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Analysis of the B2 Correction in the Tevatron

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Michael A. Martens
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Michael A. Martens
Document Created:
07 Mar 2003, 17:46
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07 Mar 2003, 17:46
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07 Mar 2003, 17:47
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Beam loss and emittance dilution during ramping from injection to collision energy is observed in the Tevatron, now in its collider run-II stage. This phenomenon is believed to be related mostly to beam instabilities. There has been, however, repeated expression of concern that imperfect control of the machine chromaticity during the injection porch and the ensuing ramp to collision could also contribute to the beam loss. It is well known that the magnetic multipoles and most importantly the sextupole component in the superconducting dipole magnets in the Tevatron decay during the injection plateau and snap back to the value before the start of the decay at the start of the ramp. Sextupole correctors distributed around the ring are used to counteract the sextupole decay in the main magnets. To determine if the sextupole compensation is working successfully in the Tevatron a thorough investigation of the Tevatron chromaticity settings and corrections was conducted and compared to the results of magnetic measurements performed on magnets. The following reports on the results of this investigation, showing that the sextupole decay and snapback are compensated to within a fraction of a unit with the current Tevatron chromaticity correction scheme. Although some minor, possible improvements are discussed, this note supports the status quo as no basic inconsistency was found in the Tevatron sextupole correction scheme. These findings were also confirmed by chromaticity measurements performed on the beam, which are reported in this note.
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