998 



EXPLORATION GEOPHYSICS 



j£nCk£2^«:"%>-%'4 



B C 



Fig. 610. — Typical thin-wall R-y counters. (A) All glass tube with chemically silvered cathode 

 (wall about .007 inch thick). (Courtesy of Radiation Counter Laboratories.) (B) Aluminum tube 

 with .001-inch wall, cut away to show construction, and (C) mica window tube. (Courtesy of Vic- 

 toreen Instrument Company.) 



COUNTER VOLTAGE 



Fig. 611. — Relationship between pulse height and 

 counter voltage. (After Montgomery and Mont- 

 gomery, ]. Franklin Inst. 231, 447, 1941.) 



relatively large bulk make them 

 less suitable for portable use than 

 for other applications, where their 

 superior sensitivity may be the 

 dominant factor. Almost all port- 

 able detectors novi^ used in the 

 field are Geiger counters. 



The simplest Geiger counter 

 may consist of a Geiger-Miiller 

 tube, a source of high voltage 

 and a pair of earphones. Such a 

 counter is very simple, rugged, and 



