介绍了该实验室建立的低能X射线(10～100kV)自由空气电离室。该电离室设计了三个不同宽度的收集极用于不同kV值的X射线测量。电离室测量照射量的总不确定度对25～100kV估计为0.39％(K=1),对10kV估计为0.45％(K=1)。该自由空气电离室与英国NE公司生产的治疗级次级标准剂量计NPL-2560比对,其结果与英国国家物理实验室 The low energy X - ray (10 ~ 100kV) free air ionization chamber established by this laboratory is introduced. The ionization chamber is designed with three collectors of different widths for X-ray measurements at different kV levels. The total uncertainty in the measurement of ionization chamber exposure is estimated to be 0.39% (K = 1) for 25-100 kV and 0.45% (K = 1) for 10 kV. The free air ionization chamber with the British NE company produced the treatment grade secondary standard dosimeter NPL-2560 compared with the results of the British National Physical Laboratory