Fast identification of radionuclides at low activity levels under dynamic conditions is crucial to public safety. The sequential Bayesian approach, leveraging prior information and incorporating both energy and interarrival time distributions, has demonstrated effectiveness in fast identification. However, conventional implementations typically require prior knowledge of radionuclide activity and are rarely applied under dynamic measurement conditions. Even when applied in such scenarios, these methods often rely on prior knowledge of the relative distance between the source and the detector. To overcome these limitations, a theoretically optimized sequential Bayesian approach is proposed, eliminating the need for prior knowledge of source activity and source-detector geometry, and demonstrating strong robustness to count rate fluctuations caused by source movement. Additionally, the method accurately discriminates gamma-rays originating from background radiation, Compton scattering, and radionuclide-specific emissions, significantly improving identification performance. Experiments were conducted using a mobile platform equipped with a LaBr3 (Ce) scintillator detector, simulating realistic scenarios where radionuclide (137Cs, 60Co, and 133Ba) moved laterally across the detector's field of view at varying speeds and distances. The identification time windows varied by condition, with the shortest being 6.7 s. The results show that all radionuclides were correctly identified at speeds up to 150 mm/s, under a maximum source dose rate contribution of 0.10 mu Sv/h. At 150 mm/s, the minimum identification times for 137Cs, 60Co, and 133Ba were 2.04 s, 1.66 s, and 1.78 s, respectively, corresponding to maximum dose rate contributions of 0.10 mu Sv/h, 1.29 mu Sv/h, and 0.89 mu Sv/h. These findings highlight the method's effectiveness for fast, reliable radionuclide identification under dynamic measurement conditions, underscoring its potential application in public-safety radioactive material detection.

The rapid identification of γ -emitting radionuclides with low activity levels in public areas is crucial for nuclear safety. However, classical methods rely on full-energy peaks in the integral spectrum, requiring sufficient count accumulation for evaluation, thereby limiting response time. The sequential Bayesian approach, which utilizes prior information and considers both photon energies and interarrival times, can significantly enhance the performance of radionuclides identification. This study proposes a theoretical optimization method for the traditional sequential Bayesian approach. Each photon is processed sequentially, and the corresponding posterior probability is updated in real time using a noninformative prior from the Bayesian theory. By comparing the posterior probabilities of the background and radionuclides based on the energy variance and time interval, the type of γ -rays can be identified (background characteristic γ -rays, Compton plateaus γ -rays, or radionuclide-specific characteristic γ -rays). By integrating the information from these multiple characteristic γ -rays, the presence and type of radionuclides were determined based on the final decision function and a set threshold. Based on theoretical research, verification experiments were conducted using a LaBr_3 (Ce) detector in both low-and natural background radiation environments with typical radionuclides (137Cs, 60Co, and 133Ba). The results show that this approach can identify 137Cs in 7.9 s and 8.5 s (source dose rate contribution: approximately 6.5× 10^-3 μGy/h), 60Co in 8.1 s and 9.8 s (approximately 4.8× 10^-2 μGy/h), and 133Ba in 4.05 s and 5.99 s (approximately 3.4× 10^-2 μGy/h) under low and natural background radiation, respectively, with a miss rate below 0.01 % . This demonstrates the effectiveness of the proposed approach for fast radionuclides identification, even at low activity levels and highlights its potential for enhancing public safety in diverse radiation environments.

The secondary neutrons produced during proton therapy could increase the risk of secondary tumors. Due to the lack of nuclear data for neutrons with energies above 20 MeV, the accuracy of Monte Carlo simulation still needs to be improved. The secondary neutrons distribution is being studied in this work, combining TOPAS simulation and experimental measurement. The TOPAS simulation results indicate that the neutron ambient dose equivalent at 50 cm from the isocenter ranges from 0.19 to 18.6 mSv/Gy, whereas measurements using the FHT762 WENDI-2 dosimeter recorded values ranging from 0.96 to 44.21 mSv/Gy.

The accurate measurement of tube voltage plays a crucial role in the imaging quality of mammography diagnosis. Based on the measurement model and methodology of tube voltage, this paper evaluates the measurement uncertainty of the relative intrinsic error for a non-invasive tube voltage meter used in mammography diagnosis. The main sources of uncertainty components considered in the evaluation process include the standard measurement system, traceability of the reference standard, annual stability of the standard, instrument reading resolution, and measurement repeatability. By synthesizing these components according to their relationships, the uncertainty of the calibration result is determined, and the final expanded uncertainty is found to be 2.0%.

To establish the national primary standard for beta radiation tissue absorbed dose and to achieve international equivalence,the National Institute of Metrology(NIM)of China participated in the BIPM KCDB:EURAMET.RI(Ⅰ)-S16 comparison that organized by EURAMET(European Association of National Metrology Institutes)and coordinated by the Physikalisch-Technische Bundesanstalt(PTB)in 2019.The circulation of the chamber and of the electronic measurement system will be effected in a star pattern,with both devices being sent back by every five participants to the pilot laboratory for testing.16 institutes from 16 different countries will calibrate the comparison device according to their quality system in beta reference fields of the radionuclides 147Pm,85Kr,90Sr/90Y and 106Ru/106Rh.NIM calibrated the transfer ionization chambers using its beta radiation tissue absorbed dose primary standard,determining the calibration factors for Hp(0.07)at incident angles of 0°,45°,and 60° in the radiation field of 85Kr and 90Sr/90Y sources,as well as the calibration factors for Hp(3)at various angles for the 90Sr/90Y source.The calibration factors obtained in this work were compared with the reference values provided by EURAMET.The relative deviations of the calibration factors for Hp(0.07)at incident angles of 0°,45°,and 60° from the 90Sr/90Y and 85Kr sources compared to the reference values are better than±0.8％;The relative deviations of the calibration factors for Hp(3)at incident angles of 0°,45°,and 60° from the 90Sr/90Y source compared to the reference values are better than±0.9％.The relative deviations for the nine results are better than±1％.These results were incorporated into the International Bureau of Weights and Measures(BIPM)Key Comparison Database(KCDB),achieving international mutual recognition for the personal dose equivalents Hp(0.07)and Hp(3)in beta radiation.

For the purpose of obtaining the smaller uncertainties for Hp(3) and Dp lens in 90Sr/90Y beta reference fields, a new dose determination method based on the Monte-Carlo simulation was proposed. The conversion coefficients from the absorbed dose in air, at the reference point of the extrapolation ionisation chamber, Dair, det to Hp(3; α) and the conversion factors from Dair, det to Dp lens(α) were calculated with EGSnrc, respectively, for the irradiation angles from 0° to 60°. Compared with the dose determination method in International Organization for Standardization (ISO) 6980 standard, the uncertainty reductions of 7.7-52.8% for Hp(3; α) and 7.9-55.0% for Dp lens(α) were achieved, respectively. In addition, for the conversion coefficients from the reference absorbed dose DR to Hp(3; α), the calculations were performed for more irradiation conditions, which are not included in the current ISO 6980 standard. For the calculations of the conversion factors from DR to Dp lens(α), the eye and head phantoms with Chinese characteristics were utilised, which makes the conversion factors more suitable for use in China.

核技术应用是国民经济的重要组成部分,而核安全是核技术应用的生命线,也是国家安全体系的重要组成部分.采用辐射监测仪表开展电离辐射剂量监测已成为确保核安全的重要手段,主要体现在核事故"事前"预警监测和"事后"应急监测,剂量测量的准确性和相应评价数据的可靠性可指导防护措施更加科学合理,并在发生事故后及时作出科学有效的决策.

为实现β射线组织吸收剂量的量值复现,通过实验和模拟计算得到了基于90Sr/90Y和85Kr源的辐射场和外推电离室参数,以及外推电离室相关修正因子,实现了展平过滤条件下组织吸收剂量率的量值复现.为后续参加β射线剂量相关的国际比对,进行β射线个人剂量当量Hp(0.07)的量值传递提供基础.

为科学合理地评价少铅/无铅材料的防护效果,需要准确检测该类材料的屏蔽性能.通过文献调研,结合现行相关标准,从 X射线辐射质、检测设备和检测方法 3 个方面对防护材料屏蔽性能检测进行介绍.根据检测布局的不同可分为以下 5 种检测方法:窄射束条件下探测器与被检材料距离较远,无法探测到被检材料产生的次级辐射,因而不适用于少铅/无铅材料检测;宽射束条件辐射束立体角增大且探测器与被检材料距离较近,利于少铅/无铅材料检测,但对被检材料面积以及探测器选取方面存在一定要求;逆宽射束条件通过窄束以及平板电离室实现检测,但存在小野问题;改进的逆宽射束条件利用 IB-AT和 IB-AP 两种布局减少衰减前后能谱的差异,但实施较为繁琐;改进的宽射束可降低小野问题带来的影响,但仍存在衰减前后能谱差异对结果带来的影响.在实际操作中可根据其实验条件和具体防护需求选择相应的检测方法.

Human eye lens is an organ vulnerable to radiation damage. Through self-developed human skull model, a spherical ionization chamber was embedded in the ball to directly measure the eye lens individual dose equivalent Hp(3). Aiming at the accuracy evaluation of Hp(3) in radiation environment, the following research was carried out in this paper: Firstly, the instrument was calibrated under the S-Cs γ-ray radiation quality condition specified in the GB/T 12162.1 standard, and a calibration factor was obtained, NH=1.19 μSv/pC. Then, the correction factors k(E,α) were determined under different energy and incident angle conditions. At the same time, the background current and polarization effect were experimentally measured. Without the correction of energy and incident angle, the relative error of the energy response was -0.9%-12.6% in the energy range of 33 keV-1.25 MeV, and the relative error of the angle response was -7.9%-0% in the range of -60°-60°. At the same time, the factors affecting the accuracy of the measured value of the chamber were discussed. The relative expanded uncertainty of the calibration factor was 5.6% (k=2); when the energy and incident angle were known and unknown, the relative expanded uncertainty of the measured value of Hp(3) were 9.4% (k=2) and 18% (k=2) respectively. For radiation fields with unknown energy and incident angle, the Hp(3) value in the radiation field can be obtained directly by using the ionization chamber within the uncertainty range. This study can provide a reference for the accurate measurement of individual dose equivalent of eye lens.

To grasp the metrological performance indicators of the BeO optically stimulated luminescent (OSL) dosimetry system and verify whether it meets the needs of personal dose monitoring, the OSL dosemeter containing BeO optically stimulated luminescent detectors was placed in and irradiated with X-ray and γ-ray reference radiation fields. Performance test research on nonlinear response, coefficient of variation, energy response, angular response, and repeatability were carried out for the personal dose equivalent Hp(10). The nonlinear response ranged from 0.92 to 1.05 in the dose range of 50 μSv to 1 Sv, and the coefficient of variation ranged from 0.55% to 4.8%. The energy response ranged from 0.71 to 1.01 in the energy range of 33 keV to 1.25 MeV. The angular response ranged from 0.97 to 1.22 in the range of 0° to ±75° angle of incidence. The irradiation dose of 1 mSv, 5 mSv and 10 mSv were repeated 8 times, and the corresponding dose repeatability were 0.99 - 1.00, 0.99 - 1.00 and 0.97 - 1.00, respectively. The results showed that the BeO OSL dosimetry system meets the requirements of the IEC 62387-2020 standard and can be used for personal dose monitoring.

Extrapolation chambers are widely used to detect the weakly-penetrating types of radiation beams. Normally, the sensitive volume of them is limited, only a few cubic centimeters. Their collecting electrodes use sheet structure, which lead to more backscattering photons. In this work, a large volume extrapolation chamber with (235–1413) cm3 was designed for the absolute measurement of air kerma strength of 125I brachytherapy seeds. The developed chamber has the following innovation: large sensitive volume and the Aluminized Polyethylene terephthalate (PET) collecting electrode foil. In order to give a more comprehensive performance evaluation for the designed chamber, a series of experiments were conducted. Evaluation parameters include leakage current, saturation curve, polarity effect, ion collecting efficiency, linearity of response, collecting area and zero point. Those tests were measured in the standard X-ray radiation field. A comparative experiment with the primary standard free air chamber (FAC) was performed. Moreover, extrapolation curve was measured in 125I radiation field. Evaluation results show a good behavior of the extrapolation chamber. The Al-coated PET collecting electrode influence the response of the chamber to 0.07% with the simulation of MCNP5 Monte Carlo. All the results indicate the usefulness of the extrapolation chamber for the absolute measurement for 125I seeds.

为建立稳定的pA级直流电流源,采用了基于电离法建立的恒流源系统,该系统包括γ射线辐射场和空腔电离室系统.利用γ辐射场对电离室辐照产生稳定的电离电流作为电流源的源头.结合环境参数采集装置、高增益负反馈单元和控制系统对直流恒流源的重复性和稳定性进行测量.测量结果表明,该恒流源系统的重复性相对标准偏差为0.04％和半年内的稳定性相对漂移为0.18％,表明可用于提供稳定的pA级直流恒流源.

A transition edge sensor (TES) is extremely sensitive to changes in temperature, and combined with a high-Z metal of a certain thickness, it can realize high-energy resolution measurements of particles such as X-rays. X-rays with energies below 10 keV have a weak penetrating ability, hence, only gold or bismuth of a few micrometers in thickness can guarantee a quantum efficiency higher than 70%. Therefore, the entire structure of the TES X-ray detector in this energy range can be realized using a microfabrication process. However, for X-rays or $$\gamma$$ -rays from 10 keV to 200 keV, submillimeter absorber layers are required, which cannot be realized using the microfabrication process. This paper first briefly introduces a set of TES X-ray detectors and their auxiliary systems, and then focuses on the introduction of the TES $$\gamma$$ -ray detector with an absorber based on a submillimeter lead-tin alloy sphere. The detector achieved a quantum efficiency above 70% near 100 keV and an energy resolution of approximately 161.5 eV at 59.5 keV.

为准确评估β射线剂量仪校准因子的不确定度,将经过溯源的薄窗电离室放置在β射线辐射场的测量点处进行测量得到剂量率参考值,然后采用替代法将β射线剂量仪放在同一位置进行测量得到指示值,通过二者的比值得到β射线剂量仪的校准因子,并对校准因子的不确定度进行评定.不确定度的来源主要包括参考辐射场的均匀性、替代法测量过程中位置的一致性、显示值的统计标准偏差等.结果表明在校准过程中,通过提高参考辐射场的均匀性和参考位置的一致性可以改善校准因子的不确定度.

近距离放射治疗用125 I粒籽源具有低能、低剂量率的特点,基于绝对测量原理,利用现有的自由空气电离室无法实现空气比释动能强度的准确测量,因此设计了测量125 I粒籽源的空气比释动能强度专用的外推电离室.电离室的设计需要满足带电粒子平衡条件,通过蒙特卡罗模拟计算与理论分析对电离室的关键部件结构设计进行了研究,包括光阑、高压极、收集极、栅极及分压电阻等.设计的专用电离室采用锥形束照射方式,增加电离室的有效测量体积占比,相比自由空气电离室有效测量体积占比由0.3％ 提升至12％.采用电荷积分法对活度标称值为3.404×107 Bq的6711型125 I粒籽源空气比释动能强度进行了测量,测量结果为1.250μGy·m2·h-1(Urel=1.6％,k=2).通过进一步优化设计,该外推电离室可用于粒籽源空气比释动能强度的量值复现,为建立近距离放疗剂量的量值传递体系提供技术基础.

In order to accurately measure the environmental level dose rate, based on the G(E) function method and conversion of complete spectra without deconvolution method, the energy spectrum and dose rate of X/γ ray was measured for calculating spectrum-dose conversion coefficient. And finally the conversion of energy spectrum to dose rate is realized. The residual difference between the calculated dose rate by the energy spectrum-dose method and the measured dose rate value is approximately 0, which proves that the method is self-consistent. Experiments have been conducted in 137Cs and 60Co radiation fields, and the maximum relative error of dose rate is ±10%, which proves that the G(E) function method and Conversion of complete spectra without deconvolution method are feasible for energy spectrum-dose conversion.

为了解决主动式电子剂量率仪在脉冲辐射条件下的溯源需求,评估主动式电子剂量率仪测量脉冲辐射剂量的准确性,本文采用栅控技术于中国计量科学研究院建立了用于辐射防护剂量量值传递的脉冲X射线参考辐射场,具有曝光时间可调的特性.对脉冲X光管的管电压、曝光时间、脉冲上升/下降时间、辐射场均匀野大小进行了测试,同时对脉冲辐射场空气比释动能率测量方法进行了研究.研究结果如下:利用介入法示波器测量管电压,测量值与管电压预设值在100 kV时,相对偏差为0.19％.在建立的均匀辐射场中,利用电离室实现了脉冲场的空气比释动能率的测量,当管电压为60 kV,管电流为50 mA时空气比释动能率约为3 mGy/s.本文研究结果可为后续空气比释动能率定值提供参考.

在电离辐射空气比释动能基准量值复现过程中,g因子作为关键组成部分之一参与量值复现和不确定度计算,其量值的确定需要通过光子的质能传输系数和质能吸收系数计算得到.采用不同的软件,在不同参数设置条件下模拟计算并对结果进行比较.结果 显示采用EGSnrc计算结果更为合理,而且对于低能光子,尽管g因子相对较小,但在不同的参数设置条件下所得到的数值差异较大.因此对于涉及到低能光子的质能传输系数和质能吸收系数的计算和使用过程中,需对有关相互作用的物理机制予以重视.

At present, there are many kinds of multi-parameter measuring instruments with the function of half-value layer(HVL) measurement in the market, which can be used to measure the HVL value of diagnostic X-ray equipment. Based on three types of multi-parameter measuring instrument, we analyze many factors that may affect the measurement of HVL, such as X-ray tube voltage, tube current, exposure time, and the placement of the HVL instrument, and then design several groups of control tests. The test results show that the deviation of the tube voltage leads to changes of the HVL and that more stable measurement results can be obtained with appropriate exposure time.