Strong transverse coupling in the Tevatron
The Tevatron was designed with an extensive set of correction and adjustment magnets built into the spool pieces in recognition of the circumstance that a superconducting synchrotron was not as easy to modify as its conventional forebearers. Recently, concern has mounted at the high excitation of the skew quadrupole correctors. The purpose of this note is to account for this situation. When slow extraction was attempted from the Main Ring in the summer of 1970 horizontal-vertical coupling prevented adequate transverse oscillation growth for efficient slow spill. This situation was corrected by an 8 mrad roll of each of twelve equi-spaced quadrupoles [1]. In order to avoid a repetition of this problem in the Tevatron, an extremely strong skew quadrupole circuit was built in at the outset. When the Tevatron was commissioned only 4$ of the capability of this circuit was required. Now, 20 years later, the excitation of this skew quadrupole circuit is approximately 60%. Other skew quadrupole correctors were installed in the neighborhood of the long straight sections, and for a variety of reasons the number of elements in the strong circuit was reduced from 48 to 42. These are relatively minor changes in the present context. Recall that in the normal Tevatron tuning process the skew quad circuits are adjusted to minimize the difference between the horizontal and vertical tunes to the level of {Delta}{nu}{sub min} {approx} 0.003. Normally the horizontal-vertical coupling is not observed directly by orbit measurements during this procedure. it was recognized that the strength of the skew quadrupole settings would imply an uncorrected minimum tune difference of 0.2 units. Clearly, with the skew quad circuit turned off the coupling of the orbital motion should be easily observable. In the following sections, the authors describe the recent Tevatron studies that exhibit the transverse coupling and the analyses that link these observations to the long term development of a skew quadrupole coefficient in the Tevatron dipoles. In brief, their conclusion is that a{sub 1} at the level of one of the traditional units will account for the coupling and is consistent with physical examination of a selection of dipoles in the tunnel.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76CH03000
- OSTI ID:
- 15017292
- Report Number(s):
- FERMILAB-BEAMS-DOC-501 FERMILAB-EXP-203; TRN: US0604911
- Country of Publication:
- United States
- Language:
- English
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