Radiation Damage Effects in Microwave Dielctric Substrate Materials

Permanent radiation damage effects on the microwave properties of the alumina, sapphire, and teflon-glass substrate as employed in microstrip and stripline microwave circuits have been investigated by means of a simple bandpass resonator. No changes in the microwave properties of alumina and sapphire substrates were noted to 1.3 × 108 rads (H2O) and 2 × 1015 neutrons/cm2 (E > 10 KeV), although slight discoloration of the alumina substrates was noted for gamma fluences as low as 104 rads. Gamma irradiation produced gradual increases in the dielectric constant and loss tangent of teflon-glass substrates, but neutrons did not appear to affect the microwave properties of these substrates to levels of 2 × 1015 neutrons/cm2.