快速光电倍增管的新进展

本文主要评论了三类亚纳秒时间分辨的光电倍增管。微通道板管脉冲响应快、线性电流大,其响应半宽度已达187ps。     

Recent Advances in X-Ray Detection Technology

A review is presented of recent developments in x-ray photon detectors and in the associated detector electronics. The first portion of the paper is devoted to a survey of the presently available physical inforrnation on the "intrinsic" resolution of silicon and germanium radiation detectors, proportional counters and NaI(Tl) scintillation crystals. Semiconductor detectors suitable for x-ray applications and low noise electronics are then analyzed in some detail. Discussions follow on scintillation detectors, proportional counters, and "external" photoelectric detectors. Recent spectral achievements and interesting applications are illustrated.     

辐射防护剂的研究进展

人体的细胞和组织受到一定剂量射线照射后,其结构和功能均会发生变化。其主要机制为,电离产生大量自由基后,破坏细胞DNA及内部端粒酶结构,破坏线粒体膜电位稳态,进而导致细胞的凋亡、异常增殖、功能发生改变。本文就现有主要的辐射防护剂和天然药物的抗辐射功能进行简要综述,并阐述其中可能的机制。其中氢巯基类辐射防护剂主要成分为N-乙酰半胱氨酸;维生素类主要是维生素E和维生素C起作用;多糖的种类繁多,植物多糖具有辐射防护作用;免疫调节剂和细胞因子中的粒细胞集落因子有较好的防辐射功效;而天然中药成分14-去氧-11,12-二去氢穿心莲内酯作为一种新的防辐射药物,其作用机制值得进一步深入研究。     

Recent Advances in Gas Scintillation Proportional Counters

Various geometrical configurations for gas scintillation proportional counters have been investigated in order to determine which is best for use in a large volume, high efficiency counter for measuring low energy gamma and x-rays. A xenon filled counter having a rod anode inside a cylindrical cathode appears to provide the best configuration for providing a uniform field and the best resolution over the total volume of the counter. The details of construction and operating characteristics of various shaped counters are described.     

粒子微束辐射生物学效应研究进展

粒子微束能够将单个或精确数目的粒子定点、定位射人靶目标,使得辐射生物学效应的研究由定性走向了定量。本文介绍了辐射目标靶研究,以及低剂量辐射生物学效应、低剂量辐射旁效应和重离子微束辐射生物学效应的研究进展。现代精确粒子微束的建立,有助于进一步研究低剂量辐射和空间辐射等生物学效应。     

辐射防护剂和治疗剂的研究进展

随着核能与核技术的迅速发展及广泛应用,人们接触电离辐射的机会日益增多。辐射防护剂和治疗剂的应用倍受关注,但目前使用的许多辐射防护剂和治疗剂都不太理想。研究人员一直致力于研究高效、低毒的天然辐射防护剂。本文主要关注了化学类、植物和天然中草药的辐射防护剂以及细胞因子和干细胞辐射治疗剂的应用前景。氨磷汀(WR-2721)及相关化合物最具市场前景,但是严重的不良反应限制其临床应用。植物提取物和天然中草药具有毒性小、价格相对低廉、可以口服给药,并且可以通过多种机制发挥作用的优势,因此成为国内外研究关注的热点。细胞因子治疗能够预防或减少急性辐射综合症(ARS)。间充质干细胞(MSC)具有分泌造血生长因子、重建造血微环境、低免疫原性、易于外源基因转染和表达等优点,将其应用于急性辐射损伤的临床治疗具有十分广阔的前景。因此,植物和中草药作为辐射防护剂和MSC作为放射治疗剂的协同应用可能是未来研究的趋势。     

The Self-Consistent Nonlinear Theory of Charged Particle Beam Acceleration by Slowed Circularly Polarized Electromagnetic Waves

The relativistic interaction of charged particle beams with a circularly polarized electromagnetic wave propagating along a uniform guiding magnetic field in the tunneling of a dielectric medium is analyzed. The acceleration mechanism and a self-consistent nonlinear theory are presented for the interaction of relativistic charged particle beams with electromagnetic waves. Numerical results show that the beam particle can be efficiently accelerated in the interaction process.     

Magnetic Field Improvement in End Region of Rectangular Planar DC Magnetron Based on Particle Simulation

For a rectangular planar direct current （DC） magnetron, anomalous target erosion may occur in the curve-out region and inner side of the curved region. One key factor is that the magnetic field in the end region is weaker than that in the straight region, and another important factor may be that there is a circumferential component of the magnetic field in the curved region. Through a calculation of three-dimensional magnetic field for the rectangular magnetron, a magnet structure shimmed by permanent magnet bars and ferromagnetic bars is proposed to solve the above problems. Through a three-dimensional non-self-consistent particle simulation and the Yamamura/Tawara formula, the target erosion profile could be predicted. The simulation results show that for an improved uniformity in magnetic field, the entire target utilization could be much enhanced.     

环境土壤样品中~(99)Tc的分析方法研究进展

随着核能的开发及核医学诊断的发展,~(99)Tc的研究日益受到重视。~(99)Tc具有半衰期长、裂变产额高和迁移性强等特点,在核废物的地质处置、环境安全评价及生物效应方面倍受关注,准确测定环境土壤样品中~(99)Tc的含量显得至关重要。本文在文献调研的基础上较详细总结了Tc的化学性质,并对~(99)Tc分析流程中样品的预处理、化学分离纯化、制源及测量等过程中涉及的主要方法进行了综述,指出了现今分析方法中存在的主要瓶颈,并对环境样品中~(99)Tc的分析做了展望。     

尿中241Am的分析方法研究进展

²⁴¹Am是高毒性的α核素,在常规职业内照射监测及应急测量中均有监测需求。本文系统介绍了尿样中²⁴¹Am分析的各种方法,包括预处理、浓集、分离纯化、制样、测量等环节。典型的化学处理流程包括磷酸钙/草酸钙共沉淀,采用DGA或TRU树脂进行萃取色谱柱分离,在硫酸铵或草酸铵体系中电镀或与Nd/CeF₃微沉积制成α源。测量仪器可以用α谱仪、液闪谱仪、γ谱仪等放射性测量仪器,或电感耦合等离子体质谱(ICP-MS)、加速器质谱(AMS)等质谱测量仪器。