Development of large-area quadrant silicon detector for charged particles

The quadrant silicon detector, a kind of passivated implanted planar silicon detector with quadrant structure on the junction side, gained its wide application in charged particle detection. In this paper, the manufacturing procedure, performance test and results of the quadrant silicon detector developed recently at the China Institute of Atomic Energy are presented. The detector is about 300 μm thick with a 48 mm×48 mm active area. The leakage current under the full depletion bias voltage of -16 V is about 2.5 nA, and the rise time is better than 160 ns. The energy resolution for a 5.157 MeV α-particle is around the level of 1%. Charge sharing effects between the neighboring quads, leading to complicated correlations between two quads, were observed when α particles illuminated on the junction side. It is explained as a result of distortion of the electric field of the inter-quad region. Such an event is only about 0.6% of all events and can be neglected in an actual application.     

A Bragg curve detector and its application in AMS measurements for medium-weight nuclides

The schematic layout and principle of a Bragg curve detector were showed in this paper. A Bragg curve detector was systemically modified and its performance was improved. The total energy resolution of the detector is 0.9% for alpha particle at energy of 5.48 MeV from ²⁴¹Am source, and the Bragg Peak resolution is 1.6%. Measurement of medium-weight nuclides by using the Bragg curve detector were carried at CIAE-AMS system. series of ³⁶Cl and ⁴¹Ca standard samples were measured. The results showed that this Bragg curve detector could clearly identify isobars ³⁶Cl-³⁶S and ⁴¹Ca-⁴¹K. The results also showed that the ΔZ/Z of 1/47, corresponding to Bragg Peak resolution is 2.1% at ion atomic number of about 16. The Bragg curve detector can be successfully used for AMS measurement.     

Study of 2D interpolating readout for a micro-pattern gaseous detector

The two-dimensional interpolating readout, a new readout concept based on resistive anode structure, was studied for the micro-pattern gaseous detector. Within its high spatial resolution, the interpolating resistive readout structure leads to an enormous reduction of electronic channels compared with pure pixel devices, and also makes the detector more reliable and robust, which is attributed to its resistive anode relieving discharge. A GEM (gaseous electron multiplier) detector with 2D interpolating resistive readout structure was set up and the performance of the detector was studied with 55Fe 5.9 keV X-ray. The detector worked stably at the gain up to 3.5 × 104 without any discharge. An energy resolution of about 19%, and a spatial resolution of about 219 μm (FWHM) were reached, and good imaging performance was also obtained.     

CsI（Tl）+Si-APD探测器的性能测试

介绍了Si-APD的工作原理并对Si-APD中的暗电流进行了理论分析。基于RIBLL上产生的放射性核束流,使用CsI（Tl）+Si-APD探测器对中能重离子进行了能量测试。测试结果显示,CsI（Tl）+Si-APD探测器测量20 MeV/u的重离子时,可得到3%的能量分辨;同时还发现Si-APD中的暗电流大小以及入射粒子的能量大小都会对探测器的能量分辨产生影响。In this paper, the working principle of Si-APD was introduced and the dark current of Si-APD was analyzed theoretically. The intermediate energy heavy ions, which are produced on the RIBLL(Radioactive Ion Beam Line in Lanzhou), were measured with CsI(Tl)+Si-APD detector. The energy resolution of CsI(Tl)+Si-APD detector is about 3% for heavy ions with energy around 20 MeV/u. It is also found that the energy resolution of detector can be in uenced by the dark current of Si-APD and the energy of incident particles.     

Study on gamma response function of E J301 organic liquid scintillator with GEANT4 and FLUKA

The gamma response function is required for energy calibration of EJ301 （5 cm in diameter and 20 cm in height） organic liquid scintillator detector by means of gamma sources. The GEANT4 and FLUKA Monte Carlo simulation packages were used to simulate the response function of the detector for standard 22Na, 60Co, 137Cs gamma sources. The simulated results showed a good agreement with experimental data by incorporating the energy resolution function to simulation codes. The energy resolution and the position of the maximum Compton electron energy were obtained by comparing measured light output distribution with simulated one. The energy resolution of the detector varied from 21.2% to 12.4% for electrons in the energy region from 0.341 MeV to 1.12 MeV. The accurate position of the maximum Compton electron energy was determined at the position 81% of maximum height of Compton edges distribution. In addition, the relation of the electron energy calibration and the effective neutron detection thresholds were described in detail. The present results indicated that both packages were suited for studying the gamma response function of EJ301 detector.     

Beam test of signal cross-talk and transmission for LMPRC

A new prototype of large area Multi-gap Resistive Plate Chamber (MRPC) with long readout strips was built. This Long-strip Multi-gap Resistive Plate Chamber (LMRPC) is double stacked and has ten 250 μm-thick gas gaps. Signals are read out from the two ends of each strip with an active area of 50 cm×2.5 cm in each. The detector was tested at FOPI in GSI, using the secondary particles of proton beams (E=3.5 GeV) colliding with a Pb target. The results show that the LMRPC prototype has a time resolution of about 60-70 ps; the detecting efficiency is over 98% and the ratio of cross-talk is lower than 2%. The detector also has a good spatial resolution of 0.36 cm along the strip direction.     

Performance evaluation of a parallel-hole collimated detector module for animal SPECT imaging

We have built and investigated a detector module for animal SPECT imaging, especially for use in large field of view (FOV) conditions. The module consists of a PMT-based detector and a parallel-hole collimator with an effective area of 80 mm × 80 mm. The detector is composed of a NaI scintillation crystal array coupled to four H8500 position sensitive photomultiplier tubes (PS-PMT). The intrinsic energy resolution of the detector is 11.5% at 140 keV on average. The planar spatial resolution of the module changes from 2.2 mm to 5.1 mm at different source-to-collimator distances with an unchanged sensitivity of about 34cps/MBq. Additionally, the SPECT Micro Deluxe Phantom imaging was performed with a radius of rotation (ROR) of 40 mm. Using the FBP reconstruction algorithm, a high performance image was obtained, indicating the feasibility of this detector module.     

Design and optimization of resistive anode for a two-dimensional imaging GEM detector

A resistive anode for two-dimensional imaging detectors,which consists of a series of high resistivity pads surrounded by low resistivity strips,can provide good spatial resolution while reducing the number of electronics channels required.The optimization of this kind of anode has been studied by both numerical simulations and experimental tests.It is found that to obtain good detector performance,the resistance ratio of the pads to the strips should be larger than 5,the nonuniformity of the pad surface resistivity should be less than 20%,a smaller pad width leads to a smaller spatial resolution,and when the pad width is 6 mm,the spatial resolution(σ) can reach about 105μm.Based on the study results,a 2-D GEM detector prototype with optimized resistive anode is constructed and a good imaging performance is achieved.     

超重反冲余核时间探测器性能测试

介绍了一种铝制内椭球面反射镜闪烁薄膜探测器,对其探测效率、光收集效率和时间性能的测试. 结果分析表明采用1 μm厚的BC498闪烁薄膜探测器测量实验中超重反冲余核, 探测效率接近100％, 时间分辨好于200 ps, 其性能满足超重反冲余核时间测量的要求. A thin plastic scintillator film detector with an inner ellipsoidal reflection mirror made of aluminum is introduced. Detection efficiency and light collection efficiency of the detector have been investigated. The time resolution of the detector has been also studied. The testing results show that the detection efficiency of BC498 with the thickness of 1 micron to be used in the coming superheavy synthesis experiments is approximately 100%, and the time resolution is better than 200 ps (σ). The performances of the thin plastic scintillator film detector meet the requirements for the time measurement of the superheavy element synthesis.     

兰州充气谱仪的焦平面探测系统

在兰州充气谱仪上,设计安装了一套新的焦平面探测系统,该系统包括飞行时间(TOF) 探测器、盒型硅(Si-box) 探测器阵列和反符合(Veto) 探测器3 部分。Si-box 探测器阵列是由3 块位置灵敏硅探测器(PSSD) 和8 块周边硅探测器(SSD) 构成,它对注入核的 衰变的探测效率达到80% 左右。Si-box 探测器阵列与TOF 探测器关联可以有效区分注入信号和 衰变信号。Veto 探测器与Si-box 探测器阵列和TOF 探测器关联可以反符合掉高能轻粒子对注入信号和 衰变信号的干扰。简要介绍了PSSD 的能量和位置刻度方法。这套探测器系统已经应用于40Ca+175Lu 和40Ca+169Tm 的实验。实验结果表明,该探测器系统具备很好的本底抑制能力,能够给出干净的a衰变能谱,结合能量-时间-位置关联测量方法可以实现对单原子的探测和鉴别,总体上达到了预期的设计要求。A new designed focal plane detection system was mounted at the gas-filled recoil separator at Institute of Modern Physics, Chinese Academy of Sciences, which consisted of a time-of-flight (TOF) detector, a silicon-box (Sibox) detector array and a silicon veto detector. Three position sensitive silicon detectors (PSSD) were surrounded by eight side silicon detectors (SSD) without position sensitive, forming a box of the detector open from the front side. The detection efficiency for -decays of implanted nuclei was about 80%. The anticoincidence condition for the signals from the TOF detector and Si-box detector array was used to distinguish between the pulses originating from the implanted nuclei and their -decays. The veto detector information was used to discriminate events due to high-energy charged particles．External energy calibration and position calibration of PSSD are described concisely in this work. This systemhas been used in experiments of 40Ca+175Lu and 40Ca+169Tm. Clean a-decay spectra obtained in these reactions indicated the detection system has a good performance in background suppression. Evaporation residues can be identified by the energy-time-position correlation method. On the whole, the new designed focal plane detection system has achieved thedesign requirements.     

Characterization of a triple-GEM position sensitive detector for X-ray fluorescence imaging

In this work, we characterized an X-ray position sensitive gaseous detector based in a triple stack of gas electron multipliers. The readout circuit is divided in 256 strips for each dimension and using a resistive chain interconnecting the strips, we are able to reconstruct the radiation interaction points by resistive charge division. The detector achieved gains above 10⁴, energy resolution of 15.28% (full width at half maximum) for 5.9 keV X-rays, and position resolution of 1.2 mm, while operating in Ar/CO₂(90/10) at atmospheric pressure.     

平直开缝翅片传热特性的三维数值模拟及场协同原理分析

本文用数值模拟的方法对翅片管换热器中广泛使用的平直开缝翅片的传热特性进行了数值模拟。结果表明在平翅片后部开缝与在翅片前部开缝相比,换热增强更多,并用场协同理论分析说明,在速度场和温度场协同比较差的区域开缝要比在场协同比较好的区域开缝对传热强化更有效。     

基于ASIC芯片的硅微条阵列探测器多通道前端电子学模块设计

描述了为兰州重离子加速器冷却储存环(HIRFL-CSR)外靶实验系统硅微条阵列探测器而设计的前端电子学模块。该模块采用专用ASIC芯片,可以处理96路能量信号。对前端电子学模块的性能进行了测试,结果表明,该模块在0.1～0.7 V范围内的积分非线性好于0.3%;其电子学分辨好于0.45%,最大串扰小于10%;通道一致性测试结果好于1.3%;在室温下连续工作24 h后,零点峰位最大漂移为1.48 m V。     

Graphene and metal hybridized terahertz metasurfaces toward tunable plasmon-induced transparency effects

Tunable metasurfaces have attracted much attention recently, owing to their capability of actively controlling electromagnetic waves. Here, we propose tunable graphene-metal hybridized terahertz (THz) metasurfaces exhibiting plasmon induced transparency (PIT) effects, driven alternately by metal and graphene resonators. The proposed meta-molecule comprises a central metal (graphene) strip placed orthogonally to two side graphene (metal) strips. Then, near-field coupling between the strips is probed by translating the central strip along the length of the side strips and the evolution of the PIT effect is investigated for orthogonal polarizations of probing THz. The coupled oscillator-based analytical model explains the coupling mechanism in these metasystems. We observe the strongest coupling and the most prominent PIT effect for edge-to-edge coupling (threshold position) between the central and side strips. Further, active PIT response is achieved by altering graphene's Fermi energy. These metasurfaces can contribute in designing compact and active metasurface-based hybrid devices for THz domain.     

一种有效提高太赫兹时域光谱装置成像空间分辨率的方法

太赫兹波成像技术一个最显著的制约因素是其有限的空间分辨率。提出通过在样品前加小孔的方法来提高传统太赫兹时域光谱装置成像的空间分辨率。采用在样品前约2 mm处加直径为0.5 mm小孔的方法使成像的空间分辨率从1.276 mm提高到0.774 mm,提高0.502 mm,约39％。通过这个简单的方法在传统的太赫兹时域光谱成像装置上实现了空间分辨率从毫米量级到亚毫米量级的提高。聚乙烯板上直径为1 mm的小孔被作为成像的研究对象,分别采用传统的太赫兹时域光谱装置对样品进行直接成像和在样品前约2 mm处加直径为0.5 mm的小孔后对样品成像两种方式,并采用损失成像中信噪比较好的能量损失成像,对比两种方式得到的样品的太赫兹像,结果显示聚乙烯板上小孔的边界加小孔后成像比不加小孔直接成像明显清晰。证实了在样品前加小孔可以有效的提高太赫兹成像系统的空间分辨率。从理论上对通过在样品前加小孔提高系统空间分辨率的方法进行了分析,指出小孔尺寸越小,系统的空间相干长度越大,空间分辨率越高,但同时太赫兹信号的强度会相应减小。该方法可以简单有效的提高太赫兹时域光谱装置成像的空间分辨率,从而进一步拓展太赫兹谱成像技术的应用领域。     

强流脉冲离子束能量密度分布的红外诊断

强流脉冲离子束在靶上的能量密度分布是其研究和应用的一个重要参数。为了解决现有束流能量密度诊断方法的不足,利用红外成像仪测量靶背面的温度分布,从而建立了强流脉冲离子束能量密度分布的红外诊断方法。对能量密度1J/cm2量级、脉冲宽度为102 ns量级的束流,该方法测量误差好于5%,空间分辨率可达到1~2mm,具有操作简便、成本低的优点,是强脉冲能量沉积分布的一种高效迅速的诊断方法。     

闪光照相中侧向散射的数值模拟

散射是闪光照相诊断技术中需要重点考虑的一个关键性问题,弄清散射的影响因素及其来源对于提高客体信息诊断精度具有十分重要的促进作用。针对法国实验客体照相系统,采用蒙特卡罗方法,系统研究了侧向散射的影响因素及其来源。结果表明:在没有侧向保护器的情况下,前保护器是侧向散射的主要来源,对任一点,前保护器的散射贡献均达到50%以上,并且侧向散射沿光轴方向呈递增或递减分布。在有侧向保护器情况下,侧向散射照射量有所减小,在与光轴垂直方向呈中间高两边低的单峰分布。增大侧向记录距离不一定带来侧向散射的降低。在适当的记录距离下,得到了较为均匀的散射分布。     

硅探测器的数字化脉冲形状甄别

介绍了利用硅探测器的脉冲形状甄别进行粒子鉴别的原理。详细叙述了基于数字化方法的脉冲形状甄别的实现。采样频率和位数是数字化方法的两个重要参数。对于硅探测器信号,采用100 MS/s,12 bit的Digitizer可以满足脉冲形状甄别法对时间分辨的要求。同时对该方法粒子鉴别的特征和能量阈值做了简要的分析和对比。粒子背面入射硅探测器的所得的阈值低于正面入射的情况。例如对于氖周围的同位素,背面入射情况的阈值约为100 MeV,为正面入射情况下鉴别阈值的二分之一,相当与ΔE-E方法中ΔE探测器厚度约为60 μm情况下的阈值。最后定性讨论了硅探测器的电阻率不均匀性和沟道效应对粒子鉴别性能的影响。In this paper Pulse Shape Discrimination(PSD) for silicon detector has been briefly introduced. The emerging digital method successfully applied to detector signal processing makes digital PSD method one of the most promising particle identification methods. Sampling frequency and the number of bits are two key parameters of digital method. For silicon detector signal, adopting 100 Ms/s, 12 bit Digitizer can satisfy the time resolution requirement of PSD method. The identification characteristic and energy threshold of this method have been discussed and compared with both front injection and rear injection cases. Energy threshold with rear injection usually is much lower than that with front injection. For example, around for Neon isotope energy threshold with rear injection is about 100 MeV which is only half of the threshold with front injection, also equivalent to thickness of about 60 μm silicon detector threshold in ΔE-E method. At the end the impact of silicon detector's resistivity nonuniformity and channel effect on the identification capacity of PSD method has been discussed in detail.     

Cell-like structure of unstable oblique detonation wave from high-resolution numerical simulation

A comprehensive numerical study was carried out to investigate the unsteady cell-like structures of oblique detonation waves (ODWs) for a fixed Mach 7 inlet flow over a wedge of 30° turning angle. The effects of grid resolution and activation energy were examined systematically at a dimensionless heat addition of 10. The ODW front remains stable for a low activation energy regardless of grid resolution, but becomes unstable for a high activation energy featuring a cell-like wave front structure. Similar to the situation with an ordinary normal detonation wave (NDW), a continuous increase in the activation energy eventually causes the wave-front oscillation to transit from a regular to an irregular pattern. The wave structure of an unstable ODW, however, differs considerably from that of a NDW. Under the present flow condition, triple points and transverse waves propagate downstream, and the numerical smoke-foil record exhibits traces of triple points that rarely intersect with each other. Several instability-driving mechanisms were conjectured from the highly refined results. Since the reaction front behind a shock wave can be easily destabilized by disturbance inherent in the flowfield, the ODW front becomes unstable and displays cell-like structures due to the local pressure oscillations and/or the reflected shock waves originating from the triple points. The combined effects of various instability sources give rise to a highly unstable and complex flow structure behind an unstable ODW front.     

工业CT图像边缘伪影校正

为了去除工业CT图像中的边缘伪影,提高CT图像的识别能力和尺寸测量精度,提出一种降低串扰的系数修正法。首先分析得出边缘伪影主要是由散射射线在相邻探测通道之间的串扰所导致,并给出了探测通道串扰的数学模型;然后根据数学模型设计实验方案,通过对影响串扰率的主要因素进行实验分析,得到串扰率随入射X射线能量和被测物体厚度变化关系,再通过最小二乘拟合得出投影数据关于串扰率的函数;最后利用此函数对投影数据进行校正,降低了串扰的影响。实验结果表明,探测器间一级串扰率约为9.0%,二级串扰率约为1.2%,其中一级串扰是造成边缘伪影的主要因素,采用本文方法能够有效地抑制边缘伪影,同时较好地保留了图像细节和边缘。