共查询到19条相似文献,搜索用时 171 毫秒
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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)。 相似文献
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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。 相似文献
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Ankerhold U 《Radiation protection dosimetry》2007,123(2):137-142
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. 相似文献
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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。 相似文献
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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 ESDa 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 Hp(10)/Hp(0.07) ratio. 相似文献
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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. 相似文献
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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. 相似文献
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D. T. Burns P. Lamperti M. O’Brien 《Journal of research of the National Institute of Standards and Technology》1999,104(2):135-140
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. 相似文献
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Michelle O’Brien Ludwig Bueermann 《Journal of research of the National Institute of Standards and Technology》2009,114(6):321-331
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 %. 相似文献