The state of the vessel of the water calorimetry employed for the measurement of absorbed dose to water for electron beam for radiotherapy is introduced.Electron beams come to a complete stop within a short distance,dose gradients vary greatly from close to zero.A 12 MeV electron beamhas a typical range in water of 3 cm.The shape of the depth dose curve provides a significant constraint to the structure of the water calorimeters vessel,it is of a pancake cylindrical design.The correction factors of the absorbed dose are sensitive to the structure of the vessel,so further investigation is required.Less data avaliable for the comparison between different primary standards.Also a brief introduction for the the water calorimetry vessel at the National Institute of Metrology is given.%介绍了国际上医用电子束水量热计量热芯的发展概况.电子束表面剂量高且分布均匀,剂量建成区窄,在达到最大剂量点后,深度曲线迅速跌落.尤其是小于12 MeV的电子,其最大剂量深度在3 cm以内.电子的剂量学特征使得其量热芯的结构一般为扁平结构.这样的结构使得热传导和微扰修正因子的计算变得复杂.讨论量热芯结构对剂量修正因子的影响以及国际比对的现状.最后介绍了中国计量科学院相关研究的进展.
展开▼
