A CMOS INTEGRATED PULSE MODE ALPHA-PARTICLE COUNTER FOR APPLICATION IN RADON MONITORING

A custom integrated circuit for detecting alpha particles for applicat ion in the monitoring of radon has been designed and tested, The desig n uses the reverse-biased well to substrate capacitance of a p-n junct ion in a conventional CMOS process as a sense capacitor for incident a lpha particles, A simple CMOS inverter is used as an analog amplifier to detect the small potential change induced by an alpha-particle stri ke on the sense capacitor; The design was implemented in a 1.2-mu m co nventional CMOS process with a sense capacitor area of 110 mu m(2). Te sts carried out under vacuum conditions using a calibrated Am-241 alph a-particle source showed an output voltage swing of greater than or eq ual to 2.0 V for an alpha event, The detector is also shown to have go od immunity to noise and high-quantum efficiency for alpha particles.