5Rytz A. The international reference system for activity measurements of γ-ray emitting nuclides [ J ]. Int Appl Radiat Isot, 1983, 34 (8) : 1047 - 1056.
6Weiss H M. 4- ionization chamber measurements [ J ]. Nuclear Instruments and Methods, 1973, 112 ( 1 ) :291 - 297.
7Schrader H. Measurement of small currents using a modified Townsend method with fast programmable A/D and D/A converters. [ J]. Nucl Instr and Meth A, 1992, 312 (1 - 2) :34 -38.
8Hino Y, Kawada Y, Nazaroh. An improved leakage current compensation technique for a 4πγ ionization chamber system. [ J ]. Nuclear Instruments and Methods in Physics Research A, 1996, 369(2 -3) : 392 -396.
9Brancaccio F, Dias M S, Koskinas M F. Automatic system for ionization chamber current measurements. [ J ]. Applied Radiation and Isotopes, 2004, 61 ( 6 ) : 1339 - 1342.
