ASIC With Multiple Energy Discrimination for High-Rate Photon Counting Applications

An ASIC for high rate photon counting measurements with multiple energy discrimination is presented. Optimized for pixelated CdZnTe sensors, the ASIC is composed of 64 channels with low-noise charge preamplification, high-order shaping (40 ns minimum peaking time), and five window-discriminators with associated 16-bit counters. An efficient readout scheme allows simultaneous measurement and readout through a 60 MHz 16-bit output bus. The ASIC architecture and experimental results are reported, and the impact of the shaper order on the resolution, ballistic deficit, and pile-up is discussed     

Ar+CH4混合气体中电子漂移速率的双栅法测量

提出了一种快速、准确测量电子在气体中漂移速率的新方法。通过分析电子在双栅电离室中两个栅极上产生的感应信号波形来确定电子漂移的起止时刻,从而得出电子在一定约化场强下的漂移速率。采用数据采集卡（waveformdigitizer）对电离室的极板信号进行记录。测量了电子在8种混合比例的Ar+CH₄气体中漂移速率随约化场强的变化曲线。通过分析实验数据,得到任意混合比例的Ar+CH₄气体中电子漂移速率的计算公式。     

A 64-Channel Wide Dynamic Range Charge Measurement ASIC for Strip and Pixel Ionization Detectors

In this paper we report a 64-channel application specified integrated circuit (ASIC) for the readout of parallel plate strip and pixel ionization detectors. The detectors measure the intensity and the geometrical characteristics of a hadron beam for hadrontherapy cancer treatments. The ASIC is based on a current to frequency converter followed by a counter. It uses a charge balancing integration technique to obtain a dynamic range in excess of$10^5$with a nonlinearity of less than 1%. The ASIC has been designed in a CMOS 0.8$mu m$technology and it has been used for the readout of both strip ionization detectors for beam calibration and pixel detectors for beam monitoring during treatment. A new version of the chip in CMOS 0.35$mu m$technology which allows bipolar input currents has been designed and is currently under test.     

Hydrogenated Amorphous Silicon Sensor Deposited on Integrated Circuit for Radiation Detection

Radiation detectors based on the deposition of a 10 to 30 mum thick hydrogenated amorphous silicon (a-Si:H) sensor directly on top of integrated circuits have been developed. The performance of this detector technology has been assessed for the first time in the context of particle detectors. Three different circuits were designed in a quarter micron CMOS technology for these studies. The so-called TFA (Thin-Film on ASIC) detectors obtained after deposition of a-Si:H sensors on the developed circuits are presented. High internal electric fields (10⁴ to 10⁵ V/cm) can be built in the a-Si:H sensor and overcome the low mobility of electrons and holes in this amorphous material. However, the deposited sensor's leakage current at such fields turns out to be an important parameter which limits the performance of a TFA detector. Its detailed study is presented as well as the detector's pixel segmentation. Signal induction by generated free carrier motion in the a-Si:H sensor has been characterized using a 660 nm pulsed laser. Results obtained with a TFA detector based on an ASIC integrating 5 ns peaking time pre-amplifiers are presented. Direct detection of 10 to 50 keV electrons and 5.9 keV X-rays with the detectors are then shown to understand the potential and the limitations of this technology for radiation detection.     

Assessment of RELAP5/MOD3.2.2 Gamma against ABB Atom 3×3-Rod Bundle Reflooding Tests

The results of the ABB Atom 3×3-Rod Bundle Reflooding Tests were used for assessment of the reflooding model used in RELAP5/MOD3.2.2 Gamma version. The assessment calculations were performed using the default calculation model options implemented in the code.The tests were performed to investigate the effects of different spacer grid designs on heat transfer during the reflooding period of a pressurized water reactor loss-of-coolant accident (LOCA). The tests were conducted under low-pressure and low-flow (LPLF) conditions using a PWR-type 3×3-rod bundle with full-length indirectly electrically heated, stepped cosine axial power-shaped heater rods. Three different spacer grid configurations were studied: spacer grids without mixing vanes, mixing vane spacer grids, and mixing vane spacer grids together with intermediate flow mixers (IFM).A total of 36 tests with different spacer grid configurations were calculated. For two selected basic tests with non-mixing spacer grids an extended comparison of calculated and measured parameters is presented. The comparison of the predicted and measured maximal cladding temperatures and quench times, which are the most important parameters in licensing calculations, is presented for all the performed tests.The assessment calculations were preceded by nodalization, time step, and moving mesh studies.The RELAP5/MOD3.2.2 Gamma code was found to still have several deficiencies in the reflood model. The calculation results show a satisfactory agreement with experimental inner peak cladding temperature, however the predicted temperature turn-around times and quench times are significantly too short. The results also show a significant over-prediction of the reflood heat transfer and the vapour temperatures. The void profile downstream the quench front is not correctly predicted either. Finally, the present reflood model does not properly reflect the effects of spacer grids on the reflood heat transfer.In spite of these deficiencies the improvements incorporated into RELAP5/MOD3.2 by the Paul Scherrer Institute (PSI) eliminated the unphysical behaviors such as continuous cooling without clear turn-around temperature and no visible quenching phenomena, which were shown in the reflood calculations by means of the RELAP5/MOD3.1 code.     

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.     

用于新型塑料闪烁体阵列探测器的多通道前端读出电子学设计

介绍一种用于新型塑料闪烁体阵列探测器系统的前端读出电子学（FEE）的设计与实现,该前端读出电子学主要基于电荷测量专用的集成电路（ASIC）芯片和现场可编程逻辑门阵列（FPGA）研制,可实现对多路探测器信号的采集、处理、筛选、打包,并通过LVDS差分接口上传到后端的数据获取系统（DAQ）。同时,该电路设有板载线性标定电路,可实现对各通道电子学性能刻度,设有电源电流、关键芯片及电路温度实时监控等电路,使电路具有较完善的功能和较强的自我保护能力。     

一种前端ASIC芯片测试系统的设计与实现

介绍了一种专用集成电路芯片性能测试系统的设计与实现,该芯片适用于构建硅探测器前端读出电子学.描述了测试系统主要硬件电路设计,基于CPLD的快读出控制时序发生模块的实现,利用并口线来模拟I2C总线的方法,系统的调试和主要性能的分析.     

Development of a compact DOI-TOF detector module for high-performance PET systems

To increase spatial resolution and signal-to-noise ratio in PET imaging,we present in this paper the design and performance evaluation of a PET detector module combining both depth-of-interaction(DOI) and time-offlight(TOF) capabilities.The detector module consists of a staggered dual-layer LYSO block with2 mm × 2 mm × 7 mm crystals.MR-compatible SiPM sensors(MicroFJ-30035-TSV,SensL) are assembled into an 8× 8 array.SiPM signals from both fast and slow outputs are read out by a 128-channel ASIC chip.To test its performance,a flood histogram is acquired with a ~(22)Na point source on top of the detector,and the energy resolution and the coincidence resolving time(CRT) value for each individual crystal are measured.The flood histogram shows excellent crystal separation in both layers.The average energy resolution at 511 keV is 14.0 and 12.7%at the bottom and top layers,respectively.The average CRT of a single crystal is 635 and 565 ps at the bottom and top layers,respectively.In conclusion,the compact DOI-TOF PET detector module is of excellent crystal identification capability,good energy resolution and reasonable time resolution and has promising application prospective in clinical TOF PET,PET/MRI,and brain PET systems.     

XA readout chip characteristics and CdZnTe spectral measurements

The authors report on the performance of a CdZnTe (CZT) array readout by an XA (X-ray imaging chip produced at the AMS foundry) application specific readout chip (ASIC). The array was designed and fabricated at NASA/Goddard Space Flight Center (GSFC) as a prototype for the Burst Arc-Second Imaging and Spectroscopy gamma-ray instrument. The XA ASIC was obtained from Integrated Detector and Electronics (IDE), in Norway. Performance characteristics and spectral data for ²⁴¹Am are presented both at room temperature and at -20°C. The measured noise (σ) was 2.5 keV at 60 keV at room temperature. This paper represents a progress report on work with the XA ASIC and CZT detectors. Work is continuing and in particular, larger arrays are planned for future NASA missions     

Test system of the front-end readout for an application-specific integrated circuit for the water Cherenkov detector array at the large high-altitude air shower observatory

The water Cherenkov detector array (WCDA) is an important part of the large high-altitude air shower observatory (LHAASO),which is in a research and development phase.The central scientific goal of LHAASO is to explore the origin of high-energy cosmic rays of the universe and to push forward the frontier of new physics.To simplify the WCDA's readout electronics,a prototype of a front-end readout for an application-specific integrated circuit (ASIC) is designed based on the timeover-threshold method to achieve charge-to-time conversion.High-precision time measurement and charge measurement are necessary over a full dynamic range [1-4000 photoelectrons (P.E.)].To evaluate the performance of this ASIC,a test system is designed that includes the front-end ASIC test module,digitization module,and test software.The first module needs to be customized for different ASIC versions,whereas the digitization module and test software are tested for general-purpose use.In the digitization module,a field programmable gate array-based time-todigital converter is designed with a bin size of 333 ps,which also integrates an inter-integrated circuit to configure the ASIC test module,and a universal serial bus interface is designed to transfer data to the remote computer.Test results indicate that the time resolution is better than 0.5 ns,and the charge resolution is better than 30％root mean square (RMS) at 1 P.E.and 3％ RMS at 4000 P.E.,which are beyond the application requirements.     

Applying particle swarm optimization algorithm for tuning a neuro-fuzzy inference system for sensor monitoring

A neuro-fuzzy inference system (ANFIS) tuned by particle swarm optimization (PSO) algorithm has been developed for monitoring the relevant sensor in a nuclear power plant (NPP) using the information of other sensors. The antecedent parameters of the ANFIS that estimates the relevant sensor signal are optimized by a PSO algorithm and consequent parameters use a least-squares algorithm. The proposed methodology to monitor sensor output signals was demonstrated through the estimation of the nuclear power value in a pressurized water reactor using as input to the ANFIS six other correlated signals. The obtained results are compared to two similar ANFIS using one gradient descendent (GD) and other genetic algorithm (GA), as antecedent parameters' training algorithm.     

Integrated computerisation of operating procedures

The computerisation of procedures can address not only the way procedures are presented or displayed, but also how they are generated and maintained. The computerisation of procedure generation will result in an improved basis for procedure display, and also make it possible to maintain the procedures on the level of internal representation rather than on the level of display. This paper describes a project, which focused on developing a system for computerised procedure generation (CPG) based on the principles of cognitive systems engineering. The CPG system was integrated with an already existing system for computerised procedure presentation, and enhanced with a number of other functions to produce a system for integrated computerisation of operating procedures.     

压水堆棒束定位格架两相搅混特性数值研究

本文提出一种CFD方法用于评价压水堆燃料棒束定位格架两相搅混特性。针对两种典型的定位格架,采用CFX12.0进行了空气-水两相流动的数值模拟,并与采用氟里昂工质开展的临界热流密度（CHF）实验进行对比。结果表明,CFD方法可初步应用于评价格架下游汽泡的分布特性。     

Hybrid Pixel Particle-Detector Without Bump Interconnection

A hybrid pixel particle-detector which does not require bump-interconnection is presented. The sensor signals are transmitted from the sensor to the readout chip using capacitive (AC) coupling. In order to facilitate the signal transmission, simple preamplifiers are implemented in the sensor pixels. The sensor chip with 100% fill-factor and in-pixel amplification is implemented in a standard high-voltage CMOS technology. Depleted high-voltage n-well/p-substrate diodes are used as sensors. CMOS charge-sensitive amplifiers are placed inside the sensor-collecting electrodes (n-wells) using twin-wells. The outputs of the preamplifiers are connected to transmitter electrodes implemented in the top metal-layer of the sensor chip. The inputs of the receivers in the readout chip are also connected to electrodes in the top metal-layer. When the readout chip is precisely flipped and glued onto the sensor chip, the sensor- and receiver electrodes form capacitors that allow AC signal transmission. The first test results obtained with a small test-matrix containing 14 times 14 pixels of 78 times 60 mum²-size are presented. Noise, threshold dispersion and radioactive source spectra are measured.     

广义分维在地震信号初至检测中的应用

基于地震信号的能量特征及广义分维的思想,给出一种新的地震信号初至估计算法。根据Mandelbrot-Richardson曲线截距的变化．可以准确检测到地震信号的初至。对于微弱地震信号初至的检测,首先按信号幅频特征的变化对原始记录进行预处理,在不改变地震信号初至的前提下,提高了记录的信噪比。对MR曲线的截距变化曲线进行类似于坐标旋转的校正．使对应信号初至的拐点成为曲线的极小值．有助于信号初至的自动检测。     

用于计算较大尺度面源气载放射性释放的环境辐射剂量的一种套网格模型

本文介绍一种用于较大尺度面源气载放射性释放环境影响评价的套网格模型，该模型采用扇形网格和正方形网格相结合，以扇形网格为基本框架，而将面源区和近源区划分为正方形网格，在进行大气扩散估算时，为合理模拟空气浓度分布，在面源区和近源区，采用大气湍流扩散实验室模式；在其它区域，将面源视作若干个虚拟点源，采用高斯烟羽模式。在进行环境辐射剂量估算时，先将正方形网格点的空气浓度值内插到扇形网格，然后按扇形网格下的     

X-ray detection based on complementary metal-oxide-semiconductor sensors

Complementary metal-oxide-semiconductor(CMOS) sensors can convert X-rays into detectable signals; therefore, they are powerful tools in X-ray detection applications. Herein, we explore the physics behind X-ray detection performed using CMOS sensors. X-ray measurements were obtained using a simulated positioner based on a CMOS sensor, while the X-ray energy was modified by changing the voltage, current, and radiation time. A monitoring control unit collected video data of the detected X-rays. The video images were framed and filtered to detect the effective pixel points(radiation spots).The histograms of the images prove there is a linear relationship between the pixel points and X-ray energy. The relationships between the image pixel points, voltage, and current were quantified, and the resultant correlations were observed to obey some physical laws.     

带增益的气体探测器读出ASIC的研制

设计了用于带增益的气体探测器比如GEM、RPC等读出的ASIC,实现对探测器信号的放大、成形和对后续实时采样ADC的驱动电路.电荷增益和成形时间可调,有利于探测器不同增益下性能的研究,也扩展了芯片的应用范围.由于成形电路引入的噪声变得显著,在低电荷增益下,ENC会随增益下降而增加.芯片采用Chartered 0.35μm2P4M CMOS工艺,论文介绍了芯片的详细设计和仿真结果.     

Signal reconstruction by a GA-optimized ensemble of PCA models

On-line sensor monitoring allows detecting anomalies in sensor operation and reconstructing the correct signals of failed sensors by exploiting the information coming from other measured signals. In field applications, the number of signals to be monitored is often too large to be handled effectively by a single reconstruction model. A more viable approach is that of decomposing the problem by constructing a number of reconstruction models, each one handling an individual group of signals. To apply this approach, two problems must be solved: (1) the optimal definition of the groups of signals and (2) the appropriate combination of the outcomes of the individual models. With respect to the first problem, in this work, Multi-Objective Genetic Algorithms (MOGAs) are devised for finding the optimal groups of signals used for building reconstruction models based on Principal Component Analysis (PCA). With respect to the second problem, a weighted scheme is adopted to combine appropriately the signal predictions of the individual models. The proposed approach is applied to a real case study concerning the reconstruction of 84 signals collected from a Swedish nuclear boiling water reactor.