SPARK GAP SWITCHES FOR RADAR 



601 



titles. For instance, one of these products would prevent the use of very 

 high peak currents along with very long pulses, a combination which would 

 give a very short life, especially with aluminum cathode gaps. Or another 

 product would prevent the use of the tube at both high peak currents and 

 high repetition rates, a condition which would not allow adequate de- 

 ionization between pulses. The later types of gaps were rated in this man- 

 ner. 



(g) Evaluation of the Fixed Gap as a Modulator Sivitch 



In order to compare the performance of fixed gaps in radar modulators 

 w^ith that of other switching devices, as well as to assess their future pos- 

 sibilities, we may consider them with respect to the following points. 



Table I 

 Ratings of W. E. Fixed Spark Gap Tubes 



(More complete information on the above tubes is contained in the JAN Specifications 

 for individual tubes.) 



1) Peak current— The present coded tubes cover a range of currents 

 from 20 amperes to 300 amperes. E.xperimental tubes have been 

 tested up to 1000 amperes, and indications are that even larger cur- 

 rents are possible. 



2) Switch voltage — The present tubes cover a range from 2.6 to 17.1 

 kilovolts. Experimental tubes have been tested up to 30 kilovolts. 



3) Peak power output— W\\h the limits of peak currents and voltages on 

 the present tubes, power outputs of 25 kilowatts to 2,2 megawatts 

 are possible. Experimental tubes were made which were capable of 

 furnishing 15 megawatts. Much larger power outputs seem possible. 



4) Pulse duration — The maximum range of pulse durations covered by 

 any of the present tubes is from 0.25 to 6 microseconds. For pulses 

 shorter than 0.25 microseconds the elficiency of these tubes would 

 decrease rapidly. Pulse durations much greater than 6 microseconds, 

 however, could probably be used if proper attention is given to cooling. 



