Wilson Cloud Chambers with an Increased Time of Sensitivity

Abstract

Two types of sylphon bellows Wilson cloud chambers have been constructed which have a time of sensitivity as great as 2.0 seconds. This has been accomplished by using a slow rate of expansion and an expanding space whose floor was water. The mechanical details have been made exceedingly simple and such that once the cloud chamber is adjusted it easily remains in adjustment indefinitely. About four to five cosmic‐ray tracks appear for each expansion. A test with x‐rays showed that the cloud chambers were sensitive for about 2 seconds under the best conditions. Some of the principal requirements for successful operation are listed. Also motion pictures of an expansion are reproduced. Several observations concerning the high voltage condenser—capillary tube method of illumination are given.