GB697052A - Improvements in or relating to radiation counter tubes - Google Patents

Abstract

697,052. Geiger counters. PHILIPS ELECTRICAL INDUSTRIES, Ltd. June 20, 1951 [June 23, 1950], No. 14632/51. Class 39(i) A radiation counter tube containing an ionizable gas and an admixture of a halogen is characterized in that the total or a considerable part of the total surface area of the metal parts of the tube in contact with the said mixture consists of chromium sesquioxide. The chromium sesquioxide prevents absorption of the quenching gas and should be provided on electrodes and other metal parts of large surface area, for example the cathode and the transverse partition sometimes contained in counter tubes for hard rays, but may be omitted from the anode when the latter is in the form of a wire or thin rod. In the embodiment shown the cylindrical cathode 1 which may be of copper is provided on the inner surface with a coating 2 of chromium sesquioxide and the anode 3 may also be provided with a similar coating. A window 5 which may be of mica is hermetically sealed to the cathode 1 by a ring 6 formed by melting pulverulent glass. Alternatively, the electrodes may be made of an alloy containing chromium, for example iron and chromium in a weight ratio lying between 1:0.25 and 1:40, and the protective coating obtained by preferential oxidation, or the electrodes may first be chromium plated and at least the surface of the chromium layer then oxidized to chromium sesquioxide. A suitable filling comprises a mixture of neon and/or argon and some tenths of a per cent of chlorine or bromine at a pressure of 10 mm. of mercury.