Multipactor saturation due to space-charge-induced debunching
- Science Applications International Corporation, McLean, Virginia 22102 (United States)
As the multipactor charge builds up, the mutual repulsion overtakes the focusing effect of the rf interaction, and the thin charge ribbon formed during the initial buildup expands into a wide band. Two synergistic effects lead to saturation (a) first, spreading of the impact phases into the region where the vacuum rf retards emission (b) later, and field reversal in the front end of the bunch due to the space-charge field, regardless of the rf phase. The effective secondary yield under opposing field is zero regardless of impact energy. Steady state is achieved when the ensemble-average yield {delta} drops to unity. The spreads in the impact energy are less important; impacts under reversed field cause saturation even at constant (independent of impact energy) secondary yield. The bunch breakup threshold is identified from bunch stability theory. It is found that near saturation both one-surface and two-surface cascades take place simultaneously; particle orbits alternate between one- and two-surface multipactors until they are finally lost to unfavorable phase/reversed field impacts. The possibility of saturation with a tight bunch, before breakup, is also discussed. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 544574
- Journal Information:
- Physics of Plasmas, Vol. 4, Issue 5; Other Information: PBD: May 1997
- Country of Publication:
- United States
- Language:
- English
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