核电站工作场所中子能谱和周围剂量当量率测量

中子周围剂量当量是核电站辐射防护监测的主要对象之一,而中子周围剂量当量的评估强烈依赖中子的能量分布。利用自制的多球谱仪对秦山第三核电有限公司（TQNPC）重水反应堆安全壳内5个位置的中子能谱和周围剂量当量率进行了测量。该谱仪由1个³He正比计数器以及9个2.5～12英寸不同直径的聚乙烯球组成,响应函数通过MCNP程序计算,并利用标准²⁵²Cf中子源进行了校准和验证。通过测量的中子能谱,获得了不同工作区域的中子周围剂量当量率及其能量分布,并与中子周围剂量当量率仪和CR-39径迹蚀刻探测器的测量结果进行了比较,为核电站中子剂量的监测提供了相关参考数据。     

中国1987—1990年科学实验卫星中空间辐射剂量信息的热释光分析方法

本文介绍了实验卫星中空间辐射剂量信息的热释光分析方法。应用LiF(Mg,Cu,P)探测器及程序加热方法,分析测定了几次实验卫星中空间辐射日平均剂量,均在20mrad/d以下。应用LiF(Mg,Ti)和Caso_4(Tm)探测器及发光曲线反卷积分析方法,研究了探测器本底荧光与低温峰影响的减除技术和高LET粒子造成的微观剂量分布不均匀情况。     

空间中子辐射及其测量技术

空间辐射环境包含大量高能带电粒子,其与航天器的结构材料相互作用会产生次级中子辐射,由于这些中子的平均品质因子是带电粒子的约4~5倍,因而对生物组织的剂量当量相对贡献更大。由于中子与物质的作用机制更为复杂,测量难度大,使得准确测量空间中子注量及其剂量当量贡献成为空间辐射剂量学中最具挑战性的工作之一。主要介绍了空间中子辐射的产生机制以及国外相关测量方法及其相关校准技术的研究状况。     

基于CLYC闪烁体的中子能谱测量及反演方法

空间中子是影响航天器和航天员安全的重要辐射要素之一。优化中子探测器，提高测量效率，提升反演精度是中子测量的难点。中国空间站将搭载一种基于新型中子探测材料Cs2LiYCl6:Ce（CLYC）闪烁体的中子探测器，该探测器具有同时测量热中子和快中子，以及探测效率高等特点。针对该新型探测器的中子能谱反演，分析了不同能量中子在该探测器中的响应特点，分析了中子反演常用的概率迭代法和非负最小二乘（NNLS）法的优缺点，考虑到这2种方法在CLYC探测器反演应用中的不足，提出了基于增广矩阵的非负最小二乘（AM-NNLS）法。数值实验结果表明:AM-NNLS法具有反演运算效率高和反演相对误差小的特点，验证了所提方法的有效性。      

电子照射对硅漂移探测器性能的影响

由于高能电子辐射的长期照射,新一代太阳X射线探测器硅漂移传感器的探测性能可能发生变化.通过用电子放射源模拟空间电子对硅漂移探测器进行辐射照射试验,以测试电子照射对传感器能量分辨率、效率、信号幅度等性能的影响.试验结果表明,长期的电子照射造成硅漂移探测器面损伤和体损伤,使其漏电流增大,信号幅度减小,能量分辨率也受到照射的影响,而探测效率未发生变化.     

(70~100)MeV准单能中子参考辐射场设计

国内基于串列加速器建立了144keV~15MeV的单能中子参考辐射场，解决了20MeV以下能区中子探测器注量、剂量等参数的量值溯源，但尚未建立20MeV以上能区准单能中子参考辐射场。随着航天空间中子探测任务的需要以及地面高能质子加速器的发展，20MeV以上能区准单能中子参考辐射场需求越来越突出。发展20MeV以上能区高能中子参考辐射场对于满足国防需求、推动中子计量学科发展具有重要意义。     

(70~100)MeV准单能中子参考辐射场设计

国内基于串列加速器建立了144keV~15MeV的单能中子参考辐射场，解决了20MeV以下能区中子探测器注量、剂量等参数的量值溯源，但尚未建立20MeV以上能区准单能中子参考辐射场。随着航天空间中子探测任务的需要以及地面高能质子加速器的发展，20MeV以上能区准单能中子参考辐射场需求越来越突出。发展20MeV以上能区高能中子参考辐射场对于满足国防需求、推动中子计量学科发展具有重要意义。     

以载荷为中心的暗物质探测卫星机电热一体化设计

暗物质粒子探测卫星是中国第一颗空间高能探测卫星,用于实现5GeV~10TeV大动态范围高能宇宙线（电子、正电子、伽马射线等）能谱测量.卫星有效载荷包括BGO量能器、硅阵列探测器、塑闪阵列探测器和中子探测器,是目前中国发射的载荷比最大的卫星.本文介绍了卫星相关技术方案,包括技术指标、轨道方案、工作模式及系统组成等,突出了其以载荷为中心的机电热一体化设计特点.      

航天员受银河宇宙线辐射的剂量计算

在近地空间(LEO)和深空探测中,航天员遭受的辐射风险主要来自于银河宇宙线(GCR)照射.银河宇宙线的辐射剂量是航天员辐射风险评价的基础.国际放射防护委员会(ICRP)于2013年提出了新的航天员空间辐射剂量估算方法,以更准确给出空间重离子辐射的剂量.基于此方法,开发了宇宙线粒子在物质中输运的蒙特卡罗程序,并在程序中实现用中国成年男性人体数字模型来仿真航天员.采用该程序计算了粒子(Z=1~92)各向同性照射航天员时器官的通量-器官剂量转换因数,并估算出航天员在近地轨道空间受银河宇宙线辐射的剂量.     

暗物质粒子探测卫星BGO量能器热控设计与验证

暗物质粒子探测卫星是2015年12月发射的中国自主设计建造的空间天文实验卫星,主要包括塑闪阵列探测器、硅阵列探测器、BGO量能器与中子探测器四个探测器.BGO量能器是暗物质粒子探测卫星的核心探测器,主要任务是精密测量高能宇宙线粒子的能量,并通过比较簇射沉积能量的空间分布,进行粒子种类鉴别.本文结合BGO量能器工作原理,分析了BGO量能器热控设计需求与约束,进行了单机热控设计.根据热控设计方案,进行有限元仿真分析,开展了单机飞行件的真空热平衡试验.分析与试验结果表明,热控设计方案合理有效,能够满足需求.      

Investigation of dose and flux dynamics in the Liulin-5 dosimeter of the tissue-equivalent phantom onboard the Russian segment of the International Space Station.

Described is the Liulin-5 active dosimetric telescope designed for measurement of the space radiation dose depth-distribution in a human phantom on the Russian Segment of the International Space Station (ISS). The Liulin-5 experiment is a part of the international project MATROSHKA-R on ISS. The MATROSHKA-R project is aimed to study the depth-dose distribution at the sites of critical organs of the human body, using models of human body-anthropomorphic and spherical tissue-equivalent phantoms. The aim of Liulin-5 experiment is a long term (4-5 years) investigation of the radiation environment dynamics inside the spherical tissue-equivalent phantom, mounted in different compartments. Energy deposition spectra, linear energy transfer spectra, and flux and dose rates for charged particles will be measured simultaneously with near real time resolution at different depths of the phantom by means of three silicon detectors. Data obtained together with data from other active and passive dosimeters will be used to estimate the radiation risk to the crewmembers, which verify the models of radiation environment in low Earth orbit. Presented are the test results of the prototype unit. Liulin-5 will be flown on the ISS in the year 2003.     

A review of instruments and methods for dosimetry in space

Instruments and methods recently used for space radiation dosimetry are reviewed for the purposes of comparison and reference. Passive detection methods mentioned include track-etch, luminescent, nuclear emulsion, and metal foil detectors. These can provide a reliable source of data for all types of radiation, but often require processing that cannot occur in space. Experimental methods of LET determination using TLDs, such as the high temperature peak ratio (HTR) method, are also discussed. Portable readout passive detectors including Pille, MOSFET, and bubble detector systems provide a novel alternative to traditional passive detectors, but research is more limited and their widespread use has yet to be established. Active detectors including DOSTEL, CPDS, RRMD-III, TEPC, R-16, BBND, and the Liulin series are examined for technical details. These instruments allow the determination of dose in real-time, and some can determine LET of incident particles by measuring energy deposition over a known path-length, but size and power consumption limit their practical use for dosimetry. Improved neutron dosimetry and development of a small active or portable readout personnel dosimeter capable of accurate LET determination are important steps for managing the effects of long-term exposure to the space radiation environment.     

Depth dose measurements with the Liulin-5 experiment inside the spherical phantom of the MATROSHKA-R project onboard the International Space Station

The Liulin-5 experiment is a part of the international project MATROSHKA-R on the Russian segment of the ISS, which uses a tissue-equivalent spherical phantom equipped with a set of radiation detectors. The objective of the MATROSHKA-R project is to provide depth dose distribution of the radiation field inside the sphere in order to get more information on the distribution of dose in a human body. Liulin-5 is a charged particle telescope using three silicon detectors. It measures time resolved energy deposition spectra, linear energy transfer (LET) spectra, particle flux, and absorbed doses of electrons, protons and heavy ions, simultaneously at three depths along the radius of the phantom. Measurements during the minimum of the solar activity in cycle 23 show that the average absorbed daily doses at 40 mm depth in the phantom are between 180 μGy/day and 220 μGy/day. The absorbed doses at 165 mm depth in the phantom decrease by a factor of 1.6–1.8 compared to the doses at 40 mm depth due to the self-shielding of the phantom from trapped protons. The average dose equivalent at 40 mm depth is 590 ± 32 μSV/day and the galactic cosmic rays (GCR) contribute at least 70% of the total dose equivalent at that depth. Shown is that due to the South Atlantic Anomaly (SAA) trapped protons asymmetry and the direction of Liulin-5 lowest shielding zone the dose rates on ascending and descending nodes in SAA are different. The data obtained are compared to data from other radiation detectors on ISS.     

Instrumentation for investigation of the depth-dose distribution by the Liulin-5 instrument of a human phantom on the Russian segment of ISS for estimation of the radiation risk during long term space flights.

Described is the Liulin-5 experiment and instrumentation, developed for investigation of the space radiation doses depth distribution in a human phantom on the Russian Segment of the International Space Station (ISS). Liulin-5 experiment is a part of the international project MATROSHKA-R on ISS. The experiment MATROSHKA-R is aimed to study the depth dose distribution at the sites of critical organs of the human body, using models of human body-anthropomorphic and spherical tissue-equivalent phantoms. The aim of Liulin-5 experiment is long term (4-5 years) investigation of the radiation environment dynamics inside the spherical tissue-equivalent phantom, mounted in different places of the Russian Segment of ISS. Energy deposition spectra, linear energy transfer spectra, flux and dose rates for protons and the biologically-relevant heavy ion components of the galactic cosmic radiation will be measured simultaneously with near real time resolution at different depths of the phantom by a telescope of silicon detectors. Data obtained together with data from other active and passive dosimeters will be used to estimate the radiation risk to the crewmembers, verify the models of radiation environment in low Earth orbit, validate body transport model and correlate organ level dose to skin dose. Presented are the test results of the prototype unit. The spherical phantom will be flown on the ISS in 2004 year and Liulin-5 experiment is planned for 2005 year.     

Radiation measurements aboard NASA ER-2 high altitude aircraft with the Liulin-4J portable spectrometer.

The risks to aircrew health posed by prolonged exposure to low levels of ionizing radiation at aircraft altitudes have recently received renewed attention. Civil and military aircraft currently on the drawing board are expected to operate at higher altitudes (>12 km) and fly longer ranges than do existing aircraft, thereby exposing their crews to higher levels of ionizing radiation, for longer periods of time. We are currently carrying out dosimetric measurements of the ionizing radiation environment at approximately 20 km altitude using portable Si detectors aboard NASA's two ER-2 high altitude research aircraft. The instruments, Liulin-4J, have been extensively calibrated at several particle accelerators. With these instruments, we can measure not only absorbed dose, but also variation of the absorbed dose as a function of time. We report radiation dose measurements as function of time, altitude, and latitude for several ER-2 missions.     

Space radiation dosimetry using bubble detectors.

Bubble detectors--a new development in radiation detection--has only recently been used for radiation measurements in space. One important characteristic of the bubble detector is that it operates on a phenomenon which bears considerable resemblance to biological response. Recent experimental results from irradiating bubble detectors with high-energy heavy ions point to the need to re-examine the methodology used for assessing space radiation and the relevance of conventional quantities such as dose equivalent for space dosimetry. It may be that biological hazard associated with the intensely ionizing events--associated with nuclear fragmentation but delivering relatively small dose equivalent--may be much more important than that associated with lightly ionizing events which comprise the bulk of the conventional radiation dose equivalent.     

Radiation measurements inside a human phantom aboard the International Space Station using Liulin-5 charged particle telescope

Liulin-5 is a particle telescope developed for the investigation of the radiation environment within the Russian spherical tissue-equivalent phantom on the International Space Station (ISS). Liulin-5 experiment is conducted aboard the Russian segment of ISS since 28 June 2007 as an adherent part of the international project MATROSHKA-R. The main objective of Liulin-5 experiment is to study the depth-dose distribution of the different components of the orbital radiation field in a human phantom. Additional objectives are mapping of the radiation environment in the phantom and its variations with time and orbital parameters (such as solar cycle, solar flare events, inclination and altitude). Liulin-5 is an active instrument, capable to provide real-time radiation data for the particle flux and dose rates, energy deposition and LET spectra. Data are recorded automatically on memory cards, periodically transported to ground by returning vehicles. In this report we present some first results from data analysis including energy deposition spectra, absorbed dose, dose rate and flux distribution measured simultaneously at 3 different depths of phantom’s radial channel and linear energy transfer (LET) spectrum. Data discussed are for the period July 2007–April 2008.     

Space Shuttle drops down the SAA doses on ISS

Long-term analysis of data from two radiation detection instruments on the International Space Station (ISS) shows that the docking of the Space Shuttle drops down the measured dose rates in the region of the South Atlantic Anomaly (SAA) by a factor of 1.5–3. Measurements either by the R3DE detector, which is outside the ISS at the EuTEF facility on the Columbus module behind a shielding of less than 0.45 g cm⁻², and by the three detectors of the Liulin-5 particle telescope, which is inside the Russian PEARS module in the spherical tissue equivalent phantom behind much heavier shielding demonstrate that effect. Simultaneously the estimated averaged incident energies of the incoming protons rise up from about 30 to 45 MeV. The effect is explained by the additional shielding against the SAA 30–150 MeV protons, provided by the 78 tons Shuttle to the instruments inside and outside of the ISS. An additional reason is the ISS attitude change (performed for the Shuttle docking) leading to decreasing of dose rates in two of Liulin-5 detectors because of the East–West proton fluxes asymmetry in SAA. The Galactic Cosmic Rays dose rates are practically not affected.     

Calibration results obtained with Liulin-4 type dosimeters.

The Mobile Radiation Exposure Control System's (Liulin-4 type) main purpose is to monitor simultaneously the doses and fluxes at 4 independent places. It can also be used for personnel dosimetry. The system consists of 4 battery-operated 256-channel dosimeters-spectrometers. We describe results obtained during the calibrations of the spectrometers at the Cyclotron facilities of the University of Louvain, Belgium and of the National Institute of Radiological Sciences-STA, Chiba, Japan with protons of energies up to 70 MeV. The angular sensitivities of the devices are studied and compared with Monte-Carlo predictions. We also present the results obtained at the HIMAC accelerator with 500 MeV/u Fe ions and at the CERN high energy radiation reference fields. Records made during airplane flights are shown and compared with the predictions of the CARI-6 model.     

Radiation measured during ISS-Expedition 13 with different dosimeters

Radiation in low Earth orbit (LEO) is mainly composed of galactic cosmic rays (GCR), solar energetic particles and particles in SAA (South Atlantic Anomaly). The biological impact of space radiation to astronauts depends strongly on the particles’ linear energy transfer (LET) and is dominated by high LET radiation. It is important to measure the LET spectrum for the space radiation field and to investigate the influence of radiation on astronauts. At present, the preferred active dosimeters sensitive to all LET are the tissue equivalent proportional counter (TEPC) and the silicon detectors in various configurations; the preferred passive dosimeters are CR-39 plastic nuclear track detectors (PNTDs) sensitive to high LET and thermoluminescence dosimeters (TLDs) as well as optically stimulated luminescence dosimeters (OSLDs) sensitive to low LET. The TEPC, CR-39 PNTDs, TLDs and OSLDs were used to investigate the radiation field for the ISS mission Expedition 13 (ISS-12S) in LEO. LET spectra and radiation quantities (fluence, absorbed dose, dose equivalent and quality factor) were measured for the space mission with different dosimeters. This paper introduces the role of high LET radiation in radiobiology, the operational principles for the different dosimeters, the LET spectrum method using CR-39 detectors, the method to combine the results measured with TLDs/OSLDs and CR-39 PNTDs, and presents the LET spectra and the radiation quantities measured and combined.