OCTOBER, 1960, GODIVA III -- MINUTEMAN RADIATION EFFECTS TESTS

Transient radiation effects tests on silicon controlled rectifiers, associated Minuteman circuits, and tantalum and aluminum electrolytic capacitors were performed at the Godiva III prompt critical assembly, Los Alamos, New Mexico, on Oct. 27 and 28, 1960. Fourteen out of 31 SCR's exhibited firing at gamma radiation rates between 6 x 10 to the 5th power and 3 x 10 to the 6th power r/sec. The gamma-induced SCR leakage current at firing generally exceeded twice the initial holding current of the device. A possible method for predicting gamma rates for firing SCR's is indicated. An empirical relationship for dependence of SCR leakage current on gamma rate was determined, as I sub c = (6 = 3) x 10 to the minus 10 power and phi to the 1.2 plus or minus 0.1 power. Leakage resistance change factors as low as 3.6 x 10 to the minus 8 power and 2.6 x 10 to the minus 7 power for tantalum and aluminum electrolytic capacitors, respectively, were noted at gamma radiation rates up to 4.5 x 10 to the 7th power r/sec. A relationship between capacitor leakage resistance (R in ohms), capacitance (C in farads), and gamma radiation rate was determined at R = G/phi C, where C = 2.1 x 10 to the 5th power for aluminum foil capacitors, 3.29 x 10 to the 5th power for tantalum foil capacitors, and 1.81 x 10 to the 5th power for tantalum solid electrolyte capacitors. (Author)