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Sample records for cesium iodide photocathodes

  1. Photoemission and optical constant measurements of a Cesium Iodide thin film photocathode

    International Nuclear Information System (INIS)

    The performance of cesium iodide as a reflective photocathode is presented. The absolute quantum efficiency of a 500 nm thick film of cesium iodide has been measured in the wavelength range 150 nm–200 nm. The optical absorbance has been analyzed in the wavelength range 190 nm–900 nm and the optical band gap energy has been calculated. The dispersion properties were determined from the refractive index using an envelope plot of the transmittance data. The morphological and elemental film composition have been investigated by atomic force microscopy and X-ray photo-electron spectroscopy techniques

  2. Electric field effects on the quantum efficiency of Cesium-iodide photocathodes in gas media

    International Nuclear Information System (INIS)

    We have measured the quantum efficiency (QE) of Cesium iodide photocathodes as a function of the electric field strength in a parallel-plate geometry, in CH4, C2H6 AND i-C4H10 both in charge collection and multiplication modes. It was found that in the collection mode the QE value in gases is lower compared to that of vacuum and is independent on the field; in gas media the QE starts to increase at the transition between collection and multiplication modes and reaches the vacuum value at high gas gain. We explain this effect by a decrease of the electron-molecule elastic backscattering while entering the multiplication mode. We conclude that the electric field effects observed here, would also apply for other photocathodes and gas mixtures. An enhancement of the QE after micro discharges was observed and is discussed in detail. (authors) 30 refs, 10 figs

  3. Photoemission and optical constant measurements of Cesium Iodide thin film photocathode

    CERN Document Server

    Triloki,; Gupta, Nikita; Jammal, Nabeel F A; Singh, B K

    2014-01-01

    Performance of cesium iodide (CsI) as a reflective photocathode is presented. Absolute quantum efficiency (QE) measurement of 500 nm thick CsI film has been carried out in the wavelength range of 150 nm to 200 nm. Optical absorbance of 500 nm thick CsI film in the spectral range of 190 nm to 900 nm is analyzed and optical energy band gap is calculated using Tauc plot. To see the dispersive behavior of CsI film, refractive index has been determined by envelop plot of transmittance data, using Swanepoel method. Additional information on morphological and elemental composition results of CsI film, gained by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively are also reported in present work.

  4. 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.

  5. Sintered wire cesium dispenser photocathode

    Energy Technology Data Exchange (ETDEWEB)

    Montgomery, Eric J; Ives, R. Lawrence; Falce, Louis R

    2014-03-04

    A photoelectric cathode has a work function lowering material such as cesium placed into an enclosure which couples a thermal energy from a heater to the work function lowering material. The enclosure directs the work function lowering material in vapor form through a low diffusion layer, through a free space layer, and through a uniform porosity layer, one side of which also forms a photoelectric cathode surface. The low diffusion layer may be formed from sintered powdered metal, such as tungsten, and the uniform porosity layer may be formed from wires which are sintered together to form pores between the wires which are continuous from the a back surface to a front surface which is also the photoelectric surface.

  6. Kelvin Probe Studies of Cesium Telluride Photocathode for AWA Photoinjector

    OpenAIRE

    Wisniewski, Eric; Velazquez, Daniel; Yusof, Zikri; Spentzouris, Linda; Terry, Jeff; Harkay, Katherine

    2012-01-01

    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 (~50 nC) 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 incl...

  7. Plasma etching of cesium iodide

    International Nuclear Information System (INIS)

    Thick films of cesium iodide (CsI) are often used to convert x-ray images into visible light. Spreading of the visible light within CsI, however, reduces the resolution of the resulting image. Anisotropic etching of the CsI film into an array of micropixels can improve the image resolution by confining light within each pixel. The etching process uses a high-density inductively coupled plasma to pattern CsI samples held by a heated, rf-biased chuck. Fluorine-containing gases such as CF4 are found to enhance the etch rate by an order of magnitude compared to Ar+ sputtering alone. Without inert-gas ion bombardment, however, the CF4 etch becomes self-limited within a few microns of depth due to the blanket deposition of a passivation layer. Using CF4+Ar continuously removes this layer from the lateral surfaces, but the formation of a thick passivation layer on the unbombarded sidewalls of etched features is observed by scanning electron microscopy. At a substrate temperature of 220 deg. C, the minimum ion-bombardment energy for etching is Ei∼50 eV, and the rate depends on Ei1/2 above 65 eV. In dilute mixtures of CF4 and Ar, the etch rate is proportional to the gas-phase density of atomic fluorine. Above 50% CF4, however, the rate decreases, indicating the onset of net surface polymer deposition. These observations suggest that anisotropy is obtained through the ion-enhanced inhibitor etching mechanism. Etching exhibits an Arrhenius-type behavior in which the etch rate increases from ∼40 nm/min at 40 deg. C to 380 nm/min at 330 deg. C. The temperature dependence corresponds to an activation energy of 0.13±0.01 eV. This activation energy is consistent with the electronic sputtering mechanism for alkali halides

  8. Kelvin Probe Studies of Cesium Telluride Photocathode for AWA Photoinjector

    CERN Document Server

    Wisniewski, Eric; Yusof, Zikri; Spentzouris, Linda; Terry, Jeff; Harkay, Katherine

    2012-01-01

    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 (~50 nC) 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.

  9. Scintillator handbook with emphasis on cesium iodide

    Science.gov (United States)

    Tidd, J. L.; Dabbs, J. R.; Levine, N.

    1973-01-01

    This report provides a background of reasonable depth and reference material on scintillators in general. Particular attention is paid to the cesium iodide scintillators as used in the High Energy Astronomy Observatory (HEAO) experiments. It is intended especially for use by persons such as laboratory test personnel who need to obtain a working knowledge of these materials and their characteristics in a short time.

  10. Kelvin probe studies of cesium telluride photocathode for AWA photoinjector

    International Nuclear Information System (INIS)

    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

  11. 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.

  12. Cesium iodide crystals fused to vacuum tube faceplates

    Science.gov (United States)

    Fleck, H. G.

    1964-01-01

    A cesium iodide crystal is fused to the lithium fluoride faceplate of a photon scintillator image tube. The conventional silver chloride solder is then used to attach the faceplate to the metal support.

  13. Characterization of quantum efficiency and robustness of cesium-based photocathodes

    Science.gov (United States)

    Montgomery, Eric J.

    High quantum efficiency, robust photocathodes produce picosecond-pulsed, high-current electron beams for photoinjection applications like free electron lasers. In photoinjectors, a pulsed drive laser incident on the photocathode causes photoemission of short, dense bunches of electrons, which are then accelerated into a relativistic, high quality beam. Future free electron lasers demand reliable photocathodes with long-lived quantum efficiency at suitable drive laser wavelengths to maintain high current density. But faced with contamination, heating, and ion back-bombardment, the highest efficiency photocathodes find their delicate cesium-based coatings inexorably lost. In answer, the work herein presents careful, focused studies on cesium-based photocathodes, particularly motivated by the cesium dispenser photocathode. This is a novel device comprised of an efficiently photoemissive, cesium-based coating deposited onto a porous sintered tungsten substrate, beneath which is a reservoir of elemental cesium. Under controlled heating cesium diffuses from the reservoir through the porous substrate and across the surface to replace cesium lost to harsh conditions---recently shown to significantly extend the lifetime of cesium-coated metal cathodes. This work first reports experiments on coated metals to validate and refine an advanced theory of photoemission already finding application in beam simulation codes. Second, it describes a new theory of photoemission from much higher quantum efficiency cesium-based semiconductors and verifies its predictions with independent experiment. Third, it investigates causes of cesium loss from both coated metal and semiconductor photocathodes and reports remarkable rejuvenation of full quantum efficiency for contaminated cesium-coated surfaces, affirming the dispenser prescription of cesium resupply. And fourth, it details continued advances in cesium dispenser design with much-improved operating characteristics: lower temperature

  14. Kelvin probe studies of cesium telluride photocathode for the AWA photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Velazquez, D.; Wisniewski, E. E.; Yusof, Z.; Harkay, K.; Spentzouris, L.; Terry, J. [Physics Department at Illinois Institute of Technology, Chicago, IL 60616 and High Energy Physics Division at Argonne National Laboratory, Lemont, IL 60439 (United States); High Energy Physics Division at Argonne National Laboratory, Lemont, IL 60439 (United States); Accelerator Science Division at Argonne National Laboratory, Lemont, IL 60439 (United States); Physics Department at Illinois Institute of Technology, Chicago, IL 60616 (United States)

    2012-12-21

    Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (> 1%), is robust in a photoinjector, and long lifetime. This photocathode is fabricated in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch ({approx}50 nC) in a long bunch train. We present some results from 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 light exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating.

  15. X-ray Photoemission Spectroscopy Studies of Cesium Antimonide Photocathodes for Photoinjector Applications

    Science.gov (United States)

    Martini, Irene; Chevallay, Eric; Fedosseev, Valentin; Hessler, Christoph; Neupert, Holger; Nistor, Valentin; Taborelli, Mauro

    Within the CLIC (Compact Linear Collider) project, feasibility studies of a photoinjector option for the drive beam as an alternative to its baseline design using a thermionic electron gun (Geschonke et al. [1]) are on-going. This R&D program covers both the laser and the photocathode side. Cesium antimonide cathodes were produced at CERN by co-deposition onto copper substrates and characterized by photoemission and by XPS (X-ray Photoemission Spectroscopy) analysis. A systematic study on newly produced and used photocathodes was conducted in order to correlate the surface composition to the photoemissive properties.

  16. Thermal emittance measurements of a cesium potassium antimonide photocathode

    OpenAIRE

    Bazarov, Ivan; Cultrera, Luca; Bartnik, Adam; Dunham, Bruce; Karkare, Siddharth; Li, Yulin; Liu, Xianghong; Maxson, Jared; Roussel, William

    2011-01-01

    Thermal emittance measurements of a CsK2Sb photocathode at several laser wavelengths are presented. The emittance is obtained with a solenoid scan technique using a high voltage dc photoemission gun. The thermal emittance is 0.56+/-0.03 mm-mrad/mm(rms) at 532 nm wavelength. The results are compared with a simple photoemission model and found to be in a good agreement.

  17. Thermal emittance measurements of a cesium potassium antimonide photocathode

    Science.gov (United States)

    Bazarov, Ivan; Cultrera, Luca; Bartnik, Adam; Dunham, Bruce; Karkare, Siddharth; Li, Yulin; Liu, Xianghong; Maxson, Jared; Roussel, William

    2011-05-01

    Thermal emittance measurements of a CsK2Sb photocathode at several laser wavelengths are presented. The emittance is obtained with a solenoid scan technique using a high voltage dc photoemission gun. The thermal emittance is 0.56±0.03 mm mrad/mm(rms) at 532 nm wavelength. The results are compared with a simple photoemission model and found to be in a good agreement.

  18. 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.

  19. Thermal emittance and response time of a cesium antimonide photocathode

    Science.gov (United States)

    Cultrera, Luca; Bazarov, Ivan; Bartnik, Adam; Dunham, Bruce; Karkare, Siddharth; Merluzzi, Richard; Nichols, Matthew

    2011-10-01

    Measurements of the intrinsic emittance and response time of a Cs3Sb photocathode are presented. The emittance is obtained with a solenoid scan technique using a high voltage dc photoemission gun. Photoemission response time is evaluated using a RF deflecting cavity synchronized to a picosecond laser pulse train. We find that Cs3Sb has both small mean transverse energy, 160 ± 10 meV at 532 nm laser wavelength, and a prompt response time (below the resolution of our measurement) making it a suitable material for high brightness electron photoinjectors.

  20. Engineering and design properties of thallium-doped sodium iodide and selected properties of sodium-doped cesium iodide

    Science.gov (United States)

    Forrest, K.; Haehner, C.; Heslin, T.; Magida, M.; Uber, J.; Freiman, S.; Hicho, G.; Polvani, R.

    1984-01-01

    Mechanical and thermal properties, not available in the literature but necessary to structural design, using thallium doped sodium iodide and sodium doped cesium iodide were determined to be coefficient of linear thermal expansion, thermal conductivity, thermal shock resistance, heat capacity, elastic constants, ultimate strengths, creep, hardness, susceptibility to subcritical crack growth, and ingot variation of strength. These properties were measured for single and polycrystalline materials at room temperature.

  1. Silver Iodide-Chitosan Nanotag Induced Biocatalytic Precipitation for Self-Enhanced Ultrasensitive Photocathodic Immunosensor.

    Science.gov (United States)

    Gong, Lingshan; Dai, Hong; Zhang, Shupei; Lin, Yanyu

    2016-06-01

    In this work, we first exposed that the application of p-type semiconductor, silver iodide-chitosan nanoparticle (SICNP), acted as peroxidase mimetic to catalyze the bioprecipitation reaction for signal-amplification photocathodic immunosensing of human interleukin-6 (IL-6). After immobilization of captured antibody onto a polyethylenimine-functionalized carbon nitride (CN) matrix, SICNPs as photoactive tags and peroxidase mimetics were labeled on secondary antibodies, which were subsequently introduced onto the sensing interface to construct sandwich immunoassay platform through antigen-antibody specific recognition. Due to the matched energy levels between CN and AgI, the photocurrent intensity and photostability of SICNP were dramatically improved with rapid separation and transportation of photogenerated carriers. Moreover, the insoluble product in effective biocatalytic precipitation reaction served as electron acceptor to scavenge the photoexcited electron, leading to great amplification of the photocurrent signal of SICNP again. With the help of multiamplification processes, this photocathodic immunosensor presented a turn-on photoelectrochemical performance for IL-6, which showed wide linear dynamic range from 10(-6) to 10 pg/mL with the ultralow detection limit of 0.737 ag/mL. This work also performed the promising application of SICNP in developing an ultrasensitive, cost-effective, and enzyme-free photocathodic immunosensor for biomarkers. PMID:27180822

  2. X-ray imaging performance of structured cesium iodide scintillators.

    Science.gov (United States)

    Zhao, Wei; Ristic, Goran; Rowlands, J A

    2004-09-01

    Columnar structured cesium iodide (CsI) scintillators doped with Thallium (Tl) have been used extensively for indirect x-ray imaging detectors. The purpose of this paper is to develop a methodology for systematic investigation of the inherent imaging performance of CsI as a function of thickness and design type. The results will facilitate the optimization of CsI layer design for different x-ray imaging applications, and allow validation of physical models developed for the light channeling process in columnar CsI layers. CsI samples of different types and thicknesses were obtained from the same manufacturer. They were optimized either for light output (HL) or image resolution (HR), and the thickness ranged between 150 and 600 microns. During experimental measurements, the CsI samples were placed in direct contact with a high resolution CMOS optical sensor with a pixel pitch of 48 microns. The modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) of the detector with different CsI configurations were measured experimentally. The aperture function of the CMOS sensor was determined separately in order to estimate the MTF of CsI alone. We also measured the pulse height distribution of the light output from both the HL and HR CsI at different x-ray energies, from which the x-ray quantum efficiency, Swank factor and x-ray conversion gain were determined. Our results showed that the MTF at 5 cycles/mm for the HR type was 50% higher than for the HL. However, the HR layer produces approximately 36% less light output. The Swank factor below K-edge was 0.91 and 0.93 for the HR and HL types, respectively, thus their DQE(0) were essentially identical. The presampling MTF decreased as a function of thickness L. The universal MTF, i.e., MTF plotted as a function of the product of spatial frequency f and CsI thickness L, increased as a function of L. This indicates that the light channeling process in CsI improved the MTF of

  3. Photolithography enhancement by incorporating photoluminescent nanoscale cesium iodide molecular dots into the photoresists

    International Nuclear Information System (INIS)

    This work demonstrated an enhancement effect of photolithograph by the incorporation of photoluminescent nanoscale cesium iodide molecular dots into ultraviolet photoresists. Cesium iodide molecular dots with the size of about 0.4 nm acted as centers of ultraviolet absorption and luminescence which enabled the improvement of the morphology of the figure edges and photosensitivity of photoresist pattern. These photoluminescent molecular dots decreased the light interference while increasing the resist sensitization of the photoresist. The detailed mechanism about the enhancement effects of photoluminescent molecular dots incorporated into photoresists on the ultraviolet absorption, photosensitivity, and light interference has been proposed. This increased effect in the enhancement of photoresists makes way for their potential use for future nanoscale photolithography

  4. High Chloride Doping Levels Stabilize the Perovskite Phase of Cesium Lead Iodide.

    Science.gov (United States)

    Dastidar, Subham; Egger, David A; Tan, Liang Z; Cromer, Samuel B; Dillon, Andrew D; Liu, Shi; Kronik, Leeor; Rappe, Andrew M; Fafarman, Aaron T

    2016-06-01

    Cesium lead iodide possesses an excellent combination of band gap and absorption coefficient for photovoltaic applications in its perovskite phase. However, this is not its equilibrium structure under ambient conditions. In air, at ambient temperature it rapidly transforms to a nonfunctional, so-called yellow phase. Here we show that chloride doping, particularly at levels near the solubility limit for chloride in a cesium lead iodide host, provides a new approach to stabilizing the functional perovskite phase. In order to achieve high doping levels, we first co-deposit colloidal nanocrystals of pure cesium lead chloride and cesium lead iodide, thereby ensuring nanometer-scale mixing even at compositions that potentially exceed the bulk miscibility of the two phases. The resulting nanocrystal solid is subsequently fused into a polycrystalline thin film by chemically induced, room-temperature sintering. Spectroscopy and X-ray diffraction indicate that the chloride is further dispersed during sintering and a polycrystalline mixed phase is formed. Using density functional theory (DFT) methods in conjunction with nudged elastic band techniques, low-energy pathways for interstitial chlorine diffusion into a majority-iodide lattice were identified, consistent with the facile diffusion and fast halide exchange reactions observed. By comparison to DFT-calculated values (with the PBE exchange-correlation functional), the relative change in band gap and the lattice contraction are shown to be consistent with a Cl/I ratio of a few percent in the mixed phase. At these incorporation levels, the half-life of the functional perovskite phase in a humid atmosphere increases by more than an order of magnitude. PMID:27135266

  5. Cesium-iodide-based nanocrystal for the detection of ionizing radiation

    Science.gov (United States)

    Farzaneh, Azadeh; Abdi, Mohammad Reza; Saraee, Khadijeh Rezaee Ebrahim; Mostajaboddavati, Mojtaba; Quaranta, A.

    2016-05-01

    We report on the synthesis of cesium-iodide nanoparticles using sol-gel technique. The structural properties of CsI nanoparticles were characterized by X-ray diffraction and optical properties were followed by optical absorption and UV-vis fluorescence. Intense photoluminescence is also observed, with some spectral tuning possible with ripening time getting a range of emission photon wavelength approximately from 366 to 350 nm. The size effect on CsI luminescence leads to an increase in scintillation light yield, a redshift of the emission bands of the on_center and off_center self_trapped excitons (STEs) and an increase in the contribution of the off_center STEs to the net intrinsic emission yield. The energy transfer from the matrix to CsI nanoparticles is a key characteristic for scintillation detectors. So the scintillation spectra and decay curve to alpha particles of sample were monitored.

  6. Radiolysis of cesium iodide solutions in conditions prevailing in a pressurized water reactor severe accident

    International Nuclear Information System (INIS)

    Measurements were made of I/sub 2/ formed when aqueous cesium iodide (CsI) solutions were exposed to two temperatures, 43 and 950C, with irradiation. Iodine partition coefficients were obtained from the experiments. The parameters varied were dose, CsI concentration, and Cs/sub 2/CO/sub 3/ concentration, in the presence of air-carbon dioxide and air-carbon dioxide-hydrogen mixtures, to provide information to calculate the form in which iodine released from fuel as CsI in a reactor accident might reach the environment. In a series of experiments, a two-compartment cell was used to trap the gaseous iodine produced. In this case, it was found that the quantity of gaseous iodine produced increased approximately linearly with the dose (at the dose rate used)

  7. Experimental and analytical study on cesium iodide behavior in piping in wave experiment

    Energy Technology Data Exchange (ETDEWEB)

    Hidaka, A.; Igarashi, M.; Hashimoto, K.; Sugimoto, J. [Japan Atomic Energy Research Inst., Dep. of Reactor Safety Research, Tokai-mura (Japan); Yoshino, T. [Toshiba Advanced System Corp., Isago Kawasaki-ku (Japan)

    1996-12-01

    The WAVE (Wide range Aerosol model VErification) experiments have been performed at JAERI to investigate cesium iodide (CsI) deposition onto an inner surface of piping wall under typical severe accident conditions. The test facility consists of a dish containing CsI powder, electrical heaters and a straight pipe of 1.5 m in length with diameter of 0.042m. Nitrogen gas and superheated steam were injected into the pipe to carry the vaporized CsI and to simulate the thermohydraulic condition for the PWR hot-leg inlet. Analyses of the experiments have been conducted with a three-dimensional thermohydraulic code, SPRAC and the radionuclide behavior analysis codes, ART and VICTORIA. A clear difference was found in the deposition behavior between nitrogen and steam conditions as carrier gases. For nitrogen gas, the analyses well reproduced the experimental results by closely coupling the CsI behavior and the detailed thermohydraulic analyses. For steam carrier gas, on the contrary, the experimental results could not be well reproduced without the use of larger aerosol size. Since the observed enhancement of aerosol size in superheated steam cannot be explained by existing models, it is necessary to further investigate this mechanisms by experiment and analysis. (author) 34 figs., 23 refs.

  8. Amorphous silicon pixel layers with cesium iodide converters for medical radiography

    International Nuclear Information System (INIS)

    The authors describe the properties of evaporated layers of Cesium Iodide (Thallium activated) deposited on substrates that enable easy coupling to amorphous silicon pixel arrays. The CsI (T1) layers range in thickness from 65 to 220μm. The authors used the two-boat evaporator system to deposit CsI(T1) layers. This system ensures the formation of the scintillator film with homogeneous thallium concentration which is essential for optimizing the scintillation light emission efficiency. The Tl concentration was kept to 0.1--0.2 mole percent for the highest light output. Temperature annealing can affect the microstructure as well as light output of the CsI(T1) film. 200--300 C temperature annealing can increase the light output by a factor of two. The amorphous silicon pixel arrays are p-i-n diodes approximately 1μm thick with transparent electrodes to enable them to detect the scintillation light produced by X-rays incident on the CsI(T1). Digital radiography requires a good spatial resolution. This is accomplished by making the detector pixel size less than 50 μm. The light emission from the CsI(T1) is collimated by techniques involving the deposition process on patterned substrates. The authors have measured MTF of greater than 12 line pairs per mm at the 10% level

  9. Amorphous silicon pixel layers with cesium iodide converters for medical radiography

    International Nuclear Information System (INIS)

    We describe the properties of evaporated layers of Cesium Iodide (Thallium activated) deposited on substrates that enable easy coupling to amorphous silicon pixel arrays. The CsI(Tl) layers range in thickness from 65 to 220μm. We used the two-boat evaporator system to deposit CsI(Tl) layers. This system ensures the formation of the scintillator film with homogenous thallium concentration which is essential for optimizing the scintillation light emission efficiency. The Tl concentration was kept to 0.1--0.2 mole percent for the highest light output. Temperature annealing can affect the microstructure as well as light output of the CsI(Tl) film. 200--300C temperature annealing can increase the light output by a factor of two. The amorphous silicon pixel arrays are p-i-n diodes approximately lμm thick with transparent electrodes to enable them to detect the scintillation light produced by X-rays incident on the CsI(Tl). Digital radiography requires a good spatial resolution. This is accomplished by making the detector pixel size less then 50μm. The light emission from the CsI(Tl) is collimated by techniques involving the deposition process on pattered substrates. We have measured MTF of greater than 12 line pairs per mm at the 10% level

  10. Experimental and analytical study on cesium iodide behavior in piping in wave experiment

    International Nuclear Information System (INIS)

    The WAVE (Wide range Aerosol model VErification) experiments have been performed at JAERI to investigate cesium iodide (CsI) deposition onto an inner surface of piping wall under typical severe accident conditions. The test facility consists of a dish containing CsI powder, electrical heaters and a straight pipe of 1.5 m in length with diameter of 0.042m. Nitrogen gas and superheated steam were injected into the pipe to carry the vaporized CsI and to simulate the thermohydraulic condition for the PWR hot-leg inlet. Analyses of the experiments have been conducted with a three-dimensional thermohydraulic code, SPRAC and the radionuclide behavior analysis codes, ART and VICTORIA. A clear difference was found in the deposition behavior between nitrogen and steam conditions as carrier gases. For nitrogen gas, the analyses well reproduced the experimental results by closely coupling the CsI behavior and the detailed thermohydraulic analyses. For steam carrier gas, on the contrary, the experimental results could not be well reproduced without the use of larger aerosol size. Since the observed enhancement of aerosol size in superheated steam cannot be explained by existing models, it is necessary to further investigate this mechanisms by experiment and analysis. (author) 34 figs., 23 refs

  11. A cesium bromide photocathode excited by 405 nm radiation

    Energy Technology Data Exchange (ETDEWEB)

    Maldonado, J. R.; Cheng, Y. T.; Pease, Fabian W.; Hesselink, L. [Electrical Engineering Department, Stanford University, Stanford, California 94305 (United States); Pianetta, P. [SLAC National Accelerator Center, Menlo Park, CA 94025 (United States)

    2014-07-14

    In several applications, such as electron beam lithography and X-ray differential phase contrast imaging, there is a need for a free electron source with a current density at least 10 A/cm{sup 2} yet can be shaped with a resolution down to 20 nm and pulsed. Additional requirements are that the source must operate in a practical demountable vacuum (>1e-9 Torr) and be reasonably compact. In prior work, a photocathode comprising a film of CsBr on metal film on a sapphire substrate met the requirements except it was bulky because it required a beam (>10 W/cm{sup 2}) of 257 nm radiation. Here, we describe an approach using a 405 nm laser which is far less bulky. The 405 nm laser, however, is not energetic enough to create color centers in CsBr films. The key to our approach is to bombard the CsBr film with a flood beam of about 1 keV electrons prior to operation. Photoelectron efficiencies in the range of 100–1000 nA/mW were demonstrated with lifetimes exceeding 50 h between electron bombardments. We suspect that the electron bombardment creates intraband color centers whence electrons can be excited by the 405 nm photons into the conduction band and thence into the vacuum.

  12. The fabrication of sub-micron size cesium iodide x-ray scintillator

    Science.gov (United States)

    Hun, Chien Wan; Chen, Po Chun; Huang, Ker Jer; Chen, Chien Chon

    2015-05-01

    The cesium iodide (CsI) scintillator can converts incident X-ray into visible light with very high conversion efficiency of optical photons. The incident energy, response time, film thickness, sample size, and spatial resolution require in engineering and medical applications are difference. A smooth and flat surface and single crystal structure of CsI enhance the X-ray to visible light conversion. However, the regular CsI is soft and extremely hygroscopic; it is very difficult to polish to obtain a smooth and optical flat plane. In order to obtain a good quality of CsI scintillator for X-ray application we used an ordering channel as template and formed sub-micron CsI wire in the template. The fabrication process including: (1) Ordering structure of nano or sub-micron channels were made by an anodization method; (2) fill CsI scintillated film on the channel by CsI solution, (3) fill CsI melt into the channel formation single crystal of sub-micron crystalline scintillator after solidification. The non-vacuum processes of anodization and solidication methods were used for the sub-micron CsI scintillator column formation that is cost down the scintillator fabrication. In addition, through the fabrication method, the ordering structure scintillator of scintillator can be made by anodic treatment and die casting technology with low cost and rapid production; moreover, the film oxidized metal tubes of the tubular template can be further manufactured to nano tubes by adjusting electrolyte composition, electrolysis voltage, and processing time of anodic treatment, and the aperture size, the thickness and the vessel density of the nano tube can be controlled and ranged from 10 nm to 500 nm, 0.1 μm to 1000 μm, and hundred million to thousand billion tube/cm2, respectively.

  13. Development of crystals based in cesium iodide for application as radiation detectors

    International Nuclear Information System (INIS)

    Inorganic scintillators with fast luminescence decay time, high density and high light output have been the object of studies for application in nuclear physics, high energy physics, nuclear tomography and other fields of science and engineering. Scintillation crystals based on cesium iodide (CsI) are matters with relatively low higroscopy, high atomic number, easy handling and low cost, characteristics that favor their use as radiation detectors. In this work, the growth of pure CsI crystals, CsI:Br and CsI:Pb, using the Bridgman technique, is described. The concentration of the bromine doping element (Br) was studied in the range of 1,5x10-1 M to 10-2 M and the lead (Pb) in the range of 10-2 M to 5x10-4 M. To evaluate the scintillators developed, systematic measurements were carried out for luminescence emission and luminescence decay time for gamma radiation, optical transmittance assays, Vickers micro-hardness assays, determination of the doping elements distribution along the grown crystals and analysis of crystals response to the gamma radiation in the energy range of 350 keV to 1330 keV and alpha particles from a 241Am source, with energy of 5.54 MeV. It was obtained 13 ns to 19 ns for luminescence decay time for CsI:Br and CsI:Pb crystals. These results were very promising. The results obtained for micro-hardness showed a significant increase in function of the doping elements concentration, when compared to the pure CsI crystal, increasing consequently the mechanical resistance of the grown crystals. The validity of using these crystals as radiation sensors may be seen from the results of their response to gamma radiation and alpha particles. (author)

  14. High Momentum Particle Identification Detector The Study of Cesium Iodide Quantum Efficiency Dependency on Substrate Material, Temperature and Quartz Window

    CERN Document Server

    Wisna, Gde Bimananda M

    2014-01-01

    The Cesium Iodide (CsI) is used as a material for detecting Cherenkov radiation produced by high momentum particle in High Momentum Particle Identification Detector (HMPID) at ALICE Experiment at CERN. This work provides investigation and analysis of The Quantum Efficiency (QE) result of CsI which is deposited on five samples substrates such as copper passivated red, copper passivated yellow, aluminium, copper coated with nickel and copper coated with nickel then coated with gold. The measurement of five samples is held under temperature $60^{0}$ C and $25^{0}$ C (room temperature) and also with optical quartz window which can be adjusted to limit the wavelength range which reach the CsI. The result shows there are dependency of substrate, temperature due to enhancement effect and also quartz windows usage on QE of CsI. The results of five samples is then compared and analyzed.

  15. Elastic and inelastic scattering of cesium, cesium iodide, and cesium chloride by argon and xenon in the crossed atomic and molecular beams

    International Nuclear Information System (INIS)

    Velocity and angular distributions of cesium atoms and two cesium halide molecules scattered by rare gas atoms have been measured for the following systems at the indicated initial relative collision energies, anti E: Cs + Ar, anti E = 0.94, 1.29, and 1.85 kcal/mole; Cs + Xe, E = 1.15, 1.91, and 3.10 kcal/mole; Csl + Ar, anti E = 1.06, 1.46, and 2.08 kcal/mole; CsI + Ar, anti E = 1.36, 1.63, and 1.94 kcal/mole; CsI + Xe, anti E = 1.52, 2.52, and 4.09 kcal/mole. At the collision energies indicated the atom-atom scattering can only be elastic. Thus the experiments with those systems can be used for apparatus calibration and a standard of comparison for the diatom-atom experiments. The velocity distributions in the diatom-atom systems are analyzed for the relative contributions of elastic and inelastic scattering

  16. Physical properties of a new flat panel detector with cesium-iodide technology

    Science.gov (United States)

    Hahn, Andreas; Penchev, Petar; Fiebich, Martin

    2016-03-01

    Flat panel detectors have become the standard technology in projection radiography. Further progress in detector technology will result in an improvement of MTF and DQE. The new detector (DX-D45C; Agfa; Mortsel/Belgium) is based on cesium-iodine crystals and has a change in the detector material and the readout electronics. The detector has a size of 30 cm x 24 cm and a pixel matrix of 2560 x 2048 with a pixel pitch of 124 μm. The system includes an automatic exposure detector, which enables the use of the detector without a connection to the x-ray generator. The physical properties of the detector were determined following IEC 62220-1-1 in a laboratory setting. The MTF showed an improvement compared to the previous version of cesium-iodine based flat-panel detectors. Thereby the DQE is also improved especially for the higher frequencies. The new detector showed an improvement in the physical properties compared to the previous versions. This enables a potential for further dose reductions in clinical imaging.

  17. The behavior of cesium iodide radioaerosols during CsI sublimation from metal surface

    International Nuclear Information System (INIS)

    One of the biologically most dangerous volatile fission products getting into the environment during hypothetical severe accidents at NPPs are CsI radioaerosols. This is the reason why great attention is now being devoted to a study of the behavior of CsI radioaerosols in the steam-gas phase. We studied the behavior of CsI aerosols using a setup made of a steam generator, a reaction chamber with a Pt heater, a condenser, bubblers with a Na2S2O3 solution, and a Petryanov filter. The method of radionuclide diagnostic was used for study of the CsI behavior during sublimation from the metal surface. The theoretical mass ratio between cesium and iodine in the CsI molecule is equal to 1.04. So, an upward deviation from this theoretical value will show an increase in the amount of cesium, and, respectively, a downward deviation will indicate an increase in the amount of iodine. Thus, change in the Cs/I ratio was a parameter with the help of which we considered estimating the extent of the oxidation hydrolysis of CsI aerosols. (orig.)

  18. Application of columnar cesium iodide (CsI) as a secondary-electron emission source to gas avalanche detectors

    International Nuclear Information System (INIS)

    A columnar cesium iodide (CsI) layer as a secondary-electron emission (SEE) source was applied to conventional gas avalanche detectors to improve their operating characteristics. The concentration of the primary electrons to a small interaction region allows gas avalanche detectors to have better spatial and timing resolutions. In this study, the signal enhancement and timing resolution of a microstrip gas chamber (MSGC) coupled with the columnar CsI layer were investigated. A large amount of electron amplification occurred within the columnar CsI layer when it was activated, greatly enhancing the signal pulse amplitude over that coming from the ionization in the gas drift region alone. The measured timing resolution of the MSGC detector having an anode width of 5 μm, a cathode width of 95 μm, and a pitch of 200 μm was about 5.5 ns rms at a reduced gas pressure to 30 torr. The SEE efficiency of the columnar CsI layer was also investigated and estimated with about 6%. (author)

  19. Uranium, Cesium, and Mercury Leaching and Recovery from Cemented Radioactive Wastes in Sulfuric Acid and Iodide Media

    Directory of Open Access Journals (Sweden)

    Nicolas Reynier

    2015-11-01

    Full Text Available The Canadian Nuclear Laboratories (CNL is developing a long-term management strategy for its existing inventory of solid radioactive cemented wastes, which contain uranium, mercury, fission products, and a number of minor elements. The composition of the cemented radioactive waste poses significant impediments to the extraction and recovery of uranium using conventional technology. The goal of this research was to develop an innovative method for uranium, mercury and cesium recovery from surrogate radioactive cemented waste (SRCW. Leaching using sulfuric acid and saline media significantly improves the solubilization of the key elements from the SRCW. Increasing the NaCl concentration from 0.5 to 4 M increases the mercury solubilization from 82% to 96%. The sodium chloride forms a soluble mercury complex when mercury is present as HgO or metallic mercury but not with HgS that is found in 60 °C cured SRCW. Several leaching experiments were done using a sulfuric acid solution with KI to leach SRCW cured at 60 °C and/or aged for 30 months. Solubilization yields are above 97% for Cs and 98% for U and Hg. Leaching using sulfuric acid and KI improves the solubilization of Hg by oxidation of Hg0, as well as HgS, and form a mercury tetraiodide complex. Hg and Cs were selectively removed from the leachate prior to uranium recovery. It was found that U recovery from sulfuric leachate in iodide media using the resin Lewatit TP260 is very efficient. Considering these results, a process including effluent recirculation was applied. Improvements of solubilization due to the recycling of chemical reagents were observed during effluent recirculation.

  20. Response of silicon multistrip detectors and a cesium iodide scintillator to a calcium ion beam of 0.5 GeV/u

    International Nuclear Information System (INIS)

    We have constructed and operated charge preamplifiers for silicon strip detectors with a dynamic range extending from fractions of minimum ionising particle (MIP) up to 16 124 MIPs. These silicon detectors combined with time-of-flight counters and cesium iodide scintillator form a segment of the VENUS detector that has been exposed to a calcium beam of 0.5 GeV/u at the GSI accelerator. The aim of the instrument is the identification of all nuclides of the periodic table of the elements. Measurements of electronic noise, cross-talk among channels and energy deposit resolutions in various experimental conditions for silicon detectors are given. The measured light output of the CsI(Tl) crystal induced by calcium is compared with that extrapolated from lower-energy data of various nuclide species determined in other experiments. The charge resolution for calcium ions, determined by the dE/dx detectors and TOF counters of time resolution of 55±7 ps, amounts to 0.42 charge units (rms). Improvements in ion discrimination with respect to the present detector configuration are considered. (orig.)

  1. Response of silicon multistrip detectors and a cesium iodide scintillator to a calcium ion beam of 0.5 GeV/u

    Energy Technology Data Exchange (ETDEWEB)

    Codino, A.; Miozza, M.; Brunetti, M.T.; Checcucci, B.; Federico, C.; Grimani, C.; Lanfranchi, M.; Macchiaiolo, T.; Menichelli, M.; Maffei, P.; Vocca, H. [Istituto Nazionale di Fisica Nucleare, Perugia (Italy); Plouin, F. [Laboratoire National de Saturne, 91191 Gif-sur-Yvette Cedex (France)

    1997-10-21

    We have constructed and operated charge preamplifiers for silicon strip detectors with a dynamic range extending from fractions of minimum ionising particle (MIP) up to 16 124 MIPs. These silicon detectors combined with time-of-flight counters and cesium iodide scintillator form a segment of the VENUS detector that has been exposed to a calcium beam of 0.5 GeV/u at the GSI accelerator. The aim of the instrument is the identification of all nuclides of the periodic table of the elements. Measurements of electronic noise, cross-talk among channels and energy deposit resolutions in various experimental conditions for silicon detectors are given. The measured light output of the CsI(Tl) crystal induced by calcium is compared with that extrapolated from lower-energy data of various nuclide species determined in other experiments. The charge resolution for calcium ions, determined by the dE/dx detectors and TOF counters of time resolution of 55{+-}7 ps, amounts to 0.42 charge units (rms). Improvements in ion discrimination with respect to the present detector configuration are considered. (orig.). 12 refs.

  2. Photocathode aging in MCP PMT

    International Nuclear Information System (INIS)

    We study aging of alkali-antimonide photocathodes in the microchannel plate photomultiplier tubes (MCP PMT) manufactured in Novosibirsk by ''Ekran FEP'' company. Such PMTs are used in the particle identification systems of KEDR, SND and CMD-3 experiments carried out at e+e− colliders VEPP-4M and VEPP-2000 in the Budker Institute of Nuclear Physics. The quantum efficiency (QE) degradation of a PMT equipped with MCP Chevron has been measured at different photon counting rates from 4⋅107 to 6⋅1010 s−1cm−2. It is found that the QE decrease is proportional to the charge extracted from the MCP nearest to the photocathode rather than to the output charge. The comparison of different types of alkali-antimonide photocathodes has shown that the treatment of photocathode with vapors of cesium and antimony can dramatically reduce the photocathode aging rate. The photocathode lifetime of the best MCP PMT sample has been measured at the photon counting rate of 107 cm−2s−1 and the initial gain of 106. The peak quantum efficiency degraded by 20% after accumulation of 3.3 C/cm2 anode charge.

  3. Development of crystals based in cesium iodide for application as radiation detectors; Desenvolvimento de cristais baseados em iodeto de cesio para aplicacao como detectores de radiacao

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Maria da Conceicao Costa

    2006-07-01

    Inorganic scintillators with fast luminescence decay time, high density and high light output have been the object of studies for application in nuclear physics, high energy physics, nuclear tomography and other fields of science and engineering. Scintillation crystals based on cesium iodide (CsI) are matters with relatively low higroscopy, high atomic number, easy handling and low cost, characteristics that favor their use as radiation detectors. In this work, the growth of pure CsI crystals, CsI:Br and CsI:Pb, using the Bridgman technique, is described. The concentration of the bromine doping element (Br) was studied in the range of 1,5x10{sup -1} M to 10{sup -2} M and the lead (Pb) in the range of 10{sup -2} M to 5x10{sup -4} M. To evaluate the scintillators developed, systematic measurements were carried out for luminescence emission and luminescence decay time for gamma radiation, optical transmittance assays, Vickers micro-hardness assays, determination of the doping elements distribution along the grown crystals and analysis of crystals response to the gamma radiation in the energy range of 350 keV to 1330 keV and alpha particles from a {sup 241}Am source, with energy of 5.54 MeV. It was obtained 13 ns to 19 ns for luminescence decay time for CsI:Br and CsI:Pb crystals. These results were very promising. The results obtained for micro-hardness showed a significant increase in function of the doping elements concentration, when compared to the pure CsI crystal, increasing consequently the mechanical resistance of the grown crystals. The validity of using these crystals as radiation sensors may be seen from the results of their response to gamma radiation and alpha particles. (author)

  4. Fabrication and measurement of regenerable low work function dispenser photocathodes

    Science.gov (United States)

    Moody, Nathan A.

    Laser-switched photoemitters are a source of electrons for high current applications such as free electron lasers. Laser-modulated photoemission permits rapid switching of the electron beam, far surpassing what can be achieved using electric-field gated emission. Photoinjector systems consist of a drive laser producing short bunches of photons and an efficient photocathode, which converts photon bunches into electron beam pulses. Development of both technologies is required, but the scope of this project is restricted to improvement of the photocathode. Most high-efficiency photocathodes employ cesium-based surface coatings to reduce work function and enable efficient electron emission in the visible range. Lifetime is severely limited by the loss of this delicate coating, which degrades rapidly in practical vacuum environments. More robust photocathodes exist, but have much lower efficiency, and place unrealistic demands on drive laser power and stability. This research proposes a novel dispenser concept that dramatically extends the lifetime of high efficiency cesium-based cathodes by continuously or periodically restoring the cesium surface monolayer during an in situ rejuvenation process. Sintered tungsten provides an interface between a cesium reservoir and the photoemitting surface. During temperature-controlled rejuvenation, cesium diffuses through and across the sintered tungsten to create and sustain a low-work function photocathode. The prototype dispenser cathode was fabricated and tested for two modes of operation: continuous and periodic near-room temperature rejuvenation. The data are compared with a photoemission model of partially covered surfaces under design for integration with existing beam simulations. Overall performance suggests that this cesium-delivery mechanism can significantly enhance the efficiency and operational lifetime of a wide variety of present and future cesium-based photocathodes. Also reported are surface characterization, ion

  5. Dose reduction in skeletal and chest radiography using a large-area flat-panel detector based on amorphous silicon and thallium-doped cesium iodide: technical background, basic image quality parameters, and review of the literature

    International Nuclear Information System (INIS)

    The two most frequently performed diagnostic X-ray examinations are those of the extremities and of the chest. Thus, dose reduction in the field of conventional skeletal and chest radiography is an important issue and there is a need to reduce man-made ionizing radiation. The large-area flat-panel detector based on amorphous silicon and thallium-doped cesium iodide provides a significant reduction of radiation dose in skeletal and chest radiography compared with traditional imaging systems. This article describes the technical background and basic image quality parameters of this 43 x 43-cm digital system, and summarizes the available literature (years 2000-2003) concerning dose reduction in experimental and clinical studies. Due to its high detective quantum efficiency and dynamic range compared with traditional screen-film systems, a dose reduction of up to 50% is possible without loss of image quality. (orig.)

  6. Dose reduction in skeletal and chest radiography using a large-area flat-panel detector based on amorphous silicon and thallium-doped cesium iodide: technical background, basic image quality parameters, and review of the literature

    Energy Technology Data Exchange (ETDEWEB)

    Voelk, Markus; Hamer, Okka W.; Feuerbach, Stefan [Department of Diagnostic Radiology, University Hospital of Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg (Germany); Strotzer, Michael [Department of Radiology, Hospital Hohe Warte, Hohe Warte 8, 95445, Bayreuth (Germany)

    2004-05-01

    The two most frequently performed diagnostic X-ray examinations are those of the extremities and of the chest. Thus, dose reduction in the field of conventional skeletal and chest radiography is an important issue and there is a need to reduce man-made ionizing radiation. The large-area flat-panel detector based on amorphous silicon and thallium-doped cesium iodide provides a significant reduction of radiation dose in skeletal and chest radiography compared with traditional imaging systems. This article describes the technical background and basic image quality parameters of this 43 x 43-cm digital system, and summarizes the available literature (years 2000-2003) concerning dose reduction in experimental and clinical studies. Due to its high detective quantum efficiency and dynamic range compared with traditional screen-film systems, a dose reduction of up to 50% is possible without loss of image quality. (orig.)

  7. Towards a Robust, Efficient Dispenser Photocathode: the Effect of Recesiation on Quantum Efficiency

    International Nuclear Information System (INIS)

    Future electron accelerators and Free Electron Lasers (FELs) require high brightness electron sources; photocathodes for such devices are challenged to maintain long life and high electron emission efficiency (high quantum efficiency, or QE). The UMD dispenser photocathode design addresses this tradeoff of robustness and QE. In such a dispenser, a cesium-based surface layer is deposited on a porous substrate. The surface layer can be replenished from a subsurface cesium reservoir under gentle heating, allowing cesium to diffuse controllably to the surface and providing demonstrably more robust photocathodes. In support of the premise that recesiation is able to restore contaminated photocathodes, we here report controlled contamination of cesium-based surface layers with subsequent recesiation and the resulting effect on QE. Contaminant gases investigated include examples known from the vacuum environment of typical electron guns.

  8. Masked Photocathode for Photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Qiang, Ji

    2010-01-21

    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.

  9. Masked Photocathode for Photoinjector

    International Nuclear Information System (INIS)

    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.

  10. Potassium Iodide

    Science.gov (United States)

    Potassium iodide is used to protect the thyroid gland from taking in radioactive iodine that may be released during ... the thyroid gland. You should only take potassium iodide if there is a nuclear radiation emergency and ...

  11. A Masked Photocathode in Photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Qiang, Ji

    2010-12-14

    In this paper, we propose a masked photocathode inside the photoinjector for generating high brightness election 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 secondary electron emission from the photocathode material. The masked photocathode also provides transverse cut-off to a Gaussian laser beam that reduces electron beam emittance growth from nonlinear space-charge effects.

  12. Should 3K zoom function be used for detection of pneumothorax in cesium iodide/amorphous silicon flat-panel detector radiographs presented on 1K-matrix soft copies?

    International Nuclear Information System (INIS)

    The purpose of the study was to evaluate observer performance in the detection of pneumothorax with cesium iodide and amorphous silicon flat-panel detector radiography (CsI/a-Si FDR) presented as 1K and 3K soft-copy images. Forty patients with and 40 patients without pneumothorax diagnosed on previous and subsequent digital storage phosphor radiography (SPR, gold standard) had follow-up chest radiographs with CsI/a-Si FDR. Four observers confirmed or excluded the diagnosis of pneumothorax according to a five-point scale first on the 1K soft-copy image and then with help of 3K zoom function (1K monitor). Receiver operating characteristic (ROC) analysis was performed for each modality (1K and 3K). The area under the curve (AUC) values for each observer were 0.7815, 0.7779, 0.7946 and 0.7066 with 1K-matrix soft copies and 0.8123, 0.7997, 0.8078 and 0.7522 with 3K zoom. Overall detection of pneumothorax was better with 3K zoom. Differences between the two display methods were not statistically significant in 3 of 4 observers (p-values between 0.13 and 0.44; observer 4: p=0.02). The detection of pneumothorax with 3K zoom is better than with 1K soft copy but not at a statistically significant level. Differences between both display methods may be subtle. Still, our results indicate that 3K zoom should be employed in clinical practice. (orig.)

  13. Photocathode RF guns

    International Nuclear Information System (INIS)

    Free-electron oscillators and amplifiers require electron accelerators capable of delivering pulse trains of electron bunches of high charge density in a wiggler or undulator. A high electron density implies a high peak current (100 A to 2000 A) and a low transverse beam emittance ( 8 nC in picoseconds) with extremely small emittances (< 10 π x mm x mrad). Several approaches have been proposed to attain such performance. This article discusses the use of photocathodes in attaining the aforementioned performance requirements. Photocathodes have been used as electron sources in lasertrons and for the production of spin-polarized electrons. A photocathode is a light-activated electron source that gives unprecedented control over all aspects of the electron distribution: peak current, spatial profile, and temporal profile. This control is possible because the electron distribution is not determined by grids or a cathode, but rather by an incident laser pulse on the photocathode. 44 references, 21 figures

  14. Development of Large Area CsI Photocathodes for the ALICE/HMPID RICH Detector

    CERN Document Server

    Hoedlmoser, H; Schyns, E

    2005-01-01

    The work carried out within the framework of this PhD deals with the measurement of the photoelectric properties of large area thin film Cesium Iodide (CsI) photocathodes (PCs) which are to be used as a photon converter in a proximity focusing RICH detector for High Momentum Particle Identification (HMPID) in the ALICE experiment at the LHC. The objective was to commission a VUV-scanner setup for in-situ measurements of the photoelectric response of the CsI PCs immediately after the thin film coating process and the use of this system to investigate the properties of these photon detectors. Prior to this work and prior to the finalization of the ALICE/HMPID detector design, R&D work investigating the properties of CsI PCs had been performed at CERN and at other laboratories in order to determine possible substrates and optimized thin film coating procedures. These R&D studies were usually carried out with small samples on different substrates and with various procedures with sometimes ambiguous result...

  15. 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

  16. Low-work-function surfaces produced by cesium carbonate decomposition

    Science.gov (United States)

    Briere, T. R.; Sommer, A. H.

    1977-01-01

    Cesium carbonate (Cs2CO3) was heated to the decomposition temperature of approximately 600 C. The nonvolatile decomposition products were condensed on a nickel substrate while the carbon dioxide was removed by pumping. The deposited material is characterized by an effective work function of between 1.05 and 1.15 eV at 450 K and by photoemission in the visible and near-infrared region of the spectrum. It is suggested that the deposited material consists of Cs2O, possibly Cs2O2, and adsorbed cesium. Silver, evaporated from a heated silver bead, produced the typical photoemissive and thermionic properties of a silver-oxygen-cesium (S-1) photocathode. The material may be of interest for thermionic energy converters and for the formation of silver-oxygen-cesium photocathodes.

  17. Acicular photomultiplier photocathode structure

    Science.gov (United States)

    Craig, Richard A.; Bliss, Mary

    2003-09-30

    A method and apparatus for increasing the quantum efficiency of a photomultiplier tube by providing a photocathode with an increased surface-to-volume ratio. The photocathode includes a transparent substrate, upon one major side of which is formed one or more large aspect-ratio structures, such as needles, cones, fibers, prisms, or pyramids. The large aspect-ratio structures are at least partially composed of a photoelectron emitting material, i.e., a material that emits a photoelectron upon absorption of an optical photon. The large aspect-ratio structures may be substantially composed of the photoelectron emitting material (i.e., formed as such upon the surface of a relatively flat substrate) or be only partially composed of a photoelectron emitting material (i.e., the photoelectron emitting material is coated over large aspect-ratio structures formed from the substrate material itself.) The large aspect-ratio nature of the photocathode surface allows for an effective increase in the thickness of the photocathode relative the absorption of optical photons, thereby increasing the absorption rate of incident photons, without substantially increasing the effective thickness of the photocathode relative the escape incidence of the photoelectrons.

  18. Potassium Iodide (KI)

    Science.gov (United States)

    ... Planning Information on Specific Types of Emergencies Potassium Iodide (KI) Language: English Español (Spanish) Recommend on Facebook ... I get KI (potassium iodide)? What is Potassium Iodide (KI)? KI (potassium iodide) is a salt of ...

  19. Methyl Iodide

    Science.gov (United States)

    Methyl iodide (MeI, iodomethane, CH3I) was reported as a potential alternative to the stratospheric ozone-depleting fumigant methyl bromide (MeBr) in the mid-1990s (Sims et al., 1995; Ohr et al., 1996). It has since received significant research attention to determine its environmental fate and tran...

  20. In-situ multi-information measurement system for preparing gallium nitride photocathode

    International Nuclear Information System (INIS)

    We introduce the first domestic in-situ multi-information measurement system for a gallium nitride (GaN) photocathode. This system can successfully fulfill heat cleaning and activation for GaN in an ultrahigh vacuum environment and produce a GaN photocathode with a negative electron affinity (NEA) status. Information including the heat cleaning temperature, vacuum degree, photocurrent, electric current of cesium source, oxygen source, and the most important information about the spectral response, or equivalently, the quantum efficiency (QE) can be obtained during preparation. The preparation of a GaN photocathode with this system indicates that the optimal heating temperature in a vacuum is about 700 °C. We also develop a method of quickly evaluating the atomically clean surface with the vacuum degree versus wavelength curve to prevent possible secondary contamination when the atomic level cleaning surface is tested with X-ray photoelectron spectroscopy. The photocurrent shows a quick enhancement when the current ratio between the cesium source and oxygen source is 1.025. The spectral response of the GaN photocathode is flat in a wavelength range from 240 nm to 365 nm, and an abrupt decline is observed at 365 nm, which demonstrates that with the in-situ multi-information measurement system the NEA GaN photocathode can be successfully prepared. (rapid communication)

  1. DIAMOND AMPLIFIED PHOTOCATHODES.

    Energy Technology Data Exchange (ETDEWEB)

    SMEDLEY,J.; BEN-ZVI, I.; BOHON, J.; CHANG, X.; GROVER, R.; ISAKOVIC, A.; RAO, T.; WU, Q.

    2007-11-26

    High-average-current linear electron accelerators require photoinjectors capable of delivering tens to hundreds of mA average current, with peak currents of hundreds of amps. Standard photocathodes face significant challenges in meeting these requirements, and often have short operational lifetimes in an accelerator environment. We report on recent progress toward development of secondary emission amplifiers for photocathodes, which are intended to increase the achievable average current while protecting the cathode from the accelerator. The amplifier is a thin diamond wafer which converts energetic (few keV) primary electrons into hundreds of electron-hole pairs via secondary electron emission. The electrons drift through the diamond under an external bias and are emitted into vacuum via a hydrogen-terminated surface with negative electron affinity (NEA). Secondary emission gain of over 200 has been achieved. Two methods of patterning diamond, laser ablation and reactive-ion etching (RIE), are being developed to produce the required geometry. A variety of diagnostic techniques, including FTIR, SEM and AFM, have been used to characterize the diamonds.

  2. Dense-Pinch Photocathode

    Science.gov (United States)

    Asmus, John F.; Lovberg, Ralph H.

    1988-05-01

    A promising approach to the generation of low-emittance e-beams for particle beam and FEL application employs a photoelectron cathode. IF such an e-beam source is to be viable at high power, a high-performance hard-UV illuminator is needed. Toward this end, experiments have been performed by illuminating a metal photocathode with the VUV radiation from a laser-guided gas-embedded high-density high-Z pinch. Such a VUV source is interesting because the plasma is created at high density and is optically thick. Thus, it is both a stable and an efficient radiator. Coupled with a copper photocathode it has generated a-beam current densities up to 60 A/sq-cm. The test device has been modified to utilize a pinch formed from a liquid jet in vacuum, rather than the laser-guided discharge in high-pressure gas. This is more suitable for rep-rate operation as it dispenses with the VUV-absorbing interposed gas, the channel-forming laser, and gas transport at high average power. A decane-jet device has been tested at 10 Hz with a peak pulse VUV power of 100 MW.

  3. Electro regeneration of iodide loaded resin. Contributed Paper RD-18

    International Nuclear Information System (INIS)

    Spent resins generated in the nuclear reactor contain essentially cationic activities due to Cesium, Strontium, Cobalt, and anionic activities due to Iodide, Iodate etc with activity loading to the extent of 0.1 Cim-3 and a surface dose of the order of 5 R. It is necessary to convert the spent resin into innocuous, reusable forms. An attempt has been made to regenerate Iodide containing spent resin into OH- electrolytically by using the OH- produced at the cathode compartment of an electrolytic cell. Results show that the regeneration of the spent resin containing Iodide could be completely accomplished electrolytically more efficiently than by addition of alkali. (author)

  4. Study of strontium and cesium migration in fractured crystalline rock

    International Nuclear Information System (INIS)

    The purpose of this investigation has been to study the retardation and dilution of non-active strontium and cesium relative to a non-absorbing substance (iodide) in a well-defined fracture zone in the Finnsjoen field research area. The investigation was carried out in a previously tracer-tested fracture zone. The study has encompassed two separate test runs with prolonged injection of strontium and iodide and of cesium and iodide. The test have shown that: - Strontium is not retarded, but rather absorbed to about 40% at equilibrium. - At injection stop, 36.3% of the injected mass of strontium has been absorbed and there is no deabsorption. -Cesium is retarded a factor of 2-3 and absorbed to about 30% at equilibrium. - At injection stop, 39.4% of the injected mass of cesium has been absorbed. Cesium is deabsorbed after injection stop (400h) and after 1300 hours, only 22% of the injected mass of cesium is absorbed. (author)

  5. Intense Electron Beams from GaAs Photocathodes as a Tool for Molecular and Atomic Physics

    OpenAIRE

    Krantz, C.

    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 stable cathode lifetimes of 24 h or more. ...

  6. Latest bialkali photocathode with ultra high sensitivity

    International Nuclear Information System (INIS)

    Among photosensitive devices in use today, the photomultiplier tube (PMT) is a versatile device providing extremely high sensitivity, exceptionally low noise and ultra-fast response. It can detect photons at ultra low light level such as single photon counting level. One of the most important characteristics of the PMT is the quantum efficiency (QE) of the photocathode. Among various kinds of photocathodes, a bialkali photocathode is commonly used for particle physics experiments since it has higher sensitivity and lower dark current than other photocathodes. QE of the conventional bialkali photocathode is 27%. Since 2007, we have made a significant improvement in the QE of the bialkali photocathode, achieving as high as 43% at peak wavelength by precise control of the photocathode activation process. This photocathode was named ultra bialkali (UBA) and was incorporated into PMTs successfully. Additionally, we have developed another new kind of bialkali photocathode for very low-temperature environments. At -175 oC, the new bialkali photocathode shows good cathode linearity up to 300 nA, and it has 28% QE and lower dark current than the UBA photocathode. A PMT with the new photocathode is expected to be an ideal detector for Dark Matter experiments or double-beta decay.

  7. Cesium-137

    International Nuclear Information System (INIS)

    This sheet belongs to a collection which relates to the use of radionuclides essentially in unsealed sources. Its goal is to gather on a single document the most relevant information as well as the best prevention practices to be implemented. These sheets are made for the persons in charge of radiation protection: users, radioprotection-skill persons, labor physicians. Each sheet treats of: 1 - the radio-physical and biological properties; 2 - the main uses; 3 - the dosimetric parameters; 4 - the measurement; 5 - the protection means; 6 - the areas delimitation and monitoring; 7 - the personnel classification, training and monitoring; 8 - the effluents and wastes; 9 - the authorization and declaration administrative procedures; 10 - the transport; and 11 - the right conduct to adopt in case of incident or accident. This sheet deals specifically with Cesium-137

  8. Direct observation of bi-alkali antimonide photocathodes growth via in operando x-ray diffraction studies

    International Nuclear Information System (INIS)

    Alkali antimonides have a long history as visible-light-sensitive photocathodes. This work focuses on the process of fabrication of the bi-alkali photocathodes, K2CsSb. In-situ synchrotron x-ray diffraction and photoresponse measurements were used to monitor phase evolution during sequential photocathode growth mode on Si(100) substrates. The amorphous-to-crystalline transition for the initial antimony layer was observed at a film thickness of 40 Å . The antimony crystalline structure dissolved upon potassium deposition, eventually recrystallizing upon further deposition into K-Sb crystalline modifications. This transition, as well as the conversion of potassium antimonide to K2CsSb upon cesium deposition, is correlated with changes in the quantum efficiency

  9. Direct observation of bi-alkali antimonide photocathodes growth via in operando x-ray diffraction studies

    Science.gov (United States)

    Ruiz-Osés, M.; Schubert, S.; Attenkofer, K.; Ben-Zvi, I.; Liang, X.; Muller, E.; Padmore, H.; Rao, T.; Vecchione, T.; Wong, J.; Xie, J.; Smedley, J.

    2014-12-01

    Alkali antimonides have a long history as visible-light-sensitive photocathodes. This work focuses on the process of fabrication of the bi-alkali photocathodes, K2CsSb. In-situ synchrotron x-ray diffraction and photoresponse measurements were used to monitor phase evolution during sequential photocathode growth mode on Si(100) substrates. The amorphous-to-crystalline transition for the initial antimony layer was observed at a film thickness of 40 Å . The antimony crystalline structure dissolved upon potassium deposition, eventually recrystallizing upon further deposition into K-Sb crystalline modifications. This transition, as well as the conversion of potassium antimonide to K2CsSb upon cesium deposition, is correlated with changes in the quantum efficiency.

  10. Direct observation of bi-alkali antimonide photocathodes growth via in operando x-ray diffraction studies

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Osés, M.; Ben-Zvi, I.; Liang, X.; Muller, E. [Stony Brook University, Stony Brook, New York 11794 (United States); Schubert, S. [Helmholtz-Zentrum Berlin, Albert-Einstein Str. 15, 12489 Berlin (Germany); Brookhaven National Laboratory, Upton, New York 11973 (United States); Attenkofer, K.; Rao, T.; Smedley, J., E-mail: smedley@bnl.gov [Brookhaven National Laboratory, Upton, New York 11973 (United States); Padmore, H.; Vecchione, T.; Wong, J. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Xie, J. [Argonne National Laboratory, Lemont, Illinois 60439 (United States)

    2014-12-01

    Alkali antimonides have a long history as visible-light-sensitive photocathodes. This work focuses on the process of fabrication of the bi-alkali photocathodes, K{sub 2}CsSb. In-situ synchrotron x-ray diffraction and photoresponse measurements were used to monitor phase evolution during sequential photocathode growth mode on Si(100) substrates. The amorphous-to-crystalline transition for the initial antimony layer was observed at a film thickness of 40 Å . The antimony crystalline structure dissolved upon potassium deposition, eventually recrystallizing upon further deposition into K-Sb crystalline modifications. This transition, as well as the conversion of potassium antimonide to K{sub 2}CsSb upon cesium deposition, is correlated with changes in the quantum efficiency.

  11. Direct observation of bi-alkali antimonide photocathodes growth via in operando x-ray diffraction studies

    Directory of Open Access Journals (Sweden)

    M. Ruiz-Osés

    2014-12-01

    Full Text Available Alkali antimonides have a long history as visible-light-sensitive photocathodes. This work focuses on the process of fabrication of the bi-alkali photocathodes, K2CsSb. In-situ synchrotron x-ray diffraction and photoresponse measurements were used to monitor phase evolution during sequential photocathode growth mode on Si(100 substrates. The amorphous-to-crystalline transition for the initial antimony layer was observed at a film thickness of 40 Å . The antimony crystalline structure dissolved upon potassium deposition, eventually recrystallizing upon further deposition into K-Sb crystalline modifications. This transition, as well as the conversion of potassium antimonide to K2CsSb upon cesium deposition, is correlated with changes in the quantum efficiency.

  12. Photo-cathode preparation system of the A0 photo-injector

    Energy Technology Data Exchange (ETDEWEB)

    Moyses Kuchnir et al.

    2002-08-23

    The A0 Photo-Injector is an electron accelerator located in the AZero high bay area of Fermilab. A pulsed laser system generates electron bunches by the photo-electric effect when hitting a photo-cathode in a 1.5-cell, 1.3 GHz RF gun. A 9-cell, 1.3 GHz superconducting resonant cavity then accelerates the electrons to 15 MeV. The 10 ps time resolved waveform of the laser pulses is transferred to the electron bunches. This report is focused on the first hardware component of this accelerator, the Photo-cathode Preparation System. The reason for its existence is in the nature of the photo-electric material film used: Cs{sub 2}Te (Cesium Telluride), a very reactive compound that once coated on the cathode requires that it be transported and used in ultra high vacuum (UHV), i.e. < 10{sup -9} Torr.

  13. Development of High Quantum Efficiency UV/Blue Photocathode Epitaxial Semiconductor Heterostructures for Scintillation and Cherenkov Radiation Detection

    Science.gov (United States)

    Leopold, Daniel J.

    2002-01-01

    The primary goal of this research project was to further extend the use of advanced heteroepitaxial-semiconductor crystal growth techniques such as molecular beam epitaxy (MBE) and to demonstrate significant gains in UV/blue photonic detection by designing and fabricating atomically-tailored heteroepitaxial GaAlN/GaInN photocathode device structures. This NASA Explorer technology research program has focused on the development of photocathodes for Cherenkov and scintillation radiation detection. Support from the program allowed us to enhance our MBE system to include a nitrogen plasma source and a magnetic bearing turbomolecular pump for delivery and removal of high purity atomic nitrogen during GaAlN/GaInN film growth. Under this program we have also designed, built and incorporated a cesium activation stage. In addition, a connected UHV chamber with photocathode transfer/positioner components as well as a hybrid phototube stage was designed and built to make in-situ quantum efficiency measurements without ever having to remove the photocathodes from UHV conditions. Thus we have constructed a system with the capability to couple atomically-tailored MBE-grown photocathode heterostructures with real high gain readout devices for single photon detection evaluation.

  14. Mercury iodide crystal growth

    Science.gov (United States)

    Cadoret, R.

    1982-01-01

    The purpose of the Mercury Iodide Crystal Growth (MICG) experiment is the growth of near-perfect single crystals of mercury Iodide (HgI2) in a microgravity environment which will decrease the convection effects on crystal growth. Evaporation and condensation are the only transformations involved in this experiment. To accomplish these objectives, a two-zone furnace will be used in which two sensors collect the temperature data (one in each zone).

  15. Cosmic muon tomography of pure cesium iodide calorimeter crystals

    International Nuclear Information System (INIS)

    Scintillation properties of pure CsI crystals used in the shower calorimeter being built for precise determination of the π+→π0e+νe decay rate are reported. Seventy-four individual crystals, polished and wrapped in Teflon foil, were examined in a multiwire drift chamber system specially designed for transmission cosmic muon tomography. Critical elements of the apparatus and reconstruction algorithms enabling measurement of spatial detector optical nonuniformities are described. Results are compared with a Monte Carlo simulation of the light response of an ideal detector. The deduced optical nonuniformity contributions to the FWHM energy resolution of the PIBETA CsI calorimeter for the π+→e+ν 69.8 MeV positrons and the monoenergetic 70.8 MeV photons were 2.7% and 3.7%, respectively. The upper limit of optical nonuniformity correction to the 69.8 MeV positron low-energy tail between 5 and 55 MeV was +0.2%, as opposed to the +0.3% tail contribution for the photon of the equivalent total energy. Imposing the 5 MeV calorimeter veto cut to suppress the electromagnetic losses, GEANT-evaluated positron and photon lineshape tail fractions summed over all above-threshold ADCs were found to be 2.36±0.05 (stat) ±0.20 (sys)% and 4.68±0.07 (stat)±0.20 (sys)%, respectively

  16. Cesium iodide photon converter performance in a gaseous RICH detector

    CERN Document Server

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

    1999-01-01

    The performance of a 48x48 cm sup 2 multi-wire proportional chamber for VUV photon detection in a RICH setup is reported. The MWPC pad cathode was covered with a solid CsI photo converter layer of 230 mu g/cm sup 2 thickness deposited on a resin-stabilized graphite (RSG) coating. Cherenkov light radiated from cosmic muons was detected in the wavelength region 160 nm95% and a constant long-term stability of the photo cathode were observed.

  17. Cosmic muon tomography of pure cesium iodide calorimeter crystals

    CERN Document Server

    Frlez, E; Assamagan, Ketevi A; Brönnimann, C; Flügel, T; Krause, B; Lawrence, D W; Mzhavia, D A; Pocanic, D; Renker, D; Ritt, S; Slocum, P L; Soic, N; Br"onnimann, Ch.; Fl"ugel, Th.

    2000-01-01

    Scintillation properties of pure CsI crystals used in the shower calorimeter being built for precise determination of the pi+ -> pi0 e+ nu decay rate are reported. Seventy-four individual crystals, polished and wrapped in Teflon foil, were examined in a multiwire drift chamber system specially designed for transmission cosmic muon tomography. Critical elements of the apparatus and reconstruction algorithms enabling measurement of spatial detector optical nonuniformities are described. Results are compared with a Monte Carlo simulation of the light response of an ideal detector. The deduced optical nonuniformity contributions to the FWHM energy resolution of the PIBETA CsI calorimeter for the pi+ -> e+ nu 69.8 MeV positrons and the monoenergetic 70.8 MeV photons were 2.7% and 3.7%, respectively. The upper limit of optical nonuniformity correction to the 69.8 MeV positron low-energy tail between 5 MeV and 55 MeV was +0.2%, as opposed to the +0.3% tail contribution for the photon of the equivalent total energy. ...

  18. Cesium chemistry in irradiated fuel; cesium uranates

    International Nuclear Information System (INIS)

    The physico-chemical behaviour of fission products in nuclear fuel during and after irradiation has been studied extensively during the past decades. In spite of the large amount of chemical, crystallographic and thermodynamic data available, the knowledge on the very complicated UO2-fission product system is still far from complete. The paper discusses the multi variant character of uranium in cesium uranates, which has been assessed by a systematic X-ray Photoelectron Spectroscopy (XPS) study of a series of cesium uranates

  19. Progress in the photocathode linac project

    International Nuclear Information System (INIS)

    The progress achieved so far in the Photocathode Linac Project have developed and tested linear accelerator structures at 2856 MHz, commissioned the klystron modulator and microwave systems, and developed the beamline, and are ready to commence acceleration experiments

  20. PHOTOCATHODES FOR THE ENERGY RECOVERY LINACS

    International Nuclear Information System (INIS)

    This paper presents an overview of existing and emerging technologies on electron sources that can service various Energy Recovering Linacs under consideration. Photocathodes that can deliver average currents from 1 mA to 1 A, the pros and cons associated with these cathodes are addressed. Status of emerging technologies such as secondary emitters, cesiated dispenser cathodes, field and photon assisted field emitters and super lattice photocathodes are also reviewed

  1. Free-electron laser triggered photocathodes

    International Nuclear Information System (INIS)

    The possibility of using free-electron laser (FEL) triggered photocathodes to produce high-quality e-beams for self-amplified spontaneous emission or oscillator FEL devices is explored. The use of the same e-beam, driving the photocathode and the FEL, makes the system naturally free of any synchronization problem, arising when an external laser is used. Examples of the interplay between the generation of electron and optical bursts are also investigated

  2. Photocathodes for the energy recovery linacs

    International Nuclear Information System (INIS)

    This paper presents an overview of existing and emerging technologies on electron sources that can service various Energy Recovering Linacs under consideration. Photocathodes that can deliver average currents from 1 mA to 1 A, the pros and cons associated with these cathodes are addressed. Status of emerging technologies such as secondary emitters, cesiated dispenser cathodes, field and photon assisted field emitters and super lattice photocathodes are also reviewed

  3. Photocathodes for the energy recovery linacs

    International Nuclear Information System (INIS)

    This paper presents an overview of existing and emerging technologies on electron sources that can service various energy recovering linacs under consideration. Photocathodes that can deliver average currents from 1 mA to 1 A, the pros and cons associated with these cathodes are addressed. Status of emerging technologies such as secondary emitters, cesiated dispenser cathodes, field and photon assisted field emitters and super lattice photocathodes are also reviewed

  4. Photocathodes for the energy recovery linacs

    Science.gov (United States)

    Rao, T.; Burrill, A.; Chang, X. Y.; Smedley, J.; Nishitani, T.; Hernandez Garcia, C.; Poelker, M.; Seddon, E.; Hannon, F. E.; Sinclair, C. K.; Lewellen, J.; Feldman, D.

    2006-02-01

    This paper presents an overview of existing and emerging technologies on electron sources that can service various energy recovering linacs under consideration. Photocathodes that can deliver average currents from 1 mA to 1 A, the pros and cons associated with these cathodes are addressed. Status of emerging technologies such as secondary emitters, cesiated dispenser cathodes, field and photon assisted field emitters and super lattice photocathodes are also reviewed.

  5. 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.)

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

    International Nuclear Information System (INIS)

    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.)

  7. The sodium/iodide symporter and radio-iodide therapy

    International Nuclear Information System (INIS)

    The sodium/iodide symporter (NIS) is an intrinsic membrane protein that mediates the active transport of iodide into the thyroid and other tissues. NIS plays key roles in thyroid pathophysiology as the route by which iodide reaches the gland for thyroid hormone biosynthesis and as a means for diagnostic scintigraphic imaging and for radio-iodide therapy in hyperthyroidism and thyroid cancer. The continued molecular analysis of NIS clearly holds the potential of an even greater impact on the diagnosis and radio-iodide treatment of cancer, both in thyroid and beyond

  8. Advanced photocathode simulation and theory

    Science.gov (United States)

    Jensen, K. L.; Feldman, D. W.; O'Shea, P. G.

    2003-07-01

    A low work function dispenser type photocathode that is self-annealing or repairing would have a substantial impact on Free Electron Lasers (FELs). On such a cathode, the emitting surface is constantly renewed by replenishment of low-work-function material. A photo-dispenser cathode should operate at a relatively low temperature compared to a conventional dispenser cathode and is anticipated to be robust and long-lived. Coatings cause a reduction in the transport barrier experienced by the electrons through a complex modification of the potential at the surface, e.g., a reduction in work function due to dipole effects. In this work, we describe our theoretical program to address such effects, as part of a program concurrent with experimental efforts to develop dispenser cathodes for use in high power RF photoinjectors. In particular, we discuss the development of a generalised Transmission Coefficient approach, its application to photoemission from metals, and progress towards developing a methodology for the determination of the general emission barrier profile.

  9. Advanced photocathode simulation and theory

    International Nuclear Information System (INIS)

    A low work function dispenser type photocathode that is self-annealing or repairing would have a substantial impact on Free Electron Lasers (FELs). On such a cathode, the emitting surface is constantly renewed by replenishment of low-work-function material. A photo-dispenser cathode should operate at a relatively low temperature compared to a conventional dispenser cathode and is anticipated to be robust and long-lived. Coatings cause a reduction in the transport barrier experienced by the electrons through a complex modification of the potential at the surface, e.g., a reduction in work function due to dipole effects. In this work, we describe our theoretical program to address such effects, as part of a program concurrent with experimental efforts to develop dispenser cathodes for use in high power RF photoinjectors. In particular, we discuss the development of a generalised Transmission Coefficient approach, its application to photoemission from metals, and progress towards developing a methodology for the determination of the general emission barrier profile

  10. Development of photocathodes for gas counters

    International Nuclear Information System (INIS)

    A lot of ways of physics needs the development of high sensibility imaging devices with large sensitive surface. The problems brought by the building of such devices may be solved by the use of gaz counters. But we must sensitize these counters to low energy photons (< 10 eV). We have particularly studied the response of solid state photocathodes working directly into the counter. We show first a method to increase the quantum efficiency of photocathodes. We experiment this method and take few conclusions. We also show a method to measure the photoelectric threshold of a metal under gas and we apply this method. Because of the limitations of our apparatus we have built a system which permit to manufacture and mesure photocathodes. This apparatus which have numerous possibilities and an automatic data taking system is described. We also describe results of its exploitation and the type of investigation that we are going to develop

  11. Photocathode device that replenishes photoemissive coating

    Energy Technology Data Exchange (ETDEWEB)

    Moody, Nathan A.; Lizon, David C.

    2016-06-14

    A photocathode device may replenish its photoemissive coating to replace coating material that desorbs/evaporates during photoemission. A linear actuator system may regulate the release of a replenishment material vapor, such as an alkali metal, from a chamber inside the photocathode device to a porous cathode substrate. The replenishment material deposits on the inner surface of a porous membrane and effuses through the membrane to the outer surface, where it replenishes the photoemissive coating. The rate of replenishment of the photoemissive coating may be adjusted using the linear actuator system to regulate performance of the photocathode device during photoemission. Alternatively, the linear actuator system may adjust a plasma discharge gap between a cartridge containing replenishment material and a metal grid. A potential is applied between the cartridge and the grid, resulting in ejection of metal ions from the cartridge that similarly replenish the photoemissive coating.

  12. 21 CFR 184.1265 - Cuprous iodide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Cuprous iodide. 184.1265 Section 184.1265 Food and... Substances Affirmed as GRAS § 184.1265 Cuprous iodide. (a) Cuprous iodide (copper (I) iodide, CuI, CAS Reg... with potassium iodide under slightly acidic conditions. (b) The ingredient must be of a purity...

  13. 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.

  14. Decorporation of cesium-137

    International Nuclear Information System (INIS)

    Cesium radio-isotopes, especially cesium-137 (137Cs) are among the radionuclides of main importance produced by a fission reaction in reactor or a nuclear weapon explosion. In the environment, 137Cs is a major contaminant which can cause severe β, γirradiations and contaminations. 137Cs is distributed widely and relatively uniformly throughout the body with the highest concentration in skeletal muscles. A treatment becomes difficult afterwards. The purposes of this report are Firstly to compare the Prussian blue verses cobalt and potassium ferrocyanide (D.I. blue) efficiency for the 137Cs decorporation and secondly to assess a chronological treatment with D.I. blue. (author)

  15. On the theory of photocathode rf guns

    Institute of Scientific and Technical Information of China (English)

    GAO Jie

    2009-01-01

    In this paper we give a set of analytical formulae to describe the characteristics of photocathode rf guns at any rf frequencies, such as energy, energy spread, bunch length, out going current, and emittance etc.as functions of the laser injection phase, which are useful in the design and practical operation of rf guns.

  16. Analysis of radioactive cesium

    International Nuclear Information System (INIS)

    The procedure of analysis of cesium-137 in environmental samples is described. The standard measurement of cesium-137 is made by using a standard solution and a low background G-M counter system. Precipitation and dust are collected on a stainless steel pan. The collected samples are treated by evaporation and extraction or ion exchange and adsorption method. The sample is then quantitatively analyzed. The measurement of cesium-137 is made according to the standard of measurement. Samples collected from inland water and sea water are also treated by evaporation or ion exchange method. The measurements of cesium-137 are also made. This manual describes how to collect soil samples. The collected soil is dried and treated to make samples for activity measurement. Activity measurement is made according to the standard of measurement, then the data are analyzed. Samples are also collected from sediment of sea bottom or river bottom, agricultural products, milk, marine organisms, and daily foods. This manual describes on the methods to collect samples and the treatment to make samples for measurement. (Kato, T.)

  17. Hydrogen iodide decomposition

    Science.gov (United States)

    O'Keefe, Dennis R.; Norman, John H.

    1983-01-01

    Liquid hydrogen iodide is decomposed to form hydrogen and iodine in the presence of water using a soluble catalyst. Decomposition is carried out at a temperature between about 350.degree. K. and about 525.degree. K. and at a corresponding pressure between about 25 and about 300 atmospheres in the presence of an aqueous solution which acts as a carrier for the homogeneous catalyst. Various halides of the platinum group metals, particularly Pd, Rh and Pt, are used, particularly the chlorides and iodides which exhibit good solubility. After separation of the H.sub.2, the stream from the decomposer is countercurrently extracted with nearly dry HI to remove I.sub.2. The wet phase contains most of the catalyst and is recycled directly to the decomposition step. The catalyst in the remaining almost dry HI-I.sub.2 phase is then extracted into a wet phase which is also recycled. The catalyst-free HI-I.sub.2 phase is finally distilled to separate the HI and I.sub.2. The HI is recycled to the reactor; the I.sub.2 is returned to a reactor operating in accordance with the Bunsen equation to create more HI.

  18. Sensitivity of cesium chemistry to the O/U radio in UO2+x

    International Nuclear Information System (INIS)

    The effect of O/U ratio on chemical reactivity was investigated in a cesium-iodide/uranium/tungsten system at temperatures up to 2200 K. It was found that slight changes in the oxidation of the urania had a large effect on reactivity. Crushed fresh fuel samples showed little reaction with CsI; however, slightly hyperstoichiometric fuel showed considerable reaction. The tungsten participated in the reaction by removing excess oxygen from the urania, eventually leading to a cesium tungstate species that was analyzed by Fourier Transform Infrared (FTIR) and X-ray diffraction (XRD) techniques. (author)

  19. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Brendel' , V M; Bukin, V V; Garnov, Sergei V; Bagdasarov, V Kh; Denisov, N N; Garanin, Sergey G; Terekhin, V A; Trutnev, Yurii A

    2012-12-31

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation. (laser technologies)

  20. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    Science.gov (United States)

    Brendel', V. M.; Bukin, V. V.; Garnov, Sergei V.; Bagdasarov, V. Kh; Denisov, N. N.; Garanin, Sergey G.; Terekhin, V. A.; Trutnev, Yurii A.

    2012-12-01

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation.

  1. 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.

  2. 21 CFR 172.375 - Potassium iodide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium iodide. 172.375 Section 172.375 Food and... Dietary and Nutritional Additives § 172.375 Potassium iodide. The food additive potassium iodide may be safely used in accordance with the following prescribed conditions: (a) Potassium iodide may be...

  3. Electrochemical reaction rates in a dye sentisised solar cell - the iodide/tri-iodide redox system

    DEFF Research Database (Denmark)

    Bay, Lasse; West, Keld; Winter-Jensen, Bjørn; Jacobsen, Torben

    2006-01-01

    The electrochemical reaction rate of the redox couple iodide / tri-iodide in acetonitrile is characterised by impedance spectroscopy. Different electrode materials relevant for the function of dye-sensitised solar cells (DSSC) are investigated. Preferably, the reaction with the iodide / tri-iodide...... layer on top of the FTO glass to lower the tri-iodide reduction rate....

  4. Cesium reservoir and interconnective components

    International Nuclear Information System (INIS)

    The program objective is to demonstrate the technology readiness of a TFE (thermionic fuel element) suitable for use as the basic element in a thermionic reactor with electric power output in the 0.5 to 5.0 MW range. A thermionic converter must be supplied with cesium vapor for two reasons. Cesium atoms adsorbed on the surface of the emitter cause a reduction of the emitter work function to permit high current densities without excessive heating of the emitter. The second purpose of the cesium vapor is to provide space-charge neutralization in the emitter-collector gap so that the high current densities may flow across the gap unattenuated. The function of the cesium reservoir is to provide a source of cesium atoms, and to provide a reserve in the event that cesium is lost from the plasma by any mechanism. This can be done with a liquid cesium metal reservoir in which case it is heated to the desired temperature with auxiliary heaters. In a TFE, however, it is desirable to have the reservoir passively heated by the nuclear fuel. In this case, the reservoir must operate at a temperature intermediate between the emitter and the collector, ruling out the use of liquid reservoirs. Integral reservoirs contained within the TFE will produce cesium vapor pressures in the desired range at typical electrode temperatures. The reservoir material that appears to be the best able to meet requirements is graphite. Cesium intercalates easily into graphite, and the cesium pressure is insensitive to loading for a given intercalation stage. The goals of the cesium reservoir test program were to verify the performance of Cs-graphite reservoirs in the temperature-pressure range of interest to TFE operation, and to test the operation of these reservoirs after exposure to a fast neutron fluence corresponding to seven year mission lifetime. In addition, other materials were evaluated for possible use in the integral reservoir

  5. Mercuric iodide sensor technology

    International Nuclear Information System (INIS)

    This report describes the improvement in the performance and the manufacturing yield of mercuric iodide detectors achieved by identifying the dominant impurities, carrier traps, and processing steps limiting device performance. Theoretical studies of electron and hole transport in this material set fundamental limits on detector performance and provided a standard against which to compare experimental results. Spectroscopy techniques including low temperature photoluminescence and thermally stimulated current spectroscopy were applied to characterize the deep level traps in this material. Traps and defects that can be introduced into the detector during growth, from the contact, and during the various steps in detector fabrication were identified. Trap energy levels and their relative abundances were determined. Variations in material quality and detector performance at the micron scale were investigated to understand the distribution in electric field in large volume detectors suitable for gamma-ray spectroscopy. Surface aging and contact degradation was studied extensively by techniques including atomic force microscopy, transmission electron microscopy, and variable angle spectroscopic ellipsometry. Preferred handling and processing procedures for maximizing detector performance and yield were established. The manufacturing yield of high resolution gamma-ray detectors was improved from a few percent to more than 30%

  6. Cesium-137 in biosphere

    International Nuclear Information System (INIS)

    The behaviour of cesium-137 in environment is reviewed. Problems on 137Cs migration in environment, on metabolism andbiological effects are considered. Data on nuclide accumulation in various plants, ways of their entering the man's organism are presented. It is marked that the rate of 137Cs metabolism in the man's organism depends considerably on age, sex, temperature of environment, conditions for activity, water and mineral metabolism and some other factors. It is shown that the annual effective equivalent dose per capita will increase to 2000 yr. up to 1 μSv, that constitutes 0.05% of the average value of irradiation by a natural source

  7. Status update on the photocathode RF LINAC project

    International Nuclear Information System (INIS)

    We present the progress achieved so far in the Photocathode Linac Project. We have developed and tested linear accelerator structures at 2856 MHz, designed and performed preliminary tests on the photocathode gun, commissioned the klystron modulator and microwave systems to extract 3.2 MW of pulsed power, developed the beam-line, and are ready to commence acceleration experiments. (author)

  8. Advances in DC photocathode electron guns

    International Nuclear Information System (INIS)

    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

  9. Advances in DC photocathode electron guns

    International Nuclear Information System (INIS)

    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

  10. Advances in DC photocathode electron guns

    International Nuclear Information System (INIS)

    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

  11. Modern theory and applications of photocathodes

    International Nuclear Information System (INIS)

    Over the last thirty years, the Spicer Three-Step model has provided a very useful description of the process of photoemission for both fundamental and practical applications. By treating photoemission in terms of three successive steps-optical absorption, electron transport, and escape across the surface this theory allows photoemission to be related to parameters of the emitter, such as the optical absorption coefficient, electron scattering mechanisms, and the height of the potential barrier at the surface. Using simple equations and established parameters, the Three-Step model predicts the performance of cathodes and provides detailed understanding of the unexpected phenomena that appear when photocathodes are pushed into new practical domains. As an example, time responses are estimated for existing cathodes, and are found to cover a range of six orders of magnitude. Further, the time response is found to be directly related to the sensitivity (i.e., quantum efficiency) of the cathode. The quantum yield systematically decreases with the time response. Thus, metals are predicted to have the shortest time response (as little as 10-15 sec) and the smallest quantum efficiency (as little as 10-4 electrons per photon), whereas the negative affinity photocathodes have high yield (as high as 0.6 electrons per photon) but long response times (as long as 10-9 sec). Other applications of the Three-Step model are discussed

  12. Determination of microamounts of potassium in sodium iodide by atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Microdetermination of potassium in sodium iodide was developed by the standard addition method. Twenty grams of sample were dissolved in 50 ml of water in a quartz beaker. To the solution, 30 ml of concentrated hydrochloric acid and 30 ml of 30% hydrogen peroxide were added, and evaporated to dryness. By this process sodium iodide was converted into sodium chloride. The cake thus obtained was dissolved in water and diluted to exactly 200 ml. To 25 ml aliquots of the solution, the standard potassium and cesium chloride solutions were added and diluted to 50 ml with water; the concentration of potassium was 0 -- 1 mg/l and that of cesium 4 mM. These solutions were introduced into an air-propane flame and the absorbances were measured at 769.9 nm. During the conversion reaction, hydrochloric acid was completely decomposed, and remained hydrogen peroxide had no influence for absorbance, and other backgrounds were negligible. The linear calibration curve was obtained in the range 0 -- 2 mg of potassium per liter. Potassium in sodium iodide was determined by this method within the coefficient of variation of +-(20 -- 3)% in the range (1.7 -- 32.5) ppm. (author)

  13. 21 CFR 582.5634 - Potassium iodide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium iodide. 582.5634 Section 582.5634 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Supplements 1 § 582.5634 Potassium iodide. (a) Product. Potassium iodide. (b) Tolerance. 0.01 percent....

  14. Beam dynamics studies for photocathode RF gun

    International Nuclear Information System (INIS)

    Photocathode RF guns are very popular choice as injector for low emittance beams especially to light sources world wide. In demand for these gun is increasing steadily and efforts are on to make 2.6 cell RF Gun as SAMEER as proto type for future use at various laboratories. The base design of this 2.6 cell RF Gun is ready and fabrication is planned in near future. In this paper, we present beam dynamic study results of the gun and methodology to arrive at the operating point. Simulation results for Gaussian with nano-second pulse length will be discussed in detail and proposal for generation of few MeV beam will be presented. (author)

  15. Femtosecond electron microscopy using photocathode RF gun

    International Nuclear Information System (INIS)

    The revealing and understanding of ultrafast structural-change induced dynamics are essential not only in physics, chemistry and biology, but also are indispensable for the development of new materials, new devices and applications. Both new RF gun based ultrafast relativistic electron diffraction and microscopy (UED and UEM) have being developed in Osaka University to probe directly structural changes at the atomic scale with sub-100 fs temporal resolution in materials. The first prototype of relativistic-energy UEM using a femtosecond photocathode RF gun has been developed. Both ultrafast diffraction and image measurements have been succeeded using a femtosecond electron beam. In this paper, the development of the UEM prototype and the first experiments of relativistic-energy electron imaging will be reported. (author)

  16. 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.

  17. High energy photocathodes for laser fusion diagnostics

    International Nuclear Information System (INIS)

    Laser fusion experiments at the National Ignition Facility require time-resolved x-ray images of the ignition target self-emission. The photon energies are expected to be greater than 10 keV. Photoemission quantum yield measurement data and photoelectron energy spectrum data are presently unavailable in this photon energy range, but are essential in the design of x-ray imaging diagnostics. We developed an apparatus to measure the quantum efficiency of primary and secondary photoelectron emission and to estimate the energy spectrum of the secondary photoelectrons. The apparatus has been tested using photon energies less than 10 keV to allow comparisons with prior work. A method for preparing photocathodes with geometrically enhanced photoefficiency has been developed.

  18. Jefferson Lab IR demo FEL photocathode quantum efficiency scanner

    Science.gov (United States)

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

    2001-12-01

    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.

  19. 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...

  20. Analysis of heterogeneous water vapor uptake by metal iodide cluster ions via differential mobility analysis-mass spectrometry

    International Nuclear Information System (INIS)

    The sorption of vapor molecules onto pre-existing nanometer sized clusters is of importance in understanding particle formation and growth in gas phase environments and devising gas phase separation schemes. Here, we apply a differential mobility analyzer-mass spectrometer based approach to observe directly the sorption of vapor molecules onto iodide cluster ions of the form (MI)xM+ (x = 1-13, M = Na, K, Rb, or Cs) in air at 300 K and with water saturation ratios in the 0.01-0.64 range. The extent of vapor sorption is quantified in measurements by the shift in collision cross section (CCS) for each ion. We find that CCS measurements are sensitive enough to detect the transient binding of several vapor molecules to clusters, which shift CCSs by only several percent. At the same time, for the highest saturation ratios examined, we observed CCS shifts of up to 45%. For x < 4, cesium, rubidium, and potassium iodide cluster ions are found to uptake water to a similar extent, while sodium iodide clusters uptake less water. For x ≥ 4, sodium iodide cluster ions uptake proportionally more water vapor than rubidium and potassium iodide cluster ions, while cesium iodide ions exhibit less uptake. Measured CCS shifts are compared to predictions based upon a Kelvin-Thomson-Raoult (KTR) model as well as a Langmuir adsorption model. We find that the Langmuir adsorption model can be fit well to measurements. Meanwhile, KTR predictions deviate from measurements, which suggests that the earliest stages of vapor uptake by nanometer scale species are not well described by the KTR model

  1. Analysis of heterogeneous water vapor uptake by metal iodide cluster ions via differential mobility analysis-mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Oberreit, Derek [Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Fluid Measurement Technologies, Inc., Saint Paul, Minnesota 55110 (United States); Rawat, Vivek K.; Larriba-Andaluz, Carlos; Ouyang, Hui; McMurry, Peter H.; Hogan, Christopher J., E-mail: hogan108@umn.edu [Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2015-09-14

    The sorption of vapor molecules onto pre-existing nanometer sized clusters is of importance in understanding particle formation and growth in gas phase environments and devising gas phase separation schemes. Here, we apply a differential mobility analyzer-mass spectrometer based approach to observe directly the sorption of vapor molecules onto iodide cluster ions of the form (MI){sub x}M{sup +} (x = 1-13, M = Na, K, Rb, or Cs) in air at 300 K and with water saturation ratios in the 0.01-0.64 range. The extent of vapor sorption is quantified in measurements by the shift in collision cross section (CCS) for each ion. We find that CCS measurements are sensitive enough to detect the transient binding of several vapor molecules to clusters, which shift CCSs by only several percent. At the same time, for the highest saturation ratios examined, we observed CCS shifts of up to 45%. For x < 4, cesium, rubidium, and potassium iodide cluster ions are found to uptake water to a similar extent, while sodium iodide clusters uptake less water. For x ≥ 4, sodium iodide cluster ions uptake proportionally more water vapor than rubidium and potassium iodide cluster ions, while cesium iodide ions exhibit less uptake. Measured CCS shifts are compared to predictions based upon a Kelvin-Thomson-Raoult (KTR) model as well as a Langmuir adsorption model. We find that the Langmuir adsorption model can be fit well to measurements. Meanwhile, KTR predictions deviate from measurements, which suggests that the earliest stages of vapor uptake by nanometer scale species are not well described by the KTR model.

  2. Improved light transitions from scintillators to new photocathode windows

    International Nuclear Information System (INIS)

    Replacement of a quartz photocathode window by an YAlO3 (YAP) window yielded improved light transitions from BGO crystals (1.78 times) and PbWO4 crystals (1.76 times) to the photocathode. This improvement is due to the higher refractive index of YAP (1.95), which matches much better the indices of BGO (2.14) and PbWO4 (2.18) than quartz (1.47). (author)

  3. Advanced 3D Photocathode Modeling and Simulations Final Report

    International Nuclear Information System (INIS)

    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

  4. High quantum efficiency S-20 photocathodes for photon counting applications

    CERN Document Server

    Orlov, Dmitry A; Pinto, Serge Duarte; Glazenborg, Rene; Kernen, Emilie

    2016-01-01

    Based on conventional S-20 processes, a new series of high quantum efficiency (QE) photocathodes has been developed that can be specifically tuned for use in the ultraviolet, blue or green regions of the spectrum. The QE values exceed 30% at maximum response, and the dark count rate is found to be as low as 30 Hz/cm2 at room temperature. This combination of properties along with a fast temporal response makes these photocathodes ideal for application in photon counting detectors.

  5. R and D ERL: Photocathode Deposition and Transport System

    International Nuclear Information System (INIS)

    The purpose of the photocathode deposition and transport system is to (1) produce a robust, high yield multialkali photocathode and (2) have a method of transporting the multialkali photocathode for insertion into a super conducting RF electron gun. This process is only successful if a sufficient quantum efficiency lifetime of the cathode, which is inserted in the SRF electron gun, is maintained. One important element in producing a multialkali photocathode is the strict vacuum requirements of 10-11 torr to assure success in the production of longlived photocathodes that will not have their QE or lifetime depleted due to residual gas poisoning in a poor vacuum. A cutaway view of our third generation deposition system is shown in figure 1. There are certain design criteria and principles required. One must be able to install, remove, rejuvenate and replace a cathode without exposing the source or cathode to atmosphere. The system must allow one to deposit Cs, K, and Sb on a cathode tip surface at pressures in the 10-10 to 10-9 torr range. The cathode needs to be heated to as high as 850 C for cleaning and maintained at 130 C to 150 C during deposition. There should also be the capability for in-situ QE measurements. In addition the preparation of dispenser photocathodes must be accounted for, thus requiring an ion source for cathode cleaning. Finally the transport cart must be mobile and be able to negotiate the ERL facility labyrinth.

  6. Cesium Concentration in MCU Solvent

    International Nuclear Information System (INIS)

    During Modular Caustic-Side Solvent Extraction (CSSX) Unit (MCU) operations, Cs-137 concentrations in product streams will vary depending on the location in the process and on the recent process conditions. Calculations of cesium concentrations under a variety of operating conditions reveal the following: (1) Under nominal operations with salt solution feed containing 1.1 Ci Cs-137 per gallon, the maximum Cs-137 concentration in the process will occur in the strip effluent (SE) and equal 15-16.5 Ci/gal. (2) Under these conditions, the majority of the solvent will contain 0.005 to 0.01 Ci/gal, with a limited portion of the solvent in the contactor stages containing ∼4 Ci/gal. (3) When operating conditions yield product near 0.1 Ci Cs-137/gal in the decontaminated salt solution (DSS), the SE cesium concentration will be the same or lower than in nominal operations, but majority of the stripped solvent will increase to ∼2-3 Ci/gal. (4) Deviations in strip and waste stream flow rates cause the largest variations in cesium content: (a) If strip flow rates deviate by -30% of nominal, the SE will contain ∼23 Ci/gal, although the cesium content of the solvent will increase to only 0.03 Ci/gal; (b) If strip flow rate deviates by -77% (i.e., 23% of nominal), the SE will contain 54 Ci/gal and solvent will contain 1.65 Ci/gal. At this point, the product DSS will just reach the limit of 0.1 Ci/gal, causing the DSS gamma monitors to alarm; and (c) Moderate (+10 to +30%) deviations in waste flow rate cause approximately proportional increases in the SE and solvent cesium concentrations. Recovery from a process failure due to poor cesium stripping can achieve any low cesium concentration required. Passing the solvent back through the contactors while recycling DSS product will produce a ∼70% reduction during one pass through the contactors (assuming the stripping D value is no worse than 0.36). If the solvent is returned to the solvent hold tank (containing additional

  7. The durability of iodide sodalite

    International Nuclear Information System (INIS)

    Highlights: • Dense iodide sodalite prepared by HIP of hydrothermally synthesised powders. • Sodalite was free from leachable secondary phases. • Leach tests indicate self-arresting congruent dissolution. - Abstract: An iodide sodalite wasteform has been prepared by Hot Isostatic Pressing of powder produced by hydrothermal synthesis. The wasteform was free of leachable secondary phases which can mask leaching mechanisms. Leaching is by congruent dissolution and leach rates decrease as Si and Al accumulate in the leachate. Differential normalised leach rates are 0.005–0.01 g m−2 d−1 during the 7–14 day period. This indicates that sodalite dissolution in natural groundwater, already saturated in these elements, will be very low

  8. Iodide uptake by negatively charged clay interlayers?

    Science.gov (United States)

    Miller, Andrew; Kruichak, Jessica; Mills, Melissa; Wang, Yifeng

    2015-09-01

    Understanding iodide interactions with clay minerals is critical to quantifying risk associated with nuclear waste disposal. Current thought assumes that iodide does not interact directly with clay minerals due to electrical repulsion between the iodide and the negatively charged clay layers. However, a growing body of work indicates a weak interaction between iodide and clays. The goal of this contribution is to report a conceptual model for iodide interaction with clays by considering clay mineral structures and emergent behaviors of chemical species in confined spaces. To approach the problem, a suite of clay minerals was used with varying degrees of isomorphic substitution, chemical composition, and mineral structure. Iodide uptake experiments were completed with each of these minerals in a range of swamping electrolyte identities (NaCl, NaBr, KCl) and concentrations. Iodide uptake behaviors form distinct trends with cation exchange capacity and mineral structure. These trends change substantially with electrolyte composition and concentration, but do not appear to be affected by solution pH. The experimental results suggest that iodide may directly interact with clays by forming ion-pairs (e.g., NaI(aq)) which may concentrate within the interlayer space as well as the thin areas surrounding the clay particle where water behavior is more structured relative to bulk water. Ion pairing and iodide concentration in these zones is probably driven by the reduced dielectric constant of water in confined space and by the relatively high polarizability of the iodide species. PMID:26057987

  9. Cesium in the nutrient cycle

    International Nuclear Information System (INIS)

    Most radioactive cesium in forests is deposited in soil, from which it passes into berries and mushrooms, and further to game. The cesium contents of Finnish berries and mushrooms vary depending on the intensity of Chernobyl fallout. Northern Haeme, Pirkanmaa and parts of central Finland received the most fallout. Weather conditions and the environmental factors, and other circumstances during the growth period, also affect the contents. However, consumption of wild berries, mushrooms and game need not be restricted because of radioactivity anywhere in Finland

  10. Cesium contamination of heather honey

    International Nuclear Information System (INIS)

    In heather honey from Lueneburger Heide, FRG, relatively high values of cesium activity were found (up to about 650 Bq/kg). Activity values for heather honey, Calluna vulgaris plants and soil were measured. It is assumed that the origin of this activity is the direct Chernobyl fallout. There may also be a high transfer of cesium from the soil to the Calluna vulgaris plant, but in order to determine the transfer factor, fresh plants are needed, which have grown later than in spring 1986. (author) 21 refs.; 2 figs.; 2 tabs

  11. Iodide uptake by negatively charged clay interlayers?

    International Nuclear Information System (INIS)

    Understanding iodide interactions with clay minerals is critical to quantifying risk associated with nuclear waste disposal. Current thought assumes that iodide does not interact directly with clay minerals due to electrical repulsion between the iodide and the negatively charged clay layers. However, a growing body of work indicates a weak interaction between iodide and clays. The goal of this contribution is to report a conceptual model for iodide interaction with clays by considering clay mineral structures and emergent behaviors of chemical species in confined spaces. To approach the problem, a suite of clay minerals was used with varying degrees of isomorphic substitution, chemical composition, and mineral structure. Iodide uptake experiments were completed with each of these minerals in a range of swamping electrolyte identities (NaCl, NaBr, KCl) and concentrations. Iodide uptake behaviors form distinct trends with cation exchange capacity and mineral structure. These trends change substantially with electrolyte composition and concentration, but do not appear to be affected by solution pH. The experimental results suggest that iodide may directly interact with clays by forming ion-pairs (e.g., NaI(aq)) which may concentrate within the interlayer space as well as the thin areas surrounding the clay particle where water behavior is more structured relative to bulk water. Ion pairing and iodide concentration in these zones is probably driven by the reduced dielectric constant of water in confined space and by the relatively high polarizability of the iodide species. - Highlights: • Iodide sorption experiments were completed with a diverse array of clay minerals. • Iodide uptake trended with CEC and swamping electrolyte identity and concentration. • Results can be explained by considering the formation of ion pairs in clay interlayers

  12. Cesium transport data for HTGR systems

    International Nuclear Information System (INIS)

    Cesium transport data on the release of cesium from HTGR fuel elements are reviewed and discussed. The data available through 1976 are treated. Equations, parameters, and associated variances describing the data are presented. The equations and parameters are in forms suitable for use in computer codes used to calculate the release of metallic fission products from HTGR fuel elements into the primary circuit. The data cover the following processes: (1) diffusion of cesium in fuel kernels and pyrocarbon, (2) sorption of cesium on fuel rod matrix material and on graphite, and (3) migration of cesium in graphite. The data are being confirmed and extended through work in progress

  13. Effect of solution pH on electrochemical oxidation of iodide ion at platinum electrode in sodium perchlorate solution

    International Nuclear Information System (INIS)

    In first several days during the severe accident of nuclear power plants, radioactive iodine-131 is one of the most hazardous volatile fission products which could be released from fuels of nuclear reactors. Due to its high radioactivity, high fission yield up to 2% and hazardous biological effects, many research groups have been studied the chemical behavior of iodine species. Iodine is reported to be released from the fuels as a cesium iodide form, CsI. And, as nuclear fuels are mostly placed in the water pool, it is easily dissolved in the water after released from the fuels. In water, iodide anion could be oxidized into molecular iodine. As the molecular iodine is a volatile species and the oxidizing rate is affected by many environmental facts such as pH, radiolysis products and temperature, the oxidation reaction of the iodide ion has been considered as an important chemical reaction related to the severe accident of nuclear power plants. In present work, the effect of the solution pH on the electrochemical oxidation of iodide anion was carried out using linear sweep voltammetry (LSV) technique in different pH solutions. We confirmed that the electrochemical oxidation reaction of iodide into iodine at Pt electrode is independent on the solution pH

  14. Simulation of imaging with sodium iodide crystals and position-sensitive photomultiplier tubes

    International Nuclear Information System (INIS)

    There has recently been a growing interest in small gamma cameras for medical imaging applications in which full-sized conventional cameras are unsuitable. A prototype miniature gamma camera has been proposed and built at the University of Chicago (UC), and its imaging characteristics are currently being evaluated. The imaging characteristics of miniature gamma cameras that consist of a single sodium iodide (NaI(Tl)) crystal coupled to a position-sensitive photomultiplier tube (PSPMT) have been studied via Monte Carlo simulations. Images obtained with such cameras with the use of conventional position calculations exhibit considerable distortions, particularly compression. This study demonstrates that the distortions result primarily from non-uniform sensitivities of PSPMTs and secondarily from non-linear responses of PSPMTs, light-reflection properties resulting from the treatments of crystals, and light-refractive properties of glass interfaces between crystals and photocathodes. Simulation results are compared to images obtained with a prototype miniature gamma camera

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

    International Nuclear Information System (INIS)

    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

  16. Influence of varied doping structure on photoemissive property of photocathode

    Institute of Scientific and Technical Information of China (English)

    Niu Jun; Zhang Yi-Jun; Chang Ben-Kang; Xiong Ya-Juan

    2011-01-01

    The built-in electric fields within a varied doping GaAs photocathode may promote the transport of electrons from the bulk to the surface, thus the quantum efficiency of the cathode can be enhanced remarkably. But this enhancement,which might be due to the increase in either the number or the energy of electrons reaching the surface, is not clear at present. In this paper, the energy distributions of electrons in a varied doping photocathode and uniform doping photocathode before and after escaping from the cathode surface are analysed, and the number of electrons escaping from the surface in different cases is calculated for the two kinds of photocathodes. The results indicate that the varied doping structure can not only increase the number of electrons reaching the surface but also cause an offset of the electron energy distribution to high energy. That is the root reason for the enhancement of the quantum efficiency of a varied doping GaAs photocathode.

  17. 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.

  18. Effect of plasmonic near field on the emittance of plasmon-enhanced photocathode

    CERN Document Server

    Jiang, Zeng-gong; Li, Xu-dong; Zhang, Meng; Gu, Duan

    2016-01-01

    The introduction of the surface plasmon polarizations makes the emittance of the photocathode complicated. In this paper, the emittance of plasmon-enhanced photocathode is analyzed. It is first demonstrated that the plasmonic near field can increase the emittance of the plasmon-enhanced photocathode. A simulation method has been used to estimate the emittance caused by plasmonic near field, and the suppression method also has been discussed, both of which are significant for the design of high performance plasmon-enhanced photocathode.

  19. Deflecting cavity for a temporal response measurement of a photocathode

    International Nuclear Information System (INIS)

    Technologies for the next generation light sources based on energy-recovery linac (ERL) are under development in our group. Photocathode related technology is a key technology for the ERL based light sources. Temporal shape control of the photocathode gun generated electron beam is indispensable to generate ultra-small emittance electron beam. A 1300 MHz deflecting cavity has been developed for a temporal shape measurement of an electron beam from a 250-kV DC photocathode electron gun. The cavity is a rectangle shaped TM120 mode with the unloaded quality factor Q0=17660. The deflecting angle is ±9.5 mrad for the electron bunch with ±50 ps with 134.7 W input RF power. (author)

  20. A study on robust NEA photocathode

    International Nuclear Information System (INIS)

    Electron source is one of the most important components in the advanced linac based application such as linear colliders, next generation light sources like Free Electron Laser (FEL) and Energy Recovery Linac (ERL). They require polarized and very low emittance electron beam as the electron source. In general, there are strong demands on the high performance cathode giving high polarization, high brightness (high current density and low emittance), and short pulse. NEA (Negative Electron Affinity)-GaAs photocathode is a unique technology which is capable for generating high polarized and extremely low emittance beam. Quantum efficiency of the cathode is high even in near IR region, so it is favor to generate a beam with the high current density from this point of view. These advantages are originated from the NEA surface where the vacuum state is lower than the bottom of the conduction band. On the other hand, the NEA surface is easily damaged, and the extractable current density is limited from this fact. To overcome this disadvantage, a robust NEA surface on GaAs cathode as a replacement of the current Cs-O NEA surface is studied. According to the hetero-junction hypothesis, Cs-Te thin film deposited on GaAs surface forms the NEA surface state. We performed the Cs-Te evaporation experiment on a clean GaAs and photo-electron emission was examined in a wide range of wavelength. We succeeded the activation of GaAs with the Cs-Te evaporation and found a high quantum efficiency up to 900 nm wavelength which strongly suggested a NEA surface formation. (author)

  1. Neutron Detection with Mercuric Iodide

    International Nuclear Information System (INIS)

    Mercuric iodide is a high-density, high-Z semiconducting material useful for gamma ray detection. This makes it convertible to a thermal neutron detector by covering it with a boron rich material and detecting the 478 keV gamma rays resulting from the 10B(n, α)7Li* reaction. However, the 374 barn thermal capture cross section of natHg, makes the detector itself an attractive absorber, and this has been exploited previously. Since previous work indicates that there are no low-energy gamma rays emitted in coincidence with the 368 keV capture gamma from the dominant 199Hg(n, γ)200Hg reaction, only the 368 keV capture gamma is seen with any efficiency a relatively thin (few mm) detector. In this paper we report preliminary measurements of neutrons via capture reactions in a bare mercuric iodide crystal and a crystal covered in 10B-loaded epoxy. The covered detector is an improvement over the bare detector because the presence of both the 478 and 368 keV gamma rays removes the ambiguity associated with the observation of only one of them. Pulse height spectra, obtained with and without lead and cadmium absorbers, showed the expected gamma rays and demonstrated that they were caused by neutrons

  2. Neutron Detection with Mercuric Iodide

    CERN Document Server

    Bell, Z A

    2003-01-01

    Mercuric iodide is a high-density, high-Z semiconducting material useful for gamma ray detection. This makes it convertible to a thermal neutron detector by covering it with a boron rich material and detecting the 478 keV gamma rays resulting from the sup 1 sup 0 B(n, alpha) sup 7 Li* reaction. However, the 374 barn thermal capture cross section of sup n sup a sup t Hg, makes the detector itself an attractive absorber, and this has been exploited previously. Since previous work indicates that there are no low-energy gamma rays emitted in coincidence with the 368 keV capture gamma from the dominant sup 1 sup 9 sup 9 Hg(n, gamma) sup 2 sup 0 sup 0 Hg reaction, only the 368 keV capture gamma is seen with any efficiency a relatively thin (few mm) detector. In this paper we report preliminary measurements of neutrons via capture reactions in a bare mercuric iodide crystal and a crystal covered in sup 1 sup 0 B-loaded epoxy. The covered detector is an improvement over the bare detector because the presence of both ...

  3. Rare, severe hypersensitivity reaction to potassium iodide

    DEFF Research Database (Denmark)

    Nielsen, Anne Sofie Korsholm; Ebbehøj, Eva; Richelsen, Bjørn

    2014-01-01

    The literature reports a large variety of adverse reactions to potassium iodide. A severe hypersensitivity reaction to potassium iodide in a 51-year-old woman with Graves' thyrotoxicosis is described. Following administration the patient developed sialadenitis, conjunctivitis, stomatitis and acne...

  4. Decorporation of cesium-137; Decorporation du cesium-137

    Energy Technology Data Exchange (ETDEWEB)

    Le Fleche, Ph.; Destombe, C.; Grasseau, A.; Mathieu, J.; Chancerelle, Y.; Mestries, J.C. [GMR, Direction des Recherches, Etudes et Techniques, 94 - Arcueil (France)

    1997-12-31

    Cesium radio-isotopes, especially cesium-137 ({sup 137}Cs) are among the radionuclides of main importance produced by a fission reaction in reactor or a nuclear weapon explosion. In the environment, {sup 137}Cs is a major contaminant which can cause severe {beta}, {gamma}irradiations and contaminations. {sup 137}Cs is distributed widely and relatively uniformly throughout the body with the highest concentration in skeletal muscles. A treatment becomes difficult afterwards. The purposes of this report are Firstly to compare the Prussian blue verses cobalt and potassium ferrocyanide (D.I. blue) efficiency for the {sup 137}Cs decorporation and secondly to assess a chronological treatment with D.I. blue. (author)

  5. Large area mercuric iodide photodetectors

    International Nuclear Information System (INIS)

    Results of an investigation of large area mercuric iodide (HgI2) photodetectors are reported. Different entrance contacts were studied, including semitransparent metallic films and conductive liquids. Theoretical calculations of electronic noise of these photodetectors were compared with experimental results. HgI2 photodetectors with active area up to 4 cm2 were matched with NaI(Tl) and CsI(Tl) scintillation crystals and were evaluated as gamma-radiation spectrometers. Energy resolution of 9.3% for gamma radiation of 511 keV with a CsI(Tl) scintillator and energy resolution of 9.0% for gamma radiation of 622 keV with a NaI(Tl) scintillator have been obtained

  6. Large area mercuric iodide photodetectors

    Energy Technology Data Exchange (ETDEWEB)

    Iwanczyk, J.S.; Dabrowski, A.J.; Markakis, J.M.; Ortale, C.; Schnepple, W.F.

    1984-02-01

    Results of an investigation of large area mercuric iodide (HgI/sub 2/) photodetectors are reported. Different entrance contacts were studied, including semitransparent metallic films and conductive liquids. Theoretical calculations of electronic noise of these photodetectors were compared with experimental results. HgI/sub 2/ photodetectors with active area up to 4 cm/sup 2/ were matched with NaI(Tl) and CsI(Tl) scintillation crystals and were evaluated as gamma-radiation spectrometers. Energy resolution of 9.3% for gamma radiation of 511 keV with a CsI(Tl) scintillator and energy resolution of 9.0% for gamma radiation of 622 keV with a NaI(Tl) scintillator have been obtained.

  7. Predissociation dynamics of lithium iodide

    CERN Document Server

    Schmidt, H; Stienkemeier, F; Bogomolov, A S; Baklanov, A V; Reich, D M; Skomorowski, W; Koch, C P; Mudrich, M

    2015-01-01

    The predissociation dynamics of lithium iodide (LiI) in the first excited A-state is investigated for molecules in the gas phase and embedded in helium nanodroplets, using femtosecond pump-probe photoionization spectroscopy. In the gas phase, the transient Li+ and LiI+ ion signals feature damped oscillations due to the excitation and decay of a vibrational wave packet. Based on high-level ab initio calculations of the electronic structure of LiI and simulations of the wave packet dynamics, the exponential signal decay is found to result from predissociation predominantly at the lowest avoided X-A potential curve crossing, for which we infer a coupling constant V=650(20) reciprocal cm. The lack of a pump-probe delay dependence for the case of LiI embedded in helium nanodroplets indicates fast droplet-induced relaxation of the vibrational excitation.

  8. SUPPRESSION OF AFTERPULSING IN PHOTOMULTIPLIERS BY GATING THE PHOTOCATHODE

    Science.gov (United States)

    A number of gating schemes to minimize the long-term afterpulse signal in photomultipliers have been evaluated. Blocking the excitation pulse by gating the photocathode was found to reduce the gate-on afterpulse background by a factor of 230 over that for nongated operation. Thi...

  9. New Photocathode materials for electron-ion-colliders

    Energy Technology Data Exchange (ETDEWEB)

    Lukaszew, Rosa A. [College of William and Mary, Williamsburg, VA (United States)

    2015-02-25

    Our aim has been to explore new photocathode materials and schemes to develop strategies and technologies for next generation nuclear physics accelerator capabilities, particularly for Electron Ion Colliders (EIC). Thus, we investigated thin film deposition and ensuing properties for several adequate magnetic materials applicable to spin-polarized photocathodes. We also implemented a full experimental setup for light incidence at an acute angle onto the photocathode surface in order to excite surface Plasmon resonance hence increasing light absorption by a metallic surface. We successfully tested the setup with a thermionic cathode as well as Plasmonic silver-MgO samples and obtained very encouraging results. Our first results are very encouraging since the photocurrent measured on this preliminary plasmonic Ag-MgO sample under low power (~ 1mW) cw red light from a HeNe laser was 256 pA, thus two orders magnitude larger than that reported by others following also plasmonic approaches. We extended our studies to shorter wavelengths and we also started preliminary work on chemically ordered MnAl thin films –a component of the tertiary Ag-Mn-Al (silmanal) alloy in order to develop spin-polarized photocathodes capable of sustaining surface Plasmon resonance. It is worthwhile mentioning that a graduate student has been directly involved during this project ensuring the training of next generation of scientists in this area of research.

  10. Design and construction a full copper photocathode RF gun

    International Nuclear Information System (INIS)

    The design and construction of an all copper S-band one-and-half cell photocathode electron gun without a choke joint is described. The methods utilized to determine the field balance at the operational frequency without usage of the bead pulling perturbation measurement is given together wit the computational data

  11. Extraction of radioactive cesium from tea leaves

    International Nuclear Information System (INIS)

    Radioactive contamination of foodstuffs attributed to the Fukushima Daiichi nuclear disaster has become a social problem. This study investigated the extraction of radioactive cesium from the contaminated leaves to the tea. The green tea was brewed twice reusing the same leaves to study the difference in extraction of cesium between the first and second brew. Moreover, the extraction of cesium was studied in correlation to brewing time. The concentration of radioactive cesium was determined with gamma spectrometry, and the concentration of caffeine was determined with absorption spectrometry. About 40% of cesium was extracted from leaves in the first brew, and about 80% was extracted in the second brew. The extraction of cesium increased over time, and it reached about 80% after 10 minutes brew. The ratio of radioactive cesium to caffeine decreased linearly over time. This study revealed that the extraction of cesium was higher for the second brew, and a rapid increase in extraction was seen as the tea was brewed for 6 minutes and more. Therefore, the first brew of green tea, which was brewed within 5 minutes, contained the least extraction of radioactive cesium from the contaminated leaves. (author)

  12. Mercuric iodide light detector and related method

    Science.gov (United States)

    Iwanczyk, Jan S.; Barton, Jeff B.; Dabrowski, Andrzej J.; Schnepple, Wayne F.

    1986-01-01

    Apparatus and method for detecting light involve applying a substantially uniform electrical potential difference between first and second spaced surfaces of a body of mercuric iodide, exposing the first surface to light and measuring an electrical current passed through the body in response to the light. The mercuric iodide may be substantially monocrystalline and the potential may be applied between a substantially transparent conductive layer at the first surface and a second conductive layer at the second surface. In a preferred embodiment, the detector is coupled to a scintillator for passage of light to the mercuric iodide in response to ionizing radiation incident on the scintillator.

  13. 21 CFR 520.763a - Dithiazanine iodide tablets.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Dithiazanine iodide tablets. 520.763a Section 520... iodide tablets. (a) Chemical name. 3-Ethyl-2- -benzothiazolium iodide. (b) Specifications. Dithiazanine iodide tablets contain 10 milligrams, 50 milligrams, 100 milligrams, or 200 milligrams of...

  14. 21 CFR 520.763b - Dithiazanine iodide powder.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Dithiazanine iodide powder. 520.763b Section 520... iodide powder. (a) Chemical name. 3-Ethyl-2- -benzothiazoliumiodide. (b) Specifications. Dithiazanine iodide powder contains 200 milligrams of dithiazanine iodide per level standard tablespoon. (c)...

  15. Activity of cesium-134 and cesium-137 in game and mushrooms in Poland

    International Nuclear Information System (INIS)

    The activity of cesium-134 and cesium-137 was measured in mushrooms and game in 1986-1991. The samples were collected all over Poland and most of the measurements were carried out for export purposes. The results indicate that the activity ratio of cesium-137 to cesium-134 in some samples is not comparable to that with fallout after the Chernobyl accident. The analysis of some samples of mushrooms from 1985 showed that the activity of cesium-137 was higher compared to any other foodstuff. The level of contamination varied greatly throughout Poland

  16. Reaction of bis[trialkyl(aryl)arsonium]-1,4-dihydronaphthalene iodides with mercury(2) iodide in aqueous-alcoholic solutions of potassium iodide

    International Nuclear Information System (INIS)

    Composition of mercury complex iodides, formed in the course of interaction between bis[trialkyl(aryl)arsonium]-1,4-dihydronaphthalene iodides and mercury(2) iodide in aqueous-alcoholic solution in the presence of potassium iodide excess was studied using the methods of chemical analysis, conductivity and IR spectroscopy. It was ascertained that under the conditions mentioned bisarsonium triiodomercurates are formed with the yield of 72-87%. The studies conducted confirm the potentiality of formation of mercury complex iodides of [HgI3]- composition in aqueous solutions of alkali metal iodides in the presence of some organic cations

  17. Sublinear effect in light emission from cesium iodide bombarded by keV polyatomic projectiles

    Science.gov (United States)

    Baudin, K.; Parilis, E. S.; Blankenship, J. F.; Van Stipdonk, M. J.; Schweikert, E. A.

    1998-02-01

    Our experiments examined light emission from a CsI target bombarded with polyatomic projectiles [H n+, (NaF) nNa +, with n=1,2; Na +, Cs 2I +, Cs +] at 5-30 keV impact energies. The light emission increases with primary ion velocity as ( V - Vth) α, where Vth is a velocity threshold. The number of photons emitted under one cluster impact increases with the number of atoms in the projectile, displaying a sublinear effect, similar to that reported elsewhere for electron emission. The model of sweeping out electrons has been applied to explain and calculate the observed effect.

  18. A columnar cesium iodide (CsI) drift plane layer for gas avalanche microdetectors

    International Nuclear Information System (INIS)

    A new method is proposed to improve the spatial and time resolutions, and the detection efficiency with respect to the angle of the incident particles, for gas avalanche micro detectors. The new technique uses a thin (∼200 microm) columnar CsI layer at the drift plane that acts as an efficient source of electrons produced by secondary emission due to the incident particles, and as an electron multiplier. In this paper, the authors present the measurements of the electron multiplication factor and detection efficiency of this layer, using a 90Sr β-source

  19. Generic R&D on undoped cesium iodide and lead fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Kierstead, J.A.; Levy, P.W.; Stoll, S.; Woody, C.L. [Brookhaven National Lab., Upton, NY (United States); Goldberg, M.; Horwitz, N.; Skwarnicki, T.; Sobolewski, Z.; Anderson, D.F.; Ramberg, E.J.; Zimmerman, J.

    1991-12-31

    A summary is given on the recent progress on generic R&D on undoped CsI and PbF{sub 2}. Both of these materials are being investigated for use as a high resolution electromagnetic calorimeter for RHIC, as well as for other potential applications. Results are given on the development of a low gain readout system for use with undoped CsI crystals. A study has also been made of radiation damage in both undoped and thallium doped CsI. The progress on the growth of large, high quality PbF{sub 2} crystals, which would be suitable for calorimeter applications, is discussed, and some first test beam results with a prototype PbF{sub 2} calorimeter are given. Finally, results are presented on the improved radiation resistance of the new PbF{sub 2} material.

  20. The effect of surface cleaning on quantum efficiency in AlGaN photocathode

    International Nuclear Information System (INIS)

    Highlights: • In order to preparative the transmission-mode AlGaN photocathodes in the future, the photocathode has a thin emission layer, and the lattice mismatch at the back interface was eased by varying Al composition of AlGaN sub-layer. • The boiling KOH solution and the mixture of sulfuric acid and hydrogen peroxide can effectively remove the alumina and carbon from the AlGaN photocathode surface, respectively. • The quantum efficiency of the activated AlGaN photocathode has up to 35.1% and improved by 50% from that of cleaned by traditional cleaning technology. - Abstract: To improve the quantum efficiency of AlGaN photocathode, various surfaces cleaning techniques for the removal of alumina and carbon from AlGaN photocathode surface were investigated. The atomic compositions of AlGaN photocathode structure and surface were measured by the X-ray photoelectron spectroscopy and Ar+ ion sputtering. It is found that the boiling KOH solution and the mixture of sulfuric acid and hydrogen peroxide, coupled with the thermal cleaning at 850 °C can effectively remove the alumina and carbon from the AlGaN photocathode surface. The quantum efficiency of AlGaN photocathode is improved to 35.1% at 240 nm, an increase of 50% over the AlGaN photocathode chemically cleaned by only the mixed solution of sulfuric acid and hydrogen peroxide and thermally cleaned at 710 °C

  1. Processing. alpha. -mercuric iodide by zone refining

    Energy Technology Data Exchange (ETDEWEB)

    Burger, A.; Morgan, S.H.; Henderson, D.O.; Biao, Y.; Zhang, K.; Silberman, E. (Fisk Univ., Nashville, TN (United States). Dept. of Physics); Nason, D.; van den Berg, L.; Ortale-Baccash, C.; Cross, E. (EG and G Energy Measurements, Inc., Goleta, CA (United States). Santa Barbara Operations)

    1992-01-01

    An investigation is being conducted on zone refining {alpha}-mercuric iodide. Analytical studies using differential scanning calorimetry and anion chromatography indicate that impurities are segregated mainly at the end where zone travel terminates. Early results indicate that single crystals can be readily grown from zone refined material, and the effects of the process on the performance of radiation detectors fabricated from {alpha}-mercuric iodide are being evaluated.

  2. Iodide refining of calcium-thermal zirconium

    International Nuclear Information System (INIS)

    The possibility of high zirconium of calcium - thermal zirconium KTC-HP and metallic wastes production by iodide refining is examined. The impurities behavior is studied,the refining coefficient dependence on the impurity concentration in the initial material is determined. The impurities minimum concentration in iodide zirconium are evaluated by extrapolation.It is determined that the refining efficiency decreases in the range: Ni=Mn > Cr >F>C>N>O>Fe and aluminium and silicon removal during the iodide refining of calcium thermal zirconium is problematic. By comparison of iodide metal of KTC-HP expected quality with the specifications and the iodide zirconium purity real level obtained in the adopted practice the possibility of standard metal production of KTC-HP and metal wastes is demonstrated. The principal merit of KTC - hafnium content <0,01 mass % is preserved. Alloys melting of double or triple on the base of KTC according TS 95.2185-90 with the addition of 35...50 % of iodide zirconium by the method VDP will allow to obtain the alloys KTC-110 and KTC-125 with oxygen fraction of total mass 0,06...0,10% and hafnium content, meeting the world standards

  3. PIXE analyses of cesium in rice grains

    Science.gov (United States)

    Sugai, Hiroyuki; Ishii, Keizo; Matsuyama, Shigeo; Terakawa, Atsuki; Kikuchi, Yohei; Takahashi, Hiroaki; Ishizaki, Azusa; Fujishiro, Fumito; Arai, Hirotsugu; Osada, Naoyuki; Karahashi, Masahiro; Nozawa, Yuichiro; Yamauchi, Shosei; Kikuchi, Kosuke; Koshio, Shigeki; Watanabe, Koji

    2014-01-01

    The Fukushima nuclear power plant accident released vast amounts of radioactive material into the environment. For instance, 134Cs and 137Cs have half-lives of about 2 and 30 years, respectively, and emit many harmful gamma rays. In 2012, rice with radioactivity >100 Bq/kg was occasionally reported in Fukushima prefecture. To determine where and how cesium accumulates in rice, we grew rice in soil containing stable cesium and investigated the distribution of cesium in rice using particle-induced X-ray emission (PIXE). This study found that cesium is accumulated in bran and germ at high concentrations, and white rice contains 40% of the cesium found in brown rice.

  4. Recovery of anhydrous hydrogen iodide

    Science.gov (United States)

    O'Keefe, Dennis R.; McCorkle, Jr., Kenneth H.; de Graaf, Johannes D.

    1982-01-01

    Relatively dry hydrogen iodide can be recovered from a mixture of HI, I.sub.2 and H.sub.2 O. After the composition of the mixture is adjusted so that the amounts of H.sub.2 O and I.sub.2 do not exceed certain maximum limits, subjection of the mixture to superatmospheric pressure in an amount equal to about the vapor pressure of HI at the temperature in question causes distinct liquid phases to appear. One of the liquid phases contains HI and not more than about 1 weight percent water. Often the adjustment in the composition will include the step of vaporization, and the distinct layers appear following the increase in pressure of the vapor mixture. Adjustment in the composition may also include the addition of an extraction agent, such as H.sub.3 PO.sub.4, and even though the adjusted composition mixture contains a significant amount of such an agent, the creation of the distinct liquid phases is not adversely affected.

  5. Electrochemical reaction rates in a dye-sensitised solar cell - the iodide/tri-iodide redox system

    DEFF Research Database (Denmark)

    Bay, L.; West, K.; Winther-Jensen, B.; Jacobsen, T.

    2006-01-01

    The electrochemical reaction rate of the redox couple iodide/tri-iodide in acetonitrile is characterised by impedance spectroscopy. Different electrode materials relevant for the function of dye-sensitised solar cells (DSSC) are investigated. Preferably, the reaction with the iodide/tri-iodide...... layer on top of the FTO glass in lowering the tri-iodide reduction rate. (c) 2005 Elsevier B.V. All rights reserved....

  6. Kinetics of gold dissolution in iodide solutions

    Science.gov (United States)

    Yang, Kang

    Cyanide has been used as a lixiviant for free milling gold ores for a long time. Cyanide solutions are highly toxic and their use poses long term environmental problems. Cyanidation process is efficient for oxide gold ores but it is ineffective for gold ores containing sulfides. Among the noncyanide based lixiviants, iodide has the potential of replacing cyanide due to its ability to leach gold at a wider pH range and higher rate of gold dissolution. The emerging technology of bio-oxidation is an accepted process for pretreatment of sulfide gold ores. The bio-oxidation is conducted at acidic pH which makes direct cyanidation without pH adjustment impractical. On the contrary, iodide leaching of gold from the bio-oxidized ore can be accomplished without any pH adjustment. The present study was undertaken in order to investigate the kinetics of gold dissolution in various iodide-oxidant solutions under conditions similar to those prevailing in a solution containing bio-oxidized ore. The thermodynamic study indicated that gold can be spontaneously dissolved in iodide-hydrogen peroxide, iodide-ferric ion and iodide-persulfate solutions. Dissolution of gold powder was carried out in these solutions and the results showed that the gold dissolution was dependent on solution pH, concentrations of iodide, oxidants and temperature. Gold dissolution was found to increase with decreasing pH and substantial gold dissolution could be achieved at pH ≤ 2. Increasing concentration of oxidant till an optimum oxidant/iodide molar ratio increased gold dissolution and much higher concentration of oxidant would result in a decrease in gold dissolution. With increasing iodide concentration and temperature, gold dissolution increased significantly. The activation energy data which ranged between 9.6 and 13.6 kcal/mole for various oxidants indicated that surface reaction was the rate controlling step. At higher temperatures a change in rate limiting step with passage of time was observed

  7. Multiphoton ionization of atomic cesium

    International Nuclear Information System (INIS)

    We describe experimental studies of resonantly enhanced multiphoton ionization (MPI) of cesium atoms in the presence and absence of an external electric field. In the zero-field studies, photoelectron angular distributions for one- and two-photon resonantly enhanced MPI are compared with the theory of Tang and Lambropoulos. Deviations of experiment from theory are attributed to hyperfine coupling effects in the resonant intermediate state. The agreement between theory and experiment is excellent. In the absence of an external electric field, signal due to two-photon resonant three-photon ionization of cesium via np states is undetectable. Application of an electric field mixes nearby nd and ns levels, thereby inducing excitation and subsequent ionization. Signal due to two-photon excitation of ns levels in field-free experiments is weak due to their small photoionization cross section. An electric field mixes nearby np levels which again allows detectable photoionization signal. For both ns and np states the field induced MPI signal increases as the square of the electric field for a given principal quantum number and increases rapidly with n for a given field strength. Finally, we note that the classical two-photon field-ionization threshold is lower for the case in which the laser polarization and the electric field are parallel than it is when they are perpendicular. 22 references, 11 figures

  8. Femtosecond response time measurements of a Cs2Te photocathode

    CERN Document Server

    Aryshev, A; Honda, Y; Terunuma, N; Urakawa, J

    2015-01-01

    We present the response time measurements of a Cs2Te photocathode illuminated with two 100 fs duration, variable time separation laser pulses at 266 nm wavelength. The response time was confirmed in dispersive region downstream of a 12-cell standing wave S-band acceleration structure using a well-known RF zero-crossing technique. At the same time it was also measured by changing mechanical path-length difference between two micro-bunches. Both methods agree that Cs2Te photocathode time response is of the order of 250 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 further opens a possibility to construct wide-range tunable THz FEL.

  9. Sealed gaseous photomultiplier with CsI photocathode

    International Nuclear Information System (INIS)

    A sealed gaseous photomultiplier tube (PMT) with a CsI photocathode has been developed using a micropattern gas detector (MPGD) made of Pyrex glass. A microblasting technique (MB) was employed for the production of a new hole-type MPGD. We investigated gaseous PMTs with a semi-transparent CsI photocathode for two different gas mixtures of Ne(90%)+i-C4H10 (10%) and Ne (90%)+CF4 (10%) at a gas pressure of 700 torr. Gains of up to 105 were attained with the microblasted glass plate (MB-GP) for both neon gas mixtures. Quantum efficiencies of up to 0.5% were obtained for UV light at the wavelength of 170 nm. The results of the aging test and the characteristics in a high magnetic-field environment are described for the gaseous PMT filled with neon gas mixture.

  10. UV pulse shaping for the photocathode RF gun

    International Nuclear Information System (INIS)

    Recently, manipulation with the drive laser plays a significant role in high brightness electron beam production by the photocathode RF gun. The article takes efforts on the temporal shaping of the driving laser for the photocathode RF gun. Method based on pulse stacking by birefringent crystal of α-BBO serials was tried to directly shape ultraviolet laser pulse. Using four pieces of α-BBO crystals to separate an input UV pulse with appropriate duration into 16 sub-pulses can form a ps-spaced pulse train suitable for coherent THz production. The group delay dispersion induced by the crystals was also carefully considered. To avoid beam deterioration by long path propagation, imaging relay of the shaped pulse was applied.

  11. Pulse selection control for the IR FEL photocathode drive laser

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, K.; Evans, R.; Garza, O. [and others

    1997-08-01

    The method for current control of a photocathode source is described. This system allows for full remote control of a photocathode drive laser for resulting electron beam currents ranging from less than one microamp to a full current ranging from less than one microamp to a full current of five milliamps. All current modes are obtained by gating the drive laser with a series of electro-optical cells. The system remotely generates this control signal by assuming a mode of operation with the following properties selectable: Current mode as continuous or gated, micropulse density, macropulse gate width from single shot to 1ms duration, macropulse synchronization to A/C line voltage (60 Hz) or an external trigger, 60 Hz phase and slewing through 60 Hz when applicable. All selections are derived from programmable logic devices operating from a master-oscillator resulting in a discrete, phase stable, pulse control for the drive laser.

  12. UV pulse shaping for the photocathode RF gun

    Energy Technology Data Exchange (ETDEWEB)

    Yan Lixin, E-mail: yanlx@mail.tsinghua.edu.cn [Accelerator Laboratory, Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Key Laboratory of Particle and Radiation Imaging (Tsinghua University), Ministry of Education, Beijing 100084 (China); Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense, Beijing 100084 (China); Du Qiang; Du Yingchao; Hua Jianfei; Huang Wenhui; Tang Chuanxiang [Accelerator Laboratory, Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Key Laboratory of Particle and Radiation Imaging (Tsinghua University), Ministry of Education, Beijing 100084 (China); Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense, Beijing 100084 (China)

    2011-05-01

    Recently, manipulation with the drive laser plays a significant role in high brightness electron beam production by the photocathode RF gun. The article takes efforts on the temporal shaping of the driving laser for the photocathode RF gun. Method based on pulse stacking by birefringent crystal of {alpha}-BBO serials was tried to directly shape ultraviolet laser pulse. Using four pieces of {alpha}-BBO crystals to separate an input UV pulse with appropriate duration into 16 sub-pulses can form a ps-spaced pulse train suitable for coherent THz production. The group delay dispersion induced by the crystals was also carefully considered. To avoid beam deterioration by long path propagation, imaging relay of the shaped pulse was applied.

  13. Photocathode-Uniformity Tests of the Hamamatsu R5912 Photomultiplier Tubes Used in the Milagro Experiment

    CERN Document Server

    Vasileiou, V; Smith, A J

    2007-01-01

    The Milagro experiment observes the extensive air showers produced by very high energy gamma-rays impacting the Earth's atmosphere. Milagro uses 898 Hamamatsu R5912 Photomultiplier Tubes. To complete our Monte Carlo simulations, we tested the photocathode uniformity of our PMTs. The main finding was that the PMT gain and detection efficiency are a function of the distance from the center of the photocathode. Both quantities become considerably smaller as the illumination position nears the edge of the photocathode.

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

    International Nuclear Information System (INIS)

    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 10-5 torr. (author). 9 figs., 10 refs

  15. Experimental study on preparing gaseous methyl iodide by chlorotrimelthylsilane/sodium iodide

    International Nuclear Information System (INIS)

    The experiments were carried out to study the feasibility of substituting the extremely toxic dimethyl sulfate (DMS) with nontoxic reagents in preparing the gaseous methyl iodide to measure the scrubbing efficiency of iodine adsorber. The test results show that the reaction of chlorotrimelthylsilane/sodium iodide (or potassium iodide) as a iodating agent and phosphate methylesters is a good substitution method, the reaction conditions and productivity of methyl iodide can meet the requirements of both workshop and in-place tests of iodine adsorber, and the substitutes have little influence on the nuclear grade immersed activated carbon filled in the iodine adsorber. The substitution method can substitute the DMS method to prepare gaseous methyl iodide. (authors)

  16. Recent developments in high voltage photocathode DC gun for accelerator

    International Nuclear Information System (INIS)

    A photoinjector which can generate a high brightness, low emittance and short duration electron bunches is required for future light source accelerators and applications such as electron microscopes. A DC high voltage gun which has a semiconductor photocathode in a high DC electric field is one of the technology choices for the generation of high quality electron beam. Many techniques to the development of semiconductor based photoemission gun are introduced in briefly. (author)

  17. Brookhaven Accelerator Test Facility photocathode gun and transport beamline

    International Nuclear Information System (INIS)

    We present an analysis of the electron beam emitted from a laser driven photocathode injector (Gun, operating at 2856 MHZ), through a Transport beamline, to the LINAC entrance for the Brookhaven Accelerator Test Facility (ATF). The beam parameters including beam energy, and emittance are calculated. Some of our results, are tabulated and the phase plots of the beam parameters, from Cathode, through the Transport line elements, to the LINAC entrance, are shown

  18. Applications of Laser and Synchrotron Based ARPES to Photocathode Research

    Energy Technology Data Exchange (ETDEWEB)

    Rameau J.; Smedley J.; Muller, E.; Kidd, T.; Johnson, P.; Allen, P.; Carr, L.; Valla, T.

    2010-10-12

    Laser angle resolved photoelectron spectroscopy (ARPES) provides unique information about angle and energy distribution of photoelectrons. Laser ARPES gives unique insight into how NEA materials work. ARPES combined with some ancillary measurements gives a very complete picture of system electronic physics. For H:C[100] there is now a clear program for engineering as well as development analogous systems. ARPES well suited for identifying 'ideal' photocathodes with intrinsically low emittance and high QE.

  19. Status of the photocathode linac project at CAT

    International Nuclear Information System (INIS)

    We present the progress achieved so far in the Photocathode Linac Project. We have successfully developed, for the first time in CAT, the technology to build linear accelerator structures. We have also developed the klystron modulator and microwave systems, and are ready to commence acceleration experiments. An undulator has been built for a free-electron laser, which can generate intense tunable radiation using the electron beam (author)

  20. Final Report, Photocathodes for High Repetition Rate Light Sources

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Zvi, Ilan [Stony Brook University

    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). 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 b) Development and testing of a diamond amplifier for photocathodes c) Tests of both cathodes in superconducting RF photoguns and copper RF photoguns

  1. 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.

  2. 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.

  3. 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.

  4. Measurement of initial emittance of back illuminated transparent superconducting multi-alkali photocathode

    International Nuclear Information System (INIS)

    We have manufactured the back-illuminated superconducting photocathode for the FEL with high pulse repetition. The novelty of this photocathode is adopting the transparent superconducting thin film LiTi2O4 as a substrate. LTO reflects RF field because of a short penetration depth of superconductor and this feature protects optical components from RF damage. Using the photocathode, a high quality beam with a low energy spread and a low space spread is expected to be produced. This paper presents experimental results of the initial emittance of multi-alkali photocathode on SrTiO3 substrate. (author)

  5. Surface tension of liquid dilute solutions of lead-cesium and bismuth-cesium systems

    International Nuclear Information System (INIS)

    Method of the maximal pressure in a drop was used to measure the surface tension of 15 liquid dilute solutions of lead-cesium system in 0-0.214 at% concentration range and of 12 diluted solutions of bismuth-cesium system in 0-0.160 at.% cesium range from solidification temperature up to 500 dec C. It was found that cesium was characterized as surfactant in lead and bismuth melts. It was established that the temperature coefficient of surface tension changes sufficiently in maximally diluted solutions of alkali metals in bismuth and lead melts. Effect of sodium, potassium, rubidum and cesium on the value of surface tension of lead and bismuth was systematized. Growth of activity in sodium, potassium, rubidium and cesium series was noted

  6. Application of Cesium isotopes in daily life

    International Nuclear Information System (INIS)

    In the world of science, the desire of the scientific community to discover new chemical elements is crucial for the development of new technologies in various fields of knowledge. And the main chemical element addressed by this article is Cesium, but specifically 133Cesium isotope and radioisotope 137Cesium, exemplifying their physical and chemical characteristics, and their applications. This article will also show how these isotopes have provided researchers a breakthrough in the field of radiological medicine and in time and frequency metrology. (author)

  7. Decontamination of radioactive cesium in soil

    International Nuclear Information System (INIS)

    Agricultural soil containing radioactive cesium was decontaminated using an extraction method involving aqueous potassium solutions. Results demonstrated that the potassium solution could extract radioactive cesium from soil artificially contaminated with 137Cs, although extraction rate decreased as time after contamination increased. However, visual examination of radioactivity distribution in soil samples significantly contaminated by the accident at the Fukushima Daiichi nuclear power plant showed that radioactive cesium also existed as insoluble particles. Therefore, reducing the volume of radioactive wastes generated from soil decontamination requires a physical decontamination method combined with chemical treatment. (author)

  8. Studies on cesium uptake by phenolic resins

    International Nuclear Information System (INIS)

    The selective removal of cesium by phenolic ion-exchange resins from highly salted alkaline radioactive solutions was studied. The resins were synthesized by alkaline polycondensation of phenol, resorcinol, catechol, and resorcinol-catechol mixture with formaldehyde and characterized for their moisture regain, ion-exchange (H+ → Na+) capacity, and distribution coefficient (KD) for cesium. The effects of open and sealed curing of the polymers on their properties were studied. The effect of Na+, NaOH, and Cs+ concentration on the uptake of cesium by resorcinol-formaldehyde resin was investigated, in particular. The chemical, thermal, and radiation stabilities of the polymers were also studied

  9. Sorption of cesium on Latvian clays

    International Nuclear Information System (INIS)

    Cesium is like potassium - good solubility and mobile in a ground, easily assimilate in organism expressly brawn woof. It is a problem if pollutant is a radioactive 137Cs. We made experiments to sorption a 2M CsF solution on some Latvian clays which mainly contain hydro micas (cesium content after good elute of clays are in table). We establish, that clay treated with 25 % sulfuric acid adsorb cesium two times more that waste clay. Hereto unstuck elute Cs from clays. (author)

  10. Method for monitoring radioactive cesium concentration in water using cesium adsorption disk and GM survey meter

    International Nuclear Information System (INIS)

    A method for monitoring radioactive cesium concentration in water using a cesium adsorption disk and a GM survey meter has been developed to ascertain whether the water quality meets standards on radiological contaminants in water. In this method, both dissolved and suspended forms of radioactive cesium are collected on the cesium adsorption disk by means of filtration of a water sample. Beta count rate of the disk is converted into radioactivity using a conservative calibration factor obtained here. The present method was applied to monitoring of decontaminated water of an outdoor school swimming pool in Date City after Fukushima Daiichi Nuclear Power Plant accident. (author)

  11. Trapping characteristics for gaseous cesium generated from different cesium compounds by fly ash filter

    International Nuclear Information System (INIS)

    The purpose of this study is to evaluate the applicability of the fly ash ceramic foam filter to trap gaseous cesium generated during the OREOX and sintering processes of DUPIC green pellets. The trapping experiments of gaseous cesium generated from different cesium compounds using fly ash filters were carried out in a two-zone furnace under air and hydrogen (Ar/4% H2) conditions. XRD and SEM analyses were used to analyze reaction products of different cesium compounds with fly ash filters. To manufacture ceramic foam filters, fly ash with a Si/Al mole ratio of 2.1 and polyvinyl alcohol as binder were used. Reaction products formed by the trapping reaction of different cesium compounds with fly ash filters were investigated. The major reaction products of gaseous cesium generated from cesium silicate and CsI by fly ash filters indicated that pollucite (CsAlSi2O6) phase was formed under air and hydrogen conditions when the carrier gas velocity was 2 cm/sec. The minimum reaction temperature of fly ash filter with gaseous cesium was determined as about 600 deg. C. Finally, off-gas treatment system of sintering process in a hot cell of lMEF was explained as an application example of fly ash filter for trapping gaseous cesium. (author)

  12. Luminescent properties of calcium iodide crystals

    International Nuclear Information System (INIS)

    The influence of preparation conditions, temperature and X radiation on luminescent properties of calcium iodide scintillating crystals is studied, the results are provided. The results obtained when studying spectral characteristics of CaI2 and CaI2:H2 crystals in case of optical and X-ray excitation in the temperature range of 90-400 K, allowance made for data obtained when studying luminescent properties of calcium iodide crystals activated by Cl-, Br-, OH- and Ca2+ impurities, permit assumption that band 236 nm observed in excitation spectra of calcium iodide crystals can stem from noncontrolled hydrogen impurity. Luminescence of the crystals with the maximum in the range of 395 nm is assigned to radiation recombination of excitons localized on H- ions

  13. Comparison of the photoemission behaviour between negative electron affinity GaAs and GaN photocathodes

    International Nuclear Information System (INIS)

    In view of the important application of GaAs and GaN photocathodes in electron sources, differences in photoemission behaviour, namely the activation process and quantum yield decay, between the two typical types of III—V compound photocathodes have been investigated using a multi-information measurement system. The activation experiment shows that a surface negative electron affinity state for the GaAs photocathode can be achieved by the necessary Cs—O two-step activation and by Cs activation alone for the GaN photocathode. In addition, a quantum yield decay experiment shows that the GaN photocathode exhibits better stability and a longer lifetime in a demountable vacuum system than the GaAs photocathode. The results mean that GaN photocathodes are more promising candidates for electron source emitter use in comparison with GaAs photocathodes. (interdisciplinary physics and related areas of science and technology)

  14. Adsorption of radioactive iodide by natural zeolites

    International Nuclear Information System (INIS)

    Two natural zeolites from Iranian deposits (clinoptilolite and natrolite) were characterized and their ability for adsorption of iodide from nuclear wastewaters was evaluated. The adsorption behavior was studied on natural and modified zeolites by γ-spectrometry using 131I as radiotracer. Adsorption isotherms and distribution coefficient (Kd) were measured. The results showed that clinoptilolite is a more promising zeolite for removal of iodide compared to natrolite. Furthermore, the adsorption was higher in silver, lead and thallium forms, whereas the lowest desorption was observed in lead modified zeolite. (author)

  15. The partitioning of iodides into steam

    International Nuclear Information System (INIS)

    In order to estimate the likely releases of radioactive iodine during steam generator tube rupture (SGTR) faults, it is necessary to know the relevant partition coefficients as a function of temperature and solution composition. It has been suggested previously that, under SGTR fault conditions, partitioning of free or ion-paired I- into the steam may be more extensive than that for molecular HI. This report uses available information on the partitioning of iodides and other salts to provide a means of estimating the partition coefficient of the iodide ion as a function of boric acid concentration and temperature. (author)

  16. Kinetic Isotope Effects in the Reduction of Methyl Iodide

    DEFF Research Database (Denmark)

    Holm, Torkil

    1999-01-01

    a-Deuterium kinetic isotope effects (KIE's) have been determined for the reaction of methyl iodide with a series of reducing agents. Reagents which transfer hydride ion in an SN2 reaction show small inverse or small normal KIE's. Reagents which transfer an electron to methyl iodide to produce...... methyl radical show large normal KIE's up to 20 % per a-D. Large KIE's were found for the reaction of methyl iodide with sodium, for Pd-catalyzed reaction of methyl iodide with hydrogen, for ET at a platinum cathode, for ET from benzophenone ketyl or from sodium naphthalenide, for iron catalyzed ET from...... a Grignard reagent to methyl iodide, and for reduction of methyl iodide with tributyltin hydride or with gaseous hydrogen iodide. Very small KIE's were found for electron transfer to methyl iodide from magnesium in ether or from sodium in ammonia. The reason may be that these reactions are transport...

  17. Cesium and strontium ion specific exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Yates, S.

    1996-10-01

    This work is one of two parallel projects that are part of an ESP task to develop high-capacity, selective, solid extractants for cesium, strontium, and technetium from nuclear wastes. In this subtask, Pacific Northwest National Laboratory (PNNL) is collaborating with AlliedSignal, Inc. (Des Plaines, Illinois) to develop inorganic ion exchangers that are selective for strontium and cesium from alkaline high-level waste and groundwater streams.

  18. Sorption of Cesium on Latvia clays

    International Nuclear Information System (INIS)

    Cesium is like potassium - good solubility and mobile in a ground, easy assimilates in organism expressly brawn woof. It is a problem if pollutant is radioactive 137Cs. We made experiments to sorption a 2M CsF solution on some Latvian clays which mainly contain hydro micas. We establish that clay treated with 25% sulfuric acid absorb cesium two times more that waste clay. Hereto unstuck elute Cs from clays

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

    International Nuclear Information System (INIS)

    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

  20. Barium iodide and strontium iodide crystals andd scintillators implementing the same

    Science.gov (United States)

    Payne, Stephen A; Cherepy, Nerine J; Hull, Giulia E; Drobshoff, Alexander D; Burger, Arnold

    2013-11-12

    In one embodiment, a material comprises a crystal comprising strontium iodide providing at least 50,000 photons per MeV. A scintillator radiation detector according to another embodiment includes a scintillator optic comprising europium-doped strontium iodide providing at least 50,000 photons per MeV. A scintillator radiation detector in yet another embodiment includes a scintillator optic comprising SrI.sub.2 and BaI.sub.2, wherein a ratio of SrI.sub.2 to BaI.sub.2 is in a range of between 0:1 A method for manufacturing a crystal suitable for use in a scintillator includes mixing strontium iodide-containing crystals with a source of Eu.sup.2+, heating the mixture above a melting point of the strontium iodide-containing crystals, and cooling the heated mixture near the seed crystal for growing a crystal. Additional materials, systems, and methods are presented.

  1. Developments in mercuric iodide gamma ray imaging

    International Nuclear Information System (INIS)

    A mercuric iodide (HgI2) gamma ray imaging array and camera system previously described have been characterized for spatial and energy resolution. Based on these data a new camera is being developed to more fully exploit the potential of the array. Characterization results and design criteria for the new camera will be presented. (orig.)

  2. Developments in mercuric iodide gamma ray imaging

    Science.gov (United States)

    Patt, B. E.; Beyerle, A. G.; Dolin, R. C.; Ortale, C.

    1989-11-01

    A mercuric iodide (HgI2) gamma ray imaging array and camera system previously described have been characterized for spatial and energy resolution. Based on these data a new camera is being developed to more fully exploit the potential of the array. Characterization results and design criteria for the new camera will be presented.

  3. Developments in mercuric iodide gamma ray imaging

    Energy Technology Data Exchange (ETDEWEB)

    Patt, B.E.; Beyerle, A.G.; Dolin, R.C.; Ortale, C.

    1987-01-01

    A mercuric iodide gamma-ray imaging array and camera system previously described has been characterized for spatial and energy resolution. Based on this data a new camera is being developed to more fully exploit the potential of the array. Characterization results and design criterion for the new camera will be presented. 2 refs., 7 figs.

  4. Developments in mercuric iodide gamma ray imaging

    Energy Technology Data Exchange (ETDEWEB)

    Patt, B.E.; Beyerle, A.G.; Dolin, R.C.; Ortale, C. (EG and G Energy Measurements, Inc., Goleta, CA (USA). Santa Barbara Operations)

    1989-11-01

    A mercuric iodide (HgI{sub 2}) gamma ray imaging array and camera system previously described have been characterized for spatial and energy resolution. Based on these data a new camera is being developed to more fully exploit the potential of the array. Characterization results and design criteria for the new camera will be presented. (orig.).

  5. 21 CFR 184.1634 - Potassium iodide.

    Science.gov (United States)

    2010-04-01

    ... ingredient meets the specifications of the “Food Chemicals Codex,” 3d Ed. (1981), pp. 246-247, which is... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium iodide. 184.1634 Section 184.1634 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD...

  6. Iodide-trapping defect of the thyroid

    International Nuclear Information System (INIS)

    We describe a grossly hypothyroid 50-year-old woman, mentally retarded since birth. On the basis of her history of recurrent goitre, absence of 131I neck uptake and a low saliva/plasma 131I ratio, congenital hypothyroidism due to a defect of the iodide-trapping mechanism was diagnosed. Other family members studied did not have the defect

  7. Removal of cesium from wastewater: A cesium-specific ion exchange resin

    International Nuclear Information System (INIS)

    Researchers at the Savannah River Laboratory (SRL) have applied for a patent for an ion exchange resin that will remove cesium from water. Radioactive cesium-137 is a fission product of nuclear reactor operations. Cesium may enter the water of spent fuel holding basins through defects in fuel cladding. Control of cesium in these basins is desirable to keep personnel exposure to a minimum. Cesium is also present in the waste from reprocessing of defense nuclear reactor fuel. Research has been underway at SRL for over a decade to improve management of high-level reprocessing waste. The current technology separates the waste into soluble and insoluble components. Radioactive constituents are removed from the soluble component stream and combined with the insoluble components, which are then converted to a glass for long-term storage. Cesium is the most radioactive constituent of the soluble components stream. The SRL resin is a resorcinol-formaldehyde condensation polymer highly specific for cesium and is about 10 times more effective in removal of cesium than other ion exchange resins evaluated for use in processing defense nuclear waste. Tests have been run at SRL using both simulated and actual waste streams

  8. Effects of atomic hydrogen and deuterium exposure on high polarization GaAs photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    M. Baylac; P. Adderley; J. Brittian; J. Clark; T. Day; J. Grames; J. Hansknecht; M. Poelker; M. Stutzman; A. T. Wu; A. S. Terekhov

    2005-12-01

    Strained-layer GaAs and strained-superlattice GaAs photocathodes are used at Jefferson Laboratory to create high average current beams of highly spin-polarized electrons. High electron yield, or quantum efficiency (QE), is obtained only when the photocathode surface is atomically clean. For years, exposure to atomic hydrogen or deuterium has been the photocathode cleaning technique employed at Jefferson Laboratory. This work demonstrates that atomic hydrogen cleaning is not necessary when precautions are taken to ensure that clean photocathode material from the vendor is not inadvertently dirtied while samples are prepared for installation inside photoemission guns. Moreover, this work demonstrates that QE and beam polarization can be significantly reduced when clean high-polarization photocathode material is exposed to atomic hydrogen from an rf dissociator-style atomic hydrogen source. Surface analysis provides some insight into the mechanisms that degrade QE and polarization due to atomic hydrogen cleaning.

  9. Characterization of x-ray photocathode in transmission mode for imaging application

    International Nuclear Information System (INIS)

    The performance of an Al x-ray transmission photocathode was experimentally characterized by measuring the total electron yield from backsurface photocathodes of varying thickness. It was demonstrated that the backsurface electron yield is proportional to the x-ray photocurrent transmitted through the photocathode for thicknesses thicker than the optimum thickness. The optimum photocathode thickness with the highest conversion efficiency was found to be approximately 70 nm at 2.963 keV. An escape depth of the secondary electrons was determined to be approximately 13 nm from the yield-versus-thickness data fitted with a semiempirical equation. Using this parameter, the dependence of the optimum photocathode thickness on the x-ray energy was calculated for the 30-10000 eV range. As one example of imaging applications, different photoemission images in the transmission and reflection modes are also presented.

  10. A mechanism of Cu work function reduction in CsBr/Cu photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Halliday, Matthew T.; Hess, Wayne P.; Shluger, AL

    2016-03-14

    Thin films of CsBr deposited on Cu(100) have been proposed as next-generation photocathode materials for applications in particle accelerators and free-electron lasers. However, the mechanisms underlying an improved photocathode performance remain poorly understood. We present density Functional Theory (DFT) calculations of the work function reduction following the application of CsBr thin film coatings to Cu photocathodes. The effects of structure and van der Waals forces are examined. Calculations suggest that CsBr films can reduce the work function by around 1.5 eV, which would explain the exponential increase in quantum efficiency (QE) of coated vs. uncoated photocathodes. A model explaining experimentally observed laser activation of photocathode is provided whereby the photo-induced creation of di-vacancies at the surface, and their subsequent diffusion throughout the lattice and segregation at the interface leads to a further increase in QE after a period of laser irradiation.

  11. Cu-catalyzed trifluoromethylation of aryl iodides with trifluoromethylzinc reagent prepared in situ from trifluoromethyl iodide

    OpenAIRE

    Yuzo Nakamura; Motohiro Fujiu; Tatsuya Murase; Yoshimitsu Itoh; Hiroki Serizawa; Kohsuke Aikawa; Koichi Mikami

    2013-01-01

    The trifluoromethylation of aryl iodides catalyzed by copper(I) salt with trifluoromethylzinc reagent prepared in situ from trifluoromethyl iodide and Zn dust was accomplished. The catalytic reactions proceeded under mild reaction conditions, providing the corresponding aromatic trifluoromethylated products in moderate to high yields. The advantage of this method is that additives such as metal fluoride (MF), which are indispensable to activate silyl groups for transmetallation in the corresp...

  12. Pulse Selection Control for the IR FEL Photocathode Drive Laser

    Science.gov (United States)

    Jordan, K.; Evans, R.; Garza, O.; Hill, R.; Shinn, M.; Song, J.; Venhaus, D.

    1997-05-01

    The method for current control of the photocathode source is described. This device allows remote control of drive laser output pulses for resulting beam currents of less than 1 microamp to full current of 5 milliamps. The low current modes are accomplished by counting discrete micropulses and gating electro-optical cells. The higher current modes are done by varying both the photons per pulse and the frequency of the laser output pulses. Programmable Logic Devices (PLDs) provide the choice in micropulses per macropulse and the macropulse frequency. All macropulses are line locked to 60 Hz and have the ability to be slewed through a line cycle in discrete steps.

  13. A stabilised blue-violet LED for VPT photocathode evaluation

    CERN Document Server

    Hobson, Peter R

    2000-01-01

    A highly stable blue-violet light source ( peak wavelength 430 nm) based on the IPL 10630PAL self-monitoring LED is described. A thermoelectric cooler has been used to stabilise the 10630PAL device and the external LED current-control electronics to +- 0.1% K. The light intensity was measured to be stable to +- 0.03% for five hours, the repeatability was +- 0.1% The output spectrum of the LED is a good match to the scintillation emission of PbWO4, and this source will be used to evaluate the spatial and angular uniformity of VPT photocathodes for the endcap calorimeter.

  14. Ultra-low emittance X-band photocathode RF gun

    Institute of Scientific and Technical Information of China (English)

    TANG Chuan-Xiang; LIU Xiao-Han

    2009-01-01

    In this paper,we present the simulation results of a 1.6 cell X-band photocathode RF gun for ultra-low emittance electron beams.It will work at 9.3 GHz.The emittance,bunch length,electron energy and energy spread at the gun exit are optimized at bunch charge of 1pC using PARMELA.Electron bunches type coupler is adopted in this gun and an initial simulation by MAFIA is also given in this paper.

  15. Lasertron, a pulsed RF-source using laser triggered photocathode

    International Nuclear Information System (INIS)

    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)

  16. Nanosecond length electron pulses from a laser-excited photocathode

    International Nuclear Information System (INIS)

    A photocathode made from polycrystalline lanthanum hexaboride (LaB6) has produced nanosecond length electron pulses when excited by an excimer laser at 308nm. Peak currents in excess of 1A have been observed, with quantum yields of 4 x 10-5 being measured. A method for extracting the electrons from an emission-limited cathode, plasma extraction, has been demonstrated. This technique uses a low power continuous discharge to provide the electric field needed to extract the photoelectrons. This technique may be useful in producing high repetition rate short pulse ion sources. 10 refs., 4 figs

  17. Determining Of Iodide Concentration In Salt Using Iodide Ion Selective Electrode

    International Nuclear Information System (INIS)

    There are various studies about the determination of iodide or iodinate in table salt samples. Iodo metric method (5), spectrophotometric method(8), gravimetric method (2), chromatographic method (6), differential potentiometric method (3).But with ion selective electrode technicality the determination of iodide in geothermal water was only determined. So, in this work, the concentration of iodide in control table salt, iodinate table salt samples were determination, using iodide ion selective electrode . Iodide calibration graph was plotted according to the standard method, and the results of control salt samples which contain a defined concentration of iodide, and known amount of ionic strength adjustment buffer, were compatible with the assigned values. The linearity and sensitivity of method were studied, the results were 50 mg.L-1 and 0.2 mg.L-1 respectively . While, when the method applied on iodinate table salt samples which contain a amount concentration of potassium iodate (KIO3), the results were inconsistent. So, we had to convert the KIO3 to I-1 with oxidation - reduction reaction. By using convenient reduction in acidic medium . Iodate calibration graph was plotted according to the last standard method, and the results of control iodinate table salt samples were good with relative standard deviation was 3 %. (author)

  18. Polarization and charge limit studies of strained GaAs photocathodes

    International Nuclear Information System (INIS)

    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/cm2 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

  19. Transfer of the human sodium/iodide symporter gene enhances iodide uptake in melanoma cells

    International Nuclear Information System (INIS)

    Aim: Radioiodide therapy using 131I is effective for patients who have benign thyroid diseases or differentiated thyroid carcinoma. The transport of iodide across the cell membrane is mediated by the human sodium/iodide symporter (hNIS). To investigate the feasibility of 131I therapy for melanoma, we established melanoma cells stably expressing hNIS gene that can be modulated and studied in vivo and in vitro. Material and Methods: We transfected hNIS gene into a mouse melanoma cell line (B16) by electroporation. Iodide accumulation was assessed under various extracellular concentrations of sodium and iodide, and iodide efflux was also evaluated. Biodistribution and tumor imaging were studied using tumor-bearing mice. Results: We established a novel cell line B16-3 stably expressing the hNIS gene from B16. 125I uptake by B16-3 cells is between 6-17-fold that of B16 cells and 8-33-fold that of cell lines transduced with the eukaryotic expression vector pcDNA3 only. Iodide uptake was completely inhibited by 1mmol/L perchlorate and was dependent on external sodium and iodide concentrations. The velocity of iodide efflux from B16-3 cells was almost equal to that of FRTL-5 thyroid cells (T1/2 = 4min). In the biodistribution study using B16-3-xenografted mice, high tumor uptake of 131I was shown at 1 hour after injection, and tumor-to-normal tissue ratios were also high, except in the thyroid and stomach. However, the residual iodide in tumor lessened with time, reaching less than 3% at 24 h after injection. Conclusion: The transduction of he hNIS gene per se is sufficient to induce iodide transport in melanoma cells in vivo and in vitro. With regard to therapeutic application, however, further investigation is necessary to determine a method of maintaining radioiodide in the cells long enough to produce greater therapeutic effects

  20. Magnetron Driven L Band RF Gun using a Photocathode Emitter

    Science.gov (United States)

    Evans, Kirk; Fisher, Amnon; Friedman, Moshe

    1996-11-01

    Magnetron Driven L Band RF Gun using a Photocathode Emitter A tunable 5 megawatt L-Band injection locked magnetron amplifier is used to drive a 1-1/2 cell RF cavity gun, to produce a 2.5 megavolt electron beam. A tunable RF source relaxes the precision of the cavity gun construction, and therefore simplifies the design and reduces the overall cost. The design of the L-Band ( 1.3 GHz) RF cavity linear accelerator is presented, along with Superfish, SOS computer simulations, and calculations of beam energy and temporal qualities. Measurements of a few robust photocathode materials as well as measurements of the beam qualities of the final accelerator are presented. Future work will utilize new semiconductor laser diodes that can be electrically driven in the gigahertz range. This makes possible an electron gun system which can run at the RF frequency used to accelerate the electron beam. Such a system produces a "lock to clock" and synchronized RF and electron beam source which can be run single shot or any rep rate up to the RF frequency.

  1. 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.

  2. Radioactive cesium in Finnish mushrooms

    International Nuclear Information System (INIS)

    Surveillance of radioactive cesium in Finnish mushrooms was started in 1986 at STUK. Results of the surveillance programs carried out in Lapland and other parts of Finland are given in this report. More than 2000 samples of edible mushrooms have been analysed during 1986-2008. The 137Cs detected in the mushrooms mainly originates from the 137Cs deposition due to the accident at the Chernobyl nuclear power plant in 1986. The 137Cs concentrations of mushrooms in the end of 1970s and in the beginning of 1980s varied from some ten to two hundred becquerels per kilogram originating from the nuclear weapon test period. The uneven division of the Chernobyl fallout is seen in the areal variation of 137Cs concentrations of mushrooms, the 137Cs concentrations being about tenfold in the areas with the highest deposition compared to those where the deposition was lowest. After the Chernobyl accident the maximum values in the 137Cs concentrations were reached during 1987-88 among most species of mushrooms. The 137Cs concentrations have decreased slowly, being in 2008 about 40 per cent of the maximum values. The 137Cs concentrations may be tenfold in the mushroom species with high uptake of cesium (Rozites caperatus, Hygrophorus camarophyllus, Lactarius trivialis) compared to the species with low uptake (Albatrellus ovinus, Leccinum sp.) picked in the same area. The 137Cs contents in certain species of commercial mushrooms in Finland still exceed the maximum permitted level, 600 Bq/kg, recommended to be respected when placing wild game, wild berries, wild mushrooms and lake fish on the market (Commission recommendation 2003/274/Euratom). Therefore, the 137Cs concentrations of mushrooms should be measured before placing them on the market in the areas of the highest 137Cs deposition, except for Albatrellus ovinus, Boletus sp. and Cantharellus cibarius. The 137Cs concentrations of common commercial mushroom species, Cantharellus tubaeformis and Craterellus cornucopioides often

  3. Research on decontamination of cesium contaminated soil by electrokinetic process

    International Nuclear Information System (INIS)

    In this research, electrokinetic process was applied for the decontamination of cesium contaminated soil. As a result, about 4.0 times cesium removal was achieved by applying a DC electric field of 80 V/m to comparing zero electric field in treatment for 30 days. Therefore, the electrokinetic process has a possibility to decontamination of cesium contaminated soil. (author)

  4. Mercuric iodide X-ray camera

    Science.gov (United States)

    Patt, B. E.; del Duca, A.; Dolin, R.; Ortale, C.

    1986-02-01

    A prototype X-ray camera utilizing a 1.5- by 1.5-in., 1024-element, thin mercuric iodide detector array has been tested and evaluated. The microprocessor-based camera is portable and operates at room temperature. Events can be localized within 1-2 mm at energies below 60 keV and within 5-6 mm at energies on the order of 600 keV.

  5. Mercuric iodide x-ray camera

    International Nuclear Information System (INIS)

    A prototype x-ray camera utilizing a 1.5- by 1.5-in., 1024-element, thin mercuric iodide detector array has been tested and evaluated. The microprocessor-based camera is portable and operates at room temperature. Events can be localized within 1 to 2 mm at energies below 60 keV and within 5 to 6 mm at energies on the order of 600 keV. 5 refs., 7 figs

  6. Mercuric iodide X-ray camera

    Energy Technology Data Exchange (ETDEWEB)

    Patt, B.E.; Del Duca, A.; Dolin, R.; Ortale, C.

    1986-02-01

    A prototype x-ray camera utilizing a 1.5- by 1.5-inch, 1024-element, thin mercuric iodide detector array has been tested and evaluated. The microprocessor-based camera is portable and operates at room temperature. Events can be localized within 1-2 mm at energies below 60 keV and within 5-6 mm at energies on the order of 600 keV.

  7. Mercuric iodide x-ray camera

    Energy Technology Data Exchange (ETDEWEB)

    Patt, B.E.; Del Duca, A.; Dolin, R.; Ortale, C.

    1985-01-01

    A prototype x-ray camera utilizing a 1.5- by 1.5-in., 1024-element, thin mercuric iodide detector array has been tested and evaluated. The microprocessor-based camera is portable and operates at room temperature. Events can be localized within 1 to 2 mm at energies below 60 keV and within 5 to 6 mm at energies on the order of 600 keV. 5 refs., 7 figs.

  8. Mercuric iodide X-ray camera

    International Nuclear Information System (INIS)

    A prototype x-ray camera utilizing a 1.5- by 1.5-inch, 1024-element, thin mercuric iodide detector array has been tested and evaluated. The microprocessor-based camera is portable and operates at room temperature. Events can be localized within 1-2 mm at energies below 60 keV and within 5-6 mm at energies on the order of 600 keV

  9. Photocathode-Uniformity Tests of the Hamamatsu R5912 Photomultiplier Tubes Used in the Milagro Experiment

    Science.gov (United States)

    Vasileiou, V.; Ellsworth, R. W.; Smith, A.

    The Milagro experiment observes the extensive air showers produced by very high energy gamma-rays impacting the Earth’s atmosphere. Milagro uses 898 Hamamatsu R5912 Photomultiplier Tubes. To complete our Monte Carlo simulations, we tested the photocathode uniformity of our PMTs. The main finding was that the PMT gain and detection efficiency are a function of the distance from the center of the photocathode. Both quantities become considerably smaller as the illumination position nears the edge of the photocathode. Inclusion of the measured quantities in our MC simulations greatly increased the agreement between the simulations and the experiment.

  10. Sealed GEM photomultiplier with a CsI photocathode: ion feedback and ageing

    International Nuclear Information System (INIS)

    We present the performance of a sealed gaseous photomultiplier consisting of a cascade of 3 or 4 Gas Electron Multiplier (GEM) elements coupled to a semitransparent CsI photocathode, in Ar/CH4 (95/5). A few-month stability study of the photocathode in a sealed mode is presented. Increasing the number of GEMs in cascade substantially reduces the ageing of the detector under strong irradiation. The ion feedback to the photocathode has probably a minor effect on the ageing rate

  11. Performance of the 8-in. R5912 photomultiplier tube with super bialkali photocathode

    Science.gov (United States)

    Wang, W.; Qian, S.; Xia, J.; Ning, Z.; Cheng, Y.; Qi, M.; Heng, Y.; Wang, Z.; Li, X.; Liu, S.; Lei, X.

    2015-08-01

    An enhanced R5912 family photomultiplier (8-inch.) model with super bialkali photocathode was developed by Hamamatsu. The spectral responses of the standard and enhanced photocathode were compared and a relative increase of 39% at 400 nm was found for the enhanced one. Additional measurements on the relative detection efficiency at a gain of 1E7 showed a consistent improvement of the quantum efficiency. Good uniformity was observed on the super bialkali photocathode. Additional tests proved that both the charge resolution and time properties were not affected by the new cathode technology. Dark count rate and dark current values were found larger in the super bialkali model compared to the standard one.

  12. A new-type photocathode for polarized electron source with distributed bragg reflector

    International Nuclear Information System (INIS)

    In order to increase the quantum efficiency of the strained GaAs photocathode for the highly polarized electron source, we designed a new type photocathode with a distributed Bragg reflector(DBR). A Fabry-Perot cavity is formed by the DBR and the GaAs surface. The large enhancement of quantum efficiency was observed at the laser wavelength which satisfied the condition for the resonant absorption of incident laser light. From this experiment, it becomes promising to make the photocathode which has the quantum efficiency more than ∼1% together with the electron spin polarization higher than 80%. (author)

  13. Development of NEA-GaAs photocathode gun used for JAERI-FEL

    International Nuclear Information System (INIS)

    The photocathode DC-gun with high average current, low beam emittance and long operational lifetime is considered to be indispensable for ERL-FEL and X-FEL. We have started the developmental program of a electron gun with the NEA-GaAs photocathode for the first time in JAERI. In order to overcome an NEA lifetime problem, the JAERI electron gun system consists of an extreme high vacuum gun chamber and MBE apparatus, an electron source consists of a NEA-diamond film as enhancement electron current device and a superlattice photocathode. (author)

  14. Composition and properties of thallium mercury iodide

    Science.gov (United States)

    Kennedy, John H.; Schaupp, Christopher; Yang, Yuan; Zhang, Zhengming; Novinson, Thomas; Hoffard, Theresa

    1990-10-01

    Conflicting reports exist in the literature concerning the composition of thallium mercury iodide. Solid state synthesis with HgI 2 and TlI has been reported to give Tl 4HgI 6 while synthesis from solution has been reported to give Tl 2HgI 4. In this report we show that the "orange compound" precipitating from solution is actually a 1:1 mole ratio mixture of Tl 4HgI 6 and HgI 2. Pure Tl 4HgI 6, which is yellow, can be produced by heating the mixture at 100°C for several days to volatilize HgI 2 or more simply, by adding Tl(I) to a solution containing 2:1 KI:K 2HgI 4 to provide the additional iodide ions needed for Tl 4HgI 6. Tl 4HgI 6, unlike Ag 2HgI 4 and Cu 2HgI 4, has no sharp thermochromic changes and has no measurable ionic conductivity. This provides another example of the significant role the metal ion plans in determining structure and properties of metal mercury iodide compounds.

  15. Cesium ion uptake by moss (Hypnum cupressiforme)

    International Nuclear Information System (INIS)

    Lower land mosses uptake water and minerals from the atmosphere. They can collect metals polluting the air and radioactive fallout elements so they can be suitable for monitoring of these substances. Cesium ion uptake by Hypnum cupressiforme is studied by a radioactive tracer, 134Cs. The quantity of cesium ion in different celluar locations and the capacity of ion uptake is determined. The total capacity is found to be several times 10-3 mol g-1 and is therefore of the same order of magnitude as the cation exchange capacity of ion exchangers. The kinetics and reversibility of the process is studied as well. (orig.)

  16. Microbial accumulation of uranium, radium, and cesium

    International Nuclear Information System (INIS)

    Diverse microbial species varied considerably in their ability to accumulate uranium, cesium, and radium. Mechanistic differences in uranium uptake by Saccharomyces cerevisiae and Pseudomonas aeruginosa were indicated. S. serevisiae exhibited a slow (hours) surface accumulation of uranium which was subject to environmental factors, while P. aeruginosa accumulated uranium rapidly (minutes) as dense intracellular deposits and did not appear to be affected by environmental parameters. Metabolism was not required for uranium uptake by either organism. Cesium and radium were concentrated to a considerably lesser extent than uranium by the several species tested

  17. Environmental transfer of radio-cesium

    International Nuclear Information System (INIS)

    A large amount of Cs 134 and 137 were emitted from the destroyed reactors of Fukushima Daiichi Nuclear Power Station and deposited on the soil surface of vast area including forests, fields, and residential areas. The present report explains mainly land transfer behaviors of cesium which deposited on the surface soils, absorbed into soil particles as time passed on and finally became difficult to move from the particles (aging effect). Depth-distribution of radio-cesium in rice paddy and grassland as well as the change over years is presented. Changes with the passage of time of Cs 137 concentrations in leaves of spinach, wormwood, and persimmon are also provided. (S. Ohno)

  18. Crystalline silicotitanates for cesium/strontium removal

    Energy Technology Data Exchange (ETDEWEB)

    Brown, N.; Miller, J.; Sherman, J.

    1996-10-01

    A new class of inorganic ion exchangers called crystalline silicotitanates (CST) has been developed that exhibits very high selectivity for cesium and strontium in the highly alkaline radioactive wastes at the Hanford Site and other DOE sites. Tests have also shown that CSTs have high selectivity for cesium in acidic and neutral solutions. The ESP is supporting an effort at Sandia National Laboratories and Texas A & M University to further develop and characterize the important chemical and physical properties that will determine the applicability of CST to radioactive waste treatment at Hanford and other DOE facilities.

  19. Measurement of photocathode spectral response at cryogenic temperature

    Science.gov (United States)

    Menegolli, A.; Prata, M.; Prata, M. C.; Raselli, G. L.; Vignoli, C.

    2007-03-01

    Noble-gas liquids, such as xenon and argon, have been recently proposed as light scintillators in some experiments dedicated to neutrino physics and dark matter research. These experiments need the use of photomultiplier tubes directly immersed in the liquid phase and operating at cryogenic temperatures. We carried out an investigation about the spectral response and its variation from room to cryogenic temperature for two different kind of cryogenic photocathodes manufactured by Electron Tubes Ltd. and Hamamatsu Photonics K.K. Measurements were carried out by means of a xenon continuous lamp and a UV-VIS monocromator which allows the analysis from 300 to 700 nm with 5 nm resolution. Cryogenic tests were made at the liquid nitrogen temperature (77 K).

  20. Upgrade of a Photocathode RF Gun at SPring-8

    CERN Document Server

    Taniuchi, Tsutomu; Dewa, Hideki; Hanaki, Hirofumi; Kobayashi, Toshiaki; Mizuno, Akihiko; Suzuki, Shinsuke; Tomizawa, Hiromitsu; Yanagida, Kenichi

    2004-01-01

    The test bench of a photocathode RF gun at SPring-8 has been upgraded. The radiation shielded area was expanded about 3 times larger and the maximum beam energy was increased from up to 30 MeV including a 3-m long accelerating tube. The clean room for the drive laser system was newly built and the performance and reliability of the laser was improved. After the construction of the shielded room and set up of the components, the RF conditioning of the waveguides, the gun cavity and the accelerating tube was successfully performed and the beam characteristics such as the emittance and bunch length were measured. In this presentation, further plans for the improvement of the beam quality will also be presented.

  1. 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.

  2. An alkali dispenser photocathode (Al-Li)-Ag-O-Li

    International Nuclear Information System (INIS)

    We propose a new Li-actived metallic photocathode that could be used in high-current photo-injectors for linear accelerators. An Ag thin film is evaporated in UHV on the surface of a piece of (Al-Li) alloy. After treating at 380 deg C Li diffuses through Ag and decreases the surface work function to 2.7 eV. The emission yields Qe, in electrons per incident photon, are higher than those measured with (Al-Li) alone. Oxidation of the surface allows one to increase again Qe which reaches Qe∼1.7x10-3 for photon energies of 3.5 and 4.6 eV respectively (energies corresponding to photons delivered by a frequency triples -or quadruples- YAG laser)

  3. Design and construction of the photocathode electron gun cavity

    International Nuclear Information System (INIS)

    A 1300-MHz, two-cell rf accelerator cavity has been constructed for the high-brightness photocathode electron source program. Each cell has an rf drive. Cell 1 has a replacement photocathode plug on the back wall and has a shape designed for linear radial fields. Cell two has a more standard high-shunt-impedance shape. SUPERFISH values for shunt impedances are, respectively, 29.5 and 45.8 MΩ/m. Peak surface field maximums are 58.9 and 32.1 MV/m for an electron acceleration of 0.9 and 1.0 MeV. Drive coupling is matched for 55 and 86% beam loading at 1-A average current. The system has vacuum pumping ports, into both cells and is baked at 300 degree C. Typical operating pressures are in the low 10-10-torr range. Cell frequencies are fine tuned by a combination of operating temperature and cell nose pulling. Cell-to-cell coupling was intended to be low (K = 0.0002); however, because of the high Qs (13,300 and 20,000), substantial coupling effects are seen. Cutting the vacuum-port slots shifted the frequencies by 1.5 MHz and gave an apparent 10% increase in the cavity Qs. Construction of the cavity required a series of four brazes with several annealing cycles. All joints are flat, and the sequence is such that each joint is brazed horizontally; as a result, all joints were successfully brazed on the first attempt. The latest experiment measurements are given in another paper at this conference. 2 refs., 3 figs

  4. Ultrafast laser pulse heating of metallic photocathodes and its contribution to intrinsic emittance

    CERN Document Server

    Maxson, J; Cultrera, L; Karkare, S; Padmore, H

    2016-01-01

    The heating of the electronic distribution of a copper photocathode is calculated under the two-temperature model for ultrafast laser illumination with fluences typical for use in RF photoinjectors. Using the finite temperature-extended relations for the photocathode intrinsic emittance and quantum efficiency, the time-dependent emittance growth due to this laser heating is calculated. This laser heating is seen to limit the intrinsic emittance achievable for photoinjectors using short laser pulses and low quantum efficiency metal photocathodes. A pump-probe photocathode experiment in a standard 1.6 cell S-band gun is proposed, in which simulations show the time dependent thermal emittance modulation from the laser heating can persist for meters downstream and, in principle, be measured using a slice emittance diagnostic.

  5. Measurement of the quantum efficiency of CsI, amorphous silicon and organometallic reflective photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Malamud, G. (LPNHE, Ecole Polytechnique, IN2P3-CNRS, 91128 Palaiseau (France)); Mine, P. (LPNHE, Ecole Polytechnique, IN2P3-CNRS, 91128 Palaiseau (France)); Vartsky, D. (LPNHE, Ecole Polytechnique, IN2P3-CNRS, 91128 Palaiseau (France)); Equer, B. (PICM, Ecole Polytechnique, CNRS (UPR258), 91128 Palaiseau (France)); Besson, P. (CE Saclay, DAPNIA/SED, 91191 Gif-sur-Yvette Cedex (France)); Bourgeois, P. (CE Saclay, DAPNIA/SED, 91191 Gif-sur-Yvette Cedex (France)); Breskin, A. (LPNHE, Ecole Polytechnique, IN2P3-CNRS, 91128 Palaiseau (France)); Chechik, R. (The Weizmann Institute of Science, 76100 Rehovot (Israel))

    1994-09-01

    We performed a systematic investigation of the quantum efficiency of some solid reflective photocathodes in the spectral range 140-240 nm. The measurements were made without gaseous amplification in vacuum and in methane. No significant difference was found among CsI photocathodes prepared by vacuum deposition at different institutes, either from powders or from crystals of different origins, and measured either in vacuum or in methane. Amorphous silicon photocathodes were prepared by the plasma enhanced chemical vapor deposition technique. We present the results for several doping conditions of amorphous silicon and for p-n junctions. Some organometallic photocathodes, containing iron or other transition metals (cerium), were evaporated and measured. Among them decamethylferrocene exhibits the highest quantum efficiency in the range 190-240 nm. ((orig.))

  6. Measurement of Low Workfunction Cesiated Metals for Use in Dispenser Photocathodes

    CERN Document Server

    Moody, N A; O'Shea, P G

    2005-01-01

    Photoinjector performance is a limiting factor in the continued development of high powered FELs. Presently available photocathodes have 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 visible wavelengths, long lifetime in practical vacuum environments, and prompt emission. High efficiency cathodes typically have limited lifetime, 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 short lifetimes are overcome by periodic in situ regeneration that restores the photosensitive surface layer, analogous to methods used in the power tube industry. This work reports on the fabrication techniques and performance of cesiated metal photocathodes and cesiated dispenser cathodes, with a focus on understanding and improving quantum efficiency and lifetime, analyzing issues of emi...

  7. High-Efficiency GaN-Based UV Imaging Photocathodes for Application in Harsh Environments Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is directed toward the development of innovative high-efficiency UV photocathodes based on the wide bandgap III-nitride semiconductors for reliable...

  8. Cesium and Strontium Separation Technologies Literature Review

    Energy Technology Data Exchange (ETDEWEB)

    T. A. Todd; T. A. Todd; J. D. Law; R. S. Herbst

    2004-03-01

    Integral to the Advanced Fuel Cycle Initiative (AFCI) Program’s proposed closed nuclear fuel cycle, the fission products cesium and strontium in the dissolved spent nuclear fuel stream are to be separated and managed separately. A comprehensive literature survey is presented to identify cesium and strontium separation technologies that have the highest potential and to focus research and development efforts on these technologies. Removal of these high-heat-emitting fission products reduces the radiation fields in subsequent fuel cycle reprocessing streams and provides a significant short-term (100 yr) heat source reduction in the repository. This, along with separation of actinides, may provide a substantial future improvement in the amount of fuel that could be stored in a geologic repository. The survey and review of the candidate cesium and strontium separation technologies are presented herein. Because the AFCI program intends to manage cesium and strontium together, technologies that simultaneously separate both elements are of the greatest interest, relative to technologies that separate only one of the two elements.

  9. Anomalous wetting of helium on cesium

    International Nuclear Information System (INIS)

    The authors report studies of the anomalous wetting of a cesium substrate by a liquid helium film by means of the technique of third sound. A hysteretic pre-wetting transition is observed as a function of the amount of helium in the experimental cell. 10 refs., 2 figs

  10. Effect of nitrogen and oxygen on radiolysis of iodide solution

    Energy Technology Data Exchange (ETDEWEB)

    Karasawa, H.; Endo, M. [Hitachi Ltd., Power and Industrial System R+D Divisions, Ibaraki (Japan)

    1996-12-01

    The effect of nitrogen and oxygen on radiolysis of iodide solution was examined. Direct decomposition of nitrogen by {gamma}-radiation produced nitric acid to decrease a water pH. This resulted in the iodine formation in the radiolysis of iodide solution. Hydrogen peroxide was produced by the radiolysis of water containing oxygen. This worked a reducing agent to suppress the formation of iodine in the radiolysis of iodide solution. In the analytical model, fourteen iodine species were considered and reaction scheme consisted in 124 reactions. The analytical model could estimate the oxidation state of iodide ions. (author) 4 figs., 4 refs.

  11. Mercuric Iodide Anticoincidence Shield for Gamma-Ray Spectrometer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to utilize a new detector material, polycrystalline mercuric iodide, for background suppression by active anticoincidence shielding in gamma-ray...

  12. Mercuric Iodide Anticoincidence Shield for Gamma-Ray Spectrometer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We utilize a new detector material, polycrystalline mercuric iodide, for background suppression by active anticoincidence shielding in gamma-ray spectrometers. Two...

  13. Downramp-assisted underdense photocathode electron bunch generation in plasma wakefield accelerators

    OpenAIRE

    Knetsch, Alexander; Karger, Oliver; Wittig, Georg; Groth, Henning; Xi, Yunfeng; Deng, Aihua; Rosenzweig, James Benjamin; Bruhwiler, David Leslie; Smith, Johnathan; Jaroszynski, Dino Anthony; Sheng, Zheng-Ming; Manahan, Grace Gloria; Xia, Guoxing; Jamison, Steven; Hidding, Bernhard

    2014-01-01

    It is shown that the requirements for high quality electron bunch generation and trapping from an underdense photocathode in plasma wakefield accelerators can be substantially relaxed through localizing it on a plasma density downramp. This depresses the phase velocity of the accelerating electric field until the generated electrons are in phase, allowing for trapping in shallow trapping potentials. As a consequence the underdense photocathode technique is applicable by a much larger number o...

  14. Downramp-assisted underdense photocathode electron bunch generation in plasma wakefield accelerators

    CERN Document Server

    Knetsch, Alexander; Wittig, Georg; Groth, Henning; Xi, Yunfeng; Deng, Aihua; Rosenzweig, James Benjamin; Bruhwiler, David Leslie; Smith, Johnathan; Jaroszynski, Dino Anthony; Sheng, Zheng-Ming; Manahan, Grace Gloria; Xia, Guoxing; Jamison, Steven; Hidding, Bernhard

    2014-01-01

    It is shown that the requirements for high quality electron bunch generation and trapping from an underdense photocathode in plasma wakefield accelerators can be substantially relaxed through localizing it on a plasma density downramp. This depresses the phase velocity of the accelerating electric field until the generated electrons are in phase, allowing for trapping in shallow trapping potentials. As a consequence the underdense photocathode technique is applicable by a much larger number of accelerator facilities. Furthermore, dark current generation is effectively suppressed.

  15. Development of new photocathode materials and its quantum efficiency improvement for high brightness electron gun

    International Nuclear Information System (INIS)

    New photocathode material is being developed for high charge electron guns. We succeeded in developing an iridium cerium (Ir5Ce) photocathode and Cu:C12A7 electride photocathode. The iridium cerium photocathode has a reasonably high QE (∼9.1×10-4 (a)213nm at room temperature) and long lifetime (> LaB6). Furthermore, the QE of Ir5Ce photocathode was increased to a maximum value of 2.70×10-3 by heating at 1006°C. These great advantages of Ir5Ce photocathode led to generate the electron beams with a maximum charge of 4.4 nC/bunch using a new-type RF gun at a test bench of KEK electron linac. Cu:C12A7 is originally an electrical insulator. Cu:C12A7, however exhibits an excellent electrical conductivity and low work function (≈2.5 eV) after a reduction process at 1100°C for 48 hours using a titanium powder. Finally, we found that Cu:C12A7 electride has a QE of 8.72×10-4 (a)213nm at 600°C. (author)

  16. Tritium and iodide diffusion through opalinus clay

    International Nuclear Information System (INIS)

    The International Mont Terri Project started in 1995 under the patronage of the Swiss National Hydrological and Geological Survey (SNHGS), and has the authorization of the Republique et Canton du Jura. The underground rock laboratory is located at the northwestern part of Switzerland (Canton Jura), in and beside the reconnaissance gallery of the Mont Terri motorway tunnel, one of the several tunnels of the A16 'Transjurane' motorway. The depth of overburden above the rock laboratory is approximately 300 meters. The project is aimed to investigate the geological, hydrogeological, geochemical and rock mechanical properties of the Opalinus Clay for assessing the feasibility and safety of a repository for radioactive waste placed in this type of host rock. One of the issues under study is radionuclide migration by diffusion through clays. As a part of this investigation, an interlaboratory comparison on small-scale diffusion experiments was carried out by three research laboratories: AEA Technology (UK), SCK-CEN (Belgium) and CIEMAT (Spain). The radionuclides investigated were tritium and iodine. This paper concerns to the methodological approach and results of the experiments undertaken by CIEMAT. The effective diffusion coefficients were measured for tritiated water and iodine (as Γ), resulting larger for tritium [(1.7±0.4)x10-11 m2/s] than for iodide [(2.7±0.3)x10-12 m2/s]. The porosity available for diffusion was calculated by using the time-lag method, but some results seemed unrealistic and showed a large variability. In general, tritium exhibited higher values of porosity than iodide (17 to 26% and 12 to 17%, respectively), which were consistent with the anion exclusion affecting the distribution of iodide into the clay pores. Copyright (2001) Material Research Society

  17. Transfer of the human sodium/iodide symporter gene enhances iodide uptake in melanoma cells

    International Nuclear Information System (INIS)

    Objective: To obtain human sodium/iodide symporter (hNIS) cDNA and to study its biological property and potential use as a therapeutic radioiodide for melanoma. Methods: hNIS gene cDNA was amplified with total RNA from human thyroid tissue by RT-PCR. The hNIS cDNA was inserted into cloning vector pUCm-T and subcloned into eukaryotic expression vector pcDNA3. The recombinant plasmid pcDNA3-hNIS was introduced into B16 cells using the electroporation technique. The uptake and efflux of iodide was examined in vitro. Results: The cloned hNIS cDNA sequence was identical to the published sequence. Two novel cell lines named B16-A containing hNIS and B16-B containing pcDNA3 only were established. The resultant cell line B16-A accumulated 17 and 19 times more radioiodide in vitro than B16 and B16-B did, respectively. However the efflux of iodide from B16-A was also rapid ( T1/2=10 min). Conclusions: Our preliminary data indicate that the transduction of the hNIS gene per se is sufficient to induce iodide transport in melanoma cells in vitro, but its T1/2 is short. With regard to therapeutic application, however, further investigation is necessary so as to develop a method of maintaining more radioiodide in the cells for long enough to produce greater therapeutic effects

  18. Taming the Reactivity of Glycosyl Iodides To Achieve Stereoselective Glycosidation.

    Science.gov (United States)

    Gervay-Hague, Jacquelyn

    2016-01-19

    Although glycosyl iodides have been known for more than 100 years, it was not until the 21st century that their full potential began to be harnessed for complex glycoconjugate synthesis. Mechanistic studies in the late 1990s probed glycosyl iodide formation by NMR spectroscopy and revealed important reactivity features embedded in protecting-group stereoelectronics. Differentially protected sugars having an anomeric acetate were reacted with trimethylsilyl iodide (TMSI) to generate the glycosyl iodides. In the absence of C-2 participation, generation of the glycosyl iodide proceeded by inversion of the starting anomeric acetate stereochemistry. Once formed, the glycosyl iodide readily underwent in situ anomerization, and in the presence of excess iodide, equilibrium concentrations of α- and β-iodides were established. Reactivity profiles depended upon the identity of the sugar and the protecting groups adorning it. Consistent with the modern idea of disarmed versus armed sugars, ester protecting groups diminished the reactivity of glycosyl iodides and ether protecting groups enhanced the reactivity. Thus, acetylated sugars were slower to form the iodide and anomerize than their benzylated analogues, and these disarmed glycosyl iodides could be isolated and purified, whereas armed ether-protected iodides could only be generated and reacted in situ. All other things being equal, the β-iodide was orders of magnitude more reactive than the thermodynamically more stable α-iodide, consistent with the idea of in situ anomerization introduced by Lemieux in the mid-20th century. Glycosyl iodides are far more reactive than the corresponding bromides, and with the increased reactivity comes increased stereocontrol, particularly when forming α-linked linear and branched oligosaccharides. Reactions with per-O-silylated glycosyl iodides are especially useful for the synthesis of α-linked glycoconjugates. Silyl ether protecting groups make the glycosyl iodide so reactive

  19. Production of Molecular Iodine and Tri-iodide in the Frozen Solution of Iodide: Implication for Polar Atmosphere.

    Science.gov (United States)

    Kim, Kitae; Yabushita, Akihiro; Okumura, Masanori; Saiz-Lopez, Alfonso; Cuevas, Carlos A; Blaszczak-Boxe, Christopher S; Min, Dae Wi; Yoon, Ho-Il; Choi, Wonyong

    2016-02-01

    The chemistry of reactive halogens in the polar atmosphere plays important roles in ozone and mercury depletion events, oxidizing capacity, and dimethylsulfide oxidation to form cloud-condensation nuclei. Among halogen species, the sources and emission mechanisms of inorganic iodine compounds in the polar boundary layer remain unknown. Here, we demonstrate that the production of tri-iodide (I3(-)) via iodide oxidation, which is negligible in aqueous solution, is significantly accelerated in frozen solution, both in the presence and the absence of solar irradiation. Field experiments carried out in the Antarctic region (King George Island, 62°13'S, 58°47'W) also showed that the generation of tri-iodide via solar photo-oxidation was enhanced when iodide was added to various ice media. The emission of gaseous I2 from the irradiated frozen solution of iodide to the gas phase was detected by using cavity ring-down spectroscopy, which was observed both in the frozen state at 253 K and after thawing the ice at 298 K. The accelerated (photo-)oxidation of iodide and the subsequent formation of tri-iodide and I2 in ice appear to be related with the freeze concentration of iodide and dissolved O2 trapped in the ice crystal grain boundaries. We propose that an accelerated abiotic transformation of iodide to gaseous I2 in ice media provides a previously unrecognized formation pathway of active iodine species in the polar atmosphere. PMID:26745029

  20. Composition and process for separating cesium ions from an acidic aqueous solution also containing other ions

    Science.gov (United States)

    Dietz, M.L.; Horwitz, E.P.; Bartsch, R.A.; Barrans, R.E. Jr.; Rausch, D.

    1999-03-30

    A crown ether cesium ion extractant is disclosed as is its synthesis. The crown ether cesium ion extractant is useful for the selective purification of cesium ions from aqueous acidic media, and more particularly useful for the isolation of radioactive cesium-137 from nuclear waste streams. Processes for isolating cesium ions from aqueous acidic media using the crown ether cesium extractant are disclosed as are processes for recycling the crown ether cesium extractant and processes for recovering cesium from a crown ether cesium extractant solution. 4 figs.

  1. Recent developments in thick mercuric iodide spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    Hull, K.; Beyerle, A.; Lopez, B.; Markakis, J.; Ortale, C.; Schnepple, W.; van den Berg, L.

    1982-01-01

    Thick (approx. 1 cm) mercuric iodide gamma-ray detectors have been produced which show spectroscopic qualities at moderate detector biases (approx. 5 kV) comparable to those of thin spectrometers. Efficiency measurements indicate that the entire volume of the detectors is active. Spectra resolutions of less than 10% have been obtained for gamma-ray energies above 1 MeV. Short charge collection times have produced the best results. Measurement of crystal charge transport properties is discussed. A small amount of bias conditioning is necessary for best performance. Operating parameters of the detectors have been investigated.

  2. Large-area mercuric iodide photodectors

    Science.gov (United States)

    Markakis, J.; Ortale, C.; Schnepple, W.; Iwanczyk, J.; Dabrowski, A.

    1983-07-01

    The limits of the active area of mercuric iodide photodetectors imposed by the size of available crystals, electronic noise, and the uniformity of charge carrier collection are discussed. Theoretical calculations of the photodetector electronic noise are compared with the experimental results. Different entrance contacts were studied including semitransparent palladium films and conductive liquids. HgI2 photodetectors with active area up to 4 sq cm are matched with NaI(Tl) and CsI(Tl) scintillation crystals and are evaluated as gamma radiation spectrometers.

  3. Large-area mercuric iodide photodetectors

    Energy Technology Data Exchange (ETDEWEB)

    Markakis, J.; Ortale, C.; Schnepple, W.; Iwanczyk, J.; Dabrowski, A.

    1983-01-01

    This article discusses the limits of the active area of mercuric iodide photodetectors imposed by the size of available crystals, electronic noise, and the uniformity of charge carrier collection. Theoretical calculations of the photodetector electronic noise are compared with the experimental results. Different entrance contacts were studied including semitransparent palladium films and conductive liquids. HgI/sub 2/ photodetectors with active area up to 4 sq cm are matched with NaI(Tl) and CsI(Tl) scintillation crystals and are evaluated as gamma radiation spectrometers.

  4. The addition of iodine to tetramethylammonium iodide

    Science.gov (United States)

    Foote, H.W.; Fleischer, M.

    1953-01-01

    The system tetramethylammonium iodide-iodine-toluene has been studied by the solubility method at 6 and at 25??. The compounds (CH3)4NI3, (CH3)4NI5 and (CH3)4NI11 were found to be stable phases at both temperatures. In addition, the compound (CH3)4NI10 was found at 6?? and the compound (CH3)4NI9 at 25??. The dissociation pressures of the compounds at these temperatures were calculated from the solubility data.

  5. Novel mercuric iodide polycrystalline nuclear particles counters

    Energy Technology Data Exchange (ETDEWEB)

    Schieber, M. [Hebrew Univ. of Jerusalem (Israel)]|[Sandia National Lab., Livermore, CA (United States); Zuck, A.; Braiman, M.; Nissenbaum, J. [Hebrew Univ. of Jerusalem (Israel)] [and others

    1996-12-31

    Polycrystalline mercuric iodide nuclear radiation detectors having areas between 0.01 to 100 cm{sup 2} and thicknesses 30 to 600 microns, have been fabricated with single, linear strip and square pixel contact. The large area detectors 10 to 600 cm{sup 2} were produced by industrial ceramic equipment while the smaller ones, about 1 cm{sup 2} area, were produced in the laboratory. The large detectors still had large leakage currents and the production process is being revised. The smaller detectors were tested and their response to lower and higher gamma energy, beta and even 100 GeV muons at CERN will be reported.

  6. Novel mercuric iodide polycrystalline nuclear particles counters

    International Nuclear Information System (INIS)

    Polycrystalline mercuric iodide nuclear radiation detectors having areas between 0.01 to 100 cm2 and thicknesses 30 to 600 microns, have been fabricated with single, linear strip and square pixel contact. The large area detectors 10 to 600 cm2 were produced by industrial ceramic equipment while the smaller ones, about 1 cm2 area, were produced in the laboratory. The large detectors still had large leakage currents and the production process is being revised. The smaller detectors were tested and their response to lower and higher gamma energy, beta and even 100 GeV muons at CERN will be reported

  7. Large-area mercuric iodide photodetectors

    International Nuclear Information System (INIS)

    This article discusses the limits of the active area of mercuric iodide photodetectors imposed by the size of available crystals, electronic noise, and the uniformity of charge carrier collection. Theoretical calculations of the photodetector electronic noise are compared with the experimental results. Different entrance contacts were studied including semitransparent palladium films and conductive liquids. HgI2 photodetectors with active area up to 4 sq cm are matched with NaI(Tl) and CsI(Tl) scintillation crystals and are evaluated as gamma radiation spectrometers

  8. Electronic and optical properties of lead iodide

    DEFF Research Database (Denmark)

    Ahuja, R.; Arwin, H.; Ferreira da Silva, A.;

    2002-01-01

    The electronic properties and the optical absorption of lead iodide (PbI2) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI2 has been recognized as a very promising...... detector material with a large technological applicability. Its band-gap energy as a function of temperature has also been measured by optical absorption. The temperature dependence has been fitted by two different relations, and a discussion of these fittings is given. ©2002 American Institute of Physics....

  9. Phase 2 Methyl Iodide Deep-Bed Adsorption Tests

    Energy Technology Data Exchange (ETDEWEB)

    Soelberg, Nick [Idaho National Lab. (INL), Idaho Falls, ID (United States); Watson, Tony [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-09-01

    Nuclear fission produces fission products (FPs) and activation products, including iodine-129, which could evolve into used fuel reprocessing facility off-gas systems, and could require off-gas control to limit air emissions to levels within acceptable emission limits. Research, demonstrations, and some reprocessing plant experience have indicated that diatomic iodine can be captured with efficiencies high enough to meet regulatory requirements. Research on the capture of organic iodides has also been performed, but to a lesser extent. Several questions remain open regarding the capture of iodine bound in organic compounds. Deep-bed methyl iodide adsorption testing has progressed according to a multi-laboratory methyl iodide adsorption test plan. This report summarizes the second phase of methyl iodide adsorption work performed according to this test plan using the deep-bed iodine adsorption test system at the Idaho National Laboratory (INL), performed during the second half of Fiscal Year (FY) 2014. Test results continue to show that methyl iodide adsorption using AgZ can achieve total iodine decontamination factors (DFs, ratios of uncontrolled and controlled total iodine levels) above 1,000, until breakthrough occurred. However, mass transfer zone depths are deeper for methyl iodide adsorption compared to diatomic iodine (I2) adsorption. Methyl iodide DFs for the Ag Aerogel test adsorption efficiencies were less than 1,000, and the methyl iodide mass transfer zone depth exceeded 8 inches. Additional deep-bed testing and analyses are recommended to (a) expand the data base for methyl iodide adsorption under various conditions specified in the methyl iodide test plan, and (b) provide more data for evaluating organic iodide reactions and reaction byproducts for different potential adsorption conditions.

  10. Direct observation of bi-alkali antimonide photocathodes growth via in operando x-ray diffraction studies

    OpenAIRE

    M. Ruiz-Osés; Schubert, S.; Attenkofer, K.; Ben-Zvi, I.; Liang, X; Muller, E; Padmore, H; Rao, T.; T. Vecchione; Wong, J; Xie, J.; Smedley, J.

    2014-01-01

    Alkali antimonides have a long history as visible-light-sensitive photocathodes. This work focuses on the process of fabrication of the bi-alkali photocathodes, K2CsSb. In-situ synchrotron x-ray diffraction and photoresponse measurements were used to monitor phase evolution during sequential photocathode growth mode on Si(100) substrates. The amorphous-to-crystalline transition for the initial antimony layer was observed at a film thickness of 40 Å . The antimony crystalline structure dissolv...

  11. 21 CFR 520.763 - Dithiazanine iodide oral dosage forms.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Dithiazanine iodide oral dosage forms. 520.763 Section 520.763 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Dithiazanine iodide oral dosage forms....

  12. Experimental research on performance of gaseous methyl iodide removal

    International Nuclear Information System (INIS)

    Under the circumstance of gaseous methyl iodide removal process in containment venting system, taking the deionized water and alkalescent sodium thiosulphate as absorber, the experimental researches on the performance of gaseous methyl iodide removal were carried out at different solution temperatures and concentrations. And the effects of two types of mechanisms, namely mass transfer and chemical reaction, on gaseous methyl iodide removal process were analyzed based on the experimental results. The research results show that at room temperature, the mass transfer mechanism plays a dominant role in gaseous methyl iodide removal process through the absorption of alkalescent sodium thiosulphate solution. Thus, the slow chemical reaction rate is the major factor that limits gaseous methyl iodide removal efficiency. With temperature increasing, the effect of chemical reaction is constantly enhanced in the methyl iodide removal process. However, the gas absorption process will get into an insensitive region when the reaction rate reaches to a certain point and the continuously enhancing chemical reaction rate will not greatly influence the removal efficiency. At that point, mass transfer performance becomes the major factor that limits gaseous methyl iodide removal process. The efficiency of gaseous methyl iodide removal can be further improved by necessary means of enhancing mass transfer process through increasing contact surface and so on. (authors)

  13. Dissolution of gaseous methyl iodide into aqueous sodium hydroxide solutions

    International Nuclear Information System (INIS)

    Absorption process of gaseous methyl iodide by water or sodium hydroxide solutions was investigated using a semi-flow type experimental apparatus by measuring the concentration of all measurable chemical species in both the gas and the liquid phase. The experimental temperature ranged from 288 to 311 K and the gaseous methyl iodide and aqueous sodium hydroxide concentrations were approximately 0.6 x 10-3 to 7 x 10-3 and 0 to 0.2 mol/dm3, respectively. It is estimated that the dissolution of methyl iodide into the sodium hydroxide solution proceeds according to the following steps. Step (1) Methyl iodide in air dissolves physically into the aqueous phase. Physical dissolution process obeys Henry's law. Step (2) Methyl iodide dissolved into the aqueous phase is decomposed by a base catalytic hydrolysis and produces methyl alcohol and iodide ion. The equilibrium constants of physical dissolution were obtained from the steady concentration in both the gas and the liquid phases in the semi-flow type experiment because the hydrolysis reaction rate of methyl iodide is very slow in comparison with the physical dissolution in this experimental conditions. The obtained value of the standard heat of solution of methyl iodide into water was 7.2 kcal/mol. Salting-out effect was observed when the concentration of sodium hydroxide in the absorbent was over 0.01 mol/dm3. (auth.)

  14. Iodide sensing via electrochemical etching of ultrathin gold films

    International Nuclear Information System (INIS)

    Iodide is an essential element for humans and animals and insufficient intake is still a major problem. Affordable and accurate methods are required to quantify iodide concentrations in biological and environmental fluids. A simple and low cost sensing device is presented which is based on iodide induced electrochemical etching of ultrathin gold films. The sensitivity of resistance measurements to film thickness changes is increased by using films with a thickness smaller than the electron mean free path. The underlying mechanism is demonstrated by simultaneous cyclic voltammetry experiments and resistance change measurements in a buffer solution. Iodide sensing is conducted in buffer solutions as well as in lake water with limits of detection in the range of 1 μM (127 μg L−1) and 2 μM (254 μg L−1), respectively. In addition, nanoholes embedded in the thin films are tested for suitability of optical iodide sensing based on localized surface plasmon resonance. (paper)

  15. Strontium-90 and cesium-137 in milk

    International Nuclear Information System (INIS)

    The milk samples have been collected from 30 prefectures by prefectural public health laboratories and institutes (raw milk: 4 times per year for the report to WHO, and raw and city milk: 2 times per year), and analysed for strontium-90 and cesium-137 content at Japan Chemical Analysis Center. Collected samples were the raw milk and the city ones for the producing districts and the consuming ones, respectively. Three liters of fresh milk were carbonized in each prefectural public health laboratories and institutes, and then it was asked at Japan Chemical Analysis Center. The ask to which both some carriers and hydrochloric acid were added, was destroyed under heating. The nuclides was dissolved into hydrochloric acid and filtrated, after it was added with nitric acid and heated to dryness. The filtrate was radiochemically analysed for strontium-90 and cesium-137 using the method recommended by Science and Technology Agency. (author)

  16. Cesium stress and adaptation in pseudomonas fluorescens

    International Nuclear Information System (INIS)

    Industrialization and acid rain have led to a marked increment on the bioavailability of numerous metals. These metallic pollutants pose a serious threat to the ecosystem due to their ability to interact negatively with living organisms. Thus, considerable effort has been directed towards the development of environmentally-friendly technologies tailored to the management of metal wastes. As microbes are known to adapt to most environmental stresses, they constitute organisms of choice in the study of molecular adaptation processes. The adaptive features may be subsequently engineered for biotechnological applications. Cesium, a monovalent metal with chemical similarities to potassium but no know essential biological function has become a cause of environmental concern owing to its accidental release from the Chernobyl nuclear accident. This study examines the impact of cesium on the soil microbe Pseudomonas fluorescensts, and discusses the possibilities of its use in management of this nuclear waste. 15 refs., 3 figs

  17. Thermochemical evaluation and preparation of cesium uranates

    International Nuclear Information System (INIS)

    Two kinds of cesium uranates, Cs2UO4 and Cs2U2O7, which are predicted by thermochemical estimation to be formed in irradiated oxide fuels, were prepared from U3O8 and Cs2CO3 for measurements of the thermal expansions and thermal conductivities. In advance of the preparation, thermochemical calculations for the formation and decomposition of these cesium uranates were performed by Gibbs free energy minimizer. The preparation temperatures for Cs2UO4 and Cs2U2O7 were determined from the results of the thermochemical calculations. The prepared samples were analyzed by X-ray diffraction, which showed that the single phases of Cs2UO4 and Cs2U2O7 were formed. Thermogravimetry and differential thermal analysis were also performed on these samples, and the decomposition temperatures were evaluated. The experimental results were in good agreement with those of the thermochemical calculations. (author)

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

    International Nuclear Information System (INIS)

    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)

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

    Science.gov (United States)

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

    2012-03-01

    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.

  20. Surface science analysis of GaAs photocathodes following sustained electron beam delivery

    Energy Technology Data Exchange (ETDEWEB)

    Carlos Hernandez-Garcia, Fay Hannon, Marcy Stutzman, V. Shutthanandan, Z. Zhu, M. Nandasri, S. V. Kuchibhatla, S. Thevuthasan, W. P. Hess

    2012-06-01

    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 (QE) degradation is due to residual gasses 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 (HIM), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) 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 shows 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.

  1. Cesium legacy safety project management work plan

    International Nuclear Information System (INIS)

    This Management Work Plan (MWP) describes the process flow, quality assurance controls, and the Environment, Safety, and Health requirements of the Cesium Legacy Safety Project. This MWP provides an overview of the project goals and methods for repackaging the non-conforming Type W overpacks and packaging the CsCl powder and pellets. This MWP is not intended to apply to other activities associated with the CsCl Legacy Safety Program (i.e., clean out of South Cell)

  2. Murine immunization by cesium-137 irradiation attenuated Schistosoma mansoni cercariae

    International Nuclear Information System (INIS)

    Cesium-137, becoming a more readily available ionizing gamma radiation source for laboratory use, was shown to effectively attenuate Schistosoma mansoni cercariae for vaccine production. In parallel comparison studies with the murine model, cesium-137 attenuated cercariae consistently afforded better protection than did the cobalt-60 prepared vaccine. Dose-response data indicated that the optimal total irradiation with cesium-137 was between 45 and 50 Krad

  3. Murine immunization by cesium-137 irradiation attenuated Schistosoma mansoni cercariae

    Energy Technology Data Exchange (ETDEWEB)

    Stek, M. Jr.; Minard, P.; Cruess, D.F.

    1984-06-01

    Cesium-137, becoming a more readily available ionizing gamma radiation source for laboratory use, was shown to effectively attenuate Schistosoma mansoni cercariae for vaccine production. In parallel comparison studies with the murine model, cesium-137 attenuated cercariae consistently afforded better protection than did the cobalt-60 prepared vaccine. Dose-response data indicated that the optimal total irradiation with cesium-137 was between 45 and 50 Krad.

  4. Sorption of cesium 137 by steel from sodium melt

    International Nuclear Information System (INIS)

    Sorption of cesium-137 radionuclide by Kh18N10T steel from sodium melt at different temperatures (150-450 deg C) has been studied. Equilibrium coefficients of cesium distribution between sodium and steel are determined, which depend on the conditions of sorption realization, such as cesium concentration in sodium melt, the content of oxygen admixture in sodium and the state of sorbing surface

  5. Cesium-137 as a radiation source

    International Nuclear Information System (INIS)

    The U.S. Department of Energy (DOE) Byproducts Utilization Program (BUP) seeks to develop and encourage widespread commercial use of defense byproducts that are produced by DOE. Cesium-l37 is one such byproduct that is radioactive and decays with emission of gamma rays. The beneficial use of this radiation to disinfect sewage sludge or disinfest food commodities is actively being pursued by the program. The radiation produced by cesium-l37(Cs-l37) is identical in form to that produced by cobalt-60(Co-60), an isotope that is widely used in commercial applications such as medical product sterilization. The choice of isotope to use depends on several factors ranging from inherent properties of the isotopes to availability and cost. The BUP, although centrally concerned with the beneficial use of Cs-l37, by investigating and assessing the feasibility of various uses hopes to define appropriate circumstances where cesium or cobalt might best be used to accomplish specific objectives. This paper discusses some of the factors that should be considered when evaluating potential uses for isotopic sources

  6. Removal of cesium from red deer meat

    International Nuclear Information System (INIS)

    The effect was studied of marinading on the reduction of cesium radionuclide activity in red deer meat contaminated by ingestion of feed containing 134Cs+137Cs from radioactive fallout following the Chernobyl accident. Two types of marinade were studied, viz., a vinegar infusion and a vinegar infusion with an addition of vegetables and spices. The meat was chopped to cubes of about 1.5 cm in size and the marinading process took place at temperatures of 5 and 11 degC. The drop of cesium content in the meat was determined by gamma spectrometry at given time intervals. The replacement of the marinade and the duration of the process were found to maximally affect efficiency. If the solution was not replaced, about 80% of cesium radionuclides were removed after seven hours of marinading. With one replacement of the infusion the drop in 134Cs+137Cs radioactivity amounted to up to 90% after seven hours of marinading. No effects were shown of vegetable additions to the vinegar infusion and of the change in temperature from 5 to 11 degC on the efficiency of the process. (author). 3 tabs., 6 refs

  7. Beyond injection: Trojan horse underdense photocathode plasma wakefield acceleration

    International Nuclear Information System (INIS)

    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.

  8. 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...

  9. Gain of a gas photomultiplier with CsI photocathode

    International Nuclear Information System (INIS)

    A Gas PMT with the CsI photocathode was fabricated as a phototube of a glass vessel identical to a conventional vacuum PMT. A GEM and a Micromegas were installed in the phototube of the Gas PMT. The Gas PMT was operated with two different gas mixtures, Ar (90%) + CH4 (10%) and Ne (90%) + CF4 (10%), at the gas pressure of 1 atm. The gain of 105 was obtained for both the gas mixtures. It was found that the gain of the Gas PMT can be described using the Townsend ionization coefficient for the Micromegas. The imaging capability of the Ne gas mixture was checked by an optical imaging capillary (CP) gas detector, using X-ray beams. The image of an X-ray resolution chart indicates that the imaging resolution is determined by the diameter of the capillary, here 100 μm. The Ne gas mixture appropriate to the Gas PMT is well suited for a fine imaging detector

  10. Superlattice Photocathodes for Accelerator-Based Polarized Electron Source Applications

    International Nuclear Information System (INIS)

    A major improvement in the performance of the SLC was achieved with the introduction of thin strained-layer semiconductor crystals. After some optimization, polarizations of 75-85% became standard with lifetimes that were equal to or better than that of thick unstrained crystals. Other accelerators of polarized electrons, generally operating with a much higher duty factor, have now successfully utilized similar photocathodes. For future colliders, the principal remaining problem is the limit on the total charge that can be extracted in a time scale of 10 to 100 ns. In addition, higher polarization is critical for exploring new physics, especially supersymmetry. However, it appears that strained-layer crystals have reached the limit of their optimization. Today strained superlattice crystals are the most promising candidates for better performance. The individual layers of the superlattice can be designed to be below the critical thickness for strain relaxation, thus in principle improving the polarization. Thin layers also promote high electron conduction to the surface. In addition the potential barriers at the surface for both emission of conduction-band electrons to vacuum and for tunneling of valence-band holes to the surface can be significantly less than for single strained-layer crystals, thus enhancing both the yield at any intensity and also decreasing the limitations on the total charge. The inviting properties of the recently developed AlInGaAs/GaAs strained superlattice with minimal barriers in the conduction band are discussed in detail

  11. Characteristics of test cavity for cryogenic photocathode RF-gun

    International Nuclear Information System (INIS)

    The cryogenic C-band photocathode RF-gun operating at 20 K is under development at LEBRA in Nihon University. The RF-gun is of the BNL-type 2.6-cell pillbox cavity with the resonant frequency of 5712 MHz. The 6N8 high purity OFC copper (corresponding to RRR-3000) is used as the cavity material. From the theoretical evaluation of the anomalous skin effect, the quality factor Q of the cavity at the operating temperature of 20K has been expected to be approximately 60000. Considering a low cooling capacity of the cryogenic system, initial operation of the RF gun is assumed at a duty factor of 0.01%. The cavity basic design and the beam bunching simulation were carried out using Poisson Superfish and General Particle Tracer (GPT). Machining and diffusion bonding of the cavity was carried out in KEK. The Q0 value of the π-mode resonance at the room temperature (23.5°C) deduced from the Smith chart was approximately 11440 after diffusion bonding. (author)

  12. Designs for waveguide and structured photocathodes with high quantum efficiency

    International Nuclear Information System (INIS)

    Conventional S20 multialkali photocathodes have a wide wavelength coverage from 850 nm, but their high transparency and the surface work function result in low quantum efficiencies at longer wavelengths. Theoretical modelling of the photon and excited electron interactions that define the cathode performance provides a realistic prediction of the measured response. The theory emphasizes that the basic light absorption is strongly sensitive to the cathode thickness, wavelength, polarization and incident angle. Parameters can be selected which predict that even at long wavelengths (e.g. 900 nm), absorption may be increased from ∼1% to ∼100%. Cathode topographies can be designed to exploit these responses and offer increased absorption at the longer wavelengths. Alternative designs, which include waveguiding of light within the cathode window, or in structured surfaces, can similarly lead to almost total absorption of the incident light by increasing the number of interactions. These concepts of optimal incidence and waveguiding have been both theoretically modelled and demonstrated in newly fabricated cathode designs. The methods have variously reached quantum efficiencies in excess of 50% at wavelengths in the range from 200 to > 750 nm under different operational conditions. The improvement factors relative to normal incidence on planar cathodes increase for longer wavelengths, and examples of 20-50 times by ∼900 nm were noted. Whilst the absolute S20 efficiency values at long wavelengths are still small, the improvements offer a usable sensitivity even beyond 1 μm, as demonstrated by spectroscopy data up to at least 1140 nm

  13. 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.

  14. Surface interactions of cesium and boric acid with stainless steel

    International Nuclear Information System (INIS)

    In this report, the effects of cesium hydroxide and boric acid on oxidized stainless steel surfaces at high temperatures and near one atmosphere of pressure are investigated. This is the first experimental investigation of this chemical system. The experimental investigations were performed using a mass spectrometer and a mass electrobalance. Surfaces from the different experiments were examined using a scanning electron microscope to identify the presence of deposited species, and electron spectroscopy for chemical analysis to identify the species deposited on the surface. A better understanding of the equilibrium thermodynamics, the kinetics of the steam-accelerated volatilizations, and the release kinetics are gained by these experiments. The release rate is characterized by bulk vaporization/gas-phase mass transfer data. The analysis couples vaporization, deposition, and desorption of the compounds formed by cesium hydroxide and boric acid under conditions similar to what is expected during certain nuclear reactor accidents. This study shows that cesium deposits on an oxidized stainless steel surface at temperatures between 1000 and 1200 Kelvin. Cesium also deposits on stainless steel surfaces coated with boric oxide in the same temperature ranges. The mechanism for cesium deposition onto the oxide layer was found to involve the chemical reaction between cesium and chromate. Some revaporization in the cesium hydroxide-boric acid system was observed. It has been found that under the conditions given, boric acid will react with cesium hydroxide to form cesium metaborate. A model is proposed for this chemical reaction

  15. Distribution and retention of cesium in Swedish boreal forest ecosystems

    International Nuclear Information System (INIS)

    The retention and distribution of cesium in forest environments are being studied at three locations in Sweden. The main part of the cesium found in the soil was recovered in horizons rich in organic matter. The cesium was retained in the soil organic matter in a more or less extractable form. As different soil types have a different distribution pattern of organic matter the distribution of cesium will depend on the forest soil type. The clay content in Swedish forest soils is in general low which will mitigate the retention of cesium in the soil mineral horizons. The cesium present in the tree was considered to be an effect of assimilation by the tissues in the canopy as well as by the roots. The redistribution of cesium within the trees was extensive which was considered to be an effect of a high mobility of cesium in the close system of a forest environment. The cesium will remain in the forest environment for a considerable time but can be removed by forest practice, by leaching out of the soil profile or by the radioactive decay. (au)

  16. Lanthanide doped strontium-barium cesium halide scintillators

    Science.gov (United States)

    Bizarri, Gregory; Bourret-Courchesne, Edith; Derenzo, Stephen E.; Borade, Ramesh B.; Gundiah, Gautam; Yan, Zewu; Hanrahan, Stephen M.; Chaudhry, Anurag; Canning, Andrew

    2015-06-09

    The present invention provides for a composition comprising an inorganic scintillator comprising an optionally lanthanide-doped strontium-barium, optionally cesium, halide, useful for detecting nuclear material.

  17. Study of silicon tip photocathodes in DC and RF photo-injectors; Etude de photocathodes a pointe de silicium dans des canons continus et hyperfrequence

    Energy Technology Data Exchange (ETDEWEB)

    Jaber, Zakaria [Lab. de Physique Corpusculaire, Clermont-Ferrand-2 Univ., 63 - Aubiere (France)

    1999-02-02

    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)

  18. Conserved charged amino acid residues in the extracellular region of sodium/iodide symporter are critical for iodide transport activity

    Directory of Open Access Journals (Sweden)

    Liang Ji-An

    2010-11-01

    Full Text Available Abstract Background Sodium/iodide symporter (NIS mediates the active transport and accumulation of iodide from the blood into the thyroid gland. His-226 located in the extracellular region of NIS has been demonstrated to be critical for iodide transport in our previous study. The conserved charged amino acid residues in the extracellular region of NIS were therefore characterized in this study. Methods Fourteen charged residues (Arg-9, Glu-79, Arg-82, Lys-86, Asp-163, His-226, Arg-228, Asp-233, Asp-237, Arg-239, Arg-241, Asp-311, Asp-322, and Asp-331 were replaced by alanine. Iodide uptake abilities of mutants were evaluated by steady-state and kinetic analysis. The three-dimensional comparative protein structure of NIS was further modeled using sodium/glucose transporter as the reference protein. Results All the NIS mutants were expressed normally in the cells and targeted correctly to the plasma membrane. However, these mutants, except R9A, displayed severe defects on the iodide uptake. Further kinetic analysis revealed that mutations at conserved positively charged amino acid residues in the extracellular region of NIS led to decrease NIS-mediated iodide uptake activity by reducing the maximal rate of iodide transport, while mutations at conserved negatively charged residues led to decrease iodide transport by increasing dissociation between NIS mutants and iodide. Conclusions This is the first report characterizing thoroughly the functional significance of conserved charged amino acid residues in the extracellular region of NIS. Our data suggested that conserved charged amino acid residues, except Arg-9, in the extracellular region of NIS were critical for iodide transport.

  19. Sorption of cesium in intact rock

    Energy Technology Data Exchange (ETDEWEB)

    Puukko, E. [Univ. of Helsinki, Dept. of Chemistry (Finland)

    2014-04-15

    The mass distribution coefficient K{sub d} is used in performance assessment (PA) to describe sorption of a radionuclide on rock. The R{sub d} is determined using crushed rock which causes uncertainty in converting the R{sub d} values to K{sub d} values for intact rock. This work describes a method to determine the equilibrium of sorption on intact rock. The rock types of the planned Olkiluoto waste disposal site were T-series mica gneiss (T-MGN), T-series tonalite granodiorite granite gneiss (T-TGG), P-series tonalite granodiorite granite gneiss (P-TGG) and pegmatitic granite (PGR). These rocks contain different amount of biotite which is the main sorbing mineral. The sorption of cesium on intact rock slices was studied by applying an electrical field to speed up migration of cesium into the rock. Cesium is in the solution as a noncomplex cation Cs{sup +} and it is sorbed by ion exchange. The tracer used in the experiments was {sup 134}Cs. The experimental sorption on the intact rock is compared with values calculated using the in house cation exchange sorption model (HYRL model) in PHREEQC program. The observed sorption on T-MGN and T-TGG rocks was close to the calculated values. Two PGR samples were from a depth of 70 m and three samples were from a depth of 150 m. Cesium sorbed more than predicted on the two 70 m PGR samples. The sorption of Cs on the three 150 m PGR samples was small which was consistent with the calculations. The pegmatitic granite PGR has the smallest content of biotite of the four rock types. In the case of P-TGG rock the observed values of sorption were only half of the calculated values. Two kind of slices were cut from P-TGG drill core. The slices were against and to the direction of the foliation of the biotite rims. The sorption of cesium on P-TGG rock was same in both cases. The results indicated that there was no effect of the directions of the electric field and the foliation of biotite in the P-TGG rock. (orig.)

  20. Design of quantum efficiency measurement system for variable doping GaAs photocathode

    Science.gov (United States)

    Chen, Liang; Yang, Kai; Liu, HongLin; Chang, Benkang

    2008-03-01

    To achieve high quantum efficiency and good stability has been a main direction to develop GaAs photocathode recently. Through early research, we proved that variable doping structure is executable and practical, and has great potential. In order to optimize variable doping GaAs photocathode preparation techniques and study the variable doping theory deeply, a real-time quantum efficiency measurement system for GaAs Photocathode has been designed. The system uses FPGA (Field-programmable gate array) device, and high speed A/D converter to design a high signal noise ratio and high speed data acquisition card. ARM (Advanced RISC Machines) core processor s3c2410 and real-time embedded system are used to obtain and show measurement results. The measurement precision of photocurrent could reach 1nA, and measurement range of spectral response curve is within 400~1000nm. GaAs photocathode preparation process can be real-time monitored by using this system. This system could easily be added other functions to show the physic variation of photocathode during the preparation process more roundly in the future.

  1. Carrier traps and transport in mercuric iodide

    Science.gov (United States)

    Schlesinger, T. E.; Bao, X. J.; James, R. B.; Cheng, A. Y.; Ortale, C.; van den Berg, L.

    1992-11-01

    Thermally stimulated current spectroscopy (TSC) was performed on a variety of mercuric iodide samples and detectors to determine the nature and origin of deep traps in this material. It is shown that the trap type and concentration is a function of the metal overlayer employed as a contact material. The energy barrier height as well as the type (electron or hole) of barrier at the metal/semiconductor interface has also been determined by internal photoemission measurements. When polarization effects are not present, as is the case in most Pd contacted samples, the barrier height can be accurately determined by this technique. A value of 1.05 eV was measured for a hole barrier at the Pd/Hgl 2 interface.

  2. Ferroelastic Fingerprints in Methylammonium Lead Iodide Perovskite

    KAUST Repository

    Hermes, Ilka M.

    2016-02-12

    Methylammonium lead iodide (MAPbI3) perovskite materials show an outstanding performance in photovoltaic devices. However, certain material properties, especially the possible ferroic behavior, remain unclear. We observed distinct nanoscale periodic domains in the piezoresponse of MAPbI3(Cl) grains. The structure and the orientation of these striped domains indicate ferroelasticity as their origin. By correlating vertical and lateral piezoresponse force microscopy experiments performed at different sample orientations with x-ray diffraction, the preferred domain orientation was suggested to be the a1-a2-phase. The observation of these ferroelastic fingerprints appears to strongly depend on the film texture and thus the preparation route. The formation of the ferroelastic twin domains could be induced by internal strain during the cubic-tetragonal phase transition.

  3. Photoluminescence studies of impurities and defects in mercuric iodide

    International Nuclear Information System (INIS)

    The authors have studied the effects of chemical etching in potassium iodide(KI) aqueous solution, vacuum exposure and bulk heating on the photoluminescence(PL) spectra of mercuric iodide(HgI2). Different contact materials deposited onto HgI2 were also investigated, such as Pd, Cu, Al, Ni, Sn, In, Ag and Ta. These processing steps and the choice of a suitable electrode material are very important in the manufacturing of high-quality mercuric iodide nuclear detectors. Comparisons are made between the front surface photoluminescence and transmission photoluminescence spectra

  4. Expression of the human sodium/iodide symporter (hNIS) in xenotransplanted human thyroid carcinoma

    NARCIS (Netherlands)

    Smit, J.W.A.; Schröder - van der Elst, J.P.; Karperien, M.; Que, I.; Romijn, J.A.; Heide, van der D.

    2001-01-01

    The uptake of iodide in thyroid epithelial cells is mediated by the sodium/iodide symporter (NIS). The uptake of iodide is of vital importance for thyroid physiology and is a prerequisite for radioiodine therapy in thyroid cancer. Loss of iodide uptake due to diminished expression of the human NIS (

  5. Characterizing and Optimizing Photocathode Laser Distributions for Ultra-low Emittance Electron Beam Operations

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, F. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Bohler, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ding, Y. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Gilevich, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Huang, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Loos, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ratner, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Vetter, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-12-07

    Photocathode RF gun has been widely used for generation of high-brightness electron beams for many different applications. We found that the drive laser distributions in such RF guns play important roles in minimizing the electron beam emittance. Characterizing the laser distributions with measurable parameters and optimizing beam emittance versus the laser distribution parameters in both spatial and temporal directions are highly desired for high-brightness electron beam operation. In this paper, we report systematic measurements and simulations of emittance dependence on the measurable parameters represented for spatial and temporal laser distributions at the photocathode RF gun systems of Linac Coherent Light Source. The tolerable parameter ranges for photocathode drive laser distributions in both directions are presented for ultra-low emittance beam operations.

  6. Significant Broadband Photocurrent Enhancement by Au-CZTS Core-Shell Nanostructured Photocathodes

    Science.gov (United States)

    Zhang, Xuemei; Wu, Xu; Centeno, Anthony; Ryan, Mary P.; Alford, Neil M.; Riley, D. Jason; Xie, Fang

    2016-03-01

    Copper zinc tin sulfide (CZTS) is a promising material for harvesting solar energy due to its abundance and non-toxicity. However, its poor performance hinders their wide application. In this paper gold (Au) nanoparticles are successfully incorporated into CZTS to form Au@CZTS core-shell nanostructures. The photocathode of Au@CZTS nanostructures exhibits enhanced optical absorption characteristics and improved incident photon-to-current efficiency (IPCE) performance. It is demonstrated that using this photocathode there is a significant increase of the power conversion efficiency (PCE) of a photoelectrochemical solar cell of 100% compared to using a CZTS without Au core. More importantly, the PCE of Au@CZTS photocathode improved by 15.8% compared to standard platinum (Pt) counter electrode. The increased efficiency is attributed to plasmon resonance energy transfer (PRET) between the Au nanoparticle core and the CZTS shell at wavelengths shorter than the localized surface plasmon resonance (LSPR) peak of the Au and the semiconductor bandgap.

  7. Temporal resolution limit estimation of x-ray streak cameras using a CsI photocathode

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiang; Gu, Li; Zong, Fangke; Zhang, Jingjin; Yang, Qinlao, E-mail: qlyang@szu.edu.cn [Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Institute of Optoelectronics, Shenzhen University, Shenzhen 518060 (China)

    2015-08-28

    A Monte Carlo model is developed and implemented to calculate the characteristics of x-ray induced secondary electron (SE) emission from a CsI photocathode used in an x-ray streak camera. Time distributions of emitted SEs are investigated with an incident x-ray energy range from 1 to 30 keV and a CsI thickness range from 100 to 1000 nm. Simulation results indicate that SE time distribution curves have little dependence on the incident x-ray energy and CsI thickness. The calculated time dispersion within the CsI photocathode is about 70 fs, which should be the temporal resolution limit of x-ray streak cameras that use CsI as the photocathode material.

  8. Impact evaluation of ion back-bombardment of NEA-GaAs photocathode

    International Nuclear Information System (INIS)

    We study GaAs photocathode with NEA (Negative Electron Affinity) surface as electron source of accelerator. Advantage of NEA GaAs photocathode is generating ultra-low emittance and polarized electron beam with circularly polarized laser. However, the cathode is so sensitive and quantum efficiency degradation limits the operational lifetime. Among several processes, Ion Back-bombardment (IBB) is the most serious phenomenon to limit the lifetime. In IBB, ions generated by ionization of residual gas molecule with electron beam collide to cathode and degrade NEA surface. We improve photocathode test bench in Hiroshima University to prevent vacuum pressure evolution during the experiment and control ion orbits to switch the IBB effect. In this study, we simulate ion orbits and evaluate distribution of ion collision on cathode to switch the IBB in on cathode. With this modification, IBB effect on the cathode lifetime will be evaluated more quantitatively. (author)

  9. 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.

  10. Photoelectrochemical water splitting: silicon photocathodes for hydrogen evolution

    Science.gov (United States)

    Warren, Emily L.; Boettcher, Shannon W.; McKone, James R.; Lewis, Nathan S.

    2010-08-01

    The development of low cost, scalable, renewable energy technologies is one of today's most pressing scientific challenges. We report on progress towards the development of a photoelectrochemical water-splitting system that will use sunlight and water as the inputs to produce renewable hydrogen with oxygen as a by-product. This system is based on the design principle of incorporating two separate, photosensitive inorganic semiconductor/liquid junctions to collectively generate the 1.7-1.9 V at open circuit needed to support both the oxidation of H2O (or OH-) and the reduction of H+ (or H2O). Si microwire arrays are a promising photocathode material because the high aspect-ratio electrode architecture allows for the use of low cost, earth-abundant materials without sacrificing energy-conversion efficiency, due to the orthogonalization of light absorption and charge-carrier collection. Additionally, the high surfacearea design of the rod-based semiconductor array inherently lowers the flux of charge carriers over the rod array surface relative to the projected geometric surface of the photoelectrode, thus lowering the photocurrent density at the solid/liquid junction and thereby relaxing the demands on the activity (and cost) of any electrocatalysts. Arrays of Si microwires grown using the Vapor Liquid Solid (VLS) mechanism have been shown to have desirable electronic light absorption properties. We have demonstrated that these arrays can be coated with earth-abundant metallic catalysts and used for photoelectrochemical production of hydrogen. This development is a step towards the demonstration of a complete artificial photosynthetic system, composed of only inexpensive, earth-abundant materials, that is simultaneously efficient, durable, and scalable.

  11. The Effect on Sodium/Iodide Symporter and Pendrin in Thyroid Colloid Retention Developed by Excess Iodide Intake.

    Science.gov (United States)

    Chen, Xiao-Yi; Lin, Chu-Hui; Yang, Li-Hua; Li, Wang-Gen; Zhang, Jin-Wei; Zheng, Wen-Wei; Wang, Xiang; Qian, Jiang; Huang, Jia-Luan; Lei, Yi-Xiong

    2016-07-01

    It is well known that excess iodide can lead to thyroid colloid retention, a classic characteristic of iodide-induced goiter. However, the mechanism has not been fully unrevealed. Iodide plays an important role in thyroid function at multiple steps of thyroid colloid synthesis and transport among which sodium/iodide symporter (NIS) and pendrin are essential. In our study, we fed female BALB/c mice with different concentrations of high-iodine water including group A (control group, 0 μg/L), group B (1500 μg/L), group C (3000 μg/L), group D (6000 μg/L), and group E (12,000 μg/L). After 7 months of feeding, we found that excess iodide could lead to different degrees of thyroid colloid retention. Besides, NIS and pendrin expression were downregulated in the highest dose group. The thyroid iodide intake function detected by urine iodine assay and thyroidal (125)I experiments showed that the urine level of iodine increased, while the iodine intake rate decreased when the concentration of iodide used in feeding water increased (all p control group). In addition, transmission electron microscopy (TEM) indicated a reduction in the number of intracellular mitochondria of thyroid cells. Based on these findings, we concluded that the occurrence of thyroid colloid retention exacerbated by excess iodide was associated with the suppression of NIS and pendrin expression, providing an additional insight of the potential mechanism of action of excess iodide on thyroid gland. PMID:26660892

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

    International Nuclear Information System (INIS)

    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.

  13. Distillation device supplies cesium vapor at constant pressure

    Science.gov (United States)

    Basiulis, A.; Shefsiek, P. K.

    1968-01-01

    Distillation apparatus in the form of a U tube supplies small amounts of pure cesium vapor at constant pressure to a thermionic converter. The upstream leg of the U tube is connected to a vacuum pump to withdraw noncondensable impurities, the bottom portion serves as a reservoir for the liquid cesium.

  14. First results of the two-phase argon avalanche detector performance with CsI photocathode

    OpenAIRE

    Bondar, A.(Budker Institute of Nuclear Physics (SB RAS), Novosibirsk State University, Novosibirsk, Russia); Buzulutskov, A.; Grebenuk, A.; Pavlyuchenko, D.; Snopkov, R.; Tikhonov, Y.

    2007-01-01

    The performance of a two-phase Ar avalanche detector with CsI photocathode was studied, with regard to potential application in coherent neutrino-nucleus scattering and dark matter search experiments. The detector comprised a 1 cm thick liquid Ar layer and a triple-GEM multiplier operated in the saturated vapor above the liquid phase; the CsI photocathode was deposited on the first GEM. Successful detection of both primary scintillation and ionization signals, produced by beta-particles in li...

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

    Institute of Scientific and Technical Information of China (English)

    NIU Jun; YANG Zhi; CHANG Ben-Kang

    2009-01-01

    The mathematical expression of the electron diffusion and drift length LDE of exponential doping photocathode is deduced. In the quantum efficiency equation of the reflection-mode uniform doping cathode, substituting L_(DE) for L_D, the equivalent quantum efficiency equation of the reflection-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 fine.The equivalent equation avoids complicated calculation, thereby simplifies the process of solving the quantum efficiency of exponential doping photocathode.

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

    International Nuclear Information System (INIS)

    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

  17. CdTeO3 Deposited Mesoporous NiO Photocathode for a Solar Cell

    OpenAIRE

    Chuan Zhao; Xiaoping Zou; Sheng He

    2014-01-01

    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 s...

  18. Development of modulated electron beam for intensity modulated radiation therapy (IMRT) on a photocathode electron gun

    International Nuclear Information System (INIS)

    Radiation therapy of cancer is developing to un-uniform irradiation, for concentrating dose to a cancer tumor and reducing dose to normal tissue. As a step toward the Intensity modulated radiation therapy, we examined dynamic optical modulation of electron beam produced by a photocathode electron gun. Images on photo-masks were transferred onto a photocathode by relay imaging. Electron beam could be controlled by a remote mirror. Modulated electron beam maintained its shape on acceleration, had a fine spatial resolution, and could be moved dynamically by optical methods. As a second step, optical modulation of electron beam and dynamic control succeeded by a digital micro mirror device (DMD). (author)

  19. Design of a high duty cycle, asymmetric emittance RF photocathode injector for linear collider applications

    International Nuclear Information System (INIS)

    One of the attractive features of the superconducting approach to linear collider design is that the transverse emittances demanded are much larger than in normal conducting schemes. For TESLA design parameters, the damping rings appear to be relatively large and expensive, and it is therefore of some interest to look into alternative sources. For electrons, a promising source candidate is an rf photocathode. In this paper, the authors present conceptual design work towards development of an asymmetric emittance rf photocathode source which can operate at the TESLA repetition rates and duty cycle, and is capable of emitting beams with the required emittances and charge per pulse

  20. Structural transformation of CsI thin film photocathodes under exposure to air and UV irradiation

    CERN Document Server

    Tremsin, A S; Siegmund, O H W

    2000-01-01

    Transmission electron microscopy has been employed to study the structure of polycrystalline CsI thin films and its transformation under exposure to humid air and UV irradiation. The catastrophic degradation of CsI thin film photocathode performance is shown to be associated with the film dissolving followed by its re-crystallization. This results in the formation of large lumps of CsI crystal on the substrate surface, so that the film becomes discontinuous and its performance as a photocathode is permanently degraded. No change in the surface morphology and the film crystalline structure was observed after the samples were UV irradiated.

  1. Measurement of temporal response of transmission-type spin-polarized photocathodes

    International Nuclear Information System (INIS)

    Spin polarized electron beam is essential for the high energy particle physics experiment 'International Linear Collider'. In Nagoya University, transmission-type spin-polarized photocathodes, in which the laser light is injected from the back side of the photocathode have been developed. In the development of the electron source, the quantum efficiency of 0.5% and the polarization of ∼90% were achieved. However, the response time of the transmission-type electron source is not evaluated. We are planning to measure the response time by using a RF deflecting cavity. In this paper, the details of the measurement system are reported. (author)

  2. Design and beam dynamics simulations of an S-band photocathode rf gun

    Science.gov (United States)

    Kumar, Arvind; Pant, K. K.; Krishnagopal, S.

    2002-10-01

    We are building an S-band photocathode rf gun as an injector to a 30MeV electron linac for FEL applications. Here we discuss details of design simulations performed using superfish and gdfidl and compare with results of cold tests performed on prototype cells of the photocathode rf gun. We also discuss beam dynamics simulations performed using parmela and report results from simulations to achieve a normalized transverse rms emittance of about 1π mm mrad for a 10ps pulse with 1nC charge in the presence of a solenoid magnetic field used for emittance compensation.

  3. Compact narrow-band THz radiation source based on photocathode rf gun

    International Nuclear Information System (INIS)

    Narrow-band THz coherent Cherenkov radiation can be driven by a subpicosecond electron bunch traveling along the axis of a hollow cylindrical dielectric-lined waveguide. We present a scheme of compact THz radiation source based on the photocathode rf gun. On the basis of our analytic result, the subpicosecond electron bunch with high charge (800 pC) can be generated directly in the photocathode rf gun. According to the analytical and simulated results, a narrow emission spectrum peaked at 0.24 THz with 2 megawatt (MW) peak power is expected to gain in the proposed scheme (the length of the facility is about 1.2 m). (authors)

  4. 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.

  5. Ion and electron thermoemission of cesium alumosilicates

    International Nuclear Information System (INIS)

    Relationships between and electron thermoemission of cesium aluminosilicate were studied. Measurements were made at 5.10-8-5.10-9 Tor and temperatures up to 1400 deg C. The effect of additions refractory metals Ti, Mo, Cu and Ir was studied. Ion thermoemission in the pulse regime was also studied. Conclusions are drawn that capacity depends upon additions. The temperature dependence of thermoionic emission current has two maxima and is characterized by instability in time. A conclusion is drawn that aluminosilicate thermionic cathodes can be reckoned as cathodes of a film type

  6. Cesium-137 in grass from Chernobyl fallout

    International Nuclear Information System (INIS)

    Grass ecosystem was monitored for 137Cs, a relatively long-lived radionuclide, for about 16 years since the Chernobyl reactor accident occurred on April 26, 1986. Cesium-137 in grass gramineae or poaceae the species, ranged from 122.9 Bq kg-1 (September 4, 1986) to 5.8 mBq kg-1 (October 16, 2001) that is a range of five orders of magnitude. It was observed that there was a trend of decreasing 137Cs with time reflecting a removal half-time of 40 months (3 1/3 years), which is the ecological half-life, T ec of 137Cs in grassland

  7. Plutonium and Cesium Colloid Mediated Transport

    Science.gov (United States)

    Boukhalfa, H.; Dittrich, T.; Reimus, P. W.; Ware, D.; Erdmann, B.; Wasserman, N. L.; Abdel-Fattah, A. I.

    2013-12-01

    Plutonium and cesium have been released to the environment at many different locations worldwide and are present in spent fuel at significant levels. Accurate understanding of the mechanisms that control their fate and transport in the environment is important for the management of contaminated sites, for forensic applications, and for the development of robust repositories for the disposal of spent nuclear fuel and nuclear waste. Plutonium, which can be present in the environment in multiple oxidations states and various chemical forms including amorphous oxy(hydr)oxide phases, adsorbs/adheres very strongly to geological materials and is usually immobile in all its chemical forms. However, when associated with natural colloids, it has the potential to migrate significant distances from its point of release. Like plutonium, cesium is not very mobile and tends to remain adhered to geological materials near its release point, although its transport can be enhanced by natural colloids. However, the reactivity of plutonium and cesium are very different, so their colloid-mediated transport might be significantly different in subsurface environments. In this study, we performed controlled experiments in two identically-prepared columns; one dedicated to Pu and natural colloid transport experiments, and the other to Cs and colloid experiments. Multiple flow-through experiments were conducted in each column, with the effluent solutions being collected and re-injected into the same column two times to examine the persistence and scaling behavior of the natural colloids, Pu and Cs. The data show that that a significant fraction of colloids were retained in the first elution through each column, but the eluted colloids collected from the first run transported almost conservatively in subsequent runs. Plutonium transport tracked natural colloids in the first run but deviated from the transport of natural colloids in the second and third runs. Cesium transport tracked natural

  8. Extraction of radioactive cesium from ash of flammable radioactive material

    International Nuclear Information System (INIS)

    Huge amount of radioactive materials was released by the hydrogen explosion at Fukushima Daiichi Nuclear Power Plant due to the Great East Japan Earthquake on March 11, 2011. Suppression of the volume of radioactive materials stored by decontamination works is strongly required since the preparation of storage places is not easy. We are developing the technology for separation and concentration of radioactive cesium using nano-particle, Prussian blue, as a cesium adsorption material which has a high efficiency and good selectivity. We propose a method in which radioactive cesium is extracted from the ash of flammable materials into the water and the Prussian blue nano-particles are added to the water to collect cesium. The volume of radioactive wastes contaminated by cesium is expected to be cut down with these processes. (J.P.N.)

  9. Evaluation of electrochemical ion exchange for cesium elution

    International Nuclear Information System (INIS)

    Electrochemical elution was investigated as an alternative method to acid elution for the desorption of cesium from loaded ion exchange resins. The approach was found to have several potential advantages over existing technologies, in particular, electrochemical elution eliminates the need for addition of chemicals to elute cesium from the ion exchange resin. Also, since, in the electrochemical elution process the eluting solution is not in direct contact with the ion exchange material, very small volumes of the eluting solution can be used in a complete recycle mode in order to minimize the total volume of the cesium elute. In addition, the cesium is eluted as an alkaline solution that does not require neutralization with caustic to meet the tank farm specifications. Other advantages include easy incorporation of the electrochemical elution process into the present cesium recovery schemes

  10. A combined cesium-strontium extraction/recovery process

    International Nuclear Information System (INIS)

    A new solvent extraction process for the simultaneous extraction of cesium and strontium from acidic nitrate media is described. This process uses a solvent formulation comprised of 0.05 M di-t-butylcyclohexano-18-crown-6 (DtBuCH18C6), 0.1 M Crown 100' (a proprietary, cesium-selective derivative of dibenzo-18-crown-6), 1.2 M tributyl phosphate (TBP), and 5% (v/v) lauryl nitrile in an isoparaffinic hydrocarbon diluent. Distribution ratios for cesium and strontium from 4 M nitric acid are 4.13 and 3.46, respectively. A benchtop batch countercurrent extraction experiment indicates that >98% of the cesium and strontium initially present in the feed solution can be removed in only four extraction stages. Through proper choice of extraction and strip conditions, extracted cesium and strontium can be recovered either together or individually

  11. Preparation and evaluation of mercuric iodide for crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, N.L.; Ortale, C.; Schieber, M.M.

    1988-01-01

    Large quantities, on the order of several hundred, of consistent, high quality mercuric iodide for crystal growth have not been commercially available. The hydrocarbon, anion, and cation impurity levels varied considerably, occasionally preventing crystal growth. This occurred even though the starting materials was from the same vendor and was subjected to the same purification treatment. This paper will describe an aqueous precipitation process of mercuric iodide preparation in batches of 3 kg using Hg(NO/sub 3/)/sub 2/ or HgCl/sub 2/and KI. Since these salts are produced in much larger quantities than mercuric iodide, more consistent quality is available. The impurity content of these batched and single crystals are compared. Some of the single crystals grown using the in-house prepared mercuric iodide have yielded a large number of spectroscopy grade nuclear radiation detectors. The influence of the major impuritites are discussed. 13 refs., 4 figs., 1 tab.

  12. Improved Stability of Mercuric Iodide Detectors for Anticoincidence Shields Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to utilize guard ring electrode structures and a new film growth technique to create improved polycrystalline mercuric iodide detectors for background...

  13. Kinetic determination of iodide by the oxidation reaction of benzidine with chloramine B

    International Nuclear Information System (INIS)

    Iodide catalyzed oxidation of benzidine with Chloramine B is studied for its possible application to kinetic determination of iodides. Based on the results of kinetic studies performed, optimal conditions for the catalytic reaction are revealed and a kinetic method for iodide determination is developed. The determination limit of iodide is 2x10-4 μg/ml. It was demonstrated that the proposed method can be used for the determination of iodides in water, soil, and kelp

  14. Prevention of organic iodide formation in BWR`s

    Energy Technology Data Exchange (ETDEWEB)

    Karjunen, T. [Finnish Centre for Radiation and Nuclear Safety, Helsinki (Finland); Laitinen, T.; Piippo, J.; Sirkiae, P. [VTT Manufacturing Technology (Finland)

    1996-12-01

    During an accident, many different forms of iodine may emerge. Organic iodides, such as methyl iodide and ethyl iodide, are relatively volatile, and thus their appearance leads to increased concentration of gaseous iodine. Since organic iodides are also relatively immune to most accident mitigation measures, such as sprays and filters, they can affect the accident source term significantly even when only a small portion of iodine is in organic form. Formation of organic iodides may not be limited by the amount of organic substances available. Excessive amounts of methane can be produced, for example, during oxidation of boron carbide, which is used in BWR`s as a neutron absorber material. Another important source is cable insulation. In a BWR, a large quantity of cables is placed below the pressure vessel. Thus a large quantity of pyrolyse gases will be produced, should the vessel fail. Organic iodides can be formed as a result of many different reactions, but at least in certain conditions the main reaction takes place between an organic radical produced by radiolysis and elemental iodine. A necessary requirement for prevention of organic iodide production is therefore that the pH in the containment water pools is kept high enough to eliminate formation of elemental iodine. In a typical BWR the suppression pool water is usually unbuffered. As a result, the pH may be dominated by chemicals introduced during an accident. If no system for adding basic chemicals is operable, the main factor affecting pool water pH may be hydrochloric acid released during cable degradation. Should this occur, the conditions could be very favorable for production of elemental iodine and, consequently, formation of organic iodides. Although high pH is necessary for iodine retention, it could have also adverse effects. High pH may, for example, accelerate corrosion of containment materials and alter the characteristics of the solid corrosion products. (author) 6 figs., 1 tab., 13 refs.

  15. Processing {alpha}-mercuric iodide by zone refining

    Energy Technology Data Exchange (ETDEWEB)

    Burger, A.; Morgan, S.H.; Henderson, D.O.; Biao, Y.; Zhang, K.; Silberman, E. [Fisk Univ., Nashville, TN (United States). Dept. of Physics; Nason, D.; van den Berg, L.; Ortale-Baccash, C.; Cross, E. [EG and G Energy Measurements, Inc., Goleta, CA (United States). Santa Barbara Operations

    1992-06-01

    An investigation is being conducted on zone refining {alpha}-mercuric iodide. Analytical studies using differential scanning calorimetry and anion chromatography indicate that impurities are segregated mainly at the end where zone travel terminates. Early results indicate that single crystals can be readily grown from zone refined material, and the effects of the process on the performance of radiation detectors fabricated from {alpha}-mercuric iodide are being evaluated.

  16. Adsorption of cesium on cement mortar from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Volchek, Konstantin, E-mail: konstantin.volchek@ec.gc.ca [Emergencies Science and Technology Section, Environment Canada, 335 River Road, Ottawa, Ontario, Canada K1A 0H3 (Canada); Miah, Muhammed Yusuf [Emergencies Science and Technology Section, Environment Canada, 335 River Road, Ottawa, Ontario, Canada K1A 0H3 (Canada); Department of Applied Chemistry and Chemical Technology, Noakhali Science and Technology University (Bangladesh); Kuang, Wenxing; DeMaleki, Zack [Emergencies Science and Technology Section, Environment Canada, 335 River Road, Ottawa, Ontario, Canada K1A 0H3 (Canada); Tezel, F. Handan [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada)

    2011-10-30

    Highlights: {yields} The adsorption of cesium on cement mortar was investigated in a range of temperatures and cesium concentrations. {yields} The pseudo-second order kinetic model produced a good fit with the experimental kinetic data. {yields} Equilibrium test results correlated well with the Freundlich isotherm adsorption model. {yields} The interaction between cesium ions and cement mortar was dominated by chemical adsorption. - Abstract: The adsorption of cesium on cement mortar from aqueous solutions was studied in series of bench-scale tests. The effects of cesium concentration, temperature and contact time on process kinetics and equilibrium were evaluated. Experiments were carried out in a range of initial cesium concentrations from 0.0103 to 10.88 mg L{sup -1} and temperatures from 278 to 313 K using coupons of cement mortar immersed in the solutions. Non-radioactive cesium chloride was used as a surrogate of the radioactive {sup 137}Cs. Solution samples were taken after set periods of time and analyzed by inductively coupled plasma mass spectroscopy. Depending on the initial cesium concentration, its equilibrium concentration in solution ranged from 0.0069 to 8.837 mg L{sup -1} while the respective surface concentration on coupons varied from 0.0395 to 22.34 {mu}g cm{sup -2}. Equilibrium test results correlated well with the Freundlich isotherm model for the entire test duration. Test results revealed that an increase in temperature resulted in an increase in adsorption rate and a decrease in equilibrium cesium surface concentration. Among several kinetic models considered, the pseudo-second order reaction model was found to be the best to describe the kinetic test results in the studied range of concentrations. The adsorption activation energy determined from Arrhenius equation was found to be approximately 55.9 kJ mol{sup -1} suggesting that chemisorption was the prevalent mechanism of interaction between cesium ions and cement mortar.

  17. Studies on release and deposition behaviour of cesium from contaminated sodium pools and cesium trap development for FBTR

    International Nuclear Information System (INIS)

    Investigations were carried out on the release and deposition behaviour of cesium from sodium pools in air-filled chamber in the temperature range of 673 to 873 K, using Cs-134 to simulate Cs-137. About 0.12 kg of sodium was loaded in a burn-pot together with 92.5 kBq of cesium. Experiments were carried out with 21% oxygen. Natural burning period of sodium and specific activity ratio between cesium and sodium showed a tendency to decrease and release fractions of both the species tended to increase with temperature. From the surface deposited aerosols it was observed that cesium has propensity to settle down closer to the point of release. A cesium trap has been developed for FBTR with RVC as getter material. Absorption kinetics and particle release behaviour studies pointed to its intended satisfactory performance in the plant. (author)

  18. Sympathetic cooling in a rubidium cesium mixture: Production of ultracold cesium atoms

    International Nuclear Information System (INIS)

    This thesis presents experiments for the production of ultracold rubidium cesium mixture in a magnetic trap. The long-termed aim of the experiment is the study of the interaction of few cesium atoms with a Bose-Einstein condensate of rubidium atoms. Especially by controlled variation of the cesium atom number the transition in the description of the interaction by concepts of the one-particle physics to the description by concepts of the many-particle physics shall be studied. The rubidium atoms are trapped in a magneto-optical trap (MOT) and from there reloaded into a magnetic trap. In this the rubidium atoms are stored in the state vertical stroke f=2,mf=2 right angle of the electronic ground state and evaporatively cooled by means of microwave-induced transitions into the state vertical stroke f=1,mf=1] (microwave cooling). The cesium atoms are also trppaed in a MOT and into the same magnetic trap reloaded, in which they are stored in the state vertical stroke f=4,mf=4 right angle of the electronic ground state together with rubidium. Because of the different hyperfine splitting only rubidium is evaporatively cooled, while cesium is cooled jointly sympathetically - i.e. by theramal contact via elastic collisions with rubidium atoms. The first two chapters contain a description of interatomic interactions in ultracold gases as well as a short summary of theoretical concepts in the description of Bose-Einstein condensates. The chapters 3 and 4 contain a short presentation of the methods applied in the experiment for the production of ultracold gases as well as the experimental arrangement; especially in the framework of this thesis a new coil system has been designed, which offers in view of future experiments additionally optical access for an optical trap. Additionally the fourth chapter contains an extensive description of the experimental cycle, which is applied in order to store rubidium and cesium atoms together into the magnetic trap. The last chapter

  19. A review of polytypism in lead iodide

    Energy Technology Data Exchange (ETDEWEB)

    Beckmann, P.A. [Department of Physics, Bryn Mawr College, Bryn Mawr, Pennsylvania (United States)

    2010-05-15

    Lead Iodide (PbI{sub 2}) is an important inorganic solid for both basic scientific research and possible technological applications and in this brief review we discuss the structure of PbI{sub 2}. Although the basic structure is a simple I-Pb-I layered structure with a[PbI{sub 6}]{sup 4-} near-octahedron being the basic building block, there are many ways of stacking the layers which results in many polytypes. We present 20 of the 23 entries for the structure of PbI{sub 2} from the Inorganic Structural Database and order them by polytype. This represents more than 80 years of crystallographic research in the structure of this compound. We present a simple way to view the 2H, 4H, 6H, and 6R polytypes and extend the procedure to higher-order polytypes. We note a relationship, not generally appreciated, between the distortion of the near [PbI{sub 6}]{sup 4-} octahedrons and the polytype. We suggest that the significance of vacancies has only recently been appreciated. We suggest that small discrepancies in structure determination are probably due to different distributions of vacancies and that there are, in practice, very many structures for macroscopic or even mesoscopic samples of a given polytype when vacancies are considered. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Mercuric iodide photodetectors for scintillation spectroscopy

    International Nuclear Information System (INIS)

    We have measured the responses to 137Cs (662 keV) of both a 1-inch-diam by 2-inch-thick NaI(Tl) scintillator optically coupled to a 1-inch-diam by 800-μmthick mercuric iodide (HgI2) photodetector, and a 1-cmdiam by 1-cm-thick CaWO4 scintillator coupled to a 1.3-cm-diam by 600-μm-thick HgI2 photodetector. Best spectral resolution to 137Cs was 7.8% FWHM for the NaI(Tl)-HgI2 and 12.5% FWHM for the CaWO4-HgI2 detectors; peak-to-valley ratios were 26:1 and 16:1, respectively. HgI2 detectors operate at room temperature and their use in scintillation spectroscopy presents the ultimate miniaturization of scintillation detectors, limited mainly by the size of the scintillation crystal

  1. Mercuric iodide photodetectors for scintillation spectroscopy

    International Nuclear Information System (INIS)

    We have measured the responses to 137Cs (662 keV) of both a 1-inch-diam by 2-inch-thick NaI(Tl) scintillator optically coupled to a 1-inch-diam by 800-μm-thick mercuric iodide (HgI2) photodetector, and a 1-cm-diam by 1-cm-thick CaWO4 scintillator coupled to a 1.3-cm-diam by 600-μm-thick HgI2 photodetector. Best spectral resolution to 137Cs was 7.8% FWHM for the NaI(Tl)-HgI2 and 12.5% FWHM for the CaWO4-HgI2 detectors; peak-to-valley ratios were 26:1 and 16:1, respectively. HgI2 detectors operate at room temperature and their use in scintillation spectroscopy presents the ultimate miniaturization of scintillation detectors, limited mainly by the size of the scintillation crystal

  2. Mercuric iodide photodetectors for scintillation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Markakis, J.; Dabrowski, A.; Iwanczyk, J.; Ortale, C.; Schnepple, W.

    1985-02-01

    We have measured the responses to /sup 137/Cs (662 keV) of both a 1-inch-diam by 2-inch-thick NaI(Tl) scintillator optically coupled to a 1-inch-diam by 800-..mu..mthick mercuric iodide (HgI/sub 2/) photodetector, and a 1-cmdiam by 1-cm-thick CaWO/sub 4/ scintillator coupled to a 1.3-cm-diam by 600-..mu..m-thick HgI/sub 2/ photodetector. Best spectral resolution to /sup 137/Cs was 7.8% FWHM for the NaI(Tl)-HgI/sub 2/ and 12.5% FWHM for the CaWO/sub 4/-HgI/sub 2/ detectors; peak-to-valley ratios were 26:1 and 16:1, respectively. HgI/sub 2/ detectors operate at room temperature and their use in scintillation spectroscopy presents the ultimate miniaturization of scintillation detectors, limited mainly by the size of the scintillation crystal.

  3. Mercuric iodide photodetectors for scintillation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Markakis, J.; Ortale, C.; Schnepple, W.; Iwanczyk, J.; Dabrowski, A.

    1984-01-01

    We have measured the responses to /sup 137/Cs (662 keV) of both a 1-inch-diam by 2-inch-thick NaI(Tl) scintillator optically coupled to a 1-inch-diam by 800-..mu..m-thick mercuric iodide (HgI/sub 2/) photodetector, and a 1-cm-diam by 1-cm-thick CaWO/sub 4/ scintillator coupled to a 1.3-cm-diam by 600-..mu..m-thick HgI/sub 2/ photodetector. Best spectral resolution to /sup 137/Cs was 7.8% FWHM for the NaI(Tl)-HgI/sub 2/ and 12.5% FWHM for the CaWO/sub 4/-HgI/sub 2/ detectors; peak-to-valley ratios were 26:1 and 16:1, respectively. HgI/sub 2/ detectors operate at room temperature and their use in scintillation spectroscopy presents the ultimate miniaturization of scintillation detectors, limited mainly by the size of the scintillation crystal.

  4. Microbial uptake of uranium, cesium, and radium

    International Nuclear Information System (INIS)

    The ability of diverse microbial species to concentrate uranium, cesium, and radium was examined. Saccharomyces cerevisiae, Pseudomonas aeruginosa, and a mixed culture of denitrifying bacteria accumulated uranium to 10 to 15% of the dry cell weight. Only a fraction of the cells in a given population had visible uranium deposits in electron micrographs. While metabolism was not required for uranium uptake, mechanistic differences in the metal uptake process were indicated. Uranium accumulated slowly (hours) on the surface of S. cerevisiae and was subject to environmental factors (i.e., temperature, pH, interfering cations and anions). In contrast, P. aeruginosa and the mixed culture of denitrifying bacteria accumulated uranium rapidly (minutes) as dense, apparently random, intracellular deposits. This very rapid accumulation has prevented us from determining whether the uptake rate during the transient between the initial and equilibrium distribution of uranium is affected by environmental conditions. However, the final equilibrium distributions are not affected by those conditions which affect uptake by S. cerevisiae. Cesium and radium were concentrated to a considerably lesser extent than uranium by the several microbial species tested. The potential utility of microorganisms for the removal and concentration of these metals from nuclear processing wastes and several bioreactor designs for contacting microorganisms with contaminated waste streams will be discussed

  5. Intense non-relativistic cesium ion beam

    International Nuclear Information System (INIS)

    The Heavy Ion Fusion group at Lawrence Berkeley Laboratory has constructed the One Ampere Cesium Injector as a proof of principle source to supply an induction linac with a high charge density and high brightness ion beam. This is studied here. An electron beam probe was developed as the major diagnostic tool for characterizing ion beam space charge. Electron beam probe data inversion is accomplished with the EBEAM code and a parametrically adjusted model radial charge distribution. The longitudinal charge distribution was not derived, although it is possible to do so. The radial charge distribution that is derived reveals an unexpected halo of trapped electrons surrounding the ion beam. A charge fluid theory of the effect of finite electron temperature on the focusing of neutralized ion beams (Nucl. Fus. 21, 529 (1981)) is applied to the problem of the Cesium beam final focus at the end of the injector. It is shown that the theory's predictions and assumptions are consistent with the experimental data, and that it accounts for the observed ion beam radius of approx. 5 cm, and the electron halo, including the determination of an electron Debye length of approx. 10 cm

  6. Cesium separation Using Electrically Switched Ion Exchange

    International Nuclear Information System (INIS)

    Electrically Switched Ion Exchange (ESIX) is a separation technology being developed at Pacific Northwest National Laboratory as an alternative to conventional ion exchange for removing metal ions from wastewater. In ESIX, which combines ion exchange and electro-chemistry, ion uptake and elution can be controlled directly by modulating the potential of an ion exchange film that has been electrochemically deposited onto an electrode. This paper presents the results of experiments on high surface area electrodes and the development of a flow system for cesium ion separation. Bench-scale flow system studies showed no change in capacity or performance of the ESIX films at a flow rate up to 113 BV/h, the maxi-mum flow rate tested, and breakthrough curves supported once-through waste processing. A comparison of results for a stacked 5-electrode cell versus a single-electrode cell showed enhanced breakthrough performance. In the stacked configuration, break-through began at about 120 BV for a feed containing 0.2 ppm cesium at a flow rate of 13 BV/h. A case study for the KE Basin (a spent nuclear fuel storage basin) on the Hanford Site demonstrated that KE Basin wastewater could be processed continuously with minimal waste generation, reduced disposal costs, and lower capital expenditures

  7. Biosorption behavior and mechanism of cesium-137 on Rhodosporidium fluviale strain UA2 isolated from cesium solution

    International Nuclear Information System (INIS)

    In order to identify a more efficient biosorbent for 137Cs, we have investigated the biosorption behavior and mechanism of 137Cs on Rhodosporidium fluviale (R. fluviale) strain UA2, one of the dominant species of a fungal group isolated from a stable cesium solution. We observed that the biosorption of 137Cs on R. fluviale strain UA2 was a fast and pH-dependent process in the solution composed of R. fluviale strain UA2 (5 g/L) and cesium (1 mg/L). While a Langmuir isotherm equation indicated that the biosorption of 137Cs was a monolayer adsorption, the biosorption behavior implied that R. fluviale strain UA2 adsorbed cesium ions by electrostatic attraction. The TEM analysis revealed that cesium ions were absorbed into the cytoplasm of R. fluviale strain UA2 across the cell membrane, not merely fixed on the cell surface, which implied that a mechanism of metal uptake contributed largely to the cesium biosorption process. Moreover, PIXE and EPBS analyses showed that ion-exchange was another biosorption mechanism for the cell biosorption of 137Cs, in which the decreased potassium ions were replaced by cesium ions. All the above results implied that the biosorption of 137Cs on R. fluviale strain UA2 involved a two-step process. The first step is passive biosorption that cesium ions are adsorbed to cells surface by electrostatic attraction; after that, the second step is active biosorption that cesium ions penetrate the cell membrane and accumulate in the cytoplasm. - Highlights: • Microorganisms isolated from a cesium solution are considered as a biosorbent to remove cesium ions. • The biosorption equilibrium is fitted well to a Langmuir model with a correlation coefficient of 0.9997. • First attempt to explore biosorption mechanisms using PIXE and EPBS. • Living and dead microorganisms have different biosorption mechanisms. • The biosorption of 137Cs involved a two-step process: passive and active

  8. Posttranscriptional regulation of sodium-iodide symporter mRNA expression in the rat thyroid gland by acute iodide administration.

    Science.gov (United States)

    Serrano-Nascimento, Caroline; Calil-Silveira, Jamile; Nunes, Maria Tereza

    2010-04-01

    Iodide is an important regulator of thyroid activity. Its excess elicits the Wolff-Chaikoff effect, characterized by an acute suppression of thyroid hormone synthesis, which has been ascribed to serum TSH reduction or TGF-beta increase and production of iodolipids in the thyroid. These alterations take hours/days to occur, contrasting with the promptness of Wolff-Chaikoff effect. We investigated whether acute iodide administration could trigger events that precede those changes, such as reduction of sodium-iodide symporter (NIS) mRNA abundance and adenylation, and if perchlorate treatment could counteract them. Rats subjected or not to methylmercaptoimidazole treatment (0.03%) received NaI (2,000 microg/0.5 ml saline) or saline intraperitoneally and were killed 30 min up to 24 h later. Another set of animals was treated with iodide and perchlorate, in equimolar doses. NIS mRNA content was evaluated by Northern blotting and real-time PCR, and NIS mRNA poly(A) tail length by rapid amplification of cDNA ends-poly(A) test (RACE-PAT). We observed that NIS mRNA abundance and poly(A) tail length were significantly reduced in all periods of iodide treatment. Perchlorate reversed these effects, indicating that iodide was the agent that triggered the modifications observed. Since the poly(A) tail length of mRNAs is directly associated with their stability and translation efficiency, we can assume that the rapid decay of NIS mRNA abundance observed was due to a reduction of its stability, a condition in which its translation could be impaired. Our data show for the first time that iodide regulates NIS mRNA expression at posttranscriptional level, providing a new mechanism by which iodide exerts its autoregulatory effect on thyroid. PMID:20107044

  9. Iodide kinetics and experimental I-131 therapy in a xenotransplanted human sodium-iodide symporter-transfected human follicular thyroid carcinoma cell line

    NARCIS (Netherlands)

    Smit, J.W.A.; Elst, van der J.P.; Karperien, M.; Que, I.; Stokkel, M.; Heide, van der D.; Romijn, J.A.

    2002-01-01

    Uptake of iodide is a prerequisite for radioiodide therapy in thyroid cancer. However, loss of iodide uptake is frequently observed in metastasized thyroid cancer, which may be explained by diminished expression of the human sodium-iodide symporter (hNIS). We studied whether transfection of hNIS int

  10. Charge Lifetime Study of K2CsSb Photocathode Inside a JLAB DC High Voltage Gun

    International Nuclear Information System (INIS)

    Two photocathodes are frequently considered for generating high average current electron beams and/or beams with high brightness for current and future accelerator applications: GaAs:Cs and K2CsSb. Each photocathode has advantages and disadvantages, and need to demonstrate performance at 'production' accelerator facilities. To this end a K2CsSb photocathode was manufactured at Brookhaven National Lab and delivered to Jefferson Lab within a compact vacuum apparatus at pressure ∼ 5 x 10-11 Torr. This photocathode was installed inside a dc high voltage photogun biased at voltages up to 200 kV, and illuminated with laser light at 440 or 532 nm, to generate beams up to 20 mA. Photocathode charge lifetime measurements indicate that under some conditions this cathode has exceptionally high charge lifetime, without measurable QE decay, even from the center of the photocathode where operation using GaAs photocathodes is precluded due to ion bombardment. These studies also suggest a complex QE decay mechanism likely related to chemistry and localized heating via the laser beam.

  11. Novel Cathode and Photocathode Materials for Dye-Sensitized Solar Cells

    Czech Academy of Sciences Publication Activity Database

    Kavan, Ladislav; Vlčková Živcová, Zuzana; Krýsová, Hana; Cígler, Petr; Liska, P.; Zakeeruddin, S. M.; Grätzel, M.

    Taipei: International Society of Electrochemistry , 2015. 826. [Annual Meeting of the International Society of Electrochemistry . Green Electrochemistry for Tomorrow´s Society /66./. 04.10.2015-09.10.2015, Taipei] R&D Projects: GA ČR GA13-07724S Institutional support: RVO:61388955 Keywords : dye-sensitized solar cells * photocathodes * electrochemistry Subject RIV: CG - Electrochemistry

  12. Characterisation of Pb thin films prepared by the nanosecond pulsed laser deposition technique for photocathode application

    International Nuclear Information System (INIS)

    Pb thin films were prepared by the nanosecond pulsed laser deposition technique on Si (100) and polycrystalline Nb substrates for photocathode application. As the photoemission performances of a cathode are strongly affected by its surface characteristics, the Pb films were grown at different substrate temperatures with the aim of modifying the morphology and structure of thin films. An evident morphological modification in the deposited films with the formation of spherical grains at higher temperatures has been observed. X-ray diffraction measurements showed that a preferred orientation of Pb (111) normal to the substrate was achieved at 30 °C while the Pb (200) plane became strongly pronounced with the increase in the substrate temperature. Finally, a Pb thin film deposited on Nb substrate at 30 °C and tested as the photocathode showed interesting results for the application of such a device in superconducting radio frequency guns. - Highlights: • Pb thin films obtained by the nanosecond pulsed laser deposition technique at different substrate temperature. • The substrate temperature modifies the morphology and structure of Pb films. • Pb thin film was deposited at room temperature for photocathode application. • The Pb thin film photocathode was tested and the quantum efficiency of the device improved after laser cleaning treatment of the film surface

  13. 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

    2016-01-01

    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. PMID:27431993

  14. Silicon decorated with amorphous cobalt molybdenum sulfide catalyst as an efficient photocathode for solar hydrogen generation.

    Science.gov (United States)

    Chen, Yang; Tran, Phong D; Boix, Pablo; Ren, Yi; Chiam, Sing Yang; Li, Zhen; Fu, Kunwu; Wong, Lydia H; Barber, James

    2015-04-28

    The construction of viable photoelectrochemical (PEC) devices for solar-driven water splitting can be achieved by first identifying an efficient independent photoanode for water oxidation and a photocathode for hydrogen generation. These two photoelectrodes then must be assembled with a proton exchange membrane within a complete coupled system. Here we report the preparation of a Si/a-CoMoSx hybrid photocathode which shows impressive performance (onset potential of 0.25 V vs RHE and photocurrent jsc of 17.5 mA cm(-2) at 0 V vs RHE) in pH 4.25 phosphate solution and under simulated AM 1.5 solar illumination. This performance is among the best reported for Si photocathodes decorated with noble-metal-free catalysts. The electrode preparation is scalable because it relies on a photoassisted electrodeposition process employing an available p-type Si electrode and [Co(MoS4)2](2-) precursor. Investigation of the mechanism of the Si/a-CoMoSx electrode revealed that under conditions of H2 photogeneration this bimetallic sulfide catalyst is highly efficient in extracting electrons from illuminated Si and subsequently in reducing protons into H2. The Si/a-CoMoSx photocathode is functional over a wide range of pH values, thus making it a promising candidate for the construction of a complete solar-driven water splitting PEC device. PMID:25801437

  15. Research and development of high-temperature operating photocathode electron source for high brightness electron gun

    International Nuclear Information System (INIS)

    We have been developing a novel photocathode RF gun system with an advanced RF cavity structure and a new photocathode material for the SuperKEKB electron linac. This injector is required to obtain a low emittance and high charge electron beams in order to achieve the highest luminosity in the world. The required beam parameters are 5 nC and 20 mm·mrad from the RF gun. Moreover, 10 nC electron beams for positron production will be also generated by the same RF gun. In order to obtain extremely high charge electron beams, Yb-based laser system is being upgraded for higher power and a high temperature photocathode system for a quantum efficiency (QE) enhancement will be introduced to the new RF gun system. This paper reports on the research and development of the system of high temperature photocathode for QE enhancement to be able to generate high charge electron beams (∼10 nC) at the RF gun in SuperKEKB electron linac. (author)

  16. Spatial variability and Cesium-137 inventories in native forest

    International Nuclear Information System (INIS)

    With the nuclear fission discovery and development of nuclear weapons in 1940s, artificial radioisotopes were introduced in the environment. This contamination is due to worldwide fallout by superficial nuclear tests realized from early 1950s to late 1970s by USA, former URSS, UK, France and China. One of theses radioisotopes that have been very studied is cesium-137. Cesium-137 has a half-life of 30.2 years and its biological behavior is similar to the potassium. The behavior in soil matrix, depth distribution, spatial variability and inventories values of cesium-137 has been determinate for several regions of the world. In Brazil, some research groups have worked on this subject, but there are few works published about theses properties of cesium-137. The aim of this paper was study the depth distribution, spatial variability, and inventory of cesium-137 in native forest. Two native forests (Mata 1 and Mata UEL) were sampling in region of Londrina, PR. The results shows that there is a spatial variability of 40% for Mata 1 and 42% for Mata UEL. The depth distribution of cesium-137 for two forests presented a exponential form, characteristic to undisturbed soil. Cesium-137 inventory determinate for Mata 1 was 358 Bq m-2 and for Mata UEL was 320 Bq m-2. (author)

  17. Methyl Iodide Formation Under Postulated Nuclear Reactor Accident Conditions

    International Nuclear Information System (INIS)

    The formation of methyl iodide under conditions of postulated nuclear reactor accidents is discussed. Although thermodynamic calculations indicate the equilibrium methyl iodide concentrations would be quite low, calculations based on a simple kinetic scheme involving reaction between small hydrocarbon species and iodine indicate that concentrations higher than equilibrium can occur during the course of the reaction. Such calculations were performed over a wide range of initial species concentrations and a range of temperatures representative of some reactor accident situations. These calculations suggest that little methyl iodide would be expected within the core volume where temperatures are maximum. As the gas leaves the core volume and expands into the plenum region, it cools and the concentration of methyl iodide increases. At the intermediate temperatures which might characterize this region, the formation of methyl iodide from thermally induced reactions could reach its maximum rate. The gas continues to cool, however, and it is probable that by the time it leaves the plenum region it has cooled to the point where thermally induced reactions may be of little importance. Although the thermally induced reactions will become slower as the gas expands and cools, the radiation-induced reactions will not be slowed to the same extent. The gases leaving the core carry fission products and hence a radiation source is available to initiate reaction by a temperature-independent process. An investigation of the radiation chemical formation and decomposition of methyl iodide in the presence of steam suggests that radiation-induced methyl iodide formation will generally be rapid under the postulated accident situations. Thus, in the plenum region where thermal reactions have become slow, the radiation-induced reaction can still proceed and may well become the dominant factor. The same situation probably pertains as well to the containment region. (author)

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

    International Nuclear Information System (INIS)

    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)

  19. Pollution of drug-technical materials by cesium-137

    International Nuclear Information System (INIS)

    Drug-technical raw materials are medicinal plants (flowers, folium, grasses, mushrooms, roots, fruits, berry, kidney, cortex), used in pharmacy. To limit receipt cesium-137 in people body in 1993 in the Republic of Belarus were created 'Temporary permission levels of the cesium-137 radionuclides contents in drug-technical raw materials' were created (TPL-1993). The permission levels of cesium-137 are following: for drug-technical raw material (flowers, folium, grass, mushrooms, roots and other plants parts) - 1850 Bq/kg, for dried up fruits and berries - 2590 Bq/kg. (Author)

  20. Synthesis and peculiarities of the cesium zeolite crystal structure (cesite)

    International Nuclear Information System (INIS)

    An attempt is made to synthesize cesium zeolite by introduction of amorphous seed crystals which correspond by composition with cesium-containing zeolite into the aluminosilicate gel, since this method can produce zeolite with a crystal structure it would not adopt under the usual conditions. It is seen that during crystablization upon introduction of a seed crystal the cesium content in zeolite decreases. A more complete structural elucidation of zeolite obtained by the suggested method was carried out by x0ray and IR spectral analyses. The data of x-ray analysis showed that the structures of synthesized zeolite and binary octagonal pores are similar

  1. Molecular imaging using sodium iodide symporter (NIS)

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Je Yoel [School of Dentistry, Kyungpook National Univ., Daegu (Korea, Republic of)

    2004-04-01

    Radioiodide uptake in thyroid follicular epithelial cells, mediated by a plasma membrane transporter, sodium iodide symporter (NIS), provides a first step mechanism for thyroid cancer detection by radioiodide injection and effective radioiodide treatment for patients with invasive, recurrent, and/or metastatic thyroid cancers after total thyroidectomy. NIS gene transfer to tumor cells may significantly and specifically enhance internal radioactive accumulation of tumors following radioiodide administration, and result in better tumor control. NIS gene transfers have been successfully performed in a variety of tumor animal models by either plasmid-mediated transfection or virus (adenovirus or retrovirus)-mediated gene delivery. These animal models include nude mice xenografted with human melanoma, glioma, breast cancer of prostate cancer, rats with subcutaneous thyroid tumor implantation, as well as the rat intracranial glioma model. In these animal models, non-invasive imaging of in vivo tumors by gamma camera scintigraphy after radioiodide or technetium injection has been performed successfully, suggesting that the NIS can serve as an imaging reporter gene for gene therapy trials. In addition, the tumor killing effects of I-131, ReO4-188 and At-211 after NIS gene transfer have been demonstrated in in vitro clonogenic assays and in vivo radioiodide therapy studies, suggesting that NIS gene can also serve as a therapeutic requires a more efficient and specific system of gene delivery with better retention of radioiodide in tumor. Results thus far are, however, promising, and suggest that NIS gene transfer followed by radioiodide treatment will allow non-invasive in vivo imaging to assess the outcome of gene therapy and provide a therapeutic strategy for a variety of human diseases.

  2. Molecular imaging using sodium iodide symporter (NIS)

    International Nuclear Information System (INIS)

    Radioiodide uptake in thyroid follicular epithelial cells, mediated by a plasma membrane transporter, sodium iodide symporter (NIS), provides a first step mechanism for thyroid cancer detection by radioiodide injection and effective radioiodide treatment for patients with invasive, recurrent, and/or metastatic thyroid cancers after total thyroidectomy. NIS gene transfer to tumor cells may significantly and specifically enhance internal radioactive accumulation of tumors following radioiodide administration, and result in better tumor control. NIS gene transfers have been successfully performed in a variety of tumor animal models by either plasmid-mediated transfection or virus (adenovirus or retrovirus)-mediated gene delivery. These animal models include nude mice xenografted with human melanoma, glioma, breast cancer of prostate cancer, rats with subcutaneous thyroid tumor implantation, as well as the rat intracranial glioma model. In these animal models, non-invasive imaging of in vivo tumors by gamma camera scintigraphy after radioiodide or technetium injection has been performed successfully, suggesting that the NIS can serve as an imaging reporter gene for gene therapy trials. In addition, the tumor killing effects of I-131, ReO4-188 and At-211 after NIS gene transfer have been demonstrated in in vitro clonogenic assays and in vivo radioiodide therapy studies, suggesting that NIS gene can also serve as a therapeutic requires a more efficient and specific system of gene delivery with better retention of radioiodide in tumor. Results thus far are, however, promising, and suggest that NIS gene transfer followed by radioiodide treatment will allow non-invasive in vivo imaging to assess the outcome of gene therapy and provide a therapeutic strategy for a variety of human diseases

  3. Management of cesium loaded AMP- Part I preparation of 137Cesium concentrate and cementation of secondary wastes

    International Nuclear Information System (INIS)

    Separation of 137cesium from High Level Waste can be achieved by use of composite-AMP, an engineered form of Ammonium Molybdo-Phosphate(AMP). Direct vitrification of cesium loaded composite AMP in borosilicate glass matrix leads to separation of water soluble molybdate phase. A proposed process describes two different routes of selective separation of molybdates and phosphate to obtain solutions of cesium concentrates. Elution of 137Cesium from composite-AMP by decomposing it under flow conditions using saturated barium hydroxide was investigated. This method leaves molybdate and phosphate embedded in the column but only 70% of total cesium loaded on column could be eluted. Alternatively composite-AMP was dissolved in sodium hydroxide and precipitation of barium molybdate-phosphate from the resultant solution, using barium nitrate was investigated by batch methods. The precipitation technique gave over 99.9% of 137Cesium activity in solutions, free of molybdates and phosphates, which is ideally suited for immobilization in borosilicate glass matrix. Detailed studies were carried out to immobilize secondary waste of 137Cesium contaminated barium molybdate-phosphate precipitates in the slag cement matrix using vermiculite and bentonite as admixtures. The cumulative fraction of 137Cs leached from the cement matrix blocks was 0.05 in 140 days while the 137Cs leach rate was 0.001 gm/cm2/d. (author)

  4. Biosorption of uranium, radium, and cesium

    International Nuclear Information System (INIS)

    Some fundamental aspects of the biosorption of metals by microbial cells were investigated. These studies were carried out in conjunction with efforts to develop a process to utilize microbial cells as biosorbents for the removal of radionuclides from waste streams generated by the nuclear fuel cycle. It was felt that an understanding of the mechanism(s) of metal uptake would potentially enable the enhancement of the metal uptake phenomenon through environmental or genetic manipulation of the microorganisms. Also presented are the results of a preliminary investigation of the applicability of microorganisms for the removal of 137cesium and 226radium from existing waste solutions. The studies were directed primarily at a characterization of uranium uptake by the yeast, Saccharomyces cerevisiae, and the bacterium, Pseudomonas aeruginosa

  5. Structure of double hafnium and cesium sulfate

    International Nuclear Information System (INIS)

    The structure of a compound whose formula according to the structural investigation is Cssub(2+x)Hf(SOsub(4))sub(2+x)(HSOsub(4))sub(2-x)x3Hsub(2)O (x approximately 0.7) (a=10.220, b=12.004, c=15.767 A, space group Pcmn) is determined by diffractometric data (2840 reflections, anisotropic refinement, R=0.087). It is build of complex unions [Hf(SO4)4H2O]4-, Cs+ cations and water molecules. Eight O atoms surrounding Hf atom (dodecahedron Hf-O 2.10-2.22 A) belong to four sulphate groups and water molecule. Three sulphate groups are bidentate-cyclic, and one group - monodentate relative to Hf. The structure has a cesium deficit in particular positions

  6. Double manganese(III) cesium triphosphate

    International Nuclear Information System (INIS)

    Double triphosphates have been identified in research on interactions in the P2O5-M2O3-Cs2O-H2O system, where M(III) = Al, Ga, Cr, Fe, at 570-770K, which have the M(III)Cs2 - P3O10 composition; here we report the identification of a new phase made under analogous conditions in a system containing Mn(III) together with some of its physicochemical properties. The product was analyzed for phosphorus by a colorimetric method, for manganese by titration with EDTA, and for cesium by atomic absorption. The x-ray phase analysis was performed with a DRON-3.0 diffractometer. The IR spectra were recorded. Thermogravimetry indicates that the product is MnCs2P3O10·H2O

  7. Sorption of cesium and strontium by arid region desert soil

    International Nuclear Information System (INIS)

    Adsorption and ion exchange in soil systems are the principal mechanisms that retard the migration of nuclear waste to the biosphere. Cesium and strontium are two elements with radioactive isotopes (Cs137 and Sr90) that are commonly disposed of as nuclear waste. The sorption and ion exchange properties of nonradioactive cesium and strontium were studied in this investigation. The soil used in this study was collected at an experimental infiltration site on Frenchman Flat, a closed drainage basin on the Nevada Test Site. This soil is mostly nonsaline-alkali sandy loam and loamy sand with a cation exchange capacity ranging from 13 to 30 me/100g. The clay fraction of the soil contains illite, montmorillonite, and clinoptilolite. Ion exchange studies have shown that this soil sorbs cesium preferentially relative to strontium, and that charge for charge, the exchange-phase cations released from exchange sites exceed the cesium and strontium sorbed by the soil. 38 references, 22 figures

  8. Comparison of CsBr and KBr coated Cu photocathodes. Effects of laser irradiation and work function changes

    Energy Technology Data Exchange (ETDEWEB)

    He, Weidong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); VilayurGanapathy, Subramanian [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Joly, Alan G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Droubay, Timothy C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Chambers, Scott A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Maldonado, Juan R. [Stanford Univ., CA (United States); Hess, Wayne P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-02-20

    Thin films (7 nm layers) of CsBr and KBr were deposited on Cu(100) to investigate photoemission properties of these potential photocathode materials. After thin film deposition and prolonged laser ultraviolet (UV) irradiation (266 nm picosecond laser) photoemission quantum efficiency increases by factors of 26 and 77 for KBr/Cu(100) and CsBr/Cu(100) photocathodes, respectively. Immediately following thin film deposition, a decrease in work function is observed, compared to bare Cu, in both cases. Quantum efficiency enhancements are attributed to the decrease in photocathode work function, due to the deposition of alkali halide thin films, and photo-induced processes, that introduce defect states into the alkali halide bandgap, induced by UV laser irradiation. It is possible that alkali metal formation occurs during UV irradiation and that this further contributes to photoemission enhancement. Our results suggest that KBr, a relatively stable alkali-halide, has potential for photocathode applications.

  9. Study of bi-alkali photocathode growth on glass by X-ray techniques for fast timing response photomultipliers

    Science.gov (United States)

    Xie, Junqi; Demarteau, Marcel; Wagner, Robert; Ruiz-Oses, Miguel; Liang, Xue; Ben-Zvi, Ilan; Attenkofer, Klaus; Schubert, Susanne; Smedley, John; Wong, Jared; Padmore, Howard; Woll, Arthur

    2014-03-01

    Bi-alkali antimonide photocathode is an essential component in fast timing response photomultipliers. Real-time in-situ grazing incidence x-ray diffraction and post-growth x-ray reflectivity measurement were performed to study the photocathode deposition process on glass substrate. Grazing incidence x-ray diffraction patterns show the formation of Sb crystalline, dissolution of crystalline phase Sb by the application of K vapor and reformation of refined crystal textures. XRR result exhibits that the film thickness increases ~ 4.5 times after K diffusion and almost have no change after Cs diffusion. Further investigation is expected to understand the photocathode growth process and provide guidelines for photocathode development.

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

    International Nuclear Information System (INIS)

    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 cm2 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

  11. Sorption of cesium on Olkiluoto mica gneiss, granodiorite and granite

    International Nuclear Information System (INIS)

    Cesium was selected as a model to study the sorption in bedrock occurring by ion exchange mechanism. The aim of the study was to supplement the existing data on sorption occurring by ion exchange mechanism in bedrock of the candidate sites for spent fuel disposal at Olkiluoto. The sorption of cesium was studied on crushed mica gneiss, tonalite (granodiorite) and granite in artificial groundwaters. Fresh water was represented by Allard water, pH 8 and pH 7, and saline water by Ol-So water, pH 7 and pH 9. In addition, a Na-Ca-Cl brine water and its 1:10 dilution were used as simulants. Cesium concentrations were between 10-8 and 10-3 mol/l. The distribution coefficients of the sorption, Rd and Ra values were determined by batch method. Isotherms were partly non-linear with slopes 0.7 - 1.0 depending on rock and water. At the end of the sorption experiment, the water was analysed for cations exchanged for cesium. The sorption of cesium was also studied as a function of ionic strength. The ionic strength increased in the order Allard < 0l-Br 1:10 < 0l-So < 0l-Br. The sorption of cesium was lower at higher ionic strength and higher Cs concentration. The mineral composition of rocks was determined by thin section analysis, and the sorption distribution ratios on thin sections in the different waters were determined by batch technique. The minerals, that sorbed most cesium were determined by autoradiography. These were biotite, muscovite and chlorite. Cordierite in mica gneiss also sorbed cesium very effectively. (orig.)

  12. Sorption of cesium on Olkiluoto mica gneiss, granodiorite and granite

    Energy Technology Data Exchange (ETDEWEB)

    Huitti, T.; Hakanen, M. [Univ. of Helsinki (Finland). Lab. of Radiochemistry; Lindberg, A. [Geological Survey of Finland, Espoo (Finland)

    1998-09-01

    Cesium was selected as a model to study the sorption in bedrock occurring by ion exchange mechanism. The aim of the study was to supplement the existing data on sorption occurring by ion exchange mechanism in bedrock of the candidate sites for spent fuel disposal at Olkiluoto. The sorption of cesium was studied on crushed mica gneiss, tonalite (granodiorite) and granite in artificial groundwaters. Fresh water was represented by Allard water, pH 8 and pH 7, and saline water by Ol-So water, pH 7 and pH 9. In addition, a Na-Ca-Cl brine water and its 1:10 dilution were used as simulants. Cesium concentrations were between 10{sup -8} and 10{sup -3} mol/l. The distribution coefficients of the sorption, R{sub d} and R{sub a} values were determined by batch method. Isotherms were partly non-linear with slopes 0.7 - 1.0 depending on rock and water. At the end of the sorption experiment, the water was analysed for cations exchanged for cesium. The sorption of cesium was also studied as a function of ionic strength. The ionic strength increased in the order Allard < 0l-Br 1:10 < 0l-So < 0l-Br. The sorption of cesium was lower at higher ionic strength and higher Cs concentration. The mineral composition of rocks was determined by thin section analysis, and the sorption distribution ratios on thin sections in the different waters were determined by batch technique. The minerals, that sorbed most cesium were determined by autoradiography. These were biotite, muscovite and chlorite. Cordierite in mica gneiss also sorbed cesium very effectively. (orig.) 12 refs.

  13. Cesium pre-implantation of embedded biological sections

    International Nuclear Information System (INIS)

    An ion implantation system which allows the implantation of a large surface of a specimen has been used to obtain an homogeneous enrichment with cesium of embedded biological tissues sections. In such a specimen, containing already oxygen at a high concentration, the addition of cesium allows both positive and negative secondary ions to be studied with the highest sensitivity, using the same primary ion source.

  14. Adsorption Behaviour of Liquid 4He on Cesium Substrates

    OpenAIRE

    Iov, Valentin

    2004-01-01

    The aim of this thesis is to investigate the wetting properties of 4He on cesium substrates using optical and electrical methods. Due to the fact that the cesium substrates are deposited at low temperatures onto a thin silver underlayer, it is necessary firstly to study and understand the adsorption of helium on silver. The work presented here is structured as follows: some of the fundamental concepts on the theory of physisorbed films, such as van der Waals interaction, adsorption isotherms ...

  15. Phase 1 Methyl Iodide Deep-Bed Adsorption Tests

    Energy Technology Data Exchange (ETDEWEB)

    Nick Soelberg; Tony Watson

    2014-08-01

    Nuclear fission results in the production of fission products (FPs) and activation products including iodine-129, which could evolve into used fuel reprocessing facility off-gas systems, and could require off-gas control to limit air emissions to levels within acceptable emission limits. Research, demonstrations, and some reprocessing plant experience have indicated that diatomic iodine can be captured with efficiencies high enough to meet regulatory requirements. Research on the capture of organic iodides has also been performed, but to a lesser extent [Jubin 2012b]. Several questions remain open regarding the capture of iodine bound in organic compounds. Deep-bed methyl iodide adsorption testing has progressed according to a multi-laboratory methyl iodide adsorption test plan. This report summarizes the first phase of methyl iodide adsorption work performed according to this test plan using the deep-bed iodine adsorption test system at the Idaho National Laboratory (INL), performed during Fiscal Year (FY) 2013 and early FY-2014. Testing has been performed to address questions posed in the test plan, and followed the testing outline in the test plan. Tests established detection limits, developed procedures for sample analysis with minimal analytical interferences, and confirmed earlier results that show that the methyl iodide reacts when in contact with the AgZ sorbent, and not significantly in the gas flow upstream of the sorbent. The reaction(s) enable separation of the iodine from the organic moiety, so that the iodine can chemisorb onto the sorbent. The organic moiety can form other compounds, some of which are organic compounds that are detected and can be tentatively identified using GC-FID and GCMS. Test results also show that other gas constituents (NOx and/or H2O) can affect the methyl iodide reactions. With NOx and H2O present in the gas stream, the majority of uncaptured iodine exiting iodine-laden sorbent beds is in the form of I2 or HI, species that

  16. Introduction of extrinsic defects into mercuric iodide during processing

    International Nuclear Information System (INIS)

    Low temperature (4.2 K) photoluminescence spectroscopy (PL) measurements were performed on mercuric iodide (HgI2) crystals which were intentionally doped with copper or silver during KI etching. PL spectra obtained after these doping experiments show specific Cu and Ag features similar to those previously observed after deposition of Cu or Ag contacts on mercuric iodide crystals. The in-diffusion of Cu or Ag into bulk HgI2 has also been confirmed a few days after doping. This diffusion introduces new recombination centers in the material. This work suggests that the processing steps used to fabricate mercuric iodide nuclear detectors can lead to the introduction of new defects which are detrimental to detector performance

  17. Introduction of extrinsic defects into mercuric iodide during processing

    Science.gov (United States)

    Hung, C.-Y.; Bao, X. J.; Schlesinger, T. E.; James, R. B.; Cheng, A. Y.; Ortale, C.; van den Berg, L.

    1993-05-01

    Low-temperature photoluminescence spectroscopy (PL) measurements were performed on mercuric iodide (HgI2) crystals which were intentionally doped with copper or silver during KI etching. PL spectra obtained after these doping experiments show specific Cu and Ag features similar to those previously observed after deposition of Cu or Ag contacts on mercuric iodide crystals. The in-diffusion of Cu or Ag into bulk HgI2 has also been confirmed a few days after doping. This diffusion introduces new recombination centers in the material. This work suggests that the processing steps used to fabricate mercuric iodide nuclear detectors can lead to the introduction of new defects which are detrimental to detector performance.

  18. Modified purification of mercuric iodide for crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, N.L.; Ortale, C.; Schieber, M.M.; van den Berg, L.

    1988-01-01

    The standard procedure used in our laboratory to purify commercially available mercuric iodide consists of a sequence of steps: (1) repeated sublimation under continous evacuation, followed by (2) melting and recrystallization, and (3) a sublimation process in a closed tube. This paper describes a modification of the standard purification sequence by adding recrystallization of the mercuric iodide in hydrochloric acid. Leaching cation impurities out of mercuric iodide powder with hydrochloric acid has been practiced before by Zaletin, (V.M. Zaletin, I.H. Nozhiua, I.N. Fomin, V.T. Shystov, and N.V. Protasov, Atomic Energy 48, 169 (1980)). Our objective for the hydrochloric acid treatment was to remove nitrates and hydrocarbons which were interfering with the vapor transport during crystal growth. Results of the procedure are presented in terms of total carbon and selected ion content of the treated and untreated material. 13 refs., 8 figs., 3 tabs.

  19. Introduction of extrinsic defects into mercuric iodide during processing

    Energy Technology Data Exchange (ETDEWEB)

    Hung, C.; Bao, X.J.; Schlesinger, T.E. (Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)); James, R.B. (Advanced Materials Research Division, Sandia National Laboratories, Livermore, California 94550 (United States)); Cheng, A.Y.; Ortale, C.; van den Berg, L. (EG G Energy Measurements, Incorporated, Goleta, California 93116 (United States))

    1993-05-01

    Low temperature (4.2 K) photoluminescence spectroscopy (PL) measurements were performed on mercuric iodide (HgI[sub 2]) crystals which were intentionally doped with copper or silver during KI etching. PL spectra obtained after these doping experiments show specific Cu and Ag features similar to those previously observed after deposition of Cu or Ag contacts on mercuric iodide crystals. The in-diffusion of Cu or Ag into bulk HgI[sub 2] has also been confirmed a few days after doping. This diffusion introduces new recombination centers in the material. This work suggests that the processing steps used to fabricate mercuric iodide nuclear detectors can lead to the introduction of new defects which are detrimental to detector performance.

  20. Removal efficiency of organic iodide by silver-exchanged zeolite

    International Nuclear Information System (INIS)

    The removal efficiency of radioactive organic iodide generated under accident conditions at nuclear power plants or nuclear fuel cycle processes by silver-exchanged zeolite(AgX) was experimentally evaluated. First of all, adsorption capacities of various adsorbents such as activated carbon, zeocarbon and zeolite 13X as a function of process temperature were analyzed. Optimal operating condition for the removal of methyl iodide using AgX was suggested, based on silver-exchanged amounts and adsorption temperature. The effective removal efficiency of methyl iodide by AgX was obtained at conditions that the process temperature is in the range of 150 .deg. C to 200 .deg. C and the silver exchanged amount is about 10 wt%

  1. Adsorption of Gaseous Methyl Iodide by Active Carbons

    International Nuclear Information System (INIS)

    The impregnation of active carbons is known to be a useful means of improving the ability of these carbons to retain methyl iodide which might be formed during the accidental release of fission products from a reactor. Some basic work was done on both impregnated and unimpregnated materials, which involved: (a) the texture: (b) the reaction of Mel with the impregnants; (c) the adsorption of Mel on the carbons under dry and wet conditions at different temperatures. It was found that the carbons are highly microporous. A large part of this porosity disappears on impregnation with organic amine; These impregnants react chemically with the methyl iodide, which is thereby fixed on the carbon. For carbon which is impregnated with KI, a rapid exchange reaction takes place between the methyl iodide and KI under both dry and wet conditions. Consequently most of the iodine activity can be removed from the gas. (author)

  2. Standard free energy of formation of iron iodide

    Science.gov (United States)

    Khandkar, A.; Tare, V. B.; Wagner, J. B., Jr.

    1983-01-01

    An experiment is reported where silver iodide is used to determine the standard free energy of formation of iron iodide. By using silver iodide as a solid electrolyte, a galvanic cell, Ag/AgI/Fe-FeI2, is formulated. The standard free energy of formation of AgI is known, and hence it is possible to estimate the standard free energy of formation of FeI2 by measuring the open-circuit emf of the above cell as a function of temperature. The free standard energy of formation of FeI2 determined by this method is -38784 + 24.165T cal/mol. It is estimated that the maximum error associated with this method is plus or minus 2500 cal/mol.

  3. A novel peculiar mutation in the sodium/iodide symporter gene in spanish siblings with iodide transport defect.

    Science.gov (United States)

    Kosugi, Shinji; Okamoto, Hiroomi; Tamada, Aiko; Sanchez-Franco, F

    2002-08-01

    Previously, we reported two Spanish siblings with congenital hypothyroidism due to total failure of iodide transport. These were the only cases reported to date who received long-term iodide treatment over 10 yr. We examined the sodium/iodide symporter (NIS) gene of these patients. A large deletion was observed by long and accurate PCR using primers derived from introns 2 and 7 of the NIS gene. PCR-direct sequencing revealed a deletion of 6192 bases spanning from exon 3 to intron 7 and an inverted insertion of a 431-base fragment spanning from exon 5 to intron 5 of the NIS gene. The patients were homozygous for the mutation, and their mother was heterozygous. In the mutant, deletion of exons 3-7 was suggested by analysis using programs to predict exon/intron organization, resulting in an in-frame 182-amino acid deletion from Met(142) in the fourth transmembrane domain to Gln(323) in the fourth exoplasmic loop. The mutant showed no iodide uptake activity when transfected into COS-7 cells, confirming that the mutation was the direct cause of the iodide transport defect in these patients. Further, the mutant NIS protein was synthesized, but not properly expressed, on the cell surface, but was mostly accumulated in the cytoplasm, suggesting impaired targeting to the plasma membrane. PMID:12161518

  4. Dynamic optical modulation of an electron beam on a photocathode RF gun: Toward intensity-modulated radiation therapy (IMRT)

    International Nuclear Information System (INIS)

    In intensity-modulated radiation therapy (IMRT), the aim is to deliver reduced doses of radiation to normal tissue. As a step toward IMRT, we examined dynamic optical modulation of an electron beam produced by a photocathode RF gun. Images on photomasks were transferred onto a photocathode by relay imaging. The resulting beam was controlled by a remote mirror. The modulated electron beam maintained its shape on acceleration, had a fine spatial resolution, and could be moved dynamically by optical methods

  5. Dynamic optical modulation of an electron beam on a photocathode RF gun: Toward intensity-modulated radiation therapy (IMRT)

    Science.gov (United States)

    Kondoh, Takafumi; Kashima, Hiroaki; Yang, Jinfeng; Yoshida, Yoichi; Tagawa, Seiichi

    2008-10-01

    In intensity-modulated radiation therapy (IMRT), the aim is to deliver reduced doses of radiation to normal tissue. As a step toward IMRT, we examined dynamic optical modulation of an electron beam produced by a photocathode RF gun. Images on photomasks were transferred onto a photocathode by relay imaging. The resulting beam was controlled by a remote mirror. The modulated electron beam maintained its shape on acceleration, had a fine spatial resolution, and could be moved dynamically by optical methods.

  6. Seasonal variation of cesium 134 and cesium 137 in semidomestic reindeer in Norway after the Chernobyl accident

    Directory of Open Access Journals (Sweden)

    I.M. H. Eikelmann

    1990-09-01

    Full Text Available The Chernobyl accident had a great impact on the semidomestic reindeer husbandry in central Norway. Seasonal differences in habitat and diet resulted in large variations in observed radiocesium concentrations in reindeer after the Chernobyl accident. In three areas with high values of cesium-134 and cesium-137 in lichens, the main feed for reindeer in winter, reindeer were sampled every second month to monitor the seasonal variation and the decrease rate of the radioactivity. The results are based on measurements of cesium-134 and cesium-137 content in meat and blood and by whole-body monitoring of live animals. In 1987 the increase of radiocesium content in reindeer in Vågå were 4x from August to January. The mean reductions in radiocesium content from the winter 1986/87 to the winter 1987/88 were 32%, 50% and 43% in the areas of Vågå, Østre-Namdal and Lom respectively.

  7. Mercuric Iodide Anticoincidence Shield for Gamma-Ray Spectrometer

    Science.gov (United States)

    Hartsough, Neal; Iwanczyk, Jan

    2009-01-01

    A film-growth process was developed for polycrystalline mercuric iodide that creates cost-effective, large-area detectors for high-energy charged-particle detection. A material, called a barrier film, is introduced onto the substrate before the normal mercuric iodide film growth process. The barrier film improves the quality of the normal film grown and enhances the adhesion between the film and the substrate. The films grown using this improved technique were found to have adequate signal-to-noise properties so that individual high-energy charged -particle interactions could be distinguished from noise, and thus, could be used to provide an anticoincidence veto function as desired.

  8. Depolymerization of Lignin in Wood with Molecular Hydrogen Iodide

    OpenAIRE

    Shevchenko, Sergey M.

    2000-01-01

    Depolymerization of lignin in wood with hydrogen iodide in a non-polar solvent is a selective, high-yield reaction that releases a diiodide of potential synthetic value into the solution. Finely milled wood (Douglas-fir, spruce, aspen, and sugarcane), was suspended in CDCl3 and treated with dry hydrogen iodide in a NMR tube. The yields and composition of the chloroform-soluble monomeric lignin depolymerization products, 1,3-diiodo-1-(4-hydroxyaryl)propanes, originated from guaiacyl (G), syrin...

  9. Photocathodes based on semiconductor superlattices for streak tubes for IR region of 0.9-1.0 um

    Science.gov (United States)

    Nolle, Eduard L.

    1995-05-01

    A possibility of temporal analysis of picosecond light pulses in the IR region with the help of photocathodes based on semiconductor superlattices (SL) of type I (InP/InGaAs) with Schottky barrier is discussed. A new principle of avalanche photoelectron emission from such an SL at interband absorption of light is suggested. The principle is based on the electrons free length path increasing in a SL with narrow quantum wells under high electric field applied to the SL. The idea makes it possible to develop a new device - avalanche photocathode with internal amplification for the IR region of 0.9-2 micrometers and temporal resolution better than 30 ps. It is proposed to use doped as well as undoped SL as basis for photocathodes sensitive to the IR radiation in the range of up to 10 micrometers . The photoemission from such structures is caused by the intersubband absorption of light in quantum wells. The use of undoped SL greatly reduced the thermoemission current of the photocathode but requires additional excitation of the SL by light pulses with energy approximately corresponding to the band gap of the narrow band gap material of the SL. The temporal resolution of such photocathodes is supposed to be less than 30 ps. The conditions for the avalanche photoelectron emission obtaining are determined, and the SL parameters which meet the requirement of maximum quantum efficiency of the photocathode are calculated.

  10. Dose mapping experiments of refurbished cesium irradiator

    International Nuclear Information System (INIS)

    Full text: Cesium irradiator is a technology demonstration facility for irradiation of food commodities to achieve various purposes like control of sprouting in onion and potato, insect disinfestations of cereals and pulses, quarantine treatment of fresh fruits and vegetables and shelf life extension of perishable foods. The facility was installed in 1968 and recently refurbished with the new control console. The current source strength (137Cs) of the irradiator is 44.3 kCi. The real success of irradiation of food commodities lies in the adequate delivery of radiation dose to achieve the particular purpose of irradiation. Therefore, evaluation of dose distribution pattern in the product trays of the irradiation facility is of paramount importance. Two sets of dose mapping experiments of the product trays of the facility were carried out to find out the dose distribution profile and dose uniformity ratio. Reference standard dosimeter Fricke was used for the experiment. The standardized ionic concentrations of Fricke dosimeter are Ferrous Ammonium Sulphate (FeSO4(NH4)2SO4 6H2O ) - 1 mM, Sodium Chloride (NaCl) - 1 mM, Sulphuric acid (H2SO4) - 400 mM. The Optical Density (O.D) evaluation was carried out using Spectrophotometry with wave length of 304 nm. The dosimetry tray was partitioned into two planes namely bottom plane and top plane using card-board sheets. Polypropylene vials containing Fricke solution were prepared and fixed on the planes. Each plane was containing nine numbers of dosimeters. The product thickness was around 9 cm. The temperatures of irradiation and measurements were 30 deg C and 28 deg C respectively. The first set of experiment was intended to find out the dose distribution profile throughout the irradiation chamber. The dose rate at Dmin position was observed as 3.69 Gy/min with a poor Dose Uniformity Ratio (DUR) of 6.5. In order to improve the dose rate and DUR the second set of the experiment was carried out with modified product geometry

  11. A High-Gradient CW R Photo-Cathode Electron Gun for High Current Injectors

    Energy Technology Data Exchange (ETDEWEB)

    Robert Rimmer

    2005-05-01

    The paper describes the analysis and preliminary design of a high-gradient photo-cathode RF gun optimized for high current CW operation. The gun cell shape is optimized to provide maximum acceleration for the newly emitted beam while minimizing wall losses in the structure. The design is intended for use in future high-current high-power CW FELs but the shape optimization for low wall losses may be advantageous for other applications such as XFELs or Linear Colliders using high peak power low duty factor guns where pulse heating is a limitation. The concept allows for DC bias on the photocathode in order to repel ions and improve cathode lifetime.

  12. Effect of humid air exposure on photoemissive and structural properties of KBr thin film photocathode

    CERN Document Server

    Rai, R; Ghosh, N; Singh, B K

    2014-01-01

    We have investigated the influence of water molecule absorption on photoemissive and structural properties of potassium bromide (KBr) thin film photocathode under humid air exposure at relative humidity (RH) 65%. It is evident from photoemission measurement that the photoelectron yield of KBr photocathode is degraded exponentially with humid air exposed time. Structural studies of the "as-deposited" and "humid air aged" films reveal that there is no effect of RH on film's crystalline face centered cubic (fcc) structure. However, the average crystallite size of "humid air exposed film" KBr film has been increased as compared to "as-deposited". In addition, topographical properties of KBr film are also examined by means of scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) and it is observed that granular characteristic of film has been altered, even for short exposure to humid air.

  13. Heat enhancement of radiation resistivity of evaporated CsI, KI and KBr photocathodes

    CERN Document Server

    Tremsin, A S

    2000-01-01

    The photoemissive stability of as-deposited and heat-treated CsI, KI and KBr evaporated thin films under UV radiation is examined in this paper. After the deposition, some photocathodes were annealed for several hours at 90 deg. C in vacuum and their performance was then compared to the performance of non-heated samples. We observed that the post-evaporation thermal treatment not only increases the photoyield of CsI and KI photocathodes in the spectral range of 115-190 nm, but also reduces CsI, KI and KBr photocurrent degradation that occurs after UV irradiation. KBr evaporated layers appeared to be more radiation-resistant than CsI and KI layers. Post-deposition heat treatment did not result in any significant variation of KBr UV sensitivity.

  14. Reflective UV photocathodes with gas-phase electron extraction: Solid, liquid, and absorbed thin films

    Energy Technology Data Exchange (ETDEWEB)

    Seguinot, J.; Ypsilantis, T. (College de France, 75 - Paris (France)); Charpak, G.; Giomataris, Y.; Tischhauser, J. (European Organization for Nuclear Research, Geneva (Switzerland)); Peskov, V. (World Lab., Geneva (Switzerland))

    1990-11-15

    The photoemission quantum efficiency of reflective photocathodes in methane gas has been investigated in the spectral range between 140 and 250 nm. The spectral response of solid metals and CsI, as well as of liquid and solid TMAE film, have been measured. The high quantum efficiency of CsI (35% at 170 nm) makes it attractive for BaF{sub 2} or xenon scintillation detection. A BaF{sub 2} crystal coupled to an ionization chamber with a reflective CsI photocathode has been successfully tested. Adsorbed TMAE films can significantly increase the quantum yields of metal and CsI (to 46% at 170 nm), making them suitable for fast RICH and other applications. (orig.).

  15. In situ Observation of Dark Current Emission in a High Gradient RF Photocathode Gun

    CERN Document Server

    Shao, Jiahang; Baryshev, Sergey V; Chen, Huaibi; Conde, Manoel; Gai, Wei; Ha, Gwanghui; Jing, Chunguang; Shi, Jiaru; Wang, Faya; Wisniewski, Eric

    2016-01-01

    Undesirable electron field emission (a.k.a. dark current) in high gradient RF photocathode guns deteriorates the quality of photoemission current and limits the operational gradient. To improve the understanding of dark current emission, a high-resolution (~100 um) dark current imaging experiment has been performed in an L-band photocathode gun operating at ~100 MV/m of surface gradient. Dark current from the cathode has been observed to be dominated by several separated strong emitters. The field enhancement factor, beta, of selected regions on the cathode has been measured. The post scanning electron microscopy (SEM) and white light interferometer (WLI) surface examinations reveal the origins of ~75% strong emitters overlap with the spots where rf breakdown have occurred.

  16. In Situ Observation of Dark Current Emission in a High Gradient rf Photocathode Gun

    Science.gov (United States)

    Shao, Jiahang; Shi, Jiaru; Antipov, Sergey P.; Baryshev, Sergey V.; Chen, Huaibi; Conde, Manoel; Gai, Wei; Ha, Gwanghui; Jing, Chunguang; Wang, Faya; Wisniewski, Eric

    2016-08-01

    Undesirable electron field emission (also known as dark current) in high gradient rf photocathode guns deteriorates the quality of the photoemission current and limits the operational gradient. To improve the understanding of dark current emission, a high-resolution (˜100 μ m ) dark current imaging experiment has been performed in an L -band photocathode gun operating at ˜100 MV /m of surface gradient. Scattered strong emission areas with high current have been observed on the cathode. The field enhancement factor β of selected regions on the cathode has been measured. The postexaminations with scanning electron microscopy and white light interferometry reveal the origins of ˜75 % strong emission areas overlap with the spots where rf breakdown has occurred.

  17. Simulation study of the field emission and photoemission on metallic photocathodes. Emitted beam dynamics

    International Nuclear Information System (INIS)

    After a bibliographic research on field emission, photoemission and photo-field emission, the principle of the field equations (Poisson and Maxwell's) resolution by the finite element method is developed. The PRIAM program is shown to be efficient (adaptive mesh and refinement in the selected area). Several possibilities exist to reduce the effect of space charge such as the decrease of the laser pulse duration, the increase of the electric field and the application of a magnetic field. Calculations of the transverse emittance for a metallic plan photocathode have been made at different moments of the emission: transverse emittance is small at the beginning and at the end of the emission. It passes by a maximum which can be the origin of the electronic beam explosion for strong field. If a small emittance is wanted, one must illuminate the photocathode by a short pulsed laser

  18. Study on Quantum Efficiency Stability of Reflection-Mode GaN Negative Electronic Affinity Photocathode

    Directory of Open Access Journals (Sweden)

    Wei Liu

    2014-02-01

    Full Text Available The aim of this study is to analyze the decaying and recovering mechanism of the quantum efficiency for reflection-mode GaN NEA photocathode. One kind of reflection-mode GaN NEA photocathode is designed and grown in the laboratory. The quantum efficiency curves are obtained immediately and six hours later after the sample is fully activated, the quantum efficiency data at different wavelengths are acquired according to the two different quantum efficiency curves, Through the analysis of experiment result, the inner factors resulting in quantum efficiency decaying are discussed. Taking the factors into consideration, the method of supplementing Cs is applied in recovering the quantum efficiency, the quantum efficiency can be partly recovered. The reason that the quantum efficiency can not be completely recorvered is also anylized.

  19. Planar field emitters and high efficiency photocathodes based on ultrananocrystalline diamond

    Energy Technology Data Exchange (ETDEWEB)

    Sumant, Anirudha V.; Baryshev, Sergey V.; Antipov, Sergey P.

    2016-08-16

    A method of forming a field emitter comprises disposing a first layer on a substrate. The first layer is seeded with nanodiamond particles. The substrate with the first layer disposed thereon is maintained at a first temperature and a first pressure in a mixture of gases which includes nitrogen. The first layer is exposed to a microwave plasma to form a nitrogen doped ultrananocrystalline diamond film on the first layer, which has a percentage of nitrogen in the range of about 0.05 atom % to about 0.5 atom %. The field emitter has about 10.sup.12 to about 10.sup.14 emitting sites per cm.sup.2. A photocathode can also be formed similarly by forming a nitrogen doped ultrananocrystalline diamond film on a substrate similar to the field emitter, and then hydrogen terminating the film. The photocathode is responsive to near ultraviolet light as well as to visible light.

  20. 40 CFR 415.510 - Applicability; description of the potassium iodide production subcategory.

    Science.gov (United States)

    2010-07-01

    ... potassium iodide production subcategory. 415.510 Section 415.510 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Potassium Iodide Production Subcategory § 415.510 Applicability; description of the potassium iodide production subcategory. The provisions of this subpart are applicable to...

  1. 21 CFR 520.763c - Dithiazanine iodide and piperazine citrate suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Dithiazanine iodide and piperazine citrate... § 520.763c Dithiazanine iodide and piperazine citrate suspension. (a) Specifications. Each milliliter of the drug contains 69 milligrams of dithiazanine iodide and 83 milligrams of piperazine base...

  2. Magnetic field effects on the photocathode uniformity of Hamamatsu R7081 photomultiplier tubes

    International Nuclear Information System (INIS)

    We tested the effects of magnetic fields on a photomultiplier tube (PMT), namely, Hamamatsu R7081, with a large surface area photocathode. The output signals of the PMT were affected in such a way that the magnetic fields deflected photoelectrons to the first dynode. We measured the effects produced by the orientation of the PMT relative to the magnetic fields and the variations in the output signals with respect to the incident light positions in the magnetic fields.

  3. Characterization and development of photocathodes using laser induced time-of-flight spectroscopy

    Science.gov (United States)

    Ramirez-Homs, E.; Velazquez, D.; Spentzouris, L.; Terry, J.

    2011-10-01

    The emittance of a beam generated for use in particle accelerators is a critical performance parameter. In order to achieve peak performance, intrinsic transverse emittance on the order of 0.1mm-mrad is required. This initial emittance is about an order of magnitude lower than provided by today's sources. Several important efforts are being made to reach this lower emittance with cathode design modifications. A photocathode design study and implementation of experimental techniques for the characterization is proposed and discussed.

  4. A fast position sensitive photodetector based on a CsI reflective photocathode

    International Nuclear Information System (INIS)

    A fast detector was built for UV photon detection that depends on a CsI sensitized pad cathode. The rapidity of the detector is compared with that of a more classical chamber filled with photosensitive gases such as TEA or TMAE. Estimates of the quantum yield of the photocathode at 160 and 200 nm are given. The performances obtained make it a good photodetector candidate to be operated at high luminosity accelerators. (author) 7 refs., 19 figs

  5. Porous copper zinc tin sulfide thin film as photocathode for double junction photoelectrochemical solar cells.

    Science.gov (United States)

    Dai, Pengcheng; Zhang, Guan; Chen, Yuncheng; Jiang, Hechun; Feng, Zhenyu; Lin, Zhaojun; Zhan, Jinhua

    2012-03-21

    Porous copper zinc tin sulfide (CZTS) thin film was prepared via a solvothermal approach. Compared with conventional dye-sensitized solar cells (DSSCs), double junction photoelectrochemical cells using dye-sensitized n-type TiO(2) (DS-TiO(2)) as the photoanode and porous p-type CZTS film as the photocathode shows an increased short circuit current, external quantum efficiency and power conversion efficiency. PMID:22322239

  6. Significant Broadband Photocurrent Enhancement by Au-CZTS Core-Shell Nanostructured Photocathodes

    OpenAIRE

    Xuemei Zhang; Xu Wu; Anthony Centeno; Ryan, Mary P.; Alford, Neil M.; D. Jason Riley; Fang Xie

    2016-01-01

    Copper zinc tin sulfide (CZTS) is a promising material for harvesting solar energy due to its abundance and non-toxicity. However, its poor performance hinders their wide application. In this paper gold (Au) nanoparticles are successfully incorporated into CZTS to form Au@CZTS core-shell nanostructures. The photocathode of Au@CZTS nanostructures exhibits enhanced optical absorption characteristics and improved incident photon-to-current efficiency (IPCE) performance. It is demonstrated that u...

  7. Improvement of cesium retention in uranium dioxide by additional phases

    International Nuclear Information System (INIS)

    The objective of this study is to improve the cesium retention in nuclear fuel. A bibliographic survey indicates that cesium is rapidly released from uranium dioxide in an accident condition. At temperatures higher than 1500 deg C or in oxidising conditions, our experiments show the difficulty of maintaining cesium inside simulated fuel. Two ternary systems are potentially interesting for the retention of cesium and to reduce the kinetics of release from the fuel: Cs2O-Al2O3-SiO2 et Cs2O-ZrO2-SO2. The compounds CsAISi2O6 and Cs2ZrSi6O15 were studied from 1200 deg C to 2000 deg C by thermogravimetric analysis. The volumetric diffusion coefficients of cesium in these structures, in solid state as well as in liquid one, were measured. A fuel was sintered with (Al2O3 + SiO2) or (ZrO2 + SiO2) and the intergranular phase was characterized. In the presence of (Al2O3 + SiO2), the sintering is realized at 1610 deg C in H2. It is a liquid phase sintering. On the other end, with (ZrO2 + SiO2), the sintering is a low temperature one in oxidising atmosphere. Finally, cesium containing simulated fuels were produced with these additives. According to the effective diffusion coefficients that were measured, the additives improved the retention of cesium. We have predicted the improvement that could be hoped for in a nuclear reactor, depending on the dispersion of the intergranular additives, the temperature and the degree of oxidation of the UO2+x. We wait for a factor of 2 for x=0 and more than 8 for x=0.05, up to 2000 deg C. (author). 148 refs., 122 figs., 34 tabs

  8. State-of-the-art Pb photocathodes deposited by pulsed laser deposition

    International Nuclear Information System (INIS)

    In this article we present and discuss the current status of thin film Pb photocathodes deposited by pulsed laser deposition (PLD) with different laser parameters, such as laser fluence, wavelength or pulse duration. The PLD technique appears very efficient for the fabrication of pure Pb photocathodes, providing good adherence and respectable quantum efficiency. The films deposited on the picosecond and subpicosecond regimes are practically free of big droplets and fragments, whereas in the nanosecond regime their presence cannot be neglected. All the films present a granular structure and polycrystalline character with preferential orientation along the (111) crystalline planes, irrespective of the laser pulse duration or wavelength. The main results obtained from the photoemission performance of Pb thin films deposited by PLD demonstrate their chemical stability under vacuum conditions and respectable quantum efficiency with a maximum of 7.3×10−5 for films deposited on the subpicosecond regime. The photoemission properties confirm that Pb thin films deposited by PLD are a notable alternative for the fabrication of photocathodes for superconductive radio-frequency electron guns. - Highlights: • Lead samples were grown by Pulsed Laser Deposition at different laser parameters • All films present a granular morphology • Lead films grow preferentially along the 111 crystalline planes of the cubic net • A maximum quantum efficiency of 7.3 × 10-5 has been found

  9. Polarization Possibilities of Small Spin-Orbit Interaction in Strained-Superlattice Photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    2010-08-25

    Strained-superlattice photocathodes based on InGaP/GaAs were investigated. The photocathode performance is found highly dependent on the superlattice parameters. The electron confinement energy in superlattice appears important. The strained-superlattice structure based on GaAsP/GaAs, with a maximum polarization as high as 90% and more than 1% quantum efficiency, is presently the prime candidate for the ILC polarized electron photocathodes. A recent systematic study shows, however, that the peak polarization seems saturated even though the heavy-hole (HH) and light-hole (LH) band splitting is increased significantly, indicating that there is a material specific spin relaxation mechanism. It is widely accepted that the D'yakonov-Perel mechanism is the dominant spin relaxation mechanism in the III-V compound superlattice structures with a low p-doping ({le} 10{sup 17} cm{sup -3}), and that the spin relaxation may be reduced by choosing a material with a smaller spin-orbit interaction. As the spin-orbit interaction in phosphides is much smaller than in arsenides, strained-superlattice structure based on InGaP/GaAs were investigated. The computer code SPECCODE developed by Subashiev and Gerchikov has been used for calculating the band structures in superlattice.

  10. Dye-sensitized nickel(II)oxide photocathodes for tandem solar cell applications

    International Nuclear Information System (INIS)

    To date, nickel(II) oxide (NiO) is one of the few p-type semiconductors that has successfully been used for the construction of dye-sensitized photocathodes as well as tandem dye-sensitized solar cells. In this study we present a novel fabrication method for the preparation of mesoporous NiO films based on preformed NiO nanopowders. Critical properties such as pore-size distribution, crystallinity, and internal surface area of the resulting NiO films were controlled through the sintering process and optimized for their application as dye-sensitized photocathodes, resulting in a significantly increased photovoltaic performance, compared to earlier studies. A series of different sensitizers and electrolytes was scrutinized for their application in dye-sensitized NiO photocathodes. Despite its limited absorption range the dye coumarin 343 clearly outperforms other sensitizers used in this study. Values for short-circuit current densities of 2.13 mA cm-2 and overall energy conversion efficiencies of 0.033% under simulated sunlight (AM1.5, 1000 W m-2) are the highest values reported in literature so far

  11. Significant Broadband Photocurrent Enhancement by Au-CZTS Core-Shell Nanostructured Photocathodes.

    Science.gov (United States)

    Zhang, Xuemei; Wu, Xu; Centeno, Anthony; Ryan, Mary P; Alford, Neil M; Riley, D Jason; Xie, Fang

    2016-01-01

    Copper zinc tin sulfide (CZTS) is a promising material for harvesting solar energy due to its abundance and non-toxicity. However, its poor performance hinders their wide application. In this paper gold (Au) nanoparticles are successfully incorporated into CZTS to form Au@CZTS core-shell nanostructures. The photocathode of Au@CZTS nanostructures exhibits enhanced optical absorption characteristics and improved incident photon-to-current efficiency (IPCE) performance. It is demonstrated that using this photocathode there is a significant increase of the power conversion efficiency (PCE) of a photoelectrochemical solar cell of 100% compared to using a CZTS without Au core. More importantly, the PCE of Au@CZTS photocathode improved by 15.8% compared to standard platinum (Pt) counter electrode. The increased efficiency is attributed to plasmon resonance energy transfer (PRET) between the Au nanoparticle core and the CZTS shell at wavelengths shorter than the localized surface plasmon resonance (LSPR) peak of the Au and the semiconductor bandgap. PMID:26997140

  12. Heat load of a GaAs photocathode in an SRF electron gun

    Institute of Scientific and Technical Information of China (English)

    WANG Er-Dong; ZHAO Kui; J(o)rg 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.

  13. Development of a photo-cathode rf electron gun for ultra-short bunch generation

    International Nuclear Information System (INIS)

    The photocathode rf electron gun is a high brightness electron source because the initial electron bunch shape can be controlled by the cathode illuminating laser pulse and then the bunch is rapidly accelerated by the high gradient electric field in the rf gun cavity. The rf guns are widely used not only as a injector for large facility but also application researches. At Waseda University, I and collaborators have been developing an rf electron gun since 1999. We performed optimization of cavity structure, improvement of rf tuner and development of photocathode material, then we succeeded in operating 3.6 cell rf gun. In these backgrounds, I conceived a new type rf gun cavity structure for ultra-short electron bunch generation, named Energy-Chirping-Cell attached rf gun (ECC rf gun). Less than 100 fs (rms) bunch can be produced with 100 pC charge by this ECC rf gun in the simulation. Such a high peak current bunch has a possibility to apply for the coherent THz radiation source and single shot electron diffraction microscope. Encouraged by this successful simulation results, we manufactured an ECC rf gun and measured the bunch length at Waseda University. The experimental results showed a good agreement with simulation and we found that the bunch length from ECC rf gun was less than 500 fs (rms). In this paper, the introduction of the photocathode rf gun, principle and experimental results of ECC rf gun, and future prospective will be described. (author)

  14. Degradation of Methyl Iodide in Soil: Effects of Environmental Factors

    Science.gov (United States)

    Methyl iodide (MeI) is a promising alternative to the phased-out fumigant methyl bromide, and its environmental fate following soil fumigation is of great concern. Experiments were conducted to investigate the effect of various environmental factors on the degradation rate of MeI in soil. The chem...

  15. Enthalpies of potassium iodide dissolution in isopropanol aqueous solutions

    International Nuclear Information System (INIS)

    At 298.15 K in air-tight microcalorimeter with isothermal shell enthalpies of potassium iodide dissolution in water and in water-isopropyl alcohol mixtures (5,10,20,30,50 and 70 mol.%) are measured. Dissolution enthalpies during infinite dilution in the above-mentioned mixed solvents are determined

  16. Iodide volatility under condition relevant to PWR steam generator faults

    International Nuclear Information System (INIS)

    The evaluation of iodine volatility during steam generator tube rupture (SGTR) is hampered by three factors: (i) lack of suitable plant data under fault conditions, (ii) lack of experimental data (mainly due to the difficulty of performing experiments under the conditions required) and (iii) uncertainty in theoretical methods to extrapolate experimental data to the required conditions. This report summarises methods of estimating the volatility of hydrogen iodide and iodide salts at the required conditions of temperature and pressure. A thermodynamic method has been used to estimate HI volatility and the density correlation method for iodide salt volatility. It is assumed throughout that it is more conservative to predict higher volatility. Consideration is given to two explanations of experiments carried out at Oak Ridge National Laboratory (ORNL) on the influence of boric acid concentration and pH on the volatility of radioiodine ostensibly under SGTR conditions: (i) the results have been interpreted in terms of reactions involving volatility of iodide salt/ion-pairs and complexation by boric acid in the gas phase and (ii) the possibility is explored that the observed results are due to the influence of oxidation leading to the formation of much more volatile iodine species. (author)

  17. Detection of soft X-rays with NEA III-V photocathodes. [Negative Electron Affinity X-ray detector for astronomy

    Science.gov (United States)

    Bardas, D.; Kellogg, E.; Murray, S.; Enck, R., Jr.

    1978-01-01

    A description is presented of the results of tests on an X-ray photomultiplier containing a negative electron affinity (NEA) photocathode. This device makes it possible to investigate the response of the NEA photocathode to X-rays of various energies. The obtained data provide a basis for the determination of the photoelectron yield and energy resolution of the considered photocathode as a function of energy in the range from 0.8 to 3 keV. The investigation demonstrates the feasibility of using an NEA III-V photocathode for the detection of soft X-rays.

  18. Cesium and strontium in Black Sea macroalgae

    International Nuclear Information System (INIS)

    The trace level of metals and particularly radioactive ones should be monitored to evaluate the transfer along the trophic chain, assess the risk for biota and can be used for global changes assessment. Plants respond rapidly to all changes in the ecosystem conditions and are widely used as indicators and predictors for changes in hydrology and geology. In this work we represent our successful development and applications of a methodology for monitoring of stable and radioactive strontium and cesium in marine biota (Black Sea algae's). In case of radioactive release they are of high interest. We use ED-XRF, gamma spectrometers and LSC instrumentation and only 0.25 g sample. Obtained results are compared with those of other authors in same regions. The novelty is the connection between the radioactive isotopes and their stable elements in algae in time and space scale. All our samples were collected from Bulgarian Black Sea coast. - Highlights: • An extraction chromatography method for radiochemical separation of Sr and Cs. • Assessment of Sr and Cs accumulation capacity of six Black Sea macroalgae species. • Connection between the isotopes and their stable elements content in algae. • Assessment of Sr and Cs content in ecosystems along the Bulgarian coast

  19. Cesium-137 levels detected in Georgia otters

    International Nuclear Information System (INIS)

    Beginning in the 1940's and continuing through the 50's and early 60's, nuclear devices were tested by aerial detonation in the United States and other countries around the world. Cesium-137 (137Cs) is one of the most important radionuclide by-products due to its abundance and slow decay (30-year half-life). The uptake of 137Cs in animal tissue is the result of its similarity to potassium. The somatic and genetic effects of 137Cs, along with its effect on reproductive cells, can pose great hazards to wildlife species. A reported buildup of 137Cs in white-tailed deer in the lower coastal plain of Georgia during the 1960's was followed by a gradual decline during the 1970's. Although numerous studies have involved terrestrial mammals of Georgia, few have involved aquatic mammals such as the river otter. With continued atmospheric testing by some foreign countries and the increased use of nuclear power as an energy source, there is a need for continued monitoring of radionuclides in wildlife to ascertain the quality of the environment. This study was initiated as part of an overall study of environmental pollutants in the river otter of Georgia and deals with analysis of the 137Cs accumulations in this species

  20. FY-2015 Methyl Iodide Deep-Bed Adsorption Test Report

    Energy Technology Data Exchange (ETDEWEB)

    Soelberg, Nicholas Ray [Idaho National Lab. (INL), Idaho Falls, ID (United States); Watson, Tony Leroy [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-09-30

    Nuclear fission produces fission and activation products, including iodine-129, which could evolve into used fuel reprocessing facility off-gas systems, and could require off-gas control to limit air emissions to levels within acceptable emission limits. Deep-bed methyl iodide adsorption testing has continued in Fiscal Year 2015 according to a multi-laboratory methyl iodide adsorption test plan. Updates to the deep-bed test system have also been performed to enable the inclusion of evaporated HNO3 and increased NO2 concentrations in future tests. This report summarizes the result of those activities. Test results showed that iodine adsorption from gaseous methyl iodide using reduced silver zeolite (AgZ) resulted in initial iodine decontamination factors (DFs, ratios of uncontrolled and controlled total iodine levels) under 1,000 for the conditions of the long-duration test performed this year (45 ppm CH3I, 1,000 ppm each NO and NO2, very low H2O levels [3 ppm] in balance air). The mass transfer zone depth exceeded the cumulative 5-inch depth of 4 bed segments, which is deeper than the 2-4 inch depth estimated for the mass transfer zone for adsorbing I2 using AgZ in prior deep-bed tests. The maximum iodine adsorption capacity for the AgZ under the conditions of this test was 6.2% (6.2 g adsorbed I per 100 g sorbent). The maximum Ag utilization was 51%. Additional deep-bed testing and analyses are recommended to (a) expand the data base for methyl iodide adsorption and (b) provide more data for evaluating organic iodide reactions and reaction byproducts for different potential adsorption conditions.

  1. FY-2015 Methyl Iodide Deep-Bed Adsorption Test Report

    International Nuclear Information System (INIS)

    Nuclear fission produces fission and activation products, including iodine-129, which could evolve into used fuel reprocessing facility off-gas systems, and could require off-gas control to limit air emissions to levels within acceptable emission limits. Deep-bed methyl iodide adsorption testing has continued in Fiscal Year 2015 according to a multi-laboratory methyl iodide adsorption test plan. Updates to the deep-bed test system have also been performed to enable the inclusion of evaporated HNO3 and increased NO2 concentrations in future tests. This report summarizes the result of those activities. Test results showed that iodine adsorption from gaseous methyl iodide using reduced silver zeolite (AgZ) resulted in initial iodine decontamination factors (DFs, ratios of uncontrolled and controlled total iodine levels) under 1,000 for the conditions of the long-duration test performed this year (45 ppm CH3I, 1,000 ppm each NO and NO2, very low H2O levels [3 ppm] in balance air). The mass transfer zone depth exceeded the cumulative 5-inch depth of 4 bed segments, which is deeper than the 2-4 inch depth estimated for the mass transfer zone for adsorbing I2 using AgZ in prior deep-bed tests. The maximum iodine adsorption capacity for the AgZ under the conditions of this test was 6.2% (6.2 g adsorbed I per 100 g sorbent). The maximum Ag utilization was 51%. Additional deep-bed testing and analyses are recommended to (a) expand the data base for methyl iodide adsorption and (b) provide more data for evaluating organic iodide reactions and reaction byproducts for different potential adsorption conditions.

  2. Uptake of cesium ions by human erythrocytes and perfused rat heart: a cesium-133 NMR study

    Energy Technology Data Exchange (ETDEWEB)

    Davis, D.G.; Murphy, E.; London, R.E.

    1988-05-17

    Cesium-133 NMR studies have been carried out on suspended human erythrocytes and on perfused rat hearts in media containing CsCl. The resulting spectra exhibit two sharp resonances, arising from intra-and extracellular Cs/sup +/, separated in chemical shift by 1.0-1.4 ppm. Thus, intra- and extracellular resonances are easily resolved without the addition of paramagnetic shift reagents required to resolve resonance of the other alkali metal ions. Spin-lattice relaxation times in all cases are monoexponential and significantly shorter (3-4 times) for the intracellular component. When corrections are made for the pulse repetition rate, the total intensity of the intracellular and extracellular Cs/sup +/ resonances in erythrocytes is conserve, implying total observability of the intracellular pool. The uptake of Cs/sup +/ by erythrocytes occurs at approximately one-third the reported rate for K/sup +/ and was reduced by a factor of 2 upon addition of ouabain to the sample. These results indicate that /sup 133/Cs NMR is a promising tool for studying the distribution and transport of cesium ions in biological systems and, in some cases such as uptake by cellular Na,K-ATPase, for analysis of K/sup +/ ion metabolism.

  3. Micro-PIXE evaluation of radioactive cesium transfer in contaminated soil samples

    International Nuclear Information System (INIS)

    Highlights: • There are radioactively contaminated soils having a radioactive cesium transfer of 0.01. • Micro-PIXE analysis has revealed an existence of phosphorus in a contaminated soil. • Radioactive cesium captured by phosphorus compound would be due to radioactive transfer. -- Abstract: Micro-PIXE analysis has been performed on two soil samples with high cesium activity concentrations. These soil samples were contaminated by fallout from the accident at Fukushima Daiichi Nuclear Power Plant. One exhibits a radioactive cesium transfer of ∼0.01, and the other shows a radioactive cesium transfer of less than 0.001, even though both samples have high cesium activity concentrations exceeding 10,000 Bq/kg. X-ray spectra and elemental images of the soil samples revealed the presence of chlorine, which can react with cesium to produce an inorganic soluble compound, and phosphorus-containing cesium-capturable organic compounds

  4. A fundamental study on cesium migration to sodium at low temperature

    International Nuclear Information System (INIS)

    Our experiment study aims to understand the behavior of cesium in severe accident of sodium cooled fast breeder reactor, especially cesium migration rate to sodium. In past study, exact migration rate of cesium to sodium has not been reported because of difficulty of the cesium-sodium interfacial area evaluations of gas bubble. In this study, we developed a pool-type experimental apparatus which can simplify the shape of interfacial area, and measured cesium migration rate in a low temperature range of 200degC to 300degC. The cesium migration rates obtained under the condition that the cesium mixed argon gas flow is the same temperature with sodium vary in the range of 10-3 - 10-1 mol/m2min and increase with increasing the system temperature. The difference of cesium migration rates between non-oxidized sodium surface and oxidized sodium surface is also clearly observed. (author)

  5. Viscosity and crystallization mechanism of cesium loaded iron phosphate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Kitheri, E-mail: joskit@igcar.gov.in [Chemistry Group, IGCAR, Kalpakkam 603 102 (India); Kutty, K.V. Govindan [Chemistry Group, IGCAR, Kalpakkam 603 102 (India); Goswami, M.C. [National Metallurgical Laboratory, Jamshedpur 831 007 (India); Rao, P.R. Vasudeva [Chemistry Group, IGCAR, Kalpakkam 603 102 (India)

    2014-07-01

    Highlights: • Melt viscosity of cesium loaded iron phosphate glasses is measured and reported for the first time. • Viscosity – temperature followed Arrhenius model. • Activation energy of viscous flow is strongly correlated to glass transition temperature of the glasses. • Process of crystallization of cesium loaded glass by approximation-free kinetic method to understand the mechanism. • Cesium loaded IPG and IPG shows bulk crystallization mechanism. - Abstract: This paper describes the melt viscosity behaviour and the crystallization mechanism of a series of iron phosphate glasses. High temperature viscosity measurements were carried out on pristine iron phosphate glass and a series of cesium loaded iron phosphate glasses in order to understand the effect of addition of Cs{sub 2}O on viscosity of iron phosphate glasses. Activation energy of viscous flow was estimated from the experimental data by applying Arrhenius model of viscosity–temperature relationship. Activation energy of viscous flow is observed to be strongly correlated to glass transition temperature of these glasses. Fragility of iron phosphate and cesium loaded iron phosphate glass systems were also evaluated in region of high temperature. Crystallization of these glasses was studied using thermal analysis techniques. Temperature integral approximation free method was utilized to evaluate the kinetic parameters such as activation energy of crystallization (E{sub c}) and Avrami exponent (n). The value of Avrami exponent ‘n’ obtained showed that the glasses under present study crystallize via bulk crystallization mechanism, i.e., nucleation and three dimensional growth.

  6. Cesium corrosion process in Fe–Cr steel

    International Nuclear Information System (INIS)

    A cesium corrosion out-pile test was performed to Fe–Cr steel in a simulated fuel pin environment. In order to specify the corrosion products, the corroded area was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A cesium corrosion process in Fe–Cr steel was successfully developed proceeding from both experimental results and thermochemical consideration. The corroded area was mainly formed by Fe layer and Fe depleted oxidized layer. The Fe depleted oxidized layer was formed by Cr0.5Fe0.5 and Cr2O3. The presumed main corrosion reactions were 2Cr+2/3 O2→Cr2O3(ΔG650°C=-894.1kJ/mol) and Cr23C6+46Cs+46O2→23Cs2CrO4+6C(ΔG650°C=-25018.1kJ/mol). Factors of these reactions are chromium, carbon, oxygen and cesium. Therefore, cesium corrosion progression must be dependent on the chromium content, carbon content in the steel, the supply rate of oxygen and temperature which correlated with the diffusion rate of cesium and oxygen into the specimen

  7. Viscosity and crystallization mechanism of cesium loaded iron phosphate glasses

    International Nuclear Information System (INIS)

    Highlights: • Melt viscosity of cesium loaded iron phosphate glasses is measured and reported for the first time. • Viscosity – temperature followed Arrhenius model. • Activation energy of viscous flow is strongly correlated to glass transition temperature of the glasses. • Process of crystallization of cesium loaded glass by approximation-free kinetic method to understand the mechanism. • Cesium loaded IPG and IPG shows bulk crystallization mechanism. - Abstract: This paper describes the melt viscosity behaviour and the crystallization mechanism of a series of iron phosphate glasses. High temperature viscosity measurements were carried out on pristine iron phosphate glass and a series of cesium loaded iron phosphate glasses in order to understand the effect of addition of Cs2O on viscosity of iron phosphate glasses. Activation energy of viscous flow was estimated from the experimental data by applying Arrhenius model of viscosity–temperature relationship. Activation energy of viscous flow is observed to be strongly correlated to glass transition temperature of these glasses. Fragility of iron phosphate and cesium loaded iron phosphate glass systems were also evaluated in region of high temperature. Crystallization of these glasses was studied using thermal analysis techniques. Temperature integral approximation free method was utilized to evaluate the kinetic parameters such as activation energy of crystallization (Ec) and Avrami exponent (n). The value of Avrami exponent ‘n’ obtained showed that the glasses under present study crystallize via bulk crystallization mechanism, i.e., nucleation and three dimensional growth

  8. The diffusion of cesium, strontium, and europium in silicon carbide

    Science.gov (United States)

    Dwaraknath, S. S.; Was, G. S.

    2016-08-01

    A novel multi-layer diffusion couple was used to isolate the diffusion of strontium, europium and cesium in SiC without introducing radiation damage to SiC and at concentrations below the solubility limit for the fission products in SiC. Diffusion occurred by both bulk and grain boundary pathways for all three fission products between 900∘ C and 1 ,300∘ C. Cesium was the fastest diffuser below 1 ,100∘ C and the slowest above this temperature. Strontium and europium diffusion tracked very closely as a function of temperature for both bulk and grain boundary diffusion. Migration energies ranged from 1.0 eV to 5.7 eV for bulk diffusion and between 2.2 eV and 4.7 eV for grain boundary diffusion. These constitute the first measurements of diffusion of cesium, europium, and strontium in silicon carbide, and the magnitude of the cesium diffusion coefficient supports the premise that high quality TRISO fuel should have minimal cesium release.

  9. Dissociative excitation of cesium atom upon e-CsOH collisions

    International Nuclear Information System (INIS)

    The process of dissociative excitation of cesium atom in collisions with mono-kinetic molecules of cesium hydroxide is studied. It is established that behaviour of dissociative excitations the cesium atom in spectral series corresponds of to the grade dependence of cross sections on the main quantum number of the upper level. The values of constants, characterizing the behaviour of cross sections in the eight spectral series of the cesium atom are determined

  10. Formation of organic iodides from containment paint ingredients caused by gamma irradiation

    International Nuclear Information System (INIS)

    The formation of volatile alkyl iodides other than methyl iodide during a serious nuclear reactor accident may have radiological significance. The hypothesis that radioactive alkyl iodides, other than methyl iodide, could form from paint solvents under the conditions of a serious nuclear accident in light water reactors (under boiling water reactor (BWR) and pressurised water reactor (PWR) conditions) was tested using stable elemental iodine, a gamma irradiator and gas chromatography equipment. It was found that methyl and isopropyl iodides were formed from the texanol ester, which is used in many modern water-based paints. Methyl, ethyl, propyl and butyl iodides were formed from a hydrocarbon solvent (white spirit) commonly used in paint products used in the past. These results suggest that further work on the formation and behaviour of the higher alkyl iodides (containing more than one carbon atom) under the conditions of a serious nuclear accident is justified. (author)

  11. A novel mutation in the sodium/iodide symporter gene in the largest family with iodide transport defect.

    Science.gov (United States)

    Kosugi, S; Bhayana, S; Dean, H J

    1999-09-01

    We previously reported nine children with an autosomally recessive form of congenital hypothyroidism due to an iodide transport defect in a large Hutterite family with extensive consanguinity living in central Canada. Since the original report, we have diagnosed congenital hypothyroidism by newborn TSH screening in 9 additional children from the family. We performed direct sequencing of the PCR products of each NIS (sodium/iodide symporter) gene exon with flanking introns amplified from genomic DNA extracted from peripheral blood cells of the patients. We identified a novel NIS gene mutation, G395R (Gly395-->Arg; GGA-->AGA), in 10 patients examined in the present study. All of the parents tested were heterozygous for the mutation, suggesting that the patients were homozygous. The mutation was located in the 10th transmembrane helix. Expression experiments by transfection of the mutant NIS complimentary DNA into COS-7 cells showed no perchlorate-sensitive iodide uptake, confirming that the mutation is the direct cause of the iodide transport defect in these patients. A patient who showed an intermediate saliva/serum technetium ratio (14.0; normal, > or = 20) and was considered to have a partial or less severe defect in the previous report (IX-24) did not have a NIS gene mutation. It is now possible to use gene diagnostics of this unique NIS mutation to identify patients with congenital hypothyroidism due to an iodide transport defect in this family and to determine the carrier state of potential parents for genetic counseling and arranging rapid and early diagnosis of their infants. PMID:10487695

  12. Sorption of cesium and uranium to Feldspar

    International Nuclear Information System (INIS)

    Within safety assessment studies, for nuclear waste disposal in deep geologic formations, calculation for the migration of radionuclides through the geosphere are often carried out with models taking sorption into account. In the past 8 years the insight grew that other physico-chemical processes, besides sorption, could affect migration behaviour. While the currently used transport models were being improved taking either linear or non-linear sorption into account, the coupling of geochemical and transport models came into scope. In spite of these developments models which are still based on the sorption theory are frequently applied in studying migration behaviour of radionuclides. This is caused by the necessity of making preliminary pronouncements, while coupled models are still in stage of development and thermodynamic data are very limited available. Therefore one has to obtain insight in the reliability of the models based on the sorption theory. within the sorption database there is a lack of knowledge about mineralogy, composition of the fluid and the experimental conditions underlying the data. Therefore the Expert Group on geochemical Modelling supported by the Finnish proposal in order to obtain insight in the possible deviation of the sorption coefficients that can be estimated from experiments performed with standard samples, fluid composition and experimental conditions. Nine laboratories from OECD membership countries took part in this intercalibration study. In the framework of the Dutch safety assessment studies the Dutch National Institute of Public health and Environmental protection (RIVM) has decided to participate in this exercise. In this report the results are presented of sorption experiments for cesium and natural Uranium to Feldspar. (H.W.). 4 refs.; 1 fig.; 7 tabs

  13. Cesium in the Savannah River Site environment

    International Nuclear Information System (INIS)

    Cesium in the Savannah River Site Environment is published as a part of the Radiological Assessment Program (RAP). It is the fourth in a series of eight documents on individual radioisotopes released to the environment as a result of Savannah River Site (SRS) operations. The earlier documents describe the environmental consequences of tritium, iodine, and uranium. Documents on plutonium, strontium, carbon, and technetium will be published in the future. These are dynamic documents and current plans call for revising and updating each one on a two-year schedule.Radiocesium exists in the environment as a result of above-ground nuclear weapons tests, the Chernobyl accident, the destruction of satellite Cosmos 954, small releases from reactors and reprocessing plants, and the operation of industrial, medical, and educational facilities. Radiocesium has been produced at SRS during the operation of five production reactors. Several hundred curies of 137Cs was released into streams in the late 50s and 60s from leaking fuel elements. Smaller quantities were released from the fuel reprocessing operations. About 1400 Ci of 137Cs was released to seepage basins where it was tightly bound by clay in the soil. A much smaller quantity, about four Ci. was released to the atmosphere. Radiocesium concentration and mechanisms for atmospheric, surface water, and groundwater have been extensively studied by Savannah River Technology Center (SRTC) and ecological mechanisms have been studied by Savannah River Ecology Laboratory (SREL). The overall radiological impact of SRS releases on the offsite maximum individual can be characterized by total doses of 033 mrem (atmospheric) and 60 mrem (liquid), compared with a dose of 12,960 mrem from non-SRS sources during the same period of time. Isotope 137Cs releases have resulted in a negligible risk to the environment and the population it supports

  14. Cesium in the Savannah River Site environment

    Energy Technology Data Exchange (ETDEWEB)

    Carlton, W.H.; Bauer, L.R.; Evans, A.G.; Geary, L.A.; Murphy, C.E. Jr.; Pinder, J.E.; Strom, R.N.

    1992-03-01

    Cesium in the Savannah River Site Environment is published as a part of the Radiological Assessment Program (RAP). It is the fourth in a series of eight documents on individual radioisotopes released to the environment as a result of Savannah River Site (SRS) operations. The earlier documents describe the environmental consequences of tritium, iodine, and uranium. Documents on plutonium, strontium, carbon, and technetium will be published in the future. These are dynamic documents and current plans call for revising and updating each one on a two-year schedule.Radiocesium exists in the environment as a result of above-ground nuclear weapons tests, the Chernobyl accident, the destruction of satellite Cosmos 954, small releases from reactors and reprocessing plants, and the operation of industrial, medical, and educational facilities. Radiocesium has been produced at SRS during the operation of five production reactors. Several hundred curies of {sup 137}Cs was released into streams in the late 50s and 60s from leaking fuel elements. Smaller quantities were released from the fuel reprocessing operations. About 1400 Ci of {sup 137}Cs was released to seepage basins where it was tightly bound by clay in the soil. A much smaller quantity, about four Ci. was released to the atmosphere. Radiocesium concentration and mechanisms for atmospheric, surface water, and groundwater have been extensively studied by Savannah River Technology Center (SRTC) and ecological mechanisms have been studied by Savannah River Ecology Laboratory (SREL). The overall radiological impact of SRS releases on the offsite maximum individual can be characterized by total doses of 033 mrem (atmospheric) and 60 mrem (liquid), compared with a dose of 12,960 mrem from non-SRS sources during the same period of time. Isotope {sup 137}Cs releases have resulted in a negligible risk to the environment and the population it supports.

  15. Cesium in the Savannah River Site environment

    Energy Technology Data Exchange (ETDEWEB)

    Carlton, W.H.; Bauer, L.R.; Evans, A.G.; Geary, L.A.; Murphy, C.E. Jr.; Pinder, J.E.; Strom, R.N.

    1992-03-01

    Cesium in the Savannah River Site Environment is published as a part of the Radiological Assessment Program (RAP). It is the fourth in a series of eight documents on individual radioisotopes released to the environment as a result of Savannah River Site (SRS) operations. The earlier documents describe the environmental consequences of tritium, iodine, and uranium. Documents on plutonium, strontium, carbon, and technetium will be published in the future. These are dynamic documents and current plans call for revising and updating each one on a two-year schedule.Radiocesium exists in the environment as a result of above-ground nuclear weapons tests, the Chernobyl accident, the destruction of satellite Cosmos 954, small releases from reactors and reprocessing plants, and the operation of industrial, medical, and educational facilities. Radiocesium has been produced at SRS during the operation of five production reactors. Several hundred curies of [sup 137]Cs was released into streams in the late 50s and 60s from leaking fuel elements. Smaller quantities were released from the fuel reprocessing operations. About 1400 Ci of [sup 137]Cs was released to seepage basins where it was tightly bound by clay in the soil. A much smaller quantity, about four Ci. was released to the atmosphere. Radiocesium concentration and mechanisms for atmospheric, surface water, and groundwater have been extensively studied by Savannah River Technology Center (SRTC) and ecological mechanisms have been studied by Savannah River Ecology Laboratory (SREL). The overall radiological impact of SRS releases on the offsite maximum individual can be characterized by total doses of 033 mrem (atmospheric) and 60 mrem (liquid), compared with a dose of 12,960 mrem from non-SRS sources during the same period of time. Isotope [sup 137]Cs releases have resulted in a negligible risk to the environment and the population it supports.

  16. Spins and magnetic moments of rubidium and cesium nuclides far from stability

    International Nuclear Information System (INIS)

    Previous studies at ISOLDE have concerned spins and magnetic moments of neutron-deficient rubidium and cesium isotopes. Here, the main results obtained, and, in the case of cesium, new moment measurements are briefly discussed also the results from measurements on neutron-rich nuclides of rubidium and cesium. (orig./AH)

  17. Environmental application of cesium-137 irradiation technology: Sludges and foods

    Science.gov (United States)

    Sivinski, Jacek S.

    Several activities have been undertaken to investigate and implement the use of the military byproduct cesium-137 in ways which benefit mankind. Gamma radiation from cesium-137 has been shown to be effective in reducing pathogens in sewage sludge to levels where reuse of the material in public areas meets current regulatory criteria for protection of public health. Food irradiation at doses of 10 kGy or less have been found by international expert committees to be wholesome and safe for human consumption. Cesium-137 can be used as a means of enhancing particular properties of various food commodities by means of sterilization, insect disinfestation, delayed senescence and ripening, and sprout inhibition. This paper discusses the U.S. Department of Energy Beneficial Uses Program research and engineering history, as well as current activities and future plans, relating to both sewage sludge and food irradiation.

  18. Environmental application of cesium-137 irradiation technology: sludges and foods

    International Nuclear Information System (INIS)

    Several activities have been undertaken to investigate and implement the use of the military byproduct cesium-137 in ways which benefit mankind. Gamma radiation from cesium-137 has been shown to be effective in reducing pathogens in sewage sludge to levels where reuse of the material in public areas meets current regulatory criteria for protection of public health. Food irradiation at doses of 10 kGy or less have been found by international expert committees to be wholesome and safe for human consumption. Cesium-137 can be used as a means of enhancing particular properties of various food commodities by means of sterilization, insect disinfestation, delayed senescence and ripening, and sprout inhibition. This paper discusses the U.S. Department of Energy Beneficial Uses Program research and engineering history, as well as current activities and future plans, relating to both sewage sludge and food irradiation. (author)

  19. Dating of mine waste in lacustrine sediments using cesium-137

    Science.gov (United States)

    Rember, W. C.; Erdman, T. W.; Hoffmann, M. L.; Chamberlain, V. E.; Sprenke, K. F.

    1993-11-01

    For over a century Medicine Lake in northern Idaho has received heavy-metal-laden tailings from the Coeur d'Alene mining district. Establishing the depositional chronology of the lake bottom sediments provides information on the source and rate of deposition of the tailings. Cesium-137, an isotope produced in the atmosphere by nuclear bomb tests, was virtually absent in the environment prior to 1951, but reached its apex in 1964. Our analysis of cesium-137 in the sediments of Medicine Lake revealed that 14 cm of fine-grained tailings were deposited in the lake from 1951 to 1964 and tailing deposition downstream was greatly reduced by the installation of tailings dams in the district in 1968. Cesium-137 analysis is accomplished by a fairly simple gamma-ray counting technique and should be a valuable tool for analyzing sedimentation in any lacustrine environment that was active during the 1950s and 1960s.

  20. Cesium 137 in oils and plants from Guatemala

    International Nuclear Information System (INIS)

    Since 1990 the project of radioactive and environmental contamination started in Guatemala. Studies about the radioactive contamination levels are made within the framework of this project. Cesium-137 has been an interest radionuclide, because it is a fission product released to the environment by the use of nuclear weapons and nuclear power plants accidents. The sampling consisted in collection of soil and grass in 20 provinces of Guatemala, one point by province, and it was made in 1990. The cesium-137 concentration in the samples, was determined by gamma spectrometry, using an hyper pure germanium detector. The results show the presence of radioactive contamination in soil and grass due to cesium-137, at levels that might be considered as normal. The levels found are not harmful for human health, and its importance is the fact that can be used as reference levels for the environmental radioactivity monitoring in Guatemala

  1. Study of radiatively sustained cesium plasmas for solar energy conversion

    Science.gov (United States)

    Palmer, A. J.; Dunning, G. J.

    1980-01-01

    The results of a study aimed at developing a high temperature solar electric converter are reported. The converter concept is based on the use of an alkali plasma to serve as both an efficient high temperature collector of solar radiation as well as the working fluid for a high temperature working cycle. The working cycle is a simple magnetohydrodynamic (MHD) Rankine cycle employing a solid electrode Faraday MHD channel. Research milestones include the construction of a theoretical model for coupling sunlight in a cesium plasma and the experimental demonstration of cesium plasma heating with a solar simulator in excellent agreement with the theory. Analysis of a solar MHD working cycle in which excimer laser power rather than electric power is extracted is also presented. The analysis predicts a positive gain coefficient on the cesium-xenon excimer laser transition.

  2. On the compartmental modeling of cesium migration in soils

    International Nuclear Information System (INIS)

    The prediction of the migration of radionuclides in soil following deposition after a nuclear accident is important for both external dose and plant uptake prediction. In this paper, the validity conditions of compartment models for cesium migration in soils are investigated. A compartment model is derived from a diffusion-convection model. The model considers free and bound cesium compartments and is applied to measured profiles of 137Cs of undisturbed soil in Northern Greece. It is concluded that the rate of cesium transfer must vary linearly with depth and that from measured equilibrium profiles, the ratios of model parameters can be determined but not the parameters themselves. This model is applied to measured profiles of 137Cs in soil due to wet deposition following the Chernobyl accident

  3. Cooled Transmission-Mode NEA-Photocathode with a Band-Graded Active Layer for High Brightness Electron Source

    Science.gov (United States)

    Jones, L. B.; Rozhkov, S. A.; Bakin, V. V.; Kosolobov, S. N.; Militsyn, B. L.; Scheibler, H. E.; Smith, S. L.; Terekhov, A. S.

    2009-08-01

    A Free-Electron Laser (FEL) places many exacting demands on a Negative Electron Affinity (NEA) photocathode, such as the need for an ultra-fast response time, low energy spread for emitted electrons, high quantum efficiency (Q.E.) and a high average photocurrent. However, these key requirements are conflicting, and cannot be fulfilled by conventional photocathode design. For example, to achieve ˜10 ps response time, the photocathode active layer should be thinned to ˜100-150 nm, but this thickness is insufficient to provide near-complete absorption of light with hv≈ɛg so high Q.E. cannot be achieved. Complete optical absorption and high Q.E. can be obtained using a thin active layer at higher photon energies, but this generates photoelectrons with excess kinetic energy within the semiconductor. These photoelectrons do not thermalise in a thin active layer, so yield a broad energy distribution in the emitted electrons. Moreover, cooling of the conventional semiconductor photocathode structure is ineffective due to its fragility, so it cannot be pressed firmly to a heat sink to attain good thermal contact. Consequently, the maximum CW photocurrent is limited to a few miiliamps. The goal of our work is to develop a new design of NEA-photocathode which is optimised for FEL applications.

  4. Nanostructured Silicon Photocathodes for Solar Water Splitting Patterned by the Self-Assembly of Lamellar Block Copolymers.

    Science.gov (United States)

    Shen, Lang; He, Chunlin; Qiu, Jing; Lee, Sung-Min; Kalita, Abinasha; Cronin, Stephen B; Stoykovich, Mark P; Yoon, Jongseung

    2015-12-01

    We studied a type of nanostructured silicon photocathode for solar water splitting, where one-dimensionally periodic lamellar nanopatterns derived from the self-assembly of symmetric poly(styrene-block-methyl methacrylate) block copolymers were incorporated on the surface of single-crystalline silicon in configurations with and without a buried metallurgical junction. The resulting nanostructured silicon photocathodes with the characteristic lamellar morphology provided suppressed front-surface reflection and increased surface area, which collectively contributed to the enhanced photocatalytic performance in the hydrogen evolution reaction. The augmented light absorption in the nanostructured silicon directly translated to the increase of the saturation current density, while the onset potential decreased with the etching depth because of the increased levels of surface recombination. The pp(+)-silicon photocathodes, compared to the n(+)pp(+)-silicon with a buried solid-state junction, exhibited a more pronounced shift of the current density-potential curves upon the introduction of the nanostructured surface owing to the corresponding increase in the liquid/silicon junction area. Systematic studies on the morphology, optical properties, and photoelectrochemical characteristics of nanostructured silicon photocathodes, in conjunction with optical modeling based on the finite-difference time-domain method, provide quantitative description and optimal design rules of lamellar-patterned silicon photocathodes for solar water splitting. PMID:26575400

  5. Thallous and cesium halide materials for use in cryogenic applications

    International Nuclear Information System (INIS)

    Certain thallous and cesium halides, either used alone or in combination with other ceramic materials, are provided in cryogenic applications such as heat exchange material for the regenerator section of a closed-cycle cryogenic refrigeration section, as stabilizing coatings for superconducting wires, and as dielectric insulating materials. The thallous and cesium halides possess unusually large specific heats at low temperatures, have large thermal conductivities, are nonmagnetic, and are nonconductors of electricity. They can be formed into a variety of shapes such as spheres, bars, rods, or the like and can be coated or extruded onto substrates or wires. (author)

  6. Selective chemical binding enhances cesium tolerance in plants through inhibition of cesium uptake

    Science.gov (United States)

    Adams, Eri; Chaban, Vitaly; Khandelia, Himanshu; Shin, Ryoung

    2015-03-01

    High concentrations of cesium (Cs+) inhibit plant growth but the detailed mechanisms of Cs+ uptake, transport and response in plants are not well known. In order to identify small molecules with a capacity to enhance plant tolerance to Cs+, chemical library screening was performed using Arabidopsis. Of 10,000 chemicals tested, five compounds were confirmed as Cs+ tolerance enhancers. Further investigation and quantum mechanical modelling revealed that one of these compounds reduced Cs+ concentrations in plants and that the imidazole moiety of this compound bound specifically to Cs+. Analysis of the analogous compounds indicated that the structure of the identified compound is important for the effect to be conferred. Taken together, Cs+ tolerance enhancer isolated here renders plants tolerant to Cs+ by inhibiting Cs+ entry into roots via specific binding to the ion thus, for instance, providing a basis for phytostabilisation of radiocesium-contaminated farmland.

  7. Selective chemical binding enhances cesium tolerance in plants through inhibition of cesium uptake

    DEFF Research Database (Denmark)

    Adams, Eri; Chaban, Vitaly; Khandelia, Himanshu; Shin, Ryoung

    2015-01-01

    High concentrations of cesium (Cs(+)) inhibit plant growth but the detailed mechanisms of Cs(+) uptake, transport and response in plants are not well known. In order to identify small molecules with a capacity to enhance plant tolerance to Cs(+), chemical library screening was performed using...... Arabidopsis. Of 10,000 chemicals tested, five compounds were confirmed as Cs(+) tolerance enhancers. Further investigation and quantum mechanical modelling revealed that one of these compounds reduced Cs(+) concentrations in plants and that the imidazole moiety of this compound bound specifically to Cs......(+). Analysis of the analogous compounds indicated that the structure of the identified compound is important for the effect to be conferred. Taken together, Cs(+) tolerance enhancer isolated here renders plants tolerant to Cs(+) by inhibiting Cs(+) entry into roots via specific binding to the ion thus, for...

  8. Mercuric iodide (HgI2) growth for nuclear detectors

    Science.gov (United States)

    Schnepple, W.

    1982-01-01

    The purpose of this investigation is to grow more-perfect mercuric iodide crystals in a low-gravity environment by taking advantage of diffusion-controlled growth conditions and by avoiding the problem of strain dislocations produced by the crystal's weight. This crystal has considerable practical importance as a sensitive gamma-ray detector and energy spectrometer that can operate at ambient temperature, as compared to presently available detectors that must be cooled to near liquid nitrogen temperatures. However, the performance of mercuric iodide crystals only rarely approaches the expected performance, presumably because some of the free electrical charges produced within the crystal are not collected at the electrodes, but instead remain trapped or immobilized at crystal defects. An efficient high atomic number semiconductor detector capable of operating at room temperature utilizing single HgI2 crystals offers a greater potential than existing detector technology.

  9. Development of the semiconductor detector of lead iodide

    International Nuclear Information System (INIS)

    Lead iodide (PbI2) crystal is one of the most promising semiconductor detectors to be operated at room temperature. It is a semiconductor with a wide band gap energy and high atomic numbers. The preparation of a detector crystal consists of the purification of starting material, in quartz ampoules, by zone refining technique and growth of crystals by Bridgman method. The ability to obtain high purity crystals containing a relatively low number of defects and the physical-chemistry characterization are necessary pre-requisites for the production of good quality radiation detectors. This work reports the lead iodide monocrystal purification and growth methods to obtain those crystals with appropriate characteristics for their application as radiation detectors. (author)

  10. Behaviour of organic iodides under pwr accident conditions

    International Nuclear Information System (INIS)

    Laboratory experiments were performed to study the behaviour of radioactive methyl iodide under PWR loss-of-coolant conditions. The pressure relief equipment consisted of an autoclave for simulating the primary circuit and of an expansion vessel for simulating the conditions after a rupture in the reactor coolant system. After pressure relief, the composition of the CH3sup(127/131)I-containing steam-air mixture within the expansion vessel was analysed at 80 0C over a period of 42 days. On the basis of the values measured and of data taken from the literature, both qualitative and quantitative assessments have been made as to the behaviour of radioactive methyl iodide in the event of loss-of-coolant accidents. (author)

  11. (1,2-Dicarba-closo-dodecaboranyltrimethylmethanaminium iodide

    Directory of Open Access Journals (Sweden)

    Jong-Dae Lee

    2011-08-01

    Full Text Available The title compound, [1-(CH33NCH2-1,2-C2B10H11]+·I− or C6H22B10N+·I−, was obtained by the reaction of (1,2-dicarba-closo-dodecaboranyldimethylmethanamine with methyl iodide. The asymmetric unit contains two iodide anions and two (o-carboranyltetramethylammonium cations. The bond lengths and angles in the carborane cage are within normal ranges, but the N—Cmethylene—Ccage angle is very large [120.2 (2°] because of repulsion between the carborane and tetramethylammonium units. In the crystal, ions are linked through C—H...I hydrogen bonds.

  12. Enhanced iodide sequestration by 3-biphenyl-5,6-dihydroimidazo 2,1-b thiazole in sodium/iodide sym-porter (NIS)-expressing cells

    International Nuclear Information System (INIS)

    The ability of the sodium/iodide sym-porter (NIS) to take up iodide has long provided the basis for cyto-reductive gene therapy and cancer treatment with radio-iodide. One of the major limitations of this approach is that radio-iodide retention in NIS-expressing cells is not sufficient for their destruction. We identified and characterized a small organic molecule capable of increasing iodide retention in HEK293 cells permanently transfected with human NIS cDNA (hNIS-HEK293) and in the rat thyroid-derived cell line FRTL-5. In the presence of 3-biphenyl-4'-yl-5,6-dihydroimidazo[2,1-b)thiazole (ISA1), the transmembrane iodide concentration gradient was increased up to 4.5-fold. Our experiments indicate that the imidazo-thiazole derivative acts either by inhibiting anion efflux mechanisms, or by promoting the relocation of iodide into subcellular compartments. This new compound is not only an attractive chemical tool to investigate the mechanisms of iodide flux at the cellular level, but also opens promising perspectives in the treatment of cancer after NIS gene transfer. (authors)

  13. Recovery of thallium-activated sodium iodide detectors

    International Nuclear Information System (INIS)

    A method for recovery and treatment of sodium iodide thallium activated detectors, NaI(Tl), is described. Special techniques of polishing and mounting in a dry environment (relative humidity less than 10%) are applied. The resolution was determined and compared with that obtained with a new detector and the results showed that a typical 3' phi x 3' recovered detector had a performance very similar to that of a new one. (Author)

  14. Nuclear detonation, thyroid cancer and potassium iodide prophylaxis

    OpenAIRE

    Viroj Wiwanitkit

    2011-01-01

    The recent nuclear disaster at Japan has raised global concerns about effects of radioactive leakage in the environment, associated hazards, and how they can be prevented. In this article, we have tried to explain about the guidelines laid down by World Health Organization for a potassium iodide prophylaxis following a nuclear disaster, and its mechanism of action in preventing thyroid cancer. Data was collected mainly from the studies carried out during the Chernobyl disaster of Russia in 19...

  15. Lead iodide perovskite light-emitting field-effect transistor

    OpenAIRE

    Chin, Xin Yu; Cortecchia, Daniele; Yin, Jun; Bruno, Annalisa; Soci, Cesare

    2015-01-01

    Despite the widespread use of solution-processable hybrid organic–inorganic perovskites in photovoltaic and light-emitting applications, determination of their intrinsic charge transport parameters has been elusive due to the variability of film preparation and history-dependent device performance. Here we show that screening effects associated to ionic transport can be effectively eliminated by lowering the operating temperature of methylammonium lead iodide perovskite (CH3NH3PbI3) field-eff...

  16. Radiative efficiency of lead iodide based perovskite solar cells

    OpenAIRE

    Kristofer Tvingstedt; Olga Malinkiewicz; Andreas Baumann; Carsten Deibel; Snaith, Henry J.; Vladimir Dyakonov; Bolink, Henk J.

    2015-01-01

    The maximum efficiency of any solar cell can be evaluated in terms of its corresponding ability to emit light. We herein determine the important figure of merit of radiative efficiency for Methylammonium Lead Iodide perovskite solar cells and, to put in context, relate it to an organic photovoltaic (OPV) model device. We evaluate the reciprocity relation between electroluminescence and photovoltaic quantum efficiency and conclude that the emission from the perovskite devices is dominated by a...

  17. Ionic transport in hybrid lead iodide perovskite solar cells

    OpenAIRE

    Eames, Christopher; Frost, Jarvist Moore; Piers R. F. Barnes; O'Regan, Brian C.; Walsh, Aron; Islam, M. Saiful

    2015-01-01

    Solar cells based on organic–inorganic halide perovskites have recently shown rapidly rising power conversion efficiencies, but exhibit unusual behaviour such as current–voltage hysteresis and a low-frequency giant dielectric response. Ionic transport has been suggested to be an important factor contributing to these effects; however, the chemical origin of this transport and the mobile species are unclear. Here, the activation energies for ionic migration in methylammonium lead iodide (CH3NH...

  18. Structural insight into iodide uptake by AFm phases.

    Science.gov (United States)

    Aimoz, Laure; Wieland, Erich; Taviot-Guého, Christine; Dähn, Rainer; Vespa, Marika; Churakov, Sergey V

    2012-04-01

    The ability of cement phases carrying positively charged surfaces to retard the mobility of (129)I, present as iodide (I(-)) in groundwater, was investigated in the context of safe disposal of radioactive waste. (125)I sorption experiments on ettringite, hydrotalcite, chloride-, carbonate- and sulfate-containing AFm phases indicated that calcium-monosulfate (AFm-SO(4)) is the only phase that takes up trace levels of iodide. The structures of AFm phases prepared by coprecipitating iodide with other anions were investigated in order to understand this preferential uptake mechanism. X-ray diffraction (XRD) investigations showed a segregation of monoiodide (AFm-I(2)) and Friedel's salt (AFm-Cl(2)) for I-Cl mixtures, whereas interstratifications of AFm-I(2) and hemicarboaluminate (AFm-OH-(CO(3))(0.5)) were observed for the I-CO(3) systems. In contrast, XRD measurements indicated the formation of a solid solution between AFm-I(2) and AFm-SO(4) for the I-SO(4) mixtures. Extended X-ray absorption fine structure spectroscopy showed a modification of the coordination environment of iodine in I-CO(3) and in I-SO(4) samples compared to pure AFm-I(2). This is assumed to be due to the introduction of stacking faults in I-CO(3) samples on one hand and due to the presence of sulfate and associated space-filling water molecules as close neighbors in I-SO(4) samples on the other hand. The formation of a solid solution between AFm-I(2) and AFm-SO(4), with a short-range mixing of iodide and sulfate, implies that AFm-SO(4) bears the potential to retard (129)I. PMID:22376086

  19. Growth of mercuric iodide single crystals from dimethylsulfoxide

    Science.gov (United States)

    Carlston, Richard C.

    1976-07-13

    Dimethylsulfoxide is used as a solvent for the growth of red mercuric iodide (HgI.sub.2) crystals for use in radiation detectors. The hygroscopic property of the solvent allows controlled amounts of water to enter into the solvent phase and diminish the large solubility of HgI.sub.2 so that the precipitating solid collects as well-defined euhedral crystals which grow into a volume of several cc.

  20. New applications for the zinc iodide-osmium tetroxide technique.

    OpenAIRE

    Dağdeviren, A; ALP, H.; Ors, U

    1994-01-01

    The zinc iodide-osmium tetroxide (ZIO) fixation/staining method was applied for neurocytological studies and also to examine several other tissue samples including epidermal Langerhans cells, blood and bone marrow cells and lymphoid tissue. Although precise specificity cannot be attributed to the staining reaction, interesting staining patterns for different cell types were observed by using one of the ZIO staining solutions. The significance of ZIO positivity is briefly discussed.

  1. Transport of Iodide Ion in Compacted Bentonite Containing Ag2O - 12111

    International Nuclear Information System (INIS)

    Observations of the transport of iodide through compacted bentonite containing Ag2O as additive and that without additive were made. Compacted bentonite samples with densities of 1.41 g/cm3 and 1.60 g/cm3 were used in the experiment. The amount of Ag2O added to the compacted bentonite was in the range of 0.0064 ∼ 0.0468 wt/wt%. Two diffusion solutions were used: one in which iodide ion was dissolved in demineralized water (pure iodide solution), and one in which iodide ion was dissolved in 0.1 M NaCl solution (0.1 M NaCl-iodide solution). Experimental results confirmed that iodide ion was transported by the diffusion process in the compacted bentonite containing Ag2O as well as in the compacted bentonite without Ag2O. The time-lag of diffusion of iodide ion in the compacted bentonite containing Ag2O is larger than that in the compacted bentonite without Ag2O. The increase of the time-lag of diffusion was observed in pure iodide ion solution as well as in 0.1 M NaCl-iodide solution. The apparent diffusion coefficient of iodide ion in the compacted bentonite containing Ag2O was smaller than in the compacted bentonite without Ag2O. The effective diffusion coefficient decreased as the amount of Ag2O in the compacted bentonite increased. (authors)

  2. The sodium iodide symporter: its implications for imaging and therapy

    International Nuclear Information System (INIS)

    The sodium iodide symporter (NIS) is an intrinsic plasma membrane glycoprotein that mediates the active transport of iodide in the thyroid gland and a number of extrathyroidal tissues, in particular lactating mammary gland. In addition to its key function in thyroid physiology, NIS-mediated iodide accumulation allows diagnostic thyroid scintigraphy as well as therapeutic radioiodine application in benign and malignant thyroid disease. NIS therefore represents one of the oldest targets for molecular imaging and therapy. Based on the effective administration of radioiodine that has been used for over 60 years in the management of follicular cell-derived thyroid cancer, cloning and characterization of the NIS gene has paved the way for the development of a novel cytoreductive gene therapy strategy based on targeted NIS expression in thyroidal and nonthyroidal cancer cells followed by therapeutic application of 131I or alternative radionuclides, including 188Re and 211At. In addition, the possibility of direct and non-invasive imaging of functional NIS expression by 123I- and 99mTc-scintigraphy or 124I-PET-imaging allows the application of NIS as a novel reporter gene. In conclusion, the dual role of NIS as diagnostic and therapeutic gene and the detection of extra-thyroidal endogenous NIS expression in breast cancer open promising perspectives in nuclear medicine and molecular oncology for diagnostic and therapeutic application of NIS outside the thyroid gland. (orig.)

  3. Synthesis and evaluation of iodide uptake inhibitors in thyroid gland

    International Nuclear Information System (INIS)

    This work was intended to discover small organic molecules acting as iodide uptake inhibitors in thyroid cells. These compounds can indeed be derivatized into biochemical probes for further characterization of proteins involved in iodide transport mechanisms. On the long term, these inhibitors also appear as attractive drug candidates for treatment of thyroid pathologies or radioprotection against iodine isotopes. A similar strategy was adopted for both of the two inhibitor families. First, we synthesized a chemical library of around 100 analogues; we measured their IC50 against iodide uptake in FRTL-5 cells to get structure-activity relationships. Absolute configuration of stereo-genic centers was also investigated, and a preferential stereochemistry was found to be responsible for activity. From this basis, around twenty 'second-generation' analogues were synthesized by combining fragments contributing to biological activity. Biological evaluation indicated that nine were very potent inhibitors, with IC50 ≤ 6 nM and satisfying physicochemical properties required for drug candidates. Finally, one photoactivatable biotinylated probe was developed in each family and used for photoaffinity labeling. Several specifically labeled proteins are still under identification and constitute new potential therapeutic targets. (author)

  4. Growth and luminescence properties of undoped strontium iodide crystals

    International Nuclear Information System (INIS)

    Highlights: •Undoped strontium iodide crystal with high optical quality was grown using the Bridgman method. •Metal impurities distribution throughout crystal boule was determined and discussed. •Reliable optical transmission spectrum of undoped strontium iodide crystal was obtained. •Luminescence properties for broad emission band at room temperature were studied. •The room temperature broad emission band was proposed to have an origin of self-trapped exciton. -- Abstract: High optical quality undoped strontium iodide crystal grown by using the Bridgman method was characterized. Crystal growth process was described and growth technical parameters were discussed. Impurity analysis of raw materials and as-grown crystal boule indicates that it is feasible to pre-purify the raw material by zone refining or recrystallization. Luminescence properties were studied by photoluminescence, radioluminescence, fluorescence decay time, and scintillation time response. As-grown crystal shows good optical transmittance with wavelength concerned and is transparent for its large Stoke shift, 540 nm peaked broad emission, which has a fluorescence decay time 494 ns at 300 K. The broad emission range from 350 nm to 800 nm was tentatively speculated to be intrinsic and have an origin of self-trapped exciton

  5. Evaluation of the amperex 56 TVP photomultiplier. [characteristics: photoelectron time spread, anode pulse amplitude and photocathode sensing area

    Science.gov (United States)

    Lo, C. C.; Leskovar, B.

    1976-01-01

    Characteristics were measured for the Amperex 56 TVP 42 mm-diameter photomultiplier. Some typical photomultiplier characteristics-such as gain, dark current, transit and rise times-are compared with data provided. Photomultiplier characteristics generally not available such as the single photoelectron time spread, the relative collection efficiency, the relative anode pulse amplitude as a function of the voltage between the photocathode and focusing electrode, and the position of the photocathode sensing area were measured and are discussed for two 56 TVP's. The single photoelectron time spread, the relative collection efficiency, and the transit time difference as a function of the voltage between photocathode and focusing electrode were also measured and are discussed, particularly with respect to the optimization of photomultiplier operating conditions for timing applications.

  6. Constructing n-ZnO@Au heterogeneous nanorod arrays on p-Si substrate as efficient photocathode for water splitting

    Science.gov (United States)

    Bao, Zhijia; Xu, Xiaoyong; Zhou, Gang; Hu, Jingguo

    2016-07-01

    Developing ingenious heterostructure photoelectrodes in photoelectrochemical (PEC) cells to both harvest more solar photons and steer desired charge separation flow is a prerequisite challenge for PEC water splitting. Herein a hierarchical p-Si/n-ZnO@Au heterostructure was constructed via large-area growth of one-dimensional (1D) ZnO nanorod arrays (NRAs) on p-Si substrate followed by decorating with Au nanoparticles (NPs), which exhibited remarkably improved photocathode activity for PEC water splitting relative to the bare Si and Si/ZnO NRAs photocathodes. In addition to structural superiorities of 1D NRAs, a series of dynamic contributions from complementary band-gap structure, p–n heterojunctions and Au plasmon towards photon harvesting and charge separation were demonstrated to ensure a well-steered collection of photoelectrons at the exposed ZnO nanorods and Au NPs, enabling substantially improved photocathode performance.

  7. Constructing n-ZnO@Au heterogeneous nanorod arrays on p-Si substrate as efficient photocathode for water splitting.

    Science.gov (United States)

    Bao, Zhijia; Xu, Xiaoyong; Zhou, Gang; Hu, Jingguo

    2016-07-29

    Developing ingenious heterostructure photoelectrodes in photoelectrochemical (PEC) cells to both harvest more solar photons and steer desired charge separation flow is a prerequisite challenge for PEC water splitting. Herein a hierarchical p-Si/n-ZnO@Au heterostructure was constructed via large-area growth of one-dimensional (1D) ZnO nanorod arrays (NRAs) on p-Si substrate followed by decorating with Au nanoparticles (NPs), which exhibited remarkably improved photocathode activity for PEC water splitting relative to the bare Si and Si/ZnO NRAs photocathodes. In addition to structural superiorities of 1D NRAs, a series of dynamic contributions from complementary band-gap structure, p-n heterojunctions and Au plasmon towards photon harvesting and charge separation were demonstrated to ensure a well-steered collection of photoelectrons at the exposed ZnO nanorods and Au NPs, enabling substantially improved photocathode performance. PMID:27306198

  8. An Experimental Study of the Quantum Efficiency and Topology of Copper Photocathode Due to Plasma Cleaning and Etching

    CERN Document Server

    Palmer, Denni T; Kirby, Robert

    2005-01-01

    We have developed an experimental research program to the study of the photoemission properties of copper photocathodes as a function of various plasma cleaning/etching parameters. The quantum efficiency, QE, and topology, Ra and Rpp, of Copper Photocathodes, , will be monitored while undergoing plasma cleaning/etching process. We will monitor the QE as a function of time for the various test coupons while we optimize the various plasma processing parameters. In addition, surface topology, will be studied to determine the suitability of the cleaning/etching process to produce an acceptable photoemitter. We propose to use two metrics in the evaluation of the plasma cleaning process as an acceptable cleaning method for metallic photocathodes, Quantum Efficiency versus Wavelength and Surface roughness: Ra and Rpp represent the Average Roughness and Peak to Peak Roughness parameters, respectively.

  9. A polarized photoluminescence study of strained layer GaAs photocathodes

    International Nuclear Information System (INIS)

    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

  10. A polarized photoluminescence study of strained layer GaAs photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    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 {approximately}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, {approx}78 K and {approx}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.

  11. Initial simulation studies of electron bunch from RF photocathode gun of DLS project

    International Nuclear Information System (INIS)

    A Free Electron Laser based compact light source, named as Delhi Light Source (DLS), is under construction at IUAC. The facility aims to produce THz and Infrared radiation by injecting high quality electron beam into an undulator magnet. In addition, intense X-rays can be obtained by bombarding the electron beam with a laser beam by the method of Inverse Compton scattering. The complete project is divided in to three phases. The first phase of the project aims at generating pre-bunched electron beam from a 2.6 cell room temperature RF photocathode gun operating at 2.86 GHz. The bunch train with a repetition rate of 10 Hz, will consist of 2, 4, 8 or 16 micro-bunches . By varying the separation between the microbunches, the tuning of the THz radiation produced from the undulator magnet can be performed. Metal photocathode will be used initially to generate the electron micro-bunches to keep the temporal spread small. This paper describes the simulation studies using ASTRA code for optimization of various parameters from RF photocathode gun upto the undulator entrance. The multiple parameters are optimized one at a time, for a single electron bunch, ensuring the desired output parameter is contained within tolerable limits. Beam optics simulation with multi electron bunches are also studied with variable number of 2, 4 and 8 micro-bunches with different micro-bunch spacing. In the simulation studies, attention is paid to optimize the fundamental beam parameters like the transverse emittance, energy spread, transverse/longitudinal beam size etc. The paper describes the simulation results with single and multi-electron bunches. (author)

  12. Large Photocathode Photodetectors Using Photon Amplification and Phase-Space Compression

    CERN Document Server

    Carrio, Alex; Greener, Kevin; McGuiness, Sean; Podrasky, Victor; Sullivan, John; Winn, David R; Bilki, Burak; Onel, Yasar

    2014-01-01

    We describe a simple technique to both amplify incident photons and compress their angular x area phase space. These Optical Compressor Amplifier Tubes (OCA Tube) use techniques analogous to image intensifiers, using vacuum photocathodes to detect photons as converted to photoelectrons, amplify the photons via photoelectron bombardment of fast scintillators, and compress the optical phase space onto optical fibers, so that small, high gain photodetectors, like miniature PMT or SiPM, can be used to detect photons from large areas, at comparatively low cost. The properties of and benefits of OCA tubes are described.

  13. Modular magnet power supplies for CUTE-FEL beamline and photocathode gun based linac

    International Nuclear Information System (INIS)

    DC current-controlled power supplies are developed for application in CUTE-FEL beamline at BP and FEL Lab, RRCAT and photocathode gun based linac being set up at Radiation and Photochemistry Division, Bhabha Atomic Research Centre. In all, 29 power supplies for various magnets are developed. Power supply design is standardized for output ratings up to 20 A and 325 W on a standard 6U card with full-function feedback control and local-remote operation interface electronics on the same card. Individual power supply cards can be configured for series-parallel operation to increase output power rating. (author)

  14. Research of photo-cathode RF gun and superconducting accelerator experiment

    International Nuclear Information System (INIS)

    Photo-cathode superconducting accelerator experiment system includes Nd: YAG mode-locked laser, Cs2Te cathode, 2 + 1/2 RF gun, L band 3.5 MW microwave source, 1.3 GHz superconducting cavity, 500 W continuous microwave source, coaxial input coupler, 4.2 K cryostat, helium liquefied system, control system, beam diagnosis system, and vacuum system. In June 2001, the experiment of this system was carried out in CAEP. The electron beam energy gained in the superconducting cavity is 0.58 MeV, and the micro-pulse current is 0.1A

  15. Study of multi-alkali photocathode to realize high quantum efficiency and high endurance

    International Nuclear Information System (INIS)

    CsK2Sb multi-alkali photocathode is considered to be one of the best candidate of the high brightness electron source of the advanced electron accelerator such as Energy Recovery Linac (ERL) and Free Electron Laser (FEL) because of the excellent features: high quantum efficiency, long lifetime, and driven by green laser. We developed an evaporation system to study the cathode performances, such as quantum efficiency (QE) and the cathode lifetime. CsK2Sb thin film cathode was successfully made in this chamber. The cathode lifetime was measured and the result suggests that the cathode has an extremely long lifetime regarding to the extracted charge density. (author)

  16. 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.

  17. Quantum yield measurements of photocathodes illuminated by pulsed ultraviolet laser radiation

    International Nuclear Information System (INIS)

    The electron quantum yields from polycrystalline lanthanum hexaboride and barium irradiated by near ultraviolet laser excitation have been determined. These measurements show that the quantum yields from these materials are dependent on the processing and previous history of the photocathode material. For lanthanum hexaboride, a yield of 7 x 10-6 with 337 nm irradiation has been achieved. For barium, a yield of 1 x 10-6 has been measured with excitation at 308 nm. These results are discussed and future plans are outlined. 4 refs., 4 figs

  18. Software Tools for the Analysis of the Photocathode Response of Photomultiplier Vacuum Tubes

    OpenAIRE

    Fabbri, R.

    2013-01-01

    The central institute of electronics (ZEA-2) in the Forschungszentrum Juelich (FZJ) has developed a system to scan the response of the photocathode of photomultiplier tubes (PMT). The PMT sits tight on a supporting structure, while a blue light emitting diode is moved along its surface by two stepper motors, spanning both the x and y coordinates. All the system is located in a light-tight box made by wood. A graphical software was developed in-situ to perform the scan operations under differe...

  19. Generation of femtosecond electron bunches using a laser photocathode RF gun linac

    International Nuclear Information System (INIS)

    Electron beams with pulse durations of picoseconds and femtoseconds have been applied to the accelerator physics application such as free electron lasers and laser-Comptom x-rays. The ultrashort electron bunches are also key element in time-resolved measurements including pulse radiolysis to improve the time resolution of the measurements. In this study, femtosecond electron bunches were generated using a laser photocathode RF gun linac and a magnetic bunch compressor at ISIR, Osaka University. The bunch lengths were evaluated by detecting coherent transition radiation (CTR) emitted from the electron bunches using a Michelson interferometer. (author)

  20. Generation and measurement of sub-picosecond electron bunch in photocathode rf gun

    International Nuclear Information System (INIS)

    We consider a scheme to generate a sub-picosecond electron bunch in the photocathode rf gun by improving the acceleration gradient in the gun, suitably tuning the bunch charge, the laser spot size and the acceleration phase, and reducing the growth of transverse emittance by laser shaping. A nondestructive technique is also reported to measure the electron bunch length, by measuring the high-frequency spectrum of wakefield radiation which is caused by the passage of a relativistic electron bunch through a channel surrounded by a dielectric. (authors)

  1. 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

  2. Slice emittance measurement for photocathode RF gun with solenoid scanning and RF deflecting cavity

    Science.gov (United States)

    Li, Chen; Huang, WenHui; Du, YingChao; Yan, LiXin; Tang, ChuanXiang

    2011-12-01

    The radiation of high-gain short-wavelength free-electron laser depends on the slice transverse emittance of the electron bunch. This essay introduces the method of slice emittance measurement, and shows the brief setup of this experiment using the solenoid scanning and RF deflecting cavity at Tsinghua University. The preliminary experimental results show that the slice rms emittance of the electron bunch generated by photocathode RF gun has considerable variations along the bunch and is typically less than 0.55 mm mrad for the laser rms radius of 0.4 mm.

  3. Cesium Ion Exchange Using Tank 241-AN-104 Supernate

    International Nuclear Information System (INIS)

    The River Protection Project is to design and build a high level nuclear waste treatment facility. The waste treatment plant is to process millions of gallons of radioactive waste stored in tanks at the Hanford Site. The high level nuclear waste treatment process includes various unit operations, such as ultrafiltration, precipitation, evaporation, ion exchange, and vitrification. Ion exchange is identified as the optimal treatment method for removal of cesium-137 and Tc-99 from the waste. Extensive ion exchange testing was performed using small-scale columns with actual waste samples. The objectives of this study were to: demonstrate SuperLig 644 ion exchange performance and process steps for the removal of cesium from actual AN-104 tank waste; pretreat actual AN-104 tank waste to reduce the concentration of cesium-137 in the waste below LAW vitrification limit; produce and characterize cesium eluate solutions for use in eluate evaporation tests. The experiments consisted of batch contact and small-scale column tests. The batch contact tests measured sorption partition coefficients Kds. The Kds were used to predict the effective resin capacity. The small-scale column tests, which closely mimic plant conditions, generated loading and elution profile data used to determine whether removal targets and design requirements were met

  4. A method for reducing the cesium-137 content in meat

    International Nuclear Information System (INIS)

    Reports a study of a method for reducing the amount of cesium-137 in meat from wild animals. The method is intended for use in the kitchen and is based on a combined leaching and mechanical process. (K.A.E.)

  5. Cesium-137 Levels Detected in Otters from Austria

    Directory of Open Access Journals (Sweden)

    Gutleb A.C.

    1991-02-01

    Full Text Available Pollution seems to be one of the most important causes for the decline of the European otter (Lutra lutra. The accident in the Chernobyl nuclear power plant added another aspect to environmental pollution. Few data on cesium-137 contents in otters are available, so levels were measured in 3 otters from Austria. All levels found were very low.

  6. Fission-product tellurium and cesium telluride chemistry revisited

    International Nuclear Information System (INIS)

    The chemistry of fission-product tellurium is discussed with a focus on conditions in an operating CANDU reactor and in an accident scenario, i.e., a loss of coolant accident (LOCA). Cesium telluride, Cs2Te, is likely to be one of the most abundant tellurium species released to containment. Available thermodynamic data on gas phase Cs2Te is not complete; hence the volatility of cesium telluride was studied by Knudsen-cell mass spectrometry. Cesium telluride was found to vapourize incongruently, becoming more tellurium-rich in the condensed phase as vapourization progressed. Vapour-phase species that were observed were elemental cesium and tellurium, CsTe, Cs2Te, Cs2Te2 and Cs2Te3. Second-law enthalpies and entropies were obtained for many of these species, and a third-law value, ΔH298o, of 186 ± 2 kJ·mol-1 was obtained for Cs2Te. (author)

  7. Discovery of Cesium, Lanthanum, Praseodymium and Promethium Isotopes

    OpenAIRE

    May, E.; Thoennessen, M

    2011-01-01

    Currently, forty-one cesium, thirty-five lanthanum, thirty-two praseodymium, and thirty-one promethium, isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  8. Strontium-90 and cesium-137 in fresh water

    International Nuclear Information System (INIS)

    Japan Chemical Analysis Center has analysed the strontium-90 and Cesium-137 contents in fresh water from 7 prefectures in Japan by the commission of Science and Technology Agency of Japanese Government. The method described in ''Radioactivity Survey Data in Japan No. 43 (NIRS-RSD-43, 1977) was applied to the analysis of these two radionuclides in samples. (author)

  9. Cesium ion desorption ionization with Fourier transform mass spectrometry

    International Nuclear Information System (INIS)

    Cesium ions (Cs+) are used for the production of the feed ions necessary to obtain Fourier transform mass spectra (FTMS). The molecule chosen for the initial study of this Cs+ desorption ionization (DI-FTMS) was vitamin B-12 because of its nonvolatile, thermally labile character. 21 references

  10. Membrane-based separation technologies for cesium, strontium, and technetium

    Energy Technology Data Exchange (ETDEWEB)

    Kafka, T.

    1996-10-01

    This work is one of two parallel projects that are part of an ESP task to develop high-capacity, selective, solid extractants for cesium, strontium, and technetium from nuclear wastes. In this subtask, Pacific Northwest National Laboratory (PNNL) is collaborating with 3M, St. Paul, Minnesota, working in cooperation with IBC Advanced Technologies, American Fork, Utah.

  11. Hot demonstration of proposed commercial cesium removal technology

    International Nuclear Information System (INIS)

    This report describes the work done in support of the development of technology for the continuous removal and concentration of radioactive cesium in supernatant from Melton Valley Storage Tanks (MVSTs) at the ORNL site. The primary objective was to test candidate absorbers and ion exchangers under continuous-flow conditions using actual supernatant from the MVSTs. An experimental system contained in a hot-cell facility was constructed to test the materials in columns or modules using the same batch of supernatant to allow comparison on an equal basis. Resorcinol/formaldehyde (RF) resin was evaluated at three flow rates with 50% breakthrough ranges of 35 to 50 column volumes (CV) and also through a series of five loading/elution/regeneration cycles. The results reported here include the cesium loading breakthrough curves, elution curves (when applicable), and operational problems and observations for each material. The comparative evaluations should provide critical data for the selection of the sorbent for the ORNL Cesium Removal Demonstration project. These results will be used to help determine the design parameters for demonstration-scale systems. Such parameters include rates of cesium removal, quantity of resin or sorbent to be used, and elution and regeneration requirements, if applicable

  12. Cesium-137 Levels Detected in Otters from Austria

    OpenAIRE

    Gutleb A.C.; Mraz, G.

    1991-01-01

    Pollution seems to be one of the most important causes for the decline of the European otter (Lutra lutra). The accident in the Chernobyl nuclear power plant added another aspect to environmental pollution. Few data on cesium-137 contents in otters are available, so levels were measured in 3 otters from Austria. All levels found were very low.

  13. Electrochemistry of silver iodide the capacity of the double layer at the silver iodide-water interface

    NARCIS (Netherlands)

    Lyklema, J.; Overbeek, J.Th.G.

    1961-01-01

    A method is described for obtaining differential double layer capacities on silver iodide. Especially the influence of the nature and concentration of indifferent electrolytes was investigated, viz., the nitrates of Li·, K·, Rb·, NH4·, H·, Tl·, Mg··, Ba··, Co··, Cd··, Pb··, La···, Th····, the fluori

  14. A Monolithically Integrated Gallium Nitride Nanowire/Silicon Solar Cell Photocathode for Selective Carbon Dioxide Reduction to Methane.

    Science.gov (United States)

    Wang, Yichen; Fan, Shizhao; AlOtaibi, Bandar; Wang, Yongjie; Li, Lu; Mi, Zetian

    2016-06-20

    A gallium nitride nanowire/silicon solar cell photocathode for the photoreduction of carbon dioxide (CO2 ) is demonstrated. Such a monolithically integrated nanowire/solar cell photocathode offers several unique advantages, including the absorption of a large part of the solar spectrum and highly efficient carrier extraction. With the incorporation of copper as the co-catalyst, the devices exhibit a Faradaic efficiency of about 19 % for the 8e(-) photoreduction to CH4 at -1.4 V vs Ag/AgCl, a value that is more than thirty times higher than that for the 2e(-) reduced CO (ca. 0.6 %). PMID:27128407

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

    International Nuclear Information System (INIS)

    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.

  16. Selective extraction of cesium: from compound to process

    International Nuclear Information System (INIS)

    Under the French law of 30 December 1991 on nuclear waste management, research is conducted to recover long-lived fission products from high-level radioactive effluents generated by spent fuel reprocessing, in order to destroy them by transmutation or encapsulate them in specific matrices. Cesium extraction with mono and bis-crown calix(4)arenes (Frame 1) is a candidate for process development. These extractants remove cesium from highly acidic or basic pH media even with high salinity. A real raffinate was treated in 1994 in a hot cell to extract cesium with a calix-crown extractant. The success of this one batch experiment confirmed the feasibility of cesium decontamination from high-level liquid waste. It was then decided to develop a process flowchart to extract cesium selectively from high-level raffinate, to be included in the general scheme of long-lived radionuclide partitioning. It was accordingly decided to develop a process based on liquid-liquid extraction and hence optimize a calixarene/diluent solvent according to: - hydraulic properties: density, viscosity, interfacial tension, - chemical criteria: sufficient cesium extraction (depending on the diluent), kinetics, third phase elimination... New mono-crown-calixarenes branched with long aliphatic groups (Frame 2) were designed to be soluble in aliphatic diluents. To prevent third phase formation associated with nitric acid extraction, the addition of modifiers (alcohol, phosphate and amide) in the organic phase was tested (Frame 3). Table 1 shows examples of calixarene/diluent systems suitable for a process flowchart, and Figure 2 provides data on cesium extraction with these new systems. Alongside these improvements, a system based on a modified 1,3-di(n-octyl-oxy)2,4-calix[4]arene crown and a modified diluent was also developed, considering a mixed TPH/NPHE system as the diluent, where TPH (hydrogenated tetra propylene) is a common aliphatic industrial solvent and NPHE is nitrophenyl

  17. Demonstration test for decontamination technology of cesium-contaminated ash

    International Nuclear Information System (INIS)

    KEPCO Engineering and Construction Company (KEPCO E and C), architecture and engineering company of nuclear power plant, developed the 'decontamination technology of cesium-contaminated ash' in the basis of pre-owned 'decontamination technology of cesium-contaminated soil'. The new technology was demonstrated in Fukushima prefecture during 12 days from November 5, 2013, in order to verify the performance. Demonstration equipment (CEDECON-DA), with a capacity of treatment of 20 ℓ per batch, can be carried in a container in order to promote the ease of transportation and in-situ installation. Through the demonstration test it was verified the superior performance and the possibility of commercialization. This technique comprises of cesium separation and cesium coagulation processes. Briefly speaking, the principal of this process is as follows; cesium is separated from ash, detached to the coagulation and then deposited. The decontaminated ash can be disposed of into municipal landfills as conventional non-radioactive waste. The present technology is evaluated such that the disposal amount of radioactive waste will be significantly reduced. The ash with average concentration of 6,200 Bq/kg from a conventional incineration plant was used for the demonstration test. Each separate performance test has been carried out under acid, neutral and alkaline conditions, respectively. The test result for alkaline condition showed the highest decontamination ratio of 82-85% and the volume reduction ratio of 95%. Radioactive Waste Management and Nuclear Facility Decommissioning Technology Center (RANDEC) performed the radiation protection management, activity measurement and evaluation in the demonstration test results. (author)

  18. Some aspects of cesium deposition in Transilvania (Romania)

    International Nuclear Information System (INIS)

    Following the accident of the Chernobyl atomic electric power station, a great quantity of radionuclides (∼100MCi) escaped from the reactor. It was estimated that 13% of the inventory activity of cesium representing 1.5-2 MCi left the reactor. The radioactive deposits were very nonuniform for the same distance and in the same direction from Chernobyl nuclear center having a close dependence upon direction and speed of wind and pluviometric conditions. The rains, especially the storms, spectacularly increased the radioactive fallout. Although, for the first two-three days, subsequent to accident, the meteorological conditions were favorable for Romania, after April 29/30, because of the changing in the wind direction on SW (initial it was N and NW) the countries were on this direction - Romania, Bulgaria, Greece, former Yugoslavia - began to be intensely contaminated with radioactive fallout. In Romania, the radioactive cloud passing coincided with abundant rains, especially on the direction mentioned above. On this direction, the cesium deposits are of 8-2 times larger than other Romanian regions. The torrential rain which fell on May 1st 1986, in the western side of Cluj Napoca town caused an intense contamination especially with short-life isotopes as Te, I, Ba, La, Mo. Medium and long-life isotopes as Ru, Zr, Cs, Sr were present in large quantities in this area.too. For the total contribution the value obtained was 1130 kBq/m2, much larger than the average in Romania. This work presents data about cesium content of pollen samples gathered daily between 1-30 May 1986; cesium deposits in five areas and some measurements in connection with cesium mitigation in soils

  19. Abiotic formation of methyl iodide on synthetic birnessite: A mechanistic study

    Energy Technology Data Exchange (ETDEWEB)

    Allard, Sébastien, E-mail: s.allard@curtin.edu.au; Gallard, Hervé

    2013-10-01

    Methyl iodide is a well-known volatile halogenated organic compound that contributes to the iodine content in the troposphere, potentially resulting in damage to the ozone layer. Most methyl iodide sources derive from biological activity in oceans and soils with very few abiotic mechanisms proposed in the literature. In this study we report that synthetic manganese oxide (birnessite δ-MnO{sub 2}) can catalyze the formation of methyl iodide in the presence of natural organic matter (NOM) and iodide. Methyl iodide formation was only observed at acidic pH (4–5) where iodide is oxidized to iodine and NOM is adsorbed on δ-MnO{sub 2}. The effect of δ-MnO{sub 2}, iodide and NOM concentrations, nature of NOM and ionic strength was investigated. High concentrations of methyl iodide were formed in experiments conducted with the model compound pyruvate. The Lewis acid property of δ-MnO{sub 2} leads to a polarization of the iodine molecule, and catalyzes the reaction with natural organic matter. As manganese oxides are strong oxidants and are ubiquitous in the environment, this mechanism could significantly contribute to the global atmospheric input of iodine. Highlights: • Methyl iodide is formed when iodide, natural organic matter and MnO{sub 2} are in contact. • Iodide is oxidized to iodine by MnO{sub 2} which reacts with NOM already adsorbed on MnO{sub 2}. • High formation of methyl iodide was observed with pyruvate. • This abiotic mechanism could contribute to the input of iodine in the atmosphere. • This abiotic mechanism could impact the ozone layer in the troposphere.

  20. Abiotic formation of methyl iodide on synthetic birnessite: A mechanistic study

    International Nuclear Information System (INIS)

    Methyl iodide is a well-known volatile halogenated organic compound that contributes to the iodine content in the troposphere, potentially resulting in damage to the ozone layer. Most methyl iodide sources derive from biological activity in oceans and soils with very few abiotic mechanisms proposed in the literature. In this study we report that synthetic manganese oxide (birnessite δ-MnO2) can catalyze the formation of methyl iodide in the presence of natural organic matter (NOM) and iodide. Methyl iodide formation was only observed at acidic pH (4–5) where iodide is oxidized to iodine and NOM is adsorbed on δ-MnO2. The effect of δ-MnO2, iodide and NOM concentrations, nature of NOM and ionic strength was investigated. High concentrations of methyl iodide were formed in experiments conducted with the model compound pyruvate. The Lewis acid property of δ-MnO2 leads to a polarization of the iodine molecule, and catalyzes the reaction with natural organic matter. As manganese oxides are strong oxidants and are ubiquitous in the environment, this mechanism could significantly contribute to the global atmospheric input of iodine. Highlights: • Methyl iodide is formed when iodide, natural organic matter and MnO2 are in contact. • Iodide is oxidized to iodine by MnO2 which reacts with NOM already adsorbed on MnO2. • High formation of methyl iodide was observed with pyruvate. • This abiotic mechanism could contribute to the input of iodine in the atmosphere. • This abiotic mechanism could impact the ozone layer in the troposphere