厚型气体电子倍增探测器(THGEM)在15～70 keV X射线测量中的应用

本文采用了自主研发的THGEM探测器,其具有双膜结构,64路直流读出电子学等特点。采用该THGEM探测器在K荧光装置上,开展了对15~70 ke V内多能量点X射线的探测实验工作;结果显示该THGEM探测器对宽能区、高注量(剂量当量)的X射线具有良好线性响应,并分析了影响探测效率的因素。

利用转化体实现THGEM在高能γ射线测量中的研究

为提高厚型气体电子倍增探测器对高能伽马射线的探测效率,研制高Z材料的光电转化体,将伽马射线转化为电子后测量.通过研究设计了多孔铅型的光电转化体(孔直径1 mm、孔间距1.2 mm),理论计算其光电转化效率为6%.并结合转化体和单模THGEM探测器建立探测系统,测量662 keV伽马射线.结果显示,含转化体的THGEM探测系统对662 keV光子探测效率达到了3%,说明转化体对于提高探测效率是有效的;同时分析探测效率略低于转化体光电转化率的理论计算值6%的主要因素为探测器外结构膜窗对低能光电子造成的损失.

直流读出的THGEM探测系统及其在X射线上的应用

THGEM是一种新型的具有计数率高、抗辐射、高增益和相对价廉等优点的气体探测器。采用适合实时记录多路多次信号累积效应的直流读出模式的THGEM探测系统测量了X射线的绝对强度及其相对强度的二维空间分布,并对多路成像效应进行了初步的探索。

薄型较大面积THGEM气体探测器的研制

为满足环形正负电子对撞机项目配置的需要,研制了薄型较大面积THGEM气体探测器。该探测器工作时不需要额外的腔室,并且其厚度能达到8 mm,较原来的11 mm有明显减少。其有效面积为20 cm×20 cm,其增益在Ar/iC_4H_(10)(97/3)工作气体中能达到10~4倍,最好能量分辨为30%,增益均匀性能达到88.5%,探测器增益也呈现出较好的长期稳定性。

THGEM数字读出成像探测器系统设计

本文介绍了一种基于THGEM的数字读出型气体电子倍增探测器设计。采用自制THGEM膜板,阳极板采用64X-64Y路条读出,通过多路电子学信号读出的前置模拟放大、过阈、成形、串行读出集成电路芯片GASTONE,可实现在线位置重建。结果表明,探测器位置分辨能力在400μm左右,达到理论预期值。利用多次阈值电压递减法完成了X射线成像以及β射线在室体灵敏空间内能量沉积响应。

Development of alpha surface contamination monitor based on THGEM for contamination distribution

In cases of high radiation emergencies,we propose a surface contamination monitor(SCM)that can quickly measure and pinpoint the contamination distribution in the affected population.Thick gaseous electron multiplier(THGEM)has several advantages,including fast response time and good spatial resolution.Based on new THGEMs,a two-dimensional imaging detector was developed for alpha detection,with a position resolution greater than 3 mm.The detector design and test results are described in this paper.Fast radiation imaging SCMs,with a 40mm×40 mm sensitive area,are currently under development.

THGEM探测器化学抛光及其工作气体优化

采用新的化学抛光方法处理HGEM膜,在不同的气体成分和比例下对THGEM膜的增益和能量分辨进行研究测量.结果表明,以Ar/C4H10为工作气体的THGEM探测器所需工作电压较低、增益高、能量分辨相对较好.在Ar/C4H10(95%/5%)的气体条件下,THGEM的增益可达7×10^3.

A Cosmic-Ray Muon Hodoscope Based on Up-down THGEM Detectors

Thick gas electron multipliers (THGEMs) are new types of gas detectors with merits such as a high counting rate,anti-radiation,high gain,robustness and relatively low cost.We establish an up-down THGEM detector hodoscope system for detecting and displaying muon tracks.Muon tracks can be well observed with the detectors and the present study lays an important technological foundation for the domestic and mass production of THGEMs.

Simulation and optimization of a double THGEM detector

A double thick GEM (THGEM) detector with thin THGEM foils and small holes was constructed. In order to optimize the operation parameters of the detector, a simulation study of the detector was carried out using ANSYS and Garfield program. Some important characteristics, including primary electron transparency, avalanche development and the secondary electron loss were calculated. Parameters, such as electric field and gas choice were optimized.

应用于热中子的nTHGEM探测器性能研究

随着脉冲强流中子源的发展,对高性能中子探测器提出了更大的挑战,3He气体资源严重短缺和高计数率中子探测器的迫切需求,已开始制约着中子源应用技术的发展。中国科学院高能物理研究所针对中子的特殊性,专门研发了一种陶瓷基材的n THGEM(neutron Thick Gaseous Electron Multiplier)探测器用于中子探测。基于n THGEM的中子探测器具有高计数率、高位置与时间分辨能力、增益大、制作工艺简单,且便于大面积制作的特点,是目前国际上发展替代~3He探测技术的重要方向之一。为了详细研究n THGEM探测器的本身性能,本工作使用^(55)Fe放射源研究了n THGEM探测器的增益、计数率稳定性、能量分辨率等关键参数与n THGEM膜间电压、收集场强、漂移场强之间的关系,优化了n THGEM探测器在不同工作气体中的工作参数,为后续进一步优化n THGEM探测器设计和工艺奠定了基础。实验结果表明,单层n THGEM探测器在Ar(90%)+CO2(10%)混合气体中增益能达到103,探测器计数率稳定性良好。另外,还在中国原子能科学研究院的CARR反应堆(China Advanced Research Reactor)上进行了中子束流实验,通过狭缝测量到探测器位置分辨率为(3.01±0.03)mm(FWHM),已经接近高气压3He MWPC中子探测器水平。

THGEM探测器X光斑寻迹和位置分辨实验研究

介绍了一种基于THGEM的X射线光斑寻迹探测器,用于X射线单光子计量技术研究和测量,探测器有效面积200 mm×200 mm,采用128路基于ASIC和FPGA的高速读出电子学,探测器分为中间高分辨区和外围低分辨区两部分,两部分共用一套读出电子学。实验在中国计量科学研究院利用X光机产生的束线,测试光斑位置、光斑精细分布以及探测器的位置分辨。实验结果表明,探测器实现了同时对光斑寻迹和光斑的精细测量,探测器中间高分辨区x方向的位置分辨率为0.63 mm(FWHM),y方向位置分辨率为0.62mm(FWHM),探测器各项性能指标均达到了预期目标。

新型M-THGEM结构探测器的蒙特卡罗模拟研究

新型多层厚型气体电子倍增器(Multi-layers THick Gas Electron Multiplier,M-THGEM)和传统THGEM(厚型气体电子倍增器)相比,具有连续的雪崩区,能够在低气压和低电压下都有较高增益,结构更紧凑,易于大面积制作等优势。对M-THGEM探测器的工作原理及性能进行了模拟研究,首先通过有限元(ANSYS)软件对二层与三层结构的M-THGEM进行了建模,对电场和电势分布分别进行了模拟计算;再利用Garfield++程序包对M-THGEM探测器在不同低气压和不同工作电压下的增益、感生信号、正离子反馈率等性能进行了研究。模拟结果表明,三层结构M-THGEM在低气压(200 Torr)、纯He气体条件下,能够获得较稳定的增益(10~5),输出信号的宽度在12 ns左右;同时,为降低正离子反馈率,本工作提出并研究了一种非对称的电压施加方式,结果表明,这种施加方式能有效降低正离子的反馈率。

Experimental studies of THGEM in different Ar/CO_2 mixtures

In this paper, the performance of a type of domestic THGEM （THick Gaseous Electron Multiplier） working in Ar/CO2 mixtures is reported in detail. This kind of single THGEM can provide a gain range from 100 to 1000, which is very suitable for application in neutron detection. In order to study its basic characteristics as a reference for the development of a THGEM based neutron detector, the counting rate plateau, the energy resolution and the gain of the THGEM have been measured in different Ar/CO2 mixtures with a variety of electrical fields. For the Ar/CO2（90%/10%） gas mixture, a wide counting rate plateau is achieved from 720 V to 770 V, with a plateau slope of 2.4%/100 V, and an excellent energy resolution of about 22% is obtained at the 5.9 keV full energy peak of the 55Fe X-ray source.

Study of the THGEM detector with a reflective CsI photocathode

The THGEM detector without and with a CsI has been tested successfully. The optimal parameters of THGEM have been determined from eight samples. The UV photoelectric effect of the CsI photocathode is observed. The changing tendency related to the extraction efficiency （εextr） versus the extraction electric field is measured, and several electric fields influencing the anode current are adjusted to adapt to the THGEM detector with a reflective CsI photocathode.

Performance study of the PTFE-THGEM at room and low temperature

GPM based on THGEM has shown its competitive strength compared to the conventional PMT, espe- cially in the low background research such as dark matter detection. A kind of THGEM made from PTFE, named PTFE-THGEM, is developed for the GPM to be used in CDEX. The PTFE has a lot of advantages especially its low level radioactivity. The PTFE-THGEM was tested at room and cryogenic temperature. It has a high gain in different gases and shows good stability at room temperature. The gain of a single PTFE-THGEM reached 112 at 117 K. The penning effect is also discussed in this paper to explain the ＂abnormal＂ phenomena of the gain in different gases.

Experimental study of a THGEM detector with mini-rims

The gas gain and energy resolution of single and double THGEM detectors （5 cm×5 cm effective area） with mini-rims （rim less than 10 um） were studied. The maximum gain was found to reach 5×103 and 2 × 105 for single and double THGEMs respectively, while the energy resolution for 5.9 keV X-rays varied from 18% to 28% for both single and double THGEM detectors of different hole sizes and thicknesses. Different combinations were also investigated of noble gases （argon, neon） mixed with a quantity of other gases （isobutane, methane） at atmospheric pressure.

Experimental research on a THGEM-based thermal neutron detector

A new thermal neutron detector with a domestically produced THGEM （Thick Gas Electron Multiplier） was developed as an alternative to 3He to meet the needs of the next generation of neutron facilities. One type of Au-coated THGEM was designed specifically for neutron detection. A detector prototype has been developed and the preliminary experimental tests are presented, including the performance of the Au-coated THGEM working in At/CO2 gas mixtures and the neutron imaging test with 252 Cf source, which can provide the reference for experimental data for research in the future.

Study of a nTHGEM-based thermal neutron detector

With new generation neutron sources, traditional neutron detectors cannot satisfy the demands of the applications, especially under high flux. Furthermore, facing the global crisis in 3He gas supply, research on new types of neutron detector as an alternative to 3He is a research hotspot in the field of particle detection. GEM （Gaseous Electron Multiplier） neutron detectors have high counting rate, good spatial and time resolution, and could be one future direction of the development of neutron detectors. In this paper, the physical process of neutron detection is simulated with Geant4 code, studying the relations between thermal conversion efficiency, boron thickness and number of boron layers. Due to the special characteristics of neutron detection, we have developed a novel type of special ceramic nTHGEM （neutron THick GEM） for neutron detection. The performance of the nTHGEM working in different Ar/CO2 mixtures is presented, including measurements of the gain and the count rate plateau using a copper target X-ray source. A detector with a single nTHGEM has been tested for 2-D imaging using a 252Cf neutron source. The key parameters of the performance of the nTHGEM detector have been obtained, providing necessary experimental data as a reference for further research on this detector.

Study of a sealed high gas pressure THGEM detector and response of alpha particle spectra

A sealed high gas pressure detector working in pure argon is assembled.It consists of a 5 cm × 5 cm PCB THGEM（THick Gaseous Electron Multiplier）.The detector structure and experimental setup are described.The performance under high pressure（2 atm） is examined,selecting optimal voltages for the ionization region and induction region.The dependence of the shape of alpha particle spectra measured with relative gas gain on gas pressure（1.3-2.0 atm） has been studied.Eight data sets of relative gas gain versus working voltage of THGEM,expressed by weighting field E/P,are normalized,consistent with theory.The results show that the air tightness of the chamber is good,measured by a sensitive barometer and checked with gas gain.The experimental results are compared with Monte Carlo simulation of energy deposition without gas gain involved.

p/π^+ response of single layer THGEM detector in Ar+3% iC_4H_(10)

In this work, we study the response of a single layer Thick Gaseous Electron Multiplier （THGEM） detector to p/π＋ at the E3 line of the Beijing Test Beam Facility. The THGEM detector drift gap used in this study is 4 mm, and the gain of the detector operated in Ar＋3% iC4H10 is about 2000. p/π＋ particles at momenta between 500 MeV/c and 1000 MeV/c are distinguished by a Time Of Flight system. Our results show that at the measured momenta, detection efficiencies for p are from 93% to 99%, and for π＋ in the range of 82%-88%. Meanwhile, simple Geant4 simulations also have been done, and are consistent with the amplitude spectra of the beam test results. We preliminarily study the feasibility of the THGEM detector as a sampling element for a Digital Hadronic Calorimeter （DHCAL）, which may provide support for the possible application of a THGEM detector in the Circular Electron Positron Collider （CEPC） HCAL.