330 



ISOTOPIC TRACERS AND NUCLEAR RADIATIONS [Chap. 10 



V2 



f-AA/V-*— AAAr^ ' 



O— * 

 INPUT 



OUTPUT 



NEG. 



PULSE 



Fig. 83. Scale of two-trigger circuit. The two units of IT form a trigger circuit delivering 

 alternately a positive and negative pulse. Negative pulses are clipped by V3, thus passing 

 one pulse for every two at the input. Scales of 4, 8, 16, 32, etc., are obtained by adding 

 identical units in series. The neon tube V2 serves as an indicator to extrapolate between 

 multiples of the scale factor. Approximate circuit values are 



121, R6 = 400,000 ohms VI = 6N7, 6SL7 or pairs of single triads 



R2, R5 = 500,000 ohms VI = neon, \i watt 



R3, RA = 40,000 ohms V3 = 6C5 or similar triode 



CI, CI =40 MMfd 



-If 



C4 



OUTPUT 

 O 



P3 



R4 



B + 



POS. 

 PULSE 



Fig. 84. Thyratron scale of two circuit. Higher scale factors are obtained with additional 

 units in series. Approximate circuit values are 121, R2 = 50,000 ohms; R3, R4 = 20,000 

 ohms; CI, C2, C3, C4 = 0.002 M f d ; VI, V2 = Thyratron, e.g., 884. 



