Compact multibeam klystron

Abstract

High power k l y s t r o n s o p e r a t i n g i n t h e 300-600 MHz frequency range, used i n s c i e n c e f o r p a r t i c l e acc e l e r a t o r s , h a v e t h e drawback of being bulky and requiring very high voltages. Since klystron dimensions grow f a r less r a p i d l y t h a n t h e power they can deliver, one could propose to employ tubes of 4 to 5 K W each when t o t a l power requirements are of s e v e r a l t e n s of M W . But a more compact and f l e x i b l e s o l u t i o n i s o f f e r e d i n t h e f o r m of t h e multi-beam klystron (MBK), an N-beam t u b e t h a t s t i l l uses 4 o r 5 c a v i t i e s . Such an MEK would g r a n t a r e d u c t i o n i n b o t h w e i g h t and high voltages used. I n the frequency range of 300-600 MHz, k l y s t r o n s are generally developed and manufactured for high energy physics and more s p e c i f i c a l l y f o r e l e c t r o n synchrotron or storage rings, although such klystrons are beginning to be considered for proton vices. The TH 2089 (352 MHz 1.2 MW CW) and the l i n e a r a c c e l e r a t o r s and powerful n e u t r a l beam de-TH 2105 (508 MHz l MW CW) are two examples of such tubes and 4 t o 5 MW CW u n i t s are a l s o f e a s i b l e [I], a s proved, for instance, by t h e 500 k W (CW) obtained a t 3.7 GHz on t h e TH 2103 [2]. The good agreement between the calculated predict i o n s and t h e r e s u l t s from on-field devices i s due not only to the use of i n c r e a s i n g l y a c c u r a t e mod e l s , b u t a l s o f r o m a b e t t e r t e c h n i c a l mastery, p a r t i c u l a r l y a s r e g a r d s s p e c i a l p r o c e s s e s d u r i n g bake-in and voltage and power rise. E f f i c i e n c y i s an important parameter for such t u b e s b u t t h e r e h a s t o be a trade-off between high e f f i c i e n c i e s and cathode voltages, which results i n t h e c h o i c e of modest perveance values, typicall y around 0.7 Irperv. On t h e TH 2089 and TH 2105, the cathode voltages are 80-90 kV DC and t h e e f f iciency is c u r r e n t l y 67-68 % w i t h some tubes a t t a i n i n g 70 %. Extremely high DC v o l t a g e s are t o be avoided for many r e a s o n s , i n c l u d i n g : t h e c o s t and bulk of power supplies and cables which vary e x p o n e n t i a l l y w i t h v o l t a g e , i n t e r n a l a n d e x t e r n a l breakdowns, aggravated by i n e v i t a b l e r e s o n a n c e s i n t h e e x t e r n a l c i r c u i t s and d i f f i c u l t i e s i n p r o t e ct i n g t h e t u b e (crow-bar systems) and the associat e d m i c r o c i r c u i t s . C o n c e r n i n g t h e s i z e , t h e h i g h v o l t a g e V has a maj o r i n f l u e n c e , i n a d d i t i o n t o f r e q u e n c y , which e x p l a i n s the large dimensions of the tubes. The s e p a r a t i o n of t h e p o l e p i e c e s t o w i t h i n t h e nearest v a r i a t i o n s i n plasma wavelength due t o t h e beam's diameter and perveance, i s e q u a l t o -evo and i s t h u s p r o p o r t i o n a l t o V i and ...

A Model for Human Tooth Enamel Central Dark Line its Hrtem Images Contrast Transfer Function Analysis

“…When the enamel crystallites are observed with the transmission electron microscope (TEM), they exhibit a line of 1 to 1.5 nm wide along their centers [1,2]. This line has been named "dark line", although in reality its contrast is focus dependent: it appears dark in underfocus, disappears when the image goes through focus, and is white in overfocus.…”