GB698980A - Ionizing radiation detector - Google Patents

Abstract

698,980. Condenser arrangements. COMMISSARIAT A L'ENERGIE ATOMIQUE. June 19, 1951 [June 27, 1950], No. 14558/51. Class 38 (iv). [Also in Group XL (b)] The high voltage necessary for a radiation detector such as a Geiger tube is derived from a condenser charged to a high voltage. As shown, a high voltage derived from a magneto is applied to housing terminals 10 of a transformer 4, the condenser 5 being charged from the secondary through a rectifying tube 7. During the charge a gas-discharge tube fires when the voltage across the transformer secondary rises above 70; the voltage across the tube then falls back to 60 volts. Almost the whole of the transformer secondary voltage is then across condenser 2. The condenser and transformer together form a circuit which is resonant at a little under alternator frequency. Ionization of the Geiger tube develops a pulse across the transformer 4 which acts as a matching impedance for the headphones. The charges on the system are then equalized by a resistor 6 whose impedance is high in comparison with series condenser 3, 2 and transformer 4. To prevent over-voltage on the Geiger tube, condenser 9 and resistor 6 constitute a circuit having a time constant five times smaller than that of the rejector comprising condenser 2 and transformer 4. During discharge, ionization of the Geiger tube develops a pulse across the transformer through condensers 2, 9. Transformer 4 thus acts as a headphonematching impedance. Resistor 6 maintains the direct voltage on the Geiger tube. The whole instrument may be enclosed in a casing filled with nitrogen S at a pressure of 5 kilograms/cm.<SP>2</SP>