Effects of γ-rays and neutrons on the noise behaviour of monolithic JFET circuits

Two monolithic technologies based upon JFETs were characterised from the point of view of their noise sensitivity to γ and neutron irradiation. Noise measurements on devices and circuits irradiated up to 100 Mrad(Si) absorbed dose of γ-rays and 4·10¹⁴ neutrons/cm² are presented. The experimental results show that the equivalent noise voltage spectrum is largely affected in the frequency region below 1 MHz. A smaller effect is observed in the high frequency region where channel thermal noise is dominant. Accordingly, the equivalent noise charge does not sizeably increase at the short signal processing times, below 100 ns, that are of interest for applications at high luminosity colliders