Lanterna Rally

Author: William Freer Bale

Publisher:

Published: 1949

Total Pages: 20

ISBN-13:

This instrument is designed for the detection and measurement of a group of ionizing radiations. Interchangeable ionization chambers have been constructed for the measurement of (1) beta and gamma radiations, (2) surface and hand monitoring of alpha radiations, (3) alpha and beta radiation of dust samples collected in precipitron tubes, and (4) fast neutrons. Moderate to high radiation intensities are measured by direct continuous deflection of a microammeter indicating changes in plate current of a 1LN5 tube used as an electrometer tube. Low intensities of radiation are measured by allowing the charge due to the ionization current to collect on one plate of a condenser. The other plate connects to the grid of the electrometer tube and to ground through a high resistance. During the period of charge collection the two condenser plates are electrically shielded from one another by a grounded metal vane inserted between them. On removing this vane the charge on the first plate of the condenser is communicated to the second plate and thus to the tube grid. A transient meter deflection then occurs proportional to the product of ionization current and ion collection time. A two pole, triple throw switch allows the output meter to be connected in test 1 position to measure screen grid current, in test 2 position to set tube voltages to reproducible values, and in "Operate" position to measure changes in plate current.