Hamamatsu Multi-pixel Photon Counter Research Articles

A study for gamma attenuation behavior of polyimide (PI) film by MPPC

Although lead is a very good radiation shielding material, its toxicity has led researchers to find alternative materials instead of it. Moreover, as the use of Kapton polyimide (PI) film in nuclear power plants and space exploration increases, the need to reveal the radiation degradation properties of this material has come along. In this regard, in the present study, it is aimed to determine the mass and linear attenuation coefficients, half value layer, tenth value layer, mean free path and radiation protection efficiency attenuation parameters for this material, experimentally and theoretically, by using the gammas of the 133Ba radioisotope. Experimental gamma attenuation measurements were made by a spectrometer using a Hamamatsu multi pixel photon counter device with a silicon photomultiplier sensor. The constant fraction discrimination timing method was used to reduce the electronic noise of the spectrometer. The attenuation parameters determined experimentally by following two ways were compared with the theoretical ones obtained from the XCOM program.

Validation of the design of a high-sensitivity and high-resolution PET system for a preclinical PET/EPR hybrid scanner

We report the development of a high-sensitivity and high-resolution PET subsystem for a next-generation preclinical PET/EPR hybrid scanner for investigating and improving hypoxia imaging with PET. The PET subsystem consists of 14 detector modules (DM) installed within a cylindrical supporting frame whose outer and inner diameters are 115 mm and 60 mm, respectively. Each DM contains eight detector units (DU) in a row and each DU is made of a 12 × 12 array of 1 × 1 × 10mm3 LYSO crystals (with a 1.05 mm pitch) coupled to a 4 × 4 silicon photomultiplier (SiPM) array that has a 3.2 mm pitch (Hamamatsu multi-pixel photon counter (MPPC) array 14161-3050HS-04). The PET subsystem has a 104 mm axial field-of-view (AFOV) that is sufficient for full-body mouse imaging, therefore enabling temporal and spatial correlation studies of tumor hypoxia between PET and EPR. It employs 1mm-width crystals to support sub-millimeter image resolution that is desired for mouse imaging. Although a DM contains 1,152 LYSO crystals, by use of a newly devised signal readout method only six outputs are produced. Recently a partial prototype of this subsystem consisting of four DMs is built. In this paper, we present performance measurement results obtained for the developed DMs and initial imaging results obtained by the prototype. The developed DMs show uniformly superior performance in identifying the hit crystal and detector unit, in energy resolution, and in coincidence time resolution. The images obtained for a 22Na point source and a 18F-filled U-shaped tube source show an image resolution of about 1.1 mm and 1.2 mm FWHM in the transverse and axial directions respectively, and demonstrate successful imaging over the entire 104 mm AFOV of the prototype. This estimated image resolution however includes the contribution by the source size.

VIDARR: Aboveground Reactor Monitoring

Technology developed for the T2K electromagnetic calorimeter has been adapted to make a small footprint, reliable, segmented detector to characterise anti-neutrinos emitted by nuclear reactors. Based on the design of the T2K Near Detector ECal, the device detects anti-neutrinos through the distinctive delayed coincidence signal of inverse β-decay interactions using plastic scintillator and Hamamatsu Multi-Pixel Photon Counters. The device has been developed and constructed at the University of Liverpool and is situated in a 20 ft ISO container unit, capable of operating aboveground. The device finished a successful field trial at the Wylfa Magnox Reactor on Anglesey, UK where it was located roughly 60 m from the 1.5 GWth reactor core and is now undergoing an upgrade with 50% more mass and channels as well as new electronics and sensors.

Radiation tests of Hamamatsu multi-pixel photon counters

Results of radiation tests of Hamamatsu 2.0 × 2.0 mm2 through-silicon-via (S13360-2050VE) multi-pixel photon counters, or MPPCs, are presented (Hamamatsu, 0000). Distinct sets of eight MPPCs were exposed to four different 1 MeV neutron equivalent doses of 200 MeV protons. Measurements of the breakdown voltage, gain and noise rates at different bias overvoltages, photoelectron thresholds, and LED illumination levels were taken before and after irradiation. No significant deterioration in performance was observed for breakdown voltage, gain, and response. Noise rates increased significantly with irradiation. These studies were undertaken in the context of MPPC requirements for the Cosmic Ray Veto detector of the Mu2e experiment at the Fermi National Accelerator Laboratory.

A Silicon Photomultiplier Readout ASIC for Time-of-Flight Applications Using a New Time-of-Recovery Method

Silicon photomultiplier timing chip (STiC) is a 64-channel mixed-mode application-specific integrated circuit in the $0.18-\mu \text{m}$ CMOS technology from Univited Microelectronics Corporation (UMC) for silicon photomultiplier (SiPM) readout with very high timing resolution. It is designed for time-of-flight measurements in positron emission tomography and high-energy physics experiments. In order to achieve the best timing performance without compromising the charge/energy measurement, a novel time-based signal processing technique called “time-of-recovery (ToR)” method has been developed and implemented in the analog front end of the chip. This technique converts the incoming charge into a digital pulse with a linearized time-over-threshold width. Measurements have shown a time jitter smaller than 20 ps for the analog front end and smaller than 40 ps for the time-to-digital converter and the digital part. A coincidence time resolution of 214-ps full-width at half-maximum (FWHM) has been obtained with STiC using $3.1{\times }3.1{\times }15$ mm3 LYSO:Ce crystals and Hamamatsu multi pixel photon counters (S12643-050CN(X)). The measured energy resolution for a 511-keV photon is 11.2% FWHM after correcting for SiPM saturation effects. In this paper, we report on the details of the ToR method and how it is embedded within the STiC design; results of performance measurements as well as the 128-channel front-end module used for the EndoTOFPET-US project are also presented.

Measurement of the energy and time resolution of a undoped CsI + MPPC array for the Mu2e experiment

This paper describes the measurements of energy and time response and resolution of a 3×3 array made of undoped CsI crystals 3×3×20 cm3 coupled to large area Hamamatsu Multi Pixel Photon Counters 12×12 mm2. The measurements have been performed using the electron beam of the Beam Test Facility in Frascati (Rome, Italy) in the energy range 80–120 MeV. The measured energy resolution, estimated with the FWHM, at 100 MeV is 16.4%. This resolution is dominated by the energy leakage due to the small dimensions of the prototype. The time is reconstructed by fitting the leading edge of the digitized signals and applying a digital constant fraction discrimination technique. A time resolution of about 110 ps at 100 MeV is achieved.

Characterization and modeling of crosstalk and afterpulsing in Hamamatsu silicon photomultipliers

The crosstalk and afterpulsing in Hamamatsu silicon photomultipliers, called Multi-Pixel Photon Counters (MPPCs), have been studied in depth. Several components of the correlated noise have been identified according to their different possible causes and their effects on the signal. In particular, we have distinguished between prompt and delayed crosstalk as well as between trap-assisted and hole-induced afterpulsing.The prompt crosstalk has been characterized through the pulse amplitude spectrum measured at dark conditions. The newest MPPC series, which incorporate isolating trenches between pixels, exhibit a very low prompt crosstalk, but a small component remains likely due to secondary photons reflected on the top surface of the device and photon-generated minority carriers diffusing in the silicon substrate.We present a meticulous procedure to characterize the afterpulsing and delayed crosstalk through the amplitude and delay time distributions of secondary pulses. Our results indicate that both noise components are due to minority carriers diffusing in the substrate and that this effect is drastically reduced in the new MPPC series as a consequence of an increase of one order of magnitude in the doping density of the substrate.Finally, we have developed a Monte Carlo simulation to study the different components of the afterpulsing and crosstalk. The simulation results support our interpretation of the experimental data. They also demonstrate that trenches longer than those employed in the Hamamatsu MPPCs would reduce the crosstalk to a much greater extent.

MPPC photon sensor operational experience in CMS

During the first long shutdown of the LHC the Outer Hadron Calorimeter of CMS has been equipped with silicon photomultipliers that replace the existing hybrid photodiodes while maintaining most of the readout chain. The new photon sensors are Hamamatsu MultiPixel Photon Counters with an active area of 3 mm × 3 mm and a cell pitch of 50 μm. Different means of determining the device's breakdown voltage and gain are presented. The stability of the overall system temperature as well as the stability of the gain and the breakdown voltage of the silicon photomultipliers are studied. The correlation between the different methods of determining the gain and breakdown voltage is tested to find whether they yield comparable results.

A simple and robust method to study after-pulses in Silicon Photomultipliers

The after-pulsing probability in Silicon Photomultipliers and its time constant are obtained measuring the mean number of photo-electrons in a variable time window following a light pulse. The method, experimentally simple and statistically robust due to the use of the Central Limit Theorem, has been qualified applying it to an HAMAMATSU Multi Pixel Photon Counter (MPPC) S10362-11-100C.

Operation of Multi-Pixel Photon Counters Down to Liquid Helium Temperatures

We are investigating the possibility of using Silicon Avalanche Photo Detectors (APD), both in proportional and in Geiger mode, to readout inorganic scintillators operated at cryogenic temperatures. Such detectors, that need to operate close to liquid helium (LHe) temperatures and in a magnetic field of a few Tesla, have been proposed by our group as a way to build an active polarized target to be used for neutrino physics, for the search of axions and CP violation, as suggested by some theoretical papers. In the present work we investigate in some details the performance of Hamamatsu Multi-Pixel Photon Counters (MPPCs) down to LHe temperature to verify the temperature range of usability of these devices.

A GEANT4 Monte Carlo simulation to describe the time response of a coupled SiPM and LYSO detection system

In recent years the silicon photomultiplier has been investigated as an alternative to the traditional photomultiplier tube in a range of applications, including Time-of-flight Positron Emission Tomography (TOF-PET). In this paper we discuss a GEANT4 simulation framework, which has been developed to drive the design of a scalable TOF-PET apparatus to be built at the Rutherford Appleton Laboratory, UK. First results presented in this paper simulate the response of an Hamamatsu Multi-Pixel Photon Counter (S10362-33-050c) coupled to LYSO scintillating crystals, with focus on the timing response of coincidence signals.

Novel Hamamatsu Multi-Pixel Photon Counter (MPPC) array studies for the GlueX experiment: New results

The novel Hamamatsu Multi-Pixel Photon Counter (MPPC) S12045(X) is an array of 16 individual 3×3mm2 MPPC devices each with 3600 Geiger-mode Avalanche Photodiode pixels of 50×50μm2. Each MPPC in the array operates at a reverse bias of approximately 70V. This paper summarizes our characterization of MPPC arrays used in the GlueX experiment in Hall D at Thomas Jefferson National Accelerator Facility (Jefferson Lab). We studied the main features of each of the 16 MPPC array channels for 2800 MPPC arrays at several different temperatures. Two measurement stations were built to extract gain, breakdown voltage, photon detection efficiency, optical crosstalk and dark rate for each of the 44800 MPPC array channels at each temperature setting. The hardware and the data analysis are described, and new analytical expressions for the mean number of photoelectrons and optical crosstalk are presented, as well as systematic trends of the performance parameters.

Pixelated Geiger-Mode Avalanche Photo-Diode Characterization Through Dark Current Measurement

PIXELATED geiger-mode avalanche photodiodes(PPDs), often called silicon photomultipliers (SiPMs) are emerging as an excellent replacement for traditional photomultiplier tubes (PMTs) in a variety of detectors, especially those for subatomic physics experiments, which requires extensive test and operation procedures in order to achieve uniform responses from all the devices. In this paper, we show for two PPD brands, Hamamatsu MPPC and SensL SPM, that the dark noise rate, breakdown voltage and rate of correlated avalanches can be inferred from the sole measure of dark current as a function of operating voltage, hence greatly simplifying the characterization procedure. We introduce a custom electronics system that allows measurement for many devices concurrently, hence allowing rapid testing and monitoring of many devices at low cost. Finally, we show that the dark current of Hamamastu Multi-Pixel Photon Counter (MPPC) is rather independent of temperature at constant operating voltage, hence the current measure cannot be used to probe temperature variations. On the other hand, the MPPC current can be used to monitor light source conditions in DC mode without requiring strong temperature stability, as long as the integrated source brightness is comparable to the dark noise rate.

Characterization of novel Hamamatsu Multi Pixel Photon Counter (MPPC) arrays for the GlueX experiment

The novel Hamamatsu Multi Pixel Photon Counter Array S12045(X) is an array of 16 individual MPPCs (3×3mm2) (further in the paper MPPC array channel) each with 3600 G-APD (Geiger-mode Avalanche Photodiodes) pixels (50×50 [μm2]). Each MPPC in the array works with its individual reverse bias voltage mode (around 70V). The paper summarizes the characterization process of MPPC arrays used in GlueX experiment (Hall D, Jefferson Lab). We studied the main features of each MPPC array channel for 2800 MPPC arrays at different temperatures. Two measurement stations were built to extract gain, breakdown voltage, photo detection efficiency (PDE), optical crosstalk and dark rate for each MPPC array channel. The hardware and the data analysis are described, which includes new analytical expressions to obtain the mean number of photo-electrons and optical crosstalk. The dynamical behavior of characterization parameters is presented as well.

MPPC Arrays in PET Detectors With LSO and BGO Scintillators

Presently, a majority of studies concerning application of silicon photomultipliers (SiPMs) in positron emission tomography detectors are focused on scintillators containing lanthanum (LaBr3) or lutetium (LSO, LYSO, or LFS). However, the modules with the well-known BGO in combination with SiPM light readout are also interesting, owing unique features of SiPMs. In this paper, the two types of detectors, based on BGO and LSO scintillators, are compared in terms of requirements for positron emission tomography scanners. The presented studies are performed with two Hamamatsu Multi Pixel Photon Counter (MPPC) arrays of 2 × 2 channels, with the total area of 6 × 6 mm2 and micro-pixel size of 25 μm (S10985-025C) and 50 μm (S10985-050C). The measurements of a number of photoelectrons, energy resolution at 511 keV and 22Na time resolution are reported for various sizes of the scintillators, including 2.75 × 2.75 × 20 mm3 pixel and single crystals covering the whole MPPC active area. The paper is more focused on optimization of the system with BGO as its performance in combination with SiPM light readout is less known. The aim of this work is to show advantages of a SiPM-based detector, especially in combination with BGO, in respect to the block detectors where classic photomultipliers are used.

SiPM-PET with a short optical fiber bundle for simultaneous PET-MR imaging

For positron emission tomography (PET) inserts to magnetic resonance imaging (MRI) applications, optical fibers have been used for some time to transfer scintillation photons to photomultiplier tubes positioned outside the fringe magnetic field. We previously proposed a novel utilization of an optical fiber for good radio frequency (RF) transmission from body coils to an imaging object. Optical fiber bundles between silicon photomultipliers (SiPM) and scintillation crystals provide an increased spacing between RF-shielded electronics boxes, facilitating RF passage from the body RF coils to imaging objects. In this paper, we present test results of a SiPM-PET system with a short optical fiber bundle for simultaneous PET-MR imaging. We built the SiPM-PET system which consisted of 12 SiPM-PET modules; each module was assembled with a lutetium yttrium oxyorthosilicatecrystal block, a 31 mm optical fiber bundle, a Hamamatsu multi-pixel photon counter S11064-050P and a signal processing box shielded with copper. The SiPM-PET system, with a face-to-face distance of 71 mm, was placed inside a 3 T MRI. A small surface coil placed inside the SiPM-PET system was used to receive the signal from phantoms while the body RF coil transmitted the RF pulses. The SiPM-PET system showed little performance degradation during the simultaneous PET-MR imaging and it caused no significant degradation of MR images with turbo spin echo (TSE), gradient echo or 3D spoiled gradient recalled sequences. Echo planar imaging MR images with and without the SiPM-PET inside the MR scanner were significantly worse than the images obtained with the TSE sequence.

The Neutrino Near Detector Complex of the T2K Experiment

Abstract The Tokai to Komiaka (T2K) experiment is designed to investigate neutrino oscillations. The Near Detector purposes are to characterize the neutrino beam produced at the J-PARC accelerator complex, and to measure neutrino cross-sections. Super-Kamiokande, the far detector, is located at 2.5 degrees with respect to the J-PARC neutrino beam. The Near Detector is composed of two main sub-detectors: one an on-axis, whose primary purpose is to monitor the beam flux and spatial distribution, and one an off-axis, in the general direction of Super-Kamiokande, that includes tracking and calorimetric capabilities. Excluding the Time Projection Chambers (TPCs), the Near Detector is an assembly of similar building blocks: extruded plastic scintillator, readout by wavelength shifting fibers and Hamamatsu Multi-Pixel Photon Counters. The Near Detector has been in operation since the end of 2009. All the sub-detectors are performing very well providing high quality data about the neutrino beam and interaction processes.

Development of a high-resolution Si-PM-based gamma camera system

A silicon photomultiplier (Si-PM) is a promising photodetector for PET, especially for PET/MRI combined systems, due to its high gain, small size, and lower sensitivity to static magnetic fields. However, these properties are also promising for gamma camera systems for single-photon imaging. We developed an ultra-high-resolution Si-PM-based compact gamma camera system for small animals. Y2SiO5:Ce (YSO) was selected as scintillators because of its high light output and no natural radioactivity. The gamma camera consists of 0.6 mm × 0.6 mm × 6 mm YSO pixels combined with a 0.1 mm thick reflector to form a 17 × 17 matrix that was optically coupled to a Si-PM array (Hamamatsu multi-pixel photon counter S11064-050P) with a 2 mm thick light guide. The YSO block size was 12 mm × 12 mm. The YSO gamma camera was encased in a 5 mm thick gamma shield, and a parallel hole collimator was mounted in front of the camera (0.5 mm hole, 0.7 mm separation, 5 mm thick). The two-dimensional distribution for the Co-57 gamma photons (122 keV) was almost resolved. The energy resolution was 24.4% full-width at half-maximum (FWHM) for the Co-57 gamma photons. The spatial resolution at 1.5 mm from the collimator surface was 1.25 mm FWHM measured using a 1 mm diameter Co-57 point source. Phantom and small animal images were successfully obtained. We conclude that a Si-PM-based gamma camera is promising for molecular imaging research.

Improvement of Energy Thresholds for Scintillation Detectors Using a Monolithic 2 ×2 Multi-Pixel Photon Counter Array with a Coincidence Technique

The performance of a large-area, monolithic Hamamatsu multi-pixel photon counter (MPPC) was tested consisting of a 2 ×2 array of 3 ×3 mm 2 pixels. MPPC is a novel type of semiconductor photodetector comprising multiple avalanche photodiode (APD) pixels operated in Geiger mode. Despite its great advantage of signal multiplication comparable to that achieved with the photomultiplier tube (PMT), the detection of weak scintillation light signals is quite difficult due to the severe contamination of dark counts, which typically amounts to ≃1 Mcps/3 ×3 mm 2 at room temperature. In this study, a coincidence technique was applied for scintillation detectors to improve the detection efficiency for low energy gamma-rays. The detector consisted of a 10 ×10 ×10 mm 3 crystals of GSO, BGO, and Pr:LuAG optically coupled with the 2 ×2 MPPC-array. With this technique, we demonstrated that the contamination of dark counts was reduced with a rejection efficiency of more than 99.8%. As a result, 22.2 keV gamma-rays were succ...

A Feasibility Study on the Use of Optical Fibers for the Transfer of Scintillation Light to Silicon Photomultipliers

Integrated PET/MRI units with simultaneous acquisition capability are set to play an important role in studies of human breast and prostate imaging and brain function. However, to take advantage of existing MRI units in hospitals and institutions, minimally modified combined PET MRI is highly desirable. In addition, the current MRI trend is to utilize powerful body coils to transmit radio-frequency (RF) waves and local RF coils to receive signals. The authors propose a silicon photomultiplier (SiPM) PET equipped with optical fiber bundles that transfer photons from scintillation crystal to SiPM. To investigate the feasibility of SiPM PET using optical fiber bundles, the authors studied the performances of SiPM/scintillator couplings using single optical fibers and a fiber bundle. GEANT4 Monte-Carlo simulation was used to study scintillation photon transfer from scintillation crystals to the SiPM. This simulation showed that light loss, due to the bending of an optical fiber, is not significant for a fiber with a diameter of 2.0 mm and a bending radius of greater than 25 mm. To validate the GEANT4 Monte-Carlo simulation, several simple detectors were assembled and tested. Simulation results agreed reasonably well with experimental results. Two Hamamatsu multi-pixel photon counters (MPPCs) were tested using double clad optical fibers of 1.5 mm and 2.0 mm diameter, and 25 mm and 50 mm bending radius, respectively. When two MPPCs were directly attached to 2.0 × 2.0 × 10.0 mm3 LYSO crystals, a ~14% energy and a ~1.3 ns coincidence timing resolution were obtained at full width half maximum (FWHM). With one of the MPPCs attached to an optical fiber of 1.5 mm diameter, 50 mm bending radius, and length 300 mm, energy and coincidence timing resolutions were 27% and 2.2 ns, respectively. With an optical fiber bundle made of bare fibers with 1.5 mm diameter and length 100 mm, an ~ 26% energy resolution was obtained. Even though the Monte-Carlo simulation showed light loss was not significant for a single 90° turn of bending, the mechanical integrity of the optical fiber, especially the absence of cracks which can be caused by sharp bending, seemed to be a far more important constraint on sharp bending. These initial results are encouraging with respect to the use of combined SiPM PET using optical fibers.