RF properties of periodic accelerating structures for linear colliders [report]

J.W. Wang
1989 unpublished
Stanford University, 1989 ~ _ _ With the advent of the SLAC electron-positron linear collider (SLC) in the 100 GeV center-of-mass energy range, research and development work on even higher energy machines of this type has started in several laboratories in the United States, Europe, the Soviet Union and Japan. These linear colliders appear to provide the only promising approach to studying e+e-physics at center-ofmass energies approaching 1 TeV. This thesis concerns itself with the study of
more » ... th the study of radio frequency properties of periodic accelerating structures for linear colliders and their interaction with bunched beams. The topics that have been investigated are: l Experimental measurements of the energy loss of single bunches to longitudinal modes in two types of structures, using an equivalent signal on a coaxial wire to simulate the beam. l A method of cancelling the energy spread created within a single bunch by longitudinal wakefields, through appropriate shaping of the longitudinal charge distribution of the bunch. l Derivation of the complete transient beam-loading equation for a train of bunches passing through a constant-gradient accelerator section, with application to the calculation and minimization of multi-bunch energy spread. l Detailed study of field emission and radio frequency breakdown in diskloaded structures at S-, C-and X-band frequencies under extremely highgradient conditions, with special attention to thermal effects, radiation, sparking, emission of gases, surface damage through explosive emission and its possible control through RF-gas processing. ii ACKNOWLEDGEMENTS My heartfelt gratitude must first go to my advisor, Professor G. A. Loew, for taking me as his student, for his countless hours of help and advice, and for his continuous encouragement and guidance throughout my years at SLAC. I have been very fortunate to have-had the-opportunity to benefit frm his extensive knowledge--and broad experience in the field of accelerator physics, and to be stimulated by his great enthusiasm for science. I extend my warm thanks to Professor R. H. Miller who can provide surprisingly lucid explanations to complex problems, and who was on my reading committee; to Professor P. B. Wilson who always stops his work to answer my questions; to my Professor in China, Naichuan Liu, who first encouraged me to study accelerator physics. Over the past several years during our RF breakdown studies at SLAC, I have been assisted by many people in various phases of the work. J. Zamzow helped with all the high-power waveguide installations, the vacuum system, and the gas exposure tests. H. Deruyter gave his assistance in many of the RF cold tests. P. Corredoura set up the VAX-785 computer interface system to digitize and record the breakdown pulses. H. Hoag led the mechanical design and construction of the recent 11.42 GHz traveling-wave section. E. Hoyt helped with many useful discussions regarding surface damage, gas exposures, and provided the scanning electron microscope pictures. V. Nguyen-Tuong, while visiting SLAC, was the prime mover in the early tests involving argon processing. R. Ecken and G. Aske were helpful in improving the operation of the test stand and C. Griffin managed to "squeeze" 47 MW out of an old 36 MW XK-5 klystron. Ipe helped with the radiation and beam energy calculations and measurements, and Professor K. L. Brown with beam transport calculations. I appreciate very useful overall discussions
doi:10.2172/5843664 fatcat:7gdvuekcs5eyrgnfdqg3axethi