An online monitor ionization chamber used in particle therapy

The clinical trials of tumor therapy using heavy ions beam C-12 are now in progress at Institute of Modem Physics in Lanzhou. In order to achieve the precise radiotherapy with the high energy C-12 beam in active pencil beam scanning mode, we have developed an ionization chamber(IC) as an online monitor for beam intensity and also a dosimeter after calibration. Through the choosing of working gas and voltage, optimizing of the electrics and the read-out system, calibrating the linearity, the detector system provide us one of the simple and highly reliable way to monitoring the beam during the active pencil beam scanning treatments. The measurement results of this detector system show that it could work well under the condition of high energy C-12 beam in active pencil beam scanning mode.

空间PMOS剂量计的研究

在我国开展卫星运行轨道粒子辐射环境总剂量探测技术的研究工作是目前一项重要任务。PMOS剂量计是一种新颖的电离辐射总剂量实时监测技术，本文通过全面系统地研究PMOS剂量计基本原理和物理机制，以最终解决此项技术在空间应用中的多项关键技术难题为目的，研制出可靠的星用PMOS剂量计，并成功地运用于“实践五号”科学实验卫星。研究结果打破了国外相关技术封锁。研制的星用PMOS剂量仪性能技术指标与国外同类产品相当，取得圆满的探测结果。本文采用了动态阈电压跟踪测量技术和I-V亚阈分析技术观测分析氧化物电荷与界面态微观参数的变化，系统全面地对辐射敏感PMOSFET进行了多种辐射条件、偏置条件、温度条件下的响应规律及退火行为的研究，从电离辐射类型、探头工作的温度环境、偏置电场、探头结构等角度获得了各自对探头辐射响应规律的影响机制，掌握了影响探头辐射灵敏度、线性度、稳定度的外部使用条件的微观作用机理。建立了适宜于空间环境的PMOS剂量仪地面标定技术，研究并发展了温度补偿技术，为该技术的空间工程应用寻求到低退火、高稳定、高灵敏度的探头应用方式。对新型探头结构－级联结构的辐照响应和二次辐照进行了深入实验探索，为提高PMOS剂量计的灵敏度等技术指标找到了又一条技术途径。最终设计出适宜于空间应用的简捷、可靠性高、易于控制、低功耗的剂量仪电子学线路。本项研究成果的创新性、先进性在于：（1）获得偏置电场影响PMOS剂量计辐射响应特性（灵敏度、线性度、稳定性）的机理模型；（2）研究了PMOS辐射敏感场效应晶体管对~(60)Co γ和电子响应的等效关系以及在瞬态辐照环境下的响应规律。（3）研究了PMOS剂量计温度、偏置退火规律以及室温长期退火行为，揭示了影响退火的微观机制；（4）研究比较了不同形式的多管级联结构在不同辐照偏置条件下的辐照响应特性，获得了改善PMOS剂量计辐射响应特性的人面指标的又一解决方案；（5）建立了有效的温度补偿技术和低剂量率标定方法。（6）运用上述研究成果，研制出性能指标与国旬同类产品性能相当的第一代国产星用PMOS剂量仪。

A preliminary study on thermoluminescence characteristics of sediments from the North Pacific

Thirty-eight surficial deposit samples were collected from the equatorial North Pacific, and the natural thermoluminescence (TL) characteristics of both bulk and clay fraction samples ( < 2 mu m fractions) were studied by the FJ427 - Al automatic TL Dosimeter for the first time. With the measurements of clay mineral composition, element composition by XRD and ICP, the correlations between TL intensity and sedimentary environment proxies were analyzed, such as water depth, ratio of FeO to Fe2O3 contents, LOI, and major clay mineral concentration, and it was found the bulk sample's TL signal was stronger than the clay ones. Usually, increase in the clay components may result in the decrease of TL intensity. From the shape of TL curves, the pelagic sediments can be divided into two groups: the majority group has two glow peaks, in general, the first peak is broad and flat, but the second narrow and sharp; the minority group only has a single peak because the first is absent. The peak centers of TL curves are almost fixed, falling in the temperature sections 230 similar to 260 and 390 similar to 405 degrees C respectively. Lorentz model packed in the Origin 7.5 was chosen to deal with the TL curves. From the processing results, three parameters ( H, C and A), corresponding to the height, center, and kurtosis of TL curve, were obtained to describe the curve characteristics. The correlations between TL curve parameters and sedimentary environment proxies were also calculated. On the basis of the above work, the relationship between TL characteristics and sediment type, mineral composition, sedimentary environment of surface sediments was discussed in the study area, and a conclusion is: sediments from the environment of shallower water, higher organic contents and weaker reductivity have stronger TL signals.