公共格栅像素CdZnTe探测器的能谱特性

使用同一块CdZnTe晶体设计制作了像素大小不等的44公共格栅像素CdZnTe探测器。通过能谱测定实验及权重势和电场仿真,研究了公共格栅像素CdZnTe探测器中的小像素效应和引导效应。结果表明：由于小像素效应较弱,较大的像素不能有效消除空穴拖尾,能谱特性较差;由于晶体内部以及像素和公共格栅间隙表层的电荷损失,较小的像素能谱特性也较差。在像素宽度为0.8 mm时,得到了对662 keV的137Cs放射源的最佳能量分辨率3.80%和峰谷比5.65。适当增大公共格栅偏压可以引导电子向阳极像素运动,促进电荷的完全收集,改善探测器的能谱特性。过大的偏压则会造成像素和公共格栅间表面漏电流的增加,探测器的能谱特性也会恶化。在像素宽度为0.8 mm时最佳偏压为-60 V。     

公共格栅像素CdZnTe探测器的能谱特性

使用同一块CdZnTe晶体设计制作了像素大小不等的4×4公共格栅像素CdZnTe探测器。通过能谱测定实验及权重势和电场仿真,研究了公共格栅像素CdZnTe探测器中的小像素效应和引导效应。结果表明:由于小像素效应较弱,较大的像素不能有效消除"空穴拖尾",能谱特性较差;由于晶体内部以及像素和公共格栅间隙表层的电荷损失,较小的像素能谱特性也较差。在像素宽度为0.8 mm时,得到了对662keV的137Cs放射源的最佳能量分辨率3.80%和峰谷比5.65。适当增大公共格栅偏压可以引导电子向阳极像素运动,促进电荷的完全收集,改善探测器的能谱特性。过大的偏压则会造成像素和公共格栅间表面漏电流的增加,探测器的能谱特性也会恶化。在像素宽度为0.8mm时最佳偏压为-60V。     

碲锌镉面元辐射探测器堆积载流子屏蔽效应

 采用铑(Rh)靶45 kV X射线源进行了碲锌镉(CdZnTe)面元像素阵列探测器成像实验。实验结果表明：在探测距离1 mm,管电压45 kV条件下,管电流增大至20 μA时,辐照中心区域像素单元信号丢失,出现围绕辐照中心区域的边缘高事件计数环形探测图像。随着管电流的增大,无响应像素区域扩大,探测器总体事件计数明显降低。进一步根据泊松方程建立了CdZnTe晶体内部电势分布模型,仿真结果表明：单位面积光子通量为5×10⁵ mm^-2·s^-1时,由于CdZnTe晶体较低的空穴迁移率,晶体内部存在堆积空穴载流子形成的高空间电荷密度分布区域。晶体内部电场产生扭曲,电子载流子无法迁移至对应阳极位置,导致辐照中心区域产生信号屏蔽效应。     

碲锌镉面元辐射探测器堆积载流子屏蔽效应

采用铑(Rh)靶45 kV X射线源进行了碲锌镉(CdZnTe)面元像素阵列探测器成像实验。实验结果表明：在探测距离1 mm,管电压45 kV条件下,管电流增大至20 μA时,辐照中心区域像素单元信号丢失,出现围绕辐照中心区域的边缘高事件计数环形探测图像。随着管电流的增大,无响应像素区域扩大,探测器总体事件计数明显降低。进一步根据泊松方程建立了CdZnTe晶体内部电势分布模型,仿真结果表明：单位面积光子通量为5×105 mm-2·s-1时,由于CdZnTe晶体较低的空穴迁移率,晶体内部存在堆积空穴载流子形成的高空间电荷密度分布区域。晶体内部电场产生扭曲,电子载流子无法迁移至对应阳极位置,导致辐照中心区域产生信号屏蔽效应。     

CdZnTe像素探测器的电输运性能

碲锌镉(CdZnTe)是一种性能优异的室温核辐射半导体探测器材料,广泛应用于核安全、核医学以及空间科学等领域.然而,传统的CdZnTe平面探测器受制于"空穴拖尾"效应的影响,探测性能有待改善.采用改进的垂直布里奇曼法生长的In掺杂Cd_(0.9)Zn_(0.1)Te单晶制备出单载流子收集的4×4像素阵列探测器,通过电流-电压(I-V)测试和γ射线能谱响应测试,研究了像素探测器的电学性能和载流子电输运性能,随之与相应的CdZnTe平面探测器进行了性能对比.结果表明,CdZnTe像素探测器的电阻率约为1.73×10~(10)?·cm,且施加100 V偏压后单像素点的最大漏电流小于2.2 nA;当施加偏压升高至300 V时,单像素点对~(241)Am@59.5 keV的γ射线的最佳能量分辨率可达5.78%,探测性能优于相同条件下制备的CdZnTe平面探测器.     

Response function of the CdZnTe SPEAR detector

The response function of the SPEAR CdZnTe detector developed by eV Microelectronics was studied in detail. This compact detector includes a CdZnTe crystal and a preamplifier. It is operational at room temperature. The energy range of the detector is between 10 keV and 1 MeV, and its relative resolution is less than 4% at 122 keV. The goal of our study was to establish an empirical analytical approximation of the response function to be used in Monte Carlo simulations (e.g. for spectrum unfolding). Various radionuclides were used for the study. The energy spectrum obtained from the detector not only showed smooth peaks but also had a tail on the low‐energy side of the peak. This tail part was more prominent at higher energies. By using the experimental spectrum for various nuclides such as ²⁴¹Am, ¹⁰⁹Cd, ⁵⁷Co and ¹³⁷Cs, the parameters required to replicate the experimental response with a peak plus exponential model were evaluated. Copyright © 2011 John Wiley & Sons, Ltd.     

超导转变边沿单光子探测器原理与研究进展

量子信息技术近十多年来的快速发展对单光子探测器的性能提出了更高的要求,高性能单光子探测器也因此受到了更多的关注.与传统的单光子探测器相比,超导转变边沿(TES)单光子探测器在探测效率、能量分辨、光子数分辨和暗计数等方面具有突出优势.目前,超导TES单光子探测器已经被成功地应用在量子光学实验和量子密钥分配系统中,未来在量子信息技术等研究领域具有更广泛的应用.本文从超导TES单光子探测器的工作原理、制备流程、测试系统、主要性能指标以及研究现状和进展等方面对该探测器技术进行简要综述.     

Influence of sub-bandgap illumination on space charge distribution in CdZnTe detector

The space charge accumulation in CdZnTe crystals seriously affects the performance of high-flux pulse detectors.The influence of sub-bandgap illumination on the space charge distribution and device performance in CdZnTe crystals were studied theoretically by Silvaco TCAD software simulation.The sub-bandgap illumination with a wavelength of 890 nm and intensity of 8×10?8 W/cm2 were used in the simulation to explore the space charge distribution and internal electric field distribution in CdZnTe crystals.The simulation results show that the deep level occupation faction is manipulated by the sub-bandgap illumination,thus space charge concentration can be reduced under the bias voltage of 500 V.A flat electric field distribution is obtained,which significantly improves the charge collection efficiency of the CdZnTe detector.Meanwhile,premised on the high resistivity of CdZnTe crystal,the space charge concentration in the crystal can be further reduced with the wavelength of 850 nm and intensity of 1×10?7 W/cm2 illumination.The electric field distribution is flatter and the carrier collection efficiency of the device can be improved more effectively.     

双层并联碲锌镉探测器制备及性能测试

实验采用并联方法制备了叠层(双层)碲锌镉探测器,并利用²⁴¹Am@59.54 keV和⁵⁷Co@122 keV γ射线源测试了其γ能谱特性。相比单层探测器,对于较高能量的⁵⁷Co@122 keV γ射线,叠层碲锌镉探测器表现出较高的探测效率和光峰值效率,较好地改善了康普顿连续统一体。叠层CZT探测器较之单层探测器,能谱分辨率发生轻微恶化。实验初步表明,通过并联叠加方法制备叠层碲锌镉探测器是可行的,并可推断制备更大厚度的叠层探测器将有利于中高能γ射线能谱测量。     

高能伽玛源下碲锌镉探测器的针孔成像

采用新型室温碲锌镉(CdZnTe)辐射探测器,通过厚针孔系统对137Cs高能662 keV伽玛射线辐射源进行成像探测,得到了能谱图和放射源图像。计算分析了高能射线穿透效应对空间分辨力的影响,并对不同偏压下得到的图像进行比较与讨论。实验表明,当放大倍率不大时（小于3）,高能射线对准直器材料的穿透效应增大是限制图像空间分辨力的主要因素,探测器像素尺寸的大小对图像空间分辨力的影响并不明显。随偏置电压升高,探测器得到的图像会得到改善,但过大的偏压（大于1 000 V）会使晶体内部的电场不均匀性增大,降低信噪比从而降低图像品质。     

Temporal pulsed x-ray response of CdZnTe:In detector

The temporal response of cadmium-zinc-telluride(CZT) crystals is evaluated at room temperature by using an ultrafast-pulsed x-ray source. The dynamics of carrier relaxation in a CZT single crystal is modeled at a microscopic level based on a multi-trapping effect. The effects of the irradiation flux and bias voltage on the amplitude and full width at half maximum(FWHM) of the transient currents are investigated. It is demonstrated that the temporal response process is affected by defect level occupation fraction. A fast photon current can be achieved under intense pulsed x-ray irradiation to be up to 2.78×10~9 photons mm~(-2)·s~(-1). Meanwhile, it is found that high bias voltage could enhance carrier detrapping by suppressing the capture of structure defects and thus improve the temporal response of CZT detectors.     

Effect of surface preparation technique on the radiation detector performance of CdZnTe

Synthetic CdZnTe (CZT) semiconducting crystals are highly suitable for the room temperature-based detection of gamma radiation. The surface preparation of Au contacts on surfaces of CZT detectors is typically conducted after (1) polishing to remove artifacts from crystal sectioning and (2) chemical etching, which removes residual mechanical surface damage however etching results in a Te rich surface layer that is prone to oxidize. Our studies show that CZT surfaces that are only polished (as opposed to polished and etched) can be contacted with Au and will yield lower surface currents. Due to their decreased dark currents, these as-polished surfaces can be used in the fabrication of gamma detectors exhibiting a higher performance than polished and etched surfaces with relatively less peak tailing and greater energy resolution.     

CdZnTe像素阵列探测器成像评价模型及实验

考虑载流子陷获效应建立了碲锌镉(CdZnTe)像素阵列探测器感应电荷分布模型,并从非平衡载流子连续方程出发,推导了晶体内部陷获载流子数密度分布,得到了CdZnTe探测器成像调制传递函数评价模型。数值计算结果表明：随入射光子能量的增加,探测器成像质量明显下降;当电子载流子与空穴载流子迁移寿命积范围分别为0.510-3 to 5.010-3 cm2/V,2.010-5 to 7.510-5 cm2/V时,电子载流子感应信号是探测器响应信号的主要来源,而空穴迁移寿命积变化对探测器成像性能的影响有限,所建立模型的载流子收集特性与实际探测器载流子收集特性相符。搭建了40 mm40 mm的CdZnTe成像探测系统,探测并获得了系统预采样调制传递函数。实验结果表明:模型理论值与实验数据相符合,实际CdZnTe晶体中存在的固有深能级缺陷、实验所采用的非单色性X射线源及较大的实际像素间隙是造成理论值与实验结果存在一定偏差的主要原因。     

Tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber

Optical fiber temperature sensors have been widely employed in enormous areas ranging from electric power industry, medical treatment, ocean dynamics to aerospace. Recently, graphene optical fiber temperature sensors attract tremendous attention for their merits of simple structure and direct power detecting ability. However, these sensors based on transfer techniques still have limitations in the relatively low sensitivity or distortion of the transmission characteristics, due to the unsuitable Fermi level of graphene and the destruction of fiber structure, respectively. Here, we propose a tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber (Gr-PCF) with the non-destructive integration of graphene into the holes of PCF. This hybrid structure promises the intact fiber structure and transmission mode, which efficiently enhances the temperature detection ability of graphene. From our simulation, we find that the temperature sensitivity can be electrically tuned over four orders of magnitude and achieve up to ～ 3.34×10^-3 dB/(cm·℃) when the graphene Fermi level is ～ 35 meV higher than half the incident photon energy. Additionally, this sensitivity can be further improved by ～ 10 times through optimizing the PCF structure (such as the fiber hole diameter) to enhance the light-matter interaction. Our results provide a new way for the design of the highly sensitive temperature sensors and broaden applications in all-fiber optoelectronic devices.     

基于CdZnTe像素阵列探测技术的伽玛源成像

根据高能射线针孔成像理论,采用CdZnTe像素阵列探测器建立了直接成像探测模式的伽玛源针孔探测系统。测试分析了CdZnTe像素阵列探测器的能量分辨力及峰值效率,讨论研究了针孔成像探测系统的调制传递函数和附加噪声特性,测试获得直径5 mm137Cs源的探测图像,采用Lucy-Richardson迭代算法得到了137Cs源的复原图像。实验结果表明:CdZnTe探测器对662 keV137Cs源的能量分辨力为6.25%～7.50%,峰值效率65.0%～72.5%;成像系统探测图像存在一定扩散现象,所采用的Lucy-Richardson迭代复原算法能较好地修正图像扩散,提高探测图像中心区域细节分辨力;估算所得137Cs源尺寸误差约0.5 mm,所建立的CdZnTe针孔成像探测系统能有效得到小尺寸伽玛源的辐照强度分布及尺寸信息。     

基于CdZnTe像素阵列探测技术的伽玛源成像

根据高能射线针孔成像理论,采用CdZnTe像素阵列探测器建立了直接成像探测模式的伽玛源针孔探测系统。测试分析了CdZnTe像素阵列探测器的能量分辨力及峰值效率,讨论研究了针孔成像探测系统的调制传递函数和附加噪声特性,测试获得直径5mm137Cs源的探测图像,采用Lucy-Richardson迭代算法得到了137Cs源的复原图像。实验结果表明:CdZnTe探测器对662keV137Cs源的能量分辨力为6.25%～7.50%,峰值效率65.0%～72.5%;成像系统探测图像存在一定扩散现象,所采用的Lucy-Richardson迭代复原算法能较好地修正图像扩散,提高探测图像中心区域细节分辨力;估算所得137Cs源尺寸误差约0.5mm,所建立的CdZnTe针孔成像探测系统能有效得到小尺寸伽玛源的辐照强度分布及尺寸信息。     

一种基于自相关函数的幂律检测器

针对水下高斯噪声中非高斯瞬态信号的检测问题,在研究Nuttall提出的power-law(幂律)检测器的基础上,为了提高其检测性能,依据信号和噪声的自相关函数的差异,提出了基于自相关函数的power-law检测器,并对其参数的最佳选取及检测性能进行了仿真研究。仿真结果表明,基于自相关函数的检测器较基于DFT的power-law检测器性能有所提高,有一定的可行性。     

一种基于~4He气闪烁体的裂变中子探测器

研制了一种新中子探测器,它以²³⁵UO₂裂变靶作为转换靶,⁴He气体作为闪烁体.该探测器充分结合了²³⁵U和⁴He两种核素的特点,从而具有中子能量响应平坦、中子灵敏度较高、n/γ分辨本领高等优点,能很好地在混合脉冲裂变辐射场中测量中子.本文对探测器的原理和结构设计进行了介绍,计算了不同能量中子、γ射线在探测器中的能量沉积,并从理论和实验上对探测器的中子灵敏度、γ射线灵敏度、n/γ分辨本领和时间响应进行了研究.结果表明探测器的中子灵敏度约10^-15C·cm²,γ灵敏度约10^-17C·cm²,时间响应约33.1 ns.     

A new configuration of the Moxon–Rae detector based on Si detector

A new Moxon–Rae detector configuration based on Si semiconductor detector was proposed in this paper. Three γ-ray sources, ¹³⁷Cs, ⁶⁰Co, and ²⁴Na, were employed to make actual measurements using the new Moxon–Rae detector. The measured pulse height spectra and detection efficiencies were compared with the EGS4 simulated values. The results revealed that the proposed new configuration is indeed a successful method and specially a useful technique for higher energy γ-ray measurement.     

A neutron sensor based on superheated droplets

The neutron sensor based on superheated droplets, developed in the U.S.A. and U.K., is one of the most attractive techniques at present for neutron radiation dosimetry. Limited shelf life, i.e. six months (BTI, U.K.), and the dependence of neutron response on climatic conditions are some of the problems associated with these sensors. The development of the above type of sensor suitable for tropical conditions is therefore required. The authors have begun to develop such sensors. The preliminary results show a lower limit of detection of 10 μSv for an ²⁴¹Am-Be neutron source and a linear response from 10 μSv to 1 mSv has been reported.