A magnetically enhanced 3-electrode wireless micro-geiger counter
Christine K. Eun, Tze-Ching Fung, Bhaskar Mitra, Yogesh B. Gianchandani · 2007
This paper explores a 3-electrode micromachined Geiger counter utilizing a high impedance (floating) electrode to control discharge energy, and its impact on sensitivity and response time. Permanent magnets in a sandwich configuration are used to enhance RF transmission from micro-discharges. Initially, weak (field-emission) leakage current charges the floating electrode capacitor (CP≈1.1 pF) to a high voltage through the charging gap (between floating electrode and anode). When beta radiation initiates a micro-discharge in the sensing gap (between floating electrode and cathode), CPdissipates through the low impedance path, lowering the voltage and quickly quenching the discharge. Permanent magnets, positioned perpendicular to the discharge path, increase the efficiency of electron-ion collisions and enhance the consequent RF transmission. Experiments conducted in a neon/air ambient with90Sr (0.1 μCi) showed a 10X-100X SNR improvement for the 3-electrode design over a similar 2-electrode design that does not utilize the floating electrode. Results also showed a significant increase in high frequency components in the presence of a magnetic field.