Design of an FPGA-Based Algorithm for Real-Time Solutions of Statistics-Based Positioning

We report on the implementation of an algorithm and hardware platform to allow real-time processing of the statistics-based positioning (SBP) method for continuous miniature crystal element (cMiCE) detectors. The SBP method allows an intrinsic spatial resolution of ~1.6 mm FWHM to be achieved using our cMiCE design. Previous SBP solutions have required a postprocessing procedure due to the computation and memory intensive nature of SBP. This new implementation takes advantage of a combination of algebraic simplifications, conversion to fixed-point math, and a hierarchal search technique to greatly accelerate the algorithm. For the presented seven stage, 127 × 127 bin LUT implementation, these algorithm improvements result in a reduction from >7 × 10(6) floating-point operations per event for an exhaustive search to < 5 × 10(3) integer operations per event. Simulations show nearly identical FWHM positioning resolution for this accelerated SBP solution, and positioning differences of <0.1 mm from the exhaustive search solution. A pipelined field programmable gate array (FPGA) implementation of this optimized algorithm is able to process events in excess of 250 K events per second, which is greater than the maximum expected coincidence rate for an individual detector. In contrast with all detectors being processed at a centralized host, as in the current system, a separate FPGA is available at each detector, thus dividing the computational load. These methods allow SBP results to be calculated in real-time and to be presented to the image generation components in real-time. A hardware implementation has been developed using a commercially available prototype board.     

BESⅢ在线测试集群系统的设计与实现

讨论了应用普通的PC机和Linux操作系统以及其他免费软件实现的BESⅢ在线数据获取系统的测试计算机集群的设计与实现.系统运行正常,并且为在线软件提供了很好的反馈以及诊断.所采用的技术将被应用到实际的BESⅢ在线数据获取系统上.同时也可以应用到其他目的的集群系统上,如物理分析.     

Implementation and integration of a systematic DBPM calibration with PLL frequency synthesis and FPGA

Beam current dependence resulted from nonlinearity and asymmetry of the four channels of digital BPM(Beam Position Monitor) processor deteriorates the BPM performance.A systematic solution based on signal source calibration tactics has been carried out to rectify this defect.It is optimized for implementation in FPGA.Mathematical illustrations of the calibration method,hardware and software design and implementation are presented.A signal source circuit using frequency synthesis technique is designed as calibration standard.Data acquisition system using JAVA web technology and Ethernet is introduced.Integrated FPGA implementation code architecture is presented,and experimental test results show that the method implemented in FPGA is feasible.Compared to other methods,our approach can rectify the nonlinearity and asymmetry simultaneously.The whole solution is integrated into the DBPM processor and can be executed online.     

Ultra fast electron beam X-ray computed tomography for two-phase flow measurement

Electron beam X-ray CT is a new technique for a fast measurement of multiphase flows with frame rates of 1000 images per second and more. It gives, in principle, quantitatively accurate images of the flow at high spatial resolution and it is non-intrusive since moderately radiation absorbing vessel walls can be penetrated by X-rays. However, on the road to a technical realisation of such a technique within a computed tomography system many problems have to be solved. As a first prototype for scientific flow measurement studies, we devised and built a fast scanned electron beam X-ray tomography scanner. The scanner consists of an electron beam unit that can be operated at up to 150 kV acceleration voltage and up to 65 mA electron beam current, with the required electron optics for beam adjustment, beam focusing and beam deflection unit and a fast circular CZT detector comprising 240 elements of 1.5 mm × 1.5 mm × 1.5 mm active pixel area. X-ray radiation is produced on a circular water cooled tungsten target. The CT system achieves up to 7000 frames per second with a spatial resolution of 1 mm. First two-phase flow experiments have been carried out on gas-water flows in bubble columns. Further, a vertical test section made of titanium alloy has been installed at the TOPFLOW facility and will be used in future to study the evolution of two-phase gas-water pipe flow at high pressures and temperatures.     

A TDC-Based System for X-Ray Imaging Detectors

An image acquisition system is presented for use with position sensitive detectors (PSD). The system is based on a high-resolution time-to-digital converter (TDC) and a field programmable gate array (FPGA). The detectors use gas as absorbing medium and two delay lines to identify the coordinates of each detected particle. The TDC translates the time information coming from the delay lines into digital words, from which the particle position coordinates are encoded. The FPGA is responsible for processing each event, controlling the data acquisition and communicating with a personal computer. 256 pixels$times$256 pixels images are stored into an on-board memory. This resolution is increased to 512 pixels$times$512 pixels by using a time multiplexing technique. The maximum data acquisition rate is 1.2 million events per second. X-ray images obtained with the system are shown, which illustrate the overall performance.     

Neutron Irradiation as a Means of Reducing the Incidence of Radiation Induced Breakdown in a Radiation Hard Power MOSFET

The problem of transient gamma induced "second breakdown" in a specially developed radiation hard power MOSFET is discussed, and results of experiments in which neutron irradiation was used to control minority carrier lifetime are presented. The technique is only partially successful at reducing susceptibility to second breakdown.     

A High Precision DC Restorer

The performance of high resolution pulse amplitude spectrometers is often seriously degraded at high counting rates due to baseline problems of various kinds. A variation on the Robinson double-diode dc restorer is presented which makes it possible to obtain high resolution with Li-drifted Ge spectrometers at counting rates greater than 50,000 per second.     

Analytical Investigation of Neutron Hardening of Integrated Injection Logic

An analytical technique is presented for investigating the neutron induced degradation of integrated injection logic (I2L) inverter cells as a function of basic processing variables. The technique combines a one-dimensional semiconductor device code, the PN code, with the circuit analysis code SPICE. Predictions of neutron induced degradation as a function of npn transistor base doping, epitaxial thickness and resistivity and pnp transistor base width are presented for a second generation I2L technology. A comparison of predicted response to experimental data is given for inverter cells fabricated with different npn base doping and epitaxial thickness.     

First User Results From the HOTWAXS Detector System

Over the past 10 years combined techniques such as small angle and wide angle X-ray scattering (SAXS/WAXS) and X-ray absorption spectroscopy (XAS) with X-ray diffraction (XRD), have become the mainstay of time resolved experimental studies carried out at synchrotron radiation sources (SRS). However, these techniques have been limited by the detectors used to measure the wide angle scattering/diffraction pattern, and therefore restrict the dynamic experiments that can be studied. The HOTWAXS (High Overall Throughput Wide-Angle X-ray Scattering) detector project was designed to address this issue by producing a position sensitive, parallax free, high count rate, photon counting detector based on microstrip gas chamber (MSGC) technology. The initial experiments, performed on station 16.1 of the Daresbury SRS, with a high density polyethylene sample, confirmed the local count rate per channel to be 1 times 10⁶ counts per second. A global count rate over the 512 channel detector of 27 times 10⁶ counts per second was also measured for this sample. Time resolved experiments on stations 2.1 and 9.3 with real 'user' samples have also been performed, the results of which are presented.     

Effect of helium on void formation in nickel

This study examines the influence of helium on void formation in self-ion irradiated nickel. Helium was injected either simultaneously with, or prior to, the self-ion bombardment. The void microstructure was characterized as a function of helium deposition rate and the total heavy-ion dose. In particular, at 575°C and 5 × 10^?3 displacements per atom per second the void density is found to be proportional to the helium deposition rate. The dose dependence of swelling is initially dominated by helium driven nucleation. The void density rapidly saturates after which swelling continues with increasing dose only from void growth. We conclude that helium promotes void nucleation in nickel with either helium implantation technique, pre-injection or simultaneous injection. Qualitative differences, however, are recognized.     

溶剂萃取法处理高放废液过程中防止形成第二有机相的技术

概要介绍和评述了用溶剂萃取法处理高放废液时避免产生第二有机相的若干技术：复合萃取体系、芳香烃作为稀释剂、稀释法、还原法、络合法以及非平衡萃取法。后者对用ＴＲＰＯ－煤油溶液处理我国生产堆高放废液有着良好的应用前景。     

High Intensity Multi-GeV Proton Accelerators

For performing many high-energy physics experiments, it is necessary to have high-energy particle beams of very high intensity. The intensity of particle beams in circular proton accelerators in the multi-GeV energy range depends, first, on the number of protons accelerated per pulse and, second, on the number of pulses per second. The number of protons which can be accelerated per pulse is limited by the space charge effects, and the number of pulses per second is limited by the design or type of the accelerator. These intensity limitations and methods of pushing back these limits are discussed. It is now feasible both technologically and economically to construct accelerators in the tens of GeV energy range which will accelerate more than 1014 protons per second.     

Photoinduced trapping of xenon in polymeric films at ambient temperature

A new technique which allows the storage of noble gases in polymeric films at ambient temperature was successfully developed. The trapping of the rare gases in the polymer takes place via X-ray irradiation of the gas and the polymer film by means of an X-ray tube. Concentrations up to about 2 × 10¹⁷ atoms of noble gas per cm² of the film were obtained. The thermal energy needed for desorbing Xe from a kapton film was found to be about 16 kcal/mol which is large compared with the known values for thermal desorptions on metal surfaces. An energy shift of 1.04 ± 0.48 eV was further observed for the 5p–1s X-ray transition of trapped Xe atoms, which permits to surmise a rather strong interaction between the sorbate atoms and the sorbent molecules. Two interpretations of the observed phenomena are presented, the first involves bond ruptures and bond rearrangements in the polymer whereas the second is based on the assumption that chemisorption or persorption of Xe occurs in the polymeric substrate.     

A New Method for Low Sensitivity Design of a Controller for a Load Following BWR Power Plant

A new method has been proposed in which the controller is approximated by two low order models, the second being the sensitivity model of the first. Thus a Kind of piecewise solution is proposed in which the system retains the same order irrespective of the number of parameters to be considered for low sensitivity design. The usefulness of the proposed technique is illustrated in the controller design for a direct cycle BWR power plant of 457 MW(thermal) with recirculation control. The mathematical model includes the reactor kinetics, hydrodynamics of the recirculation loop, pressure transients, and the load frequency control system. The response of system variables such as frequency, neutron power, and reactor pressure are plotted with the low sensitivitty controller. The sensitivity function of frequency has been plotted using the conventional and proposed low sensitivity controller for 20 per cent variation in parameter values. The method is specifically recommended for controller design of large size systems.     

Experimental evaluation of the submerged detector method to improvethe accuracy of in-situ gamma spectrometry

The rapid and accurate quantification of radioactivity in the ground is important in many instances to enable appropriate decisions to be made about limiting its use. In-situ gamma spectrometry has been shown to be a potentially powerful technique for providing this information but its accuracy is dependent on knowledge of the activity variation with depth which is generally unavailable. Methods that allow this distribution to be rapidly determined have previously been published but all rely on a fixed depth-distribution model which is unrealistic. A novel technique using submerged collimated detector measurements termed the “submerged detector method” (SDM) has been proposed, and theoretically assessed in earlier work and has given promising results. In this work, the SDM is experimentally assessed at 19 sites in Wales, U.K., of variable ¹³⁷Cs activity levels and profile shapes. Practicality and accuracy both in the derived activity per unit area and the profile shapes were assessed against the best of the other methods. The results confirm that the SDM gives more accurate results with the derived activity per unit area on average within ~40% of the true value and the depth distributions being more accurately determined     

Study of leaktightness integrity of containment wall without liner in high performance concrete under accidental conditions—I. Experimentation

When a partially saturated concrete wall is subjected to accidental conditions (high temperature and steam water pressure, as a LOCA or more severe conditions), water vapour penetrates the containment wall until saturation level of the containment atmosphere is achieved. The rate of penetration of water vapour through concrete is progressively reduced, leading to improvement of the leaktightness integrity of the concrete wall. In this paper, experimental studies involving the measurement of temperature, moisture propagation and pore pressures in a concrete containment wall are presented. The tests have been carried out on cylindrical specimens, made of high performance concrete (HPC) and having 1.3 m thickness (same thickness as a containment wall of a nuclear power plant). A finite element analysis is used to study the heat and mass transfer through the concrete wall. The results of this numerical modelling technique are presented in the second part of this study.     

弱中子源强度测量技术研究

简要叙述了采用 BF3正比计数管和 6Li玻璃闪烁体测量贫化铀材料的自发裂变中子发射率的实验研究及结果。实验测得贫化铀材料自发裂变中子发射率为 2 8/ s·kg,与理论预估在误差范围内一致。     

Development of signal analysis method for the motional Stark effect diagnostic on EAST

A pilot single-channel Motional Stark Effect (MSE) diagnostic has been developed on EAST since 2015.The dual photo-elastic modulators (PEM) were employed to encode the polarization angle into a time-varying signal.The pitch angle was related to the ratio of modulation amplitude at the second harmonic frequency.A digital harmonic analyzer (DHA) technique was developed for extracting the second harmonic amplitude.The results were validated with a hardware phase lock-in amplifier,and is also consistent with the software dual phase-locking algorithm.