Neutron Damage in Pin Diode Phase Shifters for Radar Arrays

This paper presents the results of an experimental evaluation of neutron damage in phase shifter circuits (i.e., Microwave Integrated Circuits, MIC) utilizing pin diodes as switches. In addition, the effect of neutron bombardment on experimental pin diodes is discussed. Microwave phase shifter fixtures containing pin diodes as well as discrete experimental diodes have been irradiated by 14-MeV neutrons, l-MeV neutrons, and Cobalt-60 gammas. This paper discusses the decrease in lifetime and insertion losses, and presents lifetime damage constants. The experimental diodes have been found to be resistant to insertion-loss increase after neutron bombardment despite a severe degradation of the initial lifetimes. It appears that samples with an intrinsic width of 56 ¿m and an initial lifetime of 6 ¿ are capable of exposure to fluences approaching 1013 n/cm2 (1-MeV equivalent) with an insertion-loss increase of only 0.66 dB. These hardened diodes were shown to be capable of handling 4.5 kW of peak RF power.