小尺度参考辐射场中散射γ能谱的计量特征提取方法

在小尺度参考辐射（MRR）场γ射线空气比释动能约定真值（CAK）的确定方法中,散射γ能谱由于受放射性统计涨落与测量时电子学噪声的干扰及存在的数据冗余问题而不能准确地表征MRR的特征信息,影响了CAK预测模型的构建效率与预测精度。本文采用了小波分析与主元分析（PCA）方法依次对散射γ能谱进行降噪处理和计量特征提取。所提取的计量特征用于替代原始能谱数据并构建了CAK的预测模型,其构建效率与预测精度均得到明显提高。     

A unit for inspection of materials using differential gamma-ray scattering technique

The main objectives of this research were to develop a prototype unit using the differential gamma-ray scattering technique (DGST) and to demonstrate its possible use in nondestructive inspection of materials. The unit consisted of a 5 mCi (185 MBq) ¹³⁷Cs gamma-ray source positioned perpendicularly to a 5 cm × 5 cm BGO detector. The gamma-ray beam was collimated by a 5 cm thick lead collimator with 1 cm ∅ opening while the detector was only side shielded allowing scattered gamma-rays to reach the detector from different angles. The unit was then tested with 20 cm × 20 cm × 20 cm concrete mortar containing four rebars at its corners. It was found that the integral of the differential spectrum changed corresponding to the size and position of the rebar which was in front of the source and the detector. It was also found that the integral of the differential spectrum increased with increasing degree of corrosion of the rebar. The results indicated that a portable DGST unit could be designed to be used as a tool in nondestructive inspection but the interpretation of the differential spectrum still needs further investigation.     

A digital spectrometer approach to obtaining multiple time-resolved gamma-ray spectra for pulsed spectroscopy

Neutron-induced gamma-ray emission and its detection using a pulsed neutron generator system is an established analytical technique for quantitative multi-element analysis. Traditional gamma-ray spectrometers used for this type of analysis are normally operated either in coincidence mode - for counting prompt gamma-rays following inelastic neutron scattering (INS) events when the neutron generator is ON, or in anti-coincidence mode - for counting prompt gamma-rays from thermal neutron capture (TNC) processes when the neutron generator is OFF. We have developed a digital gamma-ray spectrometer for concurrently measuring both the INS and TNC gamma-rays using a 14 MeV pulsed neutron generator. The spectrometer separates the gamma-ray counts into two independent spectra together with two separate sets of counting statistics based on the external gate level. Because the TNC gamma-ray yields are time dependent, additional accuracy in analyzing the data can be obtained by acquiring multiple time-resolved gamma-ray spectra at finer time intervals than simply ON or OFF. For that purpose we are developing a multi-gating system that will allow gamma-ray spectra to be acquired concurrently in real time with up to 16 time slots. The conceptual system design is presented, especially focusing on considerations for tracking counting statistics in multiple time slots and on the placement of pulse heights into multiple spectra in real time.     

Energy response correction for an electronic personal dosimeter using the channel ratio method

An electronic personal dosimeter mainly uses a Si-PIN photodiode as X-and gamma-ray detectors.The photon energy response of this instrument is inconsistent in the case of no correction,which seriously affects the accurate monitoring of personal dose equivalent H_p(10)parameters for radiation workers.For this reason,in this paper we propose a method of combining composite screen detection technology,multichannel measurement technology,and the channel ratio method to achieve accurate measurement of the personal dose equivalent parameters.According to China National Standard GB/T 13161-2003 and National Verification Regulation JJG 1009-2006,the instrument was tested in the energy range between 48 keV and 1.25 MeV.The experimental results showed that the difference of energy response to ~(137)C_S corrected by the new method was almost constant within ±6.0%,which fulfilled the ±30% requirement of GB/T 13161-2003 and JJG1009-2006.Meanwhile,the method proposed obtained energy information regarding the radiation field.     

可作为校准检定用标准剂量计的能量补偿型高气压电离室改进

在电离辐射计量检定工作中,标准剂量计的测量结果通过检定逐级传递到工作计量器具,以实现单位统一和量值准确可靠。由于环境水平γ射线剂量率较低,国际上常用的PTW-UNIDOS系列标准剂量计无法满足需要。针对这一特点,结合蒙特卡罗方法对高气压电离室的X射线、γ射线和宇宙射线响应特性进行模拟计算,进行了能量补偿型高气压电离室改进。测试结果表明:剂量率约30 μGy/h时,能量补偿型高气压电离室在87 keV～1.25 MeV能量范围内相对于¹³⁷Cs γ射线的响应偏差不大于6%,宇宙射线和¹³⁷Cs γ射线的响应偏差不大于10%,在0.5 μGy/h～1 mGy/h范围内相对固有误差为-3%,0.5 μGy/h时的重复性为0.7%,校准因子的不确定度为4%(k=2),可作为环境水平标准剂量计在校准检定工作中使用。     

Development of a direction finding gamma-ray detector

This paper describes a direction finding gamma-ray detector, which consists of three different scintillators; NaI (Tl), CsI (Tl) and BGO. The detector positively increases directional sensitivity to incident gamma-rays, and can measure direction, energy and number of gamma-rays. This detector will be useful to carry out monitoring of nuclear power plants or radiation facilities in emergencies. It will be also effective in searching for radiation sources such as radioisotopes and radioactive contaminations. Experimental results have shown the proposed directional detector has a potential for practical use in real fields and will contribute to radiation emergency preparedness.     

Dose intercomparison studies for 60Co gamma-ray and electron beam irradiation in the year 2002

1 Introduction With the rapid development of radiation process- ing by electron beam irradiation in China, it is more Ever since 1962, alanine/EPR dosimetry system and more needed to establish a transfer dosimetryhas been used to measure the absorbed dose.[1] Its ad- system with high accuracy to assure the quality of thevantages over othe…     

Diffusion characteristics of HTO and 99TcO4- in compacted Gaomiaozi (GMZ) bentonite

The characteristics of diffusion are essential to the transport of radionuclides through buffer/backfill materials, such as bentonite, which are commonly found in waste repositories. This study used through-diffusion techniques to investigate the diffusion behavior of HTO and ~(99)TcO_4~- on GMZ bentonite of various densities. Diffusion rates were calculated by measuring the diffusion coefficients(De, Da), plotting breakthrough curves and interpreting experiment data. The apparent and effective diffusion coefficients of HTO ranged from(1.68 ± 0.40) 9 × 10~(-11) to(2.80 ± 0.62) 9 × 10~(-11) m~2/s and from(4.61 ±1.28) 9 × 10~(-12) to (16.2 ± 2.50) 9 × 10~(-12) m~2/s, respectively.The apparent and effective diffusion coefficients of~(99)TcO_4~-ranged from(5.26 ± 0.16) 9 × 10~-12to(7.78 ± 0.43) 9× 10~-12m~2/s and from(1.49 ± 0.002) 9 × 10~(-12) to(4.16 ±0.07) 9 × 10~(-12) m~2/s, respectively. The distribution coefficients of HTO and~(99)TcO_4~-ranged from(0.70 ± 0.12) 9× 10~(-2) to(1.36 ± 0.53) 9 × 10~(-2) mL/g and from(1.12 ±0.06) 9 × 10~(-2) to(5.79 ± 2.22) 9 × 10~(-2) mL/g, respectively.The Deand Kdvalues were shown to decrease with an increase in the bulk dry density of compacted bentonite. Our results show that HTO and ~(99)Tc could be considered nonsorbent radionuclides. The data obtained in this studyprovide a valuable reference for the safety assessment of waste repositories.     

伴随粒子法瞬发γ能谱测量技术研究

采用伴随α粒子符合方法测量了水、石墨、液氮样品的16O、12C、14N核素以及硝铵、三聚氰胺、尿素和模拟样品的D-T中子作用的非弹瞬发γ谱,利用反卷积对化合物的脉冲幅度谱进行了解谱,实验获得的元素份额与其化学成分比在10%内相符。     

基于ISO 4037-1：2019对60~250 kV窄谱系列X射线参考辐射质的研建

以ISO 4037 1：2019为依托,使用大体积自由空气电离室作为测量器具,采用半值层法建立60~250 kV窄谱系列X射线参考辐射质,实验得出的各辐射质的第1半值层和第2半值层的值均在标准规定的误差范围内。使用高纯锗谱仪对建立的X射线参考辐射质进行测量,得到不同辐射质下的脉冲幅度谱。数据处理和分析结果表明,建立的60~250 kV窄谱系列X射线参考辐射质的谱分辨率、平均光子能量和有效能量与ISO 4037 1：2019的推荐值有较好的一致性。本次实验建立的60~250 kV窄谱系列X射线参考辐射质满足ISO 4037 1：2019要求。     

小型数控式相对湿度控制装置研制

相对湿度(Relative humidity,RH)是很多实验过程的关键环境参数之一,RH控制对同步辐射在线实验尤为重要。基于单片机的动态控制,研制了一套便于加载至同步辐射实验线站在线使用的小型数控式RH控制装置。该装置使用微型气泵抽取潮湿空气和干燥空气分别构建了加湿和除湿两个通道对控湿腔体内RH进行动态平衡。采用模糊控制算法通过单片机实时控制RH的变化。该装置能将RH控制在20%-94%,误差为±1.0%;能以固定速度控制RH稳定上升(20%-90%)或稳定下降(90%-20%),误差为±1.5%;能在湿度上升、稳定和下降三个工作模式之间快速切换,可满足同步辐射在线实验对湿度控制的多种需求。     

Study on Energy Variable Laser-Compton Gamma-ray with a Fixed Energy Electron Beam

The electron beam in medium scale (1-2 GeV) synchrotron radiation ring is attractive to generate an intense and narrow energy spread of laser-Compton gamma-ray beam in an MeV-region. Since the storage ring is operated with fixed electron energy for synchrotron radiation (SR) users, methods for changing the gamma-ray energy should be investigated. Three methods, 1) using a tunable laser, 2) changing the collision angle between the laser and the electron beam, and 3) selecting the scattering angle of the laser-Compton gamma-ray by using a collimator and an absorber, are studied by analytical calculation and simulation which takes into account the electron beam size and effective length of laser-electron interaction. Since a tunable laser has no enough power in the infrared wavelength region, an intense gamma-ray beam can not be generated by using a tunable laser at present stage. The collimator-absorber method generates enough amounts of gamma-rays, but simulation shows a broad energy spread, -7%, of the gamma-ray. An acceptable gamma-ray beam can be obtained by changing the incident angle of the laser beam whose pulse width and timing are synchronized with the electron beam pulse.     

Study on element detection and its correction in iron ore concentrate based on a prompt gamma-neutron activation analysis system

A prompt gamma-neutron activation analysis(PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlorine in the neutron field, the linear relationship between the iron analytical coefficient and total iron content was poor, increasing the error in the quantitative analysis. To solve this problem, gamma-ray self-absorption compensation and a neutron field correction algorithm were proposed, and the experimental results have been corrected using this algorithm. The results show that the linear relationship between the iron analytical coefficient and total iron content was considerably improved after the correction. The linear correlation coefficients reached 0.99 or more.     

Pulse Shape Analysis on Mixed Beta Particle and Gamma-ray Source Measured by CdZnTe Semiconductor Detector by means of Digital-Analog Hybrid Signal Processing Method

We present a study on pulse shapes of a CdZnTe semiconductor detector for beta particles and gamma-rays emitted by a ¹³⁷Cs-⁹⁰Sr mixed source. When beta and gamma radiations enter a semiconductor detector, two kinds of pulses are produced according to the type of radiations. The characteristics of the pulses are determined by their energy and depth of interaction. The energy deposited on the detector basically determines the pulse height and the depth of interaction affects the pulse shape. Because of the different characteristics of beta and gamma radiations, their pulse shapes are also different. The digital-analog hybrid signal processing method was applied to separation of the beta spectrum from the beta-gamma mixed one. The separation of beta spectrum was done based on a neural network algorithm, a leading edge area method, and a falling continuum tail value method. However, the perfect separation could not be obtained. The separation was also done by reconstructing the spectra on the basis of subtraction of gamma-ray component. The spectra of beta particles and gamma-rays from ¹³⁷Cs-⁹⁰Sr mixed source could be separated well by using the reconstruction method.     

Angular Distribution of Argon Ions and X-Ray Emissions in the Apf Plasma Focus Device

Angular distribution of ion beam emission from an argon gas-filled plasma focus devices has been investigated using an array of five Faraday cups. The argon ion beam emission is found to be highly pressure-dependent and reaches its maximum at the pressure of 1 torr. The ions flux decreased as the working pressure increased; the maximum ion density at 1 torr was estimated to be around 9.24 × 10²⁴ ions/steradian. Also, the study on the angular distribution of X-rays has been carried out using TLD-100 dosimeters. The intensity of ions reduced significantly at angles higher than ±11° but the X-ray distribution was bimodal, peaked approximately at ±15°.     

氧化钚属性测量技术研究

利用高分辨高纯锗γ谱仪,在铅屏蔽室内,对100 g回收氧化钚粉末样品和8 g纯氧化钚粉末样品分别进行了长时间测量,在自然环境,对200 g回收氧化钚粉末样品进行了现场探测.在三个样品的能谱中均观察到871 keV特征γ射线,除此之外,没有观察到其它与氧的存在相关的特征射线.同过去所测的金属钚谱相比较,在金属钚谱中未曾发现871 keV特征γ射线.因此,就核查区分封闭容器罐中的钚材料是金属钚还是化合钚而言,可以用871 keV来旁证"金属钚的不存在".对200 g氧化钚样品的现场探测表明,871 keV能峰是明显存在的,而且自编的丰度和年龄分析软件能从10 min测量能谱中识别出871 keV能峰.如果将属性测量系统的分析软件和控制部分进行适当改进,该系统就具备通过监测871 keV能峰确定氧化钚属性的能力.     

同位素铯源小尺度参考辐射蒙特卡罗模拟研究

为研究同位素铯源小尺度参考辐射的计量特性与散射特征,采用蒙特卡罗程序MCNP开展了模拟研究,并将模拟结果与实验结果进行对比。本文厘清了边长为600mm的铅屏蔽立方体同位素铯源小尺度参考辐射的计量特性与空间散射射线的特征信息,明确了待检仪器探头尺寸对小尺度参考辐射中散射成分的影响规律,确定了用于表征散射特征的计量特征点的位置。     

Dose profile monitoring with carbon ions by means of prompt-gamma measurements

A key point in the quality control of ion therapy is real-time monitoring and imaging of the dose delivered to the patient. Among the possible signals that can be used to make such a monitoring, prompt gamma-rays issued from nuclear fragmentation are possible candidates, provided the correlation between the emission profile and the primary beam range can be established. By means of simultaneous energy and time-of-flight discrimination, we could measure the longitudinal profile of the prompt gamma-rays emitted by 73 MeV/u carbon ions stopping inside a PMMA target. This technique allowed us to minimize the shielding against neutrons and scattered gamma rays, and to find a good correlation between the prompt-gamma profile and the ion range. This profile was studied as a function of the observation angle. By extrapolating our results to higher energies and realistic detection efficiencies, we showed that prompt gamma-ray measurements make it feasible to control in real time the longitudinal dose during ion therapy treatments.     

基于车载移动的区域射频电磁辐射监测方法比较研究

本文以江苏省南通市为例,分别采用车载移动法和国标法对城区射频电磁环境进行现场实测,共获取有效测试数据20 250个,其中移动法20 060个,国标法190个。比较分析结果表明:(1)两种方法单点比对监测结果相对偏差小于±10%;(2)两种方法所监测的南通城区环境射频电磁辐射平均综合电场强度分别为(0.58±0.28)V/m和(0.52±0.32)V/m,无明显差别,但在典型性和代表性表征上车载移动法明显优于国标法;(3)研究发现港闸区域50 Hz极低频高压输电线路沿路密集架设是车载移动法测值偏高的主要原因,可通过优化行驶路线避开高压线和后期数据处理等方法消除此类影响。本研究结果将有助于推动车载移动法国家监测技术规范的出台,并为在全国范围内推广应用提供了示范借鉴。     

主动式电离辐射剂量仪的脉冲X射线响应特性研究

国际上对于辐射防护剂量学的研究主要针对连续辐射,然而脉冲式电离辐射在工业探伤、X射线诊断、闪光X射线照相技术、安检和科研等领域中得到了广泛应用。主动式电离辐射剂量仪采用稳态辐射场进行刻度,难以准确测量短脉冲、高剂量率的脉冲式电离辐射。为了解主动式电离辐射剂量仪的脉冲响应特性,基于毫秒级脉冲X射线机搭建脉冲X射线参考辐射场,针对常用4款主动式剂量仪开展脉冲X射线响应特性测试。测试结果表明,目前常用4款主动式剂量仪均不适用于短脉冲、高剂量率辐射场的剂量测量和预警。