Characteristics of a 85Kr beta-particle source applied in Series 1 reference irradiations of DIS-1 direct ion storage dosemeters

Characteristics necessary to specify an ISO 6980 Series 1 reference radiation field were determined for a commercially available 85Kr beta-particle source, using a BEAM EGS4 Monte Carlo code. The characteristics include residual maximum beta energy, E(res), and the uniformity of the dose rate over the calibration area. The E(res) and the uniformity were also determined experimentally, using an extrapolation ionization chamber (EC) and a 0.2 cm3 parallel plate ionization chamber, respectively. The depth-dose curve measured with the EC gave a value 0.62 MeV for the E(res). Series 2 90Sr + 90Y and Series 1(85) Kr beta-particle sources calibrated for H(p)(0.07) at the secondary standard dosimetry laboratory (SSDL) of STUK were used to determine the energy and angular responses of DIS-1 direct ion storage dosemeters. The averaged zero angle H(p)(0.07) responses to the 90Sr + 90Y and 85Kr reference radiations were 135 and 80%, respectively. The responses were normalized to 100%, H(p)(0.07) response to 137Cs photon radiation.     

A prototype personal neutron dosemeter based on an ion chamber and direct ion storage

Ionisation chambers are sensitive to both neutrons and photons. In order to produce a neutron dosemeter based on an ion chamber a double-chamber system which allows for differential readings has to be built. The system consists of one chamber with high neutron sensitivity (e.g. A-150 or polyethylene with 10B or 6Li compounds) and one chamber with low neutron sensitivity (e.g. graphite or Teflon). Different combined dosemeter prototypes were produced and their responses for standard photon and neutron radiation fields, as well as various field spectra, were determined. The feasibility of neutron dosimetry with ion chambers and direct ion storage (DIS) electronics has been proved. The results obtained with prototype dosemeters indicate the system's promising potential for legal approval in the future. Apart from dosimetric properties, the advantages of the system are its small size and weight, easy readout and relatively low production cost.     

Present status of the personal neutron dosemeter based on direct ion storage

In this paper the present status of the Direct Ion Storage Neutron (DIS-N) prototype dosemeter (RADOS) is described. The separation of neutron from photon dose equivalent has been improved by adding tin shieldings. The neutron energy response has been changed by additional plastic covers containing 40% B4C in order to reduce the over-response to thermal neutrons. The responses of the dosemeters were determined for standard photon and neutron fields (monoenergetic neutrons, neutron sources and simulated workplace fields). Irradiations in real workplaces were also performed. The dependence of the neutron response on the angle of incidence was measured for different neutron sources.     

A legally approved personal dosemeter for photon and beta radiation based on direct ion storage

The novel DIS-1 dosemeter developed by RADOS is based on ionisation chambers with so-called Direct Ion Storage (DIS). The dosemeter can measure Hp(10) and Hp(0.07) of photon and Hp(0.07) of beta irradiation. The characteristics of the commercially available DIS-1 dosemeter were studied at the Paul Scherrer Institute, particularly in respect to the requirements laid down in the Swiss Dosimetry Ordinance. Detailed tests were carried out in terms of linearity, photon and beta responses, angle dependence, long-term stability of the signal, reproducibility and environmental conditions. The DIS-1 dosemeter has been qualified by the authority to conform to the requirements of the Swiss Dosimetry Ordinance for personal photon and beta dosemeters. It is now used as a legally approved personal dosemeter system at PSI.     

Comparison on characteristics of radiophotoluminescent glass dosemeters and thermoluminescent dosemeters

The radiophotoluminescent glass dosemeter (RPLGD) system is applicable for measurement of radiation dose of X rays and gamma rays by using radiophotoluminescent glass (silver-activated phosphate glass). When the radiophotoluminescent glass is exposed to ionizing radiation, stable luminescent centres are created. During pulsed ultraviolet laser excitation (337.1 nm) in the reader, the centres emit a radiation induced orange fluorescent light (600-700 nm). This phenomenon is called radiophotoluminescence. This study compared the RPLGD system with lithium fluoride (LiF) thermoluminescence dosimetry system and the results of the study revealed that the RPLGD had not only good basic characteristics for reproducibility of readout value, dose linearity, energy dependence and fading, but also infinite repeatable measurements and could be one of the most important radiation dose measurement instruments.     

New concept of IEC standards for radiation protection dosemeters

The International Electrotechnical Commission (IEC) develops new standards for radiation protection dosemeters which follow a new concept. They are much more flexible in detail, but still ensure the same measurement quality. They are, for example, no longer specific for the detector type, but rather specific for the measurement task, e.g. for individual monitoring with active direct-reading instruments. Another example is that they are flexible with respect to the ranges of influence quantities. The conceptual changes are described in this paper, together with the advantages this new concept provides for manufacturers, users and legislators.     

Comparison between direct ion storage and thermoluminescence dosimetry individual monitoring systems, and Internet reporting

A new electronic direct ion storage (DIS) dosemeter allows accumulated personal dose equivalent Hp(d) at depths of 10 mm and 0.07 mm to be monitored in a few seconds by inserting the dosemeter into a local reader without deleting the accumulated dose. The DIS system meets general requirements on individual monitoring of hospital personnel using ionising radiation. It differs greatly from off-line thermoluminescence dosimetry systems and offers many additional benefits. The non-volatile reading takes only 5 s, is taken as often as needed, and the data are collected into a dose database, where background radiation is subtracted. Individual personnel doses are reported in Intranet as well as on the Internet at regular intervals to the National Regulatory Authorities.     

Performance of a personal neutron dosemeter based on direct ion storage at workplace fields in the nuclear industry

In the framework of the EVIDOS project, funded by the EC, measurements were carried out using dosemeters, based on ionisation chambers with direct ion storage (DIS-N), at several workplace fields, namely, at a fuel processing plant, a boiling and a pressurised water reactor, and near transport and storage casks. The measurements and results obtained with the DIS-N in these workplaces, which are representative for the nuclear industry, are described in this study. Different dosemeter configurations of converter and shielding materials were considered. The results are compared with values for personal dose equivalent which were assessed within the EVIDOS project by other partners. The advantages and limitations of the DIS-N dosemeter are discussed.     

实现超高密度信息存储的最新进展

超高密度信息存储是信息科学发展的基石,本文综述了超高密度信息存储的材料及技术等方面的目的的研究进展。     

Effect of angular response properties of personal dosemeters on the estimation of effective dose using two dosemeters

Even though the two-dosemeter approach successfully solved the underestimation problem of the single-dosemeter approach for posterior incident radiations, this approach significantly overestimates effective dose for the lateral and overhead beam directions when isotropic-responding dosemeters are used for measurement. This kind of overestimation can be reduced by using anisotropic-responding dosemeters whose responses decrease as the incident angle increases, i.e. from 0 degree (normal incidence) to 90 degrees (lateral incidence). To quantify the reduction of overestimation by using anisotropic-responding dosemeters, this study applied the two-dosemeter approach to several types of anisotropic-responding dosemeters--both ideal and commercial--and then compared the results with those of isotropic-responding dosemeters. This study also derived a set of angular response factors (ARF) which can be used to develop a personal dosemeter with ideal angular response properties for use in the two-dosemeter approach.     

Biomolecular optical data storage and data encryption

The use of bacteriorhodopsin (BR) as an active layer in write-once-read-many optical storage is presented. This novel feature of BR materials may be used on a wide variety of substrates, among them transparent substrates but also paper and plastics. The physical basis of the recording process is polarization-sensitive two-photon absorption. As an example for this new BR application, an identification card equipped with an optical recording strip is presented, which has a capacity of about 1 MB of data. The recording density currently used is 125 kB/cm/sup 2/, which is far from the optical limits but allows operation with cheap terminals using plastic optics. In the examples given, data are stored in blocks of 10 kB each. A special optical encryption procedure allows the stored data to be protected from unauthorized reading. The molecular basis of this property is again the polarization-sensitive recording mechanism. The unique combination of optical storage, photochromism, and traceability of the BR material is combined on the single-molecule level. BR introduces a new quality of storage capability for applications with increased security and anticounterfeiting requirements.     

Encrypted holographic data storage based on orthogonal-phase-code multiplexing

We describe an encrypted holographic data-storage system that combines orthogonal-phase-code multiplexing with a random-phase key. The system offers the security advantages of random-phase coding but retains the low cross-talk performance and the minimum code storage requirements typical in an orthogonal-phase-code-multiplexing system.     

Data storage in 2000-trends in data storage technologies

Recent projections by experts in computer systems and semiconductor technology indicate that in the year 2000, personal computers will have a processing speed of 100 million instructions per second and a semiconductor RAM capacity of 1 Gbyte. To work with such a system, data storage devices will need to provide more than 10 Gbytes of capacity and a data rate of 100 Mbyte/s. The advances required by magnetic and magnetooptical disk drives to meet these requirements are examined. Plausible system configurations for achieving these goals are described. A magnetic disk drive utilizing eight 3.5-in. disks on one spindle appears to be a possible configuration. Because of a larger areal density, a magnetooptical disk drive could meet the capacity requirements with only a single 3.5-in. disk. On the other hand, achieving the 100-Mbyte/s data rate and access times comparable to those of magnetic disk systems will require some technological breakthroughs. Without these breakthroughs and assuming magnetic disk progress as expected, magnetooptical disks are expected to provide many of the functions which floppy disks provide today-transfer of programs and databases between systems and economical offline storage     

DR在矩阵剂量仪精确对位中的应用

针对矩阵剂量仪采用γ指数分析法进行剂量验证(通过率达90%),仪器对位精度要求需达到0.2 mm的情况,为解决仪器外壳划线与探测器位置中心线对位误差带来了剂量验证误差,采用DR(直接数字化X射线摄影)系统摄像,仪器对位误差达到0.2 mm,保证剂量验证对阵列探测器中心位置与等中心的精确对准要求,剂量验证γ指数通过率达到95%以上。     

虚拟信源直接数据域高分辨算法

目标高分辨算法的性能优劣直接影响声纳、雷达的目标感知能力。考虑基于空间平滑思想的直接数据域算法,在干扰方向产生稳定的零陷。虚拟出期望信号并加入到接收数据中,将实际目标当作干扰,通过直接数据域自适应的方法在实际目标方向产生零陷：在波束图的左半部分适当位置虚拟一个期望信号,得到0°~90°的零陷分布图,在右半部分适当位置虚拟一个期望信号,得到90°~0°的零陷分布图,将这两部分零陷图组合后,取倒数得到实际功率谱图。该方法可以在单快拍、未知目标信号先验信息的情况下得到稳定、高分辨力的目标方位估计,并能够处理相干信号。仿真分析验证了算法的正确性和良好性能。     

Active neutron dosemeters based on microdosimetric principles: research studies

Over the past few years, the Institute for Radiation Protection and Nuclear Safety (IRSN) has been studying a personal electronic neutron dosemeter and an ambient electronic neutron dosemeter based on experimental microdosimetric principles using low pressure proportional counters. The results obtained in 2000 and in 2001 with the cylindrical tissue-equivalent proportional counter developed for use in radiation protection and filled with a low pressure tissue-equivalent gas (propane based) are presented here.     

Acrylamide-based photopolymer for microholographic data storage

The application of an acrylamide-based holographic photopolymer for bit-format holographic data storage is investigated. Holographic reflection gratings with a spatial frequency of 5640 lines/mm and micrometer radius were recorded at 532 nm wavelength using 1 μJ write energy. A diffraction efficiency of up to 0.2% was measured.     

Inorganic materials for optical data storage

Recyclable holographic (optical) storage in inorganic materials is nowadays possible due to the advent of laser. Various performance parameters of the state-of-the-art of optical storage are discussed in detail with reference to the well-established case of ferroelectric lithium niobate (LiNbO₃). Various physicochemical techniques are employed in understanding the microscopic mechanisms responsible for optical storage in LiNbO₃. A short summary of other inorganic materials capable of holographic storage is also presented.