窄X射线束屏蔽材料铅当量测量研究

辐射防护材料屏蔽性能常用铅当量表示,为了准确衡量不同防护材料的屏蔽能力,根据IEC 61331标准,研究建立了用于铅当量测量的X射线辐射质.利用EGSnrc软件对辐射质能谱进行了模拟,研究了不同厚度的铅对辐射质能谱的影响以及窄射线束X射线铅当量测量方法,并在窄射线束条件下对16种不同防护材料进行了铅当量测量.结果表明建...     

诊断水平X参考辐射质的建立

参照IEC 61267-2005《医用诊断X射线测量特性使用的辐射条件》关于辐射质测量与计算的方法,通过实际测量与计算确定符合JJF 1621-2017《诊断水平剂量计校准规范》对参考辐射质要求的纯铝过滤片厚度,制作了所需的纯铝过滤片并用半值层测量装置验证了辐射质,建立了校准诊断水平剂量计的X参考辐射质.     

低空气比释动能率系列过滤X射线辐射质的测量与研究

以ISO 4037中推荐的低空气比释动能率系列过滤X射线参考辐射为研究对象,设计合理的半值层测量实验,测量获取第一半值层的值;对建立的辐射质,利用碲锌镉能谱仪测量其过滤X射线能谱,将测量得到的脉冲高度谱经过数据处理和转换,计算出平均能量;根据X射线在材料铝和铜中的衰减规律,拟合单能X射线衰减曲线,计算出该系列过滤X射线...     

防护水平X射线电离室的校准及不确定度分析

防护水平电离室剂量计是辐射防护的主要计量器具,需要在窄谱参考辐射质下进行检定和校准。利用EGSnrc软件模拟了参考辐射质X射线能谱,分析得到的能谱分辨率和平均能量与ISO 4037-1推荐值的最大偏差分别为7.1％和1.04％,均满足规范要求。依托60~250kV X射线空气比释动能国家基准装置,在窄谱系列参考辐射质下完成了距离X光机1m处参考点的空气比释动能量值复现;然后通过替代法对两个传递电离室进行校准并完成量值传递;最后利用传递电离室复现的2.25m处的空气比释动能率对PTW-32002球形电离室进行校准,获得相应的校准因子,校准因子相对扩展不确定度为2.2%(k=2)。     

钨靶光管钼过滤X射线空气比释动能的量值复现北大核心CSCD

基于低能钨靶X射线光机,配置钼过滤材料参考建立了管电压为23kV、25kV、28kV、30kV、35kV的辐射质,其附加过滤均为0.06mm的钼片。测量了5个辐射质的半值层,结果显示,半值层值在0.346mmAl到0.405mmAl之间。有效能量在15.4~16.4keV之间,明显高于相同管电压激发钼靶光管产生的X射线辐射质。对乳腺X射线自由空气电离室进行了各个修正因子的测量,完成了空气比释动能的测量工作。     

重过滤窄谱X射线辐射质的研究与建立

为推进X射线空气比释动能量值传递的工作,实验室建立中能X射线参考辐射装置。通过实验测量和插值计算,建立符合ISO4037-1标准的X射线辐射质,建立的辐射质与ISO4037国际标准的相对偏差在5%以内,满足ISO4037-1的要求。     

MC模拟高纯锗探测器准直器对X射线能谱测量的影响

为了研究不同限束光阑准直器对测量结果的影响,使用MCNP5蒙卡模拟软件建立带准直器的高纯锗探测器模型.通过模拟分析准直器各项参数对高纯锗探测器测量X射线能谱的影响,确立了准直器的最佳尺寸,为实验室使用高纯锗探测器测量X射线能谱提供一定的参考依据.计算了透射等效孔径(TEA)准直器指标,分析了高纯锗探测器测量X射线得到的...     

X射线散射光子对剂量当量电离室影响

为了测量X射线辐射散射光子对剂量当量电离室的影响,根据ISO-4037建立X射线防护水平参考辐射场.采用PTW-32002 1L和PTW-32003 10L两个不同体积的球形空腔电离室在不同辐射质条件下通过影锥屏蔽法测量散射光子对不同电离室的影响程度.实验结果表明:散射光子对不同体积电离室影响程度不同,对于10 L球形电离室散射份额在2％左右,而对于1L球形电离室散射份额在4％左右.能量越高,散射光子的散射份额也会相对增大.     

40~125kV脉冲X射线参考辐射场的建立

为解决用于X射线诊断、安检等涉及到的脉冲X射线剂量监测仪表的时间响应修正问题,建立了模拟上述辐射条件的40~125kV脉冲X射线参考辐射场。该参考辐射场同时具备了常规辐射场特性和脉冲辐射场特性。基于栅控技术的高压发生器可以调控光管产生不同脉冲特性的X射线,使用脉冲时间测量模块对产生X射线的脉冲特性(上升和下降沿时间、曝光时间等)进行测量,得到的结果表明该参考辐射场可用于主动式剂量监测设备的时间响应修正和剂量溯源。     

低本底环境低能X射线参考辐射场的研究

在平均γ射线剂量率为9.9 nSv/h的环境下进行10 ～50 keV低能X射线参考辐射场研究.利用电离室RC6M测量辐射野的均匀性,使用9种材料的K荧光刻度碲化镉探测器,测量了微型X光机能谱,并计算了空气比释动能率.结果显示:在距X射线出口55 cm处水平方向均匀性好于95％辐射野尺寸约为14 cm,竖直方向辐射野尺寸为16 cm,按窄谱系列附加过滤后能谱与ISO4037中标准模拟谱基本吻合.     

高能X射线下水等效材料对水的等效性研究

针对水等效材料校准医用加速器中存在的问题,通过对比法测量水体模和3种水等效材料校准医用加速器的剂量学差异,分别给出PTW 30013和IBA FC65-G两种类型探测器在校准深度为5 cm和10 cm的修正因子。针对加速器日稳定性校准的必要性,通过近7个月的日稳定性测量结果,给出加速器漂移量和引起漂移的可能原因;针对水等效材料在相对测量中对水的等效性,通过测量12个辐射野的输出因子,得出水等效材料在相对测量中与水一致。最后给出水等效材料在高能X射线下水吸收剂量校准时的建议和注意事项。     

X reference radiation qualities produced with tube voltages above 300 kV for the calibration and testing of dosemeters

In the international standard ISO 4037-1, only X reference radiation qualities produced with tube voltages of up to 300 kV and with mean photon energies of lower than 250 keV are defined. Higher energy reference photon fields are given with a mean energy only from 662 keV (S-Cs) upwards. To close this energy gap, four new X radiation qualities, produced with tube voltages of 350 kV and 400 kV, were realised. The filtration of two of these qualities-called N-350 and N-400-was chosen in such a way that they agree with the specifications of the narrow-spectrum series (N-series) defined in ISO 4037-1. The other qualities which have been created-called H-350 and H-400-can be assigned to the high air-kerma rate series (H-series). The fluence spectra of these qualities were measured by using X-ray spectrometry. The values of 23 characteristic parameters were determined and compared with the ISO specifications for X-ray reference fields.     

一种高精度薄膜铂电阻温度计测量迟滞性的研究

为了研究热迟滞性对工业铂电阻温度计测量不确定度的影响,选取了8支高精度铂电阻温度计进行实验。在-50～150℃内,选择3个温度区间,采用两种标准方法(IEC 60751,ASTM E644)测量水三相点(0.01℃)和所选温度范围内的中间点的迟滞性变化。实验结果表明:4支薄膜铂电阻温度计在两种标准方法测量下,随着温度区间跨度增大,热迟滞性影响增大,IEC 60751标准方法测量的热迟滞性最大值为14.2mK,ASTM E644标准方法测量的热迟滞性最大值为20.5mK;选取4支铂丝铂电阻温度计在温度范围为-50～150℃测量时,IEC 60751和ASTM E644标准方法测量的热迟滞性数据最大值分别为1.1mK和0.9mK;铂丝铂电阻温度计热迟滞性明显小于薄膜铂电阻温度计。     

Portable TL dosemeter--ESD phantom combination for chest and lumbar spine radiography

A thermoluminescence dosemeter (TLD)—entrance surfacedose (ESD) phantom combination was calibrated in terms of air-kermain IEC RQR X-ray radiation qualities between 50 and 150 kV.The ESD phantom was designed and constructed as a part of thework. With the combination, air-kermas were measured for fourradiological examinations (two chest and two lumbar spine examinationsin two hospitals), and converted to ESD_a using Monte–Carlocalculated BSF data tabulated for different tube voltages, filtrationsand beam diameters at 1 m distance. The results agreed withthe ionisation-chamber measurements within the reported overalluncertainty of the TLD method. In the calibration, the ESD phantomcan be replaced by the ISO water slab phantom unaffecting thereported overall uncertainty. Backscatter-related parametersfor the ISO water slab phantom and the newly designed ESD phantomwere determined for the IEC RQR qualities used in the secondarystandard dosimetry laboratory of STUK at 1 m distance, includingan approximate H_p(10)/H_p(0.07) ratio.     

X射线半值层测量方法研究

根据ISO 4037建立了窄谱系列规范辐射质,研究了射束宽窄与探测距离对X射线半值层测量的影响.结果显示:当X射线能量较高时,在半值层的测量中,不可忽略散射的影响,需要在窄束下测量;在依据ISO 4037建立的窄谱X射线半值层的测量中,当管电压高于60 kV,对应的射束的能量高于45.8 keV时,需要在窄柬测量;适当的增加探测距离也可减少散射对半值层测量的影响.     

Dose rate dependency of electronic personal dosemeters measuring X- and gamma-ray radiation

Three models of electronic personal dosemeters (EPDs)-Siemens Mk 2.3, Rados RAD-60S and Vertec Bleeper Sv-were irradiated with seven photon beam qualities: 60Co, 137Cs and the ISO narrow spectrum series X-ray qualities N-250, N-200, N-150, N-60 and N-20. The personal dose equivalent rates delivered to the devices varied between 0.002 and 0.25 mSv s(-1). Measurements were made with the EPDs mounted free-in-air as well as against Lucite and water phantoms. Results for all models of EPDs showed differences in personal dose equivalent energy response for different energies covered by this range of radiation qualities, with different models showing variations from 15 to 65%. In some cases, the personal dose equivalent rate response of these devices varied by a factor of 3 between irradiations at typical calibration dose rates and those normally encountered by nuclear energy workers.     

Personal monitor glass badge: theoretical dosemeter response calculated with the Monte Carlo transport code MCNPX

This paper describes the results of the simulation of a radiophotoluminescent (RPL) dosemeter with the Monte Carlo transport code MCNPX. The aim of this study is to calculate the response with MCNPX of the RPL dosemeter in terms of equivalent doses H(p) (0.07) and H(p)(10) using X-ray photon radiation qualities N series, together with S-Cs and S-Co nuclide radiation qualities, specified in ISO 4037-1. After comparison with reference values versus experimental results, the deviation of the theoretical responses of the RPL dosemeter proved to be lower than 5 % for reference values and lower than 10 % for experimental results. This good correlation validates the model over the energy range studied.     

Comparison of the NIST and BIPM Air-Kerma Standards for Measurements in the Low-Energy X-Ray Range

A direct comparison was made between the air-kerma standards used for the measurement of low-energy x rays at the National Institute of Standards and Technology (NIST) and the Bureau International des Poids et Mesures (BIPM). The comparison was carried out at the BIPM using the BIPM reference beam qualities in the range from 10 kV to 100 kV. The results show the standards to be in agreement to around 0.5 % at reference beam qualities up to 50 kV and at 100 kV. The result at the 80 kV beam quality is less favorable, with agreement at the 1 % level.     

Comparison of the NIST and PTB Air-Kerma Standards for Low-Energy X-Rays

A comparison has been made of the air-kerma standards for low-energy x rays at the National Institute of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB). The comparison involved a series of measurements at the PTB and the NIST using the air-kerma standards and two NIST reference-class transfer ionization chamber standards. Results are presented for the reference radiation beam qualities in the range from 25 kV to 50 kV for low energy x rays, including the techniques used for mammography dose traceability. The tungsten generated reference radiation qualities, between 25 kV and 50 kV used for this comparison, are new to NIST; therefore this comparison will serve as the preliminary comparison for NIST and a verification of the primary standard correction factors. The mammography comparison will repeat two previously unpublished comparisons between PTB and NIST. The results show the standards to be in reasonable agreement within the standard uncertainty of the comparison of about 0.4 %.