A DSP based FASTBUS board for data acquisition or high leveltrigger control in DELPHI electromagnetic calorimeters

A versatile FASTBUS board that is based on fast digital signal processors (DSPs) and analog-to-digital converters is described. It has been developed for the real-time acquisition and online processing of signals produced in different electromagnetic calorimeters of the DELPHI detector at the LEP (Large Electron Positron) collider. The board contains six TMS32010 DSPs, six piggyback cards for the analog-to-digital conversion, a set of 512-word FIFO memories for data exchange between contiguous DSPs and with external devices and a 16 K×16 random-access memory for data storage, accessible both to the DSPs and to FASTBUS in an asynchronous way, with override privilege granted to the DSPs     

分段γ扫描装置校准用桶状标准源的设计

放射性废物桶分段γ扫描(Segmented Gamma Scanning,SGS)测量装置结构复杂,其测量对象即废物桶自身的放射性物质的分布、组成、活度范围以及堆积密度等差别较大,若对每类样品单独进行效率刻度,通常需要多个不同组成和体积庞大的刻度源,从而花费大量的时间和费用。通过对SGS装置的测量方法的研究,设计出以线状源法为核心的放射性废物桶标准源的基本模型,该模型由单个与废物桶相同高度的线状源插入废物桶中进行旋转测量形成,优点是放射性废物桶标准源内放射性核素与填充基质分开,结构灵活且安全性较高。通过实验测量结果和蒙特卡罗模拟的结果进行比较,验证其用于量值传递的可行性。     

Energy calibration of the 500 kV heavy ion implanter ionas

Gamma ray yield functions of (p, αγ) and (p, γ) resonance reactions on semi-thick ¹⁹F, ²³Na, ^24,26Mg and ²⁷Al targets were measured and used to calibrate the accelerating voltage and energy resolution of the new 500 kV heavy ion implanter at Göttingen. The energy spread of the proton beam was found to vary linearly with the accelerating voltage from ΔE(200 keV) = 55 eV fwhm to ΔE(500 keV) = 105 eV; it is made up by a 0.012% high voltage ripple and the Doppler broadening of the resonances due to the thermal motion of the target nuclei. A long term stability of the proton energy of < 5 eV/h at 300 keV was achieved with new resistors in the voltage regulating system.Applications of the accelerator for the remeasurement of some resonance energies and widths and for depth profiling of light implanted ions in metals by the resonance broadening method will be briefly discussed.     

Energy calibration of a CR-39 nuclear-track detector irradiated by charged particles

Charged particle diagnosis is an important aspect of laser–plasma experiments conducted at super-intense laser facilities. In recent years, Columbia Resin #39(CR-39) detectors have been widely employed for detecting charged particles in laser–plasma experiments. This is because the CR-39 polymer does not respond to electromagnetic pulses or X-rays. This study presents a method for calibrating the relationship between particle energy and track diameter in a CR-39 detector(TasTrak~?) using3–8 MeV protons, 6–30 MeV carbon ions, and 1–5 MeV alpha particles. The particle tracks were compared under the manufacturer's recommended etching conditions of6.25 mol/l NaOH at 98 °C and under the widely adopted experimental conditions of 6.25 mol/l NaOH at 70 °C. The results show that if the NaOH solution concentration is6.25 mol/l, then the temperature of 70 °C is more suitable for etching proton tracks than 98 °C and employing a temperature of 98 °C to etch alpha-particle and carbon-ion tracks can significantly reduce the etching time. Moreover,this result implies that C~(3+) ion or alpha-particle tracks can be distinguished from proton tracks with energy above3 MeV by controlling the etching time. This calibration method for the CR-39 detector can be applied to the diagnosis of reaction products in laser–plasma experiments.     

Energy distributions of neutral atoms sputtered by very low energy heavy ions

Polycrystalline Cu was sputtered by normally incident, very low energy Ar⁺ ions (E₀ = 40–1000 eV). The kinetic energy (E) distributions of the neutral Cu atoms sputtered normally from the Cu surface were measured, using secondary neutral mass spectrometry. For values of E₀ above approximately 600 eV, the observed energy distributions agreed closely with the Thompson-Sigmund theory. For values of E₀ less than about 600 eV the distributions fell off faster than predicted by the Thompson-Sigmund theory, and the peak value of the distribution shifted to somewhat lower energies. Both these effects were exaggerated as E₀ was further lowered. The average kinetic energy of the sputtered neutral Cu atoms increased with increasing E₀. The rate of this increase was less at higher values of E₀.     

Radiation induced effects in segmented poly(siloxaneurethaneureas) based on aliphatic and aromatic diisocyanates

Poly(siloxaneurethaneureas) (PSURURs) prepared from aromatic and aliphatic isocyanates were investigated upon exposure to ionising radiation. Radicals are formed both in siloxane and urethane segments. In comparison with aliphatic analogues it was found that in aromatic PSURURs: (1) concentration of all radicals is lower, (2) relative concentration of methylene radicals formed in siloxane units is higher, (3) the radiation yield of H₂ is more than three times smaller and (4) it seems that efficiency of cross-linking is less significant.     

基于多元线性回归模型的中性束质子比分析

中性束质子比的高低对其注入等离子体后的加热效果具有重要的影响。实验中,强流离子源的灯丝电压、弧压、进气量等宏观运行参数决定了中性束质子比的大小。以东方超环中性束注入测试台束引出实验为基础,利用多元线性回归模型对引出中性束质子比进行分析,建立了影响中性束质子比的预测方程,并对该模型的正确性进行了检验。结果表明,中性束质子比可利用以灯丝电压和弧压为自变量的多元线性回归模型进行分析,灯丝电压是影响质子比的关键参数,弧压次之。     

Energy dissipation and power deposition of electromagnetic waves in the plasma sheath

Energy dissipation and power deposition of electromagnetic waves(EMW) in the reentry plasma sheath provide an opportunity to investigate ‘communication blackout' phenomena. Based on afinite element method(FEM) simulation, we analyze variation of EMW energy dissipation and power deposition profiles dependent on the wave polarization, wave incident angle, plasma density profile and electron collision frequency. Cutoff and resonance of EMW in the plasma sheath are crucial in explaining the regulation of energy dissipation and power deposition.     

Study of electromagnetic noise influence on quench detection system under different discharge conditions for EAST

EAST is the first Tokamak device whose toroidal and poloidal magnet are superconducting. The enormous magnetic field energy stored in the magnet system will transfer into thermal energy and cause the damage of superconducting magnet, if a quench happened. Therefore, reliable quench detection is a key issue for steady-state operation. In addition to electromagnetic noise from poloidal magnet fields and plasma current which will experience fast current ramp rate, radio frequency noise from heating system also have some interference on quench detection system to a certain degree. The most difficult point for quench detection system is required to have more detail evaluation on electromagnetic noise interference.Recently experiments have been carried out successfully in EAST device. The steady-state operation with 1 MA of plasma current and more than 100-s plasma duration has been obtained. In the paper, the electromagnetic noise interference on quench detection system under different discharge conditions are analyzed and relative process methods are also introduced. The technological experience and experimental data are significant for the constructing ITER and similar superconducting device have been mentioned which will supply significant technological experience and experimental data for constructing ITER and similar superconducting device.     

Use of sampling based correction for non-radioactivity X-ray energy calibration

As the requirement of non-radioactivity measurement has increased in recent years, various energy calibration methods applied in portable X-ray fluorescence (XRF) spectrometers have been developed. In this paper, a sampling based correction energy calibration has been discussed. In this method both history information and current state of the instrument are considered and relative high precision and reliability can be obtained.     

Online calibration of laser-induced breakdown spectroscopy for detection of heavy metals in water

In order to reduce the fluctuation of LIBS detection spectrum of liquid sample, the full-spectrum sum method and the internal standardization method is adopted, using an equal-RSD normalization algorithm to calibrate the detection spectrum. Experiment result shows that the full-spectrum sum method reduced the RSD of parallel samples of Cd and Cr to 9.4％ and 11.06％ from 28.32％ and 31.93％ respectively, yielded better overall calibration than the singleelement internal standardization approach, thereby suggesting that the former method is convenient and effective for online calibration of LIBS for detection of aqueous heavy metals.     

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.     

一种基于Directshow的实时运动监测系统的实现

采用Directshow框架,对运动检测的传统模型提出了简化和改进,设计了一个功能较完整的运动检测Fitler,用在网络视频监控项目中,得出了实验结果.     

基于车载移动的区域射频电磁辐射监测方法比较研究

本文以江苏省南通市为例,分别采用车载移动法和国标法对城区射频电磁环境进行现场实测,共获取有效测试数据20 250个,其中移动法20 060个,国标法190个。比较分析结果表明:(1)两种方法单点比对监测结果相对偏差小于±10%;(2)两种方法所监测的南通城区环境射频电磁辐射平均综合电场强度分别为(0.58±0.28)V/m和(0.52±0.32)V/m,无明显差别,但在典型性和代表性表征上车载移动法明显优于国标法;(3)研究发现港闸区域50 Hz极低频高压输电线路沿路密集架设是车载移动法测值偏高的主要原因,可通过优化行驶路线避开高压线和后期数据处理等方法消除此类影响。本研究结果将有助于推动车载移动法国家监测技术规范的出台,并为在全国范围内推广应用提供了示范借鉴。     

Energy deposition of y-ray in different instances and its influence on energy detection

In this paper, we simulate y-ray energy deposition for different incident energies with four different models using the tool GEANT4 ( Geant4.7.0, 2005 ) developed by CERN (the Center of European Research of Nucleus).The results we obtained indicate that there are different peak values for different incident energies. That is, we can differentiate the incident energy accurately if the detector can determine the peak value accurately. This is meaningful for the geometrical configuration of the detector to get the most probable distribution (MPD) of energy deposition for different incident energies. According to the simulation, we can insert certain slices with large absorption coefficient to obtain a better MPD of energy deposition which will not alter the shape of the energy deposition.     

Investigation into wideband electromagnetic stealth device based on plasma array and radar-absorbing materials

Manipulation of electromagnetic waves is essential to various microwave applications, and absorbing devices composed of low-pressure gas discharge tubes and radar-absorbing materials (RAM) can bring new solutions to broadband electromagnetic stealth. The microwave transmission method is used to measure the physical parameters of the plasma unit. The designed structure exhibits superior absorption performance and radar cross-section (RCS) reduction capability in the 2–18 GHz band, with unique absorption advantage in the S and C frequency bands. It is found that the combination of the plasma and the RAM can significantly broaden the absorption frequency band and improve the absorption performance with excellent synergistic stealth capability. Experimental and simulation results present that broadband, wide-angle, tunable electromagnetic wave absorption and RCS reduction can be achieved by adjusting the spatial layout of the combined plasma layer and the type of RAMs, which creates opportunities for microwave transmission and selective stealth of equipment. Therefore, the wave manipulation by combined plasma array and RAM provides a valuable reference for developing numerous applications, including radar antenna stealth, spatial filter, and high power microwave shielding.     

Study on the ignition process of a segmented plasma torch

Direct current plasma torches have been applied to generate unique sources of thermal energy in many industrial applications.Nevertheless,the successful ignition of a plasma torch is the key process to generate the unique source (plasma jet).However,there has been little study on the underlying mechanism of this key process.A thorough understanding of the ignition process of a plasma torch will be helpful for optimizing the design of the plasma torch structure and selection of the ignition parameters to prolong the service life of the ignition module.Thus,in this paper,the ignition process of a segmented plasma torch (SPT) is theoretically and experimentally modeled and analyzed.Corresponding electrical models of different stages of the ignition process are set up and used to derive the electrical parameters,e.g.the variations of the arc voltage and arc current between the cathode and anode.In addition,the experiments with different ignition parameters on a home-made SPT have been conducted.At the same time,the variations of the arc voltage and arc current have been measured,and used to verify the ones derived in theory and to determine the optimal ignition parameters for a particular SPT.     

Characterization and calibration of a SSNTD for heavy-ion detection and strangelet search in cosmic rays

A commercially available grade of polymer was investigated for its suitability as a solid state nuclear track detector (SSNTD) to look for rare events in cosmic rays at very high mountain altitudes. It was identified to be polyethylene terephthalate (PET) and found to have a higher detection threshold compared to many other widely used SSNTDs. Hence it is particularly suited for rare event search in cosmic rays by eliminating the dominant low Z background. Systematic studies were carried out to determine the ideal etching condition. Also the charge response of PET was studied using various ion beams from accelerators. The results of such studies were combined to obtain the calibration curve for PET as SSNTD, by which one can identify and characterize charged particles.     

~3He正比计数器探测效率模拟及灵敏度刻度

利用Monte Carlo程序研究了3He正比计数器慢化体厚度与探测效率的关系,单能中子及Hess谱中子模拟给出5 cm的聚乙烯慢化体优化厚度。利用天然中子本底对探测器装置进行测试,并对探测器灵敏度进行了刻度。