ELECTRON LIFETIME DETECTOR FOR LIQUID ARGON

A method has been developed for a fast and reproducible measurement of the electronegative contamination of liquid argon. The method is based on the transport of electrons extracted by a NdYag UV laser beam from a metallic photocathode. The transit time of the electrons from the emitting surface to a collecting plate depends on the applied electric field and ranges from a few tens of microseconds to milliseconds. The measurement of the purity is based on the ratio of collected to emitted charges. The operation can be performed in a few minutes and gives values of the electron lifetime with a typical error of a few percent. Filling and emptying the vessel can be done in less than an hour. © 1990.