REFLEX OSCILLATORS • 679 



Then -"^Jl = l(KT' - Po) ~ fk8) 



at C 



or ^' = -^ TtiTt - 1). (k9) 



Here T, = ^ and Po = KTo (klO) 



To 



where Po is the power from other sources than direct bombardment. In 

 this case T, is always greater than 1. 

 Integration yields 



C 



IKTi 



[tan"' Ts + ctnh"' T,] ^ t -^ k . (kll) 



Let FoXTs) = [tan"'r. + ctnh~Y,]. (kl2) 



This function is plotted in Fig. 80. To determine the cycling time for 

 cooling assume 



(kl3) 



giving the time for the contracting element to cool from temperature Tsk 

 to Tsc', i.e. from T;, to Tr . 



(2) Conduction Cooling 

 The rate of change of temperature on heating will be given by 



where 



T is the temperature difference between the tuning strut and the 



heat sink. 

 C is the heat capacity of the strut. 

 k is the conduction loss in watts/°C. 

 Pi is the power into the tuner. 



The solution of (kl4) is then, 



P 



k 



(^-) 



P<-T = (^- To]e-^"''' (kl5) 



