GB909719A - Improvements in or relating to condenser chamber dosimeters - Google Patents

Abstract

909,719. Electrostatic measuring instruments. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Oct. 18, 1960 [Oct. 26, 1959], No. 36285/59. Class 37. [Also in Group XX] A condenser chamber dosimeter comprises a casing constituting one electrode, and two further electrodes insulatedly mounted coaxially therein, two of the three electrodes being spaced apart to provide between them the sensitive volume. In Fig. 1, the outer casing 1 forms one electrode, and the two inner electrodes 4, 5 are mounted coaxially within it on insulators 2, 3. Insulator 2 also has moulded integrally with it two foils wound to form a condenser 8 which acts as a capacitance between electrodes 1 and 4, this capacitance being large compared with that between electrodes 4 and 5. In operation, electrode 4 is charged to a suitable polarizing voltage with respect to electrodes 1 and 5, which are momentarily connected together during this charging process. When the chamber is irradiated thereafter, a charge flows between electrodes 4 and 5, so that a potential difference develops between electrodes 5 and 1. This is directly proportional to the irradiation dose, and is measured directly on an electrometer. To reduce the sensitivity, a similar condenser may be incorporated in insulator 3, and by suitable choice of these capacitances, the roles of electrodes 4 and 5 may be reversed. In the modification of Fig. 2, electrode 4<SP>1</SP> is not adjacent to electrode 1<SP>1</SP>, but spaced therefrom, the sensitive volume now being the space between them, instead of that between electrodes 4 and 5 as in Fig. 1. In Fig. 1, contact to electrodes 4 and 5 is made through removable plugs 6, 7, but in Fig. 2, it is made through spring-loaded plungers 11, 12 sliding in insulating plugs 13, 14 so that no dirt can enter the device.