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Harmonics for the LHC Pre-Accelerators PSB, PS, SPS

Harmonics for the LHC Pre-Accelerators PSB, PS, SPS. The goal of LIU is to optimize the performance of the LHC pre-accelerators in view of the HLHC upgrade. This requires to get brighter beams, i.e. more intensity with equal or smaller emittances.

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Harmonics for the LHC Pre-Accelerators PSB, PS, SPS

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  1. Harmonics for the LHC Pre-Accelerators PSB, PS, SPS • The goal of LIU is to optimize the performance of the LHC pre-accelerators in view of the HLHC upgrade. • This requires to get brighter beams, i.e. more intensity with equal or smaller emittances. • An essential limitation is the space charge limit. • On the other hand the interplay between space charge and the nonlinearities seems to be the limiting process. • We are presently developing codes to treat both effects simultaneously. • Equally relevant are machine experiments to benchmark the simulations, directly measure and eventually correct resonances. • Ideally we would need good knowledge of the harmonics. • Can the magnet experts and help in the framework of Fidel? Fidel 03.07.2012

  2. The machines – PSB (Christian) • Reference magnets without vacuum chambers  change of fields • Spares are available Quad/Dipoles • Little is known about the harmonics other than b1 & b2. (A b4 component expected in the dipoles???) • There is a rather sizable skew sextupole (a3) component. This has been successfully measured and corrected with a driving term analysis.  Peter Urschűtz thesis • During LS1 3 close-by H&V pickups will be prepared for 1000 Turn measurements and the damper kicker will be used as a AC-dipole for continuous excitations. • Intense space charge measurements in progress. Fidel 03.07.2012

  3. The machines – PS (Simone) • An effort has been done to understand the harmonics of the dipole magnets (including pole windings). I understand that harmonics have been modeled till b4 (I would have liked b5 to understand Q’’’!). The expert is with you now. • There are reference magnets recently upgraded with fixed coils (b4/b5 can be measured) • There are a few spares for measurements. • Automated (local!) driving term measurements are being prepared with 1000T BPM system and kickers available. • Systematic space charge measurements in conjunction with linear and nonlinear resonances under way in collaboration with GSI experts. Fidel 03.07.2012

  4. The machines – SPS (Hannes) • 2 reference magnets (MBA & MBB) and spares available. • Problems with vacuum grounding and eddy currents. • b3/b5 in body and the edges, fringe fields? • NL chromaticity (Q’, (Q’’), Q’’’)  effective model of b5 in MBA, MBB. • Supercycle dependent and year-by-year changes (grounding, aging, hysteresis???) • Both driving-term and space charge measurements in progress. • Modeling possible for the dipoles, in particular b5? • Quads (small b4) model as well. • Q20 is more sensitive to multipoles (Q’/Q’’’ larger for same b3/b5). Fidel 03.07.2012

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