^18O离子轰击厚靶的中子剂量学参数

用阈探测器活化法测量了每个核子动能（简称单核能）为５０ＭｅＶ＾１８Ｏ离子轰击厚靶（Ｂｅ、Ｃｕ、Ａｕ）时出射中子的能量分布、注量率分布和中子角分布，得到了＾１８Ｏ离子的中子产额、前向中子发射率和中子剂量当量率分布的数据。并与国外报道的单核能在２０ＭｅＶ以下的低能重离子轰击厚靶研究中得到的中子剂量学参数进行了比较和分析。     

用阈探测器活化法测量50MeV／u重离子实验靶区的中子注量率,…

用阈探测器中子活化法测定了５０ＭｅＶ／ｕ＾１２Ｃ离子实验靶区的次级中子平均注量率、角分布、粗略能谱，并估算了重离子反应的中子产额。     

一种新型中子周围剂量当量(率)测量装置的性能实验

本文介绍一种新型中子周围剂量当量（率）监测方法,搭接了一套单球多计数器的中子周围剂量当量（率）监测装置,利用蒙特卡罗MCNP4A程序模拟计算了中子注量的响应函数,借用“少道”解谱软件进行解谱并对一些辐射防护量进行了计算.通过对^252Cf和Am-Be两种中子参考辐射场的测试,表明对中子注量率、周围剂量当量率、单位注量平均周围剂量当量和剂量当量平均能量的计算结果与参考值相比,偏差均小于10%, 这种监测方法较好地解决了中子剂量仪表的能量响应问题.     

一种新阈探测器的实验验证和重离子靶区中子测量

验证了用^2099Bi作为一种新的阈探测器测量高能中子的可能性，并利用^115In,^27Al,^19F,^12C和^209Bi组成的阈探测器组合测量了中能重离子反应实验靶区出射中子的注量率分布、能量分布和剂量当量率分布。     

西藏地区天然中子能谱测量

本文采用多球中子谱仪和中子周围剂量当量（率）仪分别对西藏地区的天然中子能谱和周围剂量当量率进行了测量,得到了西藏地区不同海拔处的室外天然中子能谱和周围剂量当量率。研究结果表明：该地区室外天然中子的能谱形状基本保持不变,其各能区的中子注量率随海拔的增加而增大,天然中子的总注量率和有效剂量率及周围剂量当量率均随海拔的增加呈指数规律增大;此外,天然中子的有效剂量率可用中子周围剂量当量（率）仪的测量结果乘以能谱 有效剂量转换因子得到。     

300^#—1靶片内热中子注量率分布测量实验研究

介绍了以φ4mm×0.005mm的金箔为探测片,采用绝对与相对测量法测量300#-1靶片内部热中子注量率分布的原理和方法.给出了靶片所在堆芯位置的绝对中子注量率和靶片内相对中子注量率分布.为靶片自屏因子的确定提供了测量数据.     

44GeV或18GeV ^12C离子轰击Cu靶或Pb靶时中子产额的研究

用ＣＲ－３９迭层探测器测量了４４ＧｅＶ或１８ＧｅＶ１２Ｃ离子轰击Ｃｕ靶或Ｐｂ靶时中子产额与入射粒子能量以及靶核质量的关系。当入射能量由１８ＧｅＶ增至４４ＧｅＶ时，Ｃｕ靶的中子产额增大２．１２±０．１９倍，Ｐｂ靶的中子产额增大２．０４±０．１５倍。Ｐｂ靶和Ｃｕ靶中子产额之比在４４ＧｅＶ和１８ＧｅＶ分别为２．５４±０．２０和２．５６±０．２０。     

300~#-1靶片内热中子注量率分布测量实验研究

介绍了以4 mm× 0 .0 0 5mm的金箔为探测片 ,采用绝对与相对测量法测量 30 0 #- 1靶片内部热中子注量率分布的原理和方法。给出了靶片所在堆芯位置的绝对中子注量率和靶片内相对中子注量率分布。为靶片自屏因子的确定提供了测量数据。     

靶件内中子注量率分布计算方法研究

选择ANISN作为实验靶件内中子注量率分布计算的程序，编制辅助程序输入混合材料截面。计算得到延时水箱附近的中子注量率，与测量数据作对比。计算得到靶片自屏因子，并与2000年实验数据对比。确认计算方法可行后，计算得到实验靶件内热中子注量率分布数据。     

~(241)Am-Be源和~(226)Ra-Be源的中子注量-剂量换算系数

在中子剂量仪表刻度和中子剂量计算中经常遇到单位注量中子与比释动能、吸收剂量、剂量当量之间的换算关系。它们之间的数值关系通常称为中子注量-剂量换算系数。在《放射防护规定》中规定职业放射性工作人员最大容许剂量当量为每年5雷姆。同时又对2.5毫雷姆/小时对应的中子通量(中子/厘米~2·秒)进行了规定(见附表1第7栏)。国际辐射防     

Neutron dose equivalent rate for heavy ion bombardment

The fluence rate distribution of neutrons in the reactionsof 50MeV/u ^18O-ion on thick Be,Cu and Au targets have been measured with an activation method of threshold detectors andthe neutron dose equivalent rate distributions at 1m from the tqrgets in intermediate energy heavy ion target area are obtained by using the conversion factors from neutron fluence rate to neutron doseequivalent rate.     

Neutron distribution and yield produced by 50MeV／u ^18O—ion on thick targets

Neutron energy,fluence rate,angular distributions and dose equivalent rate distributions around the thick Be,Cu,Au targets bombarded by 50MeV/u ^18O-ion were measured using a threshold detector activation method.At the same time,the neutron yields of ^18O-ion and the neutron emission rates in the forward direction were obtained approximately.     

Neutrons produced by 75MeV／u ^12C—ion on thick targets

Fluence rates and angular distributions of the neutron emitted by 75MeV/u ^12C-ion bombardment on thick Be and Au targets have been measured by means of the threshold detector activation method.Based on that,the neutron yields,emission rates in the forward direction and neutron dose equivalent rate distributions were deduced.     

Experimental test of a new neutron threshold detector and its application

The Possibility of using 209Bi as a new threshold detector to measure high-energy neutrons was investigated for the first time.At the same time the experiment measured successfully the emitted neutron fluence rate,energy spectrum and dose equivalent rate distributions in the heavy ion target area using a detector complex including 209Bi,^115In,^27Al,^19Fand ^12C samples.     

Synthesis and Characterization of a Soft-tissue Substitute for Neutron Dosimetry

To develop a physical phantom for neutron dosimetry, a solid soft-tissue substitute was synthesized. The synthesized tissue substitute, NAN-JAERI, is improved in both hydrogen and oxygen elemental composition in comparison with existing tissue substitutes. To examine the radiation characteristics of the new soft-tissue substitute, absorbed dose distributions in NAN-JAERI were measured using a ²⁵²Cf neutron source. The measured absorbed dose distributions of neutrons and photons agree with those calculated by a Monte Carlo simulation code MCNP. The agreement between the experiment and the simulation verifies this method of evaluating the soft-tissue equivalence of NAN-JAERI for ²⁵²Cf neutrons. Similar simulations for some mono-energetic neutron sources showed that the newly developed tissue substitute has soft-tissue equivalent characteristics in the neutron energy range from 1 MeV up to 14 MeV, in terms of the absorbed dose distributions in a slab phantom.     

Energy spectrum measurement and dose rate estimation of natural neutrons in Tibet region

In this work, natural neutron spectra at nine sites in Tibet region were measured using a multi-sphere neutron spectrometer. The altitude-dependence of the spectra total fluence rate and ambient dose equivalent rate were analyzed. From the normalized natural neutron spectra at different altitudes, the spectrum fractions for neutrons of greater than 0.1 MeV do not differ obviously, while those of the thermal neutrons differ greatly from each other. The total fluence rate, effective dose rate and the ambient dose equivalent rate varied with the altitude according to an exponential law.     

Fluence and dose measurements for an accelerator neutron beam

The 3 MV Van de Graaff accelerator at McMaster University accelerator laboratory is extended to a neutron irradiation facility for low-dose bystander effects research. A long counter and an Anderson-Braun type neutron monitor have been used as monitors for the determination of the total fluence. Activation foils were used to determine the thermal neutron fluence rate (around 10⁶ neutrons s⁻¹). Meanwhile, the interactions of neutrons with the monitors have been simulated using a Monte Carlo N Particle (MCNP) code. Bystander effects, i.e. damage occurring in cells that were not traversed by radiation but were in the same radiation environment, have been well observed following both alpha and gamma irradiation of many cell lines. Since neutron radiation involves mixed field (including gamma and neutron radiations), we need to differentiate the doses for the bystander effects from the two radiations. A tissue equivalent proportional counter (TEPC) filled with propane based tissue equivalent gas simulating a 2 μm diameter tissue sphere has been investigated to estimate the neutron and gamma absorbed doses. A photon dose contamination of the neutron beam is less than 3%. The axial dose distribution follows the inverse square law and lateral and vertical dose distributions are relatively uniform over the irradiation area required by the biological study.     

医院中子照射器分析室剂量场研究

医院中子照射器建成后,对分析室内及其屏蔽门外的γ剂量率和中子剂量当量率进行了测量,测量结果显示：分析室内局部γ剂量率与设计值相差较大,分析室屏蔽门外γ剂量率超过原设计监督区限值7.5 μSv/h,因此需对分析室内部及其屏蔽门进行屏蔽改造。根据蒙特卡罗程序模拟计算结果及实际使用情况给出最终屏蔽方案,即在分析室束流孔道所在墙面加装厚度为16 cm的铅屏蔽材料屏蔽γ射线,对四周墙面及屏蔽门内侧加装厚度为1 cm的含锂聚乙烯板屏蔽散射中子。改造后分析室剂量最高点γ剂量率下降277倍,中子剂量当量率下降5.8倍,屏蔽门外γ剂量率下降近90倍。     

固定式中子剂量仪器现场标校方法研究

本文利用小型可控中子源和中子剂量参考仪器组成的核设施现场标校系统,通过空间位置对称条件下的待校准仪器与参考仪器对中子管出射中子响应之比,得到校准系数;为了完成仪器的周围剂量当量校准系数从国家标准计量检定中心参考辐射场到核设施现场的传递,必须对其进行能量修正。通过Am-Be中子源模拟核设施内部辐射场,在其中进行中子剂量仪器现场标校实验,并与校准过的多球中子谱仪测量结果相比较。结果表明:使用未经修正的校准系数对待校准仪器的测量结果进行校准,周围剂量当量率相对偏差为17.0%;使用修正后的校准系数对待校准仪器的测量结果进行校准,周围剂量当量率相对偏差为-2.4%。