Accession Number:

AD0262440

Title:

ELECTRONIC EQUILIBRIUM IN FREE-AIR CHAMBERS AND A PROPOSED NEW CHAMBER DESIGN

Descriptive Note:

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s):

Report Date:

1961-08-03

Pagination or Media Count:

27.0

Abstract:

A new type of free-air ionization chamber is proposed in which electric-field uniformity plays no role in defining the ion-collecting volume. The chamber is based essentially upon a subtraction method in which two readings are taken of the ionization and the difference is used as a measure of exposure dose. The chamber is collapsible, its midplane being fixed with respect to the x-ray source. The ionization in the two equal air volumes on either side of the midplane of the chamber when in a collapsed condition and the ionization of the two volumes defined by the chamber in an expanded condition are related in such a way that their difference is just the ionization in the extra volume of air created in the middle of the chamber by the expansion of the chamber. It is evident that the end planes of this extra volume of air are not defined by electrostatic lines of force, as is the case for conventional chambers. Consequently, the new chamber has no need for guard plates or other field- shaping electrodes which are typical of conventional free-air chambers. Since the uncertainty about the degree of field uniformity represents the largest single source of error in conventional chambers, its elimination is a considerable advantage.

Subject Categories:

  • Test Facilities, Equipment and Methods

Distribution Statement:

APPROVED FOR PUBLIC RELEASE