载人航天微型磁等离子体辐射防护地面实验

星际飞行中的辐射主动防护问题一直是人们研究的焦点,低地轨道飞行中采用的质量厚度屏蔽已经不能满足要求,必须寻找新的空间辐射主动防护技术和方法。在电场、磁场、等离子体膨胀等众多新的主动防护方法中,选取了等离子体膨胀辐射防护技术作为研究对象;通过注入高能等离子体使磁场膨胀,从而使空间带电粒子偏转以减少空间辐射对飞行器及航天员的辐射损伤。通过原理性实验,证明了在真空状态下,等离子体的注入可以引起周围磁场发生变化,且同一个点的磁感强度随着射频电源输入功率的增大而增大。其机理还有待进一步的研究。     

Cost of the Radiation Damage in the ALARA Concept

The principles for determining the cost of radiation risk as a method of optimizing risk are described. The interrelationship of various components of risk is examined. The goal of optimization as a requirement to decrease the aggregate risk is formulated. It is noted that mathematical simulation is unreliable for determining the cost of risk and damage. An approach to determining the cost of risk on the basis of direct analysis of the financial costs is proposed. The result of risk cost assessment is presented. The use of the proposed approach is demonstrated for a hypothetical example. 18 references.     

A Unique Radiation Detection Concept for a Miniature Particle Spectrometer

A three-channel particle spectrometer employing charge multiplying semiconductor detectors and tunnel diode discriminators has been constructed, environmentally tested and calibrated to detect low energy protons. The three channels have been calibrated to detect protons > 0.5 MeV, >1.5 MeV, and >45 MeV. The instrument is five orders of magnitude more sensitive to protons than to electrons above 500 KeV which ensures successful operation in the midst of electrons injected into the earth's radiation belt from the starfish experiment. The unique features of this instrument are: (1) Discriminates uniquely against a low energy photon background. (2) Electrical noise immunity due to the integration of the detector to the discriminator to give a high signal level output to the binary counter. (3) Thermally generated noise does not compete with the detected signal at the discriminator. The miniature instrument is a result of simple detection circuitry and the use of microelectronic elements in the data compressor. The data compressor consists of three binary counters having a storage capability of 218-1 bits. Each counter has a thin film network to octally encode the binary counts into an analog voltage. The counters have a 1 MHz count rate. This paper describes the instrument design and its characteristics which reflect the design constraints of the flight vehicle. The calibration of the instrument for a small half-angle cone of low energy protons from a Van De Graaff accelerator is discussed.     

A New Filter Concept Yielding Improved Resolution and Throughput in Radiation Detection Systems

We introduce a new filtering method capable of increasing measurement resolution and processed data throughput through a nonstandard baseline restoration technique. An overall optimization of the signal-to-noise ratio and of the processing efficiency is performed and new filters are obtained. The hardware implementation exploits the resources of a FPGA and is not significantly resource-hungrier than standard setups. The experiments confirm theoretical expectations. The obtained resolution is 1.8 keV on the 1.173 MeV peak: This result is an improvement with respect to the one achievable with the standard optimum filter in the same conditions by about a 10% factor; the data rate is improved too.     

辐射防护概念的拓展与环境放射防护

为了真正落实法规中强调的保护环境的要求,现行辐射防护体系应该从单纯对人类的防护,拓展到对整个环境的电离辐射防护.其中,建立对非人类物种的危害评价体系是主要的内容之一,也是本项工作开展的难点.本文介绍了目前国际上在建立生物剂量模型研究中的最新进展,对我国在这方面的研究工作提出了建议.     

Radiation Damage to Chromosomes

The foregoing, I think, does give some idea of the types of things that can be done and have been done in experiments on chromosome aberrations. The studies I discussed represent basic radiobiological research on chromosomes. I would like to point out, however, that the information obtained from such basic studies is being used in a practical way. For instance, in the field of cancer radiotherapy knowledge of changes in chromosome sensitivity during the cell cycle is being exploited to devise rational dose fractionation procedures for treatments. Furthermore, attempts are now being made to either oxygenate tumor cells (which are ordinarily anoxic) or to use more densely ionizing radiations. The reason for this is that either method will obviate the difference in radiosensitivity between anoxic tumor cells, which we want to kill, and oxygenated normal cells, which we want to spare. As a basic scientist, I find it particularly gratifying to see that, ever more frequently, concepts     

正常工作状态与零偏置JFET输入运算放大器的辐射损伤

对处于正常工作和零偏置状态的JFET输入运算放大器,进行了高低剂量率辐射试验。结果表明,工作状态影响JFET运放电路的辐射效应和辐射损伤。正常工作状态下,JFET输入运算放大器表现出时间相关效应,而零偏置状态下则具有低剂量率损伤增强效应。高剂量率或低剂量率辐射情况下,正常工作的JFET输入运放电路参数退化大于或小于零偏置状态。高剂量率辐射会在JFET输入运放的基本单元双极晶体管产生氧化物正电荷和界面陷阱。从氧化物正电荷和界面态与工作状态的关系方面,对JFET运放电路的退化行为进行了解释。     

Radiation Dosage Due to Neutrons Produced in a Vehicle by Protons in the Trapped Radiation Belt

The rate of production of neutrons by geomagnetically trapped protons incident on a vehicle was measured by a neutron counting system carried into the trapped radiation belt by a pod flow piggy back on an Atlas rocket on December 19, 1961. The flux of neutrons produced by radiation belt protons incident on the pod was determined to be at least 700 neutrons/(cm2 sec); the actual value depends somewhat on the energy spectrum of the neutrons. This flux was estimated to be equivalent to a dose rate in tissue of 0.10 rems/hr. On the basis of proton flux measurements made in the radiation belt by Freden and White, a calculation was made of the tissue dosage which would have been received in the same environment directly from protons. These calculations were made by obtaining a numerical integration of the dE/dx times RBE times flux product over the entire energy spectrum. The total dose calculated amounted to 2.78 rems/ hr. Further calculations were made to estimate the dose rates which would have been received by tissue in the same environment but with varying amounts of shielding around the vehicle. The proton dose is, of course, reduced by the shield but the neutron dose actually increases as the shielding thickness is increased. It is seen that the neutron dose equals the proton dose at .3 rems/hr. when aluminum shielding of 2.6" surrounds the vehicle and it exceeds the proton dose with thicker shielding.     

ICRP Publication 105. Radiation protection in medicine

This report was prepared to underpin the Commission's 2007 Recommendations with regard to the medical exposure of patients, including their comforters and carers, and volunteers in biomedical research. It addresses the proper application of the fundamental principles (justification, optimisation of protection, and application of dose limits) of the Commission's 2007 Recommendations to these individuals. With regard to medical exposure of patients, it is not appropriate to apply dose limits or dose constraints, because such limits would often do more harm than good. Often, there are concurrent chronic, severe, or even life-threatening medical conditions that are more critical than the radiation exposure. The emphasis is then on justification of the medical procedures and on the optimisation of radiological protection. In diagnostic and interventional procedures, justification of procedures (for a defined purpose and for an individual patient), and management of the patient dose commensurate with the medical task, are the appropriate mechanisms to avoid unnecessary or unproductive radiation exposure. Equipment features that facilitate patient dose management, and diagnostic reference levels derived at the appropriate national, regional, or local level, are likely to be the most effective approaches. In radiation therapy, the avoidance of accidents is a predominant issue. With regard to comforters and carers, and volunteers in biomedical research, dose constraints are appropriate. Over the last decade, the Commission has published a number of documents that provided detailed advice related to radiological protection and safety in the medical applications of ionising radiation. Each of the publications addressed a specific topic defined by the type of radiation source and the medical discipline in which the source is applied, and was written with the intent of communicating directly with the relevant medical practitioners and supporting medical staff. This report consolidates that advice.     

Techniques to Maximize Software Reliability in Radiation Fields

Microprocessor system failures due to memory corruption by single event upsets (SEUs) and/or latch-up in RAM or ROM memory are common in environments where there is high radiation flux. Traditional methods to harden microcomputer systems against SEUs and memory latch-up have usually involved expensive large scale hardware redundancy. Such systems offer higher reliability, but they tend to be more complex and non-standard. At the Space Astronomy Laboratory we have developed general programming techniques for producing software which is resistant to such memory failures. These techniques, which may be applied to standard off-the-shelf hardware, as well as custom designs, include an implementation of our Maximally Redundant Software (MRS) model, error detection algorithms and memory verification and management.     

A GUPIX-based approach to interpreting the PIXE-plus-XRF spectra from the Mars Exploration Rovers: I. Homogeneous standards

A new fitting code has been developed on the basis of GUPIX for application to alpha-particle X-ray spectrometers, which employ simultaneously two excitation mechanisms - XRF and PIXE - for elemental analysis of a single sample, and which are principal analytical instruments on the Mars Exploration Rovers. We present some of the basic aspects of our approaches to spectrum fitting, and we use a subset of the original calibration spectra from the MER mission to test our approach to standardization. This test is limited to results from homogeneous standards such as pure elements, oxides and chlorides, and simple minerals that comprise a single phase. The important, additional issues of multiple mineral phases that arise when geochemical reference materials are used as standards are dealt with in the subsequent paper. It is shown that an accurate standardization can be achieved with only minimal resort to empirical corrections. Attention is paid to fitting of the Compton scatter feature and to the extraction of the Compton-Rayleigh scatter ratio, because the latter quantity is the basis of our method for determining “invisible” light element (water, ice and carbonate) content of Martian samples.     

空间辐射剂量学浅谈

空间辐射剂量学是辐射防护领域最具挑战性的学科之一。本文着重介绍：(1)低地球轨道空间辐射的主要来源：银河系宇宙射线,地球磁场捕获的高能电子和质子形成的地球辐射带．太阳粒子事件以及宇宙射线与地球大气相互作用产生的反照中子和质子;(2)各种辐射成分对剂量的贡献;(3)空间辐射剂量的测量方法。主要介绍有源探测器和无源探测器,它们的使用范围以及各自的优缺点。同时,简要介绍了国外目前使用的主要探测器及其特点,并对国际剂量学的发展历史作了简单的回顾。     

Radiation Damage to Satellite Electronic Systems

Space radiation can cause damage to satellite electronic systems. The amount of damage can be determined if the radiation induced component changes are known and if the behavior of the electronic system as a function of component changes can be determined. By relating space radiation damage to neutron damage, a large amount of semiconductor device data becomes available for satellite damage predictions. To obtain circuit and system performance from component performance in an economical way analysis is combined with experimental techniques. The experimental technique involves substitution of radiation degraded components into the circuit and measurement of its performance. The application of such techniques to satellite electronics indicates that performance degradation caused by lifetime reduction resulting from space radiation can generally be kept small, particularly, if modern high frequency transistors are used. However, ionization of the semiconductor environment from the artificial electron belt may cause significant surface effects resulting in a reduction in device performance even for shielding of several gm/cm2.     

空间辐射环境概述

从宇宙射线的初级粒子和次级粒子入手,考虑地球磁场对入射粒子的影响,对航线和近地轨道飞行等空间活动区域内的辐射环境进行介绍。宇宙射线初级粒子注量和能谱与太阳活动期的活动程度相关,初级粒子和次级粒子在地球大气中的注量分布与大气深度和地磁截止刚度密切相关。随着大气深度的增加,吸收剂量减小;对于相同大气深度,随着地磁截止刚度的增加,粒子总注量减小。     

Soft Errors Due to Protons in the Radiation Belt

This paper examines the problem of soft errors in semiconductor devices caused by the protons in the radiation belts. The errors can be produced by a variety of nuclear reactions in silicon. A previous paper presented a calculation of the likelihood of some of these reactions. This information can be combined with knowledge of the proton environment in order to estimate the upset rate for various devices in spacecraft. This paper discusses the proton environment, the effect of spacecraft shielding, the various proton induced reactions in silicon, the calculation of soft error sensitivity, and the soft error rate in a representative satellite.