A SCINTILLATION COUNTER HODOSCOPE AND ON-LINE EXPERIMENTS WITH COMPUTER

In this paper, a multi-strip scintillation counter hodoscope and a small on-line system are described. The hodoscope is a 4×4 array of scin tillation strip counter, each of which consists of a plastic scintillation strip of type NE104 with the dimension of 50×4×1cm³ and a Photomultiplier of type GDB-50L. An on-line program for hodoscope property test has been compiled. The hodoscope read-out system is linked with PDP-11/03 computer and with them some on-line experiments have been done.
The experimental results are as follows. The efficiency of each cell of the hodoscope is between 96.5% and 99.5%. The counting distribution caused by a radiative source Ru¹⁰⁶ put at various locations can be displayed as a histogram directly and promptly on a printer. The intensity of cosmic ray fluxes and its distribution versus azimuthal angle has been measured. All these results are reasonable. The performances of this system are well and stable and it can be used in some experiments of high energy physics.     

补充加料过程中逃逸电子的雪崩现象

在靶丸注入和超声分子束注入等补充加料期间，虽然等离子体密度骤然增加，但用五通道碘化汞探测器阵列及碘化钠探测器在此期间均测到很强的X射线辐射，且射线峰爆发时间与靶丸注入及超声分子束注入时间对应得相当好，用二次电子发射形成雪崩型逃逸电子理论解释了实验测量结果。     

Role of guard rings in improving the performance of silicon detectors

BARC has developed large-area silicon detectors in collaboration with BEL to be used in the pre-shower detector of the CMS experiment at CERN. The use of floating guard rings (FGR) in improving breakdown voltage and reducing leakage current of silicon detectors is well-known. In the present work, it has been demonstrated that FGRs can also be used to improve the spectroscopic response of silicon detectors. The results have been confirmed by carrying outα-particle (≈5 MeV) andγ-ray (60 keV) spectroscopies with the FGR floating or biased and the underlying physics aspect behind the change in spectra is explained. Although reduction in leakage current after biasing one of the guard rings has been reported earlier, the role of a guard ring in improving the spectroscopic response is reported for the first time. Results of TCAD simulations for silicon detectors with the guard ring under different biasing conditions have been presented. Low yield in producing large-area silicon detectors makes them very costly. However, with one of the FGRs biased even a detector having large surface leakage current can be used to give the same response as a very good detector. This makes the use of large-area silicon detectors very economical as the yield would be very high (>90%).     

Effect of gamma energy, temperature and shelf life on the response of gamma and BD-100R neutron bubble detectors

The use of commercially available bubble detectors for gamma and neutron detection has been reported by several groups. We have carried out systematic investigations to study the response of gamma bubble detector as a function of energy, the effect of waiting time on sensitivity of BD-100R neutron bubble detector and the effect of shelf life on both types of bubble detectors. Our results show that the response of the gamma bubble detector is energy dependent. Waiting time of up to 260 hours for BD-100R neutron detector has no significant effect. Both the detectors have a limited shelf life. These factors must be taken into account while using these detectors.     

Dark current transport mechanism associated with acceptor concentration in GaAs-based blocked-impurity-band (BIB) detectors

Dark current transport mechanism associated with acceptor concentration in GaAs-based blocked-impurity-band (BIB) detectors has been investigated. Device structure, numerical models and simulation techniques are described in detail. By careful model and parameter calibration, the numerical simulation is completely consistent with the analytical calculation, proving the validity of simulation methods. Our results reveals that the carrier-transport modes of GaAs-based BIB detectors can be classified into two categories (i.e., electron current and hopping current), and the hopping current can be neglected compared with the electron current. Besides, it is demonstrated that the dark current of GaAs-based BIB detector is dominated by the drift–diffusion current and the generation-recombination current, and the both current components are monotonically decreasing functions of the acceptor concentration.     

高增益型气体电子倍增微网结构探测器的性能研究

随着微结构气体探测器的不断发展, 不同的探测需求相继提出.为了实现气体探测器在高增益和低打火率的条件下长时间稳定工作, 结合气体电子倍增器(GEM)与微网结构气体探测器(MicroMegas)的探测优势, 成功研制出一种基于GEM作为预放大的MicroMegas探测器, 详细介绍了探测器结构和工作原理, 并利用⁵⁵Fe放射源对探测器增益、打火率、能量分辨和工作稳定性等性能进行了实验测量. 分析结果显示GEM-MicroMegas探测器可以连续工作30 h 以上, 探测器增益可以超过10⁶, 相对于无GEM膜的MicroMegas探测器, 相同增益下打火率可以降低近100倍. 关键词： 微网结构气体探测器 能量分辨率 增益 打火率     

微结构气体探测器中紫外激光束的信号和指向精度实验研究

在气体探测器研究中,利用266 nm紫外激光的双光子电离物理机制使气体电离产生可测量的信号,是一种重要的标定方法.随着微结构气体探测器(MPGD)的不断发展,用紫外激光标定来实现较高精度位置分辨率成为了一种研究需求,对此有两个关键技术问题需要解决:实验研究激光可测信号大小以及激光指向精度.分析和模拟计算了紫外光电离信号大小和激光调光误差,基于微结构气体电子倍增器探测器与266 nm波长激光束,在工作气体Ar/CO_2(70/30)中,测量了不同光斑面积与输出信号的关系;设计和研制了紫外激光调光系统,实验测量了紫外光调光偏差.模拟结果与实验结果对比分析表明:紫外激光束作用于气体探测器,探测器增益在5000,前放增益为10 mV/fC时, 6 mm读出条宽输出信号幅度约400 mV;在探测器内传播距离为400 mm时,较短时间内(10—20 min)实验调光指向精度可以保证小于5′,引入z向偏差最大可以达到0.33 mm,对应z向漂移速度的测量相对误差为6.4×10-4.该研究为MPGD与紫外激光标定实验设计提供主要的设计参考.     

基于GEANT4的CsI(Tl)闪烁体探测器的Monte Carlo模拟

对闪烁光在晶体内的传输以及光电子倍增过程进行了建模,基于GEANT4软件包对CsI(T1)闪烁体探测器进行了蒙特卡罗模拟, 得到了不同形状、尺寸和包装的CsI(Tl)晶体测量γ射线的能谱。对比模拟和测试结果,两者得到了很好的符合,从而验证了模拟参数的合理性和可靠性。该模拟程序的建立为闪烁体探测器的设计提供了更精确的开发工具。 With the modeling of the light transportation in crystal and electron multiplication in the PMT, a Monte Carlo simulation of CsI(Tl) scintillator detector has been implemented with Geant4 toolkit. The energy spectra simulated with different crystal shape, size and wrappings are obtained. And the reliability of the simulation parameters is confirmed by comparing with the measurements. The simulation code can be used as an reliable tool for the design of scintillator detectors.     

Silicon detector technology development in India for the participation in international experiments

A specific research and development program has been carried out by BARC in India to develop the technology for large area silicon strip detectors for application in nuclear and high energy physics experiments. These strip detectors will be used as pre-shower detector in the CMS experiment at LHC, CERN for π ⁰/λ rejection. The fabrication technology to produce silicon strip detectors with very good uniformity over a large area of ∼40 cm², low leakage currents of the order of 10 nA/cm² per strip and high breakdown voltage of >500 V has been developed by BARC. The production of detectors is already under way to deliver 1000 detector modules for the CMS and 90% production is completed. In this paper, research and development work carried out to develop the detector fabrication technology is briefly described. The performance of the silicon strip detectors produced in India is presented. The present status of the detector technology is discussed.      

Wide-aperture muon detector for diagnostics of the Earth’s atmosphere and magnetosphere

A wide-aperture large-area multilayered muon hodoscope is being constructed above the water Cherenkov calorimeter NEVOD (Moscow Engineering Physics Institute). This hodoscope is aimed at studying the processes in the Earth’s atmosphere and magnetosphere that lead to variations in the muon flux at the ground level. The structure of the detector and its data acquisition and triggering systems are described. Some preliminary results of the analysis of the data obtained using the first two supermodules of the system in the continuous series of measurements during 2005–2006 are discussed.     

Specific features of studying Forbush decreases in the muon flux

The variations in the cosmic ray (CR) muon flux during the Forbush decreases (FDs), registered by the DECOR muon detector and the URAGAN muon hodoscope during the periods of their operation from 2004 to 2006, are analyzed. The unified method for determining the parameters of variations in the CR flux during FDs has been developed, and the dependences of the FD characteristics on the rigidity of primary CRs and information about the spatial-angular dynamics of the muon flux during FDs have been obtained.     

Discriminating cosmic muons and X-rays based on rise time using a GEM detector

Gas electron multiplier(GEM) detectors have been used in cosmic muon scattering tomography and neutron imaging over the last decade.In this work,a triple GEM device with an effective readout area of 10 cm x10 cm is developed,and a method of discriminating between cosmic muons and X-rays based on rise time is tested.The energy resolution of the GEM detector is tested by ~(55)Fe ray source to prove the GEM detector has a good performance.Analysis of the complete signal-cycles allows us to get the rise time and pulse heights.The experiment result indicates that cosmic muons and X-rays can be discriminated with an appropriate rise time threshold.     

Spectral measurement of weak THz waves with quantum Hall detectors

A terahertz (THz) microspectroscope is developed, in which the frequency of extremely weak THz radiation is resolved by scanning the magnetic field for a quantum Hall detector. The electron density of the detectors is controlled by the back-gate biasing, so that the detector sensitivity is calibrated over a spectral range studied. Reliable spectral measurements with a spectral resolution of 1.2 cm⁻¹ has been made with a sensitivity better than 10 femtowatt level over 1 s integration time.     

ANSYS在气体探测器电场分布计算中的应用

介绍了气体探测器电场分布的计算方法,以计算MSGC探测器单元电场分布为例说明了如何用ANSYS软件包来计算结构较复杂的气体探测器内部电场分布,同时讨论了电场分布对气体探测器性能的影响.     

双层深度编码探测器的晶体表面优化

设计了双层LSO晶体和位置灵敏型光电倍增管耦合构成的用于小动物PET成像的 深度编码探测器. 众所周知, 晶体的不同的表面处理影响着光输出量, 进而影响着它们构建的PET探测器的性能. 为了优化设计的深度编码探测器的性能, 测试了两种不同表面处理的LSO闪烁晶体阵列探测器的晶体分辨能力及其能量、时间和空间分辨率, 结果表明, 光滑表面LSO晶体构建的深度编码探测器显示出良好的空间、能量及时间分辨特性.     

光子计数位置灵敏探测器畸变多项式校正

采用多项式校正方法对光子计数位置灵敏探测器成像畸变进行校正。介绍光子计数位置灵敏探测器工作原理并分析其畸变产生原因;介绍多项式校正原理,并给出光子计数位置灵敏探测器畸变多项式校正流程;采用该方法对两种不同畸变程度的基于楔条形阳极该类探测器进行了畸变校正,校正后残余误差分别为2.5pixel和1.2pixel。实验结果表明,多项式校正法能够有效校正光子计数位置灵敏探测器成像畸变。     

波段外激光辐照PC型探测器的反常响应机制

 提出了PC型半导体探测器对波段外激光辐照的热电子光电导响应机制。响应波段外激光辐照PC型半导体探测器时，探测器有响应且输出电压信号迅速增大，与波段内激光辐照时的响应规律截然不同，这是由光激发能带内热电子而引起的光电导现象。当较强功率的激光辐照时还应考虑热效应。依据该机制进行了模拟计算，计算结果表明当PC型HgCdTe探测器被波段外激光辐照时，热电子的产生使得电导率减小，进而导致探测器的电阻增大。     

Detection of a single electron in xenon-based electroluminescent detectors

It is experimentally shown that a single ionization electron can be detected by various xenon-based electroluminescent detectors with optical readout, such as a high-pressure cylindrical gas counter, a two-phase detector with gas amplification, and a two-phase detector with a plane-parallel and uniform electric field. The sensitivity of the detectors was 7, 18, and 15 photoelectrons respectively. The coordinate resolution of the two-phase detector for electrons resulting from field emission at the cathode was σ _X,Y = 5.2 mm.     

Processes in Geophysics Studied by Mössbauer Spectroscopy

Time Differential gamma–gamma Perturbed Angular Correlation spectroscopy has traditionally been done using scintillation detectors along with constant–fraction discriminators, spectroscopy amplifiers, single channel analyzers, and time to amplitude detectors. We describe a new generation spectrometer where these electronics are replaced by high speed digital transient recorders that record the output from each scintillation detector. The energy and time-of-arrival of gamma rays in any detector can be determined accurately. Many experimental difficulties related to electronics are eliminated; the number of detectors can be increased with no increase in complexity of the apparatus; coincidences among any two detectors are measurable; and coincidences separated by as little as a ns are detectable in principle within one detector. All energies are collected, and energy windows are imposed by software filtering, permitting both high energy resolution and high data-gathering power.     

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。