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。     

LaBr3(Ce)元件破损在线监测关键核素确定及效率校准

常用的元件破损在线监测方法受外在因素影响较大,以γ能谱中关键裂变产物核素比活度进行在线定量分析是一种可靠的元件破损监测方法。针对新型LaBr₃(Ce)元件破损监测仪,设计了元件破损模拟实验,对逸出的裂变产物采用HPGe和LaBr₃(Ce)探测器进行了对比测量。通过不同冷却时间γ能谱的核素分析,确定了¹³⁵Xe,⁸⁸Kr,¹³⁸Xe,⁸⁸Rb,¹³⁸Cs等可作为LaBr₃(Ce)元件破损γ能谱监测的关键核素。同时,制备了覆盖能量范围(250～2 400)keV,含⁶⁰Co,¹³⁷Cs,¹³³Ba;²⁴¹Am,¹⁵²Eu;¹⁰⁹Cd,⁸⁸Y,⁵⁷Co及²⁴Na的4组放射性标准溶液,在建立的效率校准系统上,校准了LaBr₃(Ce)在线监测仪的效率。在反应堆一次异常情况分析中,已校准的LaBr₃(Ce)元件破损监测仪对关键核素的现场分析结果与HPGe的取样分析结果一致,表明效率校准结果准确,校准方法可靠。     

LaBr3(Ce)元件破损在线监测关键核素确定及效率校准

常用的元件破损在线监测方法受外在因素影响较大，以γ能谱中关键裂变产物核素比活度进行在线定量分析是一种可靠的元件破损监测方法。针对新型LaBr₃(Ce)元件破损监测仪，设计了元件破损模拟实验，对逸出的裂变产物采用HPGe和LaBr₃(Ce)探测器进行了对比测量。通过不同冷却时间γ能谱的核素分析，确定了¹³⁵Xe，⁸⁸Kr，¹³⁸Xe，⁸⁸Rb，¹³⁸Cs等可作为LaBr₃(Ce)元件破损γ能谱监测的关键核素。同时，制备了覆盖能量范围(250～2 400)keV，含⁶⁰Co，¹³⁷Cs，¹³³Ba；²⁴¹Am，¹⁵²Eu；¹⁰⁹Cd，⁸⁸Y，⁵⁷Co及²⁴Na的4组放射性标准溶液，在建立的效率校准系统上，校准了LaBr₃(Ce)在线监测仪的效率。在反应堆一次异常情况分析中，已校准的LaBr₃(Ce)元件破损监测仪对关键核素的现场分析结果与HPGe的取样分析结果一致，表明效率校准结果准确，校准方法可靠。     

单球中子能谱仪的发展概况

本文调研了国内外多家实验室的多探头单球中子能谱仪技术现状,核心探测器主要是活化片、热释光剂量计、~6Li-~7Li对玻璃闪烁体、硅二极管、位置灵敏正比计数器等。针对这几种单球中子能谱仪的结构设计、能量响应模拟、能谱实验测量等进行了讨论分析。     

空间辐射剂量测量技术发展CSCD

简要介绍了用于空间辐射剂量测量的被动式和主动式仪器,并进行了对比。被动式仪器有荧光探测器、径迹蚀刻探测器、核乳胶探测器、金属箔探测器、气泡探测器和MOSFET剂量计;主动式仪器有硅半导体探测器(Liulin-4)、硅望远镜(DOSTEL、RRMD、Liulin-5、CPDS)、气体探测器(TEPC、R-16电离室)和中子谱仪(Bonner球中子谱仪、层叠闪烁谱仪)。利用多种测量方法互相补充和验证,为空间辐射剂量提供了更可靠的数据。     

月球表面元素含量的定量分析方法

综合了月球元素定量研究在探测手段和定量方法等方面取得的最新进展。在探测手段方面,介绍了美国最近发射的克莱门汀和月球勘探者探测器使用的多谱段成像仪、中子探测仪以及γ谱仪的主要性能,在定量方法方面,讨论Fe、Ti以及稀土元素等在定量方法上的进展。     

太赫兹大气临边探测仪遥感中高层大气风仿真

太赫兹大气临边探测仪（TALIS）是中国正在预研的第一台THz频段的临边探测仪,主要用于高精度、高分辨率的大气遥感测量.TALIS的观测目标主要包括大气温度、大气压强、大气成分（例如H₂O,O₃,HCl,ClO,N₂O,HNO₃等）的垂直分布以及长期变化趋势.由于TALIS的频段覆盖了许多重要的吸收谱线,其观测数据中包含大气风的多普勒信息,因此可以用于反演中高层风的廓线.本文针对TALIS视线多普勒风的观测进行仿真,利用辐射传输模型（ARTS）评估了TALIS测风的潜力和相应的反演精度.结果表明,TALIS的118GHz谱仪具有较好的测量精度,在70km处的精度为12m·s-1.183GHz,633GHz和658GHz谱仪也有一定的测量信息,反演精度分别为19m·s-1（60km）,19m·s-1（50km）,16m·s-1（50km）.TALIS有一个候选的测风谱仪位于655GHz频段,其在55km处的反演精度为11m·s-1.此外,虽然降低谱分辨率能有效提高系统灵敏度,但并不能提高反演精度,需要通过降低系统噪声来提高测风的精度.      

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。      

基于中法海洋卫星波谱仪观测的一维海浪谱模型对比

海浪谱模型不仅能表征粗糙海表面,还能揭示海浪能量随波数和方向的分布,为海洋探测等研究和应用提供必要信息。中法海洋卫星搭载的波谱仪可实现全球海浪方向谱的空间观测。根据现有海浪谱模型和海浪谱观测的发展现状,对波谱仪观测的海浪参数进行统计特征分析,在波谱仪观测的波数范围内(0.01～0.25rad·m^–1),进行不同海态下实测海浪谱与以Apel谱、Elfouhaily谱和Goda谱为代表的波高谱和曲率谱模型的比较,得到现有海浪谱观测与上述三种谱模型的差异,并结合海浪参数统计特征,对产生差异的原因进行讨论分析。结果表明,现有谱与波谱仪观测的差异来自于其对海态的不完全表达,且所表示的海态在自然状态中仅占有限比例。研究结论可以为海浪谱模型和观测的后续研究提供支持。     

（20～400）MeV准单能中子参考辐射场的建立方法CSCD

为了满足对高能中子辐射场测量仪器进行校准的需要,必需建立20MeV以上的准单能中子参考辐射场.对国际上（20～400） MeV准单能中子参考辐射场的建立情况及建立方法进行了调研,可通过7Li（p,n）7Be反应获得该能区准单能中子场,中子束流轮廓可通过转换体和影像板进行测量,辐射场中子能谱可利用液体闪烁探测器或者238U裂变电离室通过飞行时间法进行测量,可建立高效率的反冲质子望远镜作为该能区的中子注量测量初级标准.     

Presolar grains in micro-inclusions of iron meteorites

In residues of several iron meteorites, obtained by dissolution of the metal in dilute H₂SO₄, the isotopic ratio of ¹⁹⁰Os/¹⁸⁴Os has been measured by radiochemical neutron activation analysis and is found to be anomalous in several cases. The largest deviation so far seen is a 40% enrichment of ¹⁸⁴Os in a mineral of Sikhote Alin. A lack of homogenization of the two isotopes that are produced in different nucleosynthetic processes suggests that iron meteorites are more primitive than any other matter available to us so far. Isotopic composition of Xe is found to be planetary in general. However the two light isotopes ¹²⁴Xe and ¹²⁶Xe are strongly depleted in some non-magnetic residues. Correlation diagrams of isotopic ratio pairs indicate that a two component mixture model is not adequate. EPR studies of the non-magnetic fractions of the residues show a large concentration of stabilized free radicals which could be ascribed to an irradiation of micro-inclusions prior to compaction into the metal matrix.     

^(137)Cs,^(60)Co大面积航空平面源的制备技术CSCD

用于校准航空γ谱仪的137Cs,60Co大面积航空平面源对传统的涂刷制源技术提出了挑战,为确保平面上的均匀性,借鉴现代网格点阵喷涂技术,将137Cs,60Co两种放射性标准溶液分别定量滴注在底衬滤纸上,晾干后热塑封并用环氧树脂将塑封片固定在梯形铝板上,由8块梯形铝板拼接为边长1m的正六边形航空平面源。制备的航空平面源的扩展不确定度(k=2)为4%,不均匀性优于10%。     

ROSAT PSPC observations of two starburst galaxies

We present results from ROSAT observations of NGC 1808 and NGC 2903. Exposures of 10 ksec each with the PSPC detector show X-ray sources at the central positions of both galaxies which are classified as nuclear starburst galaxies. Both targets, NGC 1808 and NGC 2903 appear slightly extended in X-ray maps in the energy band 0.1–2.4 keV. The X-ray spectrum of NGC 1808 shows almost complete absorption below 0.5 keV, indicating an extremely high hydrogen column density towards that source (N_H ≈ 8 × 10²¹cm⁻² resulting from model fits on the PSPC spectrum). In case of NGC 2903, the number of counts in the ROSAT band is significantly lower than expected from a previous EINSTEIN investigation of the source.     

Interplanetary scintillations of PKS 2314+03 during occultation by comet Halley

Strong interplanetary scintillations (IPS) of the quasar 2314+03 were recorded at 103 MHz at Thaltej-Ahmedabad, India with a transit type correlation interferometer on 18, 19 and 20 December 1985, as the radio source was predicted to be occulted by the ion tail of the comet Halley.

On 18th through 20th very strong scintillations, with periodicities of 1 sec average were observed, their amplitude progressively decreasing as the source approached the tail-end. The rms variations of scintillating flux of the source on 18, 19 & 20 were about 18, 11 & 4.7 Jy, as against 3.3 Jy on control days 17 and 21 December for solar elongation of 87°.

Assuming Gaussian irregularities with weak scattering, the rms density variations, ΔN, of 10, 6, 3 and 1 elec./cm³ on 18 through 21 December, from the comet nucleus towards its tail-end, varied as (ΔN) ∝ r^−3.3 as against (ΔN) ∝ r⁻² in the solar plasma.

Quasi-periodic modulations of the enhanced scintillating flux possibly imply 10⁴ km scale-size ion condensations and mean electron density of 10³ to 10⁴ electrons/cm³ in the Halley's plasma tail.     

The luminosity dependence of the phase-averaged X-ray spectrum of the transient 42 second pulsar EXO 2030+375

We report on the evolution in the X-ray spectrum of the transient X-ray pulsar EXO 2030+375 during part of an outburst in 1985 May–August. The overall continuum spectral shape is similar to that of other accreting pulsars and can be represented by a power-law spectrum modified at low energies by significant absorption and at high-energies either by an exponential cut-off or by the effects of cyclotron scattering. As the luminosity decreased by a factor 100, the X-ray spectrum became harder with the photon index decreasing from 1.83 ± 0.01 to 1.29 ± 0.01. In addition, the high-energy cutoff decreased from 20 to 10 keV during the same interval. If the cutoff is interpreted in terms of cyclotron resonance scattering, then this implies a magnetic field strength that decreased from 2.6 × 10¹² G to 1.3 × 10¹² G. This variation implies that the cutoff energy does not provide a reliable measure of the surface magnetic field strength in this system.     

Diurnal variations of ion flux intensity on a synchronous orbit

The data from the synchronous-orbit satellites of the Gorizont series are used to study the dependences of the ion flux variation amplitudes in the synchronous altitude region (the diurnal behaviour) on particle energies and on the form and rigidity of the particle energy spectrum. The proton fluxes were measured in the energy range E 60–120 keV, and the [N,0]²⁺ and [C,N,0]⁴⁺ ion fluxes in the energy range E 60–70 keV/e.

The ratio of the diurnal variation amplitudes of the studied ions is shown to correspond to the similarity of their energy spectra in the E/Q representation. The magnetically-quiet time gradient of the distribution function F(μ,J,L) in the synchronous-orbit region is shown to be (∂F/∂L)=0 for the H⁺ and [N,0]²⁺ ions and (∂F/∂L) > 0 for the [C,N,0]⁴⁺ ions (at the values of μ corresponding to the examined energy ranges). During magnetically-disturbed periods the inner boundary of the (∂F/∂L)=0 region shifts to lower L and (∂ F/∂L) = O in the synchronous altitude region must be also for the [C,N,O]⁴⁺ ions.     

Study of the luminosity-dependent cyclotron resonance energies of the binary X-ray pulsar 4U 0115+63 with RXTE

We report on the luminosity dependent change of the cyclotron resonance energy obtained from a transient X-ray pulsar, 4U 0115+63. Using RXTE data observed on 1999 March, we found that the fundamental resonance energy stayed constant (11 keV) when the source luminosity was above 5 × 10³⁷ erg s⁻¹. As the luminosity decreased below 5 × 10³⁷ erg s⁻¹, the fundamental resonance energy gradually increased up to 16 keV at 0.16 × 10³⁷ erg s⁻¹. The luminosity dependence of the resonance energy can be understood by the change of the accretion column height.     

Microwave imaging observation of an electron stream in a solar flare

We report a Nobeyama Radioheliograph (NoRH) microwave observation of a propagating feature of non thermal emission in a solar flare. The flare had a very extended source well resolved by NoRH. In the rising phase of the microwave burst, a non-thermal gyrosynchrotron source was observed by the high-rate (10 images per second) observations to propagate from one end of the loop to the other with a speed of 9 × 10⁴ km s⁻¹. We interpret this non-thermal propagating source is emitted from streaming electrons.