Abstract An electron water calorimeter is described and is used to experimentally determine beam quality dependent conversion factors, kQ, for two ionization chamber types in high-energy electron beams. The current water calorimeter was upgraded to obtain reproducible measurements in electron beams from 10 MeV to 22 MeV (corresponding beam quality index R50 ranging over 4.20–8.97 g cm−2). Measurements of radiation induced temperature rise are made using a plane-parallel glass vessel with calibrated thermistor probes in a 4 °C water phantom. Three types of plane-parallel chambers (PTW Roos, IBA PPC40 and SNC 1045) and two types of cylindrical chambers (PTW30013 and IBA FC65-G) are measured to directly derive beam quality correction factors in the same water phantom. Relative combined standard uncertainty for kQ factors of 0.56% for 10 MeV beams and above were achieved. General agreement is obtained between the relative electron energy dependencies of the kQ factors measured in this work and those derived from TRS-398 of the IAEA and recent other experimental investigations. Furthermore, the experimental kQ values obtained here will impact future updates of reference dosimetry protocols, and the current standard uncertainties in electron reference dosimetry can be reduced by the method proposed in this work.

中文翻译：

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直接测量临床电子束中电离室吸收剂量 k 因子

摘要 描述了一种电子水热量计，用于通过实验确定高能电子束中两种电离室类型的束质量相关转换因子 kQ。当前的水量热仪升级后可以在 10 MeV 到 22 MeV 的电子束中获得可重复的测量值（相应的束质量指数 R50 范围超过 4.20–8.97 g cm-2）。辐射引起的温升的测量是使用平面平行玻璃容器在 4 °C 水模体中校准的热敏电阻探头进行的。测量三种类型的平面平行腔室（PTW Roos、IBA PPC40 和 SNC 1045）和两种类型的圆柱形腔室（PTW30013 和 IBA FC65-G）以直接推导出同一水体模型中的光束质量校正因子。kQ 因子为 0 的相对组合标准不确定度。10 MeV 及以上光束达到 56%。在这项工作中测量的 kQ 因子的相对电子能量依赖性与从 IAEA 的 TRS-398 和最近的其他实验研究得出的那些之间获得了普遍一致。此外，此处获得的实验 kQ 值将影响参考剂量学协议的未来更新，并且本工作中提出的方法可以减少电子参考剂量学的当前标准不确定性。