A thermoluminescence dosimetry system for personal monitoring in Ireland

In 1993 the decision was taken to replace film badges with thermoluminescence dosemeters (TLDs) as the main form of dosemeter for both whole-body and extremity monitoring at the Dosimetry Service of the Radiological Protection Institute of Ireland (RPII) in Dublin. A review of commercially available automatic TLD systems was carried out to identify the system which best met the RPII's requirements. This paper describes the dosimetry system used, and, in addition, discusses the problems encountered and how these were addressed.     

Study of a method based on TLD detectors for in-phantom dosimetry in BNCT

A method has been developed, based on thermoluminescent dosemeters (TLD), aimed at measuring the absorbed dose in tissue-equivalent phantoms exposed to thermal or epithermal neutrons, separating the contributions of various secondary radiation generated by neutrons. The proposed method takes advantage of the very low sensitivity of CaF2:Tm (TLD-300) to low energy neutrons and to the different responses to thermal neutrons of LiF:Mg,Ti dosemeters with different 6Li percentage (TLD-100, TLD-700, TLD-600). The comparison of the results with those obtained by means of gel dosemeters and activation foils has confirmed the reliability of the method. The experimental modalities allowing reliable results have been studied. The glow curves of TLD-300 after gamma or neutron irradiation have been compared; moreover, both internal irradiation effect and energy dependence have been investigated. For TLD-600, TLD-100 and TLD-700, the suitable fluence limits have been determined in order to avoid radiation damage and loss of linearity.     

A TLD-based personal dosemeter system for aircrew monitoring

Evaluation of LiF:Mg,Ti thermoluminescence dosemeters (TLDs) according to the high-temperature ratio (HTR) method enables the determination of the dose-average linear energy transfer (LET), the mean quality factor and the dose equivalent in mixed radiation fields of unknown composition. The neutron contribution is assessed by the Extended Pair method calibrated in the CERN-EU High-Energy Reference Field (CERF). The advantages of the small passive detectors as an easy-to-handle monitoring system for in-flight surveillance are demonstrated by measurements on-board north-bound and trans-equatorial flights. The experimental results are compared with calculations by the well-established CARI code.     

Study on quality control parameters of a TLD system for individual monitoring

This work intends to identify and follow up quality control parameters important for the general improvement of our thermoluminescence dosemeter (TLD) system for Individual Monitoring that is currently preparing its accreditation according to the EN ISO/IEC 17025 Standard. A retrospective analysis of the readers' start-up tests revealed an eventual variation of parameters, like the high voltage, which may affect the light collecting system, and hence the TL dose results. This was investigated and although the high voltage requires a careful look, the stability and reproducibility of the TLD system was ascertained by the results of quality control procedures. As a consequence of this work, the start-up procedure was modified and the warning levels used for the start-up daily tests of the readers were derived from a more realistic approach.     

Argentine intercomparison programme for personal dosimetry

An Intercomparison Programme is being carried out in Argentina for individual monitoring services. The programme was designed to test, on a voluntary basis, the performance of the laboratories that provide individual monitoring services for X and gamma radiation fields in the range from low-level dose up to 100 mSv. Irradiations were performed in full accordance with ISO 4037-3 recommendations by the Regional Reference Centre for Dosimetry (CRRD), belonging to Atomic Energy Commission (CNEA) and the Physical Dosimetry Laboratory of the Nuclear Regulatory Authority (ARN). At the same time, several items have been asked to each participant pertaining to the action range, the detectors' characteristics, the laboratory procedures, the existence of an algorithm and its use for the dosemeter evaluation. In this study the evolution of the laboratories' performance throughout the programme, based on ISO 14146 acceptance criteria, is shown.     

虹膜识别的身份认证系统

基于虹膜识别的身份认证系统包括3部分:虹膜图像采集,虹膜图像预处理,虹膜图像编码和识别。预处理过程中对虹膜的精确定位,使定位后的虹膜图像具有平移、尺度和旋转的不变性。与现有其他方法相比,该方法将Symlets小波用于虹膜图像编码,使算法的运行速度大大提高,为Daugman方法的8倍, 克服了当前流行算法中计算量过大的问题。     

The use of active personal dosemeters as a personal monitoring device: comparison with TL dosimetry

The use of active personal dosemeters (APDs) not only as a warning device but also, in some cases, as an official and hence stand-alone dosemeter is rapidly increasing. A comparison in terms of dose, energy and angle dependence, among different types of APD and a routinely used whole-body thermoluminescence dosemeter (TLD) has been performed. Significant differences were found between the TLD readings and mainly some not commonly used APDs. The importance of choosing the best adapted APD according to the radiation field characteristics is pointed out.     

System for personal dosimetry in interventional radiology

The progress made in radiological image processing and transmission is being widely applied in new branches of medicine. The increasing use of interventional radiology in research and clinical practice means that new groups of workers are being exposed to radiation and need to be covered by a system of radiation protection. Interventional radiology requires the operator and assisting personnel to remain close to the patient; typically these procedures require placement of the hands within the radiation field. A system of hand dose monitoring was introduced in Poland in 2000. This system uses ring badges with TL dosemeters. The measurements conducted so far characteristically show an asymmetric right-sided distribution of monthly doses. As expected, operators and their assistants are the most exposed groups of medical personnel. Average hand doses may be very dependent on the type of procedure, personal skills and quality of equipment. The hand doses of these personnel are significant from a radiological protection point of view.     

EURADOS trial performance test for neutron personal dosimetry

This paper reports on the results of a neutron trial performance test sponsored by the European Commission and organised by EURADOS. As anticipated, neutron dosimetry results were very dependent on the dosemeter type and the dose calculation algorithm. Fast neutron fields were generally well measured, but particular problems were noted in the determination of intermediate energy fields and large incident angles, demonstrating the difficulties of neutron personal dosimetry. Of particular concern from a radiological protection point of view was the large number of results underestimating personal dose equivalent. A considerable over-response was noted in a few cases.     

基于自适应滤波的薄层厚度超声测量方法

针对应用超声脉冲回波法测量三层结构中的硅橡胶薄层厚度时回波混叠的问题,提出一种基于RLS(recursive least square)自适应滤波的解决方法。该方法将硅橡胶层下界面回波发生混叠的信号作为输入信号,将无硅橡层时的回波信号作为期望信号,通过RLS自适应滤波算法的处理提取出相互分离的有效下界面回波信号,实现硅橡胶薄层的测厚。研究不同滤波器阶数和遗忘因子对信号分离及测厚精度的影响,以输出信号的信噪比为指标选择最优的滤波参数。结果表明:该方法能够有效分离出发生混叠的硅橡胶薄层界下界面回波,能够测量0.15,0.17,0.19,0.21 mm 4种厚度的硅橡胶薄层,对回波部分混叠和完全混叠两种情况均有良好的适用性。     

基于CAN总线的流量监控系统

介绍一种基于CAN总线的流量监控系统。该系统由微机系统和涡街流量计构成。系统的设计为智能流量计的联网监控提供了理想的解决方案。     

A new algorithm for identifying abnormal glow curves in thermoluminescence personal dosimetry

In this paper an algorithm for the investigation of routine curves in thermoluminescence personal dosimetry is presented. In rare cases, the luminescence glow curves do not exhibit the expected form. They have an abnormal shape as a result of, for example, external contamination, hardware problems, and poor heat transfer. So, glow curves from a monthly exposure period are compared with regular glow curves. Each curve is divided into four regions of interest (ROIs) and the relationships between the different ROIs are analysed. There are few criteria combining all four ROIs, which are necessary to distinguish between normal and abnormal glow curves. For that, the numerical value and the channel of the curves maximum also need to be considered. In most cases an additional set of criteria permits the identification of the ROI in which the irregularity occurs.     

Calibration and testing of a TLD dosemeter for area monitoring

The response of a TLD-600/TLD-700 area dosemeter has been characterized in neutron fields around the 590 MeV cyclotron ring at the Paul Scherrer Institute (PSI). The dosemeter is based on a cylindrical paraffin moderator with three of each type of TLD chip at the centre, and is intended to use for area monitoring around accelerator facilities. The dosemeter is calibrated in terms of ambient dose equivalent using a non-moderated 252Cf neutron source. The ambient dose equivalent response has been tested in five locations where the neutron fields and dose rates have been well characterized by Bonner sphere spectrometer and active neutron monitor measurements. The different spectrum shapes and dose rates in the five locations permit the comparison of the behavior of the active and passive dosemeters in these neutron fields.     

A system of secondary standards for photon dosimetry

Translated from Izmeritel'naya Tekhnika, No. 10, pp. 48–49, October, 1990.     

Pilot study on the application of computerised glow curve analysis in TL based personal dosimetry services

Preliminary results of an inter-laboratory collaborative work on the application of computerised glow curve analysis to TL personal dosimetry are presented. Very simple analysis methods have proved to be useful for the evaluation of glow curves similar to those encountered in the dosimetric control of radiation workers. A first result obtained in the study has been the possibility of simplifying the TL working procedures by eliminating pre-annealing or pre-heating steps employed in conventional systems to avoid low temperature peaks. The presence of these unwanted peaks can be detected by the computerised evaluation methods, discriminating their contribution to the dosimetric TL data.     

A microprocessor based, multi-channel low-temperature monitoring system

A multi-channel low-temperature monitoring system and its design considerations are presented. The system is microprocessor based and specially designed to interface thermoresistive sensors in cryogenic experiments. The system can be easily expanded to accept any type of physical transducer and to perform other output functions, ie control functions.     

基于动态捕获区域的DC-TLD目标跟踪算法

为提升TLD目标跟踪算法的处理速度,以达到在更高分辨率视频中跟踪目标的实时性要求,在TLD算法框架的基础上,提出了一种基于动态捕获区域的TLD目标跟踪算法(DC-TLD)。算法采用前一帧目标位置作为当前帧目标位置的预测值,减小了目标位置的预测误差。研究了检测区域负样本出现需满足的条件,分析了检测区域大小对算法鲁棒性的影响。针对样本的访问方式,提出基于索引的访问方法,极大地减少了访问时间。实验结果表明,该方法不仅有效降低了TLD算法的样本检测时间,而且提高了算法的鲁棒性。     

Passive detectors for neutron personal dosimetry: state of the art

Passive, solid-state detectors still dominate the field of neutron personal dosimetry, mainly thanks to their low cost, high reliability and elevated throughput. However, the recent appearance in the market of several electronic personal dosemeters for neutrons presents a challenge to the exclusive use of passive systems for primary or official dosimetry. This scenario drives research and development activities on passive dosemeters towards systems offering greater accuracy of response and lower detection limits. In addition, further applications and properties of the passive detectors, which are not met by the electronic devices, are also being explored. In particular, extensive investigations are in progress on the use of solid-state detectors for aviation and space dosimetry, where high-energy neutron fields are encountered. The present situation is also stimulating an acceleration in the development of international standards on performance and test requirements for passive dosimetry systems, which can expedite significantly the implementation of techniques in commercial personal dosimetry services. Upcoming standards will cover thermoluminescence albedo dosemeters, etched-track detectors, superheated emulsions and direct ion storage chambers, attesting to the level of maturity reached by these techniques. This work reviews the developments in the field of passive neutron dosimetry emerged since the previous Neutron Dosimetry Symposium, reporting on the current status of the subject and indicating the direction of ongoing research.     

基于Auto Encoder的智能监控指纹识别系统

针对目前已有的嵌入式指纹识别系统往往采用手工提取,不能自动学习并提取识别所需的特征及识别正确率仍然不高的缺点,提出一种基于自动编码器(Auto Encoder)和LSSVM的指纹识别系统。首先,提出采用FPS200作为指纹传感器采集指纹数据,然后将采集的数据经过滤波和二值化等预处理,通过比较差异算法获得Auto Encoder中的权值和偏置等参数,从而得到训练好的Auto Encoder用于指纹图像特征提取。最后,将自动提取的特征进行训练和分类,将投票最多的分类作为指纹识别的结果。通过测试表明,系统能较精确地实现指纹识别,具有收敛速度快、正确识别率高和匹配时间短的优点。     

基于LabVIEW的包装生产线远程监控系统

在LabVIEW图形编程环境下,通过LabSQL调用Microsoft ADO控件完成包装生产线数据库的访问,将底层ADO及SQL操作封装成一系列的LabSQL VIs,使用LabVIEW远程面板访问技术,实现了通过网页浏览器对VI的远程控制,使用户可以在互联网上直接控制位于远端服务器上的VI前面板,对包装生产过程进行远程监控.