An FPGA-Based Pulse Pile-up Rejection Technique for Photon Counting Imaging Detectors

A novel FPGA-based pulse pile-up rejection method for single photon imaging detectors is reported. Tile method is easy to implement in FPGAs for real-time data processing. The rejection principle and entire design are introduced in detail. The photon counting imaging detector comprises a micro-channel plate （MCP） stack, and a wedge and strip anode （WSA）. The resolution mask pattern in front of the MCP can be reconstructed after data processing in the FPGA. For high count rates, the rejection design can effectively reduce the impact of the pulse pile-up on the image. The resolution can reach up to 140μm. The pulse pile-up rejection design can also be applied to high-energy physics and particle detection.

Subnanosecond current mode detectors for prompt physical process diagnosis

For prompt physical diagnosis, several types of subnanosecond current mode detectors have been developed, including scintillator detectors with large linear output current, GaAs:Cr and InP:Fe photoconductor detectors(PCD), and X-ray diodes(XRD), etc. The characteristic of scintillation light of BaF2 crystal doped with La and of plastic scintillator ST1422 with slow component quencher are described. As for the photoconductor detectors, the main performance of neutron damaged GaAs:Cr and InP:Fe were studied. In addition, the spectral response of an XRD with coaxial leading-out end was also studied. These detectors have been successfully applied to nuclear test diagnosis and ICF research.

Preliminary results of a Compton camera based on a single 3D position-sensitive CZT detector

A Compton camera prototype has been developed using a pixelated CZT detector with 4-by-4 pixels.Signals of the detector are read out by a VASTAT ASIC that is controlled by a self-developed DAQ board. The DAQ software is developed using LabVIEW, and the offline Compton imaging codes are written in C++. The prototype has been successfully calibrated, and its capabilities for source detection, spectroscopy, and Compton imaging have been demonstrated using a Cs-137 source.The angular resolution of the 662 keV line is 36° FWHM for the simple back-projection method and 9.6° FWHM for the MLEM reconstruction method. The system is ready to be extended to 11-by-11 pixels in the future, and a better imaging quality can be expected due to the better relative position resolution.

Optical fiber positioning based on four-quadrant detector with Gaussian fitting method

With the development of large-scale spectral surveys, fiber positioning technology has been developing rapidly. Because of the performance advantages of a four-quadrant（4Q） detector, a fiber positioning and real-time monitoring system based on the 4Q detector is proposed. The detection accuracy of this system is directly determined by the precision of the center of the spot. A Gaussian fitting algorithm based on the 4Q detector is studied and applied in the fiber positioning process to improve the calculated accuracy of the spot center. The relationship between the center position of the incident spot and the detector output signal is deduced. An experimental platform is built to complete the simulated experiment. Then we use the Gaussian fitting method to process experimental data, compare the fitting value with the theoretical one and calculate the corresponding error.

Determination of Alpha Particles Concentration in Toothpaste Using CR-39 Track Detector

The present study focuses on determination of alpha particles concentration in different samples of toothpaste by using nuclear track detector (CR-39). Nine samples of toothpaste have been collected from local Iraqi markets in Babylon Province. These samples have been chosen according to their most commonly use in Babylon Province. The samples were kept with CR-39 detector for six weeks period and then etched by 6.25 N of NaOH solution at temperature of 60°C for 5 hours. The results of the present work show that Sample 3 (Frosty) found to have a high alpha concentration about four times compared with Sample 4 (Aquafresh) and about 2 - 3 times compared with other samples.

32×32 Si盖革模式激光焦平面探测器

为了满足350 nm~1100 nm波长范围内远距离及微弱激光3维成像探测的需求,提出了一种规模为32×32的盖革模式硅激光焦平面阵列探测器,它主要由硅雪崩光电二极管阵列、读出电路芯片、微透镜阵列、半导体制冷器、引脚网格阵列壳体等元件组成。硅雪崩光电二极管焦平面阵列采用拉通型N^(+)-Π_(1)-P^(-)-Π_(2)-P^(+)结构,工作在盖革模式下,通过Si片背面抛磨减薄及盲孔刻蚀技术,实现了纤薄光敏区的加工;读出电路采用主动模式淬灭设计,使电路单元的死时间控制在50 ns以内,并利用一种带相移技术的时间数字转换电路优化方案,在满足时间分辨率不大于2 ns的同时,降低了读出电路芯片的功耗。结果表明,在反向过偏电压14 V、工作温度-40℃的条件下,该探测器在850 nm的目标波长可实现20.7%的平均光子探测效率与0.59 kHz的平均暗计数率,时间分辨率为1 ns,有效像元率优于97%。该研究为纤薄型背进光Si基激光焦平面探测器的研制提供了参考。

Development of a Front End Array for Broadband Phased Array Receiver

The receiver is a signal receiving device placed at the focus of the telescope.In order to improve the observation efficiency,the concept of phased array receiver has been proposed in recent years,which places a small phased array at the focal plane of the reflector,and flexible pattern and beam scanning functions can be achieved through a beamforming network.If combined with the element multiplexing,all beams within the entire field of view can be observed simultaneously to achieve continuous sky coverage.This article focuses on the front-end array of phased array receiver at 0.7-1.8 GHz for QiTai Telescope,and designs a Vivaldi antenna array of PCB structure with dual line polarization.Each polarization antenna is designed to arrange in a rectangle manner by 11×10.Based on the simulation results of the focal field,32,18,and eight elements were selected to form one beam at 0.7,1.25,and1.8 GHz.An analog beamforming network was constructed,and the measured gains of axial beam under uniform weighting were 19.32,13.72,and 15.22 dBi.Combining the beam scanning method of reflector antenna,the pattern test of different position element sets required for PAF beam scanning was carried out under independent array.The pattern optimization at 1.25 GHz was carried out by weighting method of conjugate field matching.Compared with uniform weighting,the gain,sidelobe level,and main beam direction under conjugate field matching have been improved.Although the above test and simulation results are slightly different,which is related to the passive array and laboratory testing condition,the relevant work has accumulated experience in the development of the front-end array for the phased array receiver,and has good guiding significance for future performance verification after the array is installed on the telescope.

光谱CT钙抑制成像技术在鼻窦炎评估中的应用

目的探索双层探测器光谱CT的钙抑制(CaSupp)技术在鼻窦炎评估中的有效性和准确性,为鼻窦炎的临床诊断提供新的工具。方法回顾性收集2019年3月~2023年9月就诊于解放军总医院海南医院的鼻窦炎患者30例,患者在1周内行鼻窦光谱CT和MRI检查,30例患者6组鼻窦[上颌窦(左、右)、筛窦(左、右)、蝶窦、额窦],共纳入174个鼻窦。根据患者所行检查技术,将患者分为钙抑制组和MRI组;CaSupp组根据其钙抑制指数分为40、50、60钙抑制组,并对CaSupp图像和MRI图像进行定性诊断和定量分析。基于CaSupp图像及MRI图像对鼻窦炎进行定性诊断,并采用卡方检验进行一致性检验。基于不同的钙抑制图像和MR图像对同一患者相同部位的鼻窦黏膜厚度进行测量,采用Pearson法及组内相关系数进行可靠性检验。结果CaSupp图像显示阳性鼻窦(有炎症的鼻窦)151个,阴性鼻窦(无炎症的鼻窦)23个;MRI图像显示阳性鼻窦155个,阴性鼻窦19个;CaSupp图像与MRI图像对鼻窦炎的诊断差异无统计学意义(P>0.05)。CaSupp指数为40、50、60钙抑制组对鼻黏膜厚度的测量结果与MRI组具有相关性(P<0.001);组内相关系数分析证实其组内相关系数系数分别为0.947、0.847及0.920。结论双层探测器光谱CT钙抑制技术对鼻窦炎的定性诊断和定量分析具有较高价值,且CaSupp指数为40时钙抑制图像在定量分析上与MRI图像的相关性最高。基于光谱CT的钙抑制技术为鼻窦炎的临床诊断及评估提供一种简单、有效的新方法。

地下管线探测方法的应用研究

随着城市化不断推进,各地城区扩张和改造的进程日益加快,完整的地下管线信息是工程顺利开展的必要条件。当前地下管线具有种类多、交错铺设、权属复杂等特点,寻找一套快速有效的地下管线探测方法,成为当今城市建设中需要解决的重要问题。介绍了地下管线的特点,研究了探测不同种类管线的方法,对不同工况下的探测方法和注意事项进行了总结。地下管线探测方法的研究具有巨大的社会价值和应用前景。

大口径离轴非球面镜预应力环抛方法研究

提出了一种加工离轴非球面的预应力环抛方法,基于预应力加工方法的基本原理,利用环抛机来磨制离轴非球面.设计了一套专门的加载装置,将拼接镜面中具有不同离轴量的非球面子镜转化成曲率半径相同的球面子镜进行磨制,可以在同一台环抛机上进行抛光.利用这种方法,花费连续40 h的时间,磨制了一块按照中国30 m极大口径望远镜(CFGT)主镜参数比例缩小的离轴抛物面,顶点曲率半径21.6 m,离轴量3.6 m,离轴口径为330 mm,最大非球面度为16μm.试验表明该方法效率高,适用于批量加工,特别是极大口径天文望远镜拼接主镜的大批量非球面子镜研制.

LBIC技术研究InGaAs线列探测器串音及光敏感区

利用激光诱导电流技术研究了InGaAs台面探测器的相邻探测器间的串音和光敏感区。用分子束外延方法生长掺杂InGaAs的PIN InP/InGaAs/InP外延材料,制备了256×1正照射台面InGaAs线列探测器。测试结果表明,InGaAs线列探测器相邻探测器间没有串音,虽然台面结构周围吸收层已被腐蚀,但因为少数载流子的侧向收集,扩大了有效光敏感区。

基于数字平板探测器的高能X射线成像实验研究

为了将数字平板探测器应用到高能X射线成像无损检测,通过实验研究了平板探测器的噪声和动态范围。设计了基于平板探测器的高能X射线成像系统。通过实验研究了电子直线加速器对数字平板探测器图像采集的束流触发同步问题。

月球伽玛射线谱仪的研制及其性能

介绍将用于中国第一颗月球探测卫星主载荷之一的伽玛射线谱仪的结构设计, Monte Carlo模拟结果和原理样机性能测试结果等．该探测器采用CsI(T1)晶体作为闪烁体和反符合技术抑制本底,可探测的射线能量范围为0．3-9．0 MeV,仪器能量分辨率是9．0％(662 keV)．

量热阵列式激光束能量分布测量系统研制

为了实现对高能密度激光束分布的测量,提出了高占空比蜂窝阵列结合分立隔热式能量探头的设计思想,研制出了一种耐激光辐照能力强、测量稳定的激光参数测量系统,该系统主要由蜂窝状阵列板、多路量热探头、多通道高速数据采集单元和相应数据处理软件组成。测量系统空间占空比为62%,光强分布测量不均匀性优于5%,测量动态范围达600倍,总能量测量不确定度优于8.5%。量热阵列测量系统的研制成功解决了大面积、大动态范围激光束总能量和光强分布绝对测量的技术难题,为激光束能量绝对分布测量提供了一种有效的手段。

基于GPRS技术的配电线路故障自动定位系统

为解决小电流接地系统线路故障,尤其是单相接地故障的自动定位问题,提出一种实现配电线路短路故障和单相接地故障快速自动定位的新方法。该方法通过检测过流现象判断相间短路故障,通过在中性点投入中电阻增加接地故障电流有功分量的方法实现单相接地故障的检测。故障检测信息通过通用分组无线业务(GPRS)无线通信网络上报至自动定位系统主站,主站自动定位分析软件根据各节点上报的故障检测信息,可以定位出故障所在区段。

高效液相色谱(HPLC)分离和检测蛋白质

对近年来利用高效液相色谱 (HPLC)分离检测蛋白质的研究作了综述。比较详细地介绍了用于蛋白质分析的各种HPLC模式、检测器、以及联用技术的发展情况 。

中子感生瞬发γ射线能谱的蒙卡模拟

中子感生瞬发γ射线分析(PGNAA)中使用蒙卡技术模拟物料与中子反应后产生的瞬发光子在NaI(Tl)探测器中的响应一直是一个难点。介绍了用于PGNAA的专用蒙卡程序NPTrans,NPTrans能够进行中子、光子级联输运并能够给出光子在NaI(Tl)探测器中的响应。给出了蒙卡模拟能谱与实验数据的比较。NPTrans的开发经验为其他研究开发专用的蒙卡程序提供了一定的借鉴。

固体核径迹自动测量系统及其主要应用

图象分析技术在固体核径迹自动测量中有着重要的作用 ,特别是在径迹参数测量方面更具显著特点。本文阐述了固体核径迹自动计数和参数测量的方法及其主要的应用领域。

碲锌镉阵列探测器的研究

碲锌镉(CdZnTe)阵列探测器是近年来迅速发展的新型半导体探测器,具有高空间分辨率、高能量分辨率和可在室温下工作的特点.介绍了碲锌镉晶体的物理特性和工作原理,并重点叙述了碲锌镉阵列探测器的制作工艺,包括晶片的预处理、钝化、欧姆电极制作、阵列模板选择、阵列封装工艺选择(微互联方式).为了测试碲锌镉探测器性能,中国科学院暗物质与空间天文重点实验室和合作单位成功制作了4 pixel×4 pixel和8pixel×8 pixel碲锌镉阵列(厚度分别为5mm和2 mm,像素大小为2 mm×2 mm,间隙分别为0.15 mm和0.2 mm).在^(137)Cs放射源照射下,实验室利用自行研制的、基于ASIC(Application Specific Integrated Circuit)芯片的多通道电子读出系统,对4 pixel×4 pixel碲锌镉阵列进行了实验评估,首次获得了16 pixel的能谱以及对应的能量分辨本领,其最优分辨本领达4.8%@662 keV.

利用LBIC技术对InGaAs平面结器件结区特性的研究

室温铟镓砷(InGaAs)焦平面技术在航天工业上的应用越来越广泛,铟镓砷(InGaAs)焦平面列阵中探测器的尺寸正不断减小,这使得常规工艺形成的光伏探测器,其有效光敏元面积扩大的问题越来越突出。本文利用激光诱导电流检测(LB IC)系统测试了平面结InGaAs(P-I-N)探测器芯片的光敏元,证实了有效光敏面扩大的存在。从实验结果看,掺杂离子的横向扩散和结区的侧向收集效应,是平面工艺形成的光伏器件光敏元面积扩大的主要因素,并利用得到的实验数据拟合求出了器件少子的扩散长度。