Title :
Optical spectroscopy of plasma and plasma processing in high power microwave pulse shortening experiments
Author :
Cohen, W.E. ; Gilgenbach, R.M. ; Jaynes, R.L. ; Rintamaki, J.I. ; Peters, C.W. ; Lau, Y.Y. ; Spencer, T.A. ; Scheitrum, G.P. ; Laurent, L.L.
Author_Institution :
Michigan Univ., Ann Arbor, MI, USA
Abstract :
Summary form only given, as follows. Spectroscopic measurements have been performed to characterize the undesired plasma in a multi-megawatt coaxial gyrotron. This gyrotron is driven by the Michigan Electron Long Beam Accelerator (MELBA) at parameters: V=-800 kV, I/sub tube/=0.3 kA, and pulselengths of 0.5-1 /spl mu/s. Pulse shortening typically limits the highest (/spl sim/40 MW) microwave power pulselength to 50-100 ns. Potential explanations of pulse shortening are being investigated, particularly plasma production inside the cavity and at the e-beam collector. The source of this plasma is believed to be due to water vapor. Plasma H-/spl alpha/ line radiation has been characterized and correlated with microwave power and microwave cutoff. Experiments are underway to determine the effects of RF plasma processing of the coaxial cavity and collector. A collaborative effort is underway with the Stanford Linear Accelerator Center/U.C. Davis to study RF cavity breakdown. A SEM is being used to examine the surface effects of RF processing cavity parts.
Keywords :
gyrotrons; plasma diagnostics; 0.3 kA; 40 MW; 800 kV; H/sub 2/O vapor; MELBA; Michigan Electron Long Beam Accelerator; RF cavity breakdown; RF processing cavity; coaxial cavity; e-beam collector; high power microwave pulse shortening experiments; microwave cutoff; microwave power; multi-megawatt coaxial gyrotron; optical spectroscopy; plasma; plasma H-/spl alpha/ line radiation; plasma processing; plasma production; pulse shortening; scanning electron microscopy; surface effects; Coaxial components; Electron beams; Electron optics; Gyrotrons; Plasma accelerators; Plasma materials processing; Plasma measurements; Plasma sources; Radio frequency; Spectroscopy;
Conference_Titel :
Plasma Science, 1999. ICOPS '99. IEEE Conference Record - Abstracts. 1999 IEEE International Conference on
Conference_Location :
Monterey, CA, USA
Print_ISBN :
0-7803-5224-6
DOI :
10.1109/PLASMA.1999.829700