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Coherent betatron instability in the Tevatron [electronic resource].

Published
Batavia, Ill. : Fermi National Accelerator Laboratory, 1988.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description
Pages: 4 : digital, PDF file
Additional Creators
Fermi National Accelerator Laboratory and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
The coherent betatron instability was first observed during the recent 1987-88 Tevatron fixed target run. In this operating mode 1000 consecutive bunches are loaded into the machine at 150 GeV with a bunch spacing of 18.8 /times/ 10/sup -9/ sec (53 MHz). The normalized transverse emittance is typically 15 ..pi.. /times/ 10/sup -6/ m rad in each plane with a longitudinal emittance of about 1.5 eV-sec. The beam is accelerated to 800 GeV in 13 sec. and then it is resonantly extracted during a 23 sec flat top. As the run progressed the bunch intensities were increased until at about 1.4 /times/ 10/sup 10/ppb (protons per bunch) we experienced the onset of a coherent horizontal oscillation taking place in the later stages of the acceleration cycle (>600 GeV). This rapidly developing coherent instability results in a significant emittance growth, which limits machine performance and in a catastrophic scenario it even prevents extraction of the beam. In this paper we will present a simple analytic description of the observed instability. We will show that a combination of a resistive wall coupled bunch effect and a single bunch slow head-tail instability is consistent with the above observations. Finally, a systematic numerical analysis of our model (growth-time vs chromaticity plots) points to the existence of the greater than or equal to1 slow head-tail modes as a plausible mechanism for the observed coherent instability. This last claim, as mentioned before, does not have conclusive experimental evidence, although it is based on a very good agreement between the measured values of the instability growth-time and the ones calculated on the basis of our model. 4 refs., 3 figs.
Report Numbers
E 1.99:fnal/c-88/69
E 1.99: conf-880695-10
conf-880695-10
fnal/c-88/69
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Note
Published through SciTech Connect.
06/09/1988.
"fnal/c-88/69"
" conf-880695-10"
"DE88012677"
1. European particle accelerator conference, Rome, Italy, 7 Jun 1988.
Harrison, M.; Ng, K.Y.; Bogacz, S.A.
Funding Information
AC02-76CH03000
View MARC record | catkey: 14696857