102 deposition rate is the critical pirameter and this depends only on the dose rate. This ig not the cace for the BF Chamber, nowever, The fonirzntion curren produced in the BF3 Chamber is proportional to the number of fret neutrons which have been thermalized in the sixth centimeter polyethylene moderator and this depends on _ energy. According to Enyder and Neufeld, the ratio according to fast rem rate at five MEV and the depth of gix MEV in tiseve is ten to one, but at ten MEV it is only one to a hundred. All our instrument calibrations are done in terma of polonium beryllium and plutonium beryllium neutron sources. These have essentially the same spectron and so for the calibration of counters, counting time instruments all that is needed to know is the output of the source. However, for instrunents suoh as fonization chambers, which are also sensitive to gamma radiation, it is necessary to know the gamma output of the cources,