SCIENTIFIC OFFENSIVE 



to be read, the badge is placed in photographic develop- 

 ing solution, and the emulsion becomes darkened. The 

 degree of darkening indicates the total amount of 

 gamma radiation which struck the badge. Such badges 

 were among the simplest and most reliable of all gages 

 used at Bikini. Thousands were used for each of the 

 two explosions. They were placed at innumerable posi- 

 tions topside on target vessels, below decks, and in the 

 same compartments where test animals w^ere sta- 

 tioned.* 



Geiger counters were to be used to find the intensity 

 of gamma radiation at any one moment. These count- 

 ers are especially useful because they produce their 

 answers at once — either by motion of a needle across 

 a dial, or by producing a machine-gun noise in head- 

 phones. The marvel of the Geiger counter is that it can 

 detect a single pJioton, or unit of gamma radiation. 

 Heart of the counter is a crude electron tube, contain- 

 ing a central wire and a small quantity of gas; the 

 wire is at critically high voltage, such that the slightest 

 disturbance — even the slight disturbance produced by 

 arrival of a single photon of gamma radiation — com- 

 pletely upsets the electrostatic regime and causes a 

 violent discharge of current. Equilibrium is restored 



* Much operational use was made of such badges. They were 

 carried continuously by persons working in contaminated areas 

 where unsuspectedly large dosages of gamma radiation might be 

 acquired. By developing and analyzing the badges, reliable an- 

 swers could be found as to whether or not over-exposure had oc- 

 curred. Fortunately, the answers were always in the negative. 



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