in 120 



UJ 



a. 



LU 

 CL 



< 



100 



80 



60 



40 



20 



12 



10 



5 

 z 



z 



LU 



tr 

 cr 



D 

 O 



5 

 < 



UJ 

 CD 



(/) 

 LU 



I 



u 



z 



z 



X 



_l 

 LU 



I 



LL 

 O 



I 

 I- 

 15 

 Z 

 UJ 



_l 



1200 

 1/1 



01 



< 1000 



40 60 60 100 120 140 



160 



>- 

 (3 

 ul 



z 



UJ 

 Q 



X 



D 

 _l 

 U. 



u 



I- 

 m 

 z 

 o 

 < 

 5 



800 



600 



400 



200 



40 



60 



80 



100 120 140 160 



MEAN HELIX DIAMETER IN MILS 



Fig. 2 — Alternate designs for the M1789. These curves are an estimate of how 

 the TWT design would be affected by changing the helix diameter. They represent 

 essentially a scaling of the M1789 design. In all cases the expected maximum 

 power output is 12 watts and the low-level gain is 33 db. The line at 90 mils mean 

 diameter in the curves represents the present M1789 design. In these calculations 

 it was assumed that : 



a. 7a = 1.6 



b. power output = 2.1 CIoVo = 12 watts 



c. the magnetic flux density is 2.6 times the Brillouin flux density for a beam 

 entirely filling the helix. 



d. the ratio of wire diameter to pitch is 0.34. 



e. the dielectric loading factor is 0.79. 



f . the ratio of effective beam diameter to mean helix diameter is 0.5. 



1289 



