Showing papers on "Photomultiplier published in 2013"

Lexsyg — A new system for luminescence research

Abstract: The newly developed lexsyg system by Freiberg Instruments is a versatile luminescence reader, suited for research on the luminescence of materials, fundamental research in luminescence dating, but also for routine mass measurements in retrospective dosimetry as well as in dating application. The 80 sample storage wheel is disconnected from the measurement chamber and therefore crosstalk of optical stimulation is absent and cross-irradiation is negligible from the α- and β-sources, which are providing very uniform irradiations, with the latter especially designed for radiofluores-cence (RF) measurement. Optical excitation sources and filter wheels to vary detection wavelengths can be programmed to change at almost any time within measurement sequences, including the auto-mated change of an optional wheel holding up to four different detectors. Thermoluminescence meas-urements and preheating are possible with a versatile heater, which can be programmed for linear or non-linear heating or cooling, as well as holding a temperature constant. Rates as well as durations can be varied, together with individual ramping, staging and cooling for an almost unlimited number of steps. Violet- and IR-lasers, green and blue LED-arrays can be operated in continuous (CW) or modulated mode (linear/non-linear), and optionally for pulsed as well as time resolved luminescence detection. Six arrays of power LEDs allow the simulation of different bleaching regimes (‘solar simu-lator’), while luminescence detection can be achieved by a variety of photomultiplier tubes and by CCD cameras for spatially resolved measurements and luminescence spectra.

Improvement of γ-ray energy resolution of LaBr3:Ce3+ scintillation detectors by Sr2+ and Ca2+ co-doping

Abstract: Commercially available LaBr3:5% Ce3+ scintillators show with photomultiplier tube readout about 2.7% energy resolution for the detection of 662 keV γ-rays. Here we will show that by co-doping LaBr3:Ce3+ with Sr2+ or Ca2+ the resolution is improved to 2.0%. Such an improvement is attributed to a strong reduction of the scintillation light losses that are due to radiationless recombination of free electrons and holes during the earliest stages (1–10 ps) inside the high free charge carrier density parts of the ionization track.

Neutron light output response and resolution functions in EJ-309 liquid scintillation detectors

Abstract: Neutron light output response functions and detector resolution functions were measured at Ohio University's tandem Van de Graaff generator for three cylindrical EJ-309 liquid scintillator cells, having dimensions 12.7 ( ∅ )-by-12.7, 7.6-by-7.6, and 7.6-by-5.1 cm. A 7.44 MeV deuteron beam was used on an 27Al target generating a continuous spectrum over the energy range from a few hundred keV to over 10 MeV. The light output response functions are determined using an exponential fit. Detector resolution functions are obtained for the 12.7-by-12.7 and 7.6-by-7.6 cm detectors. It is demonstrated that the dependence on detector size is important for the light output response functions, but not to the same extent for the resolution function, even when photomultiplier tubes, detector material, and other detector characteristics are carefully matched.

Composite gamma-neutron detection system

Abstract: The present invention provides a gamma-neutron detector based on mixtures of thermal neutron absorbers that produce heavy-particle emission following thermal capture. In one configuration, B-10 based detector is used in a parallel electrode plate geometry that integrates neutron moderating sheets, such as polyethylene, on the back of the electrode plates to thermalize the neutrons and then detect them with high efficiency. The moderator can also be replaced with plastic scintillator sheets viewed with a large area photomultiplier tube to detect gamma-rays as well. The detector can be used in several scanning configurations including portal, drive-through, drive-by, handheld and backpack, etc.

Characterization of the First FBK High-Density Cell Silicon Photomultiplier Technology

Abstract: In this paper, we present the results of the characterization of the first high-density (HD) cell silicon photomultipliers produced at FBK. The most advanced prototype manufactured with this technology has a cell size of 15 × 15 μm2 featuring a nominal fill factor of 48%. To reach this high area coverage, we developed a new border structure to confine the high electric-field region of each single-photon avalanche diode. The measured detection efficiency approaches 30% in the green part of the light spectrum and it is above 20% from 400 to 650 nm. At these efficiency values, the correlated noise is very low, giving an excess charge factor below 1.1. We coupled a 2 × 2 × 10- mm3 LYSO scintillator crystal to a 2.2 × 2.2- mm2 silicon photomultiplier, obtaining very promising results for PET application: energy resolution of less than 11% full-width at half maximum (FWHM) with negligible loss of linearity and coincidence resolving time of 200-ps FWHM at 20°C.

Fast timing study of a CeBr 3 crystal: Time resolution below 120 ps at 60 Co energies

Abstract: We report on the time response of a novel inorganic scintillator, CeBr3. The measurements were performed using a cylindrical crystal of 1-in. in height and 1-in. in diameter at 22Na and 60Co photon energies. The time response was measured against a fast reference BaF2 detector. Hamamatsu R9779 and Photonis XP20D0 fast photomultipliers (PMTs) were used. The PMT bias voltages and Constant Fraction Discriminator settings were optimized with respect to the timing resolution. The Full Width at Half Maximum (FWHM) time resolution for an individual CeBr3 crystal coupled to Hamamatsu PMT is found here to be as low as 119 ps at 60Co energies, which is comparable to the resolution of 107 ps reported for LaBr3(Ce). For 511 keV photons the measured FWHM time resolution for CeBr3 coupled to the Hamamatsu PMT is 164 ps.

Performance of the Hamamatsu R11410 photomultiplier tube in cryogenic xenon environments

Abstract: The Hamamatsu R11410 photomultiplier, a tube of 3'' diameter and with a very low intrinsic radioactivity, is an interesting light sensor candidate for future experiments using liquid xenon (LXe) as target for direct dark matter searches. We have performed several experiments with the R11410 with the goal of testing its performance in environments similar to a dark matter detector setup. In particular, we examined its long-term behavior and stability in LXe and its response in various electric field configurations.

Performance of the Hamamatsu R11410 Photomultiplier Tube in cryogenic Xenon Environments

Abstract: The Hamamatsu R11410 photomultiplier, a tube of 3" diameter and with a very low intrinsic radioactivity, is an interesting light sensor candidate for future experiments using liquid xenon (LXe) as target for direct dark matter searches. We have performed several experiments with the R11410 with the goal of testing its performance in environments similar to a dark matter detector setup. In particular, we examined its long-term behavior and stability in LXe and its response in various electric field configurations.

An 8×16-pixel 92kSPAD time-resolved sensor with on-pixel 64ps 12b TDC and 100MS/s real-time energy histogramming in 0.13µm CIS technology for PET/MRI applications

Abstract: Positron-Emission Tomography (PET) is a nuclear imaging technique that provides functional 3-dimensional images of the body, finding its key applications in clinical oncology and brain-function analyses. The typical PET scanner is composed of a ring of scintillator crystals that absorb gamma rays and emit photons as a result, coupled to photon-sensing devices. The photons hit the sensors with a certain spread in space and time, depending on the material and geometry of the crystals. The sensors must then estimate the energy, the time of arrival (ToA), and the axial position of incoming gamma rays. Most commercially available scanners use photomultiplier tubes (PMTs), which are sensitive to magnetic fields, as the sensing element, making the integration of these systems with Magnetic-Resonance Imaging (MRI) impossible. A significant amount of research has focused on replacing PMTs with solid-state detectors, such as Silicon photomultipliers (SiPMs) [1], which can be integrated with MRI while maintaining the high-sensitivity of PMTs.

New Developments of Near-UV SiPMs at FBK

Abstract: A thorough characterization of a novel silicon photomultiplier technology for near-ultraviolet (near-UV) light detection, called NUV-SiPM, is presented. It features a peak detection efficiency of more than 30% in the region between 380 and 400 nm, mainly limited by the fill factor. An accurate electric field engineering allows to have excellent noise properties, with a dark count rate of less than 200 kHz/mm2 at maximum efficiency and 20°C. In addition, a breakdown voltage uniformity better than 100 mV at the wafer level and a temperature dependence of 25 mV/°C were obtained. We coupled a 4 × 4 mm2 device to a 3 × 3 × 5 mm3 LYSO scintillator obtaining an energy resolution of 10% FWHM with 511-keV gamma ray irradiation and a coincidence resolving time between two identical detectors of 210-ps FWHM. A detailed description of these results is presented in the paper.

Picosecond resolution on relativistic heavy ions' time-of-flight measurement

Abstract: We developed a time-of-flight measurement system for relativistic heavy ions with a requested resolution of 40 ps Full Width Half Maximum. Such a resolution is mandatory to assign the correct mass number to every fission fragment, identified using the B ρ - ToF - Δ E method with the recoil spectrometer designed for the SOFIA experiment—which hold very recently at GSI. To achieve such a performance, fast plastic scintillators read-out by dedicated photomultiplier tubes were chosen among other possible options. We have led several test-measurements from 2009 to 2011, in order to investigate: the effect of the addition of a quenching molecule in the scintillator's matrix, the influence of the detector's size and the impact of the photomultiplier tube. The contribution of the dedicated electronics is also characterized. Time-of-flight measurements were performed realized with electron pulses and relativistic heavy ions, respectively provided by the LASER driven electron–accelerator (ELSA) at CEA–DAM Ile-de-France and by the SIS18/FRS facility at GSI. The reported results exhibit a time resolution better than 20 ps Full Width Half Maximum reached with the last prototype at GSI with an Uranium beam. These results confirm that the SOFIA experiment should enable the measurement of the relativistic fission fragments' time-of-flight with the requested resolution.

Hybrid photomultiplier tube and photodiode parallel detection array for wideband optical spectroscopy of the breast guided by magnetic resonance imaging

Abstract: A new optical parallel detection system of hybrid frequency and continuous-wave domains was developed to improve the data quality and accuracy in recovery of all breast optical properties. This new system was deployed in a previously existing system for magnetic resonance imaging (MRI)-guided spectroscopy, and allows incorporation of additional near-infrared wavelengths beyond 850 nm, with interlaced channels of photomultiplier tubes (PMTs) and silicon photodiodes (PDs). The acquisition time for obtaining frequency-domain data at six wavelengths (660, 735, 785, 808, 826, and 849 nm) and continuous-wave data at three wavelengths (903, 912, and 948 nm) is 12 min. The dynamic ranges of the detected signal are 105 and 106 for PMT and PD detectors, respectively. Compared to the previous detection system, the SNR ratio of frequency-domain detection was improved by nearly 103 through the addition of an RF amplifier and the utilization of programmable gain. The current system is being utilized in a clinical trial imaging suspected breast cancer tumors as detected by contrast MRI scans.

Energy resolution of small scintillation detectors with SiPM light readout

Abstract: The development of silicon photomultipliers (SiPMs) with a large number of APD cells and improved linearity of the pulse height response prompted interest in their application to gamma spectrometry with scintillators. Hamamatsu MPPC sensors equipped with 3600 and 14400 APD cells were chosen in our study because of their well pronounced single photoelectron spectra, which allowed us to precisely measure the photoelectron numbers (PHE) or fired APD cells and then to discuss, in a quantitative manner, the obtainable energy resolution. The studied detectors were first characterized in direct detection of laser light pulses and then in gamma spectroscopy with LFS and CsI:Tl crystals. In the study with the laser light pulses the linearity of the MPPC response versus a light pulse intensity monitored with PMT was measured. Two different methods were used for an evaluation of the MPPC response expressed in the number of photoelectrons (PHE) generated by light illumination. The direct method (PHEdir), based on the comparison of the light peak position to that of the single photoelectron peak, determined the upper limit of the PHE. The lower limit of the PHE was derived from an analysis of the measured pulse height resolution under the assumption of Poisson statistics and MPPC excess noise factor (ENF) of 1. Furthermore, the ENF of the MPPC is discussed with respect to the contributions of device dead time, optical cross-talk and after-pulses to the results obtained. In the scintillation tests, measurements of energy resolution and non-proportionality of the light yield were performed with LFS and CsI:Tl crystals, and both types of 3 × 3 mm MPPC detectors were used for light readout. The results are discussed in a quantitative manner based on the measured PHE.

Fast Timing Silicon Photomultipliers for Scintillation Detectors

Abstract: A new silicon photomultiplier is fabricated for fast timing applications by SensL Technologies Ltd. This new family of silicon photomultiplier, herein referred to as fast SPM devices, is fabricated with a third terminal that has a low output capacitance to improve timing performance. Two fast SPMs (an N-on-P type and a prototype P-on-N type) are assessed for energy and timing performances in scintillation detectors. When coupled with L(Y)SO:Ce crystals, the optimal energy resolutions for the 511 keV photon peak are 13.7% and 13.1%, whereas coincidence resolving times (CRTs) of 184±5 and 157±3 ps are attained with 2 × 2 × 3 mm3 crystals for the N-on-P and P-on-N devices, respectively. For longer crystals (3 × 3 × 20 mm3) , more relevant for positron emission tomography, the CRTs are 298±9 and 234±6 ps for the two SPM types, respectively, a significant improvement from standard SPM devices.

Testing of cryogenic photomultiplier tubes for the MicroBooNE experiment

Abstract: The MicroBooNE detector, to be located on axis in the Booster Neutrino Beamline (BNB) at the Fermi National Accelerator Laboratory (Fermilab), consists of two main components: a large liquid argon time projection chamber (LArTPC), and a light collection system. Thirty-two 8-inch diameter Hamamatsu R5912-02mod cryogenic photomultiplier tubes (PMTs) will detect the scintillation light generated in the liquid argon (LAr). This article first describes the MicroBooNE PMT performance test procedures, including how the light collection system functions in the detector, and the design of the PMT base. The design of the cryogenic test stand is then discussed, and finally the results of the cryogenic tests are reported.

Photoemission characteristics of (Cs, O) activation exponential-doping Ga0.37Al0.63As photocathodes

Abstract: Based on the studies of the GaAs photocathode, the surface model of the Ga037Al063As photocathode is investigated and the energy distributions of electrons reaching the surface charge region, reaching the surface and emitting into vacuum are calculated The (Cs, O) adsorption and photoemission characteristics of the Ga037Al063As photocathode are studied according to the experiments We use the quantum efficiency formula to fit the experimental curve, and obtain the performance parameters of the photocathode and the surface barrier parameters The results show that the surface barrier of the Ga037Al063As photocathode is similar to that of the GaAs photocathode The prepared reflection-mode Ga037Al063As photocathode responds to the blue-green light, while the transmission-mode Ga037Al063As photocathode is sensitive to the 532 nm light

Development of an Ultrahigh Resolution Block Detector Based on 0.4 mm Pixel Ce:GAGG Scintillators and a Silicon Photomultiplier Array

Abstract: Ce doped Gd3Al2Ga3O12 (Ce:GAGG) is a newly developed single-crystal scintillator which has a large light output and longer emission light wavelength. The longer wavelength of the scintillation photons will produce a larger signal when coupled to typical silicon photomultiplier (Si-PM) as the quantum efficiency of semiconductor based photodetector is generally higher for light with longer wavelength. A block detector with higher spatial resolution may thus be realized by combining Ce:GAGG with Si-PM arrays. To achieve the highest possible spatial resolution for PET and SPECT detectors, we developed an ultrahigh resolution block detector using 0.4 mm × 0.4 mm × 5 mm Ce:GAGG pixels assembled to form a 24 × 24 matrix that is coupled to an Si-PM array and evaluated the performance. All Ce:GAGG pixels were separated in the 2-dimensional position histograms for Cs-137 (662 keV) gamma photons with an average peak-to-valley (P/V) ratio of 2.4. The energy resolution was 21.6% FWHM for Cs-137 (662 keV) and 23.8% for Co-57 (122 keV) gamma photons. Since Ce:GAGG does not contain naturally occurring radioisotope (Lu), beta-gamma true coincidences can be avoided and randoms are reduced when used for PET detectors. Furthermore, this property, together with its high light output and good intrinsic energy resolution, make the scintillator suited for SPECT detectors. An ultrahigh resolution PET/SPECT hybrid system might be an interesting application using Ce:GAGG/Si-PM block detectors.

A High-Sensitivity Low-Cost Optical Particle Counter Design

Abstract: We report the design of a small optical particle counter with high sensitivity and low construction cost for atmospheric aerosol measurements. Particle sensing is based on the detection of the forward scattering of laser light. The separation of the laser beam and scattered light is achieved with a novel yet simple optical system. A laboratory prototype system with a 405-nm laser and photomultiplier tube detector has successfully detected polystyrene latex particles as small as 125 nm in diameter with unit efficiency. Theoretical calculations suggest that a lower detectable size limit of 100 nm can be achieved with reduction of background scattered light. The new counter will be useful in a variety of ground-based as well as small balloon-borne applications such as vertical profiling and in situ measurement of particles from explosive volcanic eruptions. Copyright 2013 American Association for Aerosol Research

Calibrating image plate sensitivity in the 700 to 5000 eV spectral energy range

Abstract: This paper describes a method to calibrate image plate sensitivity for use in the low energy spectral range. Image plates, also known as photostimulable luminescence (PSL) detectors, have often proved to be a valuable tool as a detector for plasma physics studies. Their advantages of large dynamic range, high stopping power, and resistance to neutron damage sometimes outweigh the problems of limited resolution and the remote processing required. The neutron damage resistance is required when the X-ray source is producing a high neutron flux. The Static X-ray Imager (SXI) is a key diagnostic on the National Ignition Facility (NIF) target chamber at LLNL for use in determining the symmetry of the laser beams. The SXI is essential to proper interpretation of the data from the Dante diagnostic to determine the X-ray radiation temperature. It is comprised of two diagnostics located at the top and the bottom of the target chamber. The usual detector is a large array CCD camera. For shots giving high yields of neutrons, the camera would not only be blinded by the neutrons, it would be damaged. To get around this problem, an image plate (IP) is used as the detector. The NIF application covers the energy range from 700 to 5000 eV. The type of image plates typically used for plasma physics are the Fuji BAS-MS, BAS-SR, and BAS-TR models. All models consist of an X-ray sensitive material made of BaF(Br,I):Eu 2+ embedded in a plastic binder. X-rays incident on the phosphor ionize the Eu 2+ producing Eu 3+ and free electrons that are trapped in lattice defects (F-centers) produced by the absence of halogen ions in the BaF 2 crystal. An image plate readout scanner irradiates the IP with a red laser causing reduction of the Eu 3+ and emission of a blue photon. The photon is collected using a photomultiplier and digitized to make an electronic image. Image plates are cleared of all F-centers by putting them under a bright light for about 10 minutes. They are then ready for producing a new X-ray image. The MS IP model has the higher sensitivity and the SR IP and TR IP models are designed for higher resolution. The MS and SR IPs have a thin Mylar coating that protects the sensitive layer. The TR model has no protective layer and is more sensitive at the lower X-ray energies but must be handled more carefully. The raw image data from the Fuji scanner can be converted to units of PSL that are proportional to the photon count. The equation relating PSL to the raw greyscale value is: PSL = (R/100) 2 (4000/S)exp 10 {L(G/(2 B -1)-1/2)} where R is the resolution in μm S is the sensitivity setting L is the latitude B is the dynamic range (8 or 16 bits) G is the raw image greyscale value. The IP photon sensitivity is defined as the PSL output per photon input and is a function of the photon energy. Meadowcroft et al in 2008 published the sensitivity for the three types of image plates in the spectral range from 1 to 100 keV. Maddox et al measured the sensitivity for type MS and SR image plates from 8 to 80 keV using the NSTec High Energy X-ray (HEX) source, a fluorescer type X-ray source. The Meadowcroft and Maddox measurements used similar X-ray sources for the higher spectral and the same type of IP scanner, the FLA 7000. There is reasonable agreement between the Maddox and Meadowcroft sensitivity measurements of MS and SR type IP for the at spectral energies above 20 keV, but the Maddox sensitivities are much lower than those of Meadowcroft in the energy range below 20 keV. Recently Bonnet et al published a model for the photon sensitivity based upon the amount of energy deposited and Monte Carlo calculations to incorporate the specifics of the X-ray absorption and the readout process. The model was calibrated for sensitivity using radioactive sources. The model was compared to the previous publications cited. The Bonnet model tends to agree with the Meadocroft measurements at the low spectral energies. The present paper describes the measurement of IP sensitivity in the spectral range from 700 to 8000 eV. The sensitivity in this spectral range had not previously been measured and was needed for the NIF application. A calibration at the low energy range was done using a diode source and a band pass filter. X-ray beam is filtered and limited by the applied voltage to provide a spectral band that is about 1/10 of the average spectral energy. The X-ray flux is measured using a photodiode that is traceable to National Institute for Standards and Technology (NIST). The spectrum for each X-ray band is measured using a silicon drifted detector. The photodiode calibration method is described. Measurements were made on SR, TR, and specially coated TR image plates. The measurement results will be presented and the uncertainties in the measurement will be discussed. The results will be compared to other measurements and estimation methods.

Characterization of the Hamamatsu R11780 12 in. photomultiplier tube

Abstract: Future large water Cherenkov and scintillator detectors have been proposed for measurements of long baseline neutrino oscillations, proton decay, supernova and solar neutrinos. To ensure cost-effectiveness and optimize scientific reach, one of the critical requirements for such detectors are large-area, high performance photomultiplier tubes (PMTs). One candidate for such a device is the Hamamatsu R11780, a 12 in. PMT that is available in both standard and high quantum efficiency versions. Measurements of the single photoelectron response characteristics, relative efficiencies of the standard and high quantum efficiency versions, a preliminary measurement of the absolute quantum efficiency of the standard quantum efficiency version, and a two-dimensional scan of the relative efficiency across the photocathode surface are presented in this paper. All single photoelectron investigations were made using a Cherenkov light source at room temperature at a gain of 1×107. These results show that the R11780 PMT is an excellent candidate for such large optical detectors.

Expansion cone for the 3-inch PMTs of the KM3NeT optical modules

Abstract: Detection of high-energy neutrinos from distant astrophysical sources will open a new window on the Universe. The detection principle exploits the measurement of Cherenkov light emitted by charged particles resulting from neutrino interactions in the matter containing the telescope. A novel multi-PMT digital optical module (DOM) was developed to contain 31 3-inch photomultiplier tubes (PMTs). In order to maximize the detector sensitivity, each PMT will be surrounded by an expansion cone which collects photons that would otherwise miss the photocathode. Results for various angles of incidence with respect to the PMT surface indicate an increase in collection efficiency by 30% on average for angles up to 45° with respect to the perpendicular. Ray-tracing calculations could reproduce the measurements, allowing to estimate an increase in the overall photocathode sensitivity, integrated over all angles of incidence, by 27% (for a single PMT). Prototype DOMs, being built by the KM3NeT consortium, will be equipped with these expansion cones.

Comparison of deuterated and normal liquid scintillators for fast-neutron detection

Abstract: Liquid organic scintillators have long been used for fast-neutron detection due to their fast response and the ability to use pulse-shape discrimination (PSD) to distinguish between neutron and γ� ray interactions. Deuterated liquid organic scintillators have, in addition to the aforementioned properties, structure on their pulse-height spectra due to the different characteristics of n–d vs. n–p scattering. We report on the direct comparison of two small-volume liquid scintillator detectors with exactly the same geometries (11.43 cm diameter and 2.54 cm thickness); the first based on NE213 produced by Nuclear Enterprise, and the second based on EJ-315 produced by Eljen Technologies, the latter being a deuterated scintillator. A variety of photomultiplier tubes (PMTs) were used, but the quality of the data was determined to be independent of the PMT type. It is shown that, while the light output of the deuterated detector is lower than for the conventional non-deuterated detector, it is possible to detect 60 keV neutrons. The PSD capabilities of the deuterated detector match and surpass those of the NE213 detector. Its efficiency is comparable to that of the NE213 detector at neutron energies above 2 MeV; below that energy its relative efficiency suffers from the significantly lower n–d scattering cross-section. For very low neutron energies (o200 keV), the relative efficiency of the deuterated detector increases again, due to the lower noise level for our particular detectors, showing the importance of low photomultiplier tube noise for the detection of low-energy neutrons.

Study of light transport inside scintillation crystals for PET detectors.

Abstract: Scintillation crystal design is a critical component in positron emission tomography system development, which impacts a number of performance parameters including energy resolution, time resolution and spatial resolution. Our work aims to develop a generalized simulation tool to model the light transport inside scintillation crystals with good accuracy, taking into account surface treatments, reflectors, temporal dependence of scintillation decay, and comprehensive experimental validations. The simulation has been validated against both direct analytical calculation and experimental measurements. In this work, the studies were performed for a lutetium?yttrium oxyorthosilicate crystal of 3?3?20?mm3?dimension coupled to a Hamamatsu silicon photomultiplier, with respect to light output, rise-time slope, energy resolution and time resolution. Four crystal surface treatment and reflector configurations were investigated: GroundMetal, GroundPaint, PolishMetal and PolishPaint. The experiments were performed to validate the Monte Carlo simulation results. The results indicate that the best time resolution (0.96?0.05?ns) and good energy resolution (10.6?0.4%) could be produced by using a polished surface with specular reflector, while the configuration of a polished surface with diffusive reflector produces the best energy resolution (10.2?0.9%). The results indicate that a polished surface with diffusive reflector achieves the best energy resolution (10.2?0.9%) for 511?keV high energy photons, and a polished surface with specular reflector achieves the best time resolution (0.96?0.05?ns) measured against a Hamamatsu fast photomultiplier tube. The ground surface treatment is not recommended for its inferior performance in terms of energy and time resolution. Possible explanations and future improvements to be made to the developed simulation tool are discussed.

Detection system for forward emitted photons at the Experimental Storage Ring at GSI

Abstract: A single photon counting system has been developed for efficient detection of forward emitted fluorescence photons at the Experimental Storage Ring (ESR) at GSI. The system employs a movable parabolic mirror with a central slit that can be positioned around the ion beam and a selected low noise photomultiplier for detection of the collected photons. Compared to the previously used system of mirror segments installed inside the ESR the collection efficiency for forward-emitted photons is improved by more than a factor of 5. No adverse effects on the stored ion beam have been observed during operation besides a small drop in the ion current of about 5% during movement of the mirror into the beam position. The new detection system has been used in the LIBELLE experiment at ESR and enabled for the first time the detection of the ground-state hyperfine M1 transition in lithium-like bismuth (209Bi80+) in a laser-spectroscopy measurement.

Experimental search for solar hidden photons in the eV energy range using kinetic mixing with photons

Abstract: We have searched for solar hidden photons in the eV energy range using a dedicated hidden photon detector. The detector consisted of a parabolic mirror with a diameter of 500 mm and a focal length of 1007 mm installed in a vacuum chamber, and a photomultiplier tube at its focal point. The detector was attached to the Tokyo axion helioscope, Sumico which has a mechanism to track the sun. From the result of the measurement, we found no evidence for the existence of hidden photons and set a limit on the photon-hidden photon mixing parameter χ depending on the hidden photon mass mγ'.

Experimental search for solar hidden photons in the eV energy range using kinetic mixing with photons

Abstract: We have searched for solar hidden photons in the eV energy range using a dedicated hidden photon detector. The detector consisted of a parabolic mirror with a diameter of 500mm and a focal length of 1007mm installed in a vacuum chamber, and a photomultiplier tube at its focal point. The detector was attached to the Tokyo axion helioscope, Sumico which has a mechanism to track the sun. From the result of the measurement, we found no evidence for the existence of hidden photons and set a limit on the photon-hidden photon mixing parameter \chi depending on the hidden photon mass m_{\gamma '}.

Readout Electronics and Data Acquisition of a Positron Emission Tomography Time-of-Flight Detector Module With Waveform Digitizer

Abstract: A multi-element silicon photomultiplier (SiPM) based time-of-flight (ToF) detector module for positron emission tomography (PET) has been developed. The detector module is based on a 4 × 4 array of LYSO-SiPM elements (Hamamatsu MPPC S10931-050P), with individual bias supply for each element. Each element is read out by a wideband, low-noise RF amplifier to maximize timing performance. All 16 outputs are digitized with a high-speed CAEN V1742 digitizer module (32 + 2 channels, 5 GS/s sampling, 12-bit amplitude resolution, 500 MHz input bandwidth) to acquire raw pulse waveforms for offline timing and energy extraction. As the digitizer has no internal trigger for individual channels, a trigger board has been developed which produces a fast pulse that triggers the digitizer whenever any pixel of the detector detects a signal in coincidence with a reference detector. To assess the performance of the prototype module, a 4 × 4 LYSO scintillator array ( 3×3×5 mm3 elements) was coupled to the SiPM photodetectors and energy/timing resolution measurements were performed using a Ge-68 source. At 1.4 V overvoltage, the energy resolution, not corrected for saturation effects of the SiPM, varied from a minimum of 10.1% to a maximum of 13.3% with an average energy resolution of 11.4 ± 0.8% across the 16 channels. With a reference detector (single 3×3×5 mm3 LYSO crystal coupled to a Hamamatsu MPPC S10362-33), the average coincidence resolving time (CRT) across the detector module was 206 ± 7 ps FWHM at 2.4 V overvoltage-the best reported for a PET block (array) detector based on conventional photodetectors to date.

Photosensor characterization for the Cherenkov Telescope Array: silicon photomultiplier versus multi-anode photomultiplier tube

Abstract: Photomultiplier tube technology has been the photodetector of choice for the technique of imaging atmospheric Cherenkov telescopes since its birth more than 50 years ago. Recently, new types of photosensors are being contemplated for the next generation Cherenkov Telescope Array. It is envisioned that the array will be partly composed of telescopes using a Schwarzschild-Couder two mirror design never built before which has significantly improved optics. The camera of this novel optical design has a small plate scale which enables the use of compact photosensors. We present an extensive and detailed study of the two most promising devices being considered for this telescope design: the silicon photomultiplier and the multi-anode photomultiplier tube. We evaluated their most critical performance characteristics for imaging γ-ray showers, and we present our results in a cohesive manner to clearly evaluate the advantages and disadvantages that both types of device have to offer in the context of GeV-TeV γ-ray astronomy.