基于FPGA的数字反符合γ谱仪系统设计

本文设计了基于FPGA的数字反符合γ谱仪系统来降低天然本底和康普顿散射对低活度放射性测量的影响。该系统选用Φ145 mm×95 mm×80 mm的NaI （Tl）环形探测器与Φ75 mm×75 mm的NaI （Tl）主探测器构成反符合探测器,采用FPGA和高速ADC同步采样主探测器脉冲信号和反符合环形探测器输出信号。在FPGA中实现了核脉冲信号采集、缓存、反符合甄别、梯形成形等相关算法。在天然本底测量实验中,数字反符合γ谱仪系统的计数率为191.80 cps,本底抑制系数为2.69;对137Cs放射源的测量实验表明,在反符合探测器端面中心处,反符合测量峰总比为0.41,能量分辨率为6.99%;在反符合探测器侧面中间部位,反符合测量峰总比为0.30,能量分辨率为7.48%。实验结果表明,基于FPGA的数字反符合γ谱仪系统明显降低了天然环境本底和康普顿散射对测量的影响,适用于低活度放射性测量、现场就地放射性测量。     

不同响应波长的HgCdTe光导器件噪声分析

研究了不同响应波长的HgCdTe器件在不同背景辐射条件下的噪声变化.随着背景辐射的增加,甚长波器件的噪声减小,而中波器件相反.噪声频谱测量表明,产生-复合噪声分量和1/f噪声分量是器件的主要噪声来源,并且这两个分量随背景的变化趋势相同.非平衡载流子和器件有效寿命的理论分析,表明器件噪声随背景辐射的变化存在一个极大值,而中波和甚长波器件处在不同的作用区域内,接受到的背景辐射对载流子浓度和器件有效寿命的影响不同,从而噪声变化表现不同.在此基础上,提出了"临界背景通量密度"的概念.     

Measurement of radiation dose at the north interaction point of BEPCⅡ

The technique details for measuring radiation dose are expounded.The results of gamma and neutron radiation levels are presented and the corresponding radiation shielding is discussed based on the simplified estimation.In addition, the photon radiation level move as background for future experiments is measured by a NaI(T1) detector.     

红外小目标与背景辐射对比度的研究

红外目标与背景的对比度特征是红外探测系统检测的重要特征。研究了目标和背景在探测器上的辐射照度,提出了一种红外小目标与背景的辐射对比度,分析了该目标与背景对比度的相关因素。     

Mathematical modelling of the apparatus channel of an infrared remote sensing system

This paper presents a mathematical model of the apparatus channel of an infrared remote sensing radiometric system. The latter comprises: (1) the sounded object. This may be a medium, such as a cloud or a dense aerosol layer caused by a temperature inversion; (2) background radiation; (3) the atmospheric channel, or the medium where the signal radiation from the sounded object and the background radiations propagate; (4) the apparatus channel or the infrared radiometer itself. The system described is useful for investigating, measuring or controlling objects and media. The apparatus channel modelled is proposed as a lock-in detector. The joint action of all types of noise due to the stochastic nature of the infrared radiation or to the optoelectronic and electronic conversions is discussed. The final results allow calculation of the apparatus channel output signal-to-noise ratio.     

北京谱仪BES辐射本底水平的测定

北京谱仪BES辐射本底水平是由大厅内的辐射水平决定的.降低厅内的辐射水平是减少BES的辐射本底和提高BES探测效率和“信噪比”的重要途径.文中着重研究了谱仪厅内辐射本底的强度,来源及特点,并探讨了减少辐射的方法.     

基于蒙特卡罗方法的全身计数器设计研究

全身计数器用于对人体内照射污染的监测,对最小探测活度(MDA)有较高的要求。为使全身计数器具备较好的灵敏度,需要降低本底辐射和提高射线探测效率。基于MCNP5模拟了全身计数器中NaI探测器在不同几何位置时的能量响应,对探测器位置及准直器角度进行研究,同时对不同厚度的屏蔽结构进行了仿真计算分析。研究表明,当屏蔽钢板厚度为14.9 cm时,能够较大程度地降低本底辐射。在源探结构上探测腔准直器角度在26以上,探测器与体模的距离为20 cm时,能够得到理想的能谱响应和探测效率。     

Radiation monitoring of the GEM muon detectors at CMS

The higher energy and luminosity of future High Luminosity (HL) LHC, determines a significant increasing of the radiation background around the CMS subdetectors, and especially in the higher pseudorapidity region. Under such heavy conditions, the RPC (used in muon trigger) most probably could not operate effectively. GEM (Gas Electron Multiplier) detectors have been identified as a suitable technology to operate in the high radiation environment in that region and test at CMS will start in 2016. A monitoring system to control the absorbed radiation dose by the GEM under test is developed. Two types of sensors are used in it: RadFETs for total absorbed dose and p-i-n diodes for particle (proton and neutron) detection. The basic detector unit, called RADMON, contains two sensors of each type and can be installed at each GEM detector. The system has a modular structure, permitting to increase easily the number of controlled RADMONs: one module controls up to 12 RADMONs, organized in three group of four and communicates outside by RS 485 and CANBUS interfaces.     

太阳对成像型天基激光告警系统的影响

针对成像型天基激光告警系统中的太阳背景辐射问题,通过理论分析和数值计算研究了太阳与系统探测器不同空间位置关系时直射太阳光和地球反射太阳光对系统成像信噪比、威胁激光检测、探测器自身安全的影响.结果表明:太阳光是天基激光告警系统的主要背景辐射,地球反射太阳光是系统红外探测器成像的主要背景光|反射太阳光辐照在探测器像面上的最大能量密度为0.97 mJ/cm2,反射太阳光背景下,攻击激光成像信噪比在103以上,信标激光信噪比小于1,反射太阳光对攻击激光检测没有影响,对信标激光成像是强背景干扰|直射太阳光辐照探测器是系统不可避免的情况,太阳成像光斑功率密度最大时约20 W/cm2,将导致探测器像元饱和甚至损坏|太阳成像光斑特征与入射激光相似,会造成系统严重虚警.     

A simple pyroelectric power meter for the FIR range

Pyroelectric detectors are simple and rugged devices for measuring radiation from UV to Millimeter waves. In this paper a pyroelectric power meter using stock components is described. It offers some features as internal chopper background radiation compensation or calibrated detector efficiency control usually not found in commercial instruments. Calibration data at various FIR frequencies are also given.     

CERN@school: demonstrating physics with the Timepix detector

This article shows how the Timepix hybrid silicon pixel detector, developed by the Medipix2 Collaboration, can be used by students and teachers alike to demonstrate some key aspects of any well-rounded physics curriculum with CERN@school. After an overview of the programme, the detector’s capabilities for measuring and visualising ionising radiation are examined. The classification of clusters – groups of adjacent pixels – is discussed with respect to identifying the different types of particles. Three demonstration experiments – background radiation measurements, radiation profiles and the attenuation of radiation – are described; these can used as part of lessons or as inspiration for independent research projects. Results for exemplar data-sets are presented for reference, as well as details of ongoing research projects inspired by these experiments. Interested readers are encouraged to join the CERN@school Collaboration and so contribute to achieving the programme’s aim of inspiring the next generation of scientists and engineers.     

Beam energy measurement system at BEPC Ⅱ

The beam energy measurement system at BEPCII is composed of there parts: laser source and optics system,laser-electron interaction system and High Purity Germanium(HPGe)detector system.The special components and construction of each part are introduced,especially about radiation background mea-surement in the storage ring,which is of great importance for the safe commissioning of HPGe detector.     

Silicon photodiodes as Thomson scattering detectors in experiments on the Tuman-3M tokamak and in bench experiments

Experiments on Thomson scattering in the Tuman-3M tokamak plasma with silicon photodiodes applied as radiation detectors are performed. Bench tests and numerical simulation are used to compare the efficiency of detector modules based on conventional and avalanche photodiodes in recording weak pulses of various durations against uniform background light. When the pulse duration increases to several hundreds of nanoseconds, the increase in sensitivity due to avalanche gain disappears. This is of importance for diagnosing the tokamak plasma, where the background radiation is relatively intense.     

Study of beamstrahlung effects at CEPC

The discovery of a 125 GeV Higgs boson at the LHC marked a breakthrough in particle physics. The relative lightness of the new particle has inspired consideration of a high-luminosity Circular Electron Positron Collider(CEPC) as a Higgs Factory to study the particle's properties in an extremely clean environment. Given the high luminosity and high energy of the CEPC, beamstrahlung is one of the most important sources of beaminduced background that might degrade the detector performance. It can introduce even more background to the detector through the consequent electron-positron pair production and hadronic event generation. In this paper,beamstrahlung-induced backgrounds are estimated with both analytical methods and Monte Carlo simulation. Hit density due to detector backgrounds at the first vertex detector layer is found to be~0.2 hits/cm~2 per bunch crossing, resulting in a low detector occupancy below 0.5%. Non-ionizing energy loss(NIEL) and total ionizing dose(TID), representing the radiation damage effects, are estimated to be~10~(11)1 Me V neq/cm~2/yr and~300 k Rad/yr,respectively.     

消除强背景辐射干扰的光电探测新方法

 以InSb探测器(PV型)为例, 通过建立载流子输运的动力学模型得到光生电动势与入射光功率密度的函数关系, 提出了一种消除强背景辐射对光电探测的影响的新方法, 并且通过实验证实了这种方法的有效性及其理论模型的合理性。与传统的调零法相比, 该方法精度较高且能适用于更高强度的背景辐射 。     

超高灵敏度太赫兹超导探测技术发展

太赫兹波段占有宇宙微波背景(CMB)辐射以后宇宙空间近一半的光子能量,该波段在天文学研究中具有不可替代的作用,因此太赫兹天文学的研究,具有极其重要的科学意义。本文系统介绍了基于超高灵敏度太赫兹超导探测技术的太赫兹相干探测器发展状况,包括超导隧道结混频器(SIS)和超导热电子混频器(HEB),以及以超导动态电感探测器(MKIDs)和超导相变边缘探测器(TES)为代表的非相干探测器的研究。在此基础上,展望了该领域未来发展趋势,对我国太赫兹天文探测技术的发展具有一定的参考意义。     

Simulation of natural radioactivity backgrounds in the JUNO central detector

The Jiangmen Underground Neutrino Observatory(JUNO) is an experiment proposed to determine the neutrino mass hierarchy and probe the fundamental properties of neutrino oscillation.The JUNO central detector is a spherical liquid scintillator detector with 20 kton fiducial mass.It is required to achieve a 3%/E(MeV)~(1/2) energy resolution with very low radioactive background,which is a big challenge to the detector design.In order to ensure the detector performance can meet the physics requirements,reliable detector simulation is necessary to provide useful information for the detector design.A simulation study of natural radioactivity backgrounds in the JUNO central detector has been performed to guide the detector design and set requirements for the radio-purity of the detector materials.The accidental background induced by natural radioactivity in the JUNO central detector is 1.1/day.The result is satisfied for the experiment.     

An estimation of EDXRF spectrometer properties,based on a two‐layer composite Si‐Ge detector

A mathematical model for the two‐layer composite Si‐Ge energy dispersive X‐ray detector is proposed, based on analyses of radiation and electron transport in the detector, and a mathematical model of an energy dispersive X‐ray fluorescent spectrometer with the detector is considered. The Monte Carlo method is applied to calculate probabilities of photon detection in different parts of the detector's response function. The composite detector with the time anti‐coincidence scheme is proposed; its first layer is Si detector, and the second layer is Ge detector. It is shown that this composite detector has some advantages, such as reduced Ge photo escape peaks intensities and efficiency of detection of high energy photons similar to efficiency of Ge detector. Applying the X‐ray detector for the energy dispersive X‐ray fluorescent spectrometer provides for a lower background level. Copyright © 2012 John Wiley & Sons, Ltd.     

FLUKA Monte Carlo simulation code as used for radiation studies in the Alice experiment

The main features of the FLUKA Monte Carlo code, which can deal with transport and interaction of electromagnetic and hadronic particles, are summarized. The physical models embedded in FLUKA are described. Application of the code for the radiation background calculations. Especially, the origin and composition of the intense radiation field to be expected in parts of the ALICE detector for the coming multi-TeV LHC collider is described. It is important to evaluate the risk of radiation damage in detectors and electronics equipment. The text was submitted by the author in English.     

Quantitative performance measurements of bent crystal Laue analyzers for X‐ray fluorescence spectroscopy

Third‐generation synchrotron radiation sources pose difficult challenges for energy‐dispersive detectors for XAFS because of their count rate limitations. One solution to this problem is the bent crystal Laue analyzer (BCLA), which removes most of the undesired scatter and fluorescence before it reaches the detector, effectively eliminating detector saturation due to background. In this paper experimental measurements of BCLA performance in conjunction with a 13‐element germanium detector, and a quantitative analysis of the signal‐to‐noise improvement of BCLAs are presented. The performance of BCLAs are compared with filters and slits.