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Title |
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| MOPLT120 |
Proposals for Improvements of the Correction of Sextupole Dynamic Effects in the Tevatron Dipole Magnets
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818 |
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- P. Bauer, G. Ambrosio, J. Annala, J. DiMarco, R. Hanft, M. Lamm, M. Martens, P. Schlabach, D. Still, M. Tartaglia, J. Tompkins, G. Velev
Fermilab, Batavia, Illinois
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It is well known that the sextupole (b2) components in the superconducting dipole magnets decay during the injection plateau and snap back rapidly at the start of the ramp to flat top current. These so-called dynamic effects were originally discovered in the Tevatron. They are compensated for by the chromaticity correctors distributed around the ring. Imperfect control of the chromaticity during the snapback can contribute to beam loss and emittance growth. A thorough investigation of the chromaticity correction in the Tevatron was launched in the context of Run II, including beam chromaticity measurements and extensive magnetic measurements on a series of spare Tevatron dipole magnets. The study has yielded new information about the effect of the powering history on the dynamic b2. A companion paper at this conference describes in detail the results of these magnetic measurements [reference to George Velev's paper]. Study findings have given directive to new proposals for improvement of the b2 snapback correction in the Tevatron, including a revised functional form for the snapback algorithm and the elimination of the beam-less pre-cycle. This paper reports the results of beam studies performed recently to test these improved procedures.
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| WEPKF009 |
A Scaling Law for Predicting Snap-back in Superconducting Accelerator Magnets
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1609 |
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- T. Pieloni, L. Bottura, S. Sanfilippo
CERN, Geneva
- G. Ambrosio, P. Bauer
Fermilab, Batavia, Illinois
- M. Haverkamp
METROLAB, Plan-les-Ouates
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The decay of the sextupole component in the bending dipoles during injection and the subsequent snap-back at particle acceleration are issues of common concern, albeit at different levels of criticality, for all superconducting colliders built (Tevatron, HERA, RHIC) or in construction (LHC) to date. The main difficulty is the correction of the relatively large and fast sextupole change during snap-back. Motivated by the above considerations, we have conducted an extended study of sextupole snap-back on two different magnet families, the Tevatron and the LHC bending dipoles, using the same measurement method. We show in this paper that it is possible to generalise all the results obtained by using a simple, exponential scaling law. Furthermore, we show that for magnets of the same family the parameters of the scaling law correlate linearly. This finding could be exploited during accelerator operation to produce accurate forecast of the snap-back correction based solely on beam-based measurements.
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