Effect of multiple coulomb scattering on the beam tests of silicon pixel detectors

In the research and development of new silicon pixel detectors,a collimated monoenergetic charged-particle test beam equipped with a high-resolution pixel-beam telescope is crucial for prototype verification and performance evaluation.When the beam energy is low,the effect of multiple Coulomb scattering on the measured resolution of the Device Under Test(DUT)must be considered to accurately evaluate the performance of the pixel chips and detectors.This study aimed to investigate the effect of multiple Coulomb scattering on the measured resolution,particularly at low beam energies.Simulations were conducted using Allpix^(2) to study the effects of multiple Coulomb scattering under different beam energies,material budgets,and telescope layouts.The simulations also provided the minimum energy at which the effect of multiple Coulomb scattering could be ignored.Compared with the results of a five-layer detector system tested with an electron beam at DESY,the simulation results were consistent with the beam test results,confirming the reliability of the simulations.

Design of a wafer-scale ultra-thin silicon pixel detector prototype

Purpose In the upgrade study of the BESII inner drift chamber,a two-layer concentric cylindrical silicon pixel detector is proposed,which will be positioned between the beam pipe and the inner drift chamber.Method The detector consists of CMOS pixel sensors at wafer scale using chip stitching technology.The chips are thinned to a flexible thickness of about 50μm.PMI foams are used as spacers and auxiliary support between the adjacent layers,enabling the first layer of the detector to be put as close to the central beam pipe as possible.The detector structure has been optimized through finite-element analysis(FEA).Result The material budget of the detector has been reduced to about 0.077%Xo per layer.The maximum deformation of the chip edge has been controlled to±80μm after bending,and the roundness is about 100μm,which verifies the feasibility of the cylindrical detector prototype structure.In addition,the wire bonding process for the cylindrical silicon pixel detector has been tested and preliminarily validated.Conclusion This study validates the process flow for the development of large-area cylindrical detectors based on stitching technology,laying a foundation for the smooth progress of subsequent study.

FPGA-based 10G/40G Ethernet Firmware for Pixel Detector in SHINE

Background Shanghai HIgh repetition rate XFEL aNd Extreme light facility(SHINE)is a free electron laser facility,which will provide research methods such as high-resolution imaging for many disciplines.The pixel detector,which is in the pre-research stage,is one of most important components of the facility.Purpose The current target data rate of the pixel detector in SHINE is about 100 GB/s.Considering the high data rate,the 10G/40G Ethernet firmware for pixel detector in SHINE was developed on field programmable gate array(FPGA),which will lead to more integrated electronic design and make the system smaller.Methods The firmware converts the media independent interfaces(MII)of 10G and 40G Ethernet to each other and uses a polling method to process data from four 10G Ethernet channels.Based on the above methods,the firmware can merge four 10G Ethernet channels into one 40G Ethernet channel.Results and Conclusion The firmware successfully transmits data between the data source and the server.The bandwidth of the firmware is 36.66 Gbps when the computer equipped with 10G network interface controller(NIC)is set as the data source.Through joint test with the 1G/10G hub and SiTCP,the bandwidth of firmware is 36.3 Gbps.And 40 SiTCP nodes whose system clock frequency can exceed 125 MHz can be used as the data source of the firmware,which will provide a variety of technical solutions for pixel detector.

Test of a fine pitch SOI pixel detector with laser beam

A silicon pixel detector with fine pitch size of 19 μm × 19 μm, developed based on SOI （silicon-on- insulator） technology, was tested under the illumination of infrared laser pulses. As an alternative method for particle beam tests, the laser pulses were tuned to very short duration and small transverse profile to sinmlate the tracks of MIPs （minimum ionization particles） in silicon. Hit cluster sizes were measured with focused laser pulses propagating through the SOI detector perpendicular to its surface and most of the induced charge was found to be collected inside the seed pixel. For the first time, the signal amplitude as a function of the applied bias voltage was measured for this SOI detector, deepening understanding of its depletion characteristics.

Development of small pixel HgCdTe infrared detectors

After approximately half a century of development, HgCdTe infrared detectors have become the first choice for high performance infrared detectors, which are widely used in various industry sectors, including military tracking, military reconnaissance, infrared guidance, infrared warning, weather forecasting, and resource detection. Further development in infrared applications requires future HgCdTe infrared detectors to exhibit features such as larger focal plane array format and thus higher imaging resolution. An effective approach to develop HgCdTe infrared detectors with a larger array format size is to develop the small pixel technology. In this article, we present a review on the developmental history and current status of small pixel technology for HgCdTe infrared detectors, as well as the main challenges and potential solutions in developing this technology. It is predicted that the pixel size of long-wave HgCdTe infrared detectors can be reduced to5 μm, while that of mid-wave HgCdTe infrared detectors can be reduced to 3 μm. Although significant progress has been made in this area, the development of small pixel technology for HgCdTe infrared detectors still faces significant challenges such as flip-chip bonding, interconnection, and charge processing capacity of readout circuits. Various approaches have been proposed to address these challenges, including three-dimensional stacking integration and readout circuits based on microelectromechanical systems.

Hi'CT:a pixel sensor-based device for ion tomography

Carbon ions,commonly referred to as particle therapy,have become increasingly popular in the last decade.Accurately predicting the range of ions in tissues is important for the precise delivery of doses in heavy-ion radiotherapy.Range uncertainty is currently the largest contributor to dose uncertainty in normal tissues,leading to the use of safety margins in treatment planning.One potential method is the direct relative stopping measurement(RSP)with ions.Heavy-ion CT(Hi′CT),a compact segmented full digital tomography detector using monolithic active pixel sensors,was designed and evaluated using a 430 MeV/u high-energy carbon ion pencil beam in Geant4.The precise position of the individual carbon ion track can be recorded and reconstructed using a 30μm×30μm small pixel pitch size.Two types of customized image reconstruction algorithms were developed,and their performances were evaluated using three different modules of CAT-PHAN 600-series phantoms.The RSP measurement accuracy of the tracking algorithm for different types of materials in the CTP404 module was less than 1%.In terms of spatial resolution,the tracking algorithm could achieve a 20%modulation transfer function normalization value of CTP528 imaging results at 5 lp/cm,which is significantly better than that of the fast imaging algorithm(3 lp/cm).The density resolution obtained using the tracking algorithm of the customized CTP515 was approximately 10.5%.In conclusion,a compact digital Hi'CT system was designed,and its nominal performance was evaluated in a simulation.The RSP resolution and image quality provide potential feasibility for scanning most parts of an adult body or pediatric patient,particularly for head and neck tumor treatment.

Electronics system for the cosmic X-ray polarization detector

This study presents an electronics system for cosmic X-ray polarization detection(CXPD).The CXPD was designed as a high-sensitivity soft X-ray polarimeter with a measurement energy range of 2-10 keV carried by a CubeSat.A stable and functionally complete electronics system under power and space constraints is a key challenge.The complete CXPD electronics system(CXPDES)comprises hardware and firmware.CXPDES adopts a three-layer electronic board structure based on functionality and available space.Two gas pixel detectors(GPDs)were placed on the top layer board,and CXPDES provided the GPDs with voltages up to-4000 V.Each GPD signal was digitized,compressed,encoded,and stored before being transmitted to the ground.The CXPDES provided stable and high-speed communication based on a scheme that separated command and data transmission,and it supports the CXPDES in-orbit upgrade.In addition,environmental monitors,silicon photomultiplier(SiPM)triggers,power management,GPDs configuration,and mode switches were included in the overall operating logic of the CXPDES.The results obtained by testing the CXPDES showed that it satisfied all the requirements of CXPD.The CXPDES provides design experience and technological readiness for future large-area X-ray polarimetry missions.

硅像素探测器X射线探测效率实验研究

X射线探测器经历了气体探测器和闪烁体探测器时代,进入了半导体探测器时代。作为一种新型的半导体探测器,硅像素探测器具有分辨率好、探测效率高、时间响应快、功耗低等特点。为了研究硅像素探测器X射线探测效率,设计了一套X射线探测系统,并进行了实验研究。实验分别测试了4.51、5.41、6.40、8.05 keV共4种不同能量的X射线的探测效率。后期进行了误差分析和数据处理,得到4种不同能量X射线正面入射时探测效率分别为53.00%、51.56%、40.65%和29.91%。该实验研究为寻找高探测效率的X射线探测器提供了一种新的思路。

2000~2020年锡林郭勒草原植被覆盖时空动态变化及影响因素分析

锡林郭勒盟生态地位十分重要,因此定量分析其植被覆盖度时空分布变化特征及驱动因素具有重要意义。本研究首先针对草原植被结构特征,基于优化的多角度像元二分模型构建了锡林郭勒草原2000~2020年植被覆盖度数据集,然后分析了覆盖度的时空变化特征,最后利用地理探测器研究了植被覆盖度变化的影响因素。结果表明:(1)2000~2020年锡林郭勒草原植被覆盖度呈“东高西低”的分布格局,不同生态功能区覆盖度差异较大,覆盖度主要集中在0.2~0.6;不同生态亚区植被覆盖度变化趋势基本一致,呈现波动增长趋势。(2)锡林郭勒草原不同生态功能区植被覆盖度变化差异明显,整体呈上升趋势,显著上升区为11.99%,主要分布在大兴安岭南部落森林草原生态亚区南部,锡林郭勒典型草原生态亚区北部和西部,阴山山地落叶灌丛-草原生态亚区的东部和内蒙古高原荒漠草原生态亚区中部和东南部;14.21%的像元覆盖度显著下降,集中分布在大兴安岭南部落森林草原生态亚区北部、锡林郭勒典型草原生态亚区中部条带状区域和南部以及坝上高原草原与农业生态亚区,需要重点关注。(3)湿润程度是锡林郭勒草原植被覆盖度变化的主要驱动因素,降水的影响力次之,两者与覆盖度均为正相关关系,且湿润指数对中等覆盖度区域影响力较大;气温对覆盖度的驱动力最小,两者为负相关关系。该研究期望为锡林郭勒草原生态保护与合理利用提供科学支撑。

基于JavaFx的硅像素顶点探测器原型机数据获取软件的研制

在环形正负电子对撞机(CEPC)实验中,硅像素顶点探测器对空间位置分辨率有着极高的要求,这使得其芯片和探测器设计面临巨大挑战。太初系列硅像素探测器芯片(TaichuPix)是基于CMOS技术的一种重要尝试,其首款工程批芯片被应用于开发第一个全尺寸顶点探测器原型机。为满足顶点探测器原型机在实验中的特定需求,设计并实现了一套基于JavaFx框架的跨平台数据获取系统。该系统能够高效地进行探测器原型机的配置、数据采集、在线数据校验和实时监测,同时提供了一个用户友好的图形化界面。在实验室环境及德国电子同步加速器研究所(DESY)的束流实验中,数据获取系统的功能完善性和运行稳定性得到了验证,充分满足了硅像素顶点探测器原型机的实验需求。

基于带隙基准的改进型像元共享CTIA红外读出电路设计

为了提高红外读出电路动态范围、增强红外成像质量,加入暗电流抑制模块电路,设计了一种四像元分时共享的电容反馈跨阻放大器(CTIA)和带隙基准源相互配合的高性能红外读出电路。通过带隙基准源产生两个基准电压586 mV和293 mV,其中293 mV基准电压值的温漂系数达到1.49×10-6/℃,可对分流管的栅极和源极提供稳定的电压偏置,实现对暗电流的精准撇除。结果表明,该电路可实现电流信号从10 pA~10 nA宽动态范围的积分电压读出,读出数据通过线性拟合,拟合优度R 2达到0.9992,说明电路性能良好。此研究未来可应用到线列和面阵的红外探测器中。

红外焦平面探测器复合条件工作点闪元标定方法

针对闪元传统标定方法的不足,提出一种结合灰度域图像和能量域图像进行复合条件工作点闪元标定的方法。该方法解决了单一工作点对闪元激发条件不够充分和探测器非均匀性所造成的闪元漏检等问题。实验验证表明,单一工作点上闪元检测率平均提高了12.49%,与传统方法相比,整体闪元检测率提高了9.41%。本文所提方法有效提高了闪元的检出率。

基于像素化芯片的质子透射成像模拟研究

利用高能质子对病灶区域进行成像,直接获得病灶区域对质子的阻止能力,对于减小质子治疗中射程不确定度具有重要意义。作为质子CT的基本功能,透射成像对于辅助摆位具有重要意义。本研究在Geant4程序中设计并构建基于有源阵像素CMOS芯片的紧凑型质子CT探测器,并利用180 MeV质子对该系统的透射成像能力进行评估。通过径迹角度进行精确重建,对CTP404、CTP528以及自定义材料的CTP515模块进行模拟,获得空间、密度分辨力,以及质子相对阻止能力RSP的模拟结果。结果显示选用2°质子偏转角截断值时图像信噪比得到提升,使用CTP528模块测算的空间分辨力为3~4 lp/cm;使用CTP404模块测算密度分辨力优于0.05 g/cm^(3),RSP分辨力在5%以内;通过对选定材料的CTP515模块进行成像,表明该系统具备用于人体常见组织成像的潜力。

短波红外星图的噪声抑制算法

为了满足星敏感器在近地空间全天时观测的需求,基于短波红外探测器的星敏感器得到了广泛的应用。然而,短波红外星图中存在着条纹非均匀性噪声和缺陷像素等噪点,这些噪声的存在会降低星图的质量。为了抑制上述噪声的影响,本文针对短波红外星图提出了一种噪声抑制算法。首先,通过两点法对每列像素做初步的非均匀性校正,降低同列像素间的非均匀度。然后,通过改进的列向Top-hat算法去除条纹非均匀性噪声的影响。最后,通过中心点扩散连通域算法提取星点。实验结果表明,在两等星内,本文算法能够很好地去除噪声影响,星点的提取误差能够保持在0.3像素即2"内,并且算法针对单帧图像,便于实现,能够满足实时处理的要求。

四川秦巴山区植被覆盖变化及其影响因素分析

四川秦巴山区是重要的生态与水源涵养保护地,区内植被覆盖水平高,但生态环境脆弱且复杂,明确该区域植被覆盖变化情况及其影响因素,有利于为区域生态保护和植被恢复提供科学依据,为维持区域生态安全提供保障。基于MODIS-NDVI数据,利用像元二分法估算四川秦巴山区2001~2020年植被覆盖度,通过线性趋势法、Hurst指数、重心迁移模型、最优参数地理探测器等方法分析其时空变化、景观格局及影响因素。结果如下:(1)2001~2020年,四川秦巴山区植被覆盖度以+0.0071/a的速率稳步增长,多年平均植被覆盖度为0.6912;除研究区西部外,整体植被覆盖为北高南低,各等级植被覆盖重心均集中嘉陵江中游流域及其附近,未来植被覆盖趋势主要为持续增加和由增加变为减少;(2)20年间,区域植被覆盖总体景观格局破碎度减小,聚集度增强,中低、中等植被覆盖区域向高植被覆盖区域转变,高植被覆盖成为主要植被覆盖类型;(3)由最优参数地理探测器,四川秦巴山区影响因素最佳研究尺度为5 km,高程、气温与人口密度是该区域植被覆盖变化主要影响因素。

摄像机标定中亚像素级角点检测算法

针对摄像机标定模板图像的角点检测问题,提出了两种简便而有效的亚像素级精度的提取算法。先用传统的Harris算子检测出像素级的角点坐标,然后再求取亚像素级角点坐标。一种方法是用二次多项式去逼近周围3×3领域内的角点反应函数,用线性解法求得亚像素级角点坐标;另一种方法是从亚像素角点到周围像素点的矢量应垂直于图像的灰度梯度这个观察事实得到的,通过最小化误差函数的迭代方法来获得亚像素级精度的坐标值。文中提出的亚像素级角点检测方法定位精度高,摄像机标定试验中,得到的重投影平均偏差小于0.15个像素。

赋形像元探测器在超分辨重建中的应用

大多数光电成像系统的空间分辨率都与探测器的元数密切相关,增加探测器的元数是提高成像系统空间分辨率的核心问题之一。在不增加探测器元数的前提下,提高空间分辨率的技术途径之一就是超分辨重建技术,它通过增加探测器采样频率来提高探测器的空间分辨率。考虑到探测器的空间分辨率并不完全取决于采样作用,且受像元孔径效应的影响,提出了一种赋形像元探测器。基于巴比涅原理中的互补屏原则,将原有的红外探测器中的每个正矩形像元去掉1/4,用剩余部分来等效获取去掉部分的高截止频率;同时利用两列赋形像元探测器进行亚像元推扫,结合像元细分算法,实现超分辨重建。通过同时提高系统采样频率和探测器的截止频率来实现红外系统最终的高分辨率重建成像。

CdZnTe像素探测器的制备与表征

本文采用CdZnTe单晶制成像素探测器,并对其能谱响应特性及均匀性进行了系统表征。通过I-V和能谱响应测试,测定了晶体的电阻率和载流子迁移率与寿命的积,并用红外透过显微成像观察了晶体内Te夹杂的分布特性。采用光刻、剥离和真空蒸镀技术,在CdZnTe晶片上制备了8×8的像素电极,用丝网印刷和贴片技术通过导电银胶实现像素电极与读出电路的准确连接,制备出CdZnTe像素探测器。对像素探测器的测试表明,-300V下单像素最大漏电流小于0.7nA,对241 Am 59.5keV的能量分辨率可达5.6%,优于平面探测器。进一步分析了晶体内Te夹杂等缺陷对探测器漏电流和能谱响应特性的影响规律,结果表明,Te夹杂的聚集会显著增加漏电流,并降低探测器的能量分辨率。

小像元碲镉汞红外焦平面探测器的研究进展

随着红外技术的发展,探测器的尺寸、重量和功耗(SWaP)的减小已成为研究热点。像元尺寸的减小,一方面可以提高器件的分辨率,另一方面可以减小整个探测器系统的体积、重量和功耗,进而大大节约成本。因此,像元尺寸的减小成了研究的重点。本文介绍了小像元红外焦平面器件的技术难点,分别从系统的调制传递函数(Modulation Transfer Function,MTF)、噪声等效温差(Noise Equivalent Temperature Difference,NETD)、像元结构和像元集成互连方面进行了讨论。此外,介绍了国外像元中心距为12μm、10μm、8μm和5μm的HgCdTe红外焦平面探测器的研究进展。

288×4红外TDI探测器光敏元尺寸与间距设计研究

针对国外进口Sofradir公司长波288×4扫描型时间延迟积分(TDI)探测器,通过分析其沿扫描和沿线列方向上光敏元尺寸和间距对整个成像系统的系统调制传递函数(MTF)的影响,给出了探测器光敏元尺寸和间距与整个成像系统分辨率之间的相互关系,为新型TDI型探测器阵列光敏元排列设计提供了理论参考。