重离子照射细胞存活率计算的局部效应模型的缺陷

概略介绍了重离子照射细胞存活率计算的局部效应模型， 讨论了该模型在理论假设和计算方法上存在的问题， 指出了其中的任意参数， 并通过计算检验了这些任意参数的取值变化对细胞存活率计算结果的影响。 结果表明, 细胞存活率计算结果严重依赖于这些任意参数的取值。 Scholz Kraft’s Local Effect Model (LEM) for the calculation of cell survival after heavy ion irradiation was briefly introduced. Basing on the energy conservation law and the definition of the dose， the disfigurement of LEM in theoretical framework and methods was discussed. Two artificial parameters were found in LEM， and the result obtained from this model seriously depends on these two parameters.     

Study on the dose rate upset effect of partially depleted silicon-on-insulator static random access memory

This paper implements the study on the Dose Rate Upset effect of PDSOI SRAM (Partially Depleted Silicon-On-Insulator Static Random Access Memory) with the Qiangguang-I accelerator in Northwest Institute of Nuclear Technology. The SRAM (Static Random Access Memory) chips are developed by the Institute of Microelectronics of Chinese Academy of Sciences. It uses the full address test mode to determine the upset mechanisms. Specified address test is taken in the same time. The test results indicate that the upset threshold of the PDSOI SRAM is about 1x10⁸Gy(Si)/s. However, there are few bits upset when the dose rate reaches up to 1.58x10⁹Gy(Si)/s. The SRAM circuit can still work after the high level γ ray pulse. Finally, the upset mechanism is determined to be the rail span collapse by comparing the critical charge with the collected charge after γ ray pulse. The physical locations of upset cells are plotted in the layout of the SRAM to investigate the layout defect. Then, some layout optimizations have been taken to improve the dose rate hardened performance of the PDSOI SRAM.     

质子治疗装置的束流扩展研究

对扩展质子束流的双环双散射体方法进行了探讨, 研究了它的束流分布函数与束利用率和束分布均匀性的关系, 以及照射野形成距离的改变和束偏离对束流分布的影响. 计算了散射体的厚度与照射野的关系, 并提出了用液体散射体代替固体散射体的可能性.     

用NMR测定辐射剂量

本文介绍了利用琼酯糖-亚铁为剂量液,经辐照,产生糖的自由基、质子和三价铁离子。根据Fe~(3+)本身具有的弛豫能力-减小弛豫时间,利用NMR法测量出不同剂量下的T_1值并获得整个辐照过程弛豫速率随剂量分布的曲线。还观察到整个辐射过程体系氧化还原反应的动态变化过程。     

Advancements in internationally accepted standards for radiation processing

Three subcommittees of the American Society for Testing and Materials (ASTM) are developing standards on various aspects of radiation processing. Subcommittee E10.01 “Dosimetry for Radiation Processing” has published 9 standards on how to select and calibrate dosimeters, where to put them, how many to use, and how to use individual types of dosimeter systems. The group is also developing standards on how to use gamma, electron beam, and x-ray facilities for radiation processing, and a standard on how to treat dose uncertainties. Efforts are underway to promote inclusion of these standards into procedures now being developed by government agencies and by international groups such as the United Nations' International Consultative Group on Food Irradiation (ICGFI) in order to harmonize regulations and help avoid trade barriers.

Subcommittee F10.10 “Food Processing and Packaging” has completed standards on good irradiation practices for meat and poultry and for fresh fruits, and is developing similar standards for the irradiation of seafood and spices. These food-related standards are based on practices previously published by ICGFI.

Subcommittee E10.07 on “Radiation Dosimetry for Radiation Effects on Materials and Devices” principally develops standards for determining doses for radiation hardness testing of electronics. Some, including their standards on the Fricke and TLD dosimetry systems are equally useful in other radiation processing applications.     

Effect of dose rate on water absorption of partially hydrolyzed polyacrylamide-co-poly(vinyl pyrrolidone) superabsorbents

Partially hydrolyzed polyacrylamide-poly(1-vinyl-2-pyrrolidone) copolymer was synthesized by γ-irradiation through the control of dose rate. Conversion, degree of polyacrylamide hydrolysis, and water absorption of the polymers are reported.     

Opti-Chromic dosimeters for low-dose applications (0.1 Gy to 10 kGy)

Opti-chromic dosimeters have been developed which measure absorbed doses to as low as 0.1 Gy. These detectors consists of a radiation sensitive solution contained in fluorinated ethylene-propylene (FEP) tubing by borosilicate beads. Three formulations are presented, covering a range of absorbed doses from 0.1 to 3000 Gy.     

Research on radiation-induced color change of white topaz

In the present study, a method of producing sky blue topaz is studied. A 3–5 MeV scanning electron beam linear accelerator (which is currently used for processing semiconductor devices) was employed to change the color of white topaz under room-temperature conditions, together with a cooling device. A radiation-induced ion color center is formed in white topaz by an electron beam. To finish the irradiation, the total dose needs to be more than 5×10⁷–1×10⁸ Gy, the temperature of heat-treatment was between 180°C and 280°C in air conditions, after a while, a sky blue topaz was obtained.

There was a bright color and no radioactivity was formed in the sky blue topaz by this production method.     

Modification on liquid retention property of cassava starch by radiation grafting with acrylonitrile. I. Effect of γ-irradiation on grafting parameters

Radiation modification on liquid retention properties of native cassava starch, gelatinized at 85°C, by graft copolymerization with acrylonitrile was carried out by mutual irradiation to gamma-rays. A thin aluminum foil was used to cover the inner wall of the reaction vessel, so that the homopolymer concentration was reduced to be less than 1.0% with a distilled water retention value of 665 g/g of the dry weight of the saponified grafted product. Confirmation of graft copolymerization and saponification reactions was made by the infrared spectrophotometric technique. The combined effect of radiation parameters in terms of an irradiation time and a dose rate to the total dose on the extent of the grafting reaction expressed in terms of grafting parameters which directly influenced liquid retention values was evaluated in conjunction with statistical analysis.     

Effect of dose rate and comparison of different media used in the recuperation of gamma irradiated listeria monocytogenes

D₁₀ of different strains of Listeria monocytogenes (LM) gamma irradiated with varying dose-rates are were established. Our results seem to indicate that the dose-rate does not exert a significant effect on their D₁₀. D₁₀ obtained with LM irradiated and plated on Oxford agar showed the highest value.