Silicon Photomultiplier Modules Research Articles

Design and manufacture of scintillation detector using CsI(Tl) crystal coupled with silicon photomultipliers

In this research, a scintillation detector was developed using the CsI(Tl) scintillator crystal coupled with a silicon photomultiplier (SiPM) to replace the photomultiplier tube (PMT), resulting in a compact and energy-efficient detector. A rectangular box-shaped CsI(Tl) scintillation crystal with dimensions of 50x25x25 mm from Kinheng and a SiPM module S13361-3050AE-08 with dimensions of 25x25 mm from Hamamatsu were selected to use. The preamplifier circuit, power supply, and temperature stabiliser have also been integrated into the detector. The characteristics of this detector were evaluated using a 137Cs standard radioactive source together with Ortec’s multichannel analyser device and Gamma Vision software for spectrum analysis. Results showed that the energy resolution for the 137Cs peak of this detector is about 8.03%, which is almost equivalent to the energy resolution of 7.87% of the Canberra detector using 76x76 mm NaI(Tl) crystal coupled to the PMT. The results of the evaluation of stability over time when the operating ambient temperature of this detector with no change showed that the energy peak position and the energy resolution for the 137Cs radioactive source are almost unchanged. The research also investigated the stability of the detector according to the operating ambient temperature. The results exhibited that the output pulse amplitude varies greatly with the ambient temperature, it decreases when the temperature increases and vice versa. Under the condition that the operating ambient temperature varies from 11oC to 50oC, the energy peak position of 137Cs changes were 1762 and 167 channels, respectively in the cases without and with adjustment of output pulse amplitude stabilisation function in power supply for SiPM. When there is a function of output pulse amplitude stabilisation, the change in peak position according to operating ambient temperature is still about 4.3 channels/oC, so further research is needed to correct the influence of ambient temperature on the operation of this detector, to provide wide applicability of scintillation detector using SiPM to replace traditional PMT in the future.

SiPM module for the ACME III electron EDM search

This report shows the design and performance of a large area Silicon Photomultiplier (SiPM) module developed for the detection of fluorescent light emitted from a ∼1 liter scale volume. The module was optimized for the planned ACME III electron electric dipole moment (eEDM) search, which will be a ∼10 TeV probe for the existence of physics beyond the Standard Model of particle physics. The ACME experiment searched for the eEDM with the world’s highest sensitivity using cold ThO polar molecules (ACME II (Andreev et al., 2018 )). In ACME III, SiPMs will be used for detection of fluorescent photons (the fundamental signal of the experiment) instead of PMTs, which were used in the previous measurement. We have developed an optimized SiPM module, based on a 16-channel SiPM array. Key operational parameters are characterized, including gain and noise. The SiPM dark count rate, background light sensitivity, and optical crosstalk are found to all be well suppressed and more than sufficient for the ACME III application.

Development of a dual-end detector with TOF and DOI capabilities using crystal bars segmented by subsurface laser engraving

The quality and uniformity of positron emission tomography (PET) images can be improved significantly using a PET scanner, which has both time-of-flight (TOF) and depth-of-interaction (DOI) capabilities. We have already developed a DOI dual-end detector using segmented crystal bars by applying a subsurface laser engraving (SSLE) technique, and the DOI was determined by the ratio of the detected light between two readouts using the Anger calculation. In this study, we investigated the influence of the number of DOI segments on the performance of DOI identification and the coincidence timing performance of the detector. The detector consisted of a single lutetium fine silicate (LFS) crystal bar (3 × 3 × 20 mm 3 ) with various numbers of DOI segments that were made by applying the SSLE technique and Hamamatsu silicon photomultiplier (SiPM) modules. The maximum number of DOI segments was six, and the SiPM module included one hundred forty-four 4 mm × 4 mm SiPM readouts. The coincidence resolving time (CRT) of each DOI segment was obtained from the side irradiation of the dual-end detector. All DOI segments of the detector with 2, 3, 4, 5 or 6 DOI segments were clearly identified, and average energy resolutions of 9.8 ± 0.5% and 12.5 ± 1.4% were obtained at the 511 keV photo peak for the detectors with 2 DOI and 6 DOI segments, respectively. The minimum and maximum estimated CRT of 180 ± 6 ps and 236 ± 6 ps were obtained for the detectors with 2 DOI and 6 DOI segments, respectively. Insignificant differences were observed between the CRT values of different segments of one detector. Greater CRT values were obtained for detectors with larger DOIs. The results of this study prove that there is a high potential for segmented crystal bars using the SSLE technique as a good candidate for PET scanners with TOF and DOI capabilities, which can significantly improve the quality of PET images.

LTCC-Based Highly Integrated SiPM Module with Integrated Liquid Cooling Channels for High Resolution Molecular Imaging

We present a very compact hybrid detection module based on an advanced liquid-cooled low temperature cofired ceramic (LTCC) substrate. The double sided hybrid combines 144 photo detectors and four specialized flip chip readout ASICs (Application specific Integrated Circuits) used for the readout of scintillation crystals with application in time-of-flight positron emission tomography (PET) combined with magnetic resonance imaging (MRI). If MRI images and PET images are combined, completely new medical diagnostic and treatment prospects are feasible because the two techniques are complementary and they will offer both anatomical and functional information. One of the biggest challenges is the development of miniaturized detector modules that are highly functional and MRI compatible. Our SiPM (Silicon Photomultiplier) module has an area of 32.8 by 32.0 mm2 and contains 12 × 12 SiPMs in a pitch of 2.5 mm2. The SiPM readout of the 144 channels is performed by four PETA6 ASICs. The LTCC substrate with a 2.1 mm thickness has been manufactured using the most advanced technologies developed at Micro Systems Engineering GmbH To guarantee the manufacturability in serial or mass production, DP951 P2 green tape has been used. For the cooling channels, special technology has been developed by MSE. The liquid cooling channels inside the LTCC substrate provide excellent cooling for the ASICs, the SiPMs, and thermal insulation between ASICs and SiPMs and allow a very compact design of the detector modules, reducing their height by 50% compared with other technical solutions. We can insert a ring of our modules in an existing MR (Magnetic Resonance) scanner. Operating the SiPMs at low temperature improves their performance, reducing the effects of dark count rate and improving image quality. There is no heatsink, heat pipe, or other cooling element attached to the back side of the ASICs. To avoid interference between the PET and MRI system, short signal length is required for minimizing pickup loops and eddy currents. The 12 SiPM arrays with 2 × 6 geometry are wire bonded only at the edges of the SiPMs to the LTCC, enabling the use of nearly the whole detector area for photon detection, which is of paramount importance for excellent image quality. At the opposite side of the substrate, four ASICs with 272 μm bump pitch are flip chip solder assembled to the LTCC substrate including underfilling, and a few SMD (Surface Mount Device) components are mounted. A scintillator crystal array on top of the SiPMs converts gamma rays (511 keV photons produced from positron-electron annihilation) into light. We assume that the LTCC substrates and all components are fully MRI compatible, which is important for the integration of PET with MRI without mutual interference. The paper elucidates the impact of the used technology on the performance of advanced PET/MRI detector modules.

R&D of the CEPC scintillator-tungsten ECAL

The circular electron and positron collider (CEPC) was proposed as a future Higgs factory. To meet the physics requirements, a particle flow algorithm-oriented calorimeter system with high energy resolution and precise reconstruction is considered. A sampling calorimeter with scintillator-tungsten sandwich structure is selected as one of the electromagnetic calorimeter (ECAL) options due to its good performance and relatively low cost. We present the design, the test and the optimization of the scintillator module read out by silicon photomultiplier (SiPM), including the design and the development of the electronics. To estimate the performance of the scintillator and SiPM module for particles with different energy, the beam test of a mini detector prototype without tungsten shower material was performed at the E3 beams in Institute of High Energy Physics (IHEP). The results are consistent with the expectation. These studies provide a reference and promote the development of particle flow electromagnetic calorimeter for the CEPC.

High-Resolution Gamma-Ray Spectroscopy With a SiPM-Based Detection Module for 1” and 2” LaBr3:Ce Readout

In this paper, we present a silicon photomultiplier (SiPM)-based photodetector module designed to readout large cerium-doped lanthanum bromide (LaBr3:Ce) scintillators (cylindrical 1” $\times$ 1” and 2” $\times$ 2”) for nuclear physics experiments. The detector prototype has a modular structure and implements a real-time stabilization of the SiPM gain to compensate for the gain drift with temperature. The SiPM module consists of an array of 5 by 6 near-ultraviolet high-density SiPMs (Fondazione Bruno Kessler, Italy), each one having an active area of 6 mm $\times$ 6 mm and 30- $\mu \text{m}$ microcells. The single array is used for the 1” crystal readout, and it is assembled in a $2{\times} 2$ format to read the 2” scintillator. Spectroscopic measurements were performed with both crystals. The 2” crystal was irradiated with different radioactive sources in an energy range between 122 keV and 1.3 MeV, and an energy resolution of 3.19 ± 0.01% full-width at half-maximum (FWHM) has been achieved at 662 keV. The result is very close to the 3.07 ± 0.03% FWHM measured with Super Bialkali photomultiplier tube (PMT) (Hamamatsu R6233-100) at the same energy with the same 2” crystal. In the framework of the comparison between SiPM and PMT for LaBr3:Ce readout, we provide an analysis of the energy resolution contributions based on the measurements performed with the developed gamma-ray detection system.

Silicon photomultiplier modules for MRI-compatible PET

Silicon photomultiplier (SiPM) modules were developed for use in positron emission tomography-magnetic resonance imaging (PET-MRI), which is a hybrid medical imaging technology. A PET-MRI is very efficient in the early diagnosis of representative senile diseases, including cancer, Alzheimer's disease, and Parkinson's disease. SiPMs comprise the core image sensor for MR-compatible PET applications since they have a low operational voltage, high gain, good timing resolution, ruggedness, insensitivity to magnetic fields, compactness, and low cost. In PET systems, SiPM microcells can be optimized by making a trade-off between photon detection efficiency (PDE) and dynamic range. The SiPM modules used in this study were fabricated at the National NanoFab Center (NNFC) of South Korea by using a customized CMOS processes. The SiPM modules were evaluated by first packaging them with a cost-effective PCB package instead of with a conventional ceramic package. Measurements on 1,400 SiPMs indicated a uniform breakdown voltage of 20.54 V with a standard deviation of 0.07 V. Moreover, the SiPM modules present a high and uniform energy resolution of 13.6% with a standard deviation of 0.5% at 511 keV with 3 × 3 × 20 mm3 cerium-doped lutetium-yttrium oxyorthosilicate (Lu2(1−x)Y2xSiO5:Ce, LYSO) crystal coupling. These results indicated that the proposed devices offer adequate performance to form the foundation of an image sensor technology for MRI-compatible PET.

Initial results on SiPMs performance for use in medical imaging

Silicon photomultiplier (SiPMs) detectors are attractive candidates for replacing position sensitive photomultipliers in nuclear imaging. They are compact, they provide high gain with low bias voltage and show better response. The development of dedicated imaging prototypes based on SiPMs possesses several design challenges, since it is necessary to optimize scintillator and SiPM coupling, as well as signal amplification and digitization. In this work, we have investigated the performance of three SiPM modules constructed by SensL coupled on three scintillators (CsI:Tl, BGO, LYSO:Ce), which are used in SPECT and PET imaging. Irradiation was carried out using different sources, which covered a wide range of energies from 88 to 1275 keV. The parameters measured were output pulses' width and height, energy resolution and linearity as a function of bias voltage and sources energy.