The let factors rlet ( rlet = 0 . 05 ) of neutron response for liftld in various n + y mixed fields in the fast neutron reactor have been determined experimentally due to the existing let effects of the response for liftld to neutron absorbed dose . the experimental results show that the let factor for neutrons from thermal energy to 5mev energy is about 0 . 050 . so it is workable to measure the photon fluence in the pulse reactor with 7liftld 为确定liftld能否用于n 、混合场的区分测量，本文定义了let效应因子，并对liftld的let效应因子进行了实验测定，测量结果表明： liftld对热中子至5mev中子响应的let效应因子值约为0 . 050 ，因此，选用~ 7liftld用于脉冲堆光子注量测量是可行的。
2.
A uniform state ion chamber with double layers has been developed for distinct measurement in various n + y mixed fields in the fast neutron reactor . the cavity material is 6lif + 7lif . the inner wall material is 6lif and the outer wall material is 7lif 根据let效应因子的测量结果和快中子堆y谱、中子谱等基本资料，以及~ 6lif和~ 7lif对中子响应灵敏度有较大差异这一特点，研制了以~ 6lif + ~ 7lif为空腔、 ~ 6lif为外壁、 ~ 7lif为内壁的具有双层室壁结构的均匀固体电离室，并将其用于快中子脉冲堆n 、混合场区分测量，彻底剔除了热中子的干扰。
