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.

Design and development of multi-channel front end electronics based on dual-polarity charge-to-digital converter for SiPM detector applications

With the development of silicon photomultiplier(SiPM)technology,front-end electronics for SiPM signal processing have been highly sought after in various fields.A compact 64-channel front-end electronics(FEE)system achieved by fieldprogrammable gate array-based charge-to-digital converter(FPGA-QDC)technology was built and developed.The FEE consists of an analog board and FPGA board.The analog board incorporates commercial amplifiers,resistors,and capacitors.The FPGA board is composed of a low-cost FPGA.The electronics performance of the FEE was evaluated in terms of noise,linearity,and uniformity.A positron emission tomography(PET)detector with three different readout configurations was designed to validate the readout capability of the FEE for SiPM-based detectors.The PET detector was made of a 15×15 lutetium–yttrium oxyorthosilicate(LYSO)crystal array directly coupled with a SiPM array detector.The experimental results show that FEE can process dual-polarity charge signals from the SiPM detectors.In addition,it shows a good energy resolution for 511-keV gamma photons under the dual-end readout for the LYSO crystal array irradiated by a Na-22 source.Overall,the FEE based on FPGA-QDC shows promise for application in SiPM-based radiation detectors.

Wireless Preamplifier for the Specimen Current Mode Detector in a SEM

Using a scanning electron microscope (SEM) in the back-scattered electron (BSE) mode the composition of multi-element specimens may be determined based on the strong dependence of emission coefficient η on the average atomic number of elements Z. The output video signal of the usual BSE detectors is produced from their sensors, and the larger proportion of high-energy electrons with modified spectrum is added. Since η = is/ip (is and ip currents of specimen and probe), better accuracy must be achieved by direct measurements those currents on the specimen surface. Here, an experimental model of a current detector for a presented specimen is described. The cage is mounted on the carousel of the moving specimen stage. The input of the preamplifier is connected to the specimen holder in the form of a disk, the diameter of which is 12 mm. When the probe along its surface scanned, the input potential begins to pulsate with a negative polarity. The output of this preamplifier is connected to a small light-emitting diode, which creates intensity-modulated radiation in the chamber. Thus created the light video signal will be picked up by the photomultiplier of the E-T detector. The modes of true SE and BSE are set by applying tens bias volts of various polarities to the specimens or the cage itself.

Test of the LHAASO electron detector prototype using cosmic rays

The LHAASO project is to be built in south-west China, using an array of 5137 electron detectors for the measurement of incident electrons arriving at the detector plane. For quality control of the large number of electron detectors, a cosmic ray hodoscope with two-dimensional spatial sensitivity and good time resolution has been developed. The first prototype of the electron detector has been tested with the hodoscope and the performance of the detector is found to be consistent with the design.

Readout electronics for a high-resolution soft X-ray spectrometer based on silicon drift detector

The readout electronics for a prototype soft X-ray spectrometer based on silicon drift detector(SDD),for precisely measuring the energy and arrival time of X-ray photons is presented in this paper.The system mainly consists of two parts,i.e.,an analog electronics section(including a pre-amplifier,a signal shaper and filter,a constant fraction timing circuit,and a peak hold circuit)and a digital electronics section(including an ADC and a TDC).Test results with X-ray sources show that an energy dynamic range of 1-10 keV with an integral nonlinearity of less than 0.1%can be achieved,and the energy resolution is better than 160 eV @ 5.9 keV FWHM.Using a waveform generator,test results also indicate that time resolution of the electronics system is about 3.7 ns,which is much less than the transit time spread of SDD(<100 ns)and satisfies the requirements of future applications.

Enhancement of terahertz coupling efficiency by improved antenna design in GaN/AlGaN high electron mobility transistor detectors

An optimized micro-gated terahertz detector with novel triple resonant antenna is presented.The novel resonant antenna operates at room temperature and shows more than a 700% increase in photocurrent response compared to the conventional bowtie antenna.In finite-difference-time-domain simulations,we found the performance of the self-mixing GaN/AlGaN high electron mobility transistor detector is mainly dependent on the parameters L gs（the gap between the gate and the source/drain antenna） and L w（the gap between the source and drain antenna）.With the improved triple resonant antenna,an optimized micrometer-sized AlGaN/GaN high electron mobility transistor detector can achieve a high responsivity of 9.45×102 V/W at a frequency of 903 GHz at room temperature.

Two-dimensional electron gas characteristics of InP-based high electron mobility transistor terahertz detector

The samples of InxGa（1-x）As/In（0.52）Al（0.48）As two-dimensional electron gas（2DEG）are grown by molecular beam epitaxy（MBE）.In the sample preparation process,the In content and spacer layer thickness are changed and two kinds of methods,i.e.,contrast body doping andδ-doping are used.The samples are analyzed by the Hall measurements at 300 Kand 77 K.The InxGa1-xAs/In0.52Al0.48As 2DEG channel structures with mobilities as high as 10289 cm^2/V·s（300 K）and42040 cm^2/V·s（77 K）are obtained,and the values of carrier concentration（Nc）are 3.465×10^12/cm^2 and 2.502×10^12/cm^2,respectively.The THz response rates of In P-based high electron mobility transistor（HEMT）structures with different gate lengths at 300 K and 77 K temperatures are calculated based on the shallow water wave instability theory.The results provide a reference for the research and preparation of In P-based HEMT THz detectors.

Prototype of the readout electronics for the RICH PID detector in the STCF

The ring imaging Cherenkov(RICH) detector for particle identification(PID) is being evaluated for the future super tau-charm facility(STCF) complex. In this work, the prototype readout electronics for the RICH PID detector is designed. The prototype RICH PID detector is based on a thick gas electron multiplier combined with a micromegas detector for Cherenkov light detection. Considering that there will be a large number(~ 690,000) of detector channels in future RICH detector, the readout electronics faces many challenges to precisely measuring time and charge information, such as reducing the noise,increasing density, and improving precision. The requirements of the readout electronics are explored, the downselection of the ASICs is made and thus a prototype readout electronics is designed and implemented. Tests are also conducted to evaluate the performance of the prototype readout electronics, and the results indicate that the time resolution is better than ~ 1 ns(RMS) when the input charge is greater than ~ 12 fC based on the APV25chip, while the time resolution is better than ~ 1 ns(RMS) at an input charge of over ~ 48 fC based on the AGET and STCF ASIC chips, and the equivalent noise charge is better than ~ 0.5 fC(RMS) @ 20 pF based on the three ASICs. The test results indicate that the prototype readout electronics design meets the requirement of the future RICH PID detector and thus provides a reference for future engineering.

Developing cold-resistant high-adhesive electronic substrate for WIMPs detectors at CDEX

Herein we report a prototypical electronic substrate specifically designed to serve the weakly interacting massive particles(WIMPs)detectors at the China Dark Matter Experiment(CDEX).Because the bulky high-purity germanium(HPGe)detectors operate under liquid-nitrogen temperatures and ultralow radiation backgrounds,the desired electronic substrates must maintain high adhesivity across different layers in such cold environment and be free from any radioactive nuclides.To conquer these challenges,for the first time,we employed polytetrafluoroethylene((C2F4)n)foil as the base substrate,in conjunction with ion implantation and deposition techniques using an independently developed device at Beijing Normal University for surface modification prior to electroplating.The remarkable peeling strengths of 0.88±0.06 N/mm for as-prepared sample and 0.75±0.05 N/mm for that after 2.5-days of soaking inside the liquid nitrogen were observed,while the regular standards commonly require 0.4 N/mm^0.6 N/mm for electronic substrates.

Optical and electronic performances of CVD diamond film andits applications in radiation detectors

The outstanding properties of CVD diamond film such as electronic, optical, thermal and mechanical and the high radiation hardness have made it an ideal candidate material for radiation detectors in severe environments. Fabrication of ＇detector grade＇ CVD diamond films and development of CVD diamond detectors have been leading edge subjects. Micro-strip gas chamber （MSGC） fabricated on CVD diamond substrate would overcome the charge-up effect and the substrate instability, which has been a hotspot in the research of gas detectors.

Terahertz Direct Detectors Based on Superconducting Hot Electron Bolometers with Microwave Biasing

Terahertz （THz） direct detectors based on superconducting niobium nitride （NbN） hot electron bolometers （HEBs） with microwave （MW） biasing are studied. The MW is used to bias the HEB to the optimum point and to readout the impedance changes caused by the incident THz signals. Compared with the thermal biasing method, this method would be more promising in large scale array with simple readout. The used NbN HEB has an excellent performance as heterodyne detector with the double sideband noise temperature （T N） of 403K working at 4.2K and 0.65THz. As a result, the noise equivalent power of 1.5pW/Hz 1/2 and the response time of 64ps are obtained for the direct detectors based on the NbN HEBs and working at 4.2K and 0.65THz.

Design of a new vacuum Compton gamma-ray detector with clad metal electron-converter plate

A newly designed vacuum Compton gamma-ray detector with Ta-Al clad-metal electron converter plate is described. The detecting efficiency for 1.25 MeV gamma-ray is 7.85×10-3 electron/γ,which is 2.5 times higher than that with Fe converter plate. The designed detector has the merits of well processed and static vacuum keeping and can be used for intense pulsed gamma ray detecting.

Development of Electron Temperature Measuring System by Silicon Drift Detector

The soft X-ray spectroscopy, laser Thomson scattering and electron cyclotron emission （ ECE ） are usually adopted for electron temperature measurement in fusion research of magnetic confinement. The particular soft X-ray spectroscopy has the very good spatial-temporal resolution and smaller measuring error than laser Thomson scattering, a close spatial-temporal resolution to ECE, absolute measurement ability, and smaller influence by suprathermal and runaway electrons than ECE.

非电离室型探测器在深度剂量扫描中的应用研究

为研究非电离室型探测器在深度剂量分布扫描中的响应特性,通过采用平板电离室、半导体和宝石探测器对医用光子束和电子束深度剂量分布进行扫描,并以平板电离室作为参考,分析比较半导体和宝石探测器在最大剂量深度、射线质等参数来探究其在深度剂量上的性能。结果表明:医用光子束下除两支探测器外,其余探测器获得的射线质与参考值的最大相对偏差为-0.67%,符合TRS-398报告高能光子束允许的不确定度1.0%,电子束<10 MeV时,各能量下非电离室型探测器获得的射线质与参考值的平均相对偏差最小为1.91%,能量≥10 MeV时,平均相对偏差最大为1.01%,除两支探测器外,其余探测器的相对偏差最大为-1.15%,符合TRS-398报告高能电子束允许的不确定度1.2%。P型半导体探测器获得的射线质与参考值的相对偏差在±0.85%内,比E型半导体探测器的相对偏差范围±0.67%大。结论:非电离室型探测器在高能光子束下影响较小,电子束<10 MeV时影响较大,能量≥10 MeV时影响较小,且尽量选择E型半导体探测器,并考虑探测器外壳材质。

LYSO:Ce电子辐射探测器输出响应影响因素研究

针对地球静止轨道(Geostationary Earth Orbit,GEO)空间粒子辐射对卫星在轨运行时产生的电离总剂量效应,将高性能铈掺杂硅酸钇镥(LYSO:Ce)晶体与铝层结合,来屏蔽质子辐照影响,实现电子辐射剂量的有效探测。基于Geant4建立探测器模型,比较不同材料的屏蔽效果,分析探测器响应特性,研究影响探测器输出响应的因素。结果表明:使用0.022 mm厚的铝层作为屏蔽层包裹光纤,可排除质子辐照影响;基于LYSO:Ce晶体的探测器具有较好的线性响应,电子穿越屏蔽层时产生的次级电子、光子可以提高探测器响应灵敏度;物质对电子的电离阻止本领与入射电子速度的平方近似成反比,适当增加电子与探测器之间传输距离,可增强探测器的辐射响应;探测器对能量区间在0.04~1 MeV的电子探测效率最高。通过研究LYSO:Ce晶体与铝层结合的电子辐射剂量探测器特性,为新型闪烁体空间辐射探测器设计提供技术参考和理论支撑。

用于小型AMS的类布拉格探测器研制

为了解决小型AMS系统中,使用现有的气体电离室探测低能量重粒子时,脉冲信号高度与探测器本底噪声重合较多、难以有效区分的问题,研制了一种新型的类布拉格气体电离室。在一定的约化场强下,这种电离室能够使电子在阳极附近区域发生电子倍增,从而使脉冲信号高度上升,以达到与探测器本底噪声分开的目的。利用5.8 MeV的α粒子进行实验,通过调节α粒子进入探测器的能量,并在不同气体压力、阳极电压(约化场强E/P)的条件下对探测器性能进行系统调试。经过模拟计算和系统调试,得出以下结论:该探测器可用于测量粒子的能谱,能量分辨率可达到2.98%。当阳极前1 mm处的约化场强E/P为5 V·mm^(-1)·hPa^(-1)时,脉冲信号的增益大约为7倍。

重离子储存环CSRe上类钠Kr^(25+)离子的双电子复合精密谱学实验研究

高电荷态离子的双电子复合精密谱学实验研究,不仅对天体等离子体和聚变等离子体的研究具有重要意义,而且可以作为一种新的精密谱学工具,用来检验强场量子电动力学效应、测量同位素移动及提取原子核电荷半径等.在兰州重离子储存环CSRe上,安装了专门用于电子-离子复合精密谱学实验的电子束能量调制系统,质心系下电子-离子碰撞能量的调制范围达到0—1 keV.在CSRe电子冷却器下游安装了自主研制的塑料闪烁体探测器和多丝正比探测器,用于探测复合离子.在此基础上,使用Kr^(25+)离子在CSRe上进行了首次双电子复合测试实验,实验测量了质心系能量0—70 eV的双电子复合速率系数.为了更好地理解实验测量结果,利用FAC(flexible atomic code)程序计算了Kr^(25+)离子的双电子复合速率系数,并与实验做了细致对比,整体符合很好,而且发现3s→41(△n=1)的共振跃迁对实验谱线有很大的贡献.实验结果表明,CSRe双电子复合实验平台具有非常好的稳定性和可重复性,能够为下一步开展更高电荷态离子的双电子复合精密谱学实验、检验强场量子电动力学效应以及原子核性质精密测量等前沿实验提供支持.

侧栅晶体管太赫兹探测器的物理模型、结构制备与直流测试

针对侧栅结构高电子迁移率晶体管(High Electron Mobility Transistors,HEMTs)太赫兹探测器,构建了器件的直流输运和太赫兹探测的物理模型。运用自对准工艺,成功制备了形态良好、接触可靠的侧栅结构,有效地解决了器件双侧栅与台面间的接触问题,最终获得了不同栅宽(200 nm、800 nm和1400 nm)的侧栅GaN/AlGaN HEMT太赫兹探测器。通过直流测试表征发现,不同器件的栅宽与其阈值电压之间呈现出明显的线性关系,验证了侧栅结构HEMT太赫兹探测器的直流输运模型。上述结果为完整的侧栅HEMT太赫兹探测器的理论模型提供了实验验证和指导,为侧栅HEMT太赫兹探测器的发展提供了重要支持。

硅基热电子短波红外探测技术(封面文章·特邀)

短波红外具有穿透烟雾的特性,可在低光照环境或恶劣天气条件下成像,在军事、安防、环境监测等多个领域展现出重要应用价值。硅基热电子短波红外探测技术因具备与CMOS半导体工艺兼容、响应波段灵活可调等独特优势,已成为当前研究的热点。文中系统地回顾了该领域的国内外研究进展,剖析了与光电转换效率密切相关的热电子产生、传输与注入等物理过程中的能量损耗机制。在此基础上,总结了针对性的改进策略,包括通过光学吸收增强和热损耗抑制来增加热电子的产生效率;通过精确调控热电子的初始位置、能量、动量分布及自由程来优化其传输过程;以及利用肖特基结和界面调控等技术来提高热电子的注入概率。此外,文中还讨论了暗电流的抑制方法,以期提升探测器的整体性能。最后,展望了硅基热电子红外光电探测器未来的发展方向。

基于运算放大器的超导纳米线单光子探测器低温直流耦合读出电路

超导纳米线单光子探测器(SNSPD)具有高计数率、高探测效率和低暗计数等优点,在光量子通信、光量子计算、激光测距与成像等领域发挥着重要作用.SNSPD的最大计数率(探测速度)会受前级读出电路的影响,为了提升最大计数率,通常需要使用一个宽带宽的低温直流耦合读出电路.本文报道了基于商用高速运算放大芯片OPA855搭建的SNSPD低温直流耦合放大读出电路,系统表征了该电路从室温300 K到低温4.2 K下的性能参数.通过提升OPA855的工作电压,解决了电路在低温下带宽损失的问题.进一步,将OPA855放大电路安装在40 K温区,使用其实现了SNSPD探测性能的实验评估.相对于常规室温交流耦合电路,SNSPD的最大计数率约提升了1.3倍.本研究可为OPA855芯片在高速SNSPD等低温领域提供相关参考信息.