We present a cost-effective, fully reconfigurable time-resolved single-photon detection system in which the active quenching circuit (AQC) is implemented using the tri-state gates of a field-programmable gate array (FTG-SPAD). By embedding the AQC within the FPGA, interfacing with discrete avalanche photodiodes (APDs), this design decouples the detector front end from the quenching and data processing circuits, enabling a rapid initialization of APDs into Geiger-mode single-photon detection. It has the advantages of firmware-level reconfigurability at fine temporal and spatial granularity, and flexibility to interchange APDs with different structures or operation wavelength for diverse applications. In addition to the quenching circuit, the FPGA back end implemented a time-to-digital converter (86.2 ps least significant bit), a 32-bit counter, and communication modules, forming a complete reconfigurable system for time-correlated single-photon counting. The FTG-SPAD with APDs of 23 µm diameter demonstrates a dark count rate of ∼12.2 cps at 3.2 V excess bias, a peak photon detection probability of 29.9% at 460 nm, and a single-photon time resolution of ∼234.6ps (FWHM) at 475 nm. These results verify that promising time-resolved single-photon detection can be achieved within this FPGA-based architecture, aiming to be a cost-effective, compact, flexible single-photon detection platform.

This study presents a high-performance photon counting detector (PCD) for photon-counting computed tomography (PCCT) applications, addressing the critical challenge of pulse pile-up at high X-ray photon fluxes. The PCD is composed of a fast Lu1.8Y0.2SiO5:Ce (LYSO) scintillator with an epitaxial quenching resistor type silicon photomultiplier (EQR SiPM), which features a small microcell pitch of 10 & micro;m, a small active area of 0.52 & times; 0.52 mm(2) and high fill factor of 49%. It exhibits a rapid recovery time of 1.85 ns and high photon detection efficiency (PDE) greater than 30%, thus is able to achieve a high photon counting rate while retaining adequate high energy resolution (ER). In order to further mitigate pile-up effects, a pole-zero cancellation (PZC) circuit was implemented to narrow pulse width from 46.1 ns to 19.5 ns (FWHM) along with a pileup recovery algorithm (PRA) for pileup pulse discrimination. Experimental results demonstrate an ER of 37.7%(FWHM) at 59.5 keV (Am-241, 24 kBq) and a maximum count rate (CR) of 102.7 Mcps/mm(2) under 80 kV X-ray irradiation. This CR was twice as high as that obtained without using PRA methods. These preliminary results indicate the feasibility of EQR-silicon photomultiplier (SiPM)-based scintillation PCDs in clinical PCCT. The results demonstrate the PRA method's efficacy in improving spectral performance under high flux conditions in a laboratory setting, though its clinical scalability remains challenging due to high computational demands.

The performance of 4 × 4 array of one-dimensional position sensitive SiPM, intrinsic continuous Cap Resistive Layer Silicon Photomultipliers, with each element in size of 6.14 × 6.14 mm 2 , and total area of 24.6 × 24.6 mm 2 is reported in this paper. By using a specular anode-cathode signal multiplexing configuration, the number of readout channels is greatly reduced from 32 to 4 while retaining adequate high space and time resolution simultaneously. Under condition of a mean photoelectron number around 130 and the reverse bias voltage of 32 V, the position measurement error was 54.8 ± 38.3 μm, which accounted for 0.2% of the length of the CRL SiPM array. The position resolution was 392.9 ± 58.3 μm, and the time resolution was 205.3 ± 22.3 ps. A 10 × 10 LYSO array, with each element of 0.52 × 0.52 × 20 mm 3 , was clearly resolved in 1D by utilizing the natural radioactive radiation of lutetium element.

Position sensitive silicon photomultipliers that utilize an intrinsic continuous resistive layer (CRL SiPMs) for charge division are reviewed, and new developments of one-dimensional (1D) CRL SiPMs are reported. This study compares and analyzes the position and timing characteristics of three 1D CRL SiPM configurations: square ring (SR) electrodes with microcell sizes of 15 μm and 20 μm, and a dual parallel side strip (DPSS) electrode with a 10 μm microcell size. The position resolution degrades as microcell size increases, whereas the position measurement error remains independent of microcell size. The larger measurement error observed in the 10 μm device is caused by reversed pulses rather than microcell size. At the mean photoelectron numbers of 230 for the 10 μm and 15 μm devices and 240 for the 20 μm device, the average position resolutions are 72.6 ± 13.6 μm, 128.7 ± 20.1 μm, and 196.2 ± 20.2 μm, position measurement errors are 79.8 ± 57.0 μm, 32.0 ± 24.0 μm, and 31.6 ± 26.4 μm, the time resolutions are 165.8 ± 111.2 ps, 96.0 ± 33.2 ps, and 198.0 ± 112.3 ps, respectively. Moreover, the SR structure exhibited better time resolution due to the shortest charge transmition path. Compared to the tetra lateral and SR structure 2D CRL SiPM, the orthogonal configuration of two 1D CRL SiPMs can eliminate electrode-induced barrel distortion in scintillation imaging detection, and acquire depth information of interaction (DOI). As a result, the 1D CRL SiPM with SR collection electrodes has an advantage for application in scintillation detection where high 3D space and timing resolution are needed.

The characteristics of one-dimensional (1D) position sensitive SiPM with an intrinsic continuous cap resistive layer (CRL) and its performance in acquiring two-dimensional (2D) radiation imaging are reported in this paper. The device, with an active size of 6.14 mm x 6.14 mm, demonstrated the position measurement error of 32.0 +/- 24.0 mu m without correction, which accounted for 0.5% of the length of the SiPM at a mean response photoelectron number around 230 and the reverse bias voltage of 40 V. Under the same condition, it demonstrated a position resolution of 128.7 +/- 20.1 mu m and a time resolution of 96.0 +/- 33.2 ps. A 3D scintillation detector for acquiring 2D radiation imaging with depth information of interaction (DOI) is proposed by implementing two 1D CRL SiPMs in a perpendicular orientation on the two ends of a scintillator. Using this configuration, the 2D imaging of a pixelated 10 x 10 lutetium yttrium orthosilicate (LYSO) array, with each element having a volume of 0.52 mm x 0.52 mm x 20 mm, was successfully resolved by utilizing the natural radioactive radiation of lutetium element in LYSO without distortions at the edges and corners.

Low-gain avalanche detectors (LGADs) are promising candidates for 4-D tracking detectors in future high-energy physics (HEP) experiments, offering high position and time resolution. However, conventional pixel array LGADs suffer from large dead areas between pixels and require a large number of readout channels, resulting in poor spatial resolution and high cost. In this article, we present a 1-D position-sensitive LGAD (1-D PS-LGAD) based on dc coupling and a resistive charge division mechanism. The 1-D PS-LGAD features two cathodes and one anode, with 2-D position coordinates obtained by cross-placing two 1-D PS-LGADs. With an active thickness of 50 $\mu \text{m}$ and an active area of $2.7\times2.7$ mm, a 1-D PS-LGAD demonstrated an average position measurement error (PME) of 32.2 ± 35.4 $\mu \text{m}$ , accounting for 1.2% of the side length of the active area with a 100% fill factor. The coincidence time resolution and position resolutions were 8.8 ps and 22.5 $\mu \text{m}$ , respectively, at the center of the device for incident 532 nm light with a spot diameter of approximately 25 $\mu \text{m}$ and a mean photoelectron number (MPEN) of 6000 when the reverse voltage was 620 V.

The performance of an active-quenching single-photon avalanche diode (SPAD) array that is based on the tri-state gates of a field programmable gate array (FPGA) is presented. The array is implemented by stacking a bare 4 × 4 N-on-P SPAD array on a bare FPGA die, and the electrodes of the SPAD pixels and the I/O ports of the FPGA are connected through wire bonding within the same package. The active quenching action on each SPAD pixel is performed by using the properties of the tri-state gates of the FPGA. Digital signal processing, such as pulse counters, data encoders, and command interactions, is also performed by using the same FPGA. The breakdown voltage of the SPAD pixels, with an active area of 60 μm × 60 μm, is 47.2–48.0 V. When the device is reverse biased at a voltage of ~50.4 V, a response delay of ~50 ns, a dead time of 157 ns, a dark count rate of 2.44 kHz, and an afterpulsing probability of 6.9% are obtained. Its peak photon detection probability (PDP) reaches 17.0% at a peak wavelength of 760 nm and remains above 10% at 900 nm. This hybrid integrated SPAD array is reconfigurable and cost effective.

Silicon photomultiplier (SiPM) is one of the best choices for Positron Emission Computed Tomography (PET) detectors due to its excellent properties. In order to achieve high fill factor of SiPM tile for PET detector, we have developed a small “dead zones” packaging technology based on lithography, SU-8 photoresist and conductive silver paste rather than Au wire bonding. It was simple, cost-effective to form a small “dead” zone as small as 60 µm of packaging SiPMs for mass production, the ratio of chip area to packaged device area is as high as 0.9037. The preliminary yield reached 49.8%.

北京师范大学新器件实验室（NDL）一直致力于研制结构紧凑、工艺相对简单的外延电阻淬灭型硅光电倍增器（silicon photomultiplier with epitaxial quenching resistor, EQR SiPM）。近期为了满足硅光电倍增器（silicon photomultiplier, SiPM）在核医学成像方面的需要，NDL通过优化器件设计和制作工艺，成功研制出微单元尺寸为15μm、有效面积为9 mm~2的EQR SiPM。相较以往同类型器件，实现了器件暗计数率（dark count rate, DCR）的进一步降低同时保持了较高的光子探测效率（photon detection efficiency, PDE），在环境温度为20℃、过偏压为7 V时，DCR的典型值为226 kHz/mm~2、峰值PDE为46%。另外，为了进一步提升EQR SiPM的动态范围，NDL还研制出微单元尺寸为6μm、有效面积为9 mm~2、微单元数目为244 720的EQR SiPM，在环境温度为20℃、过偏压为7 V时，DCR的典型值为240 kHz/mm~2、峰值PDE为28%，其较大的动态范围特别适合高能宇宙射线的测量、强子量能器等应用。

Conventional isothermal annealing is helpful to performance recovery of radiated silicon detector; but it is hard to be applied in vast well-installed detectors in high energy physics experiments. This summary investigated an in-situ annealing technique that employs joule heat of the intrinsic p-n junction to mitigate radiation damage effect on low gain avalanche detector (LGAD). The LGADs are 2 × 2 array with each pad of 1.3 mm × 1.3mm active area and were irradiated by 2 MeV proton to an equivalent fluence of 5×10 14 neq/cm 2 . After being applied a forward current of 1 A lasting for 27 s, which reached a peak annealing temperature around 180°C, the leakage current, the full depletion voltage and the gain of the radiated LGADs were restored partially. The leakage current was decreased about an order of magnitude, the full depletion voltage increased from 20 V to 85 V, and the gain increased from about 6 to 11 at 400 V. This simple in-situ annealing method is possible to implement during the service period of the detectors, thus prolongs their lifetime in harsh irradiation environment.

A two-dimensional (2D) square-bordered position-sensitive (PS) silicon photomultiplier (SiPM) toward distortion-free performance with high spatial resolution is reported in this letter. The device, based on SiPM technology of an epitaxial quenching resistor, contains a central cap resistive region enclosed by a narrow square-shaped metal ring contact located at the surface periphery. Four small output metal pads are connected to the metal ring at each corner to read out signal charges. With an active area of 6.14 mm x 6.14 mm, the PS-SiPM demonstrated an average position measurement error (PME) of 86.9 μm without correction, which accounted for 1.4% of the side length of the active area. The average position resolutions were demonstrated to be ~130.7 μm and ~135.6 μm in the X and Y directions, respectively, for incident light with a spot diameter of 80 μm and a mean photoelectron number (MPEN) of ~600. In addition, an intrinsic radioactive-light image of a pixelated 12 × 12 lutetium-yttrium oxyorthosilicate (LYSO) array with each element volume of 0.475 × 0.475 × 6 mm 3 was clearly resolved by the 2D square-bordered PS-SiPM.

An ultralow level light detection module, the time-correlated photon counter, is proposed and evaluated for fluorescence analysis. The time-correlated photon counter employs a silicon photomultiplier as a photon counting sensor in conjunction with a Poisson statistics algorithm and a double time windows technique, and therefore it can accurately count the photon number. The time-correlated photon counter is compatible with the time-correlated single photon counting technique and can record the arrival time of very faint light signals. This low-cost and compact instrument was used to analyze the intensity and lifetime of fluorescein isothiocyanate; a limit of detection of 16 pg/ml with a large linear dynamic range from 2.86 pg/ml to 0.5 µg/ml was obtained, and the lifetime of fluorescein isothiocyanate was measured to be 3.758 ns, which agrees well with the results of a sophisticated commercial fluorescence analysis instrument. The time-correlated photon counter may be useful in applications such as point-of-care testing.

本研究运用质性研究方法,对北京、 上海共11位普通学校教师进行访谈来深入了解教师对融合教育的理解与践行.结果表明,多数教师对融合教育的态度仍不容乐观,将形式化的调整视为教学过程中最大程度的改变,最终在实践层面形构出一种"象征性"的融合教育制度.结合社会学新制度主义理论分析发现:教师在以追求效率为特征的学校内生性制度逻辑的长期浸润下,发展出包括身份图式、 应试图式以及缺陷模式特殊学生观在内的一套共享"文化—认知"图式,从而在"文化—认知"层面解构了融合教育的合法性基础,也使学校和教师倾向于采取"政策—实践"松散耦合策略应对融合教育制度.

外延电阻淬灭型硅光电倍增器(EQR SiPM)的特点是利用硅衬底外延层来制作器件淬灭电阻.为了进一步提高大动态范围EQR SiPM的光子探测效率,并且解决填充因子较低和增益较小等问题,在前期研究工作的基础上研制出微单元尺寸分别为15μm和7μm的EQR SiPM,有源区面积均是1 mm×1 mm.通过改变EQR SiPM的微单元尺寸优化填充因子,有效提高了探测效率与增益;其微单元密度分别是4400个/mm2和23200个/mm2,依然保持着较大的动态范围.室温条件下(20℃),工作在5 V过偏压的EQR SiPM至少可分辨13个光电子;15μm和7μm EQR SiPM的增益分别为5.1×105和1.1×105,在400 nm波长下的峰值光探测效率分别达到40％ 和34％.

采用混合研究方法中的并行三角互补策略来收集数据,通过调查云南与甘肃两省特教教师专业发展现状、分析教师教学工作中面临的困难以确定培训需求,并据此管窥当前两省特教教师专业发展的特征及面临的困难.结果 发现,云南、甘肃两省特教教师专业化水平不高,理论转化为实践的能力有限;在实际教学中面临着“不知道教什么”“不知道怎么教”“教起来很棘手”等困难;教师们喜欢与教学实践联系密切的培训内容,偏爱见效快、周期短、实践性强的培训形式.进一步分析发现,特教教师在专业发展路径上偏重技术理性的路线,专业发展内容偏重显性的特定专业技能和方法,忽视隐性的基于研究的实践能力和反思能力的培养.由此也揭示了当前特教教师专业发展建立准入及培养的制度迫切性.

Recently, the recovery of SiPM after radiation damage was tentatively promoted by thermal annealing with an external heat source. However, it is hard for practical applications for some specific experiments in high energy physics and space science since the vast well-installed detectors is impossible to be dismantled from a large experiment facility and implement the annealing process with a hot plate or an oven. In this paper, we present a technique of in-situ annealing and temperature monitoring for SiPMs in detail, which may provide a solution to recover the radiation damaged SiPMs and prolong the lifetime of the detectors. By applying a reverse current, the SiPM can be heated and annealed by a Joule effect; while the annealing temperature can be monitored by employing the PN junction of the same SiPM as a temperature sensor. This method may be extended to other semiconductor detectors based on PN junction, and prolong the lifetime of the detectors in a large experiment.

We proposed to design and fabricate a new Low Gain Avalanche Detector (LGAD) which can be used to replace the detector used in the high luminosity upgrade of the CERN Large Hadron Collider and synchrotron radiation detection. In this paper, we describe a 2×2 pads array Low Gain Avalanche Detector (LGAD) produced on epitaxial silicon with 33 μm thickness on a 250 μm thick support silicon wafer. The Low Gain Avalanche Detector (LGAD) has two guard rings. One is float guard ring (G-ring) without voltage which surrounds the whole 2×2 pads array, the other is collector ring (C-ring) surrounding each pad which has same voltage with active region. C-ring can reduce surface leakage current and the bulk current that can enhance signal to noise and radiation hardness. With C-ring biased, the data of the gain and responsivity were more accurate. The gain varied between 1 and 100 depending on the sensor bias voltage and responsivity was 4.9 A/W at 800nm when the gain was about 8. The time resolution was about 30ps at bias voltage of 220V.

In this paper, we present the feasibility of high-resolution PET detector readout by a 2-D tetra-lateral position-sensitive Silicon photomultiplier with an intrinsic cap resistive layer for charge division (CRL-SiPM). The scintillation imaging sensor for 511 keV gamma ray detection is realized by coupling a 5 $\times $ 5 array of 0.45 $\times $ 0.45 $ \times $ 6 mm3 LYSO crystals to the CRL-SiPM with an active area of 2.77 $ \times $ 2.77 mm2 and micro APD cell pitch of $ \sim 10~ \mu \text{m}$ . The scintillator arrays are clearly distinguished and good scintillator array imaging with little position distortion has been achieved. An energy resolution of ~13.5% and coincidence time resolution of 555 ps are demonstrated, respectively. Therefore, the potential PET imaging sensor with greatly reduced readout channels has been verified.

A two-dimensional tetra-lateral position-sensitive cap-resistive-layer silicon photomultiplier (CRL-SiPM) is employed as a single-photon imaging sensor at room temperature. The CRL-SiPM has only four anodes and one back cathode with an active area of 2.77 mm × 2.77 mm and a micro avalanche photodiode cell pitch of ~10 μm. It achieved a 150 μm-linewidth-resolved single-photon image, which is near the device's theoretical intrinsic single-photon position resolution limit of ~115 μm. With increasing light intensity, the position resolution of the device improved. When the mean photoelectron numbers were 1.34 and 41.56, the corresponding intrinsic position resolutions were 101.6 and 14.08 μm, respectively. Finally, owing to the single photoelectron imaging capability of the CRL-SiPM, we achieved the lensless imaging of dark counting sites, i.e., the locations of thermal carriers inducing avalanche breakdown of the device.