AN IMPROVED NUCLEAR DENSITY GAUGE. Quarterly Report No. 1 Covering the Period from June 1 to September 1, 1959

A mass gaging technique is being investigated in which the detector alternately views radiations transmitted through the test specimen and through a calibrated step wedge. Thulium-170 was used in initial investigations; however, sources of higher and lower energies are to be examined. Variations of balancing systmas are discussed and results of tests using NaI(Tl) and CsI(Tl) crystals with non-commutating systems are tabulated. Commutating system's operation was tested at a chopping frequency of 10 cps. Much smoother servo operation was noted than was demonstrated by the non-commutating system. A circuit diagram of the commutating system is included. (J.R.D.