Use of silicon drift detectors for the detection of medium-light elements in PIXE

In order to fully exploit in PIXE the superior performance of silicon drift detectors especially for the detection of low- and medium-energy X-rays, avoiding in particular the negative effects of backscattered particles, we developed a custom spectrometer based on a 10 mm² chip with a thermoelectric Peltier cooler and home-designed front-end electronics, coupled to a weakly focusing polycapillary lens.This paper briefly describes the detector + lens assembly and reports the results of first tests carried out at an external beam line of the LABEC laboratory in Florence. Excellent energy resolution is achieved under real operating conditions in a PIXE run (measured FWHM at 1 keV is 81 eV with a count-rate of 480 cps) and also the lineshapes are very good (FW1/10M over FWHM ratio is 2.1). As a whole, our preliminary tests gave encouraging results and also helped to point out some aspects which it is worthwhile to investigate further (e.g. how X-ray peak intensity ratios may be affected by inaccurate lens alignment), in order to profit fully from such a good performance of the spectrometer.     

Readout electronics for a high-resolution soft X-ray spectrometer based on silicon drift detector

The readout electronics for a prototype soft X-ray spectrometer based on silicon drift detector (SDD),for precisely measuring the energy and arrival time of X-ray photons is presented in this paper.The system mainly consists of two parts,i.e.,an analog electronics section (including a pre-amplifier,a signal shaper and filter,a constant fraction timing circuit,and a peak hold circuit) and a digital electronics section (including an ADC and a TDC).Test results with X-ray sources show that an energy dynamic range of 1-10 keV with an integral nonlinearity of less than 0.1％ can be achieved,and the energy resolution is better than 160 eV@5.9 keV FWHM.Using a waveform generator,test results also indicate that time resolution of the electronics system is about 3.7 ns,which is much less than the transit time spread of SDD (＜100 ns) and satisfies the requirements of future applications.     

微机核子计量系统多路信号采集/控制卡研制

介绍了最新研制的可用于微机核子计量系统的同时采集32路模拟信号和输出16号控制信号的接口板,及其基本原理和组成结构。     

Self-calibrating position-sensitive silicon detectors

Position-sensitive silicon detectors with discrete position output signal levels, which have been developed for heavy ion reaction studies at the Lawrence Berkeley Laboratory are discussed. The detectors, both 300- and 5000-μm thick, for use in ΔE-E telescopes, use a series of high and low conductivity strips on the detector p⁺ contact to produce a position signal with 15 discrete levels. Since the position of the signals from the strips is known, the detectors are self-calibrating against position nonlinearities. Some aspects of the fabrication of both the 300- and 5000-μm detectors are discussed, along with their operating characteristics. Illustrative experimental results of ¹³⁹La-induced reactions on ⁴⁰Ca targets are presented     

Semiconductor drift detectors for X- and gamma-ray spectroscopy and imaging

The semiconductor drift detectors (SDDs) show basic advantages, in terms of spectroscopic resolution and detection rate, with respect to other semiconductor detectors. These advantages are strictly related to the very low values of the output capacitance of these devices. In this paper the working principles and the performance of the SDDs are presented and the most recent devices (“droplet type” SDDs and monolithic arrays of SDDs) are introduced. The requirements of front-end electronics for the readout of the SDDs signals are then discussed and the most recent implementations (pulsed-reset preamplifiers, multi-channel ASIC readout circuits) are introduced. Some relevant applications of SDDs in the field of X-ray spectroscopy for material analysis and for nuclear physics experiments, and in the field of gamma-ray imaging, are presented as a conclusion.     

Recent results for the CMS tracker silicon detectors

The paper reports on a detailed study of the radiation resistance of p⁺ on n silicon microstrip detectors for the CMS tracking system. From this study, it is seen that the use of low-resistivity substrates with 〈100〉 crystal lattice orientation promises excellent performance of the Inner Tracker after heavy irradiation in the Large Hadron Collider environment. Furthermore, the advantage of using detectors thicker than 300 μm in the Outer Tracker is discussed together with experimental measurements on prototypes     

Designing a linear silicon drift detector

The design and 2D simulation results of a Silicon Drift Chamber with a rectangular configuration are presented. The proposed structure is intended to allow a test of the technology used in the production of the device and serve as a basis to verify different solutions in the design of drift detectors     

Large area cylindrical silicon drift detector

An advanced silicon drift detector, a large-area cylindrical drift detector, was developed. The authors focus on the design aspects of the detector. They study the transport of electrons in a cylindrical geometry. The consequences of the transport analysis for the pitch of anodes and for the number of readout channels is shown. The flow of the leakage current generated at the Si-SiO₂ interface into a sink anode is considered. The diversion of the leakage current away from the signal anodes improves the performance of the detector. The increase of the current generation on the Si-SiO₂ interface due to anticipated radiation damage effects the detector less. Some results obtained from laboratory tests and from the operation of the detector at the NA45 experiment at CERN are shown     

Neutron-induced radiation damage in silicon detectors

Ion-implanted silicon pad detectors fabricated on different n-type and p-type silicon wafers with initial resistivities between 2.6 and 12.9 kΩcm were irradiated with neutrons of ~1 MeV energy, up to a fluence of 5×10¹³ n cm^-2. The evolution of diode leakage current and capacitance characteristics is presented as a function of the neutron fluence. The reverse diode current increases proportionally to the neutron fluence. There is evidence that the doping of the initial n-type material evolves towards intrinsic and inverts to an apparent p-type at fluences between 1×10¹³ and 3×10¹³ n cm^-2, depending on the initial silicon resistivity. There is also evidence that p-type material remains of the same conduction type with a slight increase of the acceptor doping with fluence. The signal shape and the charge collection efficiency for incident β particles were measured     

基于FPGA的SDD探测器随机信号模拟发生器

设计了一款硅漂移探测器(Silicon Drift Detector,SDD)信号模拟器用于测试SDD读出电子学的性能。该信号模拟器采用现场可编程门阵列(Field Programmable Gate Array,FPGA)作为核心器件,利用其丰富的可编程逻辑资源产生多组振荡环,将其输出相异或生成均匀分布的真随机数。首先通过伯努利试验将均匀分布的随机数转化为时间间隔服从指数分布的脉冲序列,然后对随机数进行了美国国家标准与技术研究院(National Institute of Standards and Technology,NIST)随机性测试,最后测试了信号模拟器输出脉冲的时间间隔和计数率特性,结果表明:SDD信号模拟器的输出脉冲时间间隔服从指数分布、输出计数率范围为1.6～813.8 ks~(-1)、输出脉冲的电压范围为2.5～50 mV、脉冲最小时间间隔为9.6 ns,并且可长时间稳定工作。     

A novel self-biased linear silicon drift detector

A novel linear silicon drift detector (SDD) is proposed in which the proper potential profile is established by the voltage drop along a unique p⁺ cathode implanted across the surfaces. This p⁺ implant, arranged in a zigzag shape, acts at the same time as voltage divider and field cathode and allows us to increase the sensitive area, improving also the uniformity of the thermal distribution and thus minimizing the fluctuation of the electron mobility on the sensitive zone of the SDD. The perturbations of the drift field due to the asymmetry of the strips constituting the zigzag cathode have been evaluated by solving analytically Poisson's equation for a simplified model of the structure. Three-dimensional numerical simulations have been carried out to prove the negligible amount of the perturbation and the effectiveness of the proposed structure. Based on this principle, a prototype has been manufactured at Canberra Semiconductor Company. Dynamic measurements of the time-of-flight of an injected charge prove that the linearity of the prototype and the drift uniformity in the anode direction are very high     

Metal/amorphous silicon multilayer radiation detectors

A multilayer structure is described for use in a number of radiation detectors. The structure consists of alternating layers of metal and amorphous silicon (a-Si). The absorption of radiation mainly occurs in the metal layers, while electron-hole pairs are generated in the a-Si layers by the emitted secondary particles from the metal layers. The fundamental applicability of this novel detector for X-ray detection was confirmed by Monte Carlo computer simulations as well as by results for an experimental five-layer Ta(0.5 μm)/a-Si(3 μm)/Mo(0.5 μm) X-ray sensor fabricated on a 1.5-cm×4-cm glass plate. The authors have confirmed that the detector has rectifying characteristics, with the Mo and Ta layers forming Schottky barrier and ohmic contacts respectively     

Signal charge sharing in multilinear drift detectors: design andexperimental characterization

Multilinear silicon drift detectors (MLSDDs) are radiation detectors which combine excellent energy and position resolution with high count-rate capabilities. This is achieved by controlling the diffusion of the signal charges and limiting their lateral spread during the drift. This paper will present a study of the signal electrons' transport in MLSDDs in comparison with the experimental measurements. Three-dimensional simulations were carried out, taking into account diffusion effects and mutual electrostatic interaction between the signal electrons. A representative sample of these simulations will be presented. Signal sharing in a multilinear drift detector and in a “classical” multi-anode drift detector are characterized and discussed. The results are useful to tailor the design of MLSDDs for the detection of different kinds of radiation (e.g., optical photon, X-ray, ionizing particle) and to optimize signal charge sharing and detector performance according to a particular application purpose     

Compton recoil electron tracking with silicon strip detectors

The application of silicon strip detectors to Compton gamma ray astronomy telescopes is described. The silicon Compton recoil telescope tracks Compton recoil electrons in silicon strip converters to provide an unique direction for Compton scattered gamma rays above 1 MeV. With strip detectors of modest positional and energy resolutions, of 1 mm FWHM and 3% at 662 keV, respectively, true imaging can be achieved to provide an order of magnitude improvement in sensitivity to 1.6×10 ^-6 γ/cm²-s at 2 MeV. The results of extensive Monte Carlo calculations of recoil electrons traversing multiple layers of 200 μm silicon wafers are presented. Multiple Coulomb scattering of the recoil electron in the silicon wafer of the Compton interaction and the next adjacent wafer is the basic limitation to determining the electron's initial direction     

SSRF定时系统的温漂补偿系统设计

上海同步辐射装置(SSRF)的定时信号通过光纤由事件发生器EVG发送到事件接收器EVR,为各个分系统和设备提供精确时序信号,但光纤因SSRF复杂的局部环境而产生温度变化,从而引起EVR的输出信号与高频信号的相位漂移.因此需设计-套温漂补偿系统来补偿这种因光纤的温度变化而产生的相位漂移,本文详细阐述了温漂补偿系统的硬件架构及相位测量算法,最后给出了温漂补偿系统的测试结果.