Performance of small-radius thin-wall drift tubes in an SSCradiation environment at the MIT Research Reactor

Drift tubes of 1.9-mm radius and 25-μ wall thickness were exposed to neutrons and associated gamma radiation from uranium fission at the MIT Research Reactor. In 45 hours of irradiation, the drift tubes received a neutron fluence with energy greater than 0.5 MeV of 1.1×10¹³ cm^-2 And accumulated a charge per wire length of 0.08 coul cm^-1, about that expected for three years of operation at the SSC for a lead scintillator calorimeter at a 1-m radius and for drift tubes at a distance of several tens of centimeters from the beam axis. Measurement of the pulse height, pulse shape, counting rates, andcurrents showed no degradation in drift tube performance. Fast (few nanosecond rise time), sharp (20-ns width) pulses were observed at counting rates of 5 MHz using CF₄ as the drift gas     

KLOE高分辨电磁量能器

本文描述了ＫＬＯＥ高分辨电磁量能器的设计和结构，着重介绍了获得铅和闪烁光纤取样量能器优良性能的关键技术。为了研究这种量能器的性能，建造了２ｈ和一个全尺寸的量能器模块，其中两个小模块分别是一桶部模块和一个端盖模埠，本文给出了这三个模块的实验结果。     

New methods to remove baseline drift in trapezoidal pulse shaping

Trapezoidal pulse shaping algorithm is widely applied to improve signal-to-noise ratio(SNR), throughput and energy resolution with the properties of noise suppression, pile-up pulse separation and ballistic deficit correction. The algorithm can be acquired by z transform method which is easier for derivation. However, the baseline drift of trapezoidal pulse appears because the noise superimposes on the input signal. In this paper,two new methods based on convergence analysis and noise suppression are proposed to remove the baseline drift resulting from trapezoidal pulse shaping. Simulations and experimental tests are carried out to verify the methods. The results demonstrate that the proposed methods can remove baseline drift in trapezoidal pulse shaping.     

Calculation of the parameters of the field of a cylindrical absorbing radiator in the direction of the generator

The problem of determining the parameters of the field of a cylindrical absorbing radiator in the direction of the generator was solved for the case where the detection point lies outside the cylindrical surface of the radiator. A program of integrating the expression obtained numerically was developed. The results of calculations of the position of the dose rate isolines were presented for two radiators with relative heights 1 and 10. The maximum error was determined for the chosen numerical integration parameters relative to the exact solution: this error was found to be no greater than 2% for the interval of relative heights of the radiator 0.01–10. It was shown that the proposed scheme for obtaining the integral expression is much mor accurate than the scheme used previously for calculation of the parameters of the field in a range falling within the height of the radiator, 5 figures, 5 references. Affiliate of the North-West Civil Service Academy. Translated from Atomnaya énergiya, Vol. 88, No. 2, pp. 88–92.     

热管式辐射器热工水力优化分析

热管式辐射器广泛应用于空间系统废热排放，其管道复杂，包含热管、翅片和包壳等复杂结构。针对热管式辐射器的流动与换热问题，本文采用CFD软件与自主研发程序RATHAL相结合的方法。先用CFD软件计算流动管道及集流环上的流量分配，再将该结果代入RATHAL程序中计算得到辐射器的温度分布。根据计算结果，以均匀温度分布为目的，对现有结构提出了合理的优化意见。结果表明，采用CFD软件与自主研发程序RATHAL相结合的方法能尽量真实并高效地模拟辐射器的流量分配与温度分布情况，且经过优化后辐射器集流环间的温差大幅缩小、设计更加合理。     

TOPAZ-Ⅱ空间电源系统辐射器改进研究

针对前苏联TOPAZ-Ⅱ反应堆系统所采用回路式辐射器存在单点失效的问题,采用热管式辐射器对其进行改进以提高系统安全性。根据系统废热排出的要求及冷却剂工作温度,选取高温钾热管,对结构材料及相关参数进行了设计,同时设计了辐射器的结构、热管的布置方式及铜翅片的参数。热管中心蒸汽区通过一维流动方程进行了求解,采用有限元方法分析了热管管壁与吸液芯结构的导热,采用有限差分法对翅片的辐射导热进行了计算。对热管与翅片组成的辐射单元与集流环进行了耦合计算,得出了辐射器设计工况下的稳态结果,对其进行了分析并与回路式辐射器进行了相应比较。计算结果表明,所设计热管式辐射器满足TOPAZ-Ⅱ正常运行情况下的废热排出要求,并具有较多裕度,同时热管式辐射器的安全性与等温性也优于回路式辐射器。     

Characteistics of Multiwire Proportional Chambers for Positron Imaging

We describe multivire proportional chambers (MWPC) designed for use in a positron camera for Nuclear Medicine applications. The coordinates of the two annihilation gamma rays are detected in the chamber by their interaction with thin lead converters placed on both faces of each chamber. In order to obtain reasonable efficiencies (10%) the lead converters have been made in a square honeycomb-like structure, which increases the effective surface area and also permits the application of a drift field to extract the electrons into the active area of the MWPC.     

支撑体对γ辐射物探测数据的影响

在对大质量高安全性要求的γ源进行辐射探测时,发现数据误差很大,不能用于定量分析。为此,基于探测器端面注量率参数理论探析了地面或支撑台对探测器数据影响的简化计算方法,采用蒙特卡罗方法分析了混凝土支撑体对粒子注量率的影响程度,研究了铅作为次级粒子吸收物质时,铅厚度和半径与注量率测量误差之间的关系。研究结果表明,在放射性材料辐射探测过程中,为减少混凝土支撑体对辐射探测数据的影响,应采用厚度不小于0.5 cm、半径不小于源高3倍的铅板作为次级粒子吸收体,可将探测数据最大误差由22%减少至15%左右,最小可接近10%,实验结果证实了该方法的有效性。     

Scalar leakage flux spectra for 6 MeV gamma photon penetrations through PbAl and FeAl laminated shields

Leakage scalar flux spectra are established for 6 MeV gamma photons penetrating laminated shielding assemblies of lead-aluminium and steel-aluminium. A large diameter disc radiator filled with activated water provides the source of high energy photons. Scalar leakage spectra are presented for penetration through 5, 10, 20 and 30 cm aluminium following 10 cm steel and 7.5 cm lead. Results show that leakage spectra in laminated shields are characterized by the material properties of the outermost layer.     

Conceptual design of 5 MW-NBI injector for HL-2 M tokamak

The HL-2 M tokamak is now under construction in Southwestern Institute of Physics in China. As one of the main auxiliary heating systems for HL-2 M tokamak, a new NBI beam line with 5 MW NBI power, 42° injection angle, based on 4 sets of 80 kV/45 A/5 s bucket ion sources with geometrical beam focus, is conceptually designed with geometrical calculation and engineering simulations. The preliminary structure and layout of key components including ion sources, neutralizers, ion dumps, deflection magnet, beam edge scraper, long pulse calorimeter target, short pulse calorimeter target, injection port and beam drift duct are determined. The magnetic shielding of the stray field of HL-2 M tokamak is analyzed. Beam power transmission efficiency is calculated with geometrical algorithm. The ratio of neutral beam injection power to ion beam power is as high as 48%.     

程控增益线性脉冲放大器的设计

设计了一种新型程控增益线性脉冲放大器.采用准高斯CR-RC-CR成形电路结构,使用非易失性数字电位器和精密运放,使电路结构大大简化,抗干扰能力强,增益多级连续变化平稳,且具有温漂低、脉冲线性好等特点.     

Design considerations for the rotating electrostatic liquid-film radiator

A lightweight, fully modular radiator design for heat rejection in space is proposed, which is estimated to weigh less than 2 kg per square meter of the effective radiator area. The feature which makes this thin membrane radiator practical is the internal electrostatic field system, which can stop radiator leaks from punctures, sudden accelerations or accidental tears. Preliminary design calculations are presented for a rotating conical radiator, using liquid lithium at an inlet temperature of 800 K. Remarkably low weights of less than 1 kg kW⁻¹ may be attained, with safety factors of two or more for stopping leaks. This is almost an order of magnitude less than the values for current heat pipe designs.     

用于中子吸收剂量测量的量热计

本文介绍我们研制的中子吸收剂量量热计的原理、结构及其测量系统。测量了池式研究用反应堆中的中子吸收剂量并得到满意的结果。该量热计轻便、简单、测量迅速而准确。已精确知道比热数值的其它吸收材料均可采用本设计。     

高温液滴流辐射换热及蒸发特性

本文针对可应用于空间堆的矩形液滴辐射器（LDR）,研究其液滴流的辐射换热及蒸发特性。在传统的高温液滴流辐射换热模型的基础上,添加了液滴流蒸发模型,并将辐射换热模型与蒸发模型进行耦合,在该模型的基础上开发了高温液滴流辐射换热-蒸发特性分析程序LDFAC。将该程序的液滴层温度分布计算结果进行校核,其相对误差不超过1.9%。使用该程序对装载DC705硅油下不同光学厚度及长度的液滴层辐射换热蒸发特性进行了分析。结果表明：在液滴层的光学厚度较大的情况下,液滴层内部的温度分布非常不均匀,液滴层中心的温度没有显著降低,而液滴层接近外表面部分的温度下降较为明显;温度对LDR的系统寿命有着较大影响,温度每降低10 K,系统寿命可提高约450%,同时,液滴层光学厚度越大,系统寿命也越长。     

X-rays generated by relativistic electrons in a waveguide radiator mounted inside a betatron

We have observed X-ray emission from an X-ray waveguide radiator excited by relativistic electrons in the experiments carried out at Tomsk betatron B-35. A stratified radiator of a new type was mounted on a goniometer head inside the betatron toroid. The radiator consisted of the W-C-W layers placed on Si substrate. The photographs of the angular distributions of the radiation generated in the radiator by 20 and 33 MeV electrons showed the waveguide effect of the three-layer structure on X-rays generated in the radiator. The effect appeared in the angular distribution of the radiation as an additional peak attributed to guided X-rays inside a wide cone of usual Bremsstrahlung.     

Cherenkov radiation from relativistic heavy ions taking account of their slowing down in radiator

Combining the SRIM’06 computer code and the formula for spectral-angular distribution of radiation from a particle moving in a medium in arbitrary trajectory, we studied numerically the structure of angular distributions of Cherenkov radiation from moderately relativistic heavy ions (RHI) taking into account the decrease of the ion velocity due to stopping in the radiator. The results obtained clearly show that the width and the fine structure of the Cherenkov radiation in the vicinity of the Cherenkov cone depend strongly on several factors, e.g. the mean and total energy losses, the radiator thickness, the square of the ion charge, the emission wavelength and the refractive index of the radiator material. This might be useful for experiments using RICH detectors for relativistic heavy ions.     

脉冲四极磁铁峰值梯度测量

一、测量原理质子直线加速器中的漂移管四极透镜是由近似半正弦波的脉冲电流励磁的。脉冲底宽约为3.5毫秒,重复频率为每秒10次。四极透镜孔径内的磁场,若只考虑其空间分布,它是中心为零的梯度场,如图1所示。图中B_y、B_x分别表示磁场在y和x方向的分量。     

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     

Operation of the ATLAS muon drift-tube chambers at high background rates and in magnetic fields

In the ATLAS muon spectrometer, large drift-tube chambers are used for precision tracking. The chambers will be operated at a high neutron and /spl gamma/ background resulting in count rates of up to 500 Hz cm/sup -2/ corresponding to 300 kHz per tube. The spatial resolution of the drift tubes is degraded from 82 /spl mu/m without background to 108 /spl mu/m at 500 Hz cm/sup -2/ background count rate. Due to afterpulsing in the Ar/CO/sub 2/ gas mixture used in the drift tubes, ionizing radiation causes more than one hit in a tube within the maximum drift time of about 800 ns which is expected for magnetic field strengths around 1.2 T. In order to limit the count rate, the drift tubes are read out with an artificial dead time of 790 ns which causes an efficiency loss of 23% at a rate of 300 kHz per tube. The space-to-drift-time relationship of the tubes varies with background rate, temperature, and magnetic field strength. The mean magnetic field strength in a muon chamber is 0.4 T on the average, but may vary by up to 0.4 T within a chamber. The space-to-drift-time relationship must therefore be determined in short time intervals with an accuracy better than 20 /spl mu/m using muon tracks and applying corrections for measured magnetic field variations.