Electron irradiation effects of radiochromic PCDA vesicle gel dosimeters

The gel dosimeter has the uniquely capacity in recording radiation dose distribution in three dimensions(3D), which has the specific advantages in dosimetry measurements where steep dose gradients exist. In this study, a novel radiochromic gel dosimeter was developed by dispersing nanovesicles self-assembled by 10,12-pentacosadiynoic acid(PCDA) into the tissue equivalence gel matrix. The characteristics of radiochromic PCDA vesicle gel dosimeters were evaluated. Results indicate that these radiochromic gel dosimeters have good linear response to 1.7 Me V electron beam irradiation in the dose range of 0.32–6.36 k Gy. In addition,the radiochromic gel dosimeters overcome the limitations of the existing gel dosimeters such as diffusion effect,post-radiation effect, and poor forming ability. Hence, the radiochromic PCDA vesicle gel dosimeters developed could be generally applied to 3D dose distribution measurement with optical readout.     

ALANINE/ESR DOSIMETRY FOR MEASUREMENT OF ELECTRON DOSES IN INDUSTRIAL APPLICATIONS

In this report, the results of preliminary research on L-alanine/ESR electron dosimeters are described. They include the designs of modelling tools and experimental capsules, the preparation and irradiation of very thin dosimeters, the measurement of ESR signal spectrum and the calibration method. The physical, chemical and dosimetric properties of the alanine free radical dosimeters, such as the smallest thickness, average density, lowest detectable limit, repeatability of the method, reproducibility resulted in directivity and location in resonance cavity, linearity regions as well as relative scattering of the response to identical doses, are summarized.     

Electromagnetic field effects on nucleon transverse momentum for heavy ion collisions around 100 A MeV

Effective atomic numbers for photon energy absorption(ZPEA_(eff)) and their corresponding electron numbers (NPEA_(eff)), and effective macroscopic removal cross sections of fast neutrons(RR) were calculated for 27 different types of three-dimensional dosimeters, four types of phantom materials, and water. The values of ZPEA_(eff) and NPEA_(eff) were obtained using the direct method for energies ranging from 10 keV to 20 MeV. Results are presented relative to water, for direct comparison over the range of examined energies. The effect of monomers that are used in polymer gel dosimeters on the water equivalence is discussed. The relation between Σ_R and hydrogen content was studied. Micelle gel dosimeters are highly promising because our results demonstrate perfect matching between the effective atomic number, electron density number, and fast neutron attenuation coefficient of water.     

IMPROVEMENT IN PREPARATION OF LiF TLD AND OPTIMIZATION OF MEASUREMENT PARAMETERS

The technological process for preparation of LiF TLD is reported.Sixteen types of TLD of LiF:Mg,Ti and LiF:Mg,Cu,P series are produced for dosimetry of X,γ radiations and in neutron-γ mixed radiation field.The measurement parameters have been optimizationally selected by factors of parameter evaluation(P) and orthogonal method,and the procedure of quality control is recommended.     

A new digital Gaussian pulse shaping algorithm based on bilinear transformation

Nuclear pulse signal needs to be transformed to a suitable pulse shape to remove noise and improve energy resolution of a nuclear spectrometry system. In this paper, a new digital Gaussian shaping method is proposed.According to Sallen-Key analog Gaussian shaping filter circuits, the system function of Sallen-Key analog Gaussian shaping filter is deduced on the basis of Kirchhoff laws. The system function of the digital Gaussian shaping filter based on bilinear transformation is deduced too. The expression of unit impulse response of the digital Gaussian shaping filter is obtained by inverse z-transform. The response of digital Gaussian shaping filter is deduced from convolution sum of the unit impulse response and the digital nuclear pulse signal. The simulation and experimental results show that the digital nuclear pulse has been transformed to a pulse with a pseudo-Gaussian, which confirms the feasibility of the new digital Gaussian pulse shaping algorithm based on bilinear transformation.     

Simulation and calibration of the response function of multi-sphere neutron spectrometer

In order to realize the on-line real-time measurement of neutron specmnn of ITER fusion, this paper presents a multi-sphere spectrometer system which consists of eight thermal neutron detectors, namely SP9 3He proportional counter, embedded in eight different diameter polyethylene spheres. The response function of eight polyethylene spheres of rnulti-sphere neutron spectrometer was calculated after the simulation of the neutron transport processes in multi-sphere spectrometer by adopting software Geant4. The peak of the response function is in the low energy region for smaller diameter polyethylene sphere. As the polyethylene sphere diameter increased, the peak of the response function moves to the high energy region. The experimental calibration adopts 241Am-Be neutron source. The relative error between normalized data of experiment 47t solid angle counts and normalized data of simulated detection efficiency of 4in to 8in polyethylene sphere is from 1.152% to 12.222%.The experimental results verify the response function of the simulation. All these results provide a theoretical and experimental basis for solving the on-line real-time neutron spectrum of ITER fusion.     

Relative spectral response calibration using Ti plasma lines

This work introduces the branching ratio(BR) method for determining relative spectral responses,which are needed routinely in laser induced breakdown spectroscopy(LIBS). Neutral and singly ionized Ti lines in the 250–498 nm spectral range are investigated by measuring laser-induced micro plasma near a Ti plate and used to calculate the relative spectral response of an entire LIBS detection system. The results are compared with those of the conventional relative spectral response calibration method using a tungsten halogen lamp, and certain lines available for the BR method are selected. The study supports the common manner of using BRs to calibrate the detection system in LIBS setups.     

239pu alpha spectrum analysis based on PIPS detector response function and variations with vacuum and distance

Effect factors of the absorption of the source,air,entrance window,and dead layer of a detector must be considered in the measurement of monoenergetic alpha particles,along with statistical noise and other factors that collectively cause the alpha spectrum to exhibit a well-known low-energy tail.Therefore,the estabUshment of an alpha spectrum detector response function from the perspective of a signaling system must consider the various factors mentioned above.The detector response function is the convolution of an alphaparticle pulse function,two exponential functions,and a Gaussian function,followed by calculation of the parameters of the detector response function using the weighted leastsquares fitting method as proposed in this paper.In our experiment,~(239)Pu alpha spectra were measured by a highresolution,passivated implanted planar silicon(PIPS)detector at 10 levels of vacuum and 10 source-detector distances.The spectrum-fitting results were excellent as evaluated by reduced Chi-square(x~2) and correlation coefficients.Finally,the variation of parameters with vacuum level and source-detector distance was studied.Results demonstrate that σ,τ_1,and τ_2 exhibit no obvious trend of variation with vacuum in the range 2000-20,000 mTorr,and at a confidence level of 95%,the values of τ_1 and τ_2 decline in a similar fashion with source-detector distance by the power exponential function,while the value of a declines linearly.     

Monte-Carlo Simulation of Response Functions for Natural Gamma-Rays in LaBr3 Detector System with Complex Borehole Configurations

Usually, there are several methods, e.g. experiment, interpolation experiment-based, analytic function, and Monte-Carlo simulation, to calculate the response functions in LaBr3 (Ce) detectors. In logging applications, the experiment-based methods cannot be adopted because of their limitations. Analytic function has the advantage of fast calculating speed, but it is very difficult to take into account many effects that occur in practical applications. On the contrary, Monte-Carlo simulation can deal with physical and geometric configurations very tactfully. It has a distinct advantage for calculating the functions with complex configurations in borehole. A new application of LaBr3 (Ce) detector is in natural gamma-rays borehole spectrometer for uranium well logging. Calculation of response functions must consider a series of physical and geometric factors under complex logging conditions, including earth formations and its relevant parameters, different energies, material and thickness of the casings, the fluid between the two tubes, and relative position of the LaBr3 (Ce) crystal to steel ingot at the front of logging tube. The present work establishes Monte-Carlo simulation models for the above-mentioned situations, and then performs calculations for main gamma-rays from natural radio-elements series. The response functions can offer experimental directions for the design of borehole detection system, and provide technique basis and basic data for spectral analysis of natural gamma-rays, and for sourceless calibration in uranium quantitative interpretation.     

Geant4 simulation of multi-sphere spectrometer response function and the detection of ~(241)Am–Be neutron spectrum

This paper is aimed at detecting the neutron spectrum of~(241)Am–Be, a widely used neutron source, with the SP9 ~3He proportional counter, which is a multi-sphere spectrometer system of eight thermal neutron detectors embedded in eight polyethylene(PE) spheres of varying diameters. The transport processes of a neutron in the multi-sphere spectrometer are simulated using the Geant4 code. Two sets of response functions of the PE spheres are obtained for calculating the~(241)Am–Be neutron spectrum.Response Function 1 utilizes the thermal neutron scattering model G4 Neutron HPThermal Scattering for neutron energies of ≤4 eV, and Response Function 2 has no thermal treatment. Neutron spectra of an~(241)Am–Be neutron source are measured and compared to those calculated by using the response functions. The results show that response function with thermal treatment is more accurate and closer to the real spectrum.     

Al2O3:C、LiF:Mg,Ti、LiF:Mg,Cu,P对本底辐射的热释光响应比较

用Al2O3:C、LiF:Mg,Ti、LiF:Mg,Cu,P热释光剂量计(TLD)测量湛江市区本底辐射的热释光响应,以选取适合低辐射场辐射剂量测量的TLD。它们的最低响应剂量依次为Al2O3:C(1–2μGy)、LiF:Mg,Cu,P(约2μGy)和LiF:Mg,Ti(>10μGy)。Al2O3:C的热释光峰温较低,对较长时间段(>30 d)的累积剂量,存在较明显的热释光衰退,剂量响应曲线偏离线性;LiF:Mg,Cu,P和LiF:Mg,Ti的发光峰温较高,数年内都很稳定。综合考虑灵敏度和稳定性,LiF:Mg,Cu,P更宜于低辐射场的累积剂量测量。     

两批LiF(Mg、Cu、P)剂量计在环境中测量结果的差异与原因分析

两批LiF（Mg、Cu、P）热释光剂量计对大亚湾核电站环境监测的结果产生了15％的差异。本文实验分析了差异产生的原因,发现并验证这种差异是由于它们对宇宙射线的响应和自身本底的差别而造成的。     

Neutron-gamma mixed field measurements by means of MCP-TLD600 dosimeter pair

In this paper, we compared the TL response of three types of thermoluminescence dosimeters, TLD600 (⁶LiF:Mg,Ti), TLD700 (⁷LiF:Mg,Ti) and MCP (LiF:Mg,Cu,P) after exposure to a n-γ mixed field in the fluence range of radiotherapeutic applications. Since a dosimeter pair is required to discriminate the two components of the mixed field, we analyzed the ability of each dosimeter pair to provide the fluence value in the mixed field. At this aim we performed a ⁶⁰Co-γ calibration and a neutron calibration for all three dosimeter types. Finally, a blind test was performed in order to analyze the accuracy of each dosimeter pair and we found that in this mixed field the fluence value obtained through the TLD600-MCP pair is as accurate as the value obtained through the most common TLD600-TLD700 pair.     

北京市 X 线摄影检查所致受检者的体表照射量

本文报道了北京市医疗照射剂量调查中,有关 X 线摄影检查及胆囊、肾孟造影等22种检查所致受检者体表照射量的调查测量结果。     

铜和磷杂质对LiF(Mg,Cu,P)热释光特性的影响研究

ＬｉＦ（Ｍｇ,Ｃｕ,Ｐ）和ＬｉＦ（Ｍｇ,Ｆｉ）热释光磷光体的ＴＬ特性的主要差别在ＴＬ灵敏度,奶量响应和热稳定性三个方面,其产生原因都与铜和磷杂质的掺入有关。ＬｉＦ热释光家族中,镁仍然是一种不可缺少的主要杂质,铜和磷杂质掺入后在磷光体中所形成的电子俘获中心和复合发光中心都与其他ＬｉＦ热释光磷光体有所不同,从而使其具有极高的ＴＬ灵敏性,异常的能量响应和较差的热稳定性。．     

LiF（Mg,Cu,P）磷光体的X线衍射分析

对我们实验室制备的LiF(Mg,Cu,P)磷光体的X线衍射分析表明,磷光体制备过程中除生成掺有Mg,Cu和P杂质的LiF晶体外,还产生了焦磷酸锂(Li_4P_2O_7)和另外一种尚不知其组成的晶体。前者(Li_4P_2O_7)对磷光体的灵敏度的稳定性,后者对磷光体的能谱响应有一定影响。     

Comparison between the low temperature thermoluminescence spectra in annealed LiF:Mg,Cu, LiF:Mg,Cu,P and LiF:Mg,Cu,Si

Two strong thermal peaks in the wavelength range 220-420 nm have been detected at 128 and 140 K in LiF:Mg,Cu, at 123 and 135 K in LiF:Mg,Cu,P and at 125 and 133 K in LiF:Mg,Cu,Si, respectively. The origin of these main TL peaks is discussed in terms of defect perturbed H-F and V_K-e type recombination, respectively. The relative intensity between the two peaks in each sample and the emission spectra are dependent on the dopants.Annealing at 240-390 °C can modify the low temperature TL features, especially in those samples doped with three impurities. The low temperature data give some clues to select most favourable dopants for future LiF-type dosimeters.     

Copper activated LiF nanorods as TLD material for high exposures of gamma-rays

Lithium fluoride (LiF) doped with proper activators is a highly sensitive phosphor commonly used for radiation dosimetry using thermoluminescence (TL) technique. Nanorods of this material activated with Cu, Mg and P as single dopants are synthesized in our laboratory and exposed to gamma-rays for their thermoluminescence (TL) properties. The induced TL glow curves of the Cu, Mg and P doped samples are similar with a single peak at 410 K. Copper doped sample is found to be the most sensitive sample with TL intensity around 65, 7 and 8 times of those of LiF:Mg, LiF:P and LiF:Mg,Cu,P, respectively, indicating that Cu is the luminescence center in the host of LiF nanorods, while Mg and P act as TL quencher particularly when used as codopants. These observations on the nanostructured form of LiF doped with these activators are entirely different from those of the widely studied LiF:Mg,Cu,P and LiF:Mg,Ti single crystals. The nanorods of LiF:Cu might be used for heavy doses measurement as they are sensitive to gamma-rays and have a linear TL response curve in a long span of exposures.     

国产氟化锂片型热释光探测器性能比较研究

本文报道了对常用国产ＬｉＦ（Ｍｇ，Ｃｕ，Ｐ）和ＬｉＦ（Ｍｇ，Ｔｉ）两类片型热释光探测器的６种产品进行剂量学性能比较研究的结果。根据国家标准“个人和环境监测用热释光剂量测量系统”的技术要求和实际需求，比较了这几种探测器的热释发光曲线，相对灵敏度，探测阈，线性度，光子能量响应，一批的均匀性，重复性和稳定性等剂量学特性。文中还对ＴＬ探测器应用中的有关问题作了讨论。