreman, M.; Ekberg, C.; Kaerkelae, T.; Auvinen, A.; Tapper, U.; Jokiniemi, J.

2013-07-01

the particles. The formation of HIO 3 was verified with Raman analysis regardless of the reaction temperature. Furthermore, elemental iodine was also observed in the measured Raman spectra. Probably, iodine oxide particles had reacted with air humidity forming iodic acid and elemental iodine. IOx and CsI particles that were deposited on various sample surfaces were synthesized at 120 deg. C. According to XPS analysis, it seemed that IOx particles were mainly in form of HIO 3 on the metal and on the painted surfaces. The XPS spectrum of CsI was observed on all metal and painted samples on which CsI particles were deposited. However, the CsI particles seemed to have dissolved at least partially by air humidity. Iodine was observed at areas outside the caesium iodide deposits on metal and on painted surfaces. According to the XPS analyses, iodine was in oxidised form. The measurements indicated that iodine may have reacted with the oxidized metal surfaces to form metal iodates. Only trace amounts of oxidized iodine were detected on the painted surfaces. An interesting result in the XPS analysis was that a part of the acquired signal from CsI on the painted surfaces seemed to originate deeper from the structure of the paint when it was pre-treated either with heat or gamma irradiation. SEM analysis revealed that heat and gamma irradiation treatment increased the porosity of the paint. Therefore, dissolved CsI may have been transported into the matrix of the paint. Besides copper the studied metal surfaces underwent slow reactions with the iodine of the aerosol deposits which showed in the high revaporisation rates at room temperature and elevated temperatures. On the copper and paint samples it could be shown that these surfaces react more easily with the iodine from cesium iodide deposits. From the chemically converted metal iodides only copper iodide remained on the surfaces after exposure to hot humid air and as well after immersion in boiling water. Both, non aged and

Outage Performance of Decode-and-Forward in Two-Way Relaying with Outdated CSI

KAUST Repository

Hyadi, Amal

2015-01-07

In this paper, we analyze the outage behavior of decode-and-forward relaying in the context of selective two-way cooperative systems. First, a new relay selection metric is proposed to take into consideration both transmission rates and instantaneous link conditions between cooperating nodes. Afterwards, the outage probability of the proposed system is derived for Nakagami-m fading channels in the case when perfect channel state information is available and then extended to the more realistic scenario where the available channel state information (CSI) is outdated due to fast fading. New expressions for the outage probability are obtained, and the impact of imperfect CSI on the performance is evaluated. Illustrative numerical results, Monte Carlo simulations, and comparisons with similar approaches are presented to assess the accuracy of our analytical derivations and confirm the performance gain of the proposed scheme.

Minimax robust power split in AF relays based on uncertain long-term CSI

KAUST Repository

Nisar, Muhammad Danish; Alouini, Mohamed-Slim

2011-01-01

An optimal power control among source and relay nodes in presence of channel state information (CSI) is vital for an efficient amplify and forward (AF) based cooperative communication system. In this work, we study the optimal power split (power

Effect of annealing process on the heterostructure CuO/Cu2O as a highly efficient photocathode for photoelectrochemical water reduction

Science.gov (United States)

Du, Fan; Chen, Qing-Yun; Wang, Yun-Hai

2017-05-01

CuO/Cu2O photocathodes were successfully prepared via simply annealing the electrodeposited Cu2O on fluoride doped tin oxide (FTO) substrate. They were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscope (TEM), UV-vis absorption spectra and X-ray photoelectron spectroscopy (XPS). The results showed that the heterojunction of CuO/Cu2O was formed during the annealing process and presented the nature of p-type semiconductor. The photocurrent density and photoelectrochemical (PEC) stability of the p-type heterostructure CuO/Cu2O photocathode was improved greatly compared with the pure Cu2O, which was greatly affected by annealing time and temperature. The highest photo current density of -0.451 mA/cm2 and highest stability was obtained via annealing at 650 °C for 15 min (at -0.3 V vs. Ag/AgCl), which gave a remarkable improvement than the as-deposited Cu2O (-0.08 mA/cm2). This suggested that the CuO/Cu2O heterojunction facilitated the electron-hole pair separation and improved the photocathode's current and stability.

Non-Identity-Mediated CRISPR-Bacteriophage Interaction Mediated via the Csy and Cas3 Proteins ▿#

Science.gov (United States)

Cady, Kyle C.; O'Toole, George A.

2011-01-01

Studies of the Escherichia, Neisseria, Thermotoga, and Mycobacteria clustered regularly interspaced short palindromic repeat (CRISPR) subtypes have resulted in a model whereby CRISPRs function as a defense system against bacteriophage infection and conjugative plasmid transfer. In contrast, we previously showed that the Yersinia-subtype CRISPR region of Pseudomonas aeruginosa strain UCBPP-PA14 plays no detectable role in viral immunity but instead is required for bacteriophage DMS3-dependent inhibition of biofilm formation by P. aeruginosa. The goal of this study is to define the components of the Yersinia-subtype CRISPR region required to mediate this bacteriophage-host interaction. We show that the Yersinia-subtype-specific CRISPR-associated (Cas) proteins Csy4 and Csy2 are essential for small CRISPR RNA (crRNA) production in vivo, while the Csy1 and Csy3 proteins are not absolutely required for production of these small RNAs. Further, we present evidence that the core Cas protein Cas3 functions downstream of small crRNA production and that this protein requires functional HD (predicted phosphohydrolase) and DEXD/H (predicted helicase) domains to suppress biofilm formation in DMS3 lysogens. We also determined that only spacer 1, which is not identical to any region of the DMS3 genome, mediates the CRISPR-dependent loss of biofilm formation. Our evidence suggests that gene 42 of phage DMS3 (DMS3-42) is targeted by CRISPR2 spacer 1 and that this targeting tolerates multiple point mutations between the spacer and DMS3-42 target sequence. This work demonstrates how the interaction between P. aeruginosa strain UCBPP-PA14 and bacteriophage DMS3 can be used to further our understanding of the diverse roles of CRISPR system function in bacteria. PMID:21398535

From a sociology of mediation to a pragmatics of attachments. An intellectual journey within the CSI revisited

OpenAIRE

Hennion, Antoine

2017-01-01

Este artículo enfoca sobre un retorno reflexivo en mi propia trayectoria en el CSI. Mi propósito no es fijar la historia sino releerla desde las preocupaciones presentes. Desde su fundación por L. Karpik en 1967, el CSI abogó por tomar seriamente las realidades que estaba investigando (derecho, ciencia y tecnología, negocios, cultura). Bajo el título de un posible “retorno al objeto” en sociología, discuto convergencias y diferencias en el trabajo de campo emprendido, por un lado, sobre la ci...

Luminescent properties of BaCl2-Eu microcrystals embedded in a CsI matrix

International Nuclear Information System (INIS)

Pushak, A.; Vistovskyy, V.; Voloshinovskii, A.; Savchyn, P.; Antonyak, O.; Demkiv, T.; Dacyuk, Yu.; Myagkota, S.; Gektin, A.

2013-01-01

The spectral-luminescent properties of CsI-BaCl 2 (1 mol%)-Eu(0.02 mol%) crystalline system are studied. Europium ion doped BaCl 2 microcrystals embedded in a CsI matrix are revealed on CsI-BaCl 2 (1 mol%)-Eu(0.02 mol%) freshly cleaved surface by the scanning electron microscopy. The size of microcrystals is shown to be within 0.5–5 microns. The luminescent parameters of the BaCl 2 -Eu 2+ microcrystals are shown to be similar to ones of a single crystal analogue. The 4f → 5d absorption transitions in europium ions and the reabsorption of the intrinsic emission of the CsI host are the main excitation mechanisms of europium luminescence in the BaCl 2 microcrystals. -- Highlights: ► The formation of chloride BaCl 2 :Eu microcrystals in the case of BaCl 2 doped CsI crystal has been revealed. ► The observed size of microcrystals at BaCl 2 concentration of 1% is about 0.5–5 μm. ► Majority of Eu 2+ ions in CsI-BaCl 2 -EuCl 3 crystalline system enters into BaCl 2 microcrystals. ► The luminescent parameters of the BaCl 2 :Eu 2+ microcrystals and its bulk analogue are similar

High power beam test and measurement of emittance evolution of a 1.6-cell photocathode RF gun at Pohang Accelerator Laboratory

International Nuclear Information System (INIS)

Park, Jang-Ho; Park, Sung-Ju; Kim, Changbum; Huang, Jung-Yun; Ko, In Soo; Parc, Yong-Woon; Hong, Ju-Ho; Xiang Dao; Wang, Xijie

2007-01-01

A Brookhaven National Laboratory (BNL) GUN-IV type photocathode rf gun has been fabricated to use in femtosecond electron diffraction (FED), femtosecond far infrared radiation (fs-FIR) facility, and X-ray free electron laser (XFEL) facilities at the Pohang Accelerator Laboratory (PAL). The gun consists of a 1.6-cell cavity with a copper cathode, a solenoid magnet, beam diagnostic components and auxiliary systems. We report here the measurement of the basic beam parameters which confirm a successful fabrication of the photocathode RF gun system. The emittance evolution is measured by an emittance meter and compared with the PARMELA simulation, which shows a good agreement. (author)

Impact of I/Q imbalance on the performance of two-way CSI-assisted AF relaying

KAUST Repository

Qi, Jian; Aï ssa, Sonia; Alouini, Mohamed-Slim

2013-01-01

In this paper, we investigate half-duplex two-way dual-hop channel state information (CSI)-assisted amplify-and-forward (AF) relaying in the presence of in-phase and quadrature-phase (I/Q) imbalance. A compensation approach for the I/Q imbalance is proposed, which employs the received signals together with their conjugations to detect the desired signal. We also derive the average symbol error probability of the considered half-duplex two-way dual-hop CSI-assisted AF relaying networks with and without compensation for I/Q imbalance in Rayleigh fading channels. Numerical results are provided and show that the proposed compensation method mitigates the impact of I/Q imbalance to a certain extent. © 2013 IEEE.

Impact of I/Q imbalance on the performance of two-way CSI-assisted AF relaying

KAUST Repository

Qi, Jian

2013-04-01

In this paper, we investigate half-duplex two-way dual-hop channel state information (CSI)-assisted amplify-and-forward (AF) relaying in the presence of in-phase and quadrature-phase (I/Q) imbalance. A compensation approach for the I/Q imbalance is proposed, which employs the received signals together with their conjugations to detect the desired signal. We also derive the average symbol error probability of the considered half-duplex two-way dual-hop CSI-assisted AF relaying networks with and without compensation for I/Q imbalance in Rayleigh fading channels. Numerical results are provided and show that the proposed compensation method mitigates the impact of I/Q imbalance to a certain extent. © 2013 IEEE.

Surface Passivation Mechanism of Atomic Layer Deposited Al2O3 Films on c-Si Studied by Optical Second-Harmonic Generation

NARCIS (Netherlands)

Gielis, J.J.H.; Verlaan, V.; Dingemans, G.; Sanden, van de M.C.M.; Kessels, W.M.M.; Terlinden, N.M.

2009-01-01

Recently, it was shown that Al2O3 thin films synthesized by (plasmaassisted) atomic layer deposition (ALD) provide excellent surface passivation of n, p and p+ type c-Si as highly relevant for c-Si photovoltaics. It was found that a large negative fixed charge density (up to 1013 cm-2) in the Al2O3

Photocathodic Protection of 304 Stainless Steel by Bi2S3/TiO2 Nanotube Films Under Visible Light.

Science.gov (United States)

Li, Hong; Wang, Xiutong; Wei, Qinyi; Hou, Baorong

2017-12-01

We report the preparation of TiO 2 nanotubes coupled with a narrow bandgap semiconductor, i.e., Bi 2 S 3 , to improve the photocathodic protection property of TiO 2 for metals under visible light. Bi 2 S 3 /TiO 2 nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of Bi 2 S 3 deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO 2 and orthorhombic Bi 2 S 3 and exhibited a high visible light response. The photocurrent density of Bi 2 S 3 /TiO 2 was significantly higher than that of pure TiO 2 under visible light. The sensitization of Bi 2 S 3 enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO 2 . The Bi 2 S 3 /TiO 2 nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.

Photocathodic Protection of 304 Stainless Steel by Bi2S3/TiO2 Nanotube Films Under Visible Light

Science.gov (United States)

Li, Hong; Wang, Xiutong; Wei, Qinyi; Hou, Baorong

2017-01-01

We report the preparation of TiO2 nanotubes coupled with a narrow bandgap semiconductor, i.e., Bi2S3, to improve the photocathodic protection property of TiO2 for metals under visible light. Bi2S3/TiO2 nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of Bi2S3 deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO2 and orthorhombic Bi2S3 and exhibited a high visible light response. The photocurrent density of Bi2S3/TiO2 was significantly higher than that of pure TiO2 under visible light. The sensitization of Bi2S3 enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO2. The Bi2S3/TiO2 nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.

Hydrogen and electricity production in a light-assisted microbial photoelectrochemical cell with CaFe2O4 photocathode

Science.gov (United States)

Chen, Qing-Yun; Zhang, Kai; Liu, Jian-Shan; Wang, Yun-Hai

2017-04-01

A microbial photoelectrochemical cell (MPEC) was designed with a p-type CaFe2O4 semiconductor as the photoelectrode for simultaneous hydrogen and electricity production under light illumination. The CaFe2O4 photoelectrode was synthesized by the sol-gel method and well characterized by x-ray diffraction, field emission scanning electron microscope, and UV-Vis-NIR spectrophotometer. The linear sweep voltammogram of the CaFe2O4 photoelectrode presented the cathodic photocurrent output. For the MPEC, with an external resistance of 2000 Ω, the maximum power density of 143 mW was obtained. Furthermore, with an external resistance of 100 Ω, the maximum hydrogen production rate of 6.7 μL·cm-2 could be achieved. The MPEC with CaFe2O4 photocathode was compared to MPEC with other photocathodes as well as photocatalytic water splitting technology.

Enhanced columnar structure in CsI layer by substrate patterning

Energy Technology Data Exchange (ETDEWEB)

Jing, T.; Cho, G.; Drewery, J.; Kaplan, S.N.; Mireshghi, A.; Perez-Mendez, V.; Wildermuth, D. [Lawrence Berkeley Lab., CA (United States); Fujieda, I. [Xerox Palo Alto Research Center, CA (United States)

1991-10-01

Columnar structure in evaporated CsI layers can be controlled by patterning substrates as well as varying evaporation conditions. Mesh-patterned substrates with various dimensions were created by spin-coating polyimide on glass or amorphous silicon substrates and defining patterns with standard photolithography technique. CsI(Tl) layers 200--1000 {mu}m were evaporated. Scintillation properties of these evaporated layers, such as light yield and speed, were equivalent to those of the source materials. Spatial resolution of X-ray detectors consisting of these layers and a linear array of X-ray detectors consisting of these layers and a linear array of Si photodiodes was evaluated by exposing them to a 25{mu}m narrow beam of X-ray. The results obtained with 200{mu}m thick CsI layers coupled to a linear photodiode array with 20 dots/mm resolution showed that the spatial resolution of CsI(Tl) evaporated on patterned substrates was about 75 {mu}m FWHM, whereas that on CsI(Tl) on flat substrates was about 230 {mu}m FWHM. Micrographs taken by SEM revealed that these layers retained the well-defined columnar structure originating from substrate patterns. Adhesion and light transmission of CsI(Tl) were also improved by patterning the substrate.

Acinetobacter calcoaceticus CSY-P13 Mitigates Stress of Ferulic and p-Hydroxybenzoic Acids in Cucumber by Affecting Antioxidant Enzyme Activity and Soil Bacterial Community

Directory of Open Access Journals (Sweden)

Fenghui Wu

2018-06-01

Full Text Available Ferulic acid (FA and p-hydroxybenzoic acid (PHBA are main phenolic compounds accumulated in rhizosphere of continuously cropped cucumber, causing stress in plants. Microbial degradation of a mixture of FA and PHBA is not well understood in soil. We isolated a strain CSY-P13 of Acinetobacter calcoaceticus, inoculated it into soil to protect cucumber from FA and PHBA stress, and explored a mechanism underlying the protection. CSY-P13 effectively degraded a mixture of FA and PHBA in culture solution under conditions of 39.37°C, pH 6.97, and 21.59 g L-1 potassium dihydrogen phosphate, giving rise to 4-vinyl guaiacol, vanillin, vanillic acid, and protocatechuic acid. During FA and PHBA degradation, activities of superoxide dismutase (SOD, catalase, ascorbate peroxidase, and dehydroascorbate reductase in CSY-P13 were induced. Inoculated into cucumber-planted soil containing 220 μg g-1 mixture of FA and PHBA, CSY-P13 degraded FA and PHBA in soil, increased plant height, and decreased malonaldehyde, superoxide radical, and hydrogen peroxide levels in leaves. CSY-P13 also enhanced SOD, guaiacol peroxidase, catalase, glutathione peroxidase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase activities; increased ascorbate and glutathione contents; and elevated transcript levels of copper/zinc SOD, manganese SOD, and catalase in leaves under FA and PHBA. Moreover, CSY-P13 increased phosphatase, catalase, urease, and sucrase activities and changed bacterial richness, diversity, and community composition by high throughput sequencing in cucumber-planted soil supplemented with the mixture of FA and PHBA. So CSY-P13 degrades the mixture of FA and PHBA in soil and mitigates stress from the two phenolic compounds in cucumber by activating antioxidant enzymes, changing soil bacterial community, and inducing soil enzymes.

Experimental measurements and theoretical model of the cryogenic performance of bialkali photocathode and characterization with Monte Carlo simulation

Directory of Open Access Journals (Sweden)

Huamu Xie

2016-10-01

Full Text Available High-average-current, high-brightness electron sources have important applications, such as in high-repetition-rate free-electron lasers, or in the electron cooling of hadrons. Bialkali photocathodes are promising high-quantum-efficiency (QE cathode materials, while superconducting rf (SRF electron guns offer continuous-mode operation at high acceleration, as is needed for high-brightness electron sources. Thus, we must have a comprehensive understanding of the performance of bialkali photocathode at cryogenic temperatures when they are to be used in SRF guns. To remove the heat produced by the radio-frequency field in these guns, the cathode should be cooled to cryogenic temperatures. We recorded an 80% reduction of the QE upon cooling the K_{2}CsSb cathode from room temperature down to the temperature of liquid nitrogen in Brookhaven National Laboratory (BNL’s 704 MHz SRF gun. We conducted several experiments to identify the underlying mechanism in this reduction. The change in the spectral response of the bialkali photocathode, when cooled from room temperature (300 K to 166 K, suggests that a change in the ionization energy (defined as the energy gap from the top of the valence band to vacuum level is the main reason for this reduction. We developed an analytical model of the process, based on Spicer’s three-step model. The change in ionization energy, with falling temperature, gives a simplified description of the QE’s temperature dependence. We also developed a 2D Monte Carlo code to simulate photoemission that accounts for the wavelength-dependent photon absorption in the first step, the scattering and diffusion in the second step, and the momentum conservation in the emission step. From this simulation, we established a correlation between ionization energy and reduction in the QE. The simulation yielded results comparable to those from the analytical model. The simulation offers us additional capabilities such as calculation

Investigation of spectral distribution and variation of irradiance with the passage time of CSI lamps which constitute a solar simulator; Solar simulator ni shiyosuru CSI lamp no supekutoru bunpu, hosha shodo no keiji henka ni kansuru chosa

Energy Technology Data Exchange (ETDEWEB)

Sugiyama, T; Yamada, T; Noguchi, T [Japan Quality Assurance Organization, Tokyo (Japan)

1997-11-25

Study was made on time-variation of the performance of CSI lamps for solar simulators. In order to accurately evaluate the standard heat collection performance of solar systems in a room, MITI installed an artificial solar light source in the Solar Techno-Center of Japan Quality Assurance Organization for trial use and evaluation. CSI lamp is superior in durability, and can simulate the solar light in the daytime. The light source is composed of 72 metal halide lamps of 1kW arranged in a plane of 3.5times3.5m. The study result on time-variation of a spectral distribution and irradiance by intermittent switching of lamps showed a sufficient durability of 2000h. To ensure the accuracy of a solar heat collector measurement system enough, periodic calibration is being carried out using reference goods. To ensure the reliability and stability for a switching system, periodic maintenance of a power source, stabilizer and electric system is also being carried out in addition to CSI lamps. The stable irradiance and accuracy are being kept by such maintenance and periodic exchange of lamps. 6 figs., 4 tabs.

High-power fiber lasers for photocathode electron injectors

Directory of Open Access Journals (Sweden)

Zhi Zhao

2014-05-01

Full Text Available Many new applications for electron accelerators require high-brightness, high-average power beams, and most rely on photocathode-based electron injectors as a source of electrons. To achieve such a photoinjector, one requires both a high-power laser system to produce the high average current beam, and also a system at reduced repetition rate for electron beam diagnostics to verify high beam brightness. Here we report on two fiber laser systems designed to meet these specific needs, at 50 MHz and 1.3 GHz repetition rate, together with pulse pickers, second harmonic generation, spatiotemporal beam shaping, intensity feedback, and laser beam transport. The performance and flexibility of these laser systems have allowed us to demonstrate electron beam with both low emittance and high average current for the Cornell energy recovery linac.

Improved Ion Resistance for III-V Photocathodes in High Current Guns

Energy Technology Data Exchange (ETDEWEB)

Mulhollan, Gregory, A.

2012-11-16

The two photocathode test systems were modified, baked and recommissioned. The first system was dedicated to ion studies and the second to electron stimulated recovery (ESR) work. The demonstration system for the electron beam rejuvenation was set up, tested and demonstrated to one of the SSRL team (Dr. Kirby) during a site visit. The requisite subsystems were transferred to SSRL, installed and photoemission studies conducted on activated surfaces following electron beam exposure. Little surface chemistry change was detected in the photoemission spectra following the ESR process. The yield mapping system for the ion (and later, the electron beam rejuvenation) studies was implemented and use made routine. Ion species and flux measurements were performed for H, He, Ne, Ar, Kr and Xe ions at energies of 0.5, 1.0 and 2.0 kV. Gas induced photoyield measurements followed each ion exposure measurement. These data permit the extraction of photoyield induced change per ion (by species) at the measured energies. Electron beam induced rejuvenation was first demonstrated in the second chamber with primary electron beam energy and dependency investigations following. A Hiden quadrupole mass spectrometer for the electron stimulated desorption (ESD) measurements was procured. The UHV test systems needed for subsequent measurements were configured, baked, commissioned and utilized for their intended purposes. Measurements characterizing the desorption products from the ESD process and secondary electron (SE) yield at the surfaces of negative electron affinity GaAs photocathodes have been performed. One US Utility Patent was granted covering the ESR process.

DISCOVERY OF SiCSi IN IRC+10216: A MISSING LINK BETWEEN GAS AND DUST CARRIERS OF Si–C BONDS

Energy Technology Data Exchange (ETDEWEB)

Cernicharo, J.; Agúndez, M.; Prieto, L. Velilla; Quintana-Lacaci, G. [Group of Molecular Astrophysics, ICMM, CSIC, C/Sor Juana Inés de La Cruz N3, E-28049, Madrid (Spain); McCarthy, M. C.; Gottlieb, C. A.; Drumel, M. A. Martin-; Patel, N. A.; Reilly, N. J.; Young, K. H. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, and School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 (United States); Baraban, J. H. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 (United States); Changala, P. B. [JILA, National Institute of Standards and Technology and University of Colorado, and Department of Physics, University of Colorado, Boulder, CO 80309 (United States); Guélin, M. [Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, F-38406 St-Martin d’Hères (France); Kahane, C. [Universit Grenoble Alpes, IPAG, F-38000 Grenoble (France); CNRS, IPAG, F-38000 Grenoble (France); Stanton, J. F. [Institute for Theoretical Chemistry, Department of Chemistry, The University of Texas at Austin, Austin, TX 78712 (United States); Thorwirth, S. [I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln (Germany)

2015-06-10

We report the discovery in space of a disilicon species, SiCSi, from observations between 80 and 350 GHz with the IRAM 30 m radio telescope. Owing to the close coordination between laboratory experiments and astrophysics, 112 lines have now been detected in the carbon-rich star CW Leo. The derived frequencies yield improved rotational and centrifugal distortion constants up to sixth order. From the line profiles and interferometric maps with the Submillimeter Array, the bulk of the SiCSi emission arises from a region of 6″ in radius. The derived abundance is comparable to that of SiC{sub 2}. As expected from chemical equilibrium calculations, SiCSi and SiC{sub 2} are the most abundant species harboring a Si−C bond in the dust formation zone and certainly both play a key role in the formation of SiC dust grains.

Comparison of the performance of cop-coated and pt-coated radial junction n⁺p-silicon microwire-array photocathodes for the sunlight-driven reduction of water to H2(g)

DEFF Research Database (Denmark)

Roske, Christopher W.; Popczun, Eric J.; Seger, Brian

2015-01-01

-array photocathodes produced Voc = 0.44 V, Jph = 14 mA cm-2, ff = 0.46, and η = 2.9% under identical conditions. Thus, the MW geometry allows the fabrication of photocathodes entirely comprised of earth-abundant materials that exhibit performance comparable to that of devices that contain Pt....

IBC c-Si solar cells based on ion-implanted poly-silicon passivating contacts

NARCIS (Netherlands)

Yang, G.; Ingenito, A.; Isabella, O.; Zeman, M.

2016-01-01

Ion-implanted poly-crystalline silicon (poly-Si), in combination with a tunnel oxide layer, is investigated as a carrier-selective passivating contact in c-Si solar cells based on an interdigitated back contact (IBC) architecture. The optimized poly-Si passivating contacts enable low interface

Non-Cartesian Parallel Imaging Reconstruction of Undersampled IDEAL Spiral 13C CSI Data

DEFF Research Database (Denmark)

Hansen, Rie Beck; Hanson, Lars G.; Ardenkjær-Larsen, Jan Henrik

scan times based on spatial information inherent to each coil element. In this work, we explored the combination of non-cartesian parallel imaging reconstruction and spatially undersampled IDEAL spiral CSI1 acquisition for efficient encoding of multiple chemical shifts within a large FOV with high...

Study of a pure CsI crystal readout by APD for Belle II end cap ECL upgrade

Energy Technology Data Exchange (ETDEWEB)

Jin, Y., E-mail: jin@hep.phys.s.u-tokyo.ac.jp [Department of Physics, the University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033 (Japan); Aihara, H. [Department of Physics, the University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033 (Japan); Borshchev, O.V. [Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya st. 70, Moscow 117393 (Russian Federation); Epifanov, D.A. [Department of Physics, the University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033 (Japan); Ponomarenko, S.A.; Surin, N.M. [Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya st. 70, Moscow 117393 (Russian Federation)

2016-07-11

A scintillation counter consisting of a pure CsI crystal and avalanche photodiodes (Hamamatsu APD S8664-55 and S8664-1010) has been studied for the upgrade of the end cap electromagnetic calorimeter of Belle II detector. An essential increase of the light output was achieved with wavelength shifters based on nanostructured organosilicon luminophores. - Highlights: • A scintillation counter consisting of a pure CsI crystal and avalanche photodiodes has been studied. • The equivalent noise charge and equivalent noise energy of the counter have been measured. • An essential increase of the light output was achieved with wavelength shifters.

The ALICE–HMPID performance during the LHC run period 2010–2013

Energy Technology Data Exchange (ETDEWEB)

De Cataldo, Giacinto, E-mail: giacinto.decataldo@ba.infn.it

2014-12-01

The ALICE–High Momentum Particle Identification Detector (HMPID) is based on seven modules of proximity focusing Ring Imaging Cherenkov detectors. It is equipped with CsI photo-cathodes for the Cherenkov photon detection installed in multiwire proportional chambers filled with methane. It uses liquid C{sub 6}F{sub 14} as Cherenkov radiator and identifies with three sigma separation, charged π and K in the momentum range 1–3 GeV/c, and protons in the range 1.5–5 GeV/c. At the end of the first run period 2010–2013 of the Large Hadron Collider, the HMPID performance is analysed. No ageing effects of CsI photo-cathodes induced by the ion avalanches have been observed, and we do not expect to reach the charge threshold during the High Luminosity LHC run period 2019–2021. Leakages of C{sub 6}F{sub 14} in 4 out of 21 quartz radiator vessels, combined with 3 HV failing sectors out of 42, have limited the full detector acceptance to 72%. Improvements on the filling operation of the vessels should minimize further leakage. Finally, the particle identification performances are introduced using p-Pb collisions. For Pb–Pb central collisions, where purity and contamination of identified particles are extracted via a Monte Carlo simulation, the impact of the background on the pattern recognition algorithm is briefly discussed.

Longitudinal uniformity, time performances and irradiation test of pure CsI crystals

Energy Technology Data Exchange (ETDEWEB)

Angelucci, M. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Atanova, O. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Baccaro, S.; Cemmi, A. [ENEA UTTMAT-IRR, Casaccia R.C., Roma (Italy); Cordelli, M. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Donghia, R., E-mail: raffaella.donghia@lnf.infn.it [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Dipartimento di Fisica, Universitá Roma Tre, Roma (Italy); Giovannella, S.; Happacher, F.; Miscetti, S.; Sarra, I.; Soleti, S.R. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy)

2016-07-11

To study an alternative to BaF{sub 2}, as the crystal choice for the Mu2e calorimeter, 13 pure CsI crystals from Opto Materials and ISMA producers have been characterized by determining their light yield (LY) and longitudinal response uniformity (LRU), when read with a UV extended PMT. The crystals show a LY of ~100 p.e./MeV (~150 p.e./MeV) when wrapped with Tyvek and coupled to the PMT without (with) optical grease. The LRU is well represented by a linear slope that is on average δ~ −0.6%/cm. The timing performances of the Opto Materials crystal, read with a UV extended MPPC, have been evaluated with minimum ionizing particles. A timing resolution of ~330 ps (~ 440 ps) is achieved when connecting the photosensor to the MPPC with (without) optical grease. The crystal radiation hardness to a ionization dose has also been studied for one pure CsI crystal from SICCAS. After exposing it to a dose of 900 Gy, a decrease of 33% in the LY is observed while the LRU remains unchanged.

49th Annual Convention of the Computer Society of India CSI

CERN Document Server

Govardhan, A; Raju, K; Mandal, J

2015-01-01

Volume 1 contains 73 papers presented at CSI 2014: Emerging ICT for Bridging the Future: Proceedings of the 49th Annual Convention of Computer Society of India. The convention was held during 12-14, December, 2014 at Hyderabad, Telangana, India. This volume contains papers mainly focused on Fuzzy Systems, Image Processing, Software Engineering, Cyber Security and Digital Forensic, E-Commerce, Big Data, Cloud Computing and ICT applications.

Sequential C-Si Bond Formations from Diphenylsilane: Application to Silanediol Peptide Isostere Precursors

DEFF Research Database (Denmark)

Nielsen, Lone; Skrydstrup, Troels

2008-01-01

and the first new carbon-silicon bond. The next step is the reduction of this hydridosilane with lithium metal providing a silyl lithium reagent, which undergoes a highly diastereoselective addition to an optically active tert-butanesulfinimine, thus generating the second C-Si bond. This method allows...

Reactive magnetron sputtering of N-doped carbon thin films on quartz glass for transmission photocathode applications

Science.gov (United States)

Balalykin, N. I.; Huran, J.; Nozdrin, M. A.; Feshchenko, A. A.; Kobzev, A. P.; Sasinková, V.; Boháček, P.; Arbet, J.

2018-03-01

N-doped carbon thin films were deposited on a silicon substrate and quartz glass by RF reactive magnetron sputtering using a carbon target and an Ar+N2 gas mixture. During the magnetron sputtering, the substrate holder temperatures was kept at 800 °C. The carbon film thickness on the silicon substrate was about 70 nm, while on the quartz glass it was in the range 15 nm – 60 nm. The elemental concentration in the films was determined by RBS and ERD. Raman spectroscopy was used to evaluate the intensity ratios I D/I G of the D and G peaks of the carbon films. The transmission photocathodes prepared were placed in the hollow-cathode assembly of a Pierce-structure DC gun to produce photoelectrons. The quantum efficiency (QE) was calculated from the laser energy and cathode charge measured. The properties of the transmission photocathodes based on semitransparent N-doped carbon thin films on quartz glass and their potential for application in DC gun technology are discussed.

High-charge s-band photocathode RF-gun and linac system for radiation research

Energy Technology Data Exchange (ETDEWEB)

Kobayashi, Tetsuya; Uesaka, Mitsuru; Katsumura, Yousuke [Univ. of Tokyo, Graduate School of Engineering, Nuclear Engineering Research Laboratory, Tokai, Ibaraki (JP)] (and others)

2002-01-01

For sub-picosecond pump-and-prove-type radiation chemistry work, a new synchronized electron linac and laser system was installed in the Nuclear Engineering Research Laboratory (NERL) of University of Tokyo. The new laser system, with a Ti:Sapphire oscillator (795 nm) and amplifiers, generates 300 ps pulses at 10 Hz. The laser is transported through the vacuum chamber and then split into two beams. The first is compressed and converted to the third harmonics (265 nm, <250 {mu}J, 4-11 ps) so as to drive the photocathode RF-gun and generate a pump-electron beam. The second is compressed to 100 fs and used for the probe light. The high-power RF, which is provided by a new 15 MW klystron, is divided into the gun and the accelerating section. Finally, a time jitter of 330 fs (rms) was achieved between the pump-electron beam and the probe laser, which is equivalent to the design value of 320 fs. A charge of 7 nC/bunch was observed at the exit of the gun from this new laser system. Improvement of the vacuum in the gun (<10{sup -9} Torr) is the most effective way to obtain such a high-charge beam. After about three years of operation, the Cu photocathode has shown no degradation of quantum efficiency. (author)

Children and Crime Scenes: Have Schools Fallen Victim to the CSI Effect?

Science.gov (United States)

Eskriett, Angela

2011-01-01

Whilst there continues to be debate regarding the influence of the "CSI effect" upon the criminal justice system, there appears to be a general consensus that the popularisation of work within the field, particularly through a number of "procedural cop shows", has fuelled an explosion in the number of young people choosing to pursue a career in…

Epitaxial Bi2 FeCrO6 Multiferroic Thin Film as a New Visible Light Absorbing Photocathode Material.

Science.gov (United States)

Li, Shun; AlOtaibi, Bandar; Huang, Wei; Mi, Zetian; Serpone, Nick; Nechache, Riad; Rosei, Federico

2015-08-26

Ferroelectric materials have been studied increasingly for solar energy conversion technologies due to the efficient charge separation driven by the polarization induced internal electric field. However, their insufficient conversion efficiency is still a major challenge. Here, a photocathode material of epitaxial double perovskite Bi(2) FeCrO(6) multiferroic thin film is reported with a suitable conduction band position and small bandgap (1.9-2.1 eV), for visible-light-driven reduction of water to hydrogen. Photoelectrochemical measurements show that the highest photocurrent density up to -1.02 mA cm(-2) at a potential of -0.97 V versus reversible hydrogen electrode is obtained in p-type Bi(2) FeCrO(6) thin film photocathode grown on SrTiO(3) substrate under AM 1.5G simulated sunlight. In addition, a twofold enhancement of photocurrent density is obtained after negatively poling the Bi(2) FeCrO(6) thin film, as a result of modulation of the band structure by suitable control of the internal electric field gradient originating from the ferroelectric polarization in the Bi(2) FeCrO(6) films. The findings validate the use of multiferroic Bi(2) FeCrO(6) thin films as photocathode materials, and also prove that the manipulation of internal fields through polarization in ferroelectric materials is a promising strategy for the design of improved photoelectrodes and smart devices for solar energy conversion. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diffractive intermediate layer enables broadband light trapping for high efficiency ultrathin c-Si tandem cells

Energy Technology Data Exchange (ETDEWEB)

Li, Guijun, E-mail: gliad@connect.ust.hk; Ho, Jacob Y. L.; Li, He; Kwok, Hoi-Sing [State Key Laboratory on Advanced Displays and Optoelectronics Technologies, Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

2014-06-09

Light management through the intermediate reflector in the tandem cell configuration is of great practical importance for achieving high stable efficiency and also low cost production. So far, however, the intermediate reflectors employed currently are mainly focused on the light absorption enhancement of the top cell. Here, we present a diffractive intermediate layer that allows for light trapping over a broadband wavelength for the ultrathin c-Si tandem solar cell. Compared with the standard intermediate reflector, this nanoscale architectural intermediate layer results in a 35% and 21% remarkable enhancement of the light absorption in the top (400–800 nm) and bottom (800–1100 nm) cells simultaneously, and ultrathin c-Si tandem cells with impressive conversion efficiency of 13.3% are made on the glass substrate.

Diffractive intermediate layer enables broadband light trapping for high efficiency ultrathin c-Si tandem cells

International Nuclear Information System (INIS)

Li, Guijun; Ho, Jacob Y. L.; Li, He; Kwok, Hoi-Sing

2014-01-01

Light management through the intermediate reflector in the tandem cell configuration is of great practical importance for achieving high stable efficiency and also low cost production. So far, however, the intermediate reflectors employed currently are mainly focused on the light absorption enhancement of the top cell. Here, we present a diffractive intermediate layer that allows for light trapping over a broadband wavelength for the ultrathin c-Si tandem solar cell. Compared with the standard intermediate reflector, this nanoscale architectural intermediate layer results in a 35% and 21% remarkable enhancement of the light absorption in the top (400–800 nm) and bottom (800–1100 nm) cells simultaneously, and ultrathin c-Si tandem cells with impressive conversion efficiency of 13.3% are made on the glass substrate.

Metastability of a-SiO{sub x}:H thin films for c-Si surface passivation

Energy Technology Data Exchange (ETDEWEB)

Serenelli, L., E-mail: luca.serenelli@enea.it [ENEA Research centre “Casaccia”, via Anguillarese 301, 00123 Rome (Italy); DIET University of Rome “Sapienza”, via Eudossiana 18, 00184 Rome (Italy); Martini, L. [DIET University of Rome “Sapienza”, via Eudossiana 18, 00184 Rome (Italy); Imbimbo, L. [ENEA Research centre “Casaccia”, via Anguillarese 301, 00123 Rome (Italy); DIET University of Rome “Sapienza”, via Eudossiana 18, 00184 Rome (Italy); Asquini, R. [DIET University of Rome “Sapienza”, via Eudossiana 18, 00184 Rome (Italy); Menchini, F.; Izzi, M.; Tucci, M. [ENEA Research centre “Casaccia”, via Anguillarese 301, 00123 Rome (Italy)

2017-01-15

Highlights: • a-SiO{sub x}:H film deposition by RF-PECVD is optimized from SiH{sub 4}, CO{sub 2} and H{sub 2} gas mixture. • Metastability of a-SiO{sub x}:H/c-Si passivation is investigated under thermal annealing and UV exposure. • A correlation between passivation metastability and Si−H bonds is found by FTIR spectra. • A metastability model is proposed. - Abstract: The adoption of a-SiO{sub x}:H films obtained by PECVD in heterojunction solar cells is a key to further increase their efficiency, because of its transparency in the UV with respect to the commonly used a-Si:H. At the same time this layer must guarantee high surface passivation of the c-Si to be suitable in high efficiency solar cell manufacturing. On the other hand the application of amorphous materials like a-Si:H and SiN{sub x} on the cell frontside expose them to the mostly energetic part of the sun spectrum, leading to a metastability of their passivation properties. Moreover as for amorphous silicon, thermal annealing procedures are considered as valuable steps to enhance and stabilize thin film properties, when performed at opportune temperature. In this work we explored the reliability of a-SiO{sub x}:H thin film layers surface passivation on c-Si substrates under UV exposition, in combination with thermal annealing steps. Both p- and n-type doped c-Si substrates were considered. To understand the effect of UV light soaking we monitored the minority carriers lifetime and Si−H and Si−O bonding, by FTIR spectra, after different exposure times to light coming from a deuterium lamp, filtered to UV-A region, and focused on the sample to obtain a power density of 50 μW/cm{sup 2}. We found a certain lifetime decrease after UV light soaking in both p- and n-type c-Si passivated wafers according to a a-SiO{sub x}:H/c-Si/a-SiO{sub x}:H structure. The role of a thermal annealing, which usually enhances the as-deposited SiO{sub x} passivation properties, was furthermore considered. In

Design of a high charge (10 - 100 nC) and short pulse (2 - 5 ps) rf photocathode gun for wakefield acceleration

International Nuclear Information System (INIS)

Gai, W.

1998-01-01

In this paper we present a design report on a 1-1/2 cell, L Band RF photocathode gun that is capable of generating and accelerating electron beams with peak currents >10 kA. We have performed simulation for bunch intensities in the range of 10-100 nC with peak axial electrical field at the photocathode of 30-100 MV/m. Unlike conventional short electron pulse generation, this design does not require magnetic pulse compression. Based on numerical simulations using SUPERFISH and PARMELA, this design will produce 20-100 nC beam at 18 MeV with rms bunch length 0.6-1.25 mm and normalized transverse emittance 30-108 mm mrad. Applications of this beam for wakefield acceleration is also discussed

The CSI Academy: Encouraging Diverse Students to Consider Science Careers and Science Teaching

Science.gov (United States)

Kaye, Karen; Turner, John F.; Emigh, James

2011-01-01

The CSI academies employed a multi-layered, collaborative approach to encourage diverse students to consider STEM careers, including science teaching. The academies recruited a diverse group of high school students. This was due, in large part, to the creation of a unique selection process that identified students with unrealized potential. The…

Limiting efficiency of generalized realistic c-Si solar cells coupled to ideal up-converters

Science.gov (United States)

Johnson, Craig M.; Conibeer, Gavin J.

2012-11-01

The detailed balance model of photovoltaic up-conversion is revised for the specific case of a c-Si solar cell under the AM1.5G solar spectrum. The limiting efficiency of an ideal solar cell with a band gap of 1.117 eV may be increased from approximately 33% to 40% with ideal up-conversion. However, real solar cells do not demonstrate the step-function absorption characteristic assumed in the standard detailed balance model. Here, we use tabulated Si refractive index data to develop a generalized model of a realistic conventional c-Si solar cell. The model incorporates optical design and material parameters such as free carrier absorption that have a non-trivial impact on the operation of the up-conversion layer. While these modifications are shown to decrease the absolute limiting efficiency, the benefit of up-conversion is shown to be relatively greater.

Variation of carrier concentration and interface trap density in 8MeV electron irradiated c-Si solar cells

Energy Technology Data Exchange (ETDEWEB)

Bhat, Sathyanarayana, E-mail: asharao76@gmail.com; Rao, Asha, E-mail: asharao76@gmail.com [Department of Physics, Mangalore Institute of Technology and Engineering, Moodabidri, Mangalore-574225 (India); Krishnan, Sheeja [Department of Physics, Sri Devi Institute of Technology, Kenjar, Mangalore-574142 (India); Sanjeev, Ganesh [Microtron Centre, Department of Physics, Mangalore University, Mangalagangothri-574199 (India); Suresh, E. P. [Solar Panel Division, ISRO Satellite Centre, Bangalore-560017 (India)

2014-04-24

The capacitance and conductance measurements were carried out for c-Si solar cells, irradiated with 8 MeV electrons with doses ranging from 5kGy – 100kGy in order to investigate the anomalous degradation of the cells in the radiation harsh environments. Capacitance – Voltage measurements indicate that there is a slight reduction in the carrier concentration upon electron irradiation due to the creation of radiation induced defects. The conductance measurement results reveal that the interface state densities and the trap time constant increases with electron dose due to displacement damages in c-Si solar cells.

Hard X-ray photoelectron spectroscopy study for transport behavior of CsI in heating test simulating a BWR severe accident condition: Chemical effects of boron vapors

Energy Technology Data Exchange (ETDEWEB)

Okane, T., E-mail: okanet@spring8.or.jp [Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Hyogo, 679-5148 (Japan); Kobata, M. [Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Hyogo, 679-5148 (Japan); Sato, I. [Oarai Research and Development Center, Japan Atomic Energy Agency, 4002 Narita-cho, Oarai-machi, Ibaraki, 311-1393 (Japan); Kobayashi, K. [Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Hyogo, 679-5148 (Japan); Osaka, M. [Nuclear Science and Engineering Center, Japan Atomic Energy Agency, 4002 Narita-cho, Oarai-machi, Ibaraki, 311-1393 (Japan); Yamagami, H. [Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Hyogo, 679-5148 (Japan); Faculty of Science, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto, 603-8555 (Japan)

2016-02-15

Highlights: • We have clarified the temperature-dependent chemical forms of Cs/I products. • We have examined the CsI-decomposing effects of B{sub 2}O{sub 3} vapor. • The possibility of Cs re-evaporation from CsI-deposited surface is suggested. • We have demonstrated the usefulness of HAXPES on FP chemistry. - Abstract: Transport behavior of CsI in the heating test, which simulated a BWR severe accident, was investigated by hard X-ray photoelectron spectroscopy (HAXPES) with an emphasis on the chemical effect of boron vapors. CsI deposited on metal tube at temperatures ranging from 150 °C to 750 °C was reacted with vapor/aerosol B{sub 2}O{sub 3}, and the chemical form of reaction products on the sample surface was examined from the HAXPES spectra of core levels, e.g., Ni 2p, Cs 3d and I 3d levels, and valence band. For the samples at ∼300 °C, while the chemical form of major product on the sample surface without an exposure to B{sub 2}O{sub 3} was suggested to be CsI from the HAXPES spectra, an intensity ratio of Cs/I was dramatically reduced at the sample surface after the reaction with B{sub 2}O{sub 3}. The results suggest the possibility of significant decomposition of deposited CsI induced by the chemical reaction with B{sub 2}O{sub 3} at specific temperatures.

Non-conventional photocathodes based on Cu thin films deposited on Y substrate by sputtering

Energy Technology Data Exchange (ETDEWEB)

Perrone, A. [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); National Institute of Nuclear Physics and University of Salento, 73100 Lecce (Italy); D’Elia, M. [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); Gontad, F., E-mail: francisco.gontad@le.infn.it [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); National Institute of Nuclear Physics and University of Salento, 73100 Lecce (Italy); Di Giulio, M.; Maruccio, G. [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); Cola, A. [National Council Research, Institute for Microelectronics and Microsystems, 73100 Lecce (Italy); Stankova, N.E. [Institute of Electronics, Bulgarian Academy of Sciences, 1784 Sofia (Bulgaria); Kovacheva, D.G. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Broitman, E. [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)

2014-07-01

Copper (Cu) thin films were deposited on yttrium (Y) substrate by sputtering. During the deposition, a small central area of the Y substrate was shielded to avoid the film deposition and was successively used to study its photoemissive properties. This configuration has two advantages: the cathode presents (i) the quantum efficiency and the work function of Y and (ii) high electrical compatibility when inserted into the conventional radio-frequency gun built with Cu bulk. The photocathode was investigated by scanning electron microscopy to determine surface morphology. X-ray diffraction and atomic force microscopy studies were performed to compare the structure and surface properties of the deposited film. The measured electrical resistivity value of the Cu film was similar to that of high purity Cu bulk. Film to substrate adhesion was also evaluated using the Daimler–Benz Rockwell-C adhesion test method. Finally, the photoelectron performance in terms of quantum efficiency was obtained in a high vacuum photodiode cell before and after laser cleaning procedures. A comparison with the results obtained with a twin sample prepared by pulsed laser deposition is presented and discussed.

A high-gradient high-duty-factor Rf photo-cathode electron gun

International Nuclear Information System (INIS)

Rimmer, Robert A.; Hartman, Neal; Lidia, Steven M.; Wang, Shaoheng

2002-01-01

We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure

A high-gradient high-duty-factor RF photo-cathode electron gun

International Nuclear Information System (INIS)

Rimmer, Robert; Hartman, N.; Lidia, S.; Wang, S.H.

2002-01-01

We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure

Detection of Potential Induced Degradation in c-Si PV Panels Using Electrical Impedance Spectroscopy

DEFF Research Database (Denmark)

Oprea, Matei-lon; Spataru, Sergiu; Sera, Dezso

2016-01-01

This work, for the first time, investigates an Impedance Spectroscopy (IS) based method for detecting potential-induced degradation (PID) in crystalline silicon photovoltaic (c-Si PV) panels. The method has been experimentally tested on a set of panels that were confirmed to be affected by PID...

Analysis of emittance compensation and simulation results to photo-cathode RF gun

CERN Document Server

LiuShengGuang

2002-01-01

The emittance compensation technology will be used on the photo-cathode RF gun for Shanghai SDUV-FEL. The space charge force and its effect on electron beam transverse emittance in RF gun is studied, the principle of emittance compensation in phase-space is discussed. The authors have designed a compensation solenoid and calculated its magnetic field distribution. Its performance has been studied by the code PARMELA. A simulation result indicates that the normalized transverse RMS emittance for electron beam of 1.5 nC is 1.612 pi mm centre dot mrad, electron energy E = 5.71 MeV

Fission product behavior in high-temperature water: CsI vs MoO4

Science.gov (United States)

Kanjana, K.; Silva, K.; Channuie, J.

2017-09-01

Fission product behaviors of Cs, a major element released in a severe nuclear accident, still remain unclear. The question frequently addressed is whether Cs released will be in the form of Cs2MoO4 or CsOH. This is a challenging issue since it has been demonstrated that the reaction between Cs2MoO4 and water leading to CsOH production is thermodynamically favored. The present research aims at investigation of CsOH generation through this chemical channel. A high-temperature setup with a flow system based on the cooling system of a water-cooled nuclear reactor has been assembled. The reaction between aqueous solutions of CsI and Na2MoO4 in a high-corrosion-resistant hot cell (Hastelloy) has been studied up to 80 °C in deoxygenated system. The products have been characterized using FTIR and XRD. The results have shown that there is no reaction between CsI and Na2MoO4 under the experimental conditions.

Highly stable copper oxide composite as an effective photocathode for water splitting via a facile electrochemical synthesis strategy

KAUST Repository

Zhang, Zhonghai

2012-01-01

Hydrogen generation through photoelectrochemical (PEC) water splitting using solar light as an energy resource is believed to be a clean and efficient way to overcome the global energy and environmental problems. Extensive research effort has been focused on n-type metal oxide semiconductors as photoanodes, whereas studies of p-type metal oxide semiconductors as photocathodes where hydrogen is generated are scarce. In this paper, highly efficient and stable copper oxide composite photocathode materials were successfully fabricated by a facile two-step electrochemical strategy, which consists of electrodeposition of a Cu film on an ITO glass substrate followed by anodization of the Cu film under a suitable current density and then calcination to form a Cu 2O/CuO composite. The synthesized Cu 2O/CuO composite was composed of a thin layer of Cu 2O with a thin film of CuO on its top as a protecting coating. The rational control of chemical composition and crystalline orientation of the composite materials was easily achieved by varying the electrochemical parameters, including electrodeposition potential and anodization current density, to achieve an enhanced PEC performance. The best photocathode material among all materials prepared was the Cu 2O/CuO composite with Cu 2O in (220) orientation, which showed a highly stable photocurrent of -1.54 mA cm -2 at a potential of 0 V vs reversible hydrogen electrode at a mild pH under illumination of AM 1.5G. This photocurrent density was more than 2 times that generated by the bare Cu 2O electrode (-0.65 mAcm -2) and the stability was considerably enhanced to 74.4% from 30.1% on the bare Cu 2O electrode. The results of this study showed that the top layer of CuO in the Cu 2O/CuO composite not only minimized the Cu 2O photocorrosion but also served as a recombination inhibitor for the photogenerated electrons and holes from Cu 2O, which collectively explained much enhanced stability and PEC activity of the Cu 2O/CuO composite

Instruments for assessing the burden of informal caregiving for stroke patients in clinical practice: a comparison of CSI, CRA, SCQ and self-rated burden.

Science.gov (United States)

van Exel, N Job A; Scholte op Reimer, Wilma J M; Brouwer, Werner B F; van den Berg, Bernard; Koopmanschap, Marc A; van den Bos, Geertrudis A M

2004-03-01

To compare the feasibility, convergent and clinical validity of three commonly used burden scales: Caregiver Strain Index (CSI), Caregiver Reaction Assessment (CRA) and Sense of Competence Questionnaire (SCQ), with a self-developed single question on self-rated burden (SRB). Stroke patients receiving support from an informal caregiver (n = 148) and their caregivers were followed up to six months after stroke. Feasibility was assessed with several measures of missing values. Convergent validity was assessed on the basis of the correlation patterns between the burden scales, and clinical validity through evaluation of expected associations between levels of burden and explanatory patients' and caregivers' characteristics. Missing values were less often observed on CSI and SRB than SCQ and CRA. Significant correlation coefficients (p CRA. Evidence for clinical validity was strongest for CSI and SRB, based on associations between higher burden scores and patients' disability, and patients' and caregivers' poor level of health-related quality of life (all p CRA. SRB could be used for quick screening of caregivers at risk. CSI is indicated for further diagnosis of the burden of informal caregivers.

Progress in the development of photosensitive GEMs with resistive electrodes manufactured by a screen printing technology

International Nuclear Information System (INIS)

Peskov, V.; Martinengo, P.; Nappi, E.; Oliveira, R.; Paic, G.; Pietropaolo, F.; Picchi, P.

2009-01-01

An innovative photosensitive gaseous detector, consisting of a GEM-like amplification structure with double-layered electrodes (instead of commonly used metallic ones) coated with a CsI reflective photocathode, is described. In one of our latest designs, the inner electrode consists of a metallic grid and the outer one is made of resistive strips; the latter are manufactured by a screen-printing technology on the top of the metallic strips's grid The inner metallic grid is used for 2-D position measurements whereas the resistive layer provides an efficient spark-protected operation at high gains close to the breakdown limit. Detectors with active areas of 10x10 and 10x20 cm 2 were tested under various conditions including the operation in photosensitive gas mixtures containing ethylferrocene or TMAE vapors. The new technique could have many applications requiring robust and reliable large-area detectors for UV visualization, as for example, in Cherenkov imaging devices.

Photosensitive Strip RETHGEM

CERN Document Server

Peskov, Vladimir; Nappi, E.; Oliveira, R.; Paic, G.; Pietropaolo, F.; Picchi, P.

2008-01-01

An innovative photosensitive gaseous detector, consisting of a GEM like amplification structure with double layered electrodes (instead of commonly used metallic ones) coated with a CsI reflective photocathode, is described. In one of our latest designs, the inner electrode consists of a metallic grid and the outer one is made of resistive strips; the latter are manufactured by a screen printing technology on the top of the metallic strips grid The inner metallic grid is used for 2D position measurements whereas the resistive layer provides an efficient spark protected operation at high gains - close to the breakdown limit. Detectors with active areas of 10cm x10cm and 10cm x20cm were tested under various conditions including the operation in photosensitive gas mixtures containing ethylferrocene or TMAE vapors. The new technique could have many applications requiring robust and reliable large area detectors for UV visualization, as for example, in Cherenkov imaging devices.

Progress in the development of photosensitive GEMs with resistive electrodes manufactured by a screen printing technology

CERN Document Server

Peskov, V; Nappi, E; Oliveira, R; Paic, G; Pietropaolo, F; Picchi, P

2009-01-01

An innovative photosensitive gaseous detector, consisting of a GEM-like amplification structure with double-layered electrodes (instead of commonly used metallic ones) coated with a CsI reflective photocathode, is described. In one of our latest designs, the inner electrode consists of a metallic grid and the outer one is made of resistive strips; the latter are manufactured by a screen-printing technology on the top of the metallic strips's grid The inner metallic grid is used for 2-D position measurements whereas the resistive layer provides an efficient spark-protected operation at high gains close to the breakdown limit. Detectors with active areas of 10×10 and 10×20 cm2 were tested under various conditions including the operation in photosensitive gas mixtures containing ethylferrocene or TMAE vapors. The new technique could have many applications requiring robust and reliable large-area detectors for UV visualization, as for example, in Cherenkov imaging devices.

Optical concentrators for Čerenkov light detector

CERN Document Server

Kramer, Daniel

2005-01-01

RICH1 (Ring Imaging Cherenkov) detector is an important part of COMPASS particle physics experiment in CERN. Its central area photon detection part is being upgraded from wire chambers with CsI layers to very fast UV extended Hamamatsu MAPMTs (Multi Anode Photo Multiplier Tubes) array. MAPMTs have approx. 3 times smaller active area than the covered region, thus optical concentrators transforming image from old system focal plane to the new photocathode were needed. System was expected to be efficient from 200 to 600nm with best performance at 300nm and with angular acceptance including all interesting physics processes. Several design types (including i.e. a hollow waveguide) were investigated and the “telescopic” two lens aspherical design concept was selected for its proven functionality in HERA-B experiment. Chosen material was UV grade fused silica. System consists of a field lens placed in the focal plane of the RICH mirrors and a condenser lens downstream. Designing procedure started with a high op...

Imaging responses of on-site CsI and Gd2O2S flat-panel detectors: Dependence on the tube voltage

Science.gov (United States)

Jeon, Hosang; Chung, Myung Jin; Youn, Seungman; Nam, Jiho; Lee, Jayoung; Park, Dahl; Kim, Wontaek; Ki, Yongkan; Kim, Ho Kyung

2015-07-01

One of the emerging issues in radiography is low-dose imaging to minimize patient's exposure. The scintillating materials employed in most indirect flat-panel detectors show a drastic change of X-ray photon absorption efficiency around their K-edge energies that consequently affects image quality. Using various tube voltages, we investigated the imaging performance of most popular scintillators: cesium iodide (CsI) and gadolinium oxysulfide (Gd2O2S). The integrated detective quantum efficiencies (iDQE) of four detectors installed in the same hospital were evaluated according to the standardized procedure IEC 62220-1 at tube voltages of 40 - 120 kVp. The iDQE values of the Gd2O2S detectors were normalized by those of CsI detectors to exclude the effects of image postprocessing. The contrast-to-noise ratios (CNR) were also evaluated by using an anthropomorphic chest phantom. The iDQE of the CsI detector outperformed that of the Gd2O2S detector over all tube voltages. Moreover, we noted that the iDQE of the Gd2O2S detectors quickly rolled off with decreasing tube voltage under 70 kVp. The CNRs of the two scintillators were similar at 120 kVp. At 60 kVp, however, the CNR of Gd2O2S was about half that of CsI. Compared to the Gd2O2S detectors, variations in the DQE performance of the CsI detectors were relatively immune to variations in the applied tube voltages. Therefore, we claim that Gd2O2S detectors are inappropriate for use in low-tube-voltage imaging (e.g., extremities and pediatrics) with low patient exposure.

Theoretical study for heterojunction surface of NEA GaN photocathode dispensed with Cs activation

Science.gov (United States)

Xia, Sihao; Liu, Lei; Wang, Honggang; Wang, Meishan; Kong, Yike

2016-09-01

For the disadvantages of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, new-type NEA GaN photocathodes with heterojunction surface dispensed with Cs activation are investigated based on first-principle study with density functional theory. Through the growth of an ultrathin n-type GaN cap layer on p-type GaN emission layer, a p-n heterojunction is formed on the surface. According to the calculation results, it is found that Si atoms tend to replace Ga atoms to result in an n-type doped cap layer which contributes to the decreasing of work function. After the growth of n-type GaN cap layer, the atom structure near the p-type emission layer is changed while that away from the surface has no obvious variations. By analyzing the E-Mulliken charge distribution of emission surface with and without cap layer, it is found that the positive charge of Ga and Mg atoms in the emission layer decrease caused by the cap layer, while the negative charge of N atom increases. The conduction band moves downwards after the growth of cap layer. Si atom produces donor levels around the valence band maximum. The absorption coefficient of GaN emission layer decreases and the reflectivity increases caused by n-type GaN cap layer.

Measurements of Transverse Emittance for RF Photocathode Gun at the PAL

CERN Document Server

Park Jang Ho; Park, Sung-Ju; Soo Ko In; Wang, Xijie; Woon Parc, Yong; Xiang, Dao

2005-01-01

A BNL GUN-IV type RF photo-cathode gun is under fabrication for use in the FIR (Far Infra-Red) facility being built at the Pohang Accelerator Laboratory (PAL). Performance test of the gun will include the measurement of transverse emittance profile along the longitudinal direction. Successful measurement of the emittance profile will provide powerful tool for the commissioning of the 4GLS (4th generation light source) injectors based on the emittance compensation principle. We are going to achieve this withthe use of pepper-pot based emittance meters that can be moved along the longitudinal direction. In this article, we present design considerations on the emittance meter with the resolution of 1 mm mrad.

Exploring K-3 Teachers' Implementation of Comprehension Strategy Instruction (CSI) Using Expectancy-Value Theory

Science.gov (United States)

Foley, Laura S.

2011-01-01

This research investigated factors that influence the implementation levels of evidence-based comprehension strategy instruction (CSI) among K-3 teachers. An explanatory design was chosen to gather and probe the data. Quantitative data were gathered via a mailed survey distributed through a representative sample of the 40 school districts (through…

Surface and Bulk Characteristics of Cesium Iodide (CsI) coated Carbon (C) Fibers for High Power Microwave (HPM) Field Emission Cathodes

Science.gov (United States)

Vlahos, Vasilios; Morgan, Dane; Booske, John H.; Shiffler, Don

2008-11-01

CsI coated C fibers [1] are promising field emission cathodes for HPM applications. Ab initio computational modeling has shown that atomically-thin CsI coatings reduce the work function of C substrates by a surface dipole mechanism [2]. Characterization measurements of the composition and morphology of the CsI-coated C fibers are underway for determining the properties and characteristics of the following important regions of the fiber: (i) the surface on the tip of the fiber where the majority of electron emission is believed to occur, (ii) the surface covering the body of the fiber and its role on the emission properties of the system, and (iii) the interior volume of the fiber and its effects on the CsI surface re-supply process and rate. The results will be interpreted in terms of surface electronic properties and theoretical electron emission models. [1]D. Shiffler, et al., Phys. Plasmas 11 (2004) 1680. [2]V.Vlahos et al., Appl. Phys. Lett. 91 (2007) 144102.

Spatial decoupling of light absorption and catalytic activity of Ni-Mo-loaded high-aspect-ratio silicon microwire photocathodes

Science.gov (United States)

Vijselaar, Wouter; Westerik, Pieter; Veerbeek, Janneke; Tiggelaar, Roald M.; Berenschot, Erwin; Tas, Niels R.; Gardeniers, Han; Huskens, Jurriaan

2018-03-01

A solar-driven photoelectrochemical cell provides a promising approach to enable the large-scale conversion and storage of solar energy, but requires the use of Earth-abundant materials. Earth-abundant catalysts for the hydrogen evolution reaction, for example nickel-molybdenum (Ni-Mo), are generally opaque and require high mass loading to obtain high catalytic activity, which in turn leads to parasitic light absorption for the underlying photoabsorber (for example silicon), thus limiting production of hydrogen. Here, we show the fabrication of a highly efficient photocathode by spatially and functionally decoupling light absorption and catalytic activity. Varying the fraction of catalyst coverage over the microwires, and the pitch between the microwires, makes it possible to deconvolute the contributions of catalytic activity and light absorption to the overall device performance. This approach provided a silicon microwire photocathode that exhibited a near-ideal short-circuit photocurrent density of 35.5 mA cm-2, a photovoltage of 495 mV and a fill factor of 62% under AM 1.5G illumination, resulting in an ideal regenerative cell efficiency of 10.8%.

CSI Web Adventures: A Forensics Virtual Apprenticeship for Teaching Science and Inspiring STEM Careers

Science.gov (United States)

Miller, Leslie; Chang, Ching-I; Hoyt, Daniel

2010-01-01

CSI: The Experience, a traveling museum exhibit and a companion web adventure, was created through a grant from the National Science Foundation as a potential model for informal learning. The website was designed to enrich and complement the exhibit by modeling the forensic process. Substantive science, real-world lab techniques, and higher-level…

Adaptación del Inventario de Estrategias de Afrontamiento (CSI a la población penitenciaria de Mexico

Directory of Open Access Journals (Sweden)

Francisco Javier Rodríguez-Díaz

2014-01-01

Full Text Available El objetivo del estudio es adaptar el CSI - Inventario de Estrategias de Afrontamiento - al contexto penitenciario. La muestra - 261 penados, 97% varones (n=253 - del Sistema Postpenitenciario y Atención a Liberados (DSPAL del Estado Jalisco, México. Los instrumentos utilizados: Ficha Penitenciaria de Historia de Vida y el Inventario CSI. Los resultados refieren una estructura de primer orden casi idéntica a la obtenida para la población general, con niveles de consistencia interna satisfactorios, al mismo tiempo que la interpretación de segundo orden no confirma la estructura de segundo y tercer orden. Se discuten las implicaciones de los resultados para intervención penitenciaria.

Experimental study on the production of high density electron bunches from a GaAs photocathode

International Nuclear Information System (INIS)

Calabrese, R.; Masoli, F.; Gong, J.M.; Guidi, V.; Tecchio, L.

1991-01-01

In order to obtain a high charge, low emittance electron source, useful for FEL electron injector and for e + e - collider experiments, we performed a test experiment on a gallium arsenide photocathode, activated by negative electron affinity technique and illuminated with a 10 ns long laser pulse of 532 nm wavelength. We measured a maximum charge delivered, at relatively low potentials, of about 18 nC/bunch. The mean lifetime is greater than 60 h. (orig.)

The Chemistry Scoring Index (CSI: A Hazard-Based Scoring and Ranking Tool for Chemicals and Products Used in the Oil and Gas Industry

Directory of Open Access Journals (Sweden)

Tim Verslycke

2014-06-01

Full Text Available A large portfolio of chemicals and products is needed to meet the wide range of performance requirements of the oil and gas industry. The oil and gas industry is under increased scrutiny from regulators, environmental groups, the public, and other stakeholders for use of their chemicals. In response, industry is increasingly incorporating “greener” products and practices but is struggling to define and quantify what exactly constitutes “green” in the absence of a universally accepted definition. We recently developed the Chemistry Scoring Index (CSI which is ultimately intended to be a globally implementable tool that comprehensively scores and ranks hazards to human health, safety, and the environment for products used in oil and gas operations. CSI scores are assigned to products designed for the same use (e.g., surfactants, catalysts on the basis of product composition as well as intrinsic hazard properties and data availability for each product component. As such, products with a lower CSI score within a product use group are considered to have a lower intrinsic hazard compared to other products within the same use group. The CSI provides a powerful tool to evaluate relative product hazards; to review and assess product portfolios; and to aid in the formulation of products.

Enhanced photocathodic protection performance of Ag/graphene/TiO2 composite for 304SS under visible light

Science.gov (United States)

Li, Hong; Wang, Xiutong; Wei, Qinyi; Liu, Xueqing; Qian, Zhouhai; Hou, Baorong

2017-06-01

Ag and graphene co-sensitized TiO2 composites were successfully fabricated and used as photoanodes for photogenerated cathodic protection of 304 stainless steel (304SS) under visible light. Graphene films was firstly deposited onto the TiO2 nanotube (NT) films via cyclic voltammetric electrodeposition. Ag/graphene/TiO2 films were then fabricated via dipping and photoreduction method. The morphology, composition and optical response of the Ag/graphene/TiO2 NT composites were characterized by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, UV-vis diffusion reflectance spectroscopy, respectively. The photocathodic protection performance of the Ag/graphene/TiO2 composites were systematically studied through open-circuit potential and potentiodynamic polarization measurements in 3.5 wt% NaCl solution under visible light (λ > 400 nm). The composites exhibited enhanced photogenerated cathodic protection performance for 304SS under visible light irradiation compared to pure TiO2. Graphene and Ag have a synergistic effect on the enhancement of photocathodic protection performance of TiO2. The composites prepared with 30-cycle graphene film and 15 mM AgNO3 solution showed the optimal corrosion protection performance.

Environmental Disclosure of Electric Power Companies Listed in the Corporate Sustainability Index (CSI

Directory of Open Access Journals (Sweden)

Clésia Ana Gubiani

2012-12-01

Full Text Available The study aimed to verify the level of disclosure of environmental information in the administration reports of the energy companies listed in the Corporate Sustainability Index (CSI. A descriptive and quantitative research was done, using the content analysis technique on the administration reports from 2006 to 2008. The sample consisted of 11 electric power companies listed in the CSI. For quantitative analysis of the disclosure index, the data collection instrument was based on the study of Rover, Murcia and Borba (2008, which proposes eight environmental categories and 36 subcategories. For the whole analysis of the data were elaborated networks of the items disclosed in each company, using the software UNICET ®. The survey results showed that there is satisfactory disclosure in the categories of environmental policies and education, training and research environment. However, it was found that there is need for greater disclosure of categories of products impacts and processes in the environment, power polices and financial environmental information. It was concluded that the information disclosed in the administration reports of the companies surveyed about the environmental information do not respect the principle of full disclosure.

The GLAST Large Area Telescope Detector Performance Monitoring

International Nuclear Information System (INIS)

Borgland, A.W.; Charles, E.; SLAC

2007-01-01

The Large Area Telescope (LAT) is one of two instruments on board the Gamma-ray Large Area Telescope (GLAST), the next generation high energy gamma-ray space telescope. The LAT contains sixteen identical towers in a four-by-four grid. Each tower contains a silicon-strip tracker and a CsI calorimeter that together will give the incident direction and energy of the pair-converting photon in the energy range 20 MeV - 300 GeV. In addition, the instrument is covered by a finely segmented Anti-Coincidence Detector (ACD) to reject charged particle background. Altogether, the LAT contains more than 864k channels in the trackers, 1536 CsI crystals and 97 ACD plastic scintillator tiles and ribbons. Here we detail some of the strategies and methods for how we are planning to monitor the instrument performance on orbit. It builds on the extensive experience gained from Integration and Test and Commissioning of the instrument on ground

Back scattering involving embedded silicon nitride (SiN) nanoparticles for c-Si solar cells

Science.gov (United States)

Ghosh, Hemanta; Mitra, Suchismita; Siddiqui, M. S.; Saxena, A. K.; Chaudhuri, Partha; Saha, Hiranmay; Banerjee, Chandan

2018-04-01

A novel material, structure and method of synthesis for dielectric light trapping have been presented in this paper. First, the light scattering behaviour of silicon nitride nanoparticles have been theoretically studied in order to find the optimized size for dielectric back scattering by FDTD simulations from Lumerical Inc. The optical results have been used in electrical analysis and thereby, estimate the effect of nanoparticles on efficiency of the solar cells depending on substrate thickness. Experimentally, silicon nitride (SiN) nanoparticles have been formed using hydrogen plasma treatment on SiN layer deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD). The size and area coverage of the nanoparticles were controlled by varying the working pressure, power density and treatment duration. The nanoparticles were integrated with partial rear contact c-Si solar cells as dielectric back reflector structures for the light trapping in thin silicon solar cells. Experimental results revealed the increases of current density by 2.7% in presence of SiN nanoparticles.

Two-color spatial and temporal temperature measurements using a streaked soft x-ray imager

Energy Technology Data Exchange (ETDEWEB)

Moore, A. S., E-mail: alastair.moore@physics.org; Ahmed, M. F.; Soufli, R.; Pardini, T.; Hibbard, R. L.; Bailey, C. G.; Bell, P. M.; Hau-Riege, S. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551-0808 (United States); Benstead, J.; Morton, J.; Guymer, T. M.; Garbett, W. J.; Rubery, M. S.; Skidmore, J. W. [Directorate Science and Technology, AWE Aldermaston, Reading RG7 4PR (United Kingdom); Bedzyk, M.; Shoup, M. J.; Regan, S. P.; Agliata, T.; Jungquist, R. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Schmidt, D. W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); and others

2016-11-15

A dual-channel streaked soft x-ray imager has been designed and used on high energy-density physics experiments at the National Ignition Facility. This streaked imager creates two images of the same x-ray source using two slit apertures and a single shallow angle reflection from a nickel mirror. Thin filters are used to create narrow band pass images at 510 eV and 360 eV. When measuring a Planckian spectrum, the brightness ratio of the two images can be translated into a color-temperature, provided that the spectral sensitivity of the two images is well known. To reduce uncertainty and remove spectral features in the streak camera photocathode from this photon energy range, a thin 100 nm CsI on 50 nm Al streak camera photocathode was implemented. Provided that the spectral shape is well-known, then uncertainties on the spectral sensitivity limits the accuracy of the temperature measurement to approximately 4.5% at 100 eV.

Downlink Linear Precoders Based on Statistical CSI for Multicell MIMO-OFDM

Directory of Open Access Journals (Sweden)

Ebrahim Baktash

2017-01-01

Full Text Available With 5G communication systems on the horizon, efficient interference management in heterogeneous multicell networks is more vital than ever. This paper investigates the linear precoder design for downlink multicell multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM systems, where base stations (BSs coordinate to reduce the interference across space and frequency. In order to minimize the overall feedback overhead in next-generation systems, we consider precoding schemes that require statistical channel state information (CSI only. We apply the random matrix theory to approximate the ergodic weighted sum rate of the system with a closed form expression. After formulating the approximation for general channels, we reduce the results to a more compact form using the Kronecker channel model for which several multicarrier concepts such as frequency selectivity, channel tap correlations, and intercarrier interference (ICI are rigorously represented. We find the local optimal solution for the maximization of the approximate rate using a gradient method that requires only the covariance structure of the MIMO-OFDM channels. Within this covariance structure are the channel tap correlations and ICI information, both of which are taken into consideration in the precoder design. Simulation results show that the rate approximation is very accurate even for very small MIMO-OFDM systems and the proposed method converges rapidly to a near-optimal solution that competes with networked MIMO and precoders based on instantaneous full CSI.

Radiation hardness test of un-doped CsI crystals and Silicon Photomultipliers for the Mu2e calorimeter

Science.gov (United States)

Baccaro, S.; Cemmi, A.; Cordelli, M.; Diociaiuti, E.; Donghia, R.; Giovannella, S.; Loreti, S.; Miscetti, S.; Pillon, M.; Sarra, I.

2017-11-01

The Mu2e calorimeter is composed by 1400 un-doped CsI crystals coupled to large area UV extended Silicon Photomultipliers arranged in two annular disks. This calorimeter has to provide precise information on energy, timing and position. It should also be fast enough to handle the high rate background and it must operate and survive in a high radiation environment. Simulation studies estimated that, in the hottest regions, each crystal will absorb a dose of 300 Gy and will be exposed to a neutron fluency of 6 × 1011 n/cm2 in 3 years of running. Test of un-doped CsI crystals irradiated up to 900 Gy and to a neutron fluency up to 9 × 1011 n/cm2 have been performed at CALLIOPE and FNG ENEA facilities in Italy. We present our study on the variation of light yield (LY) and longitudinal response uniformity (LRU) of these crystals after irradiation. The ionization dose does not modify LRU while a 20% reduction in LY is observed at 900 Gy. Similarly, the neutron flux causes an acceptable LY deterioration (≤ 15%). A neutron irradiation test on different types of SIPMs (two different array models from Hamamatsu and one from FBK) have also been carried out by measuring the variation of the leakage current and the charge response to an ultraviolet led. We concluded that, in the experiment, we will need to cool down the SIPMs to 0 °C reduce the leakage current to an acceptable level.

A self-calibrating ion beam profiler based on a CsI scintillator

Energy Technology Data Exchange (ETDEWEB)

Finocchiaro, P. E-mail: finocchiaro@lns.infn.it; Ciavola, G.; Cosentino, L.; Gu, M.; Raia, G.; Rovelli, A

1999-11-21

We report on the test results obtained with a prototype beam profiler based on a thin slit and a CsI scintillator, read out by means of a compact photomultiplier. Such a device has proven to be suitable to perform ion beam diagnostics at low and very low intensities. In particular, our device is suitable for being used in the energy and intensity ranges expected at the EXCYT radioactive ion beam facility, that is currently under development at LNS Catania.

A self-calibrating ion beam profiler based on a CsI scintillator

International Nuclear Information System (INIS)

Finocchiaro, P.; Ciavola, G.; Cosentino, L.; Gu, M.; Raia, G.; Rovelli, A.

1999-01-01

We report on the test results obtained with a prototype beam profiler based on a thin slit and a CsI scintillator, read out by means of a compact photomultiplier. Such a device has proven to be suitable to perform ion beam diagnostics at low and very low intensities. In particular, our device is suitable for being used in the energy and intensity ranges expected at the EXCYT radioactive ion beam facility, that is currently under development at LNS Catania

Optical properties of CsI single crystals irradiated with neutrons at low temperature

International Nuclear Information System (INIS)

Okada, M.; Atobe, K.; Itatani, N.; Ozawa, K.

1998-01-01

Optical properties of the irradiation-induced-defects in neutron-irradiated CsI single crystals have been investigated. The nominally pure CsI crystals are irradiated by reactor fast neutrons (E>0.1 MeV) with a fluence of 1.4 x 10 15 n/cm 2 at 20 K and by γ-rays from 60 Co source to a dose of 1.5 x 10 4 Gy at liquid nitrogen temperature (LNT). After the irradiations, isochronal annealings are performed to investigate the thermal behavior of the defects. The glow peaks of the thermoluminescence (TL) in each sample irradiated with neutrons at 20 K and with γ-rays at LNT are observed at about 100, 160 and 220 K. In the neutron-irradiated samples at 20 K, the emission band at 338 nm is observed at LNT. It is supposed that this emission band occurs by an excitation of γ-rays from 134 Cs, which is radioactivated by thermal neutrons among the reactor radiations. It is confirmed that the temperature dependence of the 338 nm band is similar with that of the emission band due to the self-trapped exciton which is introduced into the non-irradiated samples illuminated by higher energy photons. (orig.)

Optical properties of CsI single crystals irradiated with neutrons at low temperature

Energy Technology Data Exchange (ETDEWEB)

Okada, M. [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.; Nakagawa, M. [Faculty of Education, Kagawa Univ., Takamatsu, Kagawa (Japan); Atobe, K. [Faculty of Science, Naruto Univ. of Education, Naruto, Tokushima (Japan); Itatani, N.; Ozawa, K. [Horiba Ltd., Minamiku, Kyoto (Japan)

1998-05-01

Optical properties of the irradiation-induced-defects in neutron-irradiated CsI single crystals have been investigated. The nominally pure CsI crystals are irradiated by reactor fast neutrons (E>0.1 MeV) with a fluence of 1.4 x 10{sup 15} n/cm{sup 2} at 20 K and by {gamma}-rays from {sup 60}Co source to a dose of 1.5 x 10{sup 4} Gy at liquid nitrogen temperature (LNT). After the irradiations, isochronal annealings are performed to investigate the thermal behavior of the defects. The glow peaks of the thermoluminescence (TL) in each sample irradiated with neutrons at 20 K and with {gamma}-rays at LNT are observed at about 100, 160 and 220 K. In the neutron-irradiated samples at 20 K, the emission band at 338 nm is observed at LNT. It is supposed that this emission band occurs by an excitation of {gamma}-rays from {sup 134}Cs, which is radioactivated by thermal neutrons among the reactor radiations. It is confirmed that the temperature dependence of the 338 nm band is similar with that of the emission band due to the self-trapped exciton which is introduced into the non-irradiated samples illuminated by higher energy photons. (orig.) 13 refs.

Two-way CSI-assisted AF relaying with HPA nonlinearity

KAUST Repository

Qi, Jian

2015-09-11

In this paper, we investigate half-duplex two-way dual-hop channel state information (CSI)-assisted amplify-andforward (AF) relaying in the presence of high-power amplifier (HPA) nonlinearity at relays. The expression for the end-toend signal-to-noise ratio (SNR) is derived as per the modified system model by taking into account the interference caused by relaying scheme and HPA nonlinearity. The system performance of the considered relaying network is evaluated in terms of average symbol error probability (SEP) in Nakagami-m fading channels, by making use of the moment-generating function (MGF) approach. Numerical results are provided and show the effects of several parameters, such as quadrature amplitude modulation (QAM) order, number of relays, HPA parameters, and Nakagami parameter, on performance. © 2015 IEEE.

A new two-step tuning procedure for a photocathode gun

International Nuclear Information System (INIS)

Lal, Shankar; Pant, K.K.; Krishnagopal, S.

2008-01-01

An important aspect of the development of multi-cell RF accelerating structures is tuning the resonant frequency f of the operating mode, field balance e b , and waveguide to cavity coupling coefficient β to the desired values. Earlier theoretical analyses have not been able to predict all three parameters simultaneously for a coupled-cavity system. We have developed a generalized circuit analysis to predict f, e b , and β of a coupled structure, based on the RF properties of the individual, uncoupled, cells. This has been used to develop a simplified two-step tuning procedure to tune a BNL/SLAC/UCLA type 1.6 cell S-band photocathode gun by varying RF properties of individual half and full cells, which are easily measurable. This procedure has been validated by tuning two true-to-scale prototypes made of aluminum and ETP copper to the desired values of the RF parameters

On the c-Si surface passivation mechanism by the negative-charge-dielectric Al2O3

NARCIS (Netherlands)

Hoex, B.; Gielis, J.J.H.; Sanden, van de M.C.M.; Kessels, W.M.M.

2008-01-01

Al2 O3 is a versatile high- ¿ dielectric that has excellent surface passivation properties on crystalline Si (c-Si), which are of vital importance for devices such as light emitting diodes and high-efficiency solar cells. We demonstrate both experimentally and by simulations that the surface

Beam dynamics simulations in the photo-cathode RF gun for the CLIC test facility

International Nuclear Information System (INIS)

Marchand, P.; Rinolfi, L.

1992-01-01

The CERN CLIC Test Facility (CTF) uses an RF gun with a laser driven photo-cathode in order to generate electron pulses of high charge (≥10 nC) and short duration (≤20 ps). The RF gun consists of a 3 GHz 1 + 1/2 cell cavity based on the design originally proposed at BNL which minimizes the non-linearities in the transverse field. The beam dynamics in the cavity is simulated by means of the multiparticle tracking code PARMELA. The results are compared to previous simulations as well as to the first experimental data. (author). 4 refs., 4 tabs., 4 figs

An application of CCD read-out technique to neutron distribution measurement using the self-activation method with a CsI scintillator plate

International Nuclear Information System (INIS)

Nohtomi, Akihiro; Kurihara, Ryosuke; Kinoshita, Hiroyuki; Honda, Soichiro; Tokunaga, Masaaki; Uno, Heita; Shinsho, Kiyomitsu; Wakabayashi, Genichiro; Koba, Yusuke; Fukunaga, Junichi; Umezu, Yoshiyuki; Nakamura, Yasuhiko; Ohga, Saiji

2016-01-01

In our previous paper, the self-activation of an NaI scintillator had been successfully utilized for detecting photo-neutrons around a high-energy X-ray radiotherapy machine; individual optical pulses from the self-activated scintillator are read-out by photo sensors such as a photomultiplier tube (PMT). In the present work, preliminary observations have been performed in order to apply a direct CCD read-out technique to the self-activation method with a CsI scintillator plate using a Pu-Be source and a 10-MV linac. In conclusion, it has been revealed that the CCD read-out technique is applicable to neutron measurement around a high-energy X-ray radiotherapy machine with the self-activation of a CsI plate. Such application may provide a possibility of novel method for simple neutron dose-distribution measurement. - Highlights: • Preliminary observations have been performed by a CCD for the CsI self-activation method. • It has been revealed that the CCD read-out technique is applicable to neutron measurement. • Such application may provide a novel method for simple neutron distribution measurement.

An application of CCD read-out technique to neutron distribution measurement using the self-activation method with a CsI scintillator plate

Energy Technology Data Exchange (ETDEWEB)

Nohtomi, Akihiro, E-mail: nohtomi@hs.med.kyushu-u.ac.jp [Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan); Kurihara, Ryosuke; Kinoshita, Hiroyuki; Honda, Soichiro; Tokunaga, Masaaki; Uno, Heita [Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan); Shinsho, Kiyomitsu [Graduate School of Human Sciences, Tokyo Metropolitan University, 7-2-10 Higashi-oku, Arakawa-ku, Tokyo 116-8551 (Japan); Wakabayashi, Genichiro [Atomic Energy Research Institute, Kinki University, 3-4-1 Kowakae, Higashiosaka-shi, Osaka 577-8502 (Japan); Koba, Yusuke [National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba-shi, Chiba 263-8555 (Japan); Fukunaga, Junichi; Umezu, Yoshiyuki; Nakamura, Yasuhiko [Department of Radiology, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan); Ohga, Saiji [Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan)

2016-10-01

In our previous paper, the self-activation of an NaI scintillator had been successfully utilized for detecting photo-neutrons around a high-energy X-ray radiotherapy machine; individual optical pulses from the self-activated scintillator are read-out by photo sensors such as a photomultiplier tube (PMT). In the present work, preliminary observations have been performed in order to apply a direct CCD read-out technique to the self-activation method with a CsI scintillator plate using a Pu-Be source and a 10-MV linac. In conclusion, it has been revealed that the CCD read-out technique is applicable to neutron measurement around a high-energy X-ray radiotherapy machine with the self-activation of a CsI plate. Such application may provide a possibility of novel method for simple neutron dose-distribution measurement. - Highlights: • Preliminary observations have been performed by a CCD for the CsI self-activation method. • It has been revealed that the CCD read-out technique is applicable to neutron measurement. • Such application may provide a novel method for simple neutron distribution measurement.

High Performance of Manganese Porphyrin Sensitized p-Type CuFe2O4 Photocathode for Solar Water Splitting to Produce Hydrogen in a Tandem Photoelectrochemical Cell

Directory of Open Access Journals (Sweden)

Xia Li

2018-03-01

Full Text Available A novel composite composed of (5, 10, 15, 20-tetraphenyl porphinato manganese sensitized p-type CuFe2O4 was developed for constructing the photocathode of a tandem photoelectrochemical (PEC cell. The prepared material was characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, X-ray photoelectron spectroscopy (XPS and UV-vis diffuse reflectance spectroscopy (DRS. Light-driven water splitting to produce hydrogen can be achieved through the PEC cell, and the results show that H2 and O2 can be collected separately at low applied bias. This work demonstrates that manganese porphyrin sensitized CuFe2O4 is an effective hybrid material for building the photocathode of a PEC cell for solar water splitting to produce H2.

Solution-deposited F:SnO₂/TiO₂ as a base-stable protective layer and antireflective coating for microtextured buried-junction H₂-evolving Si photocathodes.

Science.gov (United States)

Kast, Matthew G; Enman, Lisa J; Gurnon, Nicholas J; Nadarajah, Athavan; Boettcher, Shannon W

2014-12-24

Protecting Si photocathodes from corrosion is important for developing tandem water-splitting devices operating in basic media. We show that textured commercial Si-pn(+) photovoltaics protected by solution-processed semiconducting/conducting oxides (plausibly suitable for scalable manufacturing) and coupled to thin layers of Ir yield high-performance H2-evolving photocathodes in base. They also serve as excellent test structures to understand corrosion mechanisms and optimize interfacial electrical contacts between various functional layers. Solution-deposited TiO2 protects Si-pn(+) junctions from corrosion for ∼24 h in base, whereas junctions protected by F:SnO2 fail after only 1 h of electrochemical cycling. Interface layers consisting of Ti metal and/or the highly doped F:SnO2 between the Si and TiO2 reduce Si-emitter/oxide/catalyst contact resistance and thus increase fill factor and efficiency. Controlling the oxide thickness led to record photocurrents near 35 mA cm(-2) at 0 V vs RHE and photocathode efficiencies up to 10.9% in the best cells. Degradation, however, was not completely suppressed. We demonstrate that performance degrades by two mechanisms, (1) deposition of impurities onto the thin catalyst layers, even from high-purity base, and (2) catastrophic failure via pinholes in the oxide layers after several days of operation. These results provide insight into the design of hydrogen-evolving photoelectrodes in basic conditions, and highlight challenges.

Flat-beam Rf photocathode sources for linear collider applications

International Nuclear Information System (INIS)

Rosenzweig, J.B.

1991-01-01

Laser driven rf photocathodes represent a recent advance in high-brightness electron beam sources. The authors investigate here a variation on these devices, that obtained by using a ribbon laser pulse to illuminate the cathode, yielding a flat beam (σ x much-gt σ y ) which has asymmetric emittances at the cathode proportional to the beam size each transverse dimension. The flat-beam geometry mitigates space charge forces which lead to intensity dependent transverse and longitudinal emittance growth, thus limiting the beam brightness. The fundamental limit on achievable emittance and brightness is set by the transverse momentum distribution and peak current density of the photoelectrons (photon energy and cathode material dependent effects) and appears to allow, taking into account space charge and rf effects, normalized emittances ε x -5 m-rad and ε -6 m-rad, with Q = 5 nC and σ z = 1 mm. These source emittances are adequate for superconducting linear collider applications, and could preclude the use of a damping ring for the electrons in these schemes

Modeling of Diamond Field-Emitter-Arrays for high brightness photocathode applications

Science.gov (United States)

Kwan, Thomas; Huang, Chengkun; Piryatinski, Andrei; Lewellen, John; Nichols, Kimberly; Choi, Bo; Pavlenko, Vitaly; Shchegolkov, Dmitry; Nguyen, Dinh; Andrews, Heather; Simakov, Evgenya

2017-10-01

We propose to employ Diamond Field-Emitter-Arrays (DFEAs) as high-current-density ultra-low-emittance photocathodes for compact laser-driven dielectric accelerators capable of generating ultra-high brightness electron beams for advanced applications. We develop a semi-classical Monte-Carlo photoemission model for DFEAs that includes carriers' transport to the emitter surface and tunneling through the surface under external fields. The model accounts for the electronic structure size quantization affecting the transport and tunneling process within the sharp diamond tips. We compare this first principle model with other field emission models, such as the Child-Langmuir and Murphy-Good models. By further including effects of carrier photoexcitation, we perform simulations of the DFEAs' photoemission quantum yield and the emitted electron beam. Details of the theoretical model and validation against preliminary experimental data will be presented. Work ssupported by LDRD program at LANL.

The Present Development of CsI Rich Detectors for the ALICE Experiment at CERN

CERN Document Server

Nappi, E; Colonna, N; Di Mauro, A; Elia, D; Galantucci, L; Ghidini, B; Grimaldi, A; Goret, B; Monno, E; Paic, G; Piuz, François; Posa, F; Raynaud, J; Santiard, Jean-Claude; Tomasicchio, G; Williams, T D; Ljubicic, A; Tustonic, T; Stucchi, S

1999-01-01

The ALICE Collaboration plans to implement a 12m^2 array consisting of 7 proximity focussed C6F^14 liquid radiator RICH modules devoted to the particle identification in the momentum range: 1 GeV/c - 3.5 GeV/c for pions and kaons. A large area CSI-RICH prototype has been designed and built with the aim to validate the detector parameter assumptions made to predict the performance of the High Momentum Particle Identification System (HMPID) of the ALICE Experiment. The main elements of the prototype will be described with emphasis on the engineering solutions adopted. First results from the analysis of multitrack events recorded with this prototype exposed to hadron beams at the CERN SPS will be discussedList of FiguresFigure 1 General view of the ALICE lay-outFigure 2 Schematic layout of the fast CsI-RICHFigure 3 Perspective view of the HMPID layout with the seven RICH modules tilted according to their position with respect to the interaction vertex. The frame that supports the detectors is also shownFigure 4 ...

X-ray image intensifier for cardiovascular diagnosis. Development of RTP 9203 B-P4 and evaluation of image quality

Energy Technology Data Exchange (ETDEWEB)

Obata, Y; Suzuki, A; Noji, T; Harao, N [Toshiba Corp., Kawasaki, Kanagawa (Japan)

1979-07-01

The high utility of 35-mm cine fluorography with high-quality X-ray image intensifier has recently been acknowledged in the field of cardiovascular diagnosis. The newly developed 9-inch dual-field X-ray image intensifier is particularly suitable for 35-mm cinefluorography. The main characteristics of this tube are the increased contrast, brightness and resolution of images and the reduced quantum noise. These characteristics are caused by the CsI input phosphor screen which has a ''light-guide effect'', a high-sensitivity photocathode and a dark output screen. The tube is equipped with a high-voltage power supply with high reliability.

The Successful Operation of Hole-type Gaseous Detectors at Cryogenic Temperatures

CERN Document Server

Pereiale, L.; Iacobaeus, C.; Francke, T.; Lund-Jensen, B.; Pavlopoulos, P.; Picchi, P.; Pietropaolo, F.; Tokanai, F.

2004-01-01

We have demonstrated that hole-type gaseous detectors, GEMs and capillary plates, can operate up to 77 K. For example, a single capillary plate can operate at gains of above 10E3 in the entire temperature interval between 300 until 77 K. The same capillary plate combined with CsI photocathodes could operate perfectly well at gains (depending on gas mixtures) of 100-1000. Obtained results may open new fields of applications for capillary plates as detectors of UV light and charge particles at cryogenic temperatures: noble liquid TPCs, WIMP detectors or LXe scintillating calorimeters and cryogenic PETs.

An integrated photosensor readout for gas proportional scintillation counters

International Nuclear Information System (INIS)

Lopes, J.A.M.; Santos, J.M.F. dos; Conde, C.A.N.

1996-01-01

A xenon gas proportional scintillation counter has been instrumented with a novel photosensor that replaces the photomultiplier tube normally used to detect the VUV secondary scintillation light. In this implementation, the collection grid of a planar gas proportional scintillation counter also functions as a multiwire proportional chamber to amplify and detect the photoelectrons emitted by a reflective CsI photocathode in direct contact with the xenon gas. This integrated concept combines greater simplicity, compactness, and ruggedness (no optical window is used) with low power consumption. An energy resolution of 12% was obtained for 59.6 keV x-rays

Atomic-layer deposited Nb2O5 as transparent passivating electron contact for c-Si solar cells

NARCIS (Netherlands)

Macco, Bart; Black, Lachlan E.; Melskens, Jimmy; van de Loo, Bas W.H.; Berghuis, Willem Jan H.; Verheijen, Marcel A.; Kessels, Wilhelmus M.M.

2018-01-01

Passivating contacts based on metal oxides have proven to enable high energy conversion efficiencies for crystalline silicon (c-Si) solar cells at low processing complexity. In this work, the potential of atomic-layer deposited (ALD) Nb2O5 as novel electron-selective passivating contact is explored

Photocathodes inside superconducting cavities. Studies on the feasibility of a superconducting photoelectron source of high brightness. External report

International Nuclear Information System (INIS)

Michalke, A.

1992-01-01

We have done studies and experiments to explore the feasibility of a photoemission RF gun with a superconducting accelerator cavity. This concept promises to provide an electron beam of high brightness in continuous operation. It is thus of strong interest for a free-electron-laser or a linear collider based on a superconducting accelerator. In a first step we studied possible technical solutions for its components, especially the material of the photocathode and the geometrical shape of the cavity. Based on these considerations, we developed the complete design for a prototype electron source. The cathode material was chosen to be alkali antimonide. In spite of its sensitivity, it seems to be the best choice for a gun with high average current due to its high quantum efficiency. The cavity shape was at first a reentrant-type single cell of 500 MHz. It is now replaced by a more regular two-and-half cell shape, an independent half cell added for emittance correction. Its beam dynamics properties are investigated by numerical simulations; we estimated a beam brightness of about 5x10 11 A/(m.rad) 2 . But the mutual interactions between alkali antimonide photocathode and superconducting cavity must be investigated experimentally, because they are completely unkown. (orig.)

Formation of a p-n heterojunction on GaP photocathodes for H-2 production providing an open-circuit voltage of 710 mV

DEFF Research Database (Denmark)

Malizia, Mauro; Seger, Brian; Chorkendorff, Ib

2014-01-01

Photocatalytic water splitting for the sustainable production of hydrogen using a two-photon tandem device requires careful optimization of the semiconductors used as photon absorbers. In this work we show how the open-circuit voltage of photocathodes for the hydrogen evolution reaction based on ...

[The CSI effect and its impact on the perceptions of forensic science experts' work].

Science.gov (United States)

Stojer, Joanna

2011-01-01

The issue that has been analyzed in this work is the potential effect of crime films and TV series on people's perceptions of forensic medicine and science, and especially on the forming of expectations towards forensic science experts. This syndrome is being called the "CSI effect" after the popular franchise Crime Scene Investigation (CSI). Questionnaire surveys that have been conducted included "experts": 50 experts in various specialities, 77 prosecutors, 119 judges, 64 lay judges, 161 police staff and 80 members of general public. In-depth interviews have been conducted with 20 police staff, and also a focus group has been carried out with 15 law students. In the opinion of the respondents, people's perceptions and expectations of forensic science--as it can be observed during criminal trials--are largely inflated by the entertainment media. Among the surveyed persons, the category that declares watching crime series most rarely, is forensic science experts. Around half of the surveyed experts pointed out to excessive expectations towards they work instigated by TV crime series. The most common expectations towards forensic medicine experts are: immediate conclusiveness of post mortem examinations (going as far as indicating the cause of death at the crime scene), precision of death time estimation and a routine use of sophisticated methods known from TV.

A photocathode rf gun design for a mm-wave linac-based FEL

Energy Technology Data Exchange (ETDEWEB)

Nassiri, A.; Berenc, T,; Foster, J.; Waldschmidt, G.; Zhou, J.

1995-07-01

In recent years, advances in the rf gun technology have made it possible to produce small beam emittances suitable for short period microundulators which take advantage of the low emittance beam to reduce the wavelength of FELs. At the Advanced Photon Source, we are studying the design of a compact 50-MeV superconducting mm-wave linac-based FEL for the production of short wavelengths ({approximately}300 nm) to carry out FEL demonstration experiments. The electron source considered for the linac is a 30- GHz, 3 1/2-cell {pi}-mode photocathode rf gun. For cold model rf measurements a 15-GHz prototype structure was fabricated. Here we report on the design, numerical modelling and the initial cold-model rf measurement results on the 15-GHz prototype structure.

A photocathode rf gun design for a mm-wave linac-based FEL

International Nuclear Information System (INIS)

Nassiri, A.; Berenc, T.; Foster, J.; Waldschmidt, G.; Zhou, J.

1995-01-01

In recent years, advances in the rf gun technology have made it possible to produce small beam emittances suitable for short period microundulators which take advantage of the low emittance beam to reduce the wavelength of FELs. At the Advanced Photon Source, we are studying the design of a compact 50-MeV superconducting mm-wave linac-based FEL for the production of short wavelengths (∼300 nm) to carry out FEL demonstration experiments. The electron source considered for the linac is a 30- GHz, 3 1/2-cell π-mode photocathode rf gun. For cold model rf measurements a 15-GHz prototype structure was fabricated. Here we report on the design, numerical modelling and the initial cold-model rf measurement results on the 15-GHz prototype structure

Influence of wet chemical cleaning on quantum efficiency of GaN photocathode

International Nuclear Information System (INIS)

Wang Xiao-Hui; Gao Pin; Wang Hong-Gang; Li Biao; Chang Ben-Kang

2013-01-01

GaN samples 1–3 are cleaned by a 2:2:1 solution of sulfuric acid (98%) to hydrogen peroxide (30%) to de-ionized water; hydrochloric acid (37%); or a 4:1 solution of sulfuric acid (98%) to hydrogen peroxide (30%). The samples are activated by Cs/O after the same annealing process. X-ray photoelectron spectroscopy after the different ways of wet chemical cleaning shows: sample 1 has the largest proportion of Ga, N, and O among the three samples, while its C content is the lowest. After activation the quantum efficiency curves show sample 1 has the best photocathode performance. We think the wet chemical cleaning method is a process which will mainly remove C contamination. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Enhanced Photocatalytic Hydrogen Production By Surface Modification of p-Gap Photocathodes

DEFF Research Database (Denmark)

Malizia, Mauro; Seger, Brian; Chorkendorff, Ib

2014-01-01

of forming a p-n heterojunction on GaP. We deposit different n-type metal oxides (TiO2, Nb2O5, ...) thus forming an heterojunction which significantly enhances charge separation upon light irradiation by forming a built-in potential at the junction interface. This built-in potential effectively drives...... 300 mV compared to the pristine p-GaP semiconductor and marking an unprecedented value of open-circuit voltage for GaP-based photocathodes for hydrogen production. It is found that the high carrier density of the n-type oxides shifts the distribution of the built-in potential almost entirely towards...... the lightly doped p-type substrate and forms an asymmetric charge depletion region at the junction, as depicted in Figure 1. Moreover, TiO2shows excellent stability over long-time operation, unveiling its double role of brilliant material for both heterojunction formation and protection against corrosion...

Generation of quasiequally spaced ultrashort microbunches in a photocathode rf gun

International Nuclear Information System (INIS)

He, Zhigang; Xu, Yuanfang; Li, Weiwei; Jia, Qika

2015-01-01

A photocathode rf gun can generate trains of THz subpicosecond electron bunches by illuminating the cathode with trains of laser pulses, but it suffers from the increasing charge in the beam. The THz structure blurs and tends to disappear when the longitudinal space charge forces begin to play a significant role in the beam evolution. In this paper, we propose a scheme to restrain the space charge forces by expanding the transverse size of the laser pulses to reduce the charge density and adopting a multicell gun to increase the beam energy. Thus, quasiequally spaced ultrashort microbunches with relatively high charges can be generated according to our studies. Postacceleration can be used to freeze the longitudinal phase space dynamics. The proposed scheme is in principle able to generate intense multi-color narrow-band THz radiation and offers a promising way towards the tunable intense narrow-band THz sources

Designing Efficient Solar-Driven Hydrogen Evolution Photocathodes Using Semitransparent MoQxCly(Q = S, Se) Catalysts on Si Micropyramids

KAUST Repository

Ding, Qi

2015-09-21

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Silicon micropyramids with n+pp+ junctions are demonstrated to be efficient absorbers for integrated solar-driven hydrogen production systems enabling significant improvements in both photocurrent and onset potential. When conformally coated with MoSxCly, a catalyst that has excellent catalytic activity and high optical transparency, the highest photocurrent density for Si-based photocathodes with earth-abundant catalysts is achieved.

Towards efficient solar-to-hydrogen conversion: Fundamentals and recent progress in copper-based chalcogenide photocathodes

Directory of Open Access Journals (Sweden)

Chen Yubin

2016-09-01

Full Text Available Photoelectrochemical (PEC water splitting for hydrogen generation has been considered as a promising route to convert and store solar energy into chemical fuels. In terms of its large-scale application, seeking semiconductor photoelectrodes with high efficiency and good stability should be essential. Although an enormous number of materials have been explored for solar water splitting in the last several decades, challenges still remain for the practical application. P-type copper-based chalcogenides, such as Cu(In, GaSe2 and Cu2ZnSnS4, have shown impressive performance in photovoltaics due to narrow bandgaps, high absorption coefficients, and good carrier transport properties. The obtained high efficiencies in photovoltaics have promoted the utilization of these materials into the field of PEC water splitting. A comprehensive review on copper-based chalcogenides for solar-to-hydrogen conversion would help advance the research in this expanding area. This review will cover the physicochemical properties of copper-based chalco-genides, developments of various photocathodes, strategies to enhance the PEC activity and stability, introductions of tandem PEC cells, and finally, prospects on their potential for the practical solar-to-hydrogen conversion. We believe this review article can provide some insights of fundamentals and applications of copper-based chalco-genide thin films for PEC water splitting.

Femtosecond precision measurement of laser–rf phase jitter in a photocathode rf gun

International Nuclear Information System (INIS)

Shi, Libing; Zhao, Lingrong; Lu, Chao; Jiang, Tao; Liu, Shengguang; Wang, Rui; Zhu, Pengfei; Xiang, Dao

2017-01-01

We report on the measurement of the laser–rf phase jitter in a photocathode rf gun with femtosecond precision. In this experiment four laser pulses with equal separation are used to produce electron bunch trains; then the laser–rf phase jitter is obtained by measuring the variations of the electron bunch spacing with an rf deflector. Furthermore, we show that when the gun and the deflector are powered by the same rf source, it is possible to obtain the laser–rf phase jitter in the gun through measurement of the beam–rf phase jitter in the deflector. Based on these measurements, we propose an effective time-stamping method that may be applied in MeV ultrafast electron diffraction facilities to enhance the temporal resolution.

Femtosecond precision measurement of laser–rf phase jitter in a photocathode rf gun

Energy Technology Data Exchange (ETDEWEB)

Shi, Libing; Zhao, Lingrong; Lu, Chao; Jiang, Tao; Liu, Shengguang; Wang, Rui; Zhu, Pengfei; Xiang, Dao, E-mail: dxiang@sjtu.edu.cn

2017-03-21

We report on the measurement of the laser–rf phase jitter in a photocathode rf gun with femtosecond precision. In this experiment four laser pulses with equal separation are used to produce electron bunch trains; then the laser–rf phase jitter is obtained by measuring the variations of the electron bunch spacing with an rf deflector. Furthermore, we show that when the gun and the deflector are powered by the same rf source, it is possible to obtain the laser–rf phase jitter in the gun through measurement of the beam–rf phase jitter in the deflector. Based on these measurements, we propose an effective time-stamping method that may be applied in MeV ultrafast electron diffraction facilities to enhance the temporal resolution.

Time-resolved soft-x-ray studies of energy transport in layered and planar laser-driven targets

International Nuclear Information System (INIS)

Stradling, G.L.

1982-01-01

New low-energy x-ray diagnostic techniques are used to explore energy-transport processes in laser heated plasmas. Streak cameras are used to provide 15-psec time-resolution measurements of subkeV x-ray emission. A very thin (50 μg/cm 2 ) carbon substrate provides a low-energy x-ray transparent window to the transmission photocathode of this soft x-ray streak camera. Active differential vacuum pumping of the instrument is required. The use of high-sensitivity, low secondary-electron energy-spread CsI photocathodes in x-ray streak cameras is also described. Significant increases in sensitivity with only a small and intermittant decrease in dynamic range were observed. These coherent, complementary advances in subkeV, time-resolved x-ray diagnostic capability are applied to energy-transport investigations of 1.06-μm laser plasmas. Both solid disk targets of a variety of Z's as well as Be-on-Al layered-disk targets were irradiated with 700-psec laser pulses of selected intensity between 3 x 10 14 W/cm 2 and 1 x 10 15 W/cm 2

Characteristics of Pb{sup 2+} doped CsI matrix under gamma and neutron excitations

Energy Technology Data Exchange (ETDEWEB)

Pereira, Maria da Conceição Costa; Madi Filho, Tufic; Berretta, José Roberto; Tomaz, Lucas Faustino; Pinto, Marlene Cristina, E-mail: macoper@ipen.br, E-mail: tmfilho@ipen.br, E-mail: jrretta@ipen.br, E-mail: lucasfaus@gmail.com, E-mail: tynapinto@gmail.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2017-07-01

In recent years, there has been an increasing interest in finding new fast scintillating material or improve the characteristics of known scintillators for the demand of high energy physics, industrial and nuclear medical applications. Ions divalent lead Pb{sup 2+} built in some crystal structures are efficient emission centers and their applications in scintillators was and still is the reason of an intensive study of emission properties of different compounds containing these ions. The aggregation of impurities in CsI is poorly studied. The problem of impurity aggregation in CsI is of interest from point of view of the luminescent properties modification of this scintillation material. In this context, the crystals of Pb{sup 2+} doped CsI matrix were grown by the vertical Bridgman technique and subjected to annealing in vacuum of 10{sup -6} mbar and continuous temperature of 350°C, for 24 hours, and then they were employed. To evaluate the response of the CsI:Pb scintillator crystal to gamma radiation, radioactive sources of {sup 137}Cs (662 keV), {sup 60}Co (1173 keV and 1333 keV), {sup 22}Na (511 keV and 1275 keV) and {sup 13}3Ba (355 keV) was used. The operating voltage of the photomultiplier was 2700 V for the detection of gamma rays and the accumulation time in the counting process was 600 s. The crystals used in gamma spectroscopy were cut with dimensions of 20 mm in diameter and 20 mm in height. The scintillator response to neutron radiation from a radioactive source of Am/Be with energy range of 1 MeV to 12 MeV was available. The activity of the AmBe source was 1Ci Am. The fluency was 2.6 x 10{sup 6} neutrons / second. The operating voltage of the photomultiplier tube was 1300 V. The accumulation time in the counting process was 600 s. The scintillator crystals were cut with dimensions of 20 mm diameter and 10 mm height. With the results obtained, it may be observed that the crystals are sensitive to these radiations. (author)

The Feasibility of Small Hydro-Electric Generation in a Large Urban Area

OpenAIRE

Benson Y. Zhang; Adam Taylor

2012-01-01

The possibilities of generating electric power from relatively small hydro-electric sources in a large urban area is investigated. Two different aspects of hydro-electric sources have been studied: storm/waste water pipes in large multi-tenanted residential buildings and urban storm water discharge area (CSI area). The potential to generate from these sources has been investigated using a micro-turbine. The potential electric power which could be extracted from the sources was estimated using...

H{sub 2}-Ar dilution for improved c-Si quantum dots in P-doped SiN{sub x}:H thin film matrix

Energy Technology Data Exchange (ETDEWEB)

Liu, Jia [Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); Zhang, Weijia, E-mail: zwjghx@126.com [Center of Condensed Matter and Material Physics, School of Physics and Nuclear Energy Engineering, Beihang University, Beijing, 100191 (China); Liu, Shengzhong, E-mail: szliu@dicp.ac.cn [Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); State key Laboratory of Catalysis, iChEM, Dalian Institute of Chemical Physics, Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, Dalian 116023 (China)

2017-02-28

Highlights: • Phosphorous-doped SiN{sub x}:H thin films containing c-Si QDs were prepared by PECVD in H{sub 2}-Ar mixed dilution under low temperature. • QD density and QD size can be controlled by tuning H{sub 2}/Ar flow ratio. • The sample prepared at the H{sub 2}/Ar flow ratio of 100/100 possesses both wide band gap and excellent conductivity. • Detail discussion has been presented for illustrating the influence of H{sub 2}/Ar mixed dilution on the crystallization process and P-doping. - Abstract: Phosphorus-doped hydrogenated silicon nitride (SiN{sub x}:H) thin films containing crystalline silicon quantum dot (c-Si QD) was prepared by plasma enhanced chemical vapor deposition (PECVD) using hydrogen-argon mixed dilution. The effects of H{sub 2}/Ar flow ratio on the structural, electrical and optical characteristics of as-grown P-doped SiN{sub x}:H thin films were systematically investigated. Experimental results show that crystallization is promoted by increasing the H{sub 2}/Ar flow ratio in dilution, while the N/Si atomic ratio is higher for thin film deposited with argon-rich dilution. As the H{sub 2}/Ar flow ratio varies from 100/100 to 200/0, the samples exhibit excellent conductivity owing to the large volume fraction of c-Si QDs and effective P-doping. By adjusting the H{sub 2}/Ar ratio to 100/100, P-doped SiN{sub x}:H thin film containing tiny and densely distributed c-Si QDs can be obtained. It simultaneously possesses wide optical band gap and high dark conductivity. Finally, detailed discussion has been made to analyze the influence of H{sub 2}-Ar mixed dilution on the properties of P-doped SiN{sub x}:H thin films.

A compact large-format streak tube for imaging lidar

Science.gov (United States)

Hui, Dandan; Luo, Duan; Tian, Liping; Lu, Yu; Chen, Ping; Wang, Junfeng; Sai, Xiaofeng; Wen, Wenlong; Wang, Xing; Xin, Liwei; Zhao, Wei; Tian, Jinshou

2018-04-01

The streak tubes with a large effective photocathode area, large effective phosphor screen area, and high photocathode radiant sensitivity are essential for improving the field of view, depth of field, and detectable range of the multiple-slit streak tube imaging lidar. In this paper, a high spatial resolution, large photocathode area, and compact meshless streak tube with a spherically curved cathode and screen is designed and tested. Its spatial resolution reaches 20 lp/mm over the entire Φ28 mm photocathode working area, and the simulated physical temporal resolution is better than 30 ps. The temporal distortion in our large-format streak tube, which is shown to be a non-negligible factor, has a minimum value as the radius of curvature of the photocathode varies. Furthermore, the photocathode radiant sensitivity and radiant power gain reach 41 mA/W and 18.4 at the wavelength of 550 nm, respectively. Most importantly, the external dimensions of our streak tube are no more than Φ60 mm × 110 mm.

Beyond injection: Trojan horse underdense photocathode plasma wakefield acceleration

Energy Technology Data Exchange (ETDEWEB)

Hidding, B.; Rosenzweig, J. B.; Xi, Y.; O' Shea, B.; Andonian, G.; Schiller, D.; Barber, S.; Williams, O.; Pretzler, G.; Koenigstein, T.; Kleeschulte, F.; Hogan, M. J.; Litos, M.; Corde, S.; White, W. W.; Muggli, P.; Bruhwiler, D. L.; Lotov, K. [Institut fuer Laser- und Plasmaphysik, Heinrich-Heine-Universitaet Duesseldorf 40225 Duesseldorf (Germany) and Particle Beam Physics Laboratory, Department for Physics and Astronomy, UCLA (United States); Particle Beam Physics Laboratory, Department for Physics and Astronomy, UCLA (United States); Institut fuer Laser- und Plasmaphysik, Heinrich-Heine-Universitaet Duesseldorf 40225 Duesseldorf (Germany); Stanford Linear Accelerator Center (United States); Max-Planck-Institut fuer Physik, Muenchen (Germany); Tech-X Corporation, Boulder, Colorado (United States) and 1348 Redwood Ave., Boulder, Colorado 80304 (United States); Budker Institute of Nuclear Physics SB RAS, 630090, Novosibirsk (Russian Federation) and Novosibirsk State University, 630090, Novosibirsk (Russian Federation)

2012-12-21

An overview on the underlying principles of the hybrid plasma wakefield acceleration scheme dubbed 'Trojan Horse' acceleration is given. The concept is based on laser-controlled release of electrons directly into a particle-beam-driven plasma blowout, paving the way for controlled, shapeable electron bunches with ultralow emittance and ultrahigh brightness. Combining the virtues of a low-ionization-threshold underdense photocathode with the GV/m-scale electric fields of a practically dephasing-free beam-driven plasma blowout, this constitutes a 4th generation electron acceleration scheme. It is applicable as a beam brightness transformer for electron bunches from LWFA and PWFA systems alike. At FACET, the proof-of-concept experiment 'E-210: Trojan Horse Plasma Wakefield Acceleration' has recently been approved and is in preparation. At the same time, various LWFA facilities are currently considered to host experiments aiming at stabilizing and boosting the electron bunch output quality via a trojan horse afterburner stage. Since normalized emittance and brightness can be improved by many orders of magnitude, the scheme is an ideal candidate for light sources such as free-electron-lasers and those based on Thomson scattering and betatron radiation alike.

Experimental results from a DC photocathode electron gun for an IR FEL

International Nuclear Information System (INIS)

Kehne, D.; Engwall, D.; Legg, R.; Shinn, M.

1997-01-01

A 350 keV DC photocathode gun capable of delivering the high-brightness CW electron beam necessary for Jefferson Lab's infrared free-electron laser is described. The gun is to be used with a superconducting radiofrequency linac operating at 1.497 GHz and is mode-locked to the 40th subharmonic of the fundamental using a Nd:YLF drive laser. The gun provides 20--25 ps bunches at up to 135 pC/bunch. Experimental measurements of transverse and longitudinal beam properties are presented. Transverse emittance is measured using a slit-wire scanner emittance meter, and energy spread is measured using the slit and a spectrometer magnet. Longitudinal emittance is measured using a combination of sampling aperture, kicker cavity, slit and spectrometer. Measurements for bunch charges of 135 pC are described and compared with simulations

Synchronizaiton Between Laser and Electron Beam at Photocathode RF Gun

CERN Document Server

Sakumi, Akira; Fukasawa, Atsushi; Kumagai, Noritaka; Muroya, Yusa; Tomizawa, Hiromitsu; Ueda, T; Uesaka, Mitsuru; Urakawa, Junji; Yoshii, K

2005-01-01

The chemical reactions of hot, room temperature and critical water in a time-range of picosecond and sub-picosecond have been carried out by the 18 MeV S-band linac and a Mg photocathode RF gun with the irradiation of third harmonic Ti: Sapphire laser, at Nuclear Engineering Research Laboratory (NERL), the University of Tokyo. Although this short bunch and 100 fs laser light are enough to perform the experiment of radiation chemistry in the time-range of sub-picosecond, the total time-resolution become worse by the instability of synchronization between laser and radio frequency of linac. We found that the fluctuation of room temperature causes the instability, particularly the cycle of turning on/off of the air-conditioner. It is shown that 0.3 °C (peak-to-peak) fluctuation of the laser-room temperature have approximately corresponded to the instability of 6 ps. We are trying to decrease the fluctuation of the room temperature, together with the local temperature stability of the Ti: Sapphire crysta...

Generation of femtosecond electron single pulse using laser photocathode RF gun

Energy Technology Data Exchange (ETDEWEB)

Uesaka, M.; Kinoshita, K.; Watanabe, T. [Nuclear Engineering Research Laboratory, University of Tokyo, Tokai, Ibaraki (JP)] [and others

1998-11-01

A new laser photocathode RF electron gun was installed in the second linac of the S-band twin linac system of Nuclear Engineering Research Laboratory(NERL) of University of Tokyo in August in 1997. Since then, the behavior of the new gun has been tested and the characteristic parameters have been evaluated. At the exit of the gun, the energy is 4.7 MeV, the charge per bunch 1 nC, the pulse width is 10 ps(FWHM), respectively, for 6 MW RF power supply from a klystron. The electron bunch is accelerated up to 17 MeV. The horizontal normalized emittance is 1 {pi} mm.mrad. Then, the bunch is compressed to be 440 fs(FWHM) with 0.35 nC by the chicane-type magnetic pulse compressor. The gun is planned to be used for femtosecond X-ray generation via the head-on Thomson scattering and laser wakefield acceleration in 1998. (author)

Security-Reliability Analysis of Noma-Based Multi-Hop Relay Networks in Presence of an Active Eavesdropper with Imperfect Eavesdropping CSI

Directory of Open Access Journals (Sweden)

Tran Tin Phu

2017-01-01

Full Text Available In this paper, we evaluate system performances of a multi-hop relay protocol with presence of an active eavesdropper. In the proposed protocol, a source attempts to transmit its data to a destination with assistance of multiple intermediate relays. From the eavesdropping Channel State Information (CSI estimated, the source and relays adjust their transmit power so that the eavesdropper cannot overhear the transmitted data. Moreover, to enhance throughput for the proposed system, Non-Orthogonal Multiple Access (NOMA technique with a simple power allocation is also proposed. We derive exact closed-form expressions of the Outage Probability (OP and throughput for the data transmission over Rayleigh fading channel. In addition, when the CSI estimation is imperfect, Intercept Probability (IP at the eavesdropper is derived. Finally, Monte Carlo simulations are presented to verify the theoretical derivations.

Cellulose synthesis genes CESA6 and CSI1 are important for salt stress tolerance in Arabidopsis.

Science.gov (United States)

Zhang, Shuang-Shuang; Sun, Le; Dong, Xinran; Lu, Sun-Jie; Tian, Weidong; Liu, Jian-Xiang

2016-07-01

Two salt hypersensitive mutants she1 and she2 were identified through genetic screening. SHE1 encodes a cellulose synthase CESA6 while SHE2 encodes a cellulose synthase-interactive protein CSI1. Both of them are involved in cellulose deposition. Our results demonstrated that the sustained cellulose synthesis is important for salt stress tolerance in Arabidopsis. © 2015 Institute of Botany, Chinese Academy of Sciences.

VUV and ultrasoft X-ray diode detectors for tokamak plasmas

International Nuclear Information System (INIS)

Lee, P.; Snider, R.T.; Gernhardt, J.; Armontrout, C.J.

1987-11-01

Ultrasoft X-ray diode (USXRD) arrays have been used on D-IIID and ASDEX to study plasma edge radiation, in the photon energy range from 10 eV to 10 keV. The detectors are extremely useful and versatile due to their simplicity and compactness. Furthermore, absolute quantum efficiencies (QE) of many photocathodes such as vitreous C, Al, Cu CuI, CsI and Au have been measured in recent years. With filter technique, broadband resolution, E/ΔE ≅ 1, is possible. QE comparison of USXRD with semiconductor XRD is also presented to better understand the regions of applicability for each detector. (orig.)

Global Annual Final AC Yield Comparison between HCPV and c-Si PV

Directory of Open Access Journals (Sweden)

Juan Pablo Ferrer-Rodríguez

2015-01-01

Full Text Available A worldwide comparison of the annual yield between conventional c-Si photovoltaic (PV technology and high concentrated photovoltaic (HCPV technology is presented. The idea of this paper is to find the most appropriate locations for HCPV systems in terms of the annual energy produced when comparing to fixed tilt PV systems and two-axis oriented PY systems. For estimating the annual energy generation, the method of the Performance Ratio is used. For some locations with high annual direct normal irradiation values, which are distributed around the world, HCPV systems are found to be more advantageous than fixed tilt PV systems. World maps showing this comparison are presented.

Enhanced photocathodic behaviors of Pb(Zr{sub 0.20}Ti{sub 0.80})O{sub 3} films on Si substrates for hydrogen production

Energy Technology Data Exchange (ETDEWEB)

Cheng, Xiaorong; Dong, Wen; Zheng, Fengang; Fang, Liang; Shen, Mingrong, E-mail: mrshen@suda.edu.cn [College of Physics, Optoelectronics and Energy, Collaborative Innovation Center of Suzhou Nano Science and Technology, Photovoltaic Research Institute of Soochow University & Canadian Solar Inc., and Jiangsu Key Laboratory of Thin Films, Soochow University, 1 Shizi Street, Suzhou 215006 (China)

2015-06-15

Wide bandgap ferroelectric Pb(Zr{sub 0.20}Ti{sub 0.80})O{sub 3} films were deposited on indium tin oxide (ITO) coated Si-pn{sup +} substrates with an intention to form efficient Si-pn{sup +}/ITO/Pb(Zr,Ti)O{sub 3} (PZT) photocathode for hydrogen production. Depolarization electric field generated in PZT film due to poling can drive the photogenerated electrons from Si-pn{sup +} junction to PZT film, resulting in enhanced photoelectrochemical activity of the photocathode. Comparing the electrode with as-prepared PZT film, the photocurrent increased from −100 μA cm{sup −2} to −1.2 mA cm{sup −2} at 0 V vs. reversible hydrogen electrode (RHE) and the onset potential from 0.36 V to 0.7 V vs. RHE under 100 mW cm{sup −2} illumination, manifesting the great advantage of depolarization electric field in driving the photogenerated carriers not only in the ferroelectric film but also on the interface of different semiconductors.

Photocarrier radiometry for predicting the degradation of electrical parameters of monocrystalline silicon (c-Si) solar cell irradiated by 100 KeV proton beams

International Nuclear Information System (INIS)

Song, P.; Liu, J.Y.; Yuan, H.M.; Oliullah, Md.; Wang, F.; Wang, Y.

2016-01-01

In this study, the monocrystalline silicon (c-Si) solar cell irradiated by 100 KeV proton beams at various fluences is investigated. A one-dimensional two-layer carrier density wave model has been developed to estimate the minority carrier lifetime of n-region and p-region of the non-irradiated c-Si solar cell by best fitting with the experimental photocarrier radiometry (PCR) signal (the amplitude and the phase). Furthermore, the lifetime is used to determine the initial defect density of the quasi-neutral region (QNR) of the solar cell to predict its I–V characteristics. The theoretically predicted short-circuit current density (J_s_c), and open-circuit voltage (V_o_c) of the non-irradiated samples are in good agreement with experiment. Then a three-region defect distribution model for the c-Si solar cell irradiated by proton beams is carried out to describe the defect density distribution according to Monte Carlo simulation results and the initial defect density of the non-irradiated sample. Finally, we find that the electrical measurements of J_s_c and V_o_c of the solar cells irradiated at different fluences using 100 KeV proton beams are consistent with the PCR predicting results.

Photocarrier radiometry for predicting the degradation of electrical parameters of monocrystalline silicon (c-Si) solar cell irradiated by 100 KeV proton beams

Energy Technology Data Exchange (ETDEWEB)

Song, P. [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Liu, J.Y., E-mail: ljywlj@hit.edu.cn [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); State Key Laboratory of Robotics and System (HIT), Harbin 150001 (China); Yuan, H.M.; Oliullah, Md.; Wang, F. [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, Y., E-mail: songpengkevin@126.com [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); State Key Laboratory of Robotics and System (HIT), Harbin 150001 (China)

2016-09-15

In this study, the monocrystalline silicon (c-Si) solar cell irradiated by 100 KeV proton beams at various fluences is investigated. A one-dimensional two-layer carrier density wave model has been developed to estimate the minority carrier lifetime of n-region and p-region of the non-irradiated c-Si solar cell by best fitting with the experimental photocarrier radiometry (PCR) signal (the amplitude and the phase). Furthermore, the lifetime is used to determine the initial defect density of the quasi-neutral region (QNR) of the solar cell to predict its I–V characteristics. The theoretically predicted short-circuit current density (J{sub sc}), and open-circuit voltage (V{sub oc}) of the non-irradiated samples are in good agreement with experiment. Then a three-region defect distribution model for the c-Si solar cell irradiated by proton beams is carried out to describe the defect density distribution according to Monte Carlo simulation results and the initial defect density of the non-irradiated sample. Finally, we find that the electrical measurements of J{sub sc} and V{sub oc} of the solar cells irradiated at different fluences using 100 KeV proton beams are consistent with the PCR predicting results.

Environmental Stability and Oxidation Behavior of HfO2-Si and YbGd(O) Based Environmental Barrier Coating Systems for SiCSiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming; Farmer, Serene; McCue, Terry R.; Harder, Bryan; Hurst, Janet B.

2017-01-01

Ceramic environmental barrier coatings (EBC) and SiCSiC ceramic matrix composites (CMCs) will play a crucial role in future aircraft propulsion systems because of their ability to significantly increase engine operating temperatures, improve component durability, reduce engine weight and cooling requirements. Advanced EBC systems for SiCSiC CMC turbine and combustor hot section components are currently being developed to meet future turbine engine emission and performance goals. One of the significant material development challenges for the high temperature CMC components is to develop prime-reliant, environmental durable environmental barrier coating systems. In this paper, the durability and performance of advanced Electron Beam-Physical Vapor Deposition (EB-PVD) NASA HfO2-Si and YbGdSi(O) EBC bond coat top coat systems for SiCSiC CMC have been summarized. The high temperature thermomechanical creep, fatigue and oxidation resistance have been investigated in the laboratory simulated high-heat-flux environmental test conditions. The advanced NASA EBC systems showed promise to achieve 1500C temperature capability, helping enable next generation turbine engines with significantly improved engine component temperature capability and durability.

Chitin-Prussian blue sponges for Cs(I) recovery: From synthesis to application in the treatment of accidental dumping of metal-bearing solutions

Energy Technology Data Exchange (ETDEWEB)

Vincent, C. [Ecole des mines d' Alès, Centre des Matériaux des Mines d' Alès, C2MA/MPA/BCI, 6 avenue de Clavières, F-30319 Alès Cedex (France); Commissariat à l' Energie Atomique, CEA Marcoule, DEN/DTCD/SPDE/LPSD,BP 17171, F-30207 Bagnols sur Cèze (France); Barré, Y. [Commissariat à l' Energie Atomique, CEA Marcoule, DEN/DTCD/SPDE/LPSD,BP 17171, F-30207 Bagnols sur Cèze (France); Vincent, T. [Ecole des mines d' Alès, Centre des Matériaux des Mines d' Alès, C2MA/MPA/BCI, 6 avenue de Clavières, F-30319 Alès Cedex (France); Taulemesse, J.-M. [Ecole des mines d' Alès, Center des Matériaux des Mines d' Alès, 6 avenue de Clavières, F-30319 Alès Cedex (France); Robitzer, M. [Institut Charles Gerhardt – UMR5253, CNRS-UM2-ENSCM-UM1, ICGM-MACS-R2M2, 8 rue de l' Ecole Normale, F-34296 Montpellier Cedex 05 (France); Guibal, E., E-mail: Eric.Guibal@mines-ales.fr [Ecole des mines d' Alès, Centre des Matériaux des Mines d' Alès, C2MA/MPA/BCI, 6 avenue de Clavières, F-30319 Alès Cedex (France)

2015-04-28

Highlights: • Prussian blue microparticles incorporated in chitin sponges. • Efficient Cs(I) sorption after water absorption by dry hybrid sponge. • Water draining after sorption for metal confinement and water decontamination. • High decontamination factors and distribution coefficients for Cs(I) and {sup 137}Cs(I). • Effect of freezing conditions on porous structure and textural characterization. - Abstract: Prussian blue (i.e., iron[III] hexacyanoferrate[II], PB) has been synthesized by reaction of iron(III) chloride with potassium hexacyanoferrate and further immobilized in chitosan sponge (cellulose fibers were added in some samples to evaluate their impact on mechanical resistance). The composite was finally re-acetylated to produce a chitin-PB sponge. Experimental conditions such as the freezing temperature, the content of PB, the concentration of the biopolymer and the presence of cellulose fibers have been varied in order to evaluate their effect on the porous structure of the sponge, its water absorption properties and finally its use for cesium(I) recovery. The concept developed with this system consists in the absorption of contaminated water by the composite sponge, the in situ binding of target metal on Prussian blue load and the centrifugation of the material to remove treated water from soaked sponge. This material is supposed to be useful for the fast treatment of accidental dumping of Cs-contaminated water.

On the low SNR capacity of log-normal turbulence channels with full CSI

KAUST Repository

Benkhelifa, Fatma; Tall, Abdoulaye; Rezki, Zouheir; Alouini, Mohamed-Slim

2014-01-01

In this paper, we characterize the low signal-To-noise ratio (SNR) capacity of wireless links undergoing the log-normal turbulence when the channel state information (CSI) is perfectly known at both the transmitter and the receiver. We derive a closed form asymptotic expression of the capacity and we show that it scales essentially as λ SNR where λ is the water-filling level satisfying the power constraint. An asymptotically closed-form expression of λ is also provided. Using this framework, we also propose an on-off power control scheme which is capacity-achieving in the low SNR regime.

On the low SNR capacity of log-normal turbulence channels with full CSI

KAUST Repository

Benkhelifa, Fatma

2014-09-01

In this paper, we characterize the low signal-To-noise ratio (SNR) capacity of wireless links undergoing the log-normal turbulence when the channel state information (CSI) is perfectly known at both the transmitter and the receiver. We derive a closed form asymptotic expression of the capacity and we show that it scales essentially as λ SNR where λ is the water-filling level satisfying the power constraint. An asymptotically closed-form expression of λ is also provided. Using this framework, we also propose an on-off power control scheme which is capacity-achieving in the low SNR regime.

Performance study of single undoped CsI crystals for the Mu2e experiment

International Nuclear Information System (INIS)

Donghia, R.

2016-01-01

The Mu2e experiment at Fermilab aims to measure the neutrinoless muon-to-electron conversion, which is a charged-lepton flavor-violating process. The goal of the experiment is to reach a single event sensitivity of 2.5 × 10"−"1"7, to set an upper limit on the muon conversion rate at 6.7 × 10"−"1"7 in a three-year run. For this purpose, the Mu2e detector is designed to identify electrons from muon conversion and reduce the background to a negligible level. It consists of a low-mass straw tracker and a pure CsI crystal calorimeter. In this paper, the performance of undoped CsI single crystal is reported. Crystals from many vendors have been characterized by determining their Light Yield (LY) and Longitudinal Response Uniformity (LRU), when read with a UV extended PMT, and their time resolution when coupled to a silicon photomultiplier. The crystals show a LY of ∼ 100 photoelectrons per MeV when wrapped with Tyvek and coupled to the PMT without optical grease. The LRU is well represented by a linear slope that is on average 0.6%/cm. Both measurements have been performed using a "2"2Na source. The timing performance has been evaluated exploiting cosmic rays, with MPPC readout. A timing resolution lower than 400 ps has been achieved (at ∼ 20 MeV, which is the energy released by a minimum ionizing particle in the crystal).

Process Optimization for High Efficiency Heterojunction c-Si Solar Cells Fabrication Using Hot-Wire Chemical Vapor Deposition: Preprint

Energy Technology Data Exchange (ETDEWEB)

Ai, Y.; Yuan, H. C.; Page, M.; Nemeth, W.; Roybal, L.; Wang, Q.

2012-06-01

The researchers extensively studied the effects of annealing or thermal history of cell process on the minority carrier lifetimes of FZ n-type c-Si wafers with various i-layer thicknesses from 5 to 60 nm, substrate temperatures from 100 to 350 degrees C, doped layers both p- and n-types, and transparent conducting oxide (TCO).

Progress in the medicinal chemistry of silicon: C/Si exchange and beyond.

Science.gov (United States)

Fujii, Shinya; Hashimoto, Yuichi

2017-04-01

Application of silyl functionalities is one of the most promising strategies among various 'elements chemistry' approaches for the development of novel and distinctive drug candidates. Replacement of one or more carbon atoms of various biologically active compounds with silicon (so-called sila-substitution) has been intensively studied for decades, and is often effective for alteration of activity profile and improvement of metabolic profile. In addition to simple C/Si exchange, several novel approaches for utilizing silicon in medicinal chemistry have been suggested in recent years, focusing on the intrinsic differences between silicon and carbon. Sila-substitution offers great potential for enlarging the chemical space of medicinal chemistry, and provides many options for structural development of drug candidates.

Dosimetric comparison between proton and photon beams in the moving gap region in cranio-spinal irradiation (CSI)

Energy Technology Data Exchange (ETDEWEB)

Cheng, Chee-Wai; Das, Indra J.; Zhao, Li; Wolanski, Mark; Johnstone, Peter A.S.; Buchsbaum, Jeffrey C. [IU Health Proton Therapy Center, Bloomington (United States); Dept. of Radiation Oncology, Indiana Univ. School of Medicine, Indianapolis (United States)], e-mail: ccheng1@iuhealth.org; Srivastava, Shiv P. [Dept. of Radiation Oncology, Indiana Univ. School of Medicine, Indianapolis (United States); Dept. of Radiation Oncology, Reid Hospital, Richmond (United States); Simmons, Joseph [IU Health Proton Therapy Center, Bloomington (United States)

2013-04-15

Purpose: To investigate the moving gap region dosimetry in proton beam cranio-spinal irradiation (CSI) to provide optimal dose uniformity across the treatment volume. Material and methods: Proton beams of ranges 11.6 cm and 16 cm are used for the spine and the brain fields, respectively. Beam profiles for a 30 cm snout are first matched at the 50% level (hot match) on the computer. Feathering is simulated by shifting the dose profiles by a known distance two successive times to simulate a 2 x feathering scheme. The process is repeated for 2 mm and 4 mm gaps. Similar procedures are used to determine the dose profiles in the moving gap for a series of gap widths, 0-10 mm, and feathering step sizes, 4-10 mm, for a Varian iX 6MV beam. The proton and photon dose profiles in the moving gap region are compared. Results: The dose profiles in the moving gap exhibit valleys and peaks in both proton and photon beam CSI. The dose in the moving gap for protons is around 100% or higher for 0 mm gap, for both 5 and 10 mm feathering step sizes. When the field gap is comparable or larger than the penumbra, dose minima as low as 66% is obtained. The dosimetric characteristics for 6 MV photon beams can be made similar to those of the protons by appropriately combining gap width and feathering step size. Conclusion: The dose in the moving gap region is determined by the lateral penumbras, the width of the gap and the feathering step size. The dose decreases with increasing gap width or decreasing feathering step size. The dosimetric characteristics are similar for photon and proton beams. However, proton CSI has virtually no exit dose and is beneficial for pediatric patients, whereas with photon beams the whole lung and abdomen receive non-negligible exit dose.

Experimental measurement of a high resolution CMOS detector coupled to CsI scintillators under X-ray radiation

International Nuclear Information System (INIS)

Michail, C.; Valais, I.; Seferis, I.; Kalyvas, N.; Fountos, G.; Kandarakis, I.

2015-01-01

The purpose of the present study was to assess the information content of structured CsI:Tl scintillating screens, specially treated to be compatible to a CMOS digital imaging optical sensor, in terms of the information capacity (IC), based on Shannon's mathematical communication theory. IC was assessed after the experimental determination of the Modulation Transfer Function (MTF) and the Normalized Noise Power Spectrum (NNPS) in the mammography and general radiography energy range. The CMOS sensor was coupled to three columnar CsI:Tl scintillator screens obtained from the same manufacturer with thicknesses of 130, 140 and 170 μm respectively, which were placed in direct contact with the optical sensor. The MTF was measured using the slanted-edge method while NNPS was determined by 2D Fourier transforming of uniformly exposed images. Both parameters were assessed by irradiation under the mammographic W/Rh (130, 140 and 170 μm CsI screens) and the RQA-5 (140 and 170 μm CsI screens) (IEC 62220-1) beam qualities. The detector response function was linear for the exposure range under investigation. At 70 kVp, under the RQA-5 conditions IC values were found to range between 2229 and 2340 bits/mm 2 . At 28 kVp the corresponding IC values were found to range between 2262 and 2968 bits/mm 2 . The information content of CsI:Tl scintillating screens in combination to the high resolution CMOS sensor, investigated in the present study, where found optimized for use in digital mammography imaging systems. - Highlights: • Three structured CsI:Tl screens (130,140 & 170 um) were coupled to a CMOS sensor. • MTF of the CsI/CMOS was higher than GOS:Tb and CsI based digital imaging systems. • IC of CsI:Tl/CMOS was found optimized for use in digital mammography systems

Research on DC-RF superconducting photocathode injector for high average power FELs

International Nuclear Information System (INIS)

Zhao Kui; Hao Jiankui; Hu Yanle; Zhang Baocheng; Quan Shengwen; Chen Jiaer; Zhuang Jiejia

2001-01-01

To obtain high average current electron beams for a high average power Free Electron Laser (FEL), a DC-RF superconducting injector is designed. It consists of a DC extraction gap, a 1+((1)/(2)) superconducting cavity and a coaxial input system. The DC gap, which takes the form of a Pierce configuration, is connected to the 1+((1)/(2)) superconducting cavity. The photocathode is attached to the negative electrode of the DC gap. The anode forms the bottom of the ((1)/(2)) cavity. Simulations are made to model the beam dynamics of the electron beams extracted by the DC gap and accelerated by the superconducting cavity. High quality electron beams with emittance lower than 3 π-mm-mrad can be obtained. The optimization of experiments with the DC gap, as well as the design of experiments with the coaxial coupler have all been completed. An optimized 1+((1)/(2)) superconducting cavity is in the process of being studied and manufactured

High-quality electron pulse generation from a laser photocathode RF gun

International Nuclear Information System (INIS)

Yang, Jinfeng; Sakai, Fumio; Aoki, Yasushi

1999-01-01

A laser photocathode RF gun system was developed for ultra short X-ray pulse generation via the inverse Compton scattering. The gun is a BNL-type S-band RF gun and the performance test of the gun was performed at the Linear Accelerator Facility in the Institute of Scientific and Industries Research, Osaka University. The gun system produced 115 pC electron bunches with the energy of 1.6 MeV under the condition of RF peak power of 1.5 MW and laser pulse energy of 65 μJ. The quantum efficiency and dark current were obtained to be 10 -5 and 0.6 nA at the repetition rate of 10 Hz, respectively. The energy and charge of the electron bunch were measured as a function of laser injection phase. Furthermore, the electron bunches were accelerated up to 117 MeV by three s-band TW linacs and the energy monochromaticity (ΔE/E) of the beam was 1.2%. The transverse emittance was also experimentally investigated at the end of the linacs. (author)

Status of SPring-8 Photocathode Rf Gun for Future Light Sources

CERN Document Server

Tomizawa, H; Dewa, H; Hanaki, H; Kobayashi, T; Mizuno, A; Suzuki, S; Taniuchi, T; Yanagida, K

2005-01-01

We have been studying photocathode single-cell pillbox rf gun for future light sources since 1996. We achieved a rmaximum field gradient of 187 MV/m with chemical-etching processed cavity. We have been developed stable and highly qualified UV-laser source for the rf gun intensively last 3 years. The UV-laser pulse (10 Hz) energy is up to 850 uJ/pulse. The energy stability (rms) of laser has been improved down to 0.2~0.3 % at the fundamental and 0.7~1.3% at the third harmonic generation. This stability is held for two months continuously. In this improvement, we just passively stabilized the system in a humidity-controlled clean room. On the other hand, the ideal spatial and temporal profiles of a shot-by-shot single laser pulse are essential to suppress the emittance growth of the electron beam from the rf gun. We prepared a deformable mirror for spatial shaping, and a spatial light modulator based on fused-silica plates for temporal shaping. With a deformable mirror, we obtained an emittance of1.6

FY16 ASC ATDM L2 Milestone: PARTISN Research and FleCSI Updates

Energy Technology Data Exchange (ETDEWEB)

Womeldorff, Geoffrey Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Payne, Joshua Estes [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bergen, Benjamin Karl [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-09-01

These are slides for a presentation on PARTISN Research and FleCSI Updates. The following topics are covered: SNAP vs PARTISN, Background Research, Production Code (structural design and changes, kernel design and implementation, lessons learned), NuT IMC Proxy, FleCSI Update (design and lessons learned). It can all be summarized in the following manner: Kokkos was shown to be effective in FY15 in implementing a C++ version of SNAP's kernel. This same methodology was applied to a production IC code, PARTISN. This was a much more complex endeavour than in FY15 for many reasons; a C++ kernel embedded in Fortran, overloading Fortran memory allocations, general language interoperability, and a fully fleshed out production code versus a simplified proxy code. Lessons learned are Legion. In no particular order: Interoperability between Fortran and C++ was really not that hard, and a useful engineering effort. Tracking down all necessary memory allocations for a kernel in a production code is pretty hard. Modifying a production code to work for more than a handful of use cases is also pretty hard. Figuring out the toolchain that will allow a successful implementation of design decisions is quite hard, if making use of "bleeding edge" design choices. In terms of performance, production code concurrency architecture can be a virtual showstopper; being too complex to easily rewrite and test in a short period of time, or depending on tool features which do not exist yet. Ultimately, while the tools used in this work were not successful in speeding up the production code, they helped to identify how work would be done, and provide requirements to tools.

Energy-Efficient Power Allocation of Cognitive Radio Systems without CSI at the Transmitter

KAUST Repository

Sboui, Lokman

2015-01-07

Two major issues are facing today’s wireless communications evolution: -Spectrum scarcity: Need for more bandwidth. As a solution, the Cognitive Radio (CR) paradigm, where secondary users (unlicensed) share the spectrum with licensed users, was introduced. -Energy consumption and CO2 emission: The ICT produce 2% of global CO2 emission (equivalent to the aviation industry emission). The cellular networks produces 0.2%. As solution energy efficient systems should be designed rather than traditional spectral efficient systems. In this work, we aim to determine the optimal energy efficient power allocation of CR when the channel state information at the transmitter CSI-T is not available.

Energy-Efficient Power Allocation of Cognitive Radio Systems without CSI at the Transmitter

KAUST Repository

Sboui, Lokman; Rezki, Zouheir; Alouini, Mohamed-Slim

2015-01-01

Two major issues are facing today’s wireless communications evolution: -Spectrum scarcity: Need for more bandwidth. As a solution, the Cognitive Radio (CR) paradigm, where secondary users (unlicensed) share the spectrum with licensed users, was introduced. -Energy consumption and CO2 emission: The ICT produce 2% of global CO2 emission (equivalent to the aviation industry emission). The cellular networks produces 0.2%. As solution energy efficient systems should be designed rather than traditional spectral efficient systems. In this work, we aim to determine the optimal energy efficient power allocation of CR when the channel state information at the transmitter CSI-T is not available.

Transfer and breakup reactions in 16O + CsI at 16.4 MeV/n

Directory of Open Access Journals (Sweden)

M.J. Murphy

1983-01-01

Full Text Available A streamer-chamber particle-telescope system has been used to observe ejectile charge, energy, and associated charged particle multiplicity in the reaction of 16O + CsI at 16.4 MeV/n. The measurement provides relative probabilities for transfer and projectile breakup as a function of ejectile charge, and spectra for the heavy ejectiles from transfer and breakup events. The results show that the interaction energy of 16.4 MeV/n is near the threshold for breakup reactions in heavy-ion collisions.

Secondary emission coefficient dependence on the angle of incidence of primary electrons on CsI and LiF layers. [0. 9 to 3 keV, mechanism

Energy Technology Data Exchange (ETDEWEB)

Shabel' nikova, A E; Yasnopol' skii, N L

1976-08-01

The angular dependence was studied of the secondary emission coefficient sigma for CsI and LiF dielectrics which have large sigma in conditions of normal incidence of primary electrons. Measurements were taken down to the angle of 85 deg for energies of primary electrons between 0.9 and 3 keV. In the whole range of angles a nonmonotonic angular dependence sigma is observed. The dependence shows itself particularly clearly for CsI at large energies of primary electrons. Such a behaviour is due to the decrease in the depth of yield of inelastically reflected electrons and to the increase in the inelastic reflection coefficient of the substance.

On mass in 4π solid angle around song CsI scintillator aboard coronas-I satellite

International Nuclear Information System (INIS)

Bucik, R.; Kudela, K.

2003-01-01

The complex geometric setup around the SONG CsI scintillator aboard the CORONAS-1 satellite has been modelled, to evaluate the mass thickness passed through by the cosmic ray particle striking the detector. The analytic functional form giving the amount of matter traversed in absorbers for an arbitrary incident directions is present. The population mean and variance of the mass thickness are estimated by random sampling of the uniformly distributed particle trajectories in the several solid angles (Authors)

Image dissector photocathode solar damage test program. [solar radiation shielding using a fast optical lens

Science.gov (United States)

Smith, R. A.

1977-01-01

Image dissector sensors of the same type which will be used in the NASA shuttle star tracker were used in a series of tests directed towards obtaining solar radiation/time damage criteria. Data were evaluated to determine the predicted level of operability of the star tracker if tube damage became a reality. During the test series a technique for reducing the solar damage effect was conceived and verified. The damage concepts are outlined and the test methods and data obtained which were used for verification of the technique's feasibility are presented. The ability to operate an image dissector sensor with the solar image focussed on the photocathode by a fast optical lens under certain conditions is feasible and the elimination of a mechanical protection device is possible.

Role of field-effect on c-Si surface passivation by ultrathin (2-20 nm) atomic layer deposited Al2O3

NARCIS (Netherlands)

Terlinden, N.M.; Dingemans, G.; Sanden, van de M.C.M.; Kessels, W.M.M.

2010-01-01

Al2O3 synthesized by plasma-assisted atomic layer deposition yields excellent surface passivation of crystalline silicon (c-Si) for films down to ~ 5 nm in thickness. Optical second-harmonic generation was employed to distinguish between the influence of field-effect passivation and chemical

The effect of γ-ray irradiation on the adsorption properties and chemical stability of AMP/SiO2 towards Cs(I) in HNO3 solution

International Nuclear Information System (INIS)

Xiaoxia Zhang; Yan Wu; Yuezhou Wei; Guangxi University, Nanning

2016-01-01

Silica based ammonium molybdophosphate (AMP/SiO 2 ) adsorbent was used to remove Cs(I) from HNO 3 solution. The adsorbent with different absorbed dose (0-300 kGy) was characteristed by X-ray power diffraction. The adsorption data against different γ-ray absorbed doses were analyzed by the Langmuir isotherm. The adsorption capacity decreased slightly from 23.22 to 22.37 mg/g with the increase of the absorbed dose. The breakthrough properties of Cs(I) were conducted using column packed with AMP/SiO 2 before and after irradiation. The chemical stability of AMP/SiO 2 at 300 kGy absorbed dose in 3 mol/L (M) HNO 3 was excellent. (author)

Emittance studies of the BNL/SLAC/UCLA 1.6 cell photocathode rf gun

International Nuclear Information System (INIS)

Palmer, D.T.; Miller, R.H.; Wang, X.J.

1997-01-01

The symmetrized 1.6 cell S-band photocathode gun developed by the BNL/SLAC/UCLA collaboration is in operation at the Brookhaven Accelerator Test Facility (ATF). A novel emittance compensation solenoid magnet has also been designed, built and is in operation at the ATF. These two subsystems form an emittance compensated photoinjector used for beam dynamics, advanced acceleration and free electron laser experiments at the ATF. The highest acceleration field achieved on the copper cathode is 150 MV/m, and the guns normal operating field is 130 MV/m. The maximum rf pulse length is 3 micros. The transverse emittance of the photoelectron beam were measured for various injection parameters. The 1 nC emittance results are presented along with electron bunch length measurements that indicated that at above the 400 pC, space charge bunch lengthening is occurring. The thermal emittance, ε o , of the copper cathode has been measured

The Mu2e undoped CsI crystal calorimeter

Science.gov (United States)

Atanov, N.; Baranov, V.; Budagov, J.; Cervelli, F.; Colao, F.; Cordelli, M.; Corradi, G.; Davydov, Y. I.; Di Falco, S.; Diociaiuti, E.; Donati, S.; Donghia, R.; Echenard, B.; Giovannella, S.; Glagolev, V.; Grancagnolo, F.; Happacher, F.; Hitlin, D. G.; Martini, M.; Miscetti, S.; Miyashita, T.; Morescalchi, L.; Murat, P.; Pedreschi, E.; Pezzullo, G.; Porter, F.; Raffaelli, F.; Ricci, M.; Saputi, A.; Sarra, I.; Spinella, F.; Tassielli, G.; Tereshchenko, V.; Usubov, Z.; Zhu, R. Y.

2018-02-01

The Mu2e experiment at Fermilab will search for Charged Lepton Flavor Violating conversion of a muon to an electron in an atomic field. The Mu2e detector is composed of a tracker, an electromagnetic calorimeter and an external system, surrounding the solenoid, to veto cosmic rays. The calorimeter plays an important role to provide: a) excellent particle identification capabilities; b) a fast trigger filter; c) an easier tracker track reconstruction. Two disks, located downstream of the tracker, contain 674 pure CsI crystals each. Each crystal is read out by two arrays of UV-extended SiPMs. The choice of the crystals and SiPMs has been finalized after a thorough test campaign. A first small scale prototype consisting of 51 crystals and 102 SiPM arrays has been exposed to an electron beam at the BTF (Beam Test Facility) in Frascati. Although the readout electronics were not final, results show that the current design is able to meet the timing and energy resolution required by the Mu2e experiment.

RF Design and Operating Performance of the BNL/AES 1.3 GHz Single Cell Superconducting RF Photocathode Electron Gun

International Nuclear Information System (INIS)

Cole, Michael; Kneisel, Peter; Ben-Zvi, Ilan; Burrill, Andrew; Hahn, H.; Rao, Triveni; Zhao, Y.

2005-01-01

Over the past several years Advanced Energy Systems and BNL have been collaborating on the development and testing of a fully superconducting photocathode electron gun. Over the past year we have begun to realize significant results which have been published elsewhere (1). This paper will review the RF design of the gun under test and present results of its performance under various operating conditions. Results for cavity quality factor will be presented for various operating temperatures and cavity field gradients. We will also discuss future plans for testing using this gun.

R&D studies of a RICH detector using pressurized C$_{4}$F$_{8}$O radiator gas and a CsI-based gaseous photon detector

CERN Document Server

Agócs, A.G; Barnaföldi, G.G; Bellwied, R; Bencédi, G; Bencze, G; Berényi, D; Boldizsár, L; Chattopadhyay, S; Chinellato, D.D; Cindolo, F; Das-Bose, L; Das, D; Das, K; De Cataldo, G; Di Bari, D; Di Mauro, A; Futó, E; Garcia, E; Hamar, G; Harton, A; Jimenez, R.T; Kim, D.W; Kim, J.S; Knospe, A; Kovacs, L; Lévai, P; Markert, C; Martinengo, P; Molnar, L; Nappi, E; Olah, L; Paic, G; Pastore, C; Patino, M.E; Peskov, V; Pinsky, L; Piuz, F; Pochybova, S; Sgura, I; Sinha, T; Song, J; Timmins, A; Van Beelen, J.B; Varga, D; Volpe, G; Weber, M; Xaplanteris, L; Yi, J; Yoo, I.-K

2013-01-01

We report on studies of layout and performance of a new Ring Imaging Cherenkov detector using for the fi rst time pressurized C 4 F 8 O radiator gas and a photon detector consisting of a MWPC equipped with a CsI photocathode. In particular, we present here the results of beam tests of a MWPC having an adjustable anode – cathode gap, aiming at the optimization of single photoelectron detection and Cherenkov angle resolution. This system was proposed as a Very High Momentum Particle Identi fi cation (VHMPID) upgrade for the ALICE experiment at LHC to provide charged hadron track-by-track identi fi cation in the momentum range 5 – 25 GeV/c.

VHMPID RICH prototype using pressurized C{sub 4}F{sub 8}O radiator gas and VUV photon detector

Energy Technology Data Exchange (ETDEWEB)

Acconcia, T.V. [UNICAMP, University of Campinas, Campinas (Brazil); Agócs, A.G. [Wigner RCP of the HAS, Budapest (Hungary); Barile, F. [INFN Sezione di Bari and Universitá degli Studi di Bari, Dipartimento Interateneo di Fisica M. Merlin, Bari (Italy); Barnaföldi, G.G. [Wigner RCP of the HAS, Budapest (Hungary); Bellwied, R. [University of Houston, Houston (United States); Bencédi, G. [Wigner RCP of the HAS, Budapest (Hungary); Bencze, G., E-mail: Gyorgy.Bencze@cern.ch [Wigner RCP of the HAS, Budapest (Hungary); Berényi, D.; Boldizsár, L. [Wigner RCP of the HAS, Budapest (Hungary); Chattopadhyay, S. [Saha Institute, Kolkata (India); Chinellato, D.D. [University of Houston, Houston (United States); Cindolo, F. [University of Salerno, Salerno (Italy); Cossyleon, K. [Chicago State University, Chicago, IL (United States); Das, D.; Das, K.; Das-Bose, L. [Saha Institute, Kolkata (India); Dash, A.K. [UNICAMP, University of Campinas, Campinas (Brazil); D' Ambrosio, S. [University of Salerno, Salerno (Italy); De Cataldo, G. [INFN Sezione di Bari and Universitá degli Studi di Bari, Dipartimento Interateneo di Fisica M. Merlin, Bari (Italy); De Pasquale, S. [University of Salerno, Salerno (Italy); and others

2014-12-11

A small-size prototype of a new Ring Imaging Cherenkov (RICH) detector using for the first time pressurized C4F8O radiator gas and a photon detector consisting of MWPC equipped with a CsI photocathode has been built and tested at the PS accelerator at CERN. It contained all the functional elements of the detector proposed as Very High Momentum Particle Identification (VHMPID) upgrade for the ALICE experiment at LHC to provide charged hadron track-by-track identification in the momentum range starting from 5 potentially up to 25 GeV/c. In the paper the equipment and its elements are described and some characteristic test results are shown.

Validation of the Artsana CSI 610 automated blood pressure monitor in adults according to the International Protocol of the European Society of Hypertension.

Science.gov (United States)

Pini, Claudio; Pastori, Marco; Baccheschi, Jordan; Omboni, Stefano; Parati, Gianfranco

2007-06-01

There is evidence that blood pressure measurement outside the doctor's office can provide valuable information for the diagnostic evaluation of hypertensive patients and for monitoring their response to treatment. Home blood pressure monitoring devices have a major role in this setting, provided that their accuracy in measuring blood pressure is demonstrated by validation studies. This study aimed at verifying whether the automatic electronic oscillometric blood pressure measuring device Artsana CSI 610 complied with the standard of accuracy indicated by the ESH International Protocol. Sequential measurements of systolic and diastolic blood pressure were obtained in 33 participants using the mercury sphygmomanometer (two observers) and the test device (one supervisor). A standard adult cuff was always employed during the study. According to the ESH validation protocol, 99 couples of test device and reference blood pressure measurements were obtained during the two phases of the study (three pairs for each of the 33 participants). The Artsana CSI 610 device successfully passed phase 1 of study validation with the number of absolute differences between test and reference device never validation study with a mean (+/-SD) device-observer difference of -1.4+/-4.8 mmHg for systolic and -0.9+/-3.5 mmHg for diastolic blood pressure. According to the results of the validation study on the basis of the ESH International Protocol, the Artsana CSI 610 can be recommended for clinical use in adults.

Results from cosmics and first LHC beam with the ALICE HMPID detector

CERN Document Server

Volpe, Giacomo

2009-01-01

The ALICE HMPID (High Momentum Particle IDentification) detector has been designed to identify charged pions and kaons in the range 1 < p < 3 GeV/c and protons in the range 1.5 < p < 5 GeV/c. It consists of seven identical proximity focusing RICH (Ring Imaging Cherenkov) counters, covering in total 11 m2, which exploit large area MWPC equipped with CsI photocathodes for Cherenkov light imaging emitted in a liquid C6F14 radiator. The ALICE detector has been widely commissioned using cosmics and LHC beam from December 2007 until October 2008. During the cosmics data taking the HMPID detector collected a large set of data, using mainly the trigger provided by the TOF detector. We present here preliminary results of detector alignment using TPC tracking. The HMPID could be operated in a stable way, at a safe HV setting, also during LHC beam injection and circulation tests, when a very large occupancy (up to 50%) was achieved. Resulting gain mapping and overall detector performance will also be discuss...

The novel photon detectors based on MPGD technologies for the upgrade of COMPASS RICH-1

CERN Document Server

Tessarotto, F.; Alexeev, M.; Azevedo, C.D.R.; Birsa, R.; Bradamante, F.; Bressan, A.; Chatterjee, C.; Chiosso, M.; Cicuttin, A.; Ciliberti, P.; Crespo, M.L.; Dalla Torre, S.; Dasgupta, S.S.; Denisov, O.; Finger, M.; Finger Jr., M.; Gobbo, B.; Gregori, M.; Hamar, G.; Levorato, S.; Maggiora, A.; Martin, A.; Menon, G.; Novy, J.; Panzieri, D.; Pereira, F.A.B.; Santos, C.A.; Sbrizzai, G.; Slunecka, M.; Steiger, K.; Steiger, L.; Sulc, M.; Veloso, J.F.C.A.; Zhao,Y.

2018-01-01

The RICH-1 Detector of the COMPASS experiment at CERN SPS has undergone an important upgrade in 2016. Four new photon detectors, based on MPGD technology and covering a total active area larger than 1.2~m2 have replaced the previously used MWPC-based photon detectors. The new detector architecture, resulting from a dedicated, eight years long, R\\&D program, consists in a hybrid MPGD combination of two THGEMs and a Micromegas stage; the first THGEM, coated with a CsI layer, acts as a reflective photocathode. The signals are extracted from the anode pads by capacitive coupling and read-out by analog front-end electronics based on the APV25 chip. The new COMPASS RICH-1 photon detectors are described in detail: the detector design, the engineering aspects, the mass production, and the quality assessment are discussed. The assembly of the MPGD components and the installation of the new detectors are illustrated together with the main aspects of the commissioning. Preliminary indication of performance results a...

Study on the drive laser system of the photocathode-injector used in high gain FEL

CERN Document Server

Lu Xiang Yang; Zhao Kui; Wang Li; Quan Sheng Wen; Hao Jian Kui; Zhang Bao Cheng; Chen J

2002-01-01

High gain FEL requires high quality electron beam which can be provided only by the RF photocathode gun. The drive laser for electron source plays the key role. In Institute of Heavy Ion Physics of Beijing University, the laser system is required to deliver a 500 mu J, 6-8 ps pulse of UV photons (260 nm) to the cathode. This system mainly consists of a CW, frequency-doubled, diode-pumped Nd:YAG laser, which provides energy to pump a CW mode-locked Ti:sapphire oscillator, Q-switched Nd:YaG pump lasers, a regenerative amplifier and harmonics crystals. To meet the low jitters of pulses (1.0 ps), cavity length of the oscillator should be adjustable to lock the pulse frequency with external RF reference, and a phase stability feedback system is also used

Design of a high-brightness, high-duty factor photocathode electron gun

International Nuclear Information System (INIS)

Lehrman, I.S.; Birnbaum, I.A.; Fixler, S.Z.; Heuer, R.L.; Siddiqi, S.; Sheedy, E.; Ben-Zvi, I.; Batchelor, K.; Gallardo, J.C.; Kirk, H.G.; Srinivasan-Rao, T.; Warren, G.D.

1991-09-01

The proposed UV-FEL user's facility at Brookhaven National Laboratory will require a photocathode gun capable of producing short (< 6 psec) bunches of electrons in high repetition rates (5 kHz), low energy spread (< 1.5.%), a peak current of 300 A (after compression) and a total bunch charge of up to 2 nC. At the highest charge the normalized transverse emittance should be less than 7 π mm-mrad. We are presently designing a gun that is expected to exceed these requirements. This gun will consist of 3 1/2 cells, constructed of GlidCop-15, an aluminum oxide dispersion strengthened copper alloy. The gun will be capable of operating at duty factors in excess of 1%. Extensive beam dynamics studies of the gun were used to determine the effect of varying the length of the first cell, shaping the apertures between cells, and increasing the number of cells. In addition, a detailed thermal and mechanical study of the gun was performed to ensure that the thermal stresses were well within the allowable limits and that copper erosion of the water channels would not occur

1 ms pulse beam generation and acceleration by photo-cathode RF gun

International Nuclear Information System (INIS)

Watanabe, Ken; Hayano, Hitoshi; Urakawa, Jyunji

2012-01-01

We report successful generation of 1 ms long pulse and multi-bunch electron beam by a normal conducting photo-cathode RF gun at KEK-STF (Superconducting accelerator Test Facility). The 1 ms long Pulse beam generated by the RF gun is delivered to the injection line to examine stable acceleration and precise RF control. The 1 ms pulse beam is also used to demonstrate high brightness X-ray generation by inverse laser Compton scattering which will be also carried out at STF, supported by MEXT Quantum Beam project. The RF gun cavity has been fabricated by DESY-FNAL-KEK collaboration. Performing high power RF process and ethanol rinse to the cavity, a stable operation of the cavity up to 4.0 MW RF input power with ∼1 ms pulse length was achieved by keeping even low dark current. The beam generation test has been started since February 2012, 1 ms pulse was generated in March 2012. We explain about the STF injector and report the basic property of this 1 ms beam generation. (author)

Instruments for assessing the burden of informal caregiving for stroke patients in clinical practice: a comparison of CSI, CRA, SCQ and self-rated burden

NARCIS (Netherlands)

van Exel, N. Job A.; Scholte op Reimer, Wilma J. M.; Brouwer, Werner B. F.; van den Berg, Bernard; Koopmanschap, Marc A.; van den Bos, Geertrudis A. M.

2004-01-01

Objective: To compare the feasibility, convergent and clinical validity of three commonly used burden scales: Caregiver Strain Index (CSI), Caregiver Reaction Assessment (CRA) and Sense of Competence Questionnaire (SCQ), with a self-developed single question on self-rated burden (SRB). Subjects:

Minimax robust relay selection based on uncertain long-term CSI

KAUST Repository

Nisar, Muhammad Danish

2014-02-01

Cooperative communications via multiple relay nodes is known to provide the benefits of increase diversity and coverage. Simultaneous transmission via multiple relays, however, requires strong coordination between nodes either in terms of slot-based transmission or distributed space-time (ST) code implementation. Dynamically selecting a single best relay out of multiple relays and then using it alone for cooperative transmission alleviates the need for this strong coordination while still reaping the benefits of increased diversity and coverage. In this paper, we consider the design of relay selection (RS) under an imperfect knowledge of long-term channel state information (CSI) at the relay nodes, and we pursue minimax optimization to arrive at a robust RS approach that promises the best guarantee on the worst-case end-to-end signal-to-noise ratio (SNR). We provide some intuitive examples and extensive simulation results, not only in terms of worst-case SNR performance but also in terms of average bit-error-rate (BER) performance, to demonstrate the benefits of the proposed minimax robust RS scheme. © 2013 IEEE.

Photomultiplier characteristics considerations for the deep underwater muon and neutrino detection system

International Nuclear Information System (INIS)

Leskovar, B.

1980-01-01

The results of an investigation of the characteristics of photomultipliers for the Deep Underwater Muon and Neutrino Detection (DUMAND) System are discussed. The pulse-height resolution, the afterpulsing phenomena and the gain sensitivity to the ambient magnetic field have been determined for large photocathode area photomultipliers. Furthermore, the transient time difference, the single photoelectron time spread, and the collection and photocathode quantum efficiency uniformity as a function of the position of the photocathode sensing area have been reviewed. Finally, an attempt has been made to estimate the photomultiplier reliability and its lifetime

Formation mechanism of SiC in C-Si system by ion irradiation

International Nuclear Information System (INIS)

Hishita, Shunichi; Aizawa, Takashi; Suehara, Shigeru; Haneda, Hajime

2003-01-01

The irradiation effects of 2 MeV He + , Ne + , and Ar + ions on the film structure of the C-Si system were investigated with RHEED and XPS. The ion dose dependence of the SiC formation was kinetically analyzed. The SiC formation at moderate temperature was achieved by 2 MeV ion irradiation when the thickness of the initial carbon films was appropriate. The evolution process of the SiC film thickness consisted of the 3 stages. The first stage was the steep increase of the SiC, and was governed by the inelastic collision. The second was the gentle increase of the SiC, and was governed by the diffusion. The last was the decrease of the SiC, and was caused by the sputtering. The formation mechanism of the SiC was discussed. (author)

A high speed digitizing photomultiplier tube base for the KTeV CsI calorimeter

International Nuclear Information System (INIS)

Whitmore, J.

1994-11-01

A circuit has been designed to digitize PMT signals over an 18-bit dynamic range with 8-bits of resolution. The crucial element of the circuit is the custom charge integrating and encoding (QIE) ASIC. This chip is designed to operate at rates up to 53 MHz, and, in conjunction with an 8-bit FADC, generates 12-bit floating point output. Bench tests of a 17-bit version of the digital base demonstrated excellent noise performance, linearity and pedestal and gain stability. Twenty-five channels of digitizing PMT bases have been built and used for readout of a CsI array in a test beam at CERN. Performance of these devices in a beam environment is discussed

Law & Order, CSI, and NCIS: The Association Between Exposure to Crime Drama Franchises, Rape Myth Acceptance, and Sexual Consent Negotiation Among College Students.

Science.gov (United States)

Hust, Stacey J T; Marett, Emily Garrigues; Lei, Ming; Ren, Chunbo; Ran, Weina

2015-01-01

Previous research has identified that exposure to the crime drama genre lowers rape myth acceptance and increases sexual assault prevention behaviors such as bystander intervention. However, recent content analyses have revealed marked differences in the portrayal of sexual violence within the top three crime drama franchises. Using a survey of 313 college freshmen, this study explores the influence of exposure to the three most popular crime drama franchises: Law & Order, CSI, and NCIS. Findings indicate that exposure to the Law & Order franchise is associated with decreased rape myth acceptance and increased intentions to adhere to expressions of sexual consent and refuse unwanted sexual activity; whereas exposure to the CSI franchise is associated with decreased intentions to seek consent and decreased intentions to adhere to expressions of sexual consent. Exposure to the NCIS franchise was associated with decreased intentions to refuse unwanted sexual activity. These results indicate that exposure to the specific content of each crime drama franchise may have differential results on sexual consent negotiation behaviors.

Conceptual design of a bright electron injector based on a laser-driven photocathode rf electron gun

International Nuclear Information System (INIS)

Chattopadhyay, S.; Chen, Y.J.; Hopkins, D.; Kim, K.J.; Kung, A.; Miller, R.; Sessler, A.; Young, T.

1988-09-01

Conceptual design of a bright electron injector for the 1 GeV high gradient test experiment, envisaged by the LLNL-SLAC-LBL collaboration on the Relativistic Klystron is presented. The design utilizes a high-brightness laser-driven rf photocathode electron gun, similar to the pioneering LANL early studies in concept (different parametrically however), together with achromatic magnetic bunching and transport systems and diagnostics. The design is performed with attention to possible use in an FEL as well. A simple but realistic analytic model including longitudinal and transverse space-charge and rf effects and extensive computer simulation form the basis of the parametric choice for the source. These parameters are used as guides for the design of the picosecond laser system and magnetic bunching section. 4 refs., 5 figs., 2 tabs

Adsorption of Cs(I), Sr(II), Eu(III), Co(II) and Cd(II) by Al2O3

International Nuclear Information System (INIS)

Shiao, S.Y.; Egozy, Y.; Meyer, R.E.

1981-01-01

Adsorption of Cs(I), Sr(II), Eu(III), Co(II) and Cd(II) by Al 2 O 3 was carried out over a wide range of NaCl concentration and solution pH. In the medium pH region (pH 5 to 9), adsorption depends strongly on pH and less on salt concentration. However, in the high pH region (pH above 9), the salt dependence of the distribution coefficient becomes important. (author)

Project of a photoelectron X-ray microscope on ACO storage ring

International Nuclear Information System (INIS)

Polack, F.; Lowenthal, S.

1983-01-01

A photoelectron X-ray microscope is described which is based on the principles of contact X-ray imaging and of image converters. An X-ray image is projected by a parallel X-ray beam on a thin transmission photocathode. The emitted electrons are accelerated and imaged at large magnification by an emission microscope. The instrument, which is presently under construction, is designed to provide high resolution. An electron velocity filter has been added to the usual cross-over aperture so as to reduce the spherochromatic aberration, and the cathode lens has been designed to reduce field curvature. Resolution and detection efficiency of Au and CsI cathodes are compared. The interest of the instrument for soft X-ray microscopy is briefly discussed. (orig.)

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.

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)

Characterization of capsaicin synthase and identification of its gene (csy1) for pungency factor capsaicin in pepper (Capsicum sp.)

Science.gov (United States)

Prasad, B. C. Narasimha; Kumar, Vinod; Gururaj, H. B.; Parimalan, R.; Giridhar, P.; Ravishankar, G. A.

2006-01-01

Capsaicin is a unique alkaloid of the plant kingdom restricted to the genus Capsicum. Capsaicin is the pungency factor, a bioactive molecule of food and of medicinal importance. Capsaicin is useful as a counterirritant, antiarthritic, analgesic, antioxidant, and anticancer agent. Capsaicin biosynthesis involves condensation of vanillylamine and 8-methyl nonenoic acid, brought about by capsaicin synthase (CS). We found that CS activity correlated with genotype-specific capsaicin levels. We purified and characterized CS (≈35 kDa). Immunolocalization studies confirmed that CS is specifically localized to the placental tissues of Capsicum fruits. Western blot analysis revealed concomitant enhancement of CS levels and capsaicin accumulation during fruit development. We determined the N-terminal amino acid sequence of purified CS, cloned the CS gene (csy1) and sequenced full-length cDNA (981 bp). The deduced amino acid sequence of CS from full-length cDNA was 38 kDa. Functionality of csy1 through heterologous expression in recombinant Escherichia coli was also demonstrated. Here we report the gene responsible for capsaicin biosynthesis, which is unique to Capsicum spp. With this information on the CS gene, speculation on the gene for pungency is unequivocally resolved. Our findings have implications in the regulation of capsaicin levels in Capsicum genotypes. PMID:16938870

Measurements of the radiolytic oxidation of aqueous CsI using a sparging apparatus

Energy Technology Data Exchange (ETDEWEB)

Ashmore, C B; Brown, D; Sims, H E [AEA Technology, Harwell (United Kingdom); Gwyther, J R [NE plc Berkeley Technology Centre, Berkeley (United Kingdom)

1996-12-01

Radiolytic oxidation is considered to be the main mechanism for the formation of I{sub 2} from aqueous CsI in containment of a water cooled reactor after a LOCA. Despite the amount of study over the last 60 years on the radiation chemistry of iodine there has been no consistent set of experiments spanning a wide enough range of conditions to verify models with confidence. This paper describes results from a set of experiments carried out in order to remedy this deficiency. In this work the rate of evolution of I{sub 2} from sparged irradiated CsI solution labeled with {sup 131}I was measured on-line over a range of conditions. This work involved the measurement of the effects of pH, temperature, O{sub 2} concentration, I{sup -} concentration, phosphate concentration, dose-rate and impurities on the rate of evolution of I{sub 2}. The range of conditions was chosen in order to span as closely as possible conditions expected in a LOCA but also to help to elucidate some of the mechanisms especially at high pH. pH was found to be a very important factor influencing iodine volatility, over the temperature range studied the extent of oxidation reduced with temperature but this was compensated for by the decrease in partition coefficient. Oxygen concentration was more important in solutions not containing phosphate. The fractional oxidation was not particularly dependent on iodide concentration but G{sub I2} was very dependent on [I{sup -}]. There was no effect of added impurities, Fe, Mn, Mo or organics although in separate work silver was found to have a very important effect. During attempts to interpret the data it was found that it was necessary to include the iodine atom as a volatile species with a partition coefficient of 1.9 taken from thermodynamic data. The modelling work is described in a separate paper. (author) 15 figs., 1 tab., 19 refs.

Studies on a modular high-energy photon spectrometer of pure CsI scintillators

International Nuclear Information System (INIS)

Kopyto, D.

1994-04-01

Aim of the present thesis is the optimization of components for the construction of a high-energy photon spectrometer of pure CsI for the detection of the neutral pseudoscalar mesons π 0 , η, and η' at COSY. These mesons are distinguished by their decay into two γ quanta and can therefore be detected by means of a photon spectrometer. A concept of a 2-arm shower counter of pure CsI is presented. Conclusions on the energy resolution of such a calorimeter shall yield a test module, which is constructed of 5.5 CsI(pure) pyramide trunk, each of which possesses a length of 30 cm and an angular acceptance of 6 .6 . The geometry of the moduls is formed in such a way that its extension to a 2-arm shower counter is possible at any time. Hitherto 14 by teflon foils wrapped up crystals for the test module were tested. Their energy resolution varies at 0.66 MeV between 20 and 25 % FWHM. Furthermore a method was found, which allows to trim the position dependence to the required values. So for the position dependence of a crystal even a value of 1.1 % could be reached. The energy resolution amounted thereby to 22 % FWHM. A measurement of the energy resolution with 20 MeV protons yielded a value of 7 %. For the energy calibration of the single detector elements in a dynamic range between 1 MeV and 12 GeV with low-energy γ sources the charge response function of the photoelectron multiplier to be applied in the test module was determined in dependence on the light intensity. The measurement resulted that the photomultiplier at 40 MeV (related to a CsI(pure) reference crystal with an about twofold so high efficiency of the detectable light in comparison to the long pyramide trunks) deviates by 4 % and at 300 MeV by 38 % from the linear behaviour, while it at 500 MeV shows a deviation of 50 %

Measurements of the radiolytic oxidation of aqueous CsI using a sparging apparatus

International Nuclear Information System (INIS)

Ashmore, C.B.; Brown, D.; Sims, H.E.; Gwyther, J.R.

1996-01-01

Radiolytic oxidation is considered to be the main mechanism for the formation of I 2 from aqueous CsI in containment of a water cooled reactor after a LOCA. Despite the amount of study over the last 60 years on the radiation chemistry of iodine there has been no consistent set of experiments spanning a wide enough range of conditions to verify models with confidence. This paper describes results from a set of experiments carried out in order to remedy this deficiency. In this work the rate of evolution of I 2 from sparged irradiated CsI solution labeled with 131 I was measured on-line over a range of conditions. This work involved the measurement of the effects of pH, temperature, O 2 concentration, I - concentration, phosphate concentration, dose-rate and impurities on the rate of evolution of I 2 . The range of conditions was chosen in order to span as closely as possible conditions expected in a LOCA but also to help to elucidate some of the mechanisms especially at high pH. pH was found to be a very important factor influencing iodine volatility, over the temperature range studied the extent of oxidation reduced with temperature but this was compensated for by the decrease in partition coefficient. Oxygen concentration was more important in solutions not containing phosphate. The fractional oxidation was not particularly dependent on iodide concentration but G I2 was very dependent on [I - ]. There was no effect of added impurities, Fe, Mn, Mo or organics although in separate work silver was found to have a very important effect. During attempts to interpret the data it was found that it was necessary to include the iodine atom as a volatile species with a partition coefficient of 1.9 taken from thermodynamic data. The modelling work is described in a separate paper. (author) 15 figs., 1 tab., 19 refs

Diffusion of Na(I), Cs(I), Sr(II) and Eu(III) in smectite rich natural clay.

Science.gov (United States)

Kasar, Sharayu; Kumar, Sumit; Bajpai, R K; Tomar, B S

2016-01-01

Diffusion of Na(I), Cs(I), Sr(II) and Eu(III) in smectite rich natural clay, proposed as a backfill material in the Indian geological repository, was studied using the out-diffusion method. Radiotracers (22)Na, (137)Cs, (85)Sr and (154)Eu were used; the first three are carrier-free enabling experimental work at sub-micromolar metal ion concentration, and Eu(III) tracer (154)Eu was used at sub millimolar concentration. An out-diffusion methodology, wherein a thin planar source of radioactivity placed between two clay columns diffuses out, was used to obtain the apparent diffusion coefficient (Da) values. This methodology enabled determination of diffusion coefficient even for strongly sorbing (154)Eu. Da values for (22)Na, (137)Cs, (85)Sr and (154)Eu were 2.35 (±0.14) × 10(-11), 2.65 (±0.09) × 10(-12), 3.32 (±0.15) × 10(-11) and 1.23 (±0.15) × 10(-13) m(2) s(-1), respectively. Da values were found to be in fair agreement with literature data reported for similar mineralogical sediments. Sorption of radionuclides on the clay was also determined in the present study and differences in Da values were rationalized on the basis of sorption data. Distribution ratios (Kd) for Cs(I) and Eu(III) were higher than that for Sr(II), which in turn was higher than that for Na(I). Copyright © 2015 Elsevier Ltd. All rights reserved.

Emittance measurement and optimization for the photocathode RF gun with laser profile shaping

International Nuclear Information System (INIS)

Liu Shengguang; Masafumi Fukuda; Sakae Araki; Nobuhiro Terunuma; Junji Urakawa

2010-01-01

The Laser Undulator Compact X-ray source (LUCX) is a test bench for a compact high brightness X-ray generator, based on inverse Compton Scattering at KEK, which requires high intensity multi-bunch trains with low transverse emittance. A photocathode RF gun with emittance compensation solenoid is used as an electron source. Much endeavor has been made to increase the beam intensity in the multi-bunch trains. The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects, so that the field gradient on the cathode surface is relatively higher when the forward RF power into gun cavity is not high enough. A laser profile shaper is employed to convert the driving laser profile from Gaussian into uniform. In this research we seek to find the optimized operational conditions for the decrease of the transverse emittance. With the uniform driving laser and the unbalanced RF gun, the RMS transverse emittance of a 1 nC bunch has been improved effectively from 5.46 πmm.mrad to 3.66 πmm·mrad. (authors)

CSI Frequency Domain Fingerprint-Based Passive Indoor Human Detection

Directory of Open Access Journals (Sweden)

Chong Han

2018-04-01

Full Text Available Passive indoor personnel detection technology is now a hot topic. Existing methods have been greatly influenced by environmental changes, and there are problems with the accuracy and robustness of detection. Passive personnel detection based on Wi-Fi not only solves the above problems, but also has the advantages of being low cost and easy to implement, and can be better applied to elderly care and safety monitoring. In this paper, we propose a passive indoor personnel detection method based on Wi-Fi, which we call FDF-PIHD (Frequency Domain Fingerprint-based Passive Indoor Human Detection. Through this method, fine-grained physical layer Channel State Information (CSI can be extracted to generate feature fingerprints so as to help determine the state in the scene by matching online fingerprints with offline fingerprints. In order to improve accuracy, we combine the detection results of three receiving antennas to obtain the final test result. The experimental results show that the detection rates of our proposed scheme all reach above 90%, no matter whether the scene is human-free, stationary or a moving human presence. In addition, it can not only detect whether there is a target indoors, but also determine the current state of the target.

Analysis of customer satisfaction in hospital by using Importance-Performance Analysis (IPA and Customer Satisfaction Index (CSI

Directory of Open Access Journals (Sweden)

Helia Vembri Noor

2018-01-01

Full Text Available As a major health referral centre, the hospital demanded to provide comprehensive services provided by a multi-disciplinary team according to the needs of patient. In the expansion of a growing number of hospitals in Yogyakarta especially Sleman area where retreat acquire customers even more stringent, it is necessary to increase the quality of services. There are five determinants of service quality namely: reliability, responsiveness, assurance, empathy, and tangible. Collecting data is done by observation and distributing questionnaires to 70 respondents, and Importance-Performance Analysis and Customer Satisfaction Index are used to determine satisfaction level of outpatients. As a results, six out of twenty attributes need improvement, namely: a The condition of the hospital is clean, comfortable and tidy; b Guidance and information boards poly is easy to see and read; c The ease and accuracy of obtaining information for patients (referrals, lab results, etc.; d The hospital staff has a quick response to the needs of patients; e Attention physicians in managing patients and willingness to provide a particular time for consultation; and f The prescribed medication is suitable and safe. It is known that the value of CSI by 76% means the service is not satisfied the patient.

Exact Outage Probability of Dual-Hop CSI-Assisted AF Relaying Over Nakagami-m Fading Channels

KAUST Repository

Xia, Minghua

2012-10-01

In this correspondence, considering dual-hop channel state information (CSI)-assisted amplify-and-forward (AF) relaying over Nakagami- m fading channels, the cumulative distribution function (CDF) of the end-to-end signal-to-noise ratio (SNR) is derived. In particular, when the fading shape factors m1 and m2 at consecutive hops take non-integer values, the bivariate H-function and G -function are exploited to obtain an exact analytical expression for the CDF. The obtained CDF is then applied to evaluate the outage performance of the system under study. The analytical results of outage probability coincide exactly with Monte-Carlo simulation results and outperform the previously reported upper bounds in the low and medium SNR regions.

PILA: Sub-Meter Localization Using CSI from Commodity Wi-Fi Devices.

Science.gov (United States)

Tian, Zengshan; Li, Ze; Zhou, Mu; Jin, Yue; Wu, Zipeng

2016-10-10

The aim of this paper is to present a new indoor localization approach by employing the Angle-of-arrival (AOA) and Received Signal Strength (RSS) measurements in Wi-Fi network. To achieve this goal, we first collect the Channel State Information (CSI) by using the commodity Wi-Fi devices with our designed three antennas to estimate the AOA of Wi-Fi signal. Second, we propose a direct path identification algorithm to obtain the direct signal path for the sake of reducing the interference of multipath effect on the AOA estimation. Third, we construct a new objective function to solve the localization problem by integrating the AOA and RSS information. Although the localization problem is non-convex, we use the Second-order Cone Programming (SOCP) relaxation approach to transform it into a convex problem. Finally, the effectiveness of our approach is verified based on the prototype implementation by using the commodity Wi-Fi devices. The experimental results show that our approach can achieve the median error 0.7 m in the actual indoor environment.

On-line induced absorption measurement on PbWO.sub.4./sub., YAlO.sub.3./sub.:Ce and CsI scintillating crystals

Czech Academy of Sciences Publication Activity Database

Šulc, M.; Nikl, Martin; Vognar, M.; Blažek, K.; Nejezchleb, K.; Boháček, Pavel; Nitsch, Karel; Kobayashi, M.; Usuki, Y.; Shen, D.

2004-01-01

Roč. 38, - (2004), s. 393-396 ISSN 1350-4487 R&D Projects: GA ČR(CZ) GA202/01/0753 Grant - others:NATO SfP(XX) 973510-Scintillators Institutional research plan: CEZ:AV0Z1010914 Keywords : radiation damage * PbWO 4 scintillator * YAlO 3 :Ce * CsI Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.664, year: 2004

Highly segmented large-area hybrid photodiodes with bialkali photocathodes and enclosed VLSI readout electronics

CERN Document Server

Braem, André; Filthaut, Frank; Go, A; Joram, C; Weilhammer, Peter; Wicht, P; Dulinski, W; Séguinot, Jacques; Wenzel, H; Ypsilantis, Thomas

2000-01-01

We report on the principles, design, fabrication, and operation of a highly segmented, large-area hybrid photodiode, which is being developed in the framework of the LHCb RICH project. The device consists of a cylindrical, 127 mm diameter vacuum envelope capped with a spherical borosilicate UV-glass entrance window, with an active-to-total-area fraction of 81A fountain-focusing electron optics is used to demagnify the image onto a 50 mm diameter silicon sensor, containing 2048 pads of size 1*1 mm/sup 2/. (10 refs).

CSI, de la série au jeu : « a more immersive experience »

OpenAIRE

Monnet-Cantagrel, Hélène

2016-01-01

CSI est une franchise de séries policières construites autour d’un même principe narratif de résolution des enquêtes par les techniques scientifiques d’investigation. D’objectif ouvertement commercial, de l’ordre du marketing, et répétitives, les franchises de médias n’ont pas toujours bonne presse, accusées de consacrer la transformation des biens culturels en produits industriels. Les franchises sont pourtant une pratique de plus en plus fréquente à la télévision - américaine - qui, depuis ...

Deposition of Y thin films by nanosecond UV pulsed laser ablation for photocathode application

International Nuclear Information System (INIS)

Lorusso, A.; Anni, M.; Caricato, A.P.; Gontad, F.; Perulli, A.; Taurino, A.; Perrone, A.; Chiadroni, E.

2016-01-01

In this work, yttrium (Y) thin films have been deposited on Si (100) substrates by the pulsed laser deposition technique. Ex-situ morphological, structural and optical characterisations of such films have been performed by scanning electron microscopy, X-ray diffractometry, atomic force microscopy and ellipsometry. Polycrystalline films with a thickness of 1.2 μm, homogenous with a root mean square roughness of about 2 nm, were obtained by optimised laser irradiation conditions. Despite the relatively high thickness, the films resulted very adherent to the substrates. The high quality of such thin films is important to the synthesis of metallic photocathodes based on Y thin film, which could be used as electron sources of high photoemission performance in radio-frequency guns. - Highlights: • Pulsed laser deposition of Yttrium thin films is investigated. • 1.2 μm thick films were deposited with very low RMS roughness. • The Y thin films were very adherent to the Si substrate • Optical characterisation showed a very high absorption coefficient for the films.

Deposition of Y thin films by nanosecond UV pulsed laser ablation for photocathode application

Energy Technology Data Exchange (ETDEWEB)

Lorusso, A. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Istituto Nazionale di Fisica Nucleare-Lecce, 73100 Lecce (Italy); Anni, M. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Caricato, A.P. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Istituto Nazionale di Fisica Nucleare-Lecce, 73100 Lecce (Italy); Gontad, F., E-mail: francisco.gontad@le.infn.it [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Istituto Nazionale di Fisica Nucleare-Lecce, 73100 Lecce (Italy); Perulli, A. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Taurino, A. [National Research Council, Institute for Microelectronics & Microsystems, 73100 Lecce (Italy); Perrone, A. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Istituto Nazionale di Fisica Nucleare-Lecce, 73100 Lecce (Italy); Chiadroni, E. [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, 00044 Frascati (Italy)

2016-03-31

In this work, yttrium (Y) thin films have been deposited on Si (100) substrates by the pulsed laser deposition technique. Ex-situ morphological, structural and optical characterisations of such films have been performed by scanning electron microscopy, X-ray diffractometry, atomic force microscopy and ellipsometry. Polycrystalline films with a thickness of 1.2 μm, homogenous with a root mean square roughness of about 2 nm, were obtained by optimised laser irradiation conditions. Despite the relatively high thickness, the films resulted very adherent to the substrates. The high quality of such thin films is important to the synthesis of metallic photocathodes based on Y thin film, which could be used as electron sources of high photoemission performance in radio-frequency guns. - Highlights: • Pulsed laser deposition of Yttrium thin films is investigated. • 1.2 μm thick films were deposited with very low RMS roughness. • The Y thin films were very adherent to the Si substrate • Optical characterisation showed a very high absorption coefficient for the films.

R and D on high momentum particle identification with a pressurized Cherenkov radiator

Energy Technology Data Exchange (ETDEWEB)

Agócs, A.G. [Wigner RCP of the HAS, Budapest (Hungary); Barile, F. [INFN Sezione di Bari and Universit´a degli Studi di Bari, Dipartimento Interateneo di Fisica M. Merlin, Bari (Italy); Barnaföldi, G.G. [Wigner RCP of the HAS, Budapest (Hungary); Bellwied, R. [University of Houston, Houston (United States); Bencédi, G.; Bencze, G.; Berényi, D.; Boldizsár, L. [Wigner RCP of the HAS, Budapest (Hungary); Chattopadhyay, S. [Saha Institute of Nuclear Physics, Kolkata (India); Chinellato, D.D. [University of Houston, Houston (United States); Cindolo, F. [University of Salerno, Salerno (Italy); Cossyleon, K. [Chicago State University, Chicago, IL (United States); Das, D.; Das, K.; Das-Bose, L. [Saha Institute of Nuclear Physics, Kolkata (India); De Cataldo, G.; Di Bari, D. [INFN Sezione di Bari and Universit´a degli Studi di Bari, Dipartimento Interateneo di Fisica M. Merlin, Bari (Italy); Di Mauro, A. [CERN, CH1211 Geneva 23 (Switzerland); Futó, E. [Wigner RCP of the HAS, Budapest (Hungary); Garcia-Solis, E. [Chicago State University, Chicago, IL (United States); and others

2014-12-01

We report on the R and D results for a Very High Momentum Particle Identification (VHMPID) detector, which was proposed to extend the charged hadron track-by-track identification in the momentum range from 5 to 25 GeV/c in the ALICE experiment at CERN. It is a RICH detector with focusing geometry using pressurized perfluorobutane (C{sub 4}F{sub 8}O) as a Cherenkov radiator. A MWPC with a CsI photocathode was investigated as the baseline option for the photon detector. The results of beam tests performed on RICH prototypes using both liquid C{sub 6}F{sub 14} radiator (in proximity focusing geometry for reference measurements) and pressurized C{sub 4}F{sub 8}O gaseous radiator will be shown in this paper. In addition, we present studies of a CsI based gaseous photon detector equipped with a MWPC having an adjustable anode–cathode gap, aiming at the optimization of the chamber layout and performance in the detection of single photoelectrons. - Highlights: • Pressurized and heated C{sub 4}F{sub 8}O was used as Cherenkov radiator gas. • A Cherenkov angle resolution of 1.5 mrad was achieved. • The separation of electrons, pions, and kaons in a large momentum range is shown.

Experimental studies of emittance growth and energy spread in a photocathode RF gun

International Nuclear Information System (INIS)

Yang, J.; Sakai, F.; Okada, Y.; Yorozu, M.; Yanagida, T.; Endo, A.

2002-01-01

In this paper we report on a low emittance electron source, based on a photocathode RF gun, a solenoid magnet and a subsequent linac. The dependencies of the beam transverse emittance and relative energy spread with respect to the laser injection phase of the radio-frequency (RF) gun, the RF phase of the linac and the bunch charge were investigated experimentally. It was found that a lower beam emittance is observed when the laser injection phase in the RF gun is low. The emittance increases almost linearly with the bunch charge under a constant solenoid magnetic field. The corrected relative energy spread of the beam is not strongly dependent on the bunch charge. Finally, an optimal normalized rms transverse emittance of 1.91±0.28 πmm mrad at a bunch charge of 0.6 nC was obtained when the RF gun was driven by a picosecond Nd:YAG laser. A corrected relative rms energy spread of 0.2-0.25% at a bunch charge of 0.3-2 nC was obtained after the beam was accelerated to 14 MeV by the subsequent linac

Experimental studies of emittance growth and energy spread in a photocathode RF gun

CERN Document Server

Yang, J; Okada, Y; Yorozu, M; Yanagida, T; Endo, A

2002-01-01

In this paper we report on a low emittance electron source, based on a photocathode RF gun, a solenoid magnet and a subsequent linac. The dependencies of the beam transverse emittance and relative energy spread with respect to the laser injection phase of the radio-frequency (RF) gun, the RF phase of the linac and the bunch charge were investigated experimentally. It was found that a lower beam emittance is observed when the laser injection phase in the RF gun is low. The emittance increases almost linearly with the bunch charge under a constant solenoid magnetic field. The corrected relative energy spread of the beam is not strongly dependent on the bunch charge. Finally, an optimal normalized rms transverse emittance of 1.91+-0.28 pi mm mrad at a bunch charge of 0.6 nC was obtained when the RF gun was driven by a picosecond Nd:YAG laser. A corrected relative rms energy spread of 0.2-0.25% at a bunch charge of 0.3-2 nC was obtained after the beam was accelerated to 14 MeV by the subsequent linac.

Temporal laser pulse shaping for RF photocathode guns: the cheap and easy way using UV birefringent crystals

International Nuclear Information System (INIS)

Power, J.G.; Jing, C.

2009-01-01

We report experimental investigations into a new technique for achieving temporal laser pulse shaping for RF photocathode gun applications using inexpensive UV birefringent crystals. Exploiting the group velocity mismatch between the two different polarizations of a birefringent crystal, a stack of UV pulses can be assembled into the desired temporal pulse shape. The scheme is capable of generating a variety of temporal pulse shapes including: (i) flat-top pulses with fast rise-time and variable pulse duration. (ii) microbunch trains, and (iii) ramped pulse generation. We will consider two applications for beam generation at the Argonne Wakefield Accelerator (AWA) including a flat-top laser pulse for low emittance production and matched bunch length for enhanced transformer ratio production. Streak camera measurements of the temporal profiles generated with a 2-crystal set and a 4-crystal set are presented.

Outage Probability versus Fairness Trade-off in Opportunistic Relay Selection with Outdated CSI

Directory of Open Access Journals (Sweden)

Vicario JoseLopez

2009-01-01

Full Text Available We analyze the existing trade-offs in terms of system performance versus fairness of a cooperative system based on opportunistic relay selection (ORS and with outdated channel state information (CSI. In particular, system performance is analytically evaluated in terms of outage probability, and the fairness behavior is assessed based on the power consumption at the different relays. In order to improve the fairness behavior of ORS while keeping the selection diversity gain, we propose a relay selection mechanism where the relay with the highest normalized signal-to-noise ratio (SNR is selected for relaying the source's information. The proposed strategy is compared with existing relay selection strategies by adopting a novel graphical representation inspired by expected profit versus risk plots used in modern portfolio theory. As shown in the paper, this strategy allows operating the system in more favorable points of the outage versus fairness region.

Electrochemically deposited Cu{sub 2}O cubic particles on boron doped diamond substrate as efficient photocathode for solar hydrogen generation

Energy Technology Data Exchange (ETDEWEB)

Mavrokefalos, Christos K. [Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, England (United Kingdom); Hasan, Maksudul, E-mail: maksudul.hasan@chem.ox.ac.uk [Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, England (United Kingdom); Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland); Rohan, James F. [Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland); Compton, Richard G. [Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, England (United Kingdom); Foord, John S., E-mail: john.foord@chem.ox.ac.uk [Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, England (United Kingdom)

2017-06-30

Highlights: • Fabrication of low-cost photocathode by electrochemical method is described. • Boron-doped diamond is presented as catalyst support. • NiO nanoparticles on Cu{sub 2}O surface enhances photocurrent and electrode stability. • Synergy of metallic interaction between Cu and Ni leads to high efficiency. - Abstract: Herein, we report a novel photocathode for the water splitting reaction. The electrochemical deposition of Cu{sub 2}O particles on boron doped diamond (BDD) electrodes and the subsequent decoration with NiO nanoparticles by a dip coating method to act as co-catalyst for hydrogen evolution reaction is described. The morphology analysis by scanning electron microscope (SEM) revealed that Cu{sub 2}O particles are cubic and decorated sporadically with NiO nanoparticles. X-ray photoelectron spectroscopy (XPS) confirmed the electronic interaction at the interface between Cu{sub 2}O and NiO through a binding energy shift of the main Cu 2p peak. The photoelectrochemical (PEC) performance of NiO-Cu{sub 2}O/BDD showed a much higher current density (−0.33 mA/cm{sup 2}) and photoconversion efficiency (0.28%) compared to the unmodified Cu{sub 2}O/BDD electrode, which are only −0.12 mA/cm{sup 2} and 0.06%, respectively. The enhancement in PEC performance is attributable to the synergy of NiO as an electron conduction mediator leading to the enhanced charge separation and transfer to the reaction interface for hydrogen evolution as evidenced by electrochemical impedance spectroscopy (EIS) and charge carrier density calculation. Stability tests showed that the NiO nanoparticles loading content on Cu{sub 2}O surface is a crucial parameter in this regard.

CSI-Chocolate Science Investigation and the Case of the Recipe Rip-Off: Using an Extended Problem-Based Scenario to Enhance High School Students' Science Engagement

Science.gov (United States)

Marle, Peter D.; Decker, Lisa; Taylor, Victoria; Fitzpatrick, Kathleen; Khaliqi, David; Owens, Janel E.; Henry, Renee M.

2014-01-01

This paper discusses a K-12/university collaboration in which students participated in a four-day scenario-based summer STEM (science, technology, engineering, and mathematics) camp aimed at making difficult scientific concepts salient. This scenario, Jumpstart STEM-CSI: Chocolate Science Investigation (JSCSI), used open- and guided-inquiry…

CONTAIN code calculations of the effects on the source term of CsI to I/sub 2/ conversion due to severe hydrogen burns

International Nuclear Information System (INIS)

Valdez, G.D.; Williams, D.C.

1986-01-01

In experiments conducted at Sandia National Laboratories large amounts of elemental iodine were produced when CsI-Al 2 O 3 aerosol was exposed to hydrogen/air combustion. To evaluate some of the implications of the iodide conversion (observed to occur with up to 75% efficiency) for the severe accident source term, computational simulations of representative accident sequences were conducted with the CONTAIN code. The following conclusions can be drawn from this preliminary source term assessment: (1) If the containment sprays are inoperative during the accident, or failed by the hydrogen burn, the late-time source term is almost tripled when the iodide is converted to I 2 . (2) With the sprays active, the amount released without conversion of the CsI aerosol is 63% higher than for the case when conversion occurs. (3) For the case where CsI is converted to I 2 continued operation of the sprays reduces the release by a factor of 40, relative to the case in which the sprays fail at the time of the hydrogen burn. When there is no conversion, the reduction factor for continued spray operation is about a factor of 9, relative to the failed spray case

On the secrecy capacity of the broadcast wiretap channel with limited CSI feedback

KAUST Repository

Hyadi, Amal

2016-10-27

In this paper, we investigate the problem of secure broadcasting over block-fading channels with limited channel knowledge at the transmitter. More particularly, we analyze the effect of having imperfect channel state information (CSI) via a finite rate feedback on the throughput of a broadcast channel where the transmission is intended for multiple legitimate receivers in the presence of an eavesdropper. First, we partially characterize the ergodic secrecy capacity of the system when the source broadcasts the same information to all the receivers, i.e., common message transmission. Then, we look at the independent messages case, where the transmitter broadcasts multiple independent messages to the legitimate receivers. For this case, we present lower and upper bounds on the ergodic secrecy sum-capacity. In both scenarios, we show that the proposed lower and upper bounds coincide asymptotically as the capacity of the feedback links becomes large, hence, fully characterizing the secrecy capacity in this case.

On the secrecy capacity of the broadcast wiretap channel with limited CSI feedback

KAUST Repository

Hyadi, Amal; Rezki, Zouheir; Alouini, Mohamed-Slim

2016-01-01

In this paper, we investigate the problem of secure broadcasting over block-fading channels with limited channel knowledge at the transmitter. More particularly, we analyze the effect of having imperfect channel state information (CSI) via a finite rate feedback on the throughput of a broadcast channel where the transmission is intended for multiple legitimate receivers in the presence of an eavesdropper. First, we partially characterize the ergodic secrecy capacity of the system when the source broadcasts the same information to all the receivers, i.e., common message transmission. Then, we look at the independent messages case, where the transmitter broadcasts multiple independent messages to the legitimate receivers. For this case, we present lower and upper bounds on the ergodic secrecy sum-capacity. In both scenarios, we show that the proposed lower and upper bounds coincide asymptotically as the capacity of the feedback links becomes large, hence, fully characterizing the secrecy capacity in this case.

[Overload in the informal caregivers of patients with multiple comorbidities in an urban area].

Science.gov (United States)

Álvarez-Tello, Margarita; Casado-Mejía, Rosa; Ortega-Calvo, Manuel; Ruiz-Arias, Esperanza

2012-01-01

The aim of the study was, to determine the profile of the family caregiver of patients with multiple pathologies, identify factors associated with overload, and construct predictive models using items from the Caregiver Strain Index (CSI). A cross-sectional study of caregivers of patients with multiple comorbidities who attended an urban health centre. Data were collected from health records and questionnaires (Barthel index, Pfeiffer index, and CSI). Statistical analysis was performed using measures of central tendency and dispersion, and by building multivariate models with binary logistic regression with the CSI items as predictors (program R version 2.14.0). The sample included 67 caregivers, with a mean age of 64.69 years (standard deviation=12.71, median 62 years), of whom 74.6% were women, 35.8% were wives, and 32.8% were daughters. The level of dependence of the patients cared for was total/severe in 77.6%, and moderate in 12% (Barthel), and 47.8% had some level of cognitive impairment (Pfeiffer). A CSI equal or greater than 7 was seen in 47.8% of caregivers, identifying life problems in more than 40% of them such as, restriction of social life, physical exertion, discomfort with change, bad behaviour, personal and family emotional changes, and sleep disturbances. Item 4 of the CSI, analysing the social restriction, was the one that showed a greater significance in the predictive multivariate model. Item 12 (economic burden) was the most significant with age in patients with cognitive impairment. Women tend to take the role of caregiver at an earlier age than men in the urban environment studied, and items from CSI showed that items 4 (social restrictions) and 12 (economic burden) have more significance in the predictive models constructed with Binary Logistic Regression. Copyright © 2012 Elsevier España, S.L. All rights reserved.

Design of a high repetition rate S-band photocathode gun

International Nuclear Information System (INIS)

Han Janghui; Cox, Matthew; Huang, Houcheng; Pande, Shivaji

2011-01-01

Photocathode RF guns have been developed in many laboratories for generating high quality electron beams for free-electron lasers based on linear accelerators. Such guns can generate electron beams with an exceptionally high peak current as well as a small transverse emittance. Their applications have been recently expanded for ultrafast electron diffraction, coherent terahertz radiation, and X-ray or γ-ray radiation by Compton scattering. In this paper, we design an S-band normal-conducting gun with capabilities of high quality beam generation and high repetition rate operation. The RF design and thermal analysis of the gun cavity and coupler are introduced. Optimal position of the gun focusing solenoid for low emittance beam generation is found by performing particle tracking simulations. Then, the gun system is designed to be able to afford the optimal solenoid position. The cooling-water channel surrounding the gun cavity and coupler is designed and analyzed numerically. The pressure in the gun is simulated with a vacuum model containing the detailed inner structure of the gun. An injector for a free-electron laser application is designed by using this gun and the beam dynamics simulation is shown. A cold test with a prototype gun for confirmation of the RF design is reported. - Highlights: → We design an S-band gun for low emittance beam generation and high repetition rate operation. → The RF design and thermal analysis of the gun cavity and coupler are studied. → An FEL injector is designed by using this gun and the beam dynamics simulation is shown. → A cold test with a prototype gun for confirmation of the RF design is reported.

Microhydration of caesium compounds: Cs, CsOH, CsI and Cs₂I₂ complexes with one to three H₂O molecules of nuclear safety interest.

Science.gov (United States)

Sudolská, Mária; Cantrel, Laurent; Cernušák, Ivan

2014-04-01

Structure and thermodynamic properties (standard enthalpies of formation and Gibbs free energies) of hydrated caesium species of nuclear safety interest, Cs, CsOH, CsI and its dimer Cs₂I₂, with one up to three water molecules, are calculated to assess their possible existence in severe accident occurring to a pressurized water reactor. The calculations were performed using the coupled cluster theory including single, double and non-iterative triple substitutions (CCSD(T)) in conjunction with the basis sets (ANO-RCC) developed for scalar relativistic calculations. The second-order spin-free Douglas-Kroll-Hess Hamiltonian was used to account for the scalar relativistic effects. Thermodynamic properties obtained by these correlated ab initio calculations (entropies and thermal capacities at constant pressure as a function of temperature) are used in nuclear accident simulations using ASTEC/SOPHAEROS software. Interaction energies, standard enthalpies and Gibbs free energies of successive water molecules addition determine the ordering of the complexes. CsOH forms the most hydrated stable complexes followed by CsI, Cs₂I₂, and Cs. CsOH still exists in steam atmosphere even at quite high temperature, up to around 1100 K.

3D Imaging of Dielectric Objects Buried under a Rough Surface by Using CSI

Directory of Open Access Journals (Sweden)

Evrim Tetik

2015-01-01

Full Text Available A 3D scalar electromagnetic imaging of dielectric objects buried under a rough surface is presented. The problem has been treated as a 3D scalar problem for computational simplicity as a first step to the 3D vector problem. The complexity of the background in which the object is buried is simplified by obtaining Green’s function of its background, which consists of two homogeneous half-spaces, and a rough interface between them, by using Buried Object Approach (BOA. Green’s function of the two-part space with planar interface is obtained to be used in the process. Reconstruction of the location, shape, and constitutive parameters of the objects is achieved by Contrast Source Inversion (CSI method with conjugate gradient. The scattered field data that is used in the inverse problem is obtained via both Method of Moments (MoM and Comsol Multiphysics pressure acoustics model.

Impact of one-dimensional photonic crystal back reflector in thin-film c-Si solar cells on efficiency

Science.gov (United States)

Jalali, Tahmineh

2018-05-01

In this work, the effect of one-dimensional photonic crystal on optical absorption, which is implemented at the back side of thin-film crystalline silicon (c-Si) solar cells, is extensively discussed. The proposed structure acts as a Bragg reflector which reflects back light to the active layer as well as nanograting which couples the incident light to enhance optical absorption. To understand the optical mechanisms responsible for the enhancement of optical absorption, quantum efficiency and current density for all structures are calculated and the effect of influential parameters, such as grating period is investigated. The results confirm that our proposed structure have a great deal for substantial efficiency enhancement in a broad range from 400 to 1100 nm.

Trends in the development of large area photon detectors for Cherenkov light imaging applications

CERN Document Server

Nappi, E

2003-01-01

Since the successful operations of hi-tech devices at OMEGA, DELPHI and SLD, the technique of Cherenkov light imaging has gone through an impressive and fruitful evolution driven by the conception of novel large area photon detectors. The well-assessed potentialities of thin CsI films, employed as reflective photoconverters in gas counters operated at atmospheric pressure, will be compared with the promising features of hybrid and multianode vacuum photomultipliers. Recently proposed single-photon gaseous detectors based on GEMs will also be reviewed.

A low-power RF system with accurate synchronization for a S-band RF-gun using a laser-triggered photocathode

International Nuclear Information System (INIS)

Otake, Y.; Naito, T.; Shintake, T.; Takata, K.; Takeuchi, Y.; Urakawa, J.; Yoshioka, M.; Akiyama, H.

1992-01-01

An S-band RF-gun using a laser-triggered photocathode and its low-power RF system have been constructed. The main elements of the low-power RF system comprise a 600-W amplifier, an amplitude modulator, a phase detector, a phase shifter and a frequency-divider module. Synchronization between the RF fields for acceleration and the mode-locked laser pulses for beam triggering are among the important points concerning the RF-gun. The frequency divider module which down-converts from 2856 MHz(RF) to 89.25 MHz(laser), and the electrical phase-shifter were specially developed for stable phase control. The phase jitter of the frequency divider should be less than 10 ps to satisfy our present requirements. The first experiments to trigger and accelerate beams with the above-mentioned system were carried out in January, 1992. (Author) 6 figs., 5 refs

Modulating Hole Transport in Multilayered Photocathodes with Derivatized p-Type Nickel Oxide and Molecular Assemblies for Solar-Driven Water Splitting

Energy Technology Data Exchange (ETDEWEB)

Shan, Bing [Department; Sherman, Benjamin D. [Department; Klug, Christina M. [Center; Nayak, Animesh [Department; Marquard, Seth L. [Department; Liu, Qing [Department; Bullock, R. Morris [Center; Meyer, Thomas J. [Department

2017-08-31

We report here a new photocathode composed of a bi-layered doped NiO film topped by a macro-mesoporous ITO (ioITO) layer with molecular assemblies attached to the ioITO surface. The NiO film containing a 2% K+ doped NiO inner layer and a 2% Cu2+ doped NiO outer layer provides sufficient driving force for hole transport after injection to NiO by the molecular assembly. The tri-layered oxide, NiK0.02O | NiCu0.02O | ioITO, sensitized by a ruthenium polypyridyl dye and functionalized with a nickel-based hydrogen evolution catalyst, outperforms its counterpart, NiO | NiO | ioITO, in photocatalytic hydrogen evolution from water over a period of several hours with a Faradaic yield of ~90%.

Development of a low-cost-high-sensitivity Compton camera using CsI (Tl) scintillators (γI)

Energy Technology Data Exchange (ETDEWEB)

Kagaya, M., E-mail: 13nd401n@vc.ibaraki.ac.jp [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito City, Ibaraki 310-8512 (Japan); Open-It consortium (Japan); Katagiri, H. [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito City, Ibaraki 310-8512 (Japan); Open-It consortium (Japan); Enomoto, R. [Institute for Cosmic Ray Research, University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 277-8582 (Japan); Open-It consortium (Japan); Hanafusa, R.; Hosokawa, M.; Itoh, Y. [Fuji Electric, 1 Fujimachi, Hino City, Tokyo 191-8502 (Japan); Muraishi, H. [School of Allied Health Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara City, Kanagawa 252-0373 (Japan); Open-It consortium (Japan); Nakayama, K. [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito City, Ibaraki 310-8512 (Japan); Open-It consortium (Japan); Satoh, K. [Shinsei Corporation, 4-9-1 Nihonbashi-honcho, Chuo-ku, Tokyo 103-0023 (Japan); Takeda, T. [School of Allied Health Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara City, Kanagawa 252-0373 (Japan); Tanaka, M.M.; Uchida, T. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba City, Ibaraki 305-0801 (Japan); Open-It consortium (Japan); Watanabe, T. [School of Allied Health Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara City, Kanagawa 252-0373 (Japan); Open-It consortium (Japan); Yanagita, S.; Yoshida, T.; Umehara, K. [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito City, Ibaraki 310-8512 (Japan); Open-It consortium (Japan)

2015-12-21

We have developed a novel low-cost gamma-ray imaging Compton camera γI that has a high detection efficiency. Our motivation for the development of this detector was to measure the arrival directions of gamma rays produced by radioactive nuclides that were released by the Fukushima Daiichi nuclear power plant accident in 2011. The detector comprises two arrays of inorganic scintillation detectors, which act as a scatterer and an absorber. Each array has eight scintillation detectors, each comprising a large CsI (Tl) scintillator cube of side 3.5 cm, which is inexpensive and has a good energy resolution. Energies deposited by the Compton scattered electrons and subsequent photoelectric absorption, measured by each scintillation counter, are used for image reconstruction. The angular resolution was found to be 3.5° after using an image-sharpening technique. With this angular resolution, we can resolve a 1 m{sup 2} radiation hot spot that is located at a distance of 10 m from the detector with a wide field of view of 1 sr. Moreover, the detection efficiency 0.68 cps/MBq at 1 m for 662 keV (7.6 cps/μSv/h) is sufficient for measuring low-level contamination (i.e., less than 1 μSv/h) corresponding to typical values in large areas of eastern Japan. In addition to the laboratory tests, the imaging capability of our detector was verified in various regions with dose rates less than 1 μSv/h (e.g., Fukushima city).

Contact Selectivity Engineering in a 2 μm Thick Ultrathin c-Si Solar Cell Using Transition-Metal Oxides Achieving an Efficiency of 10.8.

Science.gov (United States)

Xue, Muyu; Islam, Raisul; Meng, Andrew C; Lyu, Zheng; Lu, Ching-Ying; Tae, Christian; Braun, Michael R; Zang, Kai; McIntyre, Paul C; Kamins, Theodore I; Saraswat, Krishna C; Harris, James S

2017-12-06

In this paper, the integration of metal oxides as carrier-selective contacts for ultrathin crystalline silicon (c-Si) solar cells is demonstrated which results in an ∼13% relative improvement in efficiency. The improvement in efficiency originates from the suppression of the contact recombination current due to the band offset asymmetry of these oxides with Si. First, an ultrathin c-Si solar cell having a total thickness of 2 μm is shown to have >10% efficiency without any light-trapping scheme. This is achieved by the integration of nickel oxide (NiO x ) as a hole-selective contact interlayer material, which has a low valence band offset and high conduction band offset with Si. Second, we show a champion cell efficiency of 10.8% with the additional integration of titanium oxide (TiO x ), a well-known material for an electron-selective contact interlayer. Key parameters including V oc and J sc also show different degrees of enhancement if single (NiO x only) or double (both NiO x and TiO x ) carrier-selective contacts are integrated. The fabrication process for TiO x and NiO x layer integration is scalable and shows good compatibility with the device.

To Think and Watch the Evil: The Turn of the Screw as Cultural Reference in Television from Dark Shadows to C.S.I.

Directory of Open Access Journals (Sweden)

Anna Viola Sborgi

2012-07-01

Full Text Available Since its first publication, Henry James’s The Turn of the Screw (1898 has always haunted the imagination of artists (Benjamin Britten, Jack Clayton, Amenábar and has been widely used as a source for television narratives (Dan Curtis, US TV version starring Colin Firth, Tim Fywell. In serial productions, James’s story has been the object of extensive quotation and allusion, from the 1960 gothic soap opera Dark Shadows to the C.S.I. episode Turn of the Screw (Season 4, Episode 21. A milestone in literary history, the story now embodies a set of cultural references conveying different, complex meanings, which can only be disclosed in the light of contemporary forms of representing reality. The novella appeals to two apparently opposite tendencies in contemporary television: the morbid display of the real (C.S.I. and the quest for the supernatural (Buffy The Vampire Slayer, among others. A line can be traced from Dark Shadows, the show that pioneered the genre, to contemporary horror soaps about vampires and supernatural phenomena. This paper shows the ways in which James’ sophisticated novella makes its way through popular culture, and how its constant ambiguous, dilemmatic interplay between reality and imagination can be related to the double-sided drive of the contemporary public towards hyper-reality and the supernatural.

CSI: Dognapping workshop : an outreach experiment designed to produce students that are hooked on science.

Energy Technology Data Exchange (ETDEWEB)

Boyle, Timothy J.; Gorman, Anna K.; Pratt, Harry D., III; Hernandez-Sanchez, Bernadette A.; Lambert, Timothy N.; Ottley, Leigh Anna M.; Baros, Christina Marie

2008-04-01

The CSI: Dognapping Workshop is a culmination of the more than 65 Sandian staff and intern volunteers dedication to exciting and encouraging the next generation of scientific leaders. This 2 hour workshop used a 'theatrical play' and 'hands on' activities that was fun, exciting and challenging for 3rd-5th graders while meeting science curriculum standards. In addition, new pedagogical methods were developed in order to introduce nanotechnology to the public. Survey analysis indicated that the workshop had an overall improvement and positive impact on helping the students to understand concepts from materials science and chemistry as well as increased our interaction with the K-5 community. Anecdotal analyses showed that this simple exercise will have far reaching impact with the results necessary to maintain the United States as the scientific leader in the world. This experience led to the initiation of over 100 Official Junior Scientists.

Surface chemical analysis and ab initio investigations of CsI coated C fiber cathodes for high power microwave sources

Science.gov (United States)

Vlahos, Vasilios; Morgan, Dane; LaCour, Matthew; Golby, Ken; Shiffler, Don; Booske, John H.

2010-02-01

CsI coated C fiber cathodes are promising electron emitters utilized in field emission applications. Ab initio calculations, in conjunction with experimental investigations on CsI-spray coated C fiber cathodes, were performed in order to better understand the origin of the low turn-on E-field obtained, as compared to uncoated C fibers. One possible mechanism for lowering the turn-on E-field is surface dipole layers reducing the work function. Ab initio modeling revealed that surface monolayers of Cs, CsI, Cs2O, and CsO are all capable of producing low work function C fiber cathodes (1 eV<Φ<1.5 eV), yielding a reduction in the turn-on E-field by as much as ten times, when compared to the bare fiber. Although a CsI-containing aqueous solution is spray deposited on the C fiber surface, energy dispersive x-ray spectroscopy and scanning auger microscopy measurements show coabsorption of Cs and I into the fiber interior and Cs and O on the fiber surface, with no surface I. It is therefore proposed that a cesium oxide (CsxOy) surface coating is responsible, at least in part, for the low turn E-field and superior emission characteristics of this type of fiber cathode. This CsxOy layer could be formed during preconditioning heating. CsxOy surface layers cannot only lower the fiber work function by the formation of surface dipoles (if they are thin enough) but may also enhance surface emission through their ability to emit secondary electrons due to a process of grazing electron impact. These multiple electron emission processes may explain the reported 10-100 fold reduction in the turn-on E-field of coated C fibers.

A Brief Technical History of the Large-Area Picosecond Photodetector (LAPPD) Collaboration

Energy Technology Data Exchange (ETDEWEB)

Adams, B.W.; et al.

2016-03-06

The Large Area Picosecond PhotoDetector (LAPPD) Collaboration was formed in 2009 to develop large-area photodetectors capable of time resolutions measured in pico-seconds, with accompanying sub-millimeter spatial resolution. During the next three and one-half years the Collaboration developed the LAPPD design of 20 x 20 cm modules with gains greater than $10^7$ and non-uniformity less than $15\\%$, time resolution less than 50 psec for single photons and spatial resolution of 700~microns in both lateral dimensions. We describe the R\\&D performed to develop large-area micro-channel plate glass substrates, resistive and secondary-emitting coatings, large-area bialkali photocathodes, and RF-capable hermetic packaging. In addition, the Collaboration developed the necessary electronics for large systems capable of precise timing, built up from a custom low-power 15-GigaSample/sec waveform sampling 6-channel integrated circuit and supported by a two-level modular data acquisition system based on Field-Programmable Gate Arrays for local control, data-sparcification, and triggering. We discuss the formation, organization, and technical successes and short-comings of the Collaboration. The Collaboration ended in December 2012 with a transition from R\\&D to commercialization.

Monte-Carlo simulations of secondary electron emission from CsI, induced by 1-10 keV X-rays and electrons

International Nuclear Information System (INIS)

Akkerman, A.; Gibrekhterman, A.; Breskin, A.; Chechik, R.

1992-05-01

A model for electron transport and emission in CsI is proposed. It is based on theoretically calculated microscopic cross-sections for electron interaction with the nuclear and the electronic components of the solid. A Monte Carlo program based on this model was developed to simulate secondary electron emission induced by X-rays and electrons in the energy range of 1 to 10 keV. The calculated secondary emission yields agree with existing experimental data. The model provides all necessary characteristics for the design of radiation detectors based on secondary electron emission. It can be expanded to higher incident energies and other alkali halides. (author)

A compact and modular x- and gamma-ray detector with a CsI scintillator and double-readout Silicon Drift Detectors

Science.gov (United States)

Campana, R.; Fuschino, F.; Labanti, C.; Marisaldi, M.; Amati, L.; Fiorini, M.; Uslenghi, M.; Baldazzi, G.; Bellutti, P.; Evangelista, Y.; Elmi, I.; Feroci, M.; Ficorella, F.; Frontera, F.; Picciotto, A.; Piemonte, C.; Rachevski, A.; Rashevskaya, I.; Rignanese, L. P.; Vacchi, A.; Zampa, G.; Zampa, N.; Zorzi, N.

2016-07-01

A future compact and modular X and gamma-ray spectrometer (XGS) has been designed and a series of proto- types have been developed and tested. The experiment envisages the use of CsI scintillator bars read out at both ends by single-cell 25 mm2 Silicon Drift Detectors. Digital algorithms are used to discriminate between events absorbed in the Silicon layer (lower energy X rays) and events absorbed in the scintillator crystal (higher energy X rays and -rays). The prototype characterization is shown and the modular design for future experiments with possible astrophysical applications (e.g. for the THESEUS mission proposed for the ESA M5 call) are discussed.

Time Dependent Quantum Efficiency and Dark Current Measurements in an RF Photocathode Injector with a High Quantum Efficiency Cathode

CERN Document Server

Fliller, Raymond P; Hartung, Walter

2005-01-01

A system was developed at INFN Milano for preparing cesium telluride photo-cathodes and transferring them into an RF gun under ultra-high vacuum. This system has been in use at the Fermilab NICADD Photo-Injector Laboratory (FNPL) since 1997. A similar load-lock system is used at the TeSLA Test Facility at DESY-Hamburg. Two 1.625-cell high duty cycle RF guns have been fabricated for the project. Studies of the photo-emission and field emission ("dark current") behavior of both RF guns have been carried out. Unexpected phenomena were observed in one of the RF guns. In situ changes in the cathode's quantum efficiency and dark current with time were seen during operation of the photo-injector. These changes were correlated with the magnetostatic field at the cathode.* In addition, multipacting is observed in the RF guns under certain conditions. Recent measurements indicate a correlation between multipacting, anomalous photo-emission behavior, and anomalous field emission behavior. Results will be presented.

Artificial intelligence systems for rainy areas detection and convective cells' delineation for the south shore of Mediterranean Sea during day and nighttime using MSG satellite images

Science.gov (United States)

Tebbi, Mohsene Abdelfettah; Haddad, Boualem

2016-09-01

The aim of this study is to investigate the potential of cloud classification by means of support vector machines using high resolution images from northern Algeria. The images were taken from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board of the Meteosat Second Generation (MSG) satellite. An automatic system was developed to operate during both day and nighttime by following two steps of data processing. The first aims to detect rainy areas in cloud systems, whereas the second delineates convective cells from stratiform ones. A set of 12 spectral parameters was selected to extract information about cloud properties, which are different from day to night. The training and validation steps of this study were performed by in-situ rainfall measurement data, collected during the rainy season of years 2011 and 2012 via automatic rain gauge stations distributed in northern Algeria. Artificial neural networks (ANNs) and support vector machine (SVM) were explored, by combining spectral parameters derived from MSG images. Better performances were obtained by the SVM classifier, in terms of Critical Success Index and Probability of Detection for rainy areas detection (CSI = 0.81, POD = 91%), and also for convective/stratiform delineation (CSI = 0.55, POD = 74%).

Development Status and Performance Comparisons of Environmental Barrier Coating Systems for SiCSiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming; Harder, Bryan

2016-01-01

Environmental barrier coatings (EBC) and SiCSiC ceramic matrix composites (CMCs) will play a crucial role in future aircraft turbine engine systems, because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. This paper presents current NASA EBC-CMC development emphases including: the coating composition and processing improvements, laser high heat flux-thermal gradient thermo-mechanical fatigue - environmental testing methodology development, and property evaluations for next generation EBC-CMC systems. EBCs processed with various deposition techniques including Plasma Spray, Electron Beam - Physical Vapor Deposition, and Plasma Spray Physical Vapor Deposition (PS-PVD) will be particularly discussed. The testing results and demonstrations of advanced EBCs-CMCs in complex simulated engine thermal gradient cyclic fatigue, oxidizing-steam and CMAS environments will help provide insights into the coating development strategies to meet long-term engine component durability goals.

Efficient solar-assisted O2 reduction by a cofacial iron porphyrin dimer integrated to a p-CuBi2O4 photocathode prepared by a simple novel method.

Science.gov (United States)

Zahran, Zaki N; Mohamed, Eman A; Naruta, Yoshinori; Haleem, Ashraf

2017-10-04

A cofacial iron porphyrin hetero-dimer, Fe2TPFPP-TMP showed high electro-catalytic activity, selectivity, and stability for the O2 reduction to H2O both in homogeneous non-aqueous and heterogeneous neutral aqueous solutions. Moreover, when it is integrated to FTO/p-CuBi2O4 (FTO = fluorine doped tin oxide) photocathode prepared by a simple novel method, a remarkable efficient solar-assisted O2 reduction is achieved in neutral potassium phosphate (KPi) or basic NaOH solutions saturated with O2. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Advances in gas avalanche photomultipliers

CERN Document Server

Breskin, Amos; Buzulutskov, A F; Chechik, R; Garty, E; Shefer, G; Singh, B K

2000-01-01

Gas avalanche detectors, combining solid photocathodes with fast electron multipliers, provide an attractive solution for photon localization over very large sensitive areas and under high illumination flux. They offer single-photon sensitivity and the possibility of operation under very intense magnetic fields. We discuss the principal factors governing the operation of gas avalanche photomultipliers. We summarize the recent progress made in alkali-halide and CVD-diamond UV-photocathodes, capable of operation under gas multiplication, and novel thin-film protected alkali-antimonide photocathodes, providing, for the first time, the possibility of operating gas photomultipliers in the visible range. Electron multipliers, adequate for these photon detectors, are proposed and some applications are briefly discussed.

Particle Identification with the Cherenkov imaging technique using MPGD based Photon Detectors for Physics at COMPASS Experiment at CERN

CERN Document Server

AUTHOR|(CDS)2070220; Martin, Anna

A novel technology for the detection of single photons has been developed and implemented in 2016 in the Ring Imaging Cherenkov (RICH) detector of the COMPASS Experiment at CERN SPS. Some basic knowledge in the field of particle identification and RICH counters, Micro Pattern Gaseous Detectors (MPGDs) in general and their development for photon detection applications are provided. The characteristics of the COMPASS setup are summarized and the COMPAS RICH-1 detector is described and shown to provide hadron identification in the momentum range between 3 and 55 GeV/c. The THGEM technology is discussed illustrating their characterization as gas multipliers and as reflective photocathodes: large gains and efficient photodetection collections are achieved when using optimized parameters and conditions (hole diameter = THGEM thickness = 0.4 mm; hole pitch = 0.8 mm and no rim; CH4-rich gas mixtures and electric field values > 1 kV/cm at the CsI surface). The intense R\\&D program leading to the choice of a hybrid...

Photosensitive Gaseous Detectors for Cryogenic Temperature Applications

CERN Document Server

Periale, L; Iacobaeus, C; Lund-Jensen, B; Picchi, P; Pietropaolo, F

2007-01-01

There are several proposals and projects today for building LXe Time Projection Chambers (TPCs) for dark matter search. An important element of these TPCs are the photomultipliers operating either inside LXe or in vapors above the liquid. We have recently demonstrated that photosensitive gaseous detectors (wire type and hole-type) can operate perfectly well until temperatures of LN2. In this paper results of systematic studies of operation of the photosensitive version of these detectors (combined with reflective or semi-transparent CsI photocathodes) in the temperature interval of 300-150 K are presented. In particular, it was demonstrated that both sealed and flushed by a gas detectors could operate at a quite stable fashion in a year/time scale. Obtained results, in particular the long-term stability of photosensitive gaseous detectors, strongly indicate that they can be cheap and simple alternatives to photomultipliers or avalanche solid-state detectors in LXe TPC applications.

Results of a first beam test of hadron blind trackers

Energy Technology Data Exchange (ETDEWEB)

Chen, M. (Laboratory for Nuclear Science, MIT, Cambridge, MA (United States)); Luckey, D. (Laboratory for Nuclear Science, MIT, Cambridge, MA (United States)); Smolin, M. (Laboratory for Nuclear Science, MIT, Cambridge, MA (United States)); Sumorok, K. (Laboratory for Nuclear Science, MIT, Cambridge, MA (United States)); Zhang, X. (Laboratory for Nuclear Science, MIT, Cambridge, MA (United States)); Bolozdynya, A. (ITEP, Moscow (Russian Federation)); Belogurov, S. (ITEP, Moscow (Russian Federation)); Churakov, D. (ITEP, Moscow (Russian Federation)); Koutchenkov, A. (ITEP, Moscow (Russian Federation)); Kovalenko, A. (ITEP, Moscow (Russian Federation)); Kuzichev, V. (ITEP, Moscow (Russian Federation)); Lebedenko, V. (ITEP, Moscow (Russian Federation)); Sheinkman, V. (ITEP, Moscow (Russian Federation)); Smirnov, G. (ITEP, Moscow (Russian Federation)); Safronov, G. (ITEP, Moscow (Russian Federation)); Vinogradov, V. (ITEP, Moscow (Russian Federation)); Giomataris, Y. (IPN,

1994-07-15

We describe the experimental results of a new type of electron tracker, called Hadron Blind Detector or HBD. An HBD prototype was tested with gas mixtures of CF[sub 4] with He or Ne and a parallel plate avalanche chamber having a CsI photocathode of eight pads. Beam tests confirm the large Cherenkov light bandwidth in the EUV region that can be obtained with such gas mixtures. It results in a large quality factor of about 500 cm[sup -1] which allows HBD operation with a much shorter radiator thickness than conventional Cherenkov counters. Full electron efficiency was obtained, while pions were rejected up to momenta of 9 GeV/c. HBD is unique in measuring electron trajectories near the vertex, vetoing Dalitz pairs, and providing trigger on electrons among heavy hadron background. We discuss the use of such detectors for lepton identification and detection in high energy physics experiments and especially in heavy ion colliders. ((orig.))

Results of a first beam test of hadron blind trackers

International Nuclear Information System (INIS)

Chen, M.; Luckey, D.; Smolin, M.; Sumorok, K.; Zhang, X.; Bolozdynya, A.; Belogurov, S.; Churakov, D.; Koutchenkov, A.; Kovalenko, A.; Kuzichev, V.; Lebedenko, V.; Sheinkman, V.; Smirnov, G.; Safronov, G.; Vinogradov, V.; Giomataris, Y.; Joseph, C.; Werlen, M.; Charpak, G.; Blumenfeld, B.; Gougas, A.K.; Steele, D.; Akopyan, M.

1994-01-01

We describe the experimental results of a new type of electron tracker, called Hadron Blind Detector or HBD. An HBD prototype was tested with gas mixtures of CF 4 with He or Ne and a parallel plate avalanche chamber having a CsI photocathode of eight pads. Beam tests confirm the large Cherenkov light bandwidth in the EUV region that can be obtained with such gas mixtures. It results in a large quality factor of about 500 cm -1 which allows HBD operation with a much shorter radiator thickness than conventional Cherenkov counters. Full electron efficiency was obtained, while pions were rejected up to momenta of 9 GeV/c. HBD is unique in measuring electron trajectories near the vertex, vetoing Dalitz pairs, and providing trigger on electrons among heavy hadron background. We discuss the use of such detectors for lepton identification and detection in high energy physics experiments and especially in heavy ion colliders. ((orig.))

The ALICE-HMPID Detector Control System: Its evolution towards an expert and adaptive system

Science.gov (United States)

De Cataldo, G.; Franco, A.; Pastore, C.; Sgura, I.; Volpe, G.

2011-05-01

The High Momentum Particle IDentification (HMPID) detector is a proximity focusing Ring Imaging Cherenkov (RICH) for charged hadron identification. The HMPID is based on liquid C 6F 14 as the radiator medium and on a 10 m 2 CsI coated, pad segmented photocathode of MWPCs for UV Cherenkov photon detection. To ensure full remote control, the HMPID is equipped with a detector control system (DCS) responding to industrial standards for robustness and reliability. It has been implemented using PVSS as Slow Control And Data Acquisition (SCADA) environment, Programmable Logic Controller as control devices and Finite State Machines for modular and automatic command execution. In the perspective of reducing human presence at the experiment site, this paper focuses on DCS evolution towards an expert and adaptive control system, providing, respectively, automatic error recovery and stable detector performance. HAL9000, the first prototype of the HMPID expert system, is then presented. Finally an analysis of the possible application of the adaptive features is provided.

The ALICE-HMPID Detector Control System: Its evolution towards an expert and adaptive system

International Nuclear Information System (INIS)

De Cataldo, G.; Franco, A.; Pastore, C.; Sgura, I.; Volpe, G.

2011-01-01

The High Momentum Particle IDentification (HMPID) detector is a proximity focusing Ring Imaging Cherenkov (RICH) for charged hadron identification. The HMPID is based on liquid C 6 F 14 as the radiator medium and on a 10 m 2 CsI coated, pad segmented photocathode of MWPCs for UV Cherenkov photon detection. To ensure full remote control, the HMPID is equipped with a detector control system (DCS) responding to industrial standards for robustness and reliability. It has been implemented using PVSS as Slow Control And Data Acquisition (SCADA) environment, Programmable Logic Controller as control devices and Finite State Machines for modular and automatic command execution. In the perspective of reducing human presence at the experiment site, this paper focuses on DCS evolution towards an expert and adaptive control system, providing, respectively, automatic error recovery and stable detector performance. HAL9000, the first prototype of the HMPID expert system, is then presented. Finally an analysis of the possible application of the adaptive features is provided.

Aluminum-coated optical fibers as efficient infrared timing fiducial photocathodes for synchronizing x-ray streak cameras

International Nuclear Information System (INIS)

Koch, J.A.; MacGowan, B.J.

1991-01-01

The timing fiducial system at the Nova Two-Beam Facility allows time-resolved x-ray and optical streak camera data from laser-produced plasmas to be synchronized to within 30 ps. In this system, an Al-coated optical fiber is inserted into an aperture in the cathode plate of each streak camera. The coating acts as a photocathode for a low-energy pulse of 1ω (λ = 1.054 μm) light which is synchronized to the main Nova beam. The use of the fundamental (1ω) for this fiducial pulse has been found to offer significant advantages over the use of the 2ω second harmonic (λ = 0.53 μm). These advantages include brighter signals, greater reliability, and a higher relative damage threshold, allowing routine use without fiber replacement. The operation of the system is described, and experimental data and interpretations are discussed which suggest that the electron production in the Al film is due to thermionic emission. The results of detailed numerical simulations of the relevant thermal processes, undertaken to model the response of the coated fiber to 1ω laser pulses, are also presented, which give qualitative agreement with experimental data. Quantitative discrepancies between the modeling results and the experimental data are discussed, and suggestions for further research are given

Electro-optical design of a long slit streak tube

Science.gov (United States)

Tian, Liping; Tian, Jinshou; Wen, Wenlong; Chen, Ping; Wang, Xing; Hui, Dandan; Wang, Junfeng

2017-11-01

A small size and long slit streak tube with high spatial resolution was designed and optimized. Curved photocathode and screen were adopted to increase the photocathode working area and spatial resolution. High physical temporal resolution obtained by using a slit accelerating electrode. Deflection sensitivity of the streak tube was improved by adopting two-folded deflection plates. The simulations indicate that the photocathode effective working area can reach 30mm × 5mm. The static spatial resolution is higher than 40lp/mm and 12lp/mm along scanning and slit directions respectively while the physical temporal resolution is higher than 60ps. The magnification is 0.75 and 0.77 in scanning and slit directions. And also, the deflection sensitivity is as high as 37mm/kV. The external dimension of the streak tube are only ∅74mm×231mm. Thus, it can be applied to laser imaging radar system for large field of view and high range precision detection.

Development of gaseous photomultiplier

International Nuclear Information System (INIS)

Tokanai, F.; Sumiyoshi, T.; Sugiyama, H.; Okada, T.

2014-01-01

We have been developing gaseous photomultiplier tubes (PMTs) with alkali photocathode combined with micropattern gas detectors (MPGDs). The potential advantage of the gaseous PMT is that it can achieve a very large effective area with adequate position and timing resolutions. In addition, it will be easily operated under a very high magnetic field, compared with the conventional vacuum-based PMT. To evaluate the gaseous PMTs filled with Ne and Ar based gas mixture, we have developed gaseous PMTs with an alkali photocathode combined with MPGDs such as a glass capillary plate, GEM, and Micromegas detector. We describe the recent development of the gaseous PMTs, particularly the production of the photocathode, gas gain, ion and photon feedbacks, quantum efficiency, and the characteristics in the magnetic field environment. (author)

Enhancement of solar hydrogen evolution from water by surface modification with CdS and TiO2 on porous CuInS2 photocathodes prepared by an electrodeposition-sulfurization method.

Science.gov (United States)

Zhao, Jiao; Minegishi, Tsutomu; Zhang, Li; Zhong, Miao; Gunawan; Nakabayashi, Mamiko; Ma, Guijun; Hisatomi, Takashi; Katayama, Masao; Ikeda, Shigeru; Shibata, Naoya; Yamada, Taro; Domen, Kazunari

2014-10-27

Porous films of p-type CuInS2, prepared by sulfurization of electrodeposited metals, are surface-modified with thin layers of CdS and TiO2. This specific porous electrode evolved H2 from photoelectrochemical water reduction under simulated sunlight. Modification with thin n-type CdS and TiO2 layers significantly increased the cathodic photocurrent and onset potential through the formation of a p-n junction on the surface. The modified photocathodes showed a relatively high efficiency and stable H2 production under the present reaction conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fast and accurate methods for the performance testing of highly-efficient c-Si photovoltaic modules using a 10 ms single-pulse solar simulator and customized voltage profiles

International Nuclear Information System (INIS)

Virtuani, A; Rigamonti, G; Friesen, G; Chianese, D; Beljean, P

2012-01-01

Performance testing of highly efficient, highly capacitive c-Si modules with pulsed solar simulators requires particular care. These devices in fact usually require a steady-state solar simulator or pulse durations longer than 100–200 ms in order to avoid measurement artifacts. The aim of this work was to validate an alternative method for the testing of highly capacitive c-Si modules using a 10 ms single pulse solar simulator. Our approach attempts to reconstruct a quasi-steady-state I–V (current–voltage) curve of a highly capacitive device during one single 10 ms flash by applying customized voltage profiles–-in place of a conventional V ramp—to the terminals of the device under test. The most promising results were obtained by using V profiles which we name ‘dragon-back’ (DB) profiles. When compared to the reference I–V measurement (obtained by using a multi-flash approach with approximately 20 flashes), the DB V profile method provides excellent results with differences in the estimation of P max (as well as of I sc , V oc and FF) below ±0.5%. For the testing of highly capacitive devices the method is accurate, fast (two flashes—possibly one—required), cost-effective and has proven its validity with several technologies making it particularly interesting for in-line testing. (paper)

The Development of Environmental Barrier Coatings for SiCSiC Ceramic Matrix Composites: Challenges and Opportunities

Science.gov (United States)

Zhu, Dongming

2014-01-01

Environmental barrier coatings (EBCs) and SiC/SiC ceramic matrix composites (CMCs) systems will play a crucial role in future turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is a key to enable the applications of the envisioned CMC components to help achieve next generation engine performance and durability goals. This paper will primarily address the performance requirements and design considerations of environmental barrier coatings for turbine engine applications. The emphasis is placed on current candidate environmental barrier coating systems for SiCSiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. Major technical barriers in developing advanced environmental barrier coating systems, the coating integrations with next generation CMC turbine components having improved environmental stability, cyclic durability and system performance will be described. The development trends for turbine environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling will be discussed.

Impact of radiation technique upon the outcome of treatment for medulloblastoma

International Nuclear Information System (INIS)

Halperin, Edward C.

1996-01-01

Craniospinal irradiation (CSI) is an essential component of the therapy of medulloblastoma. Because medulloblastoma disseminates via the cerebrospinal fluid (CSF), CSI technique involves the irradiation of all CSF-bearing areas which are at risk for tumor seeding. Underdosing with radiation because of inadequacies in CSI technique will produce dose 'cold spots' which have the potential of serving as a nidus for tumor recurrence. A simple mathematic model of subclinical disease in medulloblastoma based on the available data concerning the radiosensitivity of medulloblastoma cell lines as well as the known clinical dose-response relationships support the hypothesis that for most cases of medulloblastoma, the radiotherapist is working in a range of doses arrayed on the steep portion of the tumor control probability curve. Underdosing of CSF-bearing areas because of technical problems at the junction of the cranial and spinal fields of irradiation, placement of shielding blocks in the cribiform plate-sub frontal region, and/or anatomic errors in the design of the caudal end of the CSI fields may lead to significant risks of tumor relapse. One may debate the necessity of a posterior fossa boost encompassing the entire anatomic posterior fossa rather than the primary tumor volume with a margin. This review critically evaluates the potential impact of CSI technique upon the outcome of treatment for medulloblastoma, and suggests future areas of inquiry

Delay analysis of a point-to-multipoint spectrum sharing network with CSI based power allocation

KAUST Repository

Khan, Fahd Ahmed

2012-10-01

In this paper, we analyse the delay performance of a point-to-multipoint cognitive radio network which is sharing the spectrum with a point-to-multipoint primary network. The channel is assumed to be independent but not identically distributed and has Nakagami-m fading. A constraint on the peak transmit power of the secondary user transmitter (SU-Tx) is also considered in addition to the peak interference power constraint. Based on the constraints, a power allocation scheme which requires knowledge of the instantaneous channel state information (CSI) of the interference links is derived. The SU-Tx is assumed to be equipped with a buffer and is modelled using the M/G/1 queueing model. Closed form expressions for the probability distribution function (PDF) and cumulative distribution function (CDF) of the packet transmission time is derived. Using the PDF, the expressions for the moments of transmission time are obtained. In addition, using the moments, the expressions for the performance measures such as the total average waiting time of packets and the average number of packets waiting in the buffer of the SU-Tx are also obtained. Numerical simulations corroborate the theoretical results. © 2012 IEEE.

A separate effect study of the influence of metallic fission products on CsI radioactive release from nuclear fuel

Energy Technology Data Exchange (ETDEWEB)

Di Lemma, F.G., E-mail: fidelma.dilemma@gmail.com [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Delft, 2629 JB (Netherlands); Colle, J.Y., E-mail: jean-yves.colle@ec.europa.eu [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Beneš, O. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Konings, R.J.M. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Delft, 2629 JB (Netherlands)

2015-10-15

The chemistry of cesium and iodine is of main importance to quantify the radioactive release in case of a nuclear reactor accident, or sabotage involving irradiated nuclear materials. We studied the interaction of CsI with different metallic fission products such as Mo and Ru. These elements can be released from nuclear fuel when exposed to oxidising conditions, as in the case of contact of overheated nuclear fuel with air (e.g. in a spent fuel cask sabotage, uncovering of a spent fuel pond, or air ingress accidents). Experiments were performed by vaporizing mixtures of the compounds in air, and analysing the produced aerosols in view of a possible gas–gas and gas–aerosol reactions between the compounds. These results were compared with the gaseous species predicted by thermochemical equilibrium calculations and experimental equilibrium vaporization tests using Knudsen Effusion Mass Spectrometry.

Effect of hydrogen on passivation quality of SiNx/Si-rich SiNx stacked layers deposited by catalytic chemical vapor deposition on c-Si wafers

International Nuclear Information System (INIS)

Thi, Trinh Cham; Koyama, Koichi; Ohdaira, Keisuke; Matsumura, Hideki

2015-01-01

We investigate the role of hydrogen content and fixed charges of catalytic chemical vapor deposited (Cat-CVD) SiN x /Si-rich SiN x stacked layers on the quality of crystalline silicon (c-Si) surface passivation. Calculated density of fixed charges is on the order of 10 12 cm −2 , which is high enough for effective field effect passivation. Hydrogen content in the films is also found to contribute significantly to improvement in passivation quality of the stacked layers. Furthermore, Si-rich SiN x films deposited with H 2 dilution show better passivation quality of SiN x /Si-rich SiN x stacked layers than those prepared without H 2 dilution. Effective minority carrier lifetime (τ eff ) in c-Si passivated by SiN x /Si-rich SiN x stacked layers is as high as 5.1 ms when H 2 is added during Si-rich SiN x deposition, which is much higher than the case of using Si-rich SiN x films prepared without H 2 dilution showing τ eff of 3.3 ms. - Highlights: • Passivation mechanism of Si-rich SiN x /SiN x stacked layers is investigated. • H atoms play important role in passivation quality of the stacked layer. • Addition of H 2 gas during Si-rich SiN x film deposition greatly enhances effective minority carrier lifetime (τ eff ). • For a Si-rich SiN x film with refractive index of 2.92, τ eff improves from 3.3 to 5.1 ms by H 2 addition

From 1 Sun to 10 Suns c-Si Cells by Optimizing Metal Grid, Metal Resistance, and Junction Depth

International Nuclear Information System (INIS)

Chaudhari, V.A.; Solanki, C.S.

2009-01-01

Use of a solar cell in concentrator PV technology requires reduction in its series resistance in order to minimize the resistive power losses. The present paper discusses a methodology of reducing the series resistance of a commercial c-Si solar cell for concentrator applications, in the range of 2 to 10 suns. Step by step optimization of commercial cell in terms of grid geometry, junction depth, and electroplating of the front metal contacts is proposed. A model of resistance network of solar cell is developed and used for the optimization. Efficiency of un optimized commercial cell at 10 suns drops by 30% of its 1 sun value corresponding to resistive power loss of about 42%. The optimized cell with grid optimization, junction optimization, electroplating, and junction optimized with electroplated contacts cell gives resistive power loss of 20%, 16%, 11%, and 8%, respectively. An efficiency gain of 3% at 10 suns for fully optimized cell is estimated

Lifetime measurements using the Jefferson Lad Load-Lock Electron Gun

International Nuclear Information System (INIS)

J. Grames; P. Adderley; M. Baylac; J. Brittian; D. Charles; J. Clark; J. Hansknecht; M. Poelker; M. Stutzman; K. Surles-Law

2000-01-01

Lifetime measurements of bulk GaAs using a 100 kV load-lock electron gun and beam line were made. Initial tests used anodized samples to study lifetime under various conditions (gun vacuum, laser spot location, activated area). Subsequent tests used a mechanical mask to limit the active area and included improved monitoring of the gun chamber and beam line vacuum pressure. Results of these measurements support claims made at past workshops, namely photocathode lifetime improves when gun vacuum is enhanced and when electron emission from the edge of the photocathode is eliminated. The dependence upon laser spot location is less certain. Tests studying lifetime at higher beam intensity (I ∼ 8 mA) have begun

Deuterium trapping in the carbon-silicon co-deposition layers prepared by RF sputtering in D2 atmosphere

Science.gov (United States)

Zhang, Hongliang; Zhang, Weiyuan; Su, Ranran; Tu, Hanjun; Shi, Liqun; Hu, Jiansheng

2018-04-01

Deuterated carbon-silicon layers co-deposited on graphite and silicon substrates by radio frequency magnetron sputtering in pure D2 plasma were produced to study deuterium trapping and characteristics of the C-Si layers. The C-Si co-deposited layers were examined by ion beam analysis (IBA), Raman spectroscopy (RS), infrared absorption (IR) spectroscopy, thermal desorption spectroscopy (TDS) and scanning electron microscopy (SEM). It was found that the growth rate of the C-Si co-deposition layer decreased with increasing temperature from 350 K to 800 K, the D concentration and C/Si ratios increased differently on graphite and silicon substrates. TDS shows that D desorption is mainly as D2, HD, HDO, CD4, and C2D4 and release peaks occurred at temperatures of less than 900 K. RS and IR analysis reveal that the structure of the C-Si layers became more disordered with increasing temperatures. Rounded areas of peeling with 1-2 μm diameters were observed on the surface.

The experience of building and operating COMPASS RICH-1

CERN Document Server

Birsa, R; Rocco, E; Schiavon, P; Kramer, D; Schroder, W; Dafni, T; Tessarotto, F; Bressan, A; Schill, C; Deschamps, H; Mann, A; Sozzi, F; Colantoni, M; Dibiase, N; Abbon, P; Svec, M; Delagnes, E; Ketzer, B; Joosten, R; Steiger, L; Ciliberti, P; Konigsmann, K; Maggiora, A; Kolosov, V N; Giorgi, M; Sbrizzai, G; Nahle, O; Kunne, F; Sulc, M; Teufel, A; Paul, S; Neyret, D; Rebourgeard, P; Menon, G; Dalla Torre, S; Hagemann, R; Slunecka, M; Martin, A; Magnon, A; Takekawa, S; Finger, M; Bradamante, F; Heinsius, F H; Nerling, F; Gerassimov, S; Polak, J; Alexeev, M; Pizzolotto, C; Chiosso, M; Gobbo, B; Angerer, H; Denisov, O; Ferrero, A; Baum, G; Franco, C; Lehmann, A; Bordalo, P; Duic, V; Konorov, I; Mutter, A; Levorato, S; Robinet, F; von Harrach, D; Fischer, H; Schoenmeier, P; Pesaro, G; Wollny, H; Panzieri, D

2011-01-01

COMPASS RICH-1 is a large size gaseous Imaging Cherenkov Detector providing hadron identification in the range from 3 to 55 GeV/c, in the wide acceptance spectrometer of the COMPASS Experiment at CERN SPS. It uses a 3 m long C(4)F(10) radiator, a 21 m(2) large VUV mirror surface and two kinds of photon detectors: MAPMTs and MWPCs with CsI photocathodes, covering a total of 5.5 m(2). It is in operation since 2002 and its performance has increased in time thanks to progressive optimization and mostly to a major upgrade which was implemented in 2006. The main characteristics of COMPASS RICH-1 components are described and some specific aspects related to the radiator gas system, the mirror alignment, the MWPC electrical stability and the readout electronics are discussed. Some key features of the event reconstruction and the PID analysis are presented together with results from the COMPASS RICH-1 performance characterization study. (C) 2010 Elsevier B.V. All rights reserved.

Optimization of the electron collection efficiency of a large area MCP-PMT for the JUNO experiment

International Nuclear Information System (INIS)

Chen, Lin; Tian, Jinshou; Liu, Chunliang; Wang, Yifang; Zhao, Tianchi; Liu, Hulin; Wei, Yonglin; Sai, Xiaofeng; Chen, Ping; Wang, Xing; Lu, Yu; Hui, Dandan; Guo, Lehui; Liu, Shulin; Qian, Sen; Xia, Jingkai; Yan, Baojun; Zhu, Na; Sun, Jianning; Si, Shuguang

2016-01-01

A novel large-area (20-inch) photomultiplier tube based on microchannel plate (MCP-PMTs) is proposed for the Jiangmen Underground Neutrino Observatory (JUNO) experiment. Its photoelectron collection efficiency C e is limited by the MCP open area fraction (A open ). This efficiency is studied as a function of the angular (θ), energy (E) distributions of electrons in the input charge cloud and the potential difference (U) between the PMT photocathode and the MCP input surface, considering secondary electron emission from the MCP input electrode. In CST Studio Suite, Finite Integral Technique and Monte Carlo method are combined to investigate the dependence of C e on θ, E and U. Results predict that C e can exceed A open , and are applied to optimize the structure and operational parameters of the 20-inch MCP-PMT prototype. C e of the optimized MCP-PMT is expected to reach 81.2%. Finally, the reduction of the penetration depth of the MCP input electrode layer and the deposition of a high secondary electron yield material on the MCP are proposed to further optimize C e .

Femtosecond pulse radiolysis based on photocathode electron accelerator

International Nuclear Information System (INIS)

Yoshida, Y.; Yang, Jinfeng; Kondoh, T.; Kozawa, T.; Tagawa, S.

2006-01-01

Pulse radiolysis is a powerful tool for studying chemical kinetics and primary processes or reactions of radiation chemistry. In the pulse radiolysis, a short electron beam, which is almost produced by radio-frequency (RF) electron linear accelerator with energy from a few MeV to a few tens MeV, is used as an irradiative source. The electron-induced reactions or phenomena in matter are analyzed by a short-pulse analyzing light (e.g. synchronized lasers) with the time-resolved stroboscopic technique. The time resolution of pulse radiolysis is not only dependent on the electron bunch length, the analyzing light pulse width, the time jitter between the electron bunch and the analyzing light, but also determined by degradation due to the velocity difference between light and the electron in the sample because of the refractive index. In order to improve the time resolution into femtosecond time region, we have develop a new pulse radiolysis based on a concept of 'Equivalent Velocity Spectroscopy (EVS)' to avoid the degradation of the time resolution caused by the velocity difference between the light and the electron beam in sample. In EVS as shown in Fig.1, a femtosecond electron beam produced by a photocathode electron linear accelerator was used, and a synchronized femtosecond laser was used as the analyzing light source. The electron beam and the laser light were injected into sample with an angle (θ), which is determined by the refractive index (n) of the sample. The electron bunch was also rotated with a same angle to make an overlap of the electron bunch with the laser pulse. The degradation of the time resolution caused by the velocity difference between the light and the electron beam can be calculated as g(L)=L[n/c-1/(vcos θ)], where L is the optical path length and v is the velocity of the electron in sample (we can assume v=c for a few tens MeV electron beam).We can thus obtained g(L)=0 by adjusting the incident angle to cos θ=1/n. However, the rotation

A Comprehensive evaluation of groundwater vulnerability to saltwater up-coning and sea water intrusion in a coastal aquifer (case study: Ghaemshahr-juybar aquifer)

Science.gov (United States)

Motevalli, Alireza; Moradi, Hamid Reza; Javadi, Saman

2018-02-01

Aquifer salinization has recently increased significantly due to human activity and has caused irreparable environmental and economic effects. In this research, a new method is proposed for modeling the vulnerability to salinity for the Ghaemshahr-juybar aquifer. Specifically, the GALDIT (Sea water intrusion) and TAWLBIC (Saltwater up-coning) indices were combined to produce a map of vulnerability (Comprehensive Salinity Index or CSI) to seawater intrusion of a region near the coast and saltwater up-coning away from the coast, respectively. Single parameter and removal layer sensitivity analysis were performed in order to identify the sensitive parameters and achieve optimal weights (through the single-parameter method) of contributing factors in all three methods. The three optimized methods produced were GALDIT-Opt, TAWLBIC-Opt and CSI-Opt. To assess the accuracy of the original maps and optimal ones, the Pearson correlation was used. Results indicated that the Pearson correlation of the optimized GALDIT, TAWLBIC and CSI model was better than GALDIT, TAWLBIC and CSI. The results show that the increase in correlation between EC (Electrical Conductivity), TDS (Total Dissolved Solids) and SAR (Sodium Adsorption Ratio) from the GALDIT model to the CSI-Opt model from values of 0.64, 0.56 and 0.68 has improved to values of 0.81, 0.88 and 0.91, respectively. The highest concentration of EC, with a value of 7050 μs/cm, is sampled in the areas of the east and northwest of the Ghaemshahr-juybar aquifer, which are classified in the CSI-Opt model as high and very high vulnerability levels. The highest concentration of TDS and SAR has been found in the east, northwest and northeast of the Ghaemshahr-juybar aquifer with a value of 4724 ppm for TDS and 14 mg/l for SAR that have been modeled in the CSI-Opt index as highly vulnerable areas. Eventually, CSI mapping can be used as an efficient tool in prioritizing in terms of the vulnerability to aquifer salinity, carrying out

Growing GaN LEDs on amorphous SiC buffer with variable C/Si compositions

Science.gov (United States)

Cheng, Chih-Hsien; Tzou, An-Jye; Chang, Jung-Hung; Chi, Yu-Chieh; Lin, Yung-Hsiang; Shih, Min-Hsiung; Lee, Chao-Kuei; Wu, Chih-I; Kuo, Hao-Chung; Chang, Chun-Yen; Lin, Gong-Ru

2016-01-01

The epitaxy of high-power gallium nitride (GaN) light-emitting diode (LED) on amorphous silicon carbide (a-SixC1−x) buffer is demonstrated. The a-SixC1−x buffers with different nonstoichiometric C/Si composition ratios are synthesized on SiO2/Si substrate by using a low-temperature plasma enhanced chemical vapor deposition. The GaN LEDs on different SixC1−x buffers exhibit different EL and C-V characteristics because of the extended strain induced interfacial defects. The EL power decays when increasing the Si content of SixC1−x buffer. The C-rich SixC1−x favors the GaN epitaxy and enables the strain relaxation to suppress the probability of Auger recombination. When the SixC1−x buffer changes from Si-rich to C-rich condition, the EL peak wavelengh shifts from 446 nm to 450 nm. Moreover, the uniform distribution contour of EL intensity spreads between the anode and the cathode because the traping density of the interfacial defect gradually reduces. In comparison with the GaN LED grown on Si-rich SixC1−x buffer, the device deposited on C-rich SixC1−x buffer shows a lower turn-on voltage, a higher output power, an external quantum efficiency, and an efficiency droop of 2.48 V, 106 mW, 42.3%, and 7%, respectively. PMID:26794268

I Evolution of Environmental Costs Discolsur: A Study in Cellulose and Paper Companies - Members of Corporate Sustainability Index - CSI

Directory of Open Access Journals (Sweden)

Daniel Fonseca

2016-07-01

Full Text Available This research aimed to analyse, in relation to previous studies, the evolution of classification and disclosure of environmental costs on cellulose and paper companies listed on the CSI. The research, of a descriptive, documentary and qualitative nature, was based on content analysis of financial statements, accompanying notes, management reports and sustainability reports in the fiscal years 2010 to 2014. The results indicate that companies show environmental costs mainly in a qualitative way and of the positive type. The most part of this information is contained in the sustainability report. As to the classification, the highlighted environmental costs are of these types, (a prevention costs; (b internal failure costs; (c indirect costs; (d internal costs; (e costs for contingencies; (f potentially hidden costs; (g image and relationship costs, though not by these names. These results demonstrate a change, compared to previous studies on the quality and quantity of disclosure of environmental costs. It is suggested for future research the broadening of samples for other organizational activity sectors, with the aim of possible understanding of the Brazilian environment.

De una sociología de la mediación a una pragmática de las vinculaciones. Retrospectiva de un recorrido sociológico dentro del CSI

Directory of Open Access Journals (Sweden)

Antoine Hennion

2017-08-01

Full Text Available Este artículo enfoca sobre un retorno reflexivo en mi propia trayectoria en el CSI. Mi propósito no es fijar la historia sino releerla desde las preocupaciones presentes. Desde su fundación por L. Karpik en 1967, el CSI abogó por tomar seriamente las realidades que estaba investigando (derecho, ciencia y tecnología, negocios, cultura. Bajo el título de un posible “retorno al objeto” en sociología, discuto convergencias y diferencias en el trabajo de campo emprendido, por un lado, sobre la ciencia y tecnología (STS, y por el otro sobre la cultura: por ejemplo, el uso de términos como traducción o mediación, o la relación diferente con la sociología crítica de Bourdieu, que no tuvo el mismo impacto en cada campo. Luego considero la emergencia de los enfoques pragmatistas en Francia en los años noventa y la gran variedad de concepciones a las que dieron lugar, en particular a través de debates con grupos cercanos como el GSPM y el CEMS en la EHESS de Paris, sobre el estatuto de los objetos, y examinando la influencia de las teorías de la acción provenientes de Estados Unidos. Apoyándome en esta genealogía, muestro cómo las aseveraciones del pragmatismo han informado mi propio trabajo con los aficionados y las vinculaciones, y discute en definitiva la importancia para la sociología de volverse más sensible respecto a los objetos de los que se ocupa.

Optimization of the electron collection efficiency of a large area MCP-PMT for the JUNO experiment

Energy Technology Data Exchange (ETDEWEB)

Chen, Lin, E-mail: chenlin@opt.cn [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an 710119 (China); Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Xi’an Jiaotong University, Xi’an 710049 (China); Tian, Jinshou [Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Liu, Chunliang [Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Yifang; Zhao, Tianchi [Institute of High Energy Physics (IHEP) of CAS, Beijing 100049 (China); Liu, Hulin; Wei, Yonglin; Sai, Xiaofeng [Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Chen, Ping [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an 710119 (China); Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Wang, Xing; Lu, Yu [Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Hui, Dandan; Guo, Lehui [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an 710119 (China); Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Liu, Shulin; Qian, Sen; Xia, Jingkai; Yan, Baojun; Zhu, Na [Institute of High Energy Physics (IHEP) of CAS, Beijing 100049 (China); Sun, Jianning; Si, Shuguang [North Night Vision Technology (NNVT) CO., LTD, Nanjing 210110 (China); and others

2016-08-11

A novel large-area (20-inch) photomultiplier tube based on microchannel plate (MCP-PMTs) is proposed for the Jiangmen Underground Neutrino Observatory (JUNO) experiment. Its photoelectron collection efficiency C{sub e} is limited by the MCP open area fraction (A{sub open}). This efficiency is studied as a function of the angular (θ), energy (E) distributions of electrons in the input charge cloud and the potential difference (U) between the PMT photocathode and the MCP input surface, considering secondary electron emission from the MCP input electrode. In CST Studio Suite, Finite Integral Technique and Monte Carlo method are combined to investigate the dependence of C{sub e} on θ, E and U. Results predict that C{sub e} can exceed A{sub open}, and are applied to optimize the structure and operational parameters of the 20-inch MCP-PMT prototype. C{sub e} of the optimized MCP-PMT is expected to reach 81.2%. Finally, the reduction of the penetration depth of the MCP input electrode layer and the deposition of a high secondary electron yield material on the MCP are proposed to further optimize C{sub e}.

Gamma Ray Large Area Space Telescope (GLAST) Balloon Flight Engineering Model: Overview

Science.gov (United States)

Thompson, D. J.; Godfrey, G.; Williams, S. M.; Grove, J. E.; Mizuno, T.; Sadrozinski, H. F.-W.; Kamae, T.; Ampe, J.; Briber, Stuart; Dann, James;

First observation of Cherenkov rings with a large area CsI-TGEM-based RICH prototype

CERN Document Server

Peskov, V; Di Mauro, A; Martinengo, P; Mayani, D; Molnar, L; Nappi, E; Paic, G; Smirnov, N; Anand, H; Shukla, I

2012-01-01

We have built a RICH detector prototype consisting of a liquid C6F14 radiator and six triple Thick Gaseous Electron Multipliers (TGEMs), each of them having an active area of 10x10 cm2. One triple TGEM has been placed behind the liquid radiator in order to detect the beam particles, whereas the other five have been positioned around the central one at a distance to collect the Cherenkov photons. The upstream electrode of each of the TGEM stacks has been coated with a 0.4 micron thick CsI layer. In this paper, we will present the results from a series of laboratory tests with this prototype carried out using UV light, 6 keV photons from 55Fe and electrons from 90Sr as well as recent results of tests with a beam of charged pions where for the first time Cherenkov Ring images have been successfully recorded with TGEM photodetectors. The achieved results prove the feasibility of building a large area Cherenkov detector consisting of a matrix of TGEMs.

Moments Based Framework for Performance Analysis of One-Way/Two-Way CSI-Assisted AF Relaying

KAUST Repository

Xia, Minghua

2012-09-01

When analyzing system performance of conventional one-way relaying or advanced two-way relaying, these two techniques are always dealt with separately and, thus, their performance cannot be compared efficiently. Moreover, for ease of mathematical tractability, channels considered in such studies are generally assumed to be subject to Rayleigh fading or to be Nakagami-$m$ channels with integer fading parameters, which is impractical in typical urban environments. In this paper, we propose a unified moments-based framework for general performance analysis of channel-state-information (CSI) assisted amplify-and-forward (AF) relaying systems. The framework is applicable to both one-way and two-way relaying over arbitrary Nakagami-$m$ fading channels, and it includes previously reported results as special cases. Specifically, the mathematical framework is firstly developed under the umbrella of the weighted harmonic mean of two Gamma-distributed variables in conjunction with the theory of Pad\\\\\\'e approximants. Then, general expressions for the received signal-to-noise ratios of the users in one-way/two-way relaying systems and the corresponding moments, moment generation function, and cumulative density function are established. Subsequently, the mathematical framework is applied to analyze, compare, and gain insights into system performance of one-way and two-way relaying techniques, in terms of outage probability, average symbol error probability, and achievable data rate. All analytical results are corroborated by simulation results as well as previously reported results whenever available, and they are shown to be efficient tools to evaluate and compare system performance of one-way and two-way relaying.