WorldWideScience

Sample records for dynodes

  1. At site qualification of accelerating tube dynodes

    International Nuclear Information System (INIS)

    Rajan, Rehim N.; Dewangan, S.; Sharma, D.K.

    2015-01-01

    A dc electron beam accelerator rated for 3 MeV encountered numerous vacuum side discharges at terminal voltage levels of 1800 kV. The cumulative rating of the accelerating tube in the system is 3350 kV. Pulsed currents in the order of 50 mA has been observed at the beam collector during these events along with voltage dips in terminal voltage. As dynode to dynode arcing is suspected to be the primary cause of this behaviour, it is desired to test the voltage withstanding capacity of each pair of dynodes. The accelerating tubes are rated for 335 kV at 6 kg/cm 2 SF 6 environment. However working at these pressures and testing of individual pairs of dynodes are impractical for qualification of dynodes of the 10 sets of accelerating tubes mounted in the accelerator. This problem has been overcome by using atmospheric pressure SF 6 and solid dielectrics. Experience of at site testing of the accelerating tube dynodes are described in this paper. (author)

  2. Secondary Electron Emission Materials for Transmission Dynodes in Novel Photomultipliers: A Review

    Directory of Open Access Journals (Sweden)

    Shu Xia Tao

    2016-12-01

    Full Text Available Secondary electron emission materials are reviewed with the aim of providing guidelines for the future development of novel transmission dynodes. Materials with reflection secondary electron yield higher than three and transmission secondary electron yield higher than one are tabulated for easy reference. Generations of transmission dynodes are listed in the order of the invention time with a special focus on the most recent atomic-layer-deposition synthesized transmission dynodes. Based on the knowledge gained from the survey of secondary election emission materials with high secondary electron yield, an outlook of possible improvements upon the state-of-the-art transmission dynodes is provided.

  3. Performance of 8- and 12-dynode stage multianode photo-multipliers

    Energy Technology Data Exchange (ETDEWEB)

    Bibby, J.H. [University of Oxford, Oxford (United Kingdom); Buckley, A. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Chamonal, R.J.U. [University of Edinburgh, Edinburgh (United Kingdom)]. E-mail: chamonal@ph.ed.ac.uk; Easo, S. [CCLRC, Rutherford Aplleton Laboratory, Chilton, Didcot, Oxfordshire (United Kingdom); Eisenhardt, S. [University of Edinburgh, Edinburgh (United Kingdom); Gibson, V. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Harnew, N. [University of Oxford, Oxford (United Kingdom); Muheim, F. [University of Edinburgh, Edinburgh (United Kingdom); Howard, A. [Imperial College, London (United Kingdom); Lawrence, J. [University of Edinburgh, Edinburgh (United Kingdom); Pickford, A. [University of Glasgow, Glasgow (United Kingdom); Plackett, R. [Imperial College, London (United Kingdom); Price, D.R. [Imperial College, London (United Kingdom); Rademacker, J. [University of Oxford, Oxford (United Kingdom); Smale, N. [University of Oxford, Oxford (United Kingdom); Soler, F.J.P. [University of Glasgow, Glasgow (United Kingdom); CCLRC, Rutherford Aplleton Laboratory, Chilton, Didcot, Oxfordshire (United Kingdom); Somerville, L. [University of Oxford, Oxford (United Kingdom); Storey, J. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Websdale, D. [Imperial College, London (United Kingdom); Wotton, S. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom)

    2006-11-01

    We report on studies of 64-channel Multianode Photo-Multiplier Tubes (MaPMTs) as photo-detectors for Ring Imaging CHerenkov (RICH) counters. The newly available 8-dynode stage MaPMT was tested in particle beams at CERN. The MaPMT signals were read out directly with the Beetle1.2 chip which was designed for the LHCb environment and operates at 40MHz. The photon yield and signal losses were determined for a cluster of 3x3 close-packed MaPMTs. The performance of the 8-dynode stage MaPMT was compared to that of the 12-dynode stage MaPMT which has a larger intrinsic gain.

  4. Best-estimate analyses of LOFT anticipated transients with and without scram using DYNODE-P

    International Nuclear Information System (INIS)

    Kern, R.C.; Anderson, R.O.; Rautmann, D.A.

    1984-01-01

    Six LOFT transient tests with scram (L6-1, L6-2, L6-3, L6-7, L6-8B-1, and L6-8B-2) and two anticipated transient tests without scram (L9-3 and L9-4) have been analyzed using a best-estimate DYNODE-P/5.2 computer model. These tests span a wide range of anticipated operational occurrences for Pressurized Water Reactors. In general, satisfactory agreement between calculation and measurement for the key system parameters (nuclear power, primary and secondary pressures, temperatures, liquid levels, and flows) have been found. Sensitivity studies have resolved all significant discrepancies. These analyses have provided a significant qualification of the model for application to these types of events

  5. The effect of the first dynode`s geometry on the detection efficiency of a 119EM electron multiplier used as a highly charged ion detector

    Czech Academy of Sciences Publication Activity Database

    Krása, Josef; Pfeifer, Miroslav; Stöckli, M. P.; Lehnert, U.; Fry, D.

    1999-01-01

    Roč. 152, - (1999), s. 397-402 ISSN 0168-583X R&D Projects: GA AV ČR IAA1010819; GA ČR GA202/97/0918 Institutional research plan: CEZ:AV0Z1010921 Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.118, year: 1999

  6. Ceramic Electron Multiplier

    International Nuclear Information System (INIS)

    Comby, G.

    1996-01-01

    The Ceramic Electron Multipliers (CEM) is a compact, robust, linear and fast multi-channel electron multiplier. The Multi Layer Ceramic Technique (MLCT) allows to build metallic dynodes inside a compact ceramic block. The activation of the metallic dynodes enhances their secondary electron emission (SEE). The CEM can be used in multi-channel photomultipliers, multi-channel light intensifiers, ion detection, spectroscopy, analysis of time of flight events, particle detection or Cherenkov imaging detectors. (auth)

  7. Scintillation detectors in experiments on plasma accelerators

    International Nuclear Information System (INIS)

    Bystritskij, V.M.; Gerasimov, V.V.; Kublikov, R.V.; Parzhitskij, S.S.; Smirnov, V.S.; Wozniak, J.; Dudkin, G.N.; Nechaev, B.A.; Padalko, V.M.

    2005-01-01

    The gating circuits for photomultipliers of scintillation detectors operating in powerful pulsed electromagnetic and nuclear radiation fields are investigated. PMTs with the jalousie-type dynode system and with the linear dynode system are considered. The basic gating circuits of the photomultipliers involving active and resistor high-voltage dividers are given. The results of the investigations are important for experiments in which it is necessary to discriminate in time the preceding background radiation and the process of interest. (author)

  8. Two types of photomultiplier voltage dividers for high and changing count rates

    International Nuclear Information System (INIS)

    Reiter, W.L.; Stengl, G.

    1980-01-01

    We report on the design of two types of voltage distribution circuits for high stability photomultiplier operation. 'Type A' voltage divider is an ohmic voltage divider with high bleeder current (up to 10 mA) and the resistor chain split at one of the last dynodes, usually the dynode where the analog signal is derived from. This simple constructive measure improves the stability of the dynode voltage by a factor of 5 compared with an unsplit conventional resistor chain. 'Type B' is a novel active voltage divider using cold cathode tubes ar regulating elements. This voltage divider exhibits excellent temperature stability (about 10 -4 / 0 C). With 'type B' an equal stability compared with conventional ohmic dividers can be achieved at a bleeder current smaller by one order of magnitude. Of course both concepts, 'type A' and 'type B', can be combined. (orig.)

  9. Monte Carlo simulation of the spectral response of beta-particle emitters in LSC systems

    International Nuclear Information System (INIS)

    Ortiz, F.; Los Arcos, J.M.; Grau, A.; Rodriguez, L.

    1992-01-01

    This paper presents a new method to evaluate the counting efficiency and the effective spectra at the output of any dynodic stage, for any pure beta-particle emitter, measured in a liquid scintillation counting system with two photomultipliers working in sum-coincidence mode. The process is carried out by a Monte Carlo simulation procedure that gives the electron distribution, and consequently the counting efficiency, at any dynode, in response to the beta particles emitted, as a function of the figure of merit of the system and the dynodic gains. The spectral outputs for 3 H and 14 C have been computed and compared with experimental data obtained with two sets of quenched radioactive standards of these nuclides. (orig.)

  10. Scintillation 1024-channel hodoscope

    International Nuclear Information System (INIS)

    Kotov, I.V.; Krasnokutskij, R.N.; Kurbakov, V.I.; Shchukin, A.V.

    1993-01-01

    Flow diagram of voltage divider for photomultiplier used in scintillation multichannel hodoscope is described. The suggested diagram of the divider allows to optimize potential distribution at the innput chamber (photocathode - modulator - first dynode) and in the tail segment of the divider (the nineth dynode-anode). Adjustment of high voltage is conducted using multirotational potentiometer switched in series with the divider. Amplifier-limiter with 80 mkA threshold set at voltage comparator is placed at divide plate. Threshold of its sensitivity constitutes 80 mkA. Hodoscope supply system consists of supply sources of comparators (+-6V) four sources of auxiliary supply sources of the last dynodes of photomultipliers and high-voltage source. Current consumption constitutes 25 A by - 6V, 23 A by + 6 V for the whole hodoscope and up to 200 mA from high-voltage source for one plane. Additional charging sources have constant consumption equal to ∼ 20 mA

  11. Performances of multi-channel ceramic photomultipliers

    International Nuclear Information System (INIS)

    Comby, G.; Karolak, M.; Piret, Y.; Mouly, J.P.

    1995-09-01

    Ceramic electron multipliers with real metal dynodes and independent channels ware constructed using multilayer ceramic technology. Tests of these prototypes show their capability to form sensitive detectors such as photomultipliers or light intensifiers. Here, we present results for the photocathode sensitivity, dynode activation, gain, linearity range and dynamic characteristics as well as the effect of 3-year aging of the main operational functions. The advantages provided by the ceramic components are discussed. These results motivate the development of a compact 256 pixel ceramic photomultiplier. (author)

  12. Statistics of electron multiplication in multiplier phototube: iterative method

    International Nuclear Information System (INIS)

    Grau Malonda, A.; Ortiz Sanchez, J.F.

    1985-01-01

    An iterative method is applied to study the variation of dynode response in the multiplier phototube. Three different situations are considered that correspond to the following ways of electronic incidence on the first dynode: incidence of exactly one electron, incidence of exactly r electrons and incidence of an average anti-r electrons. The responses are given for a number of steps between 1 and 5, and for values of the multiplication factor of 2.1, 2.5, 3 and 5. We study also the variance, the skewness and the excess of jurtosis for different multiplication factors. (author)

  13. A simple method to improve the spatial uniformity of venetian-blind photomultiplier tubes

    International Nuclear Information System (INIS)

    Santos, J.M.F. dos; Veloso, J.F.C.A.; Morgado, R.E.

    1996-01-01

    An improvement in the uniformity of venetian-blind photomultiplier tubes has been achieved by reducing the voltage difference between the first and second dynodes. The method has been applied to a gas proportional scintillation counter (GPSC) instrumented with a venetian-blind photomultiplier (PMT). When exposed to a 20-mm collimated 5.9-keV x-ray beam, an overall improvement in energy resolution for the GPSC/PMT combination from 20% to 11.5% was achieved. An alternative method that reduces the photocathode-to-first-dynode voltage was less effective and resulted in a severe degradation of detector energy resolution

  14. Effect of interelectrode potentials in the photomultiplier on formation of afterpulses

    International Nuclear Information System (INIS)

    Morozov, V.A.; Morozova, N.V.

    2001-01-01

    The effect of the interelectrode potential difference in the XP2020 photomultiplier on the intensity of formation of afterpulses caused by ion feedback is studied. It is shown that the photocathode - first dynode gap plays a decisive role in this process while the dynode system is of minor importance at pulse currents below a few tens of milliampers. It is also shown that the anomalous ratio between the afterpulse amplitudes and basic pulse amplitudes can be governed by the process of single ion detection. (author)

  15. Statistics of electron multiplication in a multiplier phototube; Iterative method

    International Nuclear Information System (INIS)

    Ortiz, J. F.; Grau, A.

    1985-01-01

    In the present paper an iterative method is applied to study the variation of dynode response in the multiplier phototube. Three different situation are considered that correspond to the following ways of electronic incidence on the first dynode: incidence of exactly one electron, incidence of exactly r electrons and incidence of an average r electrons. The responses are given for a number of steps between 1 and 5, and for values of the multiplication factor of 2.1, 2.5, 3 and 5. We study also the variance, the skewness and the excess of jurtosis for different multiplication factors. (Author) 11 refs

  16. Statistics of electron multiplication in a multiplier phototube; Iterative method; Estadistica de la multiplicacion de electrones en un fotomultiplicador: Metodos iterativos

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz, J F; Grau, A

    1985-07-01

    In the present paper an iterative method is applied to study the variation of dynode response in the multiplier phototube. Three different situation are considered that correspond to the following ways of electronic incidence on the first dynode: incidence of exactly one electron, incidence of exactly r electrons and incidence of an average r electrons. The responses are given for a number of steps between 1 and 5, and for values of the multiplication factor of 2.1, 2.5, 3 and 5. We study also the variance, the skewness and the excess of jurtosis for different multiplication factors. (Author) 11 refs.

  17. Gain stabilization circuit of measuring devices with photomultipliers

    International Nuclear Information System (INIS)

    Seda, J.; Sabol, J.

    1974-01-01

    A circuit is designed for the stabilization of the gain of measuring devices with photomultipliers, suitable especially for the stabilization of scintillation detection systems, in which the correction signal is applied to the photomultiplier grid placed between the photocathode and the first dynode. (J.K.)

  18. Single-electron multiplication statistics as a combination of Poissonian pulse height distributions using constraint regression methods

    International Nuclear Information System (INIS)

    Ballini, J.-P.; Cazes, P.; Turpin, P.-Y.

    1976-01-01

    Analysing the histogram of anode pulse amplitudes allows a discussion of the hypothesis that has been proposed to account for the statistical processes of secondary multiplication in a photomultiplier. In an earlier work, good agreement was obtained between experimental and reconstructed spectra, assuming a first dynode distribution including two Poisson distributions of distinct mean values. This first approximation led to a search for a method which could give the weights of several Poisson distributions of distinct mean values. Three methods have been briefly exposed: classical linear regression, constraint regression (d'Esopo's method), and regression on variables subject to error. The use of these methods gives an approach of the frequency function which represents the dispersion of the punctual mean gain around the whole first dynode mean gain value. Comparison between this function and the one employed in Polya distribution allows the statement that the latter is inadequate to describe the statistical process of secondary multiplication. Numerous spectra obtained with two kinds of photomultiplier working under different physical conditions have been analysed. Then two points are discussed: - Does the frequency function represent the dynode structure and the interdynode collection process. - Is the model (the multiplication process of all dynodes but the first one, is Poissonian) valid whatever the photomultiplier and the utilization conditions. (Auth.)

  19. Reduction of predose reading in radiophotoluminescent glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ramanathan, G.; Nagpal, J.S.; Gangadharan, P. (Bhabha Atomic Research Centre, Bombay (India). Div. of Radiological Protection)

    1982-04-01

    A method is described of reducing the predose reading in radiophotoluminescent glass dosimeters. Decay time discrimination is obtained by making use of the space charge effects which occur between the last dynode and the collector of the detecting photomultiplier and discriminating the pulse heights obtained.

  20. The reduction of predose reading in radiophotoluminescent glasses

    International Nuclear Information System (INIS)

    Ramanathan, G.; Nagpal, J.S.; Gangadharan, P.

    1982-01-01

    A method is described of reducing the predose reading in radiophotoluminescent glass dosimeters. Decay time discrimination is obtained by making use of the space charge effects which occur between the last dynode and the collector of the detecting photomultiplier and discriminating the pulse heights obtained. (U.K.)

  1. Potential applications of electron emission membranes in medicine

    Energy Technology Data Exchange (ETDEWEB)

    Bilevych, Yevgen [Fraunhofer Institute for Reliability and Microintegration (IZM), Berlin (Germany); University of Bonn, Bonn (Germany); Brunner, Stefan E. [Delft University of Technology, Delft (Netherlands); Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences, Vienna (Austria); Chan, Hong Wah; Charbon, Edoardo [Delft University of Technology, Delft (Netherlands); Graaf, Harry van der, E-mail: vdgraaf@nikhef.nl [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); Hagen, Cornelis W. [Delft University of Technology, Delft (Netherlands); Nützel, Gert; Pinto, Serge D. [Photonis, Roden (Netherlands); Prodanović, Violeta [Delft University of Technology, Delft (Netherlands); Rotman, Daan [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); University of Amsterdam, Amsterdam (Netherlands); Santagata, Fabio [State Key Lab for Solid State Lighti Changzhou base, F7 R& D HUB 1, Science and Education Town, Changzhou 213161, Jangsu Province (China); Sarro, Lina; Schaart, Dennis R. [Delft University of Technology, Delft (Netherlands); Sinsheimer, John; Smedley, John [Brookhaven National Laboratory, Upton, NY (United States); Tao, Shuxia; Theulings, Anne M.M.G. [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands)

    2016-02-11

    With a miniaturised stack of transmission dynodes, a noise free amplifier is being developed for the detection of single free electrons, with excellent time- and 2D spatial resolution and efficiency. With this generic technology, a new family of detectors for individual elementary particles may become possible. Potential applications of such electron emission membranes in medicine are discussed.

  2. Ion feedback afterpulses in FEU-130 and XP2020 photomultipliers

    International Nuclear Information System (INIS)

    Brudanin, V.B.; Morozov, V.A.; Morozova, N.V.

    2003-01-01

    Intensities and time distributions of ion feedback afterpulses are studied as a function of the difference of potentials between the photocathode and the first dynodes in FEU-130. The intensities and amplitudes of afterpulses in FEU-130 are found to be appreciably larger than in XP2020, which may limit the use of FEU-130 in some experiments with autocorrelation delayed-coincidence spectrometers

  3. The R&D of the 20 in. MCP–PMTs for JUNO

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yaping [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); State Key Laboratory of Particle Detection and Electronics, Beijing 100049 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Huang, Guorui [North Night Vision Tech. Ltd., Nanjing 211106 (China); Heng, Yuekun [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); State Key Laboratory of Particle Detection and Electronics, Beijing 100049 (China); Li, Dong [North Night Vision Tech. Ltd., Nanjing 211106 (China); Liu, Huilin [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 710068 (China); Liu, Shulin [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); State Key Laboratory of Particle Detection and Electronics, Beijing 100049 (China); Li, Weihua [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 710068 (China); Ning, Zhe [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); State Key Laboratory of Particle Detection and Electronics, Beijing 100049 (China); Qi, Ming [Department of Physics, Nanjing University, Nanjing 210093 (China); Qian, Sen, E-mail: qians@ihep.ac.cn [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); State Key Laboratory of Particle Detection and Electronics, Beijing 100049 (China); Sun, Jianning; Si, Shuguang [North Night Vision Tech. Ltd., Nanjing 211106 (China); Tian, Jinshou [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 710068 (China); Wang, Xingchao [North Night Vision Tech. Ltd., Nanjing 211106 (China); and others

    2016-07-11

    A new concept of large area photomultiplier based on MCPs was conceived for JUNO by the scientists in IHEP, and with the collaborative work of the MCP–PMT collaboration in China, 8 in. and 20 in. prototypes were produced. Test results show that this type of MCP–PMT can have good SPE performance as the traditional dynode type PMTs.

  4. Some results concerning the external photoelectric effect and secondary emission; Quelques resultats sur l'effet photoelectrique externe et l'emission secondaire

    Energy Technology Data Exchange (ETDEWEB)

    Lenouvel, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Ecole normale superieure, 75 - Paris (France)

    1967-01-01

    The characteristics and limiting possibilities of the various constituent parts of a photoelectric detector are considered. Two methods for illuminating the cathode are described and discussed. The few scattered results concerning the maximum output of cathodes and dynodes are collected together and a tentative explanation is put forward. A comparison is made of three methods for measuring very low light fluxes. (author) [French] Nous degageons les caracteristiques et les possibilites limites des divers elements constitutifs d'un detecteur photoelectrique. Deux solutions d'illumination de la cathode sont decrites et discutees. Les quelques resultats epars sur la limite de debit des cathodes et des dynodes sont rassembles et une interpretation provisoire est esquissee. Trois moyens de mesure des tres faibles flux lumineux sont compares. (auteur)

  5. Fast light pulse measurements and temporal fluctuations in photomultipliers

    International Nuclear Information System (INIS)

    Miehe, J.A.; Sipp, B.

    1975-01-01

    This paper reviews the results on time fluctuations in high gain first dynode photomultipliers used in single photon timing experiments; the theoretical analysis of the measurement of the shape of light pulses is recalled and the previously obtained results concerning time dispersion in the photocathode, first dynode space are discussed. In addition, the influence of the variations of the electron transit time in the multiplier on the time resolution curves of the detector is examined: the curves obtained by leading-edge triggering of the anodic pulse show a strong dependence on the threshold level of the discriminator. A single-photoelectron timing resolution of 270ps is measured using a low leading edge discrimination [fr

  6. Secondary emission from a CuBe target due to bombardment with parent and fragment ions of ammonia and phosphine

    International Nuclear Information System (INIS)

    Maerk, T.D.

    1977-01-01

    The secondary electron emission of the first dynode of a CuBe alloy sixteen dynode electron multiplier has been studied in the course of electron impact ionization studies of ammonia and phosphine. Relative secondary electron emission coefficients have been obtained for the singly and doubly charged parent and fragment ions of ammonia, ammonia-d 3 , phosphine and phosphine-d 3 for kinetic energies of 5,25 and 10,5 keV. It has been found, that in general deuterated ions have smaller γ coefficients, that ammonia ions have larger γ coefficients than corresponding phosphine ions, and that the γ coefficients increase with the complexity of the ion under study. (Auth.)

  7. Linearity testing and dead-time determination for MC-ICP-MS ion counters using the IRMM-072 series of uranium isotope reference materials

    OpenAIRE

    RICHTER Stephan; KONEGGER-KAPPEL S.; BOULYGA S.; STADELMANN G.; KOEPF A.; SIEGMUND H.

    2016-01-01

    The Environmental Sample Laboratory (ESL) of the International Atomic Energy Agency (IAEA) routinely analyses environmental swipe samples for their bulk U and Pu isotope amounts and ratios using a Neptune Plus™ (Thermo Fisher Scientific) multi collector-inductively coupled plasma mass spectrometer (MC-ICP-MS). The instrument is equipped with the so-called “L5 ion counter package”, which comprises ten Faraday cups, three classical discrete dynode secondary electron multipliers (SEM), and two c...

  8. Dynamic range broadening for photomultipliers in kinetic spectrophotometry

    International Nuclear Information System (INIS)

    Rumas, V.K.

    1983-01-01

    The circuit of switching on a photomultiplier with prestage modulation developed for kinetic spectrophotometry purposes is described. Distinguishing features of the scheme are wide range of control pulse duration (40 nc - 2.5 mc) and direct transistor photostart by laser light pulse. In the case of PM prestage modulation for the second dynode modulation depth attains 400 while PM opening time constitutes 40 nc

  9. On the stability of performance of NaI(Tl) scintillation spectrometer with FEhU-49 photomultiplier at high counting rates

    International Nuclear Information System (INIS)

    Belousov, A.S.; Vazdik, Ya.A.; Malinovskij, E.N.; Rusakov, S.V.; Solov'ev, Yu.V.; Fomenko, A.M.; Sharejko, P.N.

    1986-01-01

    The dependence of instability in NaI(Tl)-spectrometer characteristics on the instability of photomultiplier (PM), the multiplication factor of which grows with an increase in counting rate, is determined. A simple way to stabilize PM gain factor with an accuracy up to 1.7% is suggested, which consists in stabilization of voltage in two terminal dynodes of PM and photocathode illumination by an auxillary light source

  10. Air Force Research Laboratory Sensors Directorate Communications Branch History from 1960-2011

    Science.gov (United States)

    2011-12-01

    the National Command Authority ( NCA ) and U.S. strategic and non-strategic forces. The E-6B was conceived as a replacement for the Air Force’s Airborne...application. The physical design will meet a l-cubic-foot volume goal, given LSI processor development and large- cathode , folded-dynode photomultiplier...development. Performance limiters are the input optics ’transmission at large zenith angles and photodetector cathode quantum efficiency at the

  11. Development of a 13-in. Hybrid Avalanche Photo-Detector (HAPD) for a next generation water Cherenkov detector

    International Nuclear Information System (INIS)

    Nakayama, H.; Kusaka, A.; Kakuno, H.; Abe, T.; Iwasaki, M.; Aihara, H.; Shiozawa, M.; Tanaka, M.; Kyushima, H.; Suyama, M.; Kawai, Y.

    2006-01-01

    We have developed a 13-in. Hybrid Avalanche Photo-Detector (HAPD) for photosensors in next generation water Cherenkov type detectors. We study the performance of the HAPD and the results show good time resolution better than σ=1ns, good sensitivity for single photon detection, wide dynamic range, and good uniformity on the photocathode. The HAPD is also expected to be less expensive than large PMTs because of its simpler structure without dynodes

  12. Cross-talk of a multi-anode PMT and attainment of a σ∼10ps TOF counter

    International Nuclear Information System (INIS)

    Enari, Y.; Hayasaka, K.; Hokuue, T.; Inami, K.; Ohshima, T.; Sato, N.; Akatsu, M.; Kawakami, S.; Miyabayashi, Y.; Tokuda, H.; Yanase, H.; Shimoi, H.; Fujimori, T.

    2005-01-01

    We extensively studied a cross-talk phenomenon that seriously deteriorates the high time-resolution of a multi-anode 16-channel linear array photo-multiplier tube (PMT); the dynode structures were modified to eliminate the cross-talk effect and to recover a time resolution of σ=70-80ps for single photons. The use of 16 anode signals of the modified PMT enabled us to attain σ=12ps for a small TOF counter of Cherenkov radiation

  13. Extension of photomultiplier tube dynamic range for the LHAASO-KM2A electromagnetic particle detectors

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Hongkui, E-mail: lvhk@ihep.ac.cn [Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Sheng, Xiangdong; He, Huihai; Liu, Jia [Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Zhongquan [Shandong University, Jinan 250100 (China); Hou, Chao; Zhao, Jing [Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2015-05-01

    In the Large High Altitude Air Shower Observatory (LHAASO), the 1 km{sup 2} array (KM2A) requires linear measurement of optical intensity with a wide dynamic range. Over 5000 photomultiplier tubes (PMTs) are employed in this experiment and developed as “two outputs” device (anode and dynode) to meet the relevant requirements. In this study, the linearity of the anode and the eighth dynode (DY8), which is limited by space charge effects and mainly related to the relative dynode voltage ratios of the PMT divider, is examined. A voltage divider for the Hamamatsu R11102 PMT is designed and a dramatically enhanced linearity is demonstrated. Test results show that this design can cover a wide dynamic range from 20 to 2×10{sup 5} photoelectrons and achieve a peak anode current of 380 mA at a PMT gain of 10{sup 5}, which satisfies the requirements of KM2A electromagnetic particle detectors. The circuit design has been successfully simulated using the simulation software Multisim. The details of PMT performance tests and simulations are described.

  14. Extension of photomultiplier tube dynamic range for the LHAASO-KM2A electromagnetic particle detectors

    Science.gov (United States)

    Lv, Hongkui; Sheng, Xiangdong; He, Huihai; Liu, Jia; Zhang, Zhongquan; Hou, Chao; Zhao, Jing

    2015-05-01

    In the Large High Altitude Air Shower Observatory (LHAASO), the 1 km2 array (KM2A) requires linear measurement of optical intensity with a wide dynamic range. Over 5000 photomultiplier tubes (PMTs) are employed in this experiment and developed as "two outputs" device (anode and dynode) to meet the relevant requirements. In this study, the linearity of the anode and the eighth dynode (DY8), which is limited by space charge effects and mainly related to the relative dynode voltage ratios of the PMT divider, is examined. A voltage divider for the Hamamatsu R11102 PMT is designed and a dramatically enhanced linearity is demonstrated. Test results show that this design can cover a wide dynamic range from 20 to 2×105 photoelectrons and achieve a peak anode current of 380 mA at a PMT gain of 105, which satisfies the requirements of KM2A electromagnetic particle detectors. The circuit design has been successfully simulated using the simulation software Multisim. The details of PMT performance tests and simulations are described.

  15. Extension of photomultiplier tube dynamic range for the LHAASO-KM2A electromagnetic particle detectors

    International Nuclear Information System (INIS)

    Lv, Hongkui; Sheng, Xiangdong; He, Huihai; Liu, Jia; Zhang, Zhongquan; Hou, Chao; Zhao, Jing

    2015-01-01

    In the Large High Altitude Air Shower Observatory (LHAASO), the 1 km 2 array (KM2A) requires linear measurement of optical intensity with a wide dynamic range. Over 5000 photomultiplier tubes (PMTs) are employed in this experiment and developed as “two outputs” device (anode and dynode) to meet the relevant requirements. In this study, the linearity of the anode and the eighth dynode (DY8), which is limited by space charge effects and mainly related to the relative dynode voltage ratios of the PMT divider, is examined. A voltage divider for the Hamamatsu R11102 PMT is designed and a dramatically enhanced linearity is demonstrated. Test results show that this design can cover a wide dynamic range from 20 to 2×10 5 photoelectrons and achieve a peak anode current of 380 mA at a PMT gain of 10 5 , which satisfies the requirements of KM2A electromagnetic particle detectors. The circuit design has been successfully simulated using the simulation software Multisim. The details of PMT performance tests and simulations are described

  16. The PhE4-49B photomultiplier spply providing the protection from the geomagnetic field

    International Nuclear Information System (INIS)

    Georgiev, V.V.; Gladyshev, V.A.

    1980-01-01

    To protect a scintillation detector from the effect of the geomagnetic field it is proposed to use an experimentally selected voltage divider in the FEhU-49B photomultiplier supplying circuit. Employment of such a divider makes it possible to increase the electrostatic field strength in the photomultiplier input chamber which ensures better collection of photoelectrons on the first dynode, to decrease effect of the magnetic field on electron focusing and to increase the first dynode secondary emission coefficient. Selection of photomultiplier supplying conditions is carried out experimentally on a scintillation counter with a plastic scintillator. The potentials of the focusing electrode and the first dynode are adjusted so that the relation between the counting rate at a photomultiplier orientation along the magnetic field lines of force and the counting rate at normal orientation to the lines of force is minimum. Usage of the experimentally selected voltage divider improves the scintillation counter time resolution and decreases the photomultiplier operating supply voltage by 100-150 V. The scintillation counter provided with a proposed divider requires no magnetic shields [ru

  17. The calibration and electron energy reconstruction of the BGO ECAL of the DAMPE detector

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhiyong; Wang, Chi; Dong, Jianing; Wei, Yifeng [State Key Laboratory of Particle Detection and Electronics (IHEP-USTC), University of Science and Technology of China, Hefei 230026 (China); Wen, Sicheng [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210000 (China); Zhang, Yunlong, E-mail: ylzhang@ustc.edu.cn [State Key Laboratory of Particle Detection and Electronics (IHEP-USTC), University of Science and Technology of China, Hefei 230026 (China); Li, Zhiying; Feng, Changqing; Gao, Shanshan; Shen, ZhongTao; Zhang, Deliang; Zhang, Junbin; Wang, Qi; Ma, SiYuan; Yang, Di; Jiang, Di [State Key Laboratory of Particle Detection and Electronics (IHEP-USTC), University of Science and Technology of China, Hefei 230026 (China); Chen, Dengyi; Hu, Yiming [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210000 (China); Huang, Guangshun; Wang, Xiaolian [State Key Laboratory of Particle Detection and Electronics (IHEP-USTC), University of Science and Technology of China, Hefei 230026 (China); and others

    2016-11-11

    The DArk Matter Particle Explorer (DAMPE) is a space experiment designed to search for dark matter indirectly by measuring the spectra of photons, electrons, and positrons up to 10 TeV. The BGO electromagnetic calorimeter (ECAL) is its main sub-detector for energy measurement. In this paper, the instrumentation and development of the BGO ECAL is briefly described. The calibration on the ground, including the pedestal, minimum ionizing particle (MIP) peak, dynode ratio, and attenuation length with the cosmic rays and beam particles is discussed in detail. Also, the energy reconstruction results of the electrons from the beam test are presented.

  18. Study of the intrinsic background noise of a quadrupole mass spectrometer

    International Nuclear Information System (INIS)

    Sysoev, A.A.; Islamov, I.M.; Khafizov, R.S.

    1977-01-01

    A proper background noise of a quadrupole mass-spectrometer is studied. The main sources of the noise have been analysed as well as their contributions to the overall noise of the device. It is shown that the main contribution is made by the photocurrent of the first dynode of the secondary-electron multiplier from ultraviolet radiation. The construction of the detecting system of the mass-spectrometer is given allowing one to increase the signal-to-noise ratio by a factor of > 500

  19. Actively-stabilized photomultiplier tube base for vacuum operation

    International Nuclear Information System (INIS)

    Bryan, M.A; Morris, C.L.; Idzorek, G.C.

    1992-01-01

    An actively stabilized photomultiplier tube (PMT) base design for an Amperex XP-2262B PMT is described. Positive-negative-positive transistors are used as low-impedance current sources to maintain constant voltages on the last three dynodes. This technique results in a highly stable, low-power tube base ideal for use with low-duty-factor beams, such as those found at the Clinton P. Anderson Meson Physics Facility. Furthermore, because of the low power usage of this large design, these bases can be sealed in a heat-conductive, electrically insulating material and used in a vacuum

  20. photomultiplier tube

    CERN Multimedia

    A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are used in all detectors based on scintillating material (i.e. based on large numbers of fibres which produce scintillation light at the passage of a charged particle). A photomultiplier consists of 3 main parts: firstly, a photocathode where photons are converted into electrons by the photoelectric effect; secondly, a multiplier chain consisting of a serie of dynodes which multiply the number of electron; finally, an anode, which collects the resulting current.

  1. photomultiplier tubes

    CERN Multimedia

    photomultiplier tubes. A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are used in all detectors based on scintillating material (i.e. based on large numbers of fibres which produce scintillation light at the passage of a charged particle). A photomultiplier consists of 3 main parts: firstly, a photocathode where photons are converted into electrons by the photoelectric effect; secondly, a multiplier chain consisting of a serie of dynodes which multiply the number of electron; finally, an anode, which collects the resulting current.

  2. photomultiplier tube

    CERN Multimedia

    photomultiplier tubes. A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are used in all detectors based on scintillating material (i.e. based on large numbers of fibres which produce scintillation light at the passage of a charged particle). A photomultiplier consists of 3 main parts: firstly, a photocathode where photons are converted into electrons by the photoelectric effect; secondly, a multiplier chain consisting of a serie of dynodes which multiply the number of electron; finally, an anode, which collects the resulting current.

  3. photomultiplier tube

    CERN Multimedia

    Philips. 150AVP. A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are used in all detectors based on scintillating material (i.e. based on large numbers of fibres which produce scintillation light at the passage of a charged particle). A photomultiplier consists of 3 main parts: firstly, a photocathode where photons are converted into electrons by the photoelectric effect; secondly, a multiplier chain consisting of a serie of dynodes which multiply the number of electron; finally, an anode, which collects the resulting current.

  4. Ultrafast readout of scintillating fibers using upgraded position-sensitive photomultipliers

    International Nuclear Information System (INIS)

    Onel, Y.

    1994-01-01

    Experimental results obtained with commercially available position-sensitive photomultipliers (PSPM) coupled with 0.5 mm diameter scintillating fiber arrays show some promising performances such as space resolution better than 200 μm and time resolution ∼ 1.5 ns with a detection efficiency higher than 90%. Major progress has also been recently achieved with an upgrade of a PSPM based on new grid dynode structures. Two-track spatial resolution has been studied using the upgraded PSPM. Initial studies demonstrate that two tracks separated by a minimum distance of 3 mm are resolved

  5. Fast readout of scintillating fibres using position-sensitive photomultipliers

    International Nuclear Information System (INIS)

    Agoritsas, V.; Akchurin, N.; Bergdolt, A.M.; Bing, O.; Bravar, A.; Ditta, J.; Dufournaud, J.; Dyachenko, V.A.; Giacomich, R.; Gorin, A.M.; Kuroda, K.; Magaudda, D.; Newsom, C.; Okada, K.; Onel, Y.; Penzo, A.; Rakhmatov, V.Ye.; Rykalin, V.I.; Salvato, G.; Savin, A.A.; Schiavon, P.; Sillou, D.; Solovyov, Yu.A.; Takeutchi, F.; Tareb-Reyes, M.; Vasilchenko, V.G.; Yoshida, T.; Zaychenko, A.A.

    1994-01-01

    Major progress has recently been achieved in the fast readout of scintillating fibres using position-sensitive photomultipliers (PSPMs). Experimental results obtained with commercially available PSPMs already show a space resolution better than 200 μm, a time resolution of about 1.5 ns with a detection efficiency higher than 90%, and the possibility of separating double hits with a minimum distance of ∼3 mm. An upgrade of PSPMs based on new dynode structures is also in progress. Results obtained with one new PSPM prototype in a magnetic field are also presented. (orig.)

  6. Improved environmental and forensics measurements using multiple ion counters in isotope ratio mass spectrometry

    International Nuclear Information System (INIS)

    Goldberg, S.A.; Richter, S.; Schwieters, H.

    2002-01-01

    Full text: A new detector system designed for isotope ratio mass spectrometers provides improved precision on measurements of samples with very low amounts ( -11 grams) of analyte. An array of continuous dynode electron multipliers has been installed on a new ThermoFinnigan MAT Triton thermal ionization mass spectrometer acquired by the New Brunswick Laboratory. These ion counters are modifications of miniaturized, commercially-available continuous dynode electron multipliers. They can be readily installed to replace individual Faraday cups in a multi-detector mass spectrometer or bundled together and located along the detector plane with a set of Faraday cups. On the New Brunswick Laboratory mass spectrometer, nine Faraday cups, one conventional discrete dynode electron multiplier, and seven miniaturized ion counters were installed. Six of the small ion counters were bundled together and positioned on the high mass side of the Low 4 Faraday cup. One additional ion counter was positioned on the low mass side of the Low 4 Faraday cup. This arrangement allows for the simultaneous measurement of all uranium (including 233 U) or plutonium (including 244 Pu) isotopes, and allows for the measurement of larger 238 U intensities on the Faraday cup if needed. Unit mass spacing of U, Pu, or other actinides is readily achieved by the use of a mass dispersion zoom lens. The advantage of multiple ion counting is the simultaneous collection of isotopes. It overcomes many of the problems such as transient signal variation in sample emission and ionization. For a given sample, multiple ion counting generates a greater number of counts for each isotope relative to single detector ion counting and provides improved counting statistics by a factor of two or more. Initial tests indicate that the multiple ion counters exhibit high counting efficiency, a dark noise of less than 10 counts per minute and typically less than 1 count per minute, and show linear response characteristics over

  7. Study on the performance of electromagnetic particle detectors of LHAASO-KM2A

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhongquan [Shandong University, Jinan 250100 (China); Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Hou, Chao; Cao, Zhen [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Chang, Jingfan; Feng, Cunfeng; Hanapia, Erlan [Shandong University, Jinan 250100 (China); Gong, Guanghua [Tsinghua University, Beijing 100083 (China); Liu, Jia [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Lv, Hongkui [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Sheng, Xiangdong [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Shaoru [Hebei Normal University, Shijiazhuang 050024 (China); Zhu, Chengguang [Shandong University, Jinan 250100 (China)

    2017-02-11

    The electromagnetic particle detectors (EDs) for one square kilometer detector array (KM2A) of large high altitude air shower observation (LHAASO) are designed to measure the densities and arrival times of secondary particles in extensive air showers (EASs). ED is a type of plastic scintillator detector with an active area of 1 m{sup 2}. This study investigates the design and performance of prototype ED. Approximately 20 photoelectrons are collected by the 1st dynode of a photomultiplier tube (PMT). The prototype ED exhibited good detection efficiency and time resolution. The detection for the wide dynamic particle density varying from 1 to 10 000 particles/m{sup 2} is realized with the design of the PMT divider for the readout of both the anode and 6th dynode. - Highlights: • Detailed description for the design of ED in LHAASO. • Good performances of prototype ED are obtained according to the measuring results. • Detailed studies on the factors which influence the properties of ED.

  8. Cross Talk Study to the Single Photon Response of a Flat Panel PMT for the RICH Upgrade at LHCb

    CERN Multimedia

    Arnaboldi, C; Calvi, M; Fanchini, E; Gotti, C; Maino, M; Matteuzzi, C; Perego, D L; Pessina, G; Wang, J C

    2009-01-01

    The Ring Imaging CHerenkov, RICH, detector at LHCb is now readout by Hybrid Photon Detectors. In view of its upgrade a possible option is the adoption of the flat panel Photon Multipliers Tubes, PMT. An important issue for the good determination of the rings produced in the sensitive media is a negligible level of cross talk. We have experimentally studied the cross talk from the 64x64 pixels of the H9500 PMT from Hamamatsu. Results have shown that at the single photon signal level, as expected at LHCb, the statistics applied to the small number of electrons generated at the first dynode of the PMT chain leads to a cross talk mechanism that must be interpreted in term of the percentage of the number of induced signals rather than on the amplitude of the induced signals. The threshold to suppress cross talk must be increased to a significant fraction of the single photon signal for the worst case. The number of electrons generated at the first dynode is proportional to the biasing voltage. Measurements have sh...

  9. Measurement of the ratio h / e with a photomultiplier tube and a set of LEDs

    International Nuclear Information System (INIS)

    Loparco, F; Malagoli, M S; Rainò, S; Spinelli, P

    2017-01-01

    We propose a laboratory experience aimed at undergraduate physics students to understand the main features of the photoelectric effect and to perform a measurement of the ratio h / e , where h is Planck’s constant and e is the electron charge. The experience is based on the method developed by Millikan for his measurements of the photoelectric effect in the years from 1912 to 1915. The experimental setup consists of a photomultiplier tube (PMT) equipped with a voltage divider properly modified to set variable retarding potentials between the photocathode and the first dynode, and a set of LEDs emitting at different wavelengths. The photocathode is illuminated with the various LEDs and, for each wavelength of the incident light, the output anode current is measured as a function of the retarding potential applied between the cathode and the first dynode. From each measurement, a value of the stopping potential for the anode current is derived. Finally, the stopping potentials are plotted as a function of the frequency of the incident light, and a linear fit is performed. The slope and the intercept of the line allow one to respectively evaluate the ratio h / e and the ratio W / e , where W is the work function of the photocathode. (paper)

  10. Secondary Emission Calorimeter Sensor Development

    Science.gov (United States)

    Winn, David R.; Onel, Yasar

    2012-12-01

    In a Secondary Emission electron(SEe) detector module, Secondary Emission electrons (SEe) are generated from an SE surface/cathode, when charged hadronic or electromagnetic particles, particularly shower particles, penetrate an SE sampling module placed between absorber materials (Fe, Cu, Pb, W etc) in calorimeters. The SE cathode is a thin (10-50 nm thick) film (simple metal-oxides, or other higher yield materials) on the surface of a metal plate, which serves as the entrance “window” to a compact vacuum vessel (metal or metal-ceramic); this SE film cathode is analogous to a photocathode, and the SEe are similar to p.e., which are then amplified by dynodes, also is in a PMT. SE sensor modules can make use of electrochemically etched/machined or laser-cut metal mesh dynode sheets, as large as ~30 cm square, to amplify the Secondary Emission Electrons (SEe), much like those that compact metal mesh or mesh dynode PMT's use to amplify p.e.'s. The construction requirements easier than a PMT, since the entire final assembly can be done in air; there are no critical controlled thin film depositions, cesiation or other oxygen-excluded processes or other required vacuum activation, and consequently bake-out can be a refractory temperatures; the module is sealed by normal vacuum techniques (welding or brazing or other high temperature joinings), with a simple final heated vacuum pump-out and tip-off. The modules envisioned are compact, high gain, high speed, exceptionally radiation damage resistant, rugged, and cost effective, and can be fabricated in arbitrary tileable shapes. The SE sensor module anodes can be segmented transversely to sizes appropriate to reconstruct electromagnetic cores with high precision. The GEANT4 and existing calorimeter data estimated calorimeter response performance is between 35-50 Secondary Emission electrons per GeV, in a 1 cm thick Cu absorber calorimeter, with a gain per SEe > 105 per SEe, and an e/pi<1.2. The calorimeter pulse width is

  11. Measurement of sigma(pp'bar' → W) x BF(W → eν) in the CDF experiment, and single photoelectron analysis of light signals

    International Nuclear Information System (INIS)

    Fedorko, I.

    2004-01-01

    In this work, I present a measurement of the cross section of W production at collider Tevatron times branching fraction for W → eν (sigma(pp'bar' → W) x BF(W → eν)) with electron reconstructed in the forward region of the detector CDF, using combined calorimetric and tracking information. This is the first CDF measurement in the forward rapidity range and is the first step for study of W properties at large η. For the period Run II, started from autumn 2001, was made upgrade of CDF detector. The forward region (for pseudorapidity |η| > 1) was strongly affected by this upgrade. Mainly due to new silicon tracking system and new forward calorimeter. With combination of tracking detectors SVXII and ISL it is now possible to reconstruct '3D' tracks. The analysis starts from calorimeter-based selection criteria finished with sample of W candidates. This selection is followed by matching '3D' tracks (to remove remaining background) with reconstructed cluster in electromagnetic calorimeter, which is measuring not only energy, but also position of electromagnetic object by Preshower detector (part of calorimeter). Besides MET PEM trigger and tracking efficiencies were established as a helpful numbers for other analysis in forward region. The measured value of the σ x BF(W → eν) is 2.874 ± 0.034(stat) ± 0.167(sys) ± 0.172(lum)nb for data sample of integrated luminosity 64 pb -1 , taken from February 2002 until the January 2003 shutdown. Presented value is in agreement with measurements performed by CDF in the central region and with theoretical estimates. Analysis of the photomultiplier (PMT) pulse height spectra from faint light sources (usually called the single-photoelectron spectra) is of a great importance because it reveals many features and can be used to find relevant parameters of PMTs. A deconvolution method is based on a sophisticated photomultiplier response function, which takes into account also photoeffect on first dynode and non

  12. 5-1 Beam Test of the PSD EQM at CERN

    Institute of Scientific and Technical Information of China (English)

    Zhou; Yong[1; Sun; Zhiyu[1; Yu; Yuhong[1; Fang; Fang[1; Zhang; Yongjie[1

    2014-01-01

    Dark Matter Particle Explorer (DAMPE) is a powerful space telescope for high energy cosmic rays detectionsuch as -ray, electron and heavy ions. The main motivation of DAMPE is to find the evidence of dark matterexistence, and the satellite is scheduled for launching before the end of 2015.The Plastic Scintillator Detector (PSD), which is oneof the key components of the DAMPE system, has twomajor functionalities: distinguish photons from chargedparticles by anti-coincidence and measure the charge ofheavy ions. The PSD is designed and fabricated by theinstitute of modern physics, CAS. It consists of 82 plasticscintillator strips, each of which is readout by PMTat both ends, and a double-dynode readout scheme forPMT is utilized in order to cover the large dynamicrange (from H to Ca).

  13. Research of Spectrometric and Exploitation Characteristics of BGO-PMP-165 Scintiblock in Temperature Interval from +25 to -140$^{o}$C

    CERN Document Server

    Ainbund, M R; Gundorin, N A; Matveev, D V; Serov, D G

    2001-01-01

    Photomultipliers based on microchannel plates are used for fast systems which form time marks of physical setups as well as in special technical areas. It is not uncommon when they substitute traditional dynode system photomultipliers. The possibility of compatible work of the PMP-165 photomultiplier with BGO crystal which were cooled down to temperature necessary for appropriate functioning of a semiconductor Ge detector with taking into account of temperature dependencies of own PMP characteristics is investigated during experiment. Cooling down of the system from room temperature down to v140^{o}C during 8 hours is done. Lower limit of temperature which allows PMP to function properly is registered. Changes of spectrometric characteristics caused by temperature are studied.

  14. Pulse height non-linearity in LaBr3:Ce crystal for gamma ray spectrometry and imaging

    International Nuclear Information System (INIS)

    Pani, R.; Cinti, M.N.; Pellegrini, R.; Bennati, P.; Ridolfi, S.; Scafe, R.; Orsolini Cencelli, V.; De Notaristefani, F.; Fabbri, A.; Navarria, F.L.; Lanconelli, N.; Moschini, G.; Boccaccio, P.

    2011-01-01

    In this paper the response in term of pulse height linearity of two Hamamatsu photomultipliers is investigated, when coupled to a LaBr 3 :Ce scintillation crystal. The two photodetectors have high quantum efficiency and in particular 30% for R6231-01 and 42% for R7600-200 tube. The substantial difference is in the dynode structure, linear focused and metal channel for R6231 and R7600 respectively. In this work in order to verify the non-linearity effects on the pulse height distribution, due principally to the high and fast light production of LaBr 3 :Ce scintillator, we propose a 'peak by peak' procedure to calibrate the pulse height distribution. Utilizing a specific fragmentation of the calibration curve in subsets, the calculated energy values are very similar for both PMTs. This result confirmed the potentiality of the procedure to highlight the non-linearity effects on pulse height distribution.

  15. Detailed measurements and shaping of gate profiles for microchannel-plate-based X-ray framing cameras

    International Nuclear Information System (INIS)

    Landen, O.L.; Hammel, B.A.; Bell, P.M.; Abare, A.; Bradley, D.K.; Univ. of Rochester, NY

    1994-01-01

    Gated, microchannel-plate-based (MCP) framing cameras are increasingly used worldwide for x-ray imaging of subnanosecond laser-plasma phenomena. Large dynamic range (> 1,000) measurements of gain profiles for gated microchannel plates (MCP) are presented. Temporal profiles are reconstructed for any point on the microstrip transmission line from data acquired over many shots with variable delay. No evidence for significant pulse distortion by voltage reflections at the ends of the microstrip is observed. The measured profiles compare well to predictions by a time-dependent discrete dynode model down to the 1% level. The calculations do overestimate the contrast further into the temporal wings. The role of electron transit time dispersion in limiting the minimum achievable gate duration is then investigated by using variable duration flattop gating pulses. A minimum gate duration of 50 ps is achieved with flattop gating, consistent with a fractional transit time spread of ∼ 15%

  16. Experiments on a 14.5 GHz ECR source

    International Nuclear Information System (INIS)

    Hill, C.E.; Langbein, K.

    1996-01-01

    The 14.5 GHz ECR4 source supplied to CERN in the framework of the Heavy Ion Facility collaboration provided Pb 27+ operational beams to a new custom built linac in 1994. This source, which operates in the pulsed 'afterglow' mode, quickly met its design specification of 80 eμA and now provides currents >100 eμA regularly. Early source tests showed the existence of extremely stable modes of operation. In the search for higher intensities a number of experiments have been performed on plasma gas composition, RF power matching, extraction, beam pulse compression and a biased dynode. The results of these tests will be presented along with further ideas to improve source performance. (author)

  17. Performance of the inverse photoemission spectrometer with a new bandpass photon detector of narrow bandwidth and high sensitivity

    International Nuclear Information System (INIS)

    Ueda, Yoshifumi; Nishihara, Katsuhiro; Mimura, Kojiro; Hari, Yasuko; Taniguchi, Masaki; Fujisawa, Masami

    1993-01-01

    A combination of a SrF 2 entrance window and a photomultiplier with the Cu-BeO first dynode coated with KCl film realizes the bandpass photon detector with the FWHM of 0.47 eV centered at 9.43 eV and the sensitivity improved by about one order of magnitude in comparison with the detector without the KCl film. The overall energy resolution of the inverse photoemission spectrometer consisting of an electron gun with a BaO cathode and the new detector has been estimated to be 0.56 eV using polycrystalline Au. Typical counting rate is 10 2 -10 3 counts/(μA s) for unoccupied states near the Fermi level of the Au at an acceptance angle of about 0.8π sr with an Al collecting mirror. (orig.)

  18. Simulation of the transient behaviour of the Mulheim-Karlich nuclear power station and comparison with startup tests

    International Nuclear Information System (INIS)

    Burchhardt, W.; Weber, J.P.

    1987-01-01

    Among the startup tests of the Mulheim-Karlich nuclear power station an anticipated turbine trip and a rector trip have been performed. Calculations have been done for both tests by the authors using the computer codes DYNODE-P and ALMOD4. At a given reactor power the transient behavior of the plant is determined by the heat load of the once-through steam generators (OTSG), which in turn is governed by the integral control system. As expected the behavior of the plant after the trips can be exactly reproduced only if the bypass control system is completely modelled. In addition the heat transfer to the secondary side of the OTSG which governs the steam production has to be calculated close to reality. comparing the calculated results with the measured test data it is demonstrated that either code can be used to reproduce the transient behavior of the plant

  19. Design and assembly of the optical modules for phase-2 of the NEMO project

    Energy Technology Data Exchange (ETDEWEB)

    Leonora, E., E-mail: emanuele.leonora@ct.infn.it; Aiello, S.

    2013-10-11

    The NEMO collaboration team has undertaken a Phase-2 project, which aims at the realization and installation of a new infrastructure at the Capo Passero (Italy) deep-sea site at a depth of 3500 m. With this objective in mind, a fully equipped tower with 8-storey hosting two optical modules at each end is under construction. Following a well established procedure, 32 optical modules have been assembled. The optical module consists of a large area photomultiplier tube enclosed in a pressure resistant glass sphere with a diameter of 13 in. The photomultiplier is a R7081 type, produced by Hamamatsu, with a photocathode area with a diameter of 10 in. and 10 dynodes. Mechanical and optical contacts between the front of the photomultiplier tube and the glass surface are ensured by an optical bi-component silicone gel. A mu-metal cage is used to shield the photomultiplier against the influence of the Earth's magnetic field.

  20. A simple method to increase effective PMT gain by amplifier circuit powered from voltage divider

    International Nuclear Information System (INIS)

    Popov, V.; Majewski, S.; Wojtsekhowski, B.; Guerin, D

    2001-01-01

    A novel concept is introduced of additional effective signal amplification by employing a dedicated circuit to process anode or dynode signals prior to sending them through a standard 50 /spl Omega/ line/cable. The circuit is entirely powered by the current flowing through the base voltage divider. Additional gain factors of 2-10 were easily achieved with preserved operation speed and rate capability up to several MHz. This additional signal boost can be used in many applications where higher gain and/or lower PMT operational voltages are desirable. For example, in the case of a PMT employed in a low input light signal (such as a Cherenkov counter), this technique will permit operation at a lower voltage and, therefore, will result in better operational PMT stability and longer PMT lifetime. At present, two experimental set-ups at Jefferson Lab are using PMT bases using this concept

  1. Very low power, high voltage base for a Photo Multiplier Tube for the KM3NeT deep sea neutrino telescope

    International Nuclear Information System (INIS)

    Timmer, P; Heine, E; Peek, H

    2010-01-01

    The described system is developed in the framework of a deep-sea submerged Very Large Volume neutrino Telescope where photons are detected by a large number of Photo Multiplier Tubes. These PMTs are placed in optical modules (OM). A basic Cockcroft-Walton (CW) voltage multiplier circuit design is used to generate multiple voltages to drive the dynodes of the photomultiplier tube. To achieve a long lifetime and a high reliability the dissipation in the OM must be kept to the minimum. The design is also constrained by size restrictions, load current, voltage range, and the maximum allowable ripple in the output voltage. A surface mount PMT-base PCB prototype is designed and successfully tested. The system draws less than 1.5 mA of supply current at a voltage of 3.3 V with outputs up to -1400 Vdc cathode voltage, a factor 10 less than the commercially available state of the art.

  2. The Tynode: A new vacuum electron multiplier

    Energy Technology Data Exchange (ETDEWEB)

    Graaf, Harry van der, E-mail: vdgraaf@nikhef.nl [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); Akhtar, Hassan; Budko, Neil; Chan, Hong Wah; Hagen, Cornelis W. [Delft University of Technology, Delft (Netherlands); Hansson, Conny C.T. [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); Nützel, Gert; Pinto, Serge D. [Photonis, Roden (Netherlands); Prodanović, Violeta; Raftari, Behrouz; Sarro, Pasqualina M. [Delft University of Technology, Delft (Netherlands); Sinsheimer, John; Smedley, John [Brookhaven National Laboratory, Upton, NY 11973 (United States); Tao, Shuxia [Eindhoven University of Technology/DIFFER (Netherlands); Theulings, Anne M.M.G. [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); Vuik, Kees [Delft University of Technology, Delft (Netherlands)

    2017-03-01

    By placing, in vacuum, a stack of transmission dynodes (tynodes) on top of a CMOS pixel chip, a single free electron detector could be made with outstanding performance in terms of spatial and time resolution. The essential object is the tynode: an ultra thin membrane, which emits, at the impact of an energetic electron on one side, a multiple of electrons at the other side. The electron yields of tynodes have been calculated by means of GEANT-4 Monte Carlo simulations, applying special low-energy extensions. The results are in line with another simulation based on a continuous charge-diffusion model. By means of Micro Electro Mechanical System (MEMS) technology, tynodes and test samples have been realized. The secondary electron yield of several samples has been measured in three different setups. Finally, several possibilities to improve the yield are presented.

  3. R&D of a pioneering system for a high resolution photodetector: The VSiPMT

    Science.gov (United States)

    Barbato, F. C. T.; Barbarino, G.; Campajola, L.; Di Capua, F.; Mollo, C. M.; Valentini, A.; Vivolo, D.

    2017-12-01

    The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design for a hybrid photodetector. The idea, born with the purpose to use a SiPM for large detection volumes, consists in replacing the classical dynode chain with a special SiPM. In this configuration, we match the large sensitive area of a photocathode with the performances of the SiPM technology, which therefore acts like an electron detector and so like a current amplifier. The excellent photon counting capability, fast response, low power consumption and the stability are among the most attractive features of the VSiPMT.We now present the progress on the realization of a 1-in. prototype and the preliminary tests we are performing on it.

  4. The First Successful Compact Negative Heavy Ion Cyclotron

    International Nuclear Information System (INIS)

    Liu, Y.; Chen, M.; Li, D.; Lu, X.; Shen, L.; Xu, S.; Chen, G.

    1999-01-01

    A compact negative heavy ion minicyclotron has been set up in 1993 in Shanghai, China which is dedicated to the analysis of radioactive isotope 14 C. This is a new type of cyclotron with a series of gifted ideas, such as adopting triangular-wave Dee Voltage, configuring the asymmetric differential Dee electrodes with varying width and aperture, combining the yoke of the magnet with the vacuum chamber, designing a pair of the spherical electrostatic injection deflectors, adding auxiliary electrodes for extraction, alternately accelerating different particles and using Dynode-MCP detector for counting 14 C etc., all of which have aimed at increasing the transmission efficiency in the injection, acceleration and extraction region, eliminating various backgrounds and improving the precision of 14 C analysis. All of those will be introduced in this article. Finally, its operation performance and some difficulties will be discussed

  5. Very low power, high voltage base for a Photo Multiplier Tube for the KM3NeT deep sea neutrino telescope

    CERN Document Server

    Timmer, P; Peek, H

    2010-01-01

    The described system is developed in the framework of a deep-sea submerged Very Large Volume neutrino Telescope where photons are detected by a large number of Photo Multiplier Tubes. These PMTs are placed in optical modules (OM). A basic Cockcroft-Walton (CW) voltage multiplier circuit design is used to generate multiple voltages to drive the dynodes of the photomultiplier tube. To achieve a long lifetime and a high reliability the dissipation in the OM must be kept to the minimum. The design is also constrained by size restrictions, load current, voltage range, and the maximum allowable ripple in the output voltage. A surface mount PMT-base PCB prototype is designed and successfully tested. The system draws less than 1.5 mA of supply current at a voltage of 3.3 V with outputs up to -1400 Vdc cathode voltage, a factor 10 less than the commercially available state of the art

  6. An approach for high voltage power supply system for HCAL of LHCb experiment

    International Nuclear Information System (INIS)

    Cimpean, A.; Dumitru, D.; Kluger, A.; Magureanu, C.; Tarta, D.; Coca, C.; Orlandea, M.; Popescu, S.

    2003-01-01

    The main aim of the calorimeter system of the LHCb (Large Hadron Collider Beauty) experiment dedicated to precision measurements of CP violation and rare phenomena is to provide identification of the electrons, hadrons and photons, for the level-0 trigger and offline analysis with measurements of position and energy. The system consists in a scintillator pad/preshower (SPD/PS) detector, an electromagnetic calorimeter (ECAL) and a hadron calorimeter (HCAL), all the sub-detectors having a similar technology with scintillating tiles as active material and being read out via wavelength-shifting fibers and with an identical readout electronics for ECAL and HCAL and similar electronics for the PS. During 1997-1999 a computer controlled High Voltage (HV) distribution scheme was developed by Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH) group and used to supply the PMTs of half HCAL prototype during the beam tests (1998-2000). This scheme consisted of three parts: 1) a control box which includes low voltage power supply, the RS232 interface to a PC and three modules of high voltage power supply; 2) two types of multichannel HV distributors with an individual voltage setting; 3) a software package to control all settings and refresh them periodically. Based on the acquired experience, a new design for a High Voltage Power Supply (HVPS) which satisfies the LHCb requirements has been developed for PMTs of the hadron calorimeter. The demands of this system are simplicity and low cost. This HVPS with multiple outputs (HV for photocathode and D1 - D4 dynodes) is destined to supply, with the same high voltage, groups of PMTs sorted by similar characteristics as gain and sensitivity. Because of the high rates (∼ 40 MHz) supported by PMTs, booster voltage sources are necessary to supply current for the last 4 dynodes. The box has 5 HV power supplies for photocathodes and the last 4 dynodes, each HV power supply being followed by a 4 channel

  7. Optical signatures of discharges in parallel coupled DC accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Rajan, Rehim N.; Banerjee, Srutarshi; Acharya, S.N., E-mail: rehim@barc.gov.in [Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Mumbai (India); and others

    2014-07-01

    Parallel coupled voltage multiplier based accelerator topologies offer advantages of better regulation and ripple compared to their series coupled counterparts for Industrial electron beam accelerators. During conditioning and operation these systems undergoes various types of electrical discharges. The discharge can be a direct spark over from the high voltage terminal to ground through SF{sub 6} insulation, vacuum breakdown in the accelerating tube maintained in the order of 10{sup -7} mbar pressure, or local discharge between corona guards which are used to couple RF power to the multiplier. There could be discharges in between dynodes of the accelerating tube. As the inter electrode discharges do not reflect in load current, detection of these conditions becomes very difficult. Optical discharge detection methods can be used effectively in this situation. Photo multiplier based optical discharge detection has been deployed in a 3 MeV DC accelerator. Characteristics of the optical signal received during conditioning phase have been presented in this paper. (author)

  8. Measurement of amplitude fluctuations in a rapid response photomultiplier

    International Nuclear Information System (INIS)

    Raimbault, P.

    1961-01-01

    In order to measure amplitude fluctuations in a rapid response photomultiplier, two independent random variables are introduced which determine the shape of the anode pulse. The energy of each pulse, which depends directly on the gain and the variance, is the first variable; amplitude fluctuations, functions of the first variable, depend as well on the pulse width which in turn constitutes the second variable. The results obtained on the variations of the maximum impulse, using a steep-edged pulse broadening circuit, and those obtained on the statistical variations of the gain, are compared to show that the variance relative to the maximum amplitude of the signal is greater than that of the gain. Within the limits of these fluctuations are shown the contribution of the secondary emission coefficient of the first dynode, and that of the mean secondary emission coefficient of the multiplier. (author) [fr

  9. Mean secondary electron yield of avalanche electrons in the channels of a microchannel plate detector

    International Nuclear Information System (INIS)

    Funsten, H.O.; Suszcynsky, D.M.; Harper, R.W.

    1996-01-01

    By modeling the statistical evolution of an avalanche created by 20 keV protons impacting the input surface of a z-stack microchannel plate (MCP) detector, the mean secondary electron yield γ C of avalanche electrons propagating through a MCP channel is measured to equal 1.37 for 760 V per MCP in the z stack. This value agrees with other studies that used MCP gain measurements to infer γ C . The technique described here to measure γ C is independent of gain saturation effects and simplifying assumptions used in the segmented dynode model, both of which can introduce errors when inferring γ C through gain measurements. copyright 1996 American Institute of Physics

  10. Effects of Changing Hot Rolling Direction on Microstructure, Texture and Mechanical Properties of Cu-2.7Be Sheets

    Science.gov (United States)

    Zhu, Daibo; Liu, Chuming; Yu, Haijun; Han, Tan

    2018-03-01

    A hot rolling scheme (cross-rolling and unidirectional rolling) was adopted to process Cu-2.7Be sheets used as multiplier dynodes in photomultiplier. The effects of changing rolling direction on microstructure, texture and mechanical properties were studied by a combination of XRD, EBSD and TEM. It was found that higher copper-type texture and lower brass texture intensity were obtained in the ultimately cross-rolling (CR) sheet compared with the unidirectional rolling (UR) sheet.The EBSD results indicated that the grain orientation from mainly for UR sample turns to random for CR sample. Great enhancements in YS and UTS after unidirectional rolling were attributed to the massive and polygonal γ precipitates. The CR sample exhibited lower anisotropy, because of the increase of S and γ precipitates with spherical and tiny shape.

  11. New Very Low Noise Multilayer And Graded-Gap Avalanche Photodiodes For The 0.8 To 1 .8 μm Wavelength Region

    Science.gov (United States)

    Capasso, F.; Tsang, W. T.; Williams, G. F.

    1982-12-01

    Recent experimental and theoretical results on a new class of low noise avalanche photo-diodes are reviewed. A large enhancement of the impact ionization rates ratio (a/(3=10) has been demonstrated in AlGaAs/GaAs superlattices and graded band gap detector structures. In addition two novel photodiodes ("staircase" and "channeling" APDs) where only electrons multiply, have been proposed. The staircase APD is the solid state analog of the photo-multiplier with discrete dynodes. It has a low operating voltage (5-20 volts) and a lower excess noise factor, in the ideal case, than that of an ideal conventional APD The channeling APD is instead the solid state analog of a channeltron photomultiplier and has the unique feature of an ultrahigh a/β, ratio (≍∞) compatible with high gain (>100).

  12. The device for measuring amplitude spectra of ionizing irradiation

    International Nuclear Information System (INIS)

    Polyak, Yu.V.; Nebesnyj, A.F.

    1996-01-01

    The front-end electronic device for measuring of amplitude spectra of ionizing radiation have been made. The device have connection interface with the ionizing radiation detector, the pulse former, adapter, memory, electron ray tube with diode, supply unit and the regime setting unit of the work of electron ray tube. There are linear transmission scheme, level discriminator, pulse series - channel code converter, dividing capacitor in the device. Dynode of electron ray tube has been made in the form of rack or pads installed in the line parallel to axis of vertical scanning and electrically joined with each other. The distance between next tooth of rack or pads is Δy≥0,5 d, where d - diameter of focused electron beam of electron ray tube. The output of pulse former is joined with level discriminator and the first entrance of linear transmission scheme. The output of linear transmission scheme is joined with the entrance of pulse delay scheme, and the second entrance is joined with the first output of level discriminator. The output of pulse delay scheme is joined with Y-deflecting plate of electron ray tube. The first and the second entrance of pulse series - channel code converter are joined correspondingly with the output of adapter and the second output of level discriminator, and its output - with the entrance of memory unit. The first pin of loading resistor is joined through dividing capacitor with the entrance of adapter, its second pin - with the anode output nearest to dynode of electron ray tube. (E.V.Kh.)

  13. UNCONTROLLED PHOTOMULTIPLIER CURRENT IN PHOTOEMISSION ANALYSIS

    Directory of Open Access Journals (Sweden)

    K. A. Viazava

    2016-01-01

    Full Text Available The dependence of photon energy from energy of photoelectron is base of photoemission radiation analysis. In such photoemission measurements except current of photocathode is always exist a reverse current from the collector of electrons to the photocathode in two-electrode sensors. There are various ways of reverse and uncontrolled current eliminating or reducing their influence. The constructive method is based on creating an electron-optical system of photoelectronic device, which would be a photoelectron energy analyzer. The second method – technological. However, it requires the manufacture of the photocathode and the dynode system in different vacuum chamber with subsequent connection to a single device in vacuum environment without exposure to the atmosphere. The purpose of this article is to determinate the effect of photoemission from photocathode chamber and the first dynode of photomultiplier on energy distribution of the photoelectrons from photocathode. To solve this problem authors obtained calibration curves for measuring pyrometer module ПИФ 4/2 with ФЭУ-114 as a sensor at supply voltage 1350 V and different decelerating voltages. The effect of illumination on the value of modulation coefficient on temperature k(T and wavelength k(λ is shown. In temperature measurements, this effect is evident in fact that at temperatures below 1400 K linear dependence ln k – T-1 is broken. Still this linear dependence is a necessary consequence of the fact that the measured temperature is color temperature. However, this calibration curve can be used to measure low temperature if the target measurements condition and calibration conditions are identical. In wavelength calibration, curve k(λ at λ > 760 nm is two-valued, that doesn’t allow to identify monochromatic radiation by this method and bring in errors in temperature measurements. 

  14. Measurement of amplitude fluctuations in a rapid response photomultiplier; Mesure des fluctuations d'amplitude d'un photo multiplicateur a reponse rapide

    Energy Technology Data Exchange (ETDEWEB)

    Raimbault, P [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1961-07-01

    In order to measure amplitude fluctuations in a rapid response photomultiplier, two independent random variables are introduced which determine the shape of the anode pulse. The energy of each pulse, which depends directly on the gain and the variance, is the first variable; amplitude fluctuations, functions of the first variable, depend as well on the pulse width which in turn constitutes the second variable. The results obtained on the variations of the maximum impulse, using a steep-edged pulse broadening circuit, and those obtained on the statistical variations of the gain, are compared to show that the variance relative to the maximum amplitude of the signal is greater than that of the gain. Within the limits of these fluctuations are shown the contribution of the secondary emission coefficient of the first dynode, and that of the mean secondary emission coefficient of the multiplier. (author) [French] Pour etudier les fluctuations d'amplitude d'un photomultiplicateur a reponse rapide, on introduit deux variables aleatoires independantes qui determinent la forme de l'impulsion anodique. L'energie de chaque impulsion, directement fonction du gain et de sa variance, est la premiere variable; les fluctuations d'amplitude, fonctions de la premiere variable, dependent egalement de la largeur de l'impulsion qui, elle, constitue la deuxieme variable. Les resultats obtenus sur les variations de l'amplitude maximale, a l'aide d'un circuit elargisseur d'impulsions a front raide, et les resultats des variations statistiques du gain sont compares pour mettre en evidence le fait que la variance relative a l'amplitude maximale du signal est plus grande que celle du gain. Dans la mesure de ces fluctuations, sont mises en evidence la contribution du coefficient d'emission secondaire de la premiere dynode et celle du coefficient d'emission secondaire moyen du multiplicateur. (auteur)

  15. Electron multiplier for the measurement of an ion current on a mass spectrometer; Multiplicateur d'electrons pour la mesure de courant d'ions sur un spectrometre de masse

    Energy Technology Data Exchange (ETDEWEB)

    Lohez, P; Nief, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1957-07-01

    The apparatus described is designed to measure weak ion currents received at the collector of a mass spectrometer. The report describes successively the study of electron paths in the multiplier by the method of analogy, using rubber membranes, and the practical details of construction of the apparatus. The variation with surface treatment of the secondary emission coefficient of the alloy CuBe containing 2 per cent Be, which makes up the dynodes, and the influence of the voltage on the gain per stage, are discussed. Results of tests regarding: the influence of the ion mass on the gain, the background of the instrument and the energy distribution of the impulses coming out on a high gain multiplier (q.q. 10{sup 7}) are given. Finally the performances of the multiplier are reported. 1- For a low gain (10{sup 4}), precision and reproducibility comparable to the electrometer valve, sensitivity 100 times greater, currents capable of detection 10{sup -17} Ampere. 2- For a high gain (10{sup 7}) and measurement by impulse counting, currents capable of detection 10{sup -19} Ampere. Mounting difficult to use on a mass spectrometer. (author) [French] L'appareil decrit est destine a la mesure des faibles courants d'ions re s au collecteur d'un spectrometre de masse. Le rapport decrit successivement l'etude des trajectoires des electrons dans le multiplicateur, par la methode analogique de la menbrane en caoutchouc, et la realisation pratique de l'appareil. La variation du coefficient d'emission secondaire de l'alliage CuBe a 2 pour cent de Be, constituant les dynodes suivant le traitement des surfaces, et l'influence de la tension sur le gain par etage sont discutees. Des resultats d'essais concernant: l'influence de la masse des ions sur le gain, le bruit de fond de l'appareil et la repartition en energie des impulsions de sortie sur un multiplicateur a gain eleve (q.q. 10{sup 7}) sont donnes. Enfin, sont rapportees les performances du multiplicateur. 1- pour un gain faible

  16. Secondary emission scintillation counter for microdosimetry at the nanometer level

    International Nuclear Information System (INIS)

    Goldhagen, P.

    1987-01-01

    The secondary emission scintillation (SES) counter is a device designed to count the positive ions of charged-particle tracks in gas volumes simulating sites in tissue with diameters of the order of 1 nanometer. Based on suggestions by H.H. Rossi and A.M. Kellerer, the basic idea of the device was developed by A. Kosiara, M. Biavati, and R.D. Colvett in the late 1970s. The device was substantially modified in 1982, but work on it was suspended before the new version could be tested, in order to devote full-time effort to rebuilding RARAF. Work resumed on the SES counter in 1986. A diagram of the prototype SES counter now being tested is shown. A weak electric field in the cylindrical collection region of the device drifts ions from a track to a small region (less than 1 mm) of high electric field where they are accelerated by several kilovolts onto a dynode, producing secondary electrons. The secondary electrons are then accelerated onto a plastic scintillator, and the resulting light is detected by a photomultiplier. The passage of a charged particle is established by a solid state detector, which triggers electronics detecting coincidences and measuring the timing and amplitude of pulses from the photomultiplier

  17. Evaluation of flat panel PMT for gamma ray imaging

    International Nuclear Information System (INIS)

    Pani, R.; Cinti, M.N.; Pellegrini, R.; Trotta, C.; Trotta, G.; Montani, L.; Ridolfi, S.; Garibaldi, F.; Scafe, R.; Belcari, N.; Del Guerra, A.

    2003-01-01

    The first position sensitive PMT, Hamamatsu R2486, developed in 1985, represented a strong technological advance for gamma-ray imaging. Hamamatsu H8500 Flat Panel PMT is the last generation position sensitive PMT: extremely compact with 2 in. active area. Its main features are: minimum peripheral dead zone (1 mm) and height of 12 mm. It was designed to be assembled in array to cover large detection area. It can represent a technical revolution for many applications in the field of gamma-ray imaging as for example nuclear medicine. This tube is based on metal channel dynode for charge multiplication and 8x8 anodes for charge collection and position calculation. In this paper we present a preliminary evaluation of the imaging performances addressed to nuclear medicine application. To this aim we have taken into account two different electronic readouts: resistive chain with Anger Camera principle and multianode readout. Flat panel PMT was coupled to CsI(Tl) and NaI(Tl) scintillation arrays. The results were also compared with the first generation PSPMT

  18. Gallium nitride at the millennial transition

    International Nuclear Information System (INIS)

    Pankovo, J.I.

    2000-01-01

    The properties of gallium nitride were uncovered in the early years of exploratory research and endowed with negative electron affinity that could be used to make efficient cold cathodes and even dynodes for electron multipliers. GaN has another property i.e. polar nature of the crystal which makes this material piezo-electric and has non-linear optical properties. The piezo-electric properties led to new piezo electric effect may cause interfacial charge. The non-uniform distribution of acceptors, there is also presence of threading and other dislocation in GaN. Defects reappear where two adjacent overgrowth merge, but the good lateral overgrow region is large enough to make lasers. Injection lasers benefit from strong electrical and optical environment. This was achieved by using quantum wells of InGaN in GaN and this can be doped with rare earth elements to exploit the atomic transition between core levels in these elements. The emission efficiency of electrically excited Er in GaN is nearly temperature incentive from 80K to room temperature. An other application of GaN is as a heterojunction emitter for a bi-polar transistor (HBT) that can operate at high temperatures. (A.B.)

  19. Investigation about decoupling capacitors of PMT voltage divider effects on neutron-gamma discrimination

    International Nuclear Information System (INIS)

    Divani, Nazila; Firoozabadi, Mohammad M.; Bayat, Esmail

    2014-01-01

    Scintillators are almost used in any nuclear laboratory. These detectors combine of scintillation materials, PMT and a voltage divider. Voltage dividers are different in resistive ladder design. But the effect of decoupling capacitors and damping resistors haven’t discussed yet. In this paper at first a good equilibrium circuit designed for PMT, and it was used for investigating about capacitors and resistors in much manner. Results show that decoupling capacitors have great effect on PMT output pulses. In this research, it was tried to investigate the effect of Capacitor’s value and places on PMT voltage divider in Neutron-Gamma discrimination capability. Therefore, the voltage divider circuit for R329-02 Hamamatsu PMT was made and Zero Cross method used for neutron-gamma discrimination. The neutron source was a 20Ci Am-Be. Anode and Dynode pulses and discrimination spectrum were saved. The results showed that the pulse height and discrimination quality change with the value and setting of capacitors

  20. Gain uniformity, linearity, saturation and depletion in gated microchannel-plate x-ray framing cameras

    International Nuclear Information System (INIS)

    Landen, O.L.; Bell, P.M.; Satariano, J.J.; Oertel, J.A.; Bradley, D.K.

    1994-01-01

    The pulsed characteristics of gated, stripline configuration microchannel-plate (MCP) detectors used in X-ray framing cameras deployed on laser plasma experiments worldwide are examined in greater detail. The detectors are calibrated using short (20 ps) and long (500 ps) pulse X-ray irradiation and 3--60 ps, deep UV (202 and 213 nm), spatially-smoothed laser irradiation. Two-dimensional unsaturated gain profiles show 5 in irradiation and fitted using a discrete dynode model. Finally, a pump-probe experiment quantifying for the first time long-suspected gain depletion by strong localized irradiation was performed. The mechanism for the extra voltage and hence gain degradation is shown to be associated with intense MCP irradiation in the presence of the voltage pulse, at a fluence at least an order of magnitude above that necessary for saturation. Results obtained for both constant pump area and constant pump fluence are presented. The data are well modeled by calculating the instantaneous electrical energy loss due to the intense charge extraction at the pump site and then recalculating the gain downstream at the probe site given the pump-dependent degradation in voltage amplitude

  1. Micro-channel plates and vacuum detectors

    Energy Technology Data Exchange (ETDEWEB)

    Gys, T., E-mail: Thierry.Gys@cern.ch

    2015-07-01

    A micro-channel plate is an array of miniature electron multipliers that are each acting as a continuous dynode chain. The compact channel structure results in high spatial and time resolutions and robustness to magnetic fields. Micro-channel plates have been originally developed for night vision applications and integrated as an amplification element in image intensifiers. These devices show single-photon sensitivity with very low noise and have been used as such for scintillating fiber tracker readout in high-energy physics experiments. Given their very short transit time spread, micro-channel plate photomultiplier tubes are also being used in time-of-flight and particle identification detectors. The present paper will cover the history of the micro-channel plate development, basic features, and some of their applications. Emphasis will be put on various new manufacturing processes that have been developed over the last few years, and that result in a significant improvement in terms of efficiency, noise, and lifetime performance.

  2. Applications of High Speed Configurable Logic Devices in Modern Particle Physics Experiments

    CERN Document Server

    Giorgi, Filippo Maria

    Several activities were conducted during my PhD activity. For the NEMO experiment a collaboration between the INFN/University groups of Catania and Bologna led to the development and production of a mixed signal acquisition board for the Nemo Km3 telescope. The research concerned the feasibility study for a different acquisition technique quite far from that adopted in the NEMO Phase 1 telescope. The DAQ board that we realized exploits the LIRA06 front-end chip for the analog acquisition of anodic an dynodic sources of a PMT (Photo-Multiplier Tube). The low-power analog acquisition allows to sample contemporaneously multiple channels of the PMT at different gain factors in order to increase the signal response linearity over a wider dynamic range. Also the auto triggering and self-event-classification features help to improve the acquisition performance and the knowledge on the neutrino event. A fully functional interface towards the first level data concentrator, the Floor Control Module, has been integrated...

  3. Influence of incident light wavelength on time jitter of fast photomultipliers

    International Nuclear Information System (INIS)

    Moszynski, M.; Vacher, J.

    1977-01-01

    The study of the single photoelectron time resolution as a function of the wavelength of the incident light was performed for a 56 CVP photomultiplier having an S-1 photocathode. The light flash from the XP22 light emitting diode generator was passed through passband filters and illuminated the 5 mm diameter central part of the photocathode. A significant increase of the time resolution above 30% was observed when the wavelength of the incident light was changed from 790 nm to 580 nm. This gives experimental evidence that the time jitter resulting from the spread of the initial velocity of photoelectrons is proportional to the square root of the maximal initial energy of photoelectrons. Based on this conclusion the measured time jitter of C31024, RCA8850 and XP2020 photomultipliers with the use of the XP22 light emitting diode at 560 nm light wavelength was recalculated to estimate the time jitter at 400 nm near the maximum of the photocathode sensitivity. It shows an almost twice larger time spread at 400 nm for the C31024 and RCA8850 with a high gain first dynode and an about 1.5 times larger time spread for the XP2020 photomultiplier, than those measured at 560 nm. (Auth.)

  4. New prototype scintillator detector for the Tibet ASγ experiment

    Science.gov (United States)

    Zhang, Y.; Gou, Q.-B.; Cai, H.; Chen, T.-L.; Danzengluobu; Feng, C.-F.; Feng, Y.-L.; Feng, Z.-Y.; Gao, Q.; Gao, X.-J.; Guo, Y.-Q.; Guo, Y.-Y.; Hou, Y.-Y.; Hu, H.-B.; Jin, C.; Li, H.-J.; Liu, C.; Liu, M.-Y.; Qian, X.-L.; Tian, Z.; Wang, Z.; Xue, L.; Zhang, X.-Y.; Zhang, Xi-Ying

    2017-11-01

    The hybrid Tibet AS array was successfully constructed in 2014. It has 4500 m2 underground water Cherenkov pools used as the muon detector (MD) and 789 scintillator detectors covering 36900 m2 as the surface array. At 100 TeV, cosmic-ray background events can be rejected by approximately 99.99%, according to the full Monte Carlo (MC) simulation for γ-ray observations. In order to use the muon detector efficiently, we propose to extend the surface array area to 72900 m2 by adding 120 scintillator detectors around the current array to increase the effective detection area. A new prototype scintillator detector is developed via optimizing the detector geometry and its optical surface, by selecting the reflective material and adopting dynode readout. {This detector can meet our physics requirements with a positional non-uniformity of the output charge within 10% (with reference to the center of the scintillator), time resolution FWHM of ~2.2 ns, and dynamic range from 1 to 500 minimum ionization particles}.

  5. A scintillation detector set measuring the charge particle energy

    International Nuclear Information System (INIS)

    Dore, Chantal.

    1979-01-01

    The S143 experiment, at CERN in 1976, needed both the measurement and the identification of light nuclei, and especially the separation between 3 H and 3 He, over a large energy range. In the chosen solution, in addition to semiconductor detectors, some scintillation counters are used. The non-linearity of light versus energy of charged particles was complicated by the fact there was two different linear laws according to the charge of particles. To obtain good analogic signals over a dynamic range nearly equal to 200, the signals from several dynodes were used simultaneously. In the experimental setting up, each scintillator was put directly in contact with the corresponding photocathode. In spite of a special shielding, some perturbations due to the magnet placed close by required to bring important corrections to linear laws. Thanks to complementary informations from semiconductor counters, a full separation between charge 1 and charge 2 particles was possible. A suitable identification as guaranted among charge 1 particles, but only kinematic constraints gave the possibility to extract 4 He corresponding to the elastic scattering [fr

  6. Construction and tests of a fine granularity lead-scintillating fibers calorimeter

    International Nuclear Information System (INIS)

    Branchini, P; Di Micco, B; Passeri, A; Ceradini, F; Corradi, G

    2009-01-01

    We report the construction and the tests of a small prototype of the lead-scintillating fiber calorimeter of the KLOE experiment, instrumented with multianode photomultipliers to obtain a 16 times finer readout granularity. The prototype is 15 cm wide, 15 radiation lengths deep and is made of 200 layers of fibers 50 cm long. On one side it is read out with an array of 3x5 multianode photomultipliers Hamamatsu type R8900-M16, each segmented with 4x4 anodes, the read out granularity being 240 pixels of 11 x 11 mm 2 corresponding to about 64 scintillating fibers each. These are interfaced to the 6 x 6 mm 2 pixeled photocathode with truncated pyramid light guides made of Bicron BC-800 plastic to partially transmit the UV light. Each photomultiplier provides also an OR of the 16 last dynodes that is used for trigger. The response of the individual anodes, their relative gain and cross-talk has been measured with the light (440 nm) of a laser illuminating only few fibers on the side opposite to the readout. We finally present the first results of the calorimeter response to cosmic rays in auto-trigger mode.

  7. Simple ways of n-γ discrimination using charge comparison technique

    International Nuclear Information System (INIS)

    Jhingan, Akhil; Singh, Hardev; Singh, R.P.; Golda, K.S.; Sugathan, P.; Mandal, S.; Bhowmik, R.K.

    2008-01-01

    The charge comparison method for n-γ discrimination has been in practice for more than two decades; technically it can be implemented in variety of ways. We present explicitly, in detail, two simple ways of implementing this technique. The first one is the conventional way of comparing the fractional or slow charge in the tail with the full charge of photomultiplier tubes (PMTs) anode pulse fed to a charge integrating ADC or QDC, but has been electronically implemented in a new fashion. The second one is a novel technique of comparing shaped-dynode pulse, fed to a peak-sensing ADC, with the fractional slow charge integrated in QDC. This technique reduces the complexity of individual gate generation, and thus reduces the number of gate and delay generators, compared with the first case. To implement these techniques, we have designed and fabricated a six-channel, single-width NIM module for use with QDC for n-γ discrimination. The module fabrication is very simple and inexpensive, and can be easily integrated with commercially available high-density NIM and CAMAC modules in experimental setups involving a large number of neutron detectors. Commercially available passive analog delay line chips have been used for delaying analog signals fed to the QDC. To simplify the setup for high-density applications we have replaced the constant fraction discriminator (CFD) by a fast leading-edge discriminator. The quality of n-γ discrimination obtained is comparable with that reported earlier in the literature

  8. The effect of the rotational orientation of circular photomultipliers in a PET camera block detector design

    International Nuclear Information System (INIS)

    Uribe, J.; Wong, Wai-Hoi; Hu, Guoju

    1996-01-01

    This is a study of the effects of geometric asymmetries in circular photomultipliers (PMT) on the design of PET position-sensitive block detectors. The dynodes of linear-focus circular PMT's are asymmetric relative to the axis of the photocathode, despite the rotational symmetry of the photocathode. Hence, there are regional photocathode differences in the anode signal, which affect the decoding characteristics of position sensitive block detectors. This orientation effect, as well as the effect of introducing light diffusers, are studied in a block detector design (BGO) using the PMT-quadrant-sharing configuration. The PMT studied is the Philips XP-1911 (19mm diameter). Seven symmetrical and representative orientations of the four decoding PMT were investigated, as well as one asymmetric orientation. The measurements performed include block-composite pulse-height spectra and crystal decoding maps. Two orientation effects were observed: (A) distortion variation in decoding maps, and (B) decoding resolution variation. The introduction of circular plastic pieces, used as light diffusers, prove to be useful by improving the decoding of crystals on the periphery of the detector block and minimizing distortion in the decoding map. These measurements have shown optimal PMT orientations for the PMT-quadrant-sharing design, as well as for conventional block designs

  9. Multisector scintillation detector with fiber-optic light collection

    Science.gov (United States)

    Ampilogov, N. V.; Denisov, S. P.; Kokoulin, R. P.; Petrukhin, A. A.; Prokopenko, N. N.; Shulzhenko, I. A.; Unatlokov, I. B.; Yashin, I. I.

    2017-07-01

    A new type of scintillation detector for the use in high energy physics is described. The octagonal detector consists of eight triangular scintillator sectors with total area of 1 m2. Each sector represents two plates of 2 cm thick plastic scintillator. Seven 1 mm thick WLS fibers are laid evenly between the plates. The space between the fibers is filled with silicone compound to provide better light collection. Fiber ends from all eight sectors are gathered in the central part of the detector into a bunch and docked to the cathode of a FEU-115m photomultiplier. The read-out of the counter signals is carried out from 7th and 12th dynodes, providing a wide dynamic range up to about 10000 particles. The front-end electronics of the detector is based on the flash-ADC with a sampling frequency of 200 MHz. The features of detecting and recording systems of the multisector scintillation detector (MSD) and the results of its testing are discussed.

  10. Dual parameter analysis of CsI:Tl/PMT with a digital oscilloscope

    CERN Document Server

    Devol, T A; Fjeld, R A

    1999-01-01

    Scintillation pulses from alpha-particle and gamma-ray excited CsI:Tl were recorded with a photomultiplier tube and digital oscilloscope card in single parameter (pulse shape or pulse height) and dual parameter (simultaneous pulse shape and pulse height) modes. A 2.8x1.3x1.3 cm sup 3 CsI:Tl crystal was coupled to a Burle 8850 photomultiplier tube (PMT) and excited with sup 1 sup 4 sup 8 Gd (E subalpha=3.18 MeV) and sup 1 sup 3 sup 7 Cs (E subgamma=0.662 MeV). The timing pulses (50 OMEGA terminated dynode signal) from the PMT base were directly input to a GaGe CompuScope 8012A/PCI sup T sup M (12-bit, 50 MHz dual channel digital oscilloscope card) that resided in a P6-300 MHz personal computer. Individual digitized pulses were processed via a LabVIEW sup T sup M V 4.1 interface to the oscilloscope. The ratio of the charge collected over a short time interval to the total charge collected was used for the single parameter pulse shape spectrum while the total charge collected was used for the single parameter pu...

  11. Mass measurements on neutron-deficient nuclides at SHIPTRAP and commissioning of a cryogenic narrow-band FT-ICR mass spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Ferrer Garcia, R.

    2007-07-01

    The dissertation presented here deals with high-precision Penning trap mass spectrometry on short-lived radionuclides. Owed to the ability of revealing all nucleonic interactions, mass measurements far off the line of {beta}-stability are expected to bring new insight to the current knowledge of nuclear properties and serve to test the predictive power of mass models and formulas. In nuclear astrophysics, atomic masses are fundamental parameters for the understanding of the synthesis of nuclei in the stellar environments. This thesis presents ten mass values of radionuclides around A=90 interspersed in the predicted rp-process pathway. Six of them have been experimentally determined for the first time. The measurements have been carried out at the Penning-trap mass spectrometer SHIPTRAP using the destructive time-of-flight ion-cyclotron-resonance (TOF-ICR) detection technique. Given the limited performance of the TOF-ICR detection when trying to investigate heavy/superheavy species with small production cross sections ({sigma} <1 {mu}b), a new detection system is found to be necessary. Thus, the second part of this thesis deals with the commissioning of a cryogenic double-Penning trap system for the application of a highly-sensitive, narrow-band Fourier-transform ion-cyclotron-resonance (FT-ICR) detection technique. With the non-destructive FT-ICR detection method a single singly-charged trapped ion will provide the required information to determine its mass. First off-line tests of a new detector system based on a channeltron with an attached conversion dynode, of a cryogenic pumping barrier, to guarantee ultra-high vacuum conditions during mass determination, and of the detection electronics for the required single-ion sensitivity are reported. (orig.)

  12. A low background-rate detector for ions in the 5 to 50 keV energy range to be used for radioisotope dating with a small cyclotron

    International Nuclear Information System (INIS)

    Friedman, P.G.

    1986-01-01

    Accelerator mass spectrometry in tandem Van de Graaff accelerators has proven successful for radioisotope dating small samples. We are developing a 20 cm diameter 30 to 40 keV cyclotron dedicated to high-sensitivity radioisotope dating, initially for 14 C. At this energy, range and dE/dx methods of particle identification are impossible. Thus arises the difficult problem of reliably detecting 30 to 40 keV 14 C at 10 -2 counts/sec in the high background environment of the cyclotron, where lower energy ions, electrons, and photons bombard the detector at much higher rates. We have developed and tested an inexpensive, generally useful ion detector that allows dark-count rates below 10 -4 counts/sec and excellent background suppression. With the cyclotron tuned near the 13 CH background peak, to the frequency for 14 C, the detector suppresses the background to 6 x 10 -4 counts/sec. For each 14 C ion the detectors grazing-incidence Al 2 O 3 conversion dynode emits about 20 secondary electrons, which are independently multiplied in separate pores of a microchannel plate. The output signal is proportional to the number of secondary electrons, allowing pulse-height discrimination of background. We have successfully tested the detector with positive 12 C, 23 Na, 39 K, 41 K, 85 Rb, 87 Rb, and 133 Cs at 5 to 40 keV, and with 36 keV negative 12 C and 13 CH. It should detect ions and neutrals of all species, at energies above 5 keV, with good efficiency and excellent background discrimination. Counting efficiency and background discrimination improve with higher ion energy. The detector can be operated at least up to 2 x 10 -7 Torr and be repeatedly exposed to air. The maximum rate is 10/sup 6.4/ ions/sec in pulse counting mode and 10/sup 9.7/ ions/sec in current integrating mode

  13. A double photomultiplier Compton camera and its readout system for mice imaging

    Energy Technology Data Exchange (ETDEWEB)

    Fontana, Cristiano Lino [Physics Department Galileo Galilei, University of Padua, Via Marzolo 8, Padova 35131 (Italy) and INFN Padova, Via Marzolo 8, Padova 35131 (Italy); Atroshchenko, Kostiantyn [Physics Department Galileo Galilei, University of Padua, Via Marzolo 8, Padova 35131 (Italy) and INFN Legnaro, Viale dell' Universita 2, Legnaro PD 35020 (Italy); Baldazzi, Giuseppe [Physics Department, University of Bologna, Viale Berti Pichat 6/2, Bologna 40127, Italy and INFN Bologna, Viale Berti Pichat 6/2, Bologna 40127 (Italy); Bello, Michele [INFN Legnaro, Viale dell' Universita 2, Legnaro PD 35020 (Italy); Uzunov, Nikolay [Department of Natural Sciences, Shumen University, 115 Universitetska str., Shumen 9712, Bulgaria and INFN Legnaro, Viale dell' Universita 2, Legnaro PD 35020 (Italy); Di Domenico, Giovanni [Physics Department, University of Ferrara, Via Saragat 1, Ferrara 44122 (Italy) and INFN Ferrara, Via Saragat 1, Ferrara 44122 (Italy)

    2013-04-19

    We have designed a Compton Camera (CC) to image the bio-distribution of gamma-emitting radiopharmaceuticals in mice. A CC employs the 'electronic collimation', i.e. a technique that traces the gamma-rays instead of selecting them with physical lead or tungsten collimators. To perform such a task, a CC measures the parameters of the Compton interaction that occurs in the device itself. At least two detectors are required: one (tracker), where the primary gamma undergoes a Compton interaction and a second one (calorimeter), in which the scattered gamma is completely absorbed. Eventually the polar angle and hence a 'cone' of possible incident directions are obtained (event with 'incomplete geometry'). Different solutions for the two detectors are proposed in the literature: our design foresees two similar Position Sensitive Photomultipliers (PMT, Hamamatsu H8500). Each PMT has 64 output channels that are reduced to 4 using a charge multiplexed readout system, i.e. a Series Charge Multiplexing net of resistors. Triggering of the system is provided by the coincidence of fast signals extracted at the last dynode of the PMTs. Assets are the low cost and the simplicity of design and operation, having just one type of device; among drawbacks there is a lower resolution with respect to more sophisticated trackers and full 64 channels Readout. This paper does compare our design of our two-Hamamatsu CC to other solutions and shows how the spatial and energy accuracy is suitable for the inspection of radioactivity in mice.

  14. A high dynamic range pulse counting detection system for mass spectrometry.

    Science.gov (United States)

    Collings, Bruce A; Dima, Martian D; Ivosev, Gordana; Zhong, Feng

    2014-01-30

    A high dynamic range pulse counting system has been developed that demonstrates an ability to operate at up to 2e8 counts per second (cps) on a triple quadrupole mass spectrometer. Previous pulse counting detection systems have typically been limited to about 1e7 cps at the upper end of the systems dynamic range. Modifications to the detection electronics and dead time correction algorithm are described in this paper. A high gain transimpedance amplifier is employed that allows a multi-channel electron multiplier to be operated at a significantly lower bias potential than in previous pulse counting systems. The system utilises a high-energy conversion dynode, a multi-channel electron multiplier, a high gain transimpedance amplifier, non-paralysing detection electronics and a modified dead time correction algorithm. Modification of the dead time correction algorithm is necessary due to a characteristic of the pulse counting electronics. A pulse counting detection system with the capability to count at ion arrival rates of up to 2e8 cps is described. This is shown to provide a linear dynamic range of nearly five orders of magnitude for a sample of aprazolam with concentrations ranging from 0.0006970 ng/mL to 3333 ng/mL while monitoring the m/z 309.1 → m/z 205.2 transition. This represents an upward extension of the detector's linear dynamic range of about two orders of magnitude. A new high dynamic range pulse counting system has been developed demonstrating the ability to operate at up to 2e8 cps on a triple quadrupole mass spectrometer. This provides an upward extension of the detector's linear dynamic range by about two orders of magnitude over previous pulse counting systems. Copyright © 2013 John Wiley & Sons, Ltd.

  15. Electron emission from materials at low excitation energies

    International Nuclear Information System (INIS)

    Urma, N.; Kijek, M.; Millar, J.J.

    1996-01-01

    Full text: An experimental system has been designed and developed with the purpose of measuring the total electron emission yield from materials at low energy excitation. In the first instance the reliability of the system was checked by measuring the total electron emission yield for a well defined surface (aluminium 99.45%). The obtained data was in the expected range given by the literature, and consequently the system will be used further for measuring the total electron yield for a range of materials with interest in the instrumentation industry. We intend to measure the total electron emission yield under electron bombardment as a function of incident electron energy up to 1200 eV, angle of incidence, state of the surface and environment to which the surface has been exposed. Dependence of emission on total electron irradiated dose is also of interest. For many practical application of the 'Secondary Electron Emission', the total electron yield is desired to be as large as possible. The above phenomenon has practical applicability in electron multiplier tube and Scanning electron microscopy - when by means of the variation of the yield of the emitted electrons one may produce visible images of small sample areas. The electron multiplier tube, is a device which utilises the above effect to detect and amplify both single particles and low currents streams of charged particles. The majority of electron tubes use electrons with low energy, hundreds of eV. Not a lot has been published in the literature about this regime and also about the emission when the impinging electrons have small energy, up to 1 KeV. The information obtained from the experimental measurements concerning the total electron emission yield is used to asses the investigated materials as a potential electron emitting surfaces or dynodes in an electron multiplier tube

  16. The advantages of orthogonal acceleration in ICP time-of-flight mass spectrometry

    International Nuclear Information System (INIS)

    Gaal, Andrew

    2004-01-01

    The OptiMass 8000 incorporates an orthogonal acceleration time-of-flight mass spectrometer. A general schematic of the instrument is given. The continuous ion beam is chopped by an orthogonal accelerator. A push out pulse supply is coupled to the accelerator for providing repetitive push-out voltages at a frequency of 30 kHz. The ion packets that are sliced out of the beam then travel within the field free space towards the SMARTGATE ion blanker. Orthogonal accelerator parameters are set to enable temporal-spatial focusing at the SMARTGATE ion blanker, so that iso-mass ion packets are resolved in time. Any ion packets of unwanted specie are ejected from the direction of travel by supplying pulsed voltages onto the deflection plates of the SMARTGATE. The ions to be measured are let through SMARTGATE and travel further down the field free space, to enter the ion reflectron. The ion reflectron increases the resolution of the mass spectrometer by means of temporal-energy focussing. After reflection, the ions travel within the field free space towards the discrete-dynode detector. In comparison to other acceleration geometries used in elemental time-of-flight mass spectrometry the OptiMass 8000 orthogonal acceleration geometry ultimately leads to superior resolution. As the energy spread is about 3 orders of magnitude lower in the time-of-flight direction for an oaTOFMS in comparison to an on-axis system, aberration acquired in the initial stages of acceleration are much lower. As a result the orthogonal acceleration scheme provides superior resolution at the first spatial focus point and the detector. The orthogonal acceleration time-of-flight analyzer of the OptiMass 8000 is able to provide resolution of at least 1800 at mass 238. (author)

  17. Limitation of secondary electron multiplier non-linearity on accurate U-Th isotopic determination by MC-ICP-MS

    Science.gov (United States)

    Shen, C.; Wu, C.; Gallet, S.; Cheng, H.; Edwards, R.; Hsieh, Y.; Lin, K.

    2008-12-01

    Contemporary multicollector-inductively coupled plasma mass spectrometry (MC-ICP-MS) with discrete dynode secondary electron multipliers (SEMs) can offer U-Th isotopic determinations with subpermil-permil- level precision in femtogram quantities. However, accurate isotopic measurement requires fully understanding SEM mass and intensity biases. In additional to dead-time effect, Richter et al (2001, Int. J. Mass Spectrom., 206, 105-127) reported a nonlinearity on SEMs produced by ETP and MasCom for count rates > 20 thousand counts per second (cps). We evaluated the possible biases for ion beams of 500- 1,600,000 cps on a latest MasCom SEM, SEV TE-Z/17, with more effective ion optical acceptance area (>50%) and better peak shape than previous models, used in a MC-ICP-MS, Thermo Fisher NEPTUNE. With the retarding potential quadruple lens (RPQ) turned off, ion beam intensity can be biased by only dead- time effect, which can be precisely corrected online or offline. With the RPQ on, two additional biases, an exponential-like increase of ion beam intensity from 100-100,000 s cps and an apparent dead-time effect (-2 to 2 ns) at high count rates, are observed. They are likely caused by the slightly defocused ions with a wide kinetic energy spread of ~5 eV, 10 times worse than that with thermal source, passing through the RPQ lens to the SEM, which is installed behind the focal plane. Fortunately, the two biases, which are stable during the daily measurements with the same settings of inlet system, source lenses, zoom optics, and RPQ, can be corrected effectively offline to earn accurate U-Th isotopic measurement.

  18. Mass cytometry: technique for real time single cell multitarget immunoassay based on inductively coupled plasma time-of-flight mass spectrometry.

    Science.gov (United States)

    Bandura, Dmitry R; Baranov, Vladimir I; Ornatsky, Olga I; Antonov, Alexei; Kinach, Robert; Lou, Xudong; Pavlov, Serguei; Vorobiev, Sergey; Dick, John E; Tanner, Scott D

    2009-08-15

    A novel instrument for real time analysis of individual biological cells or other microparticles is described. The instrument is based on inductively coupled plasma time-of-flight mass spectrometry and comprises a three-aperture plasma-vacuum interface, a dc quadrupole turning optics for decoupling ions from neutral components, an rf quadrupole ion guide discriminating against low-mass dominant plasma ions, a point-to-parallel focusing dc quadrupole doublet, an orthogonal acceleration reflectron analyzer, a discrete dynode fast ion detector, and an 8-bit 1 GHz digitizer. A high spectrum generation frequency of 76.8 kHz provides capability for collecting multiple spectra from each particle-induced transient ion cloud, typically of 200-300 micros duration. It is shown that the transients can be resolved and characterized individually at a peak frequency of 1100 particles per second. Design considerations and optimization data are presented. The figures of merit of the instrument are measured under standard inductively coupled plasma (ICP) operating conditions ( 900 for m/z = 159, the sensitivity with a standard sample introduction system of >1.4 x 10(8) ion counts per second per mg L(-1) of Tb and an abundance sensitivity of (6 x 10(-4))-(1.4 x 10(-3)) (trailing and leading masses, respectively) are shown. The mass range (m/z = 125-215) and abundance sensitivity are sufficient for elemental immunoassay with up to 60 distinct available elemental tags. When 500) can be used, which provides >2.4 x 10(8) cps per mg L(-1) of Tb, at (1.5 x 10(-3))-(5.0 x 10(-3)) abundance sensitivity. The real-time simultaneous detection of multiple isotopes from individual 1.8 microm polystyrene beads labeled with lanthanides is shown. A real time single cell 20 antigen expression assay of model cell lines and leukemia patient samples immuno-labeled with lanthanide-tagged antibodies is presented.

  19. Spectrometric performances of high quantum efficiency multi and single anode PMTs coupled to LaBr3(Ce) crystal

    Energy Technology Data Exchange (ETDEWEB)

    Cinti, Maria Nerina, E-mail: marianerina.cinti@uniroma1.it [Department of Molecular Medicine, Sapienza University of Rome, Rome 00161 (Italy); INFN Rome 1 Section, Rome (Italy); Pani, Roberto; Pellegrini, Rosanna [Department of Molecular Medicine, Sapienza University of Rome, Rome 00161 (Italy); INFN Rome 1 Section, Rome (Italy); Bennati, Paolo [Department of Molecular Medicine, Sapienza University of Rome, Rome 00161 (Italy); Orlandi, Chiara [Medical Physics Post Graduate School, Sapienza University of Rome, Rome 00161 (Italy); Fabbri, Andrea [Department of Physics, Roma Tre University, Rome (Italy); INFN Rome 3 Section, Rome (Italy); Ridolfi, Stefano; Scafè, Raffaele [Department of Molecular Medicine, Sapienza University of Rome, Rome 00161 (Italy)

    2013-10-01

    High quantum efficiency semiconductor photodetectors have recently drawn the attention of the scientific community for their potential in the realization of a new class of scintillation imagers with very high energy and spatial resolution performance. However, this goal does not seem within easy reach, due to various technological issues such as, for example, the difficulty to scale the characteristics of a single detector to an imager with suitable dimensions. Lately a definite technical improvement in increasing quantum efficiency up to 42% for position sensitive photomultipliers was achieved. The aim of this work is thus to test this new technological progress and to study the possible implications in imaging applications. Four Hamamatsu PMTs were tested: two multi anode photomultipliers, one with a bialkali (27% quantum efficiency) and the other one with a super-bialkali photocathode (38% quantum efficiency), and two 1×1 in. PMTs, both equipped with an ultra bialkali photocathode (42% quantum efficiency). In particular one of the ultra bialkali PMT has also an increased efficiency of first dynode charge collection. The results were compared with the ones obtained with a reference PMT (Hamamatsu R6231), mainly used in spectroscopy. The PMTs were coupled to LaBr3(Ce), NaI(Tl) and LSO(Ce) continuous scintillation crystals. The tests were done using two independent electronic chains: one dedicated for spectroscopic application and a second one, using a multi wire 64 channel readout, for imaging applications. The super-bialkali MA-PMTs have shown high energy resolution, both with spectroscopic and imaging setup, highlighting the appropriateness of these devices for the development of imaging devices with high spectroscopic performance. -- Highlights: • A study of energy resolution results coming from position sensitive photomultipliers are proposed. • The study is also extended on mono- anode photomultiplier. • The selected scintillation crystal is LeBr3(Ce

  20. Gamma–neutron imaging system utilizing pulse shape discrimination with CLYC

    International Nuclear Information System (INIS)

    Whitney, Chad M.; Soundara-Pandian, Lakshmi; Johnson, Erik B.; Vogel, Sam; Vinci, Bob; Squillante, Michael; Glodo, Jarek; Christian, James F.

    2015-01-01

    Recently, RMD has investigated the use of CLYC (Cs 2 LiYCl 6 :Ce), a new and emerging scintillation material, in a gamma–neutron coded aperture imaging system based on RMD's commercial RadCam TM instrument. CLYC offers efficient thermal neutron detection, fast neutron detection capabilities, excellent pulse shape discrimination (PSD), and gamma-ray energy resolution as good as 4% at 662 keV. PSD improves the isolation of higher energy gammas from thermal neutron interactions (>3 MeV electron equivalent peak), compared to conventional pulse height techniques. The scintillation emission time in CLYC provides the basis for PSD; where neutron interactions result in a slower emission rise and decay components while gamma interactions result in a faster emission components. By creating a population plot based on the ratio of the decay tail compared to the total integral amplitude (PSD ratio), discrimination of gammas, thermal neutrons, and fast neutrons is possible. Previously, we characterized the CLYC-based RadCam system for imaging gammas and neutrons using a layered W-Cd coded aperture mask and employing only pulse height discrimination. In this paper, we present the latest results which investigate gamma-neutron imaging capabilities using PSD. An FPGA system is used to acquire the CLYC–PSPMT last dynode signals, determine a PSD ratio for each event, and compare it to a calibrated PSD cutoff. Each event is assigned either a gamma (low) or neutron (high) flag signal which is then correlated with the imaging information for each event. - Highlights: • The latest results are presented for our CLYC RadCam-2 system which investigate gamma–neutron imaging using pulse shape discrimination. • CLYC RadCam-2 system successfully discriminates gammas, thermal neutrons, and fast neutrons by employing a fully integrated, FPGA-based PSD system. • Imaging of our 252 Cf source was possible using both pulse height and pulse shape discrimination with CLYC. • Imaging

  1. Study of a photomultiplier for the measurement of low light flows by photon counting; Etude d'un photomultiplicateur en vue de la mesure des faibles flux lumineux par comptage de photons

    Energy Technology Data Exchange (ETDEWEB)

    Haye, Kleber

    1964-03-20

    After a recall of the history of the discovery and use of the photoemission effect, a presentation of the main characteristics of photomultipliers, a discussion of performance and weaknesses of electron multiplier-based cells, this research thesis addresses the study of low light flows. The author tried to determine whether it was possible, at ambient temperature, to reduce the influence of the thermoelectric effect. In order to do so, he made a detailed study of the amplitude spectrum of pulses of photoelectric origin. In order to analyse the influence of temperature of photomultiplier characteristics, he studied, with respect to temperature, the variation of the counting rate corresponding to darkness, the variation of pulse amplitude spectrum, and relative variations of the quantum efficiency for various wavelengths. In parallel with the study by counting, a study has been performed by using the well known mean current measurement [French] Si l'on veut etudier de faibles flux lumineux, c'est surtout l'effet thermoelectronique qui limite a temperature ambiante le domaine possible des mesures. Les electrons qui arrivent en effet a quitter la photocathode ou les dynodes donnent naissance a des groupes supplementaires d'electrons venant s'ajouter a ceux causes par effet photoelectrique. En utilisant une methode de mesure par comptage des groupes d'electrons, nous nous sommes attaches a determiner s'il etait possible a temperature ordinaire de reduire 1'influence de l'effet thermoelectronique. Pour cela, nous avons fait une etude detaillee du spectre d'amplitude des impulsions d'origine photoelectrique. Toutefois, la solution la plus efficace pour combattre l'effet thermoelectronique etant le refroidissement, nous avons essaye d'analyser l'influence de la temperature sur les caracteristiques du photomultiplicateur. Nous avons ainsi etudie en fonction de la temperature la variation du taux de comptage correspondant a l'obscurite, la variation du spectre d

  2. TH-CD-207B-06: Swank Factor of Segmented Scintillators in Multi-Slice CT Detectors: Pulse Height Spectra and Light Escape

    Energy Technology Data Exchange (ETDEWEB)

    Howansky, A; Peng, B; Lubinsky, A; Zhao, W [Stony Brook University, Stony Brook, NY (United States)

    2016-06-15

    Purpose: Pulse height spectra (PHS) have been used to determine the Swank factor of a scintillator by measuring fluctuations in its light output per x-ray interaction. The Swank factor and x-ray quantum efficiency of a scintillator define the upper limit to its imaging performance, i.e. DQE(0). The Swank factor below the K-edge is dominated by optical properties, i.e. variations in light escape efficiency from different depths of interaction, denoted e(z). These variations can be optimized to improve tradeoffs in x-ray absorption, light yield, and spatial resolution. This work develops a quantitative model for interpreting measured PHS, and estimating e(z) on an absolute scale. The method is used to investigate segmented ceramic GOS scintillators used in multi-slice CT detectors. Methods: PHS of a ceramic GOS plate (1 mm thickness) and segmented GOS array (1.4 mm thick) were measured at 46 keV. Signal and noise propagation through x-ray conversion gain, light escape, detection by a photomultiplier tube and dynode amplification were modeled using a cascade of stochastic gain stages. PHS were calculated with these expressions and compared to measurements. Light escape parameters were varied until modeled PHS agreed with measurements. The resulting estimates of e(z) were used to calculate PHS without measurement noise to determine the inherent Swank factor. Results: The variation in e(z) was 67.2–89.7% in the plate and 40.2–70.8% in the segmented sample, corresponding to conversion gains of 28.6–38.1 keV{sup −1} and 17.1–30.1 keV{sup −1}, respectively. The inherent Swank factors of the plate and segmented sample were 0.99 and 0.95, respectively. Conclusion: The high light escape efficiency in the ceramic GOS samples yields high Swank factors and DQE(0) in CT applications. The PHS model allows the intrinsic optical properties of scintillators to be deduced from PHS measurements, thus it provides new insights for evaluating the imaging performance of

  3. Readout Electronics for BGO Calorimeter of DAMPE: Status during the First Half-year after Launching

    Science.gov (United States)

    Ma, Siyuan; Feng, Changqing; Zhang, Deliang; Wang, Qi

    2016-07-01

    The DAMPE (DArk Matter Particle Explorer) is a scientic satellite which was successfully launched into a 500 Km sun-synchronous orbit, on December 17th, 2015, from the Jiuquan Satellite Launch Center of China. The major scientific objective of DAMPE mission is indirect searching for dark matter by observing high energy primary cosmic rays, especially positrons/electrons and gamma rays with an energy range from 5 GeV to 10 TeV. The BGO (Bismuth Germanate Oxide) calorimeter, which is a critical sub-detector of DAMPE payload, was developed for measuring the energy of cosmic particles, distinguishing positrons/electrons and gamma rays from hadron background, and providing trigger information. It is composed of 308 BGO crystal logs, with the size of 2.5cm*2.5cm*60cm for each log to form a total absorption electromagnetic calorimeter. All the BGO logs are stacked in 14 layers, with each layer consisting of 22 BGO crystal logs and each log is viewed by two Hamamatsu R5610A PMTs (photomultiplier tubes), from both sides respectively. Each PMT incorporates a three dynode pick off to achieve a large dynamic range, which results in 616 PMTs and 1848 signal channels. The main function of readout electronics system, which consists of 16 FEE(Front End Electronics) modules, is to precisely measure the charge of PMT signals and providing "hit" signals. The hit signals are sent to the trigger module of PDPU (Payload Data Process Unit) to generate triggers for the payload. The calibration of the BGO calorimeter is composed of pedestal testing and electronic linear scale, which are executed frequently in the space after launching. The data of the testing is transmitted to ground station in the form of scientific data. The monitor status consists of temperature, current and status words of the FEE, which are measured and recorded every 16 seconds and packed in the engineering data, then transmitted to ground station. The status of the BGO calorimeter can be evaluated by the calibration

  4. Electronic methods for discriminating scintillation shapes; Methodes electroniques de discrimination des formes des impulsions issues de scintillateurs; Ehlektronnye metody diskriminatsii form stsintillyatsii; Metodos electronicos de discriminacion de forma de impulsos de centelleo

    Energy Technology Data Exchange (ETDEWEB)

    Forte, M; Konsta, A; Maranzana, C [European Atomic Energy Community, CCR, ISPRA (Italy)

    1962-04-15

    As reported previously, the scintillation pulse shape, which is characteristic of the excitating particle type (electron, proton, alpha, etc.), can be converted into a pulse-height independent parameter. This displays, by means of a multichannel analyser, the composition of a mixed particle beam which excites the scintillator. This method was successful with several scintillators, both of the organic and the inorganic type. Details are given of the electronic techniques used for converting the pulse shapes. For the simpler case of discrimination between only two classes of pulses (e.g. neutron-gamma discrimination) the use of passive networks has also been considered possible for further improvements and simplifications. A few networks were tried, the main results being that, in the presence of gamma background, the discrimination of recoil protons in liquid scintillators was extended to small pulses of a few decades of photoelectrons and the discrimination of neutron-capture fragments in boronloaded liquids was obtained. Some of these networks operated with pulses of the same polarity, from two of the last dynode, or even with the output from a single electrode. This may be useful when it is convenient to use the anode independently, e. g. for operating fast time circuits. (author) [French] On sait que la forme des impulsions delivrees par un detecteur a scintillations, qui est fonction du type de particule excitatrice (electron, proton, particule alpha, etc.), peut etre convertie en un parametre d'amplitude d'impulsion independant. Cette propriete permet de determiner, a l'aide d'un selecteur multicanaux, la composition d'un faisceau de particules mixte qui frappe le scintillateur. Cette methode a ete utilisee avec succes dans le cas de plusieurs scintillateurs, tant organiques qu'inorganiques. Les auteurs donnent des precisions sur les procedes electroniques employes pour convertir la forme de l'impulsion. Dans le cas le plus simple, celui ou la discrimination

  5. Study on Radiation Condition in DAMPE Orbit by Analyzing the Engineering Data of BGO Calorimeter

    Science.gov (United States)

    Feng, Changqing; Liu, Shubin; Zhang, Yunlong; Ma, Siyuan

    2016-07-01

    The DAMPE (DArk Matter Particle Explorer) is a scientific satellite which was successfully launched into a 500 Km sun-synchronous orbit, on December 17th, 2015, from the Jiuquan Satellite Launch Center of China. The major scientific objectives of the DAMPE mission are primary cosmic ray, gamma ray astronomy and dark matter particles, by observing high energy primary cosmic rays, especially positrons/electrons and gamma rays with an energy range from 5 GeV to 10 TeV. The BGO calorimeter is a critical sub-detector of DAMPE payload, for measuring the energy of cosmic particles, distinguishing positrons/electrons and gamma rays from hadron background, and providing trigger information. It utilizes 308 BGO (Bismuth Germanate Oxide) crystal logs with the size of 2.5cm*2.5cm*60cm for each log, to form a total absorption electromagnetic calorimeter. All the BGO logs are stacked in 14 layers, with each layer consisting of 22 BGO crystal logs and each log is viewed by two Hamamatsu R5610A PMTs (photomultiplier tubes), from both sides respectively. In order to achieve a large dynamic range, each PMT base incorporates a three dynode (2, 5, 8) pick off, which results in 616 PMTs and 1848 signal channels. The readout electronics system, which consists of 16 FEE (Front End Electronics) modules, was developed. Its main functions are based on the Flash-based FPGA (Field Programmable Gate Array) chip and low power, 32-channel VA160 and VATA160 ASICs (Application Specific Integrated Circuits) for precisely measuring the charge of PMT signals and providing "hit" signals as well. The hit signals are sent to the trigger module of PDPU (Payload Data Process Unit) and the hit rates of each layer is real-timely recorded by counters and packed into the engineering data, which directly reflect the flux of particles which fly into or pass through the detectors. In order to mitigate the SEU (Single Event Upset) effect in radioactive space environment, certain protecting methods, such as TMR

  6. A Low-Background Liquid-Scintlllation Counter for the Assay of Low-Specific Activity Tritiated Water; Compteur a scintillations a liquides, a faible mouvement propre, pour le dosage d'eau tritiee en faible activite specifique; ZHidkostnyj stsintillyatsionnyi schetchik s nizkim fonom dlya analiza nasyshchennoj tritiem vody s nizkoj udel'noj aktivnost'yu; Contador de centelleador liquido de reducida actividad de fondo para el analisis de agua pritiada de baja actividad especifica

    Energy Technology Data Exchange (ETDEWEB)

    Boyce, I S; Cameron, J F [Wantage Research Laboratory, Wantage (United Kingdom)

    1962-01-15

    In liquid-scintillation counting of tritiated water single photomultiplier counters and coincidence systems offer comparable sensitivities. To investigate low level counting a coincidence system was selected to avoid Uncertainties in the background due to single photon events arising from phosphorescence and chemiluminescenc e in the solution. With this system the background was found to be due largely to light originating in the photomultiplier photocathode. Using two photomultipliers with ''Pyrex'' photocathodes in contact in an 8 in thick iron shield experiments were conducted to determine the relative importance of the following possible courses of background : (a) Ionization and excitation of residual gas and of the semi-conductor dynode surfaces, particularly in regions where the current density is greatest. (b) Sparking, electroluminescence and field emission. (c) Positive ion feedback to the photocathode causing secondary electron emission. (d) Operation of the photocathode window itself as a phosphor for cosmic radiation, K{sup 40} beta particles or radiation from uranium daughter products. In particular it was found that contribution (c) was significantly lower than was previously supposed. Methods of minimizing these effects, including the use of quartz photocathodes, and special photomultipliers were investigated. In the finished design of counter the minimum detectable specific activity with a counting time of 30 min. is 6x10{sup 7} {mu}c/ml. (author) [French] Dans le dosage de l'eau tritiee au moyen d'un compteur a scintillations a liquides, les compteurs a photomultiplicateur unique et les ensembles a coincidences presentent une sensibilite du meme ordre. Pour faire des recherches sur la mesure des faibles activites, les auteurs ont choisi un dispositif monte en coincidence, afin d'eviter les incertitudes dans le mouvement propre causees par l'apparation de photons isoles, dus a la phosphorescence et a la chimioluminescenc e de la solution. Dans ce