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Accelerator Report: HL-LHC Alternatives & First Ideas in Progress

Explore innovative solutions like the 8b+4e scheme for potential 25.ns-like backup in HL-LHC, with a focus on 200MHz cavities to address electron cloud issues and enhance performance.

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Accelerator Report: HL-LHC Alternatives & First Ideas in Progress

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  1. US2: HL-LHC alternatives – first ideas (under construction) R. Tomàs, O. Dominguez, S. White Reported by G. Arduini Thanks to P. Baudrenghien, H. Bartosik, O. Bruning, X. Buffat, R. Calaga, E. Shaposhnikova, H. Damerau, S. Fartoukh, R. Garoby, R. de Maria, V. Litvinenkoand G. Rumolo

  2. 8b+4e scheme as a possible 25 ns-like back-up in case of e-cloud issues 12-25 ns slots (4 empty) X 6 = 48 bunches out of 72 25ns slots • Double splitting instead of triple splitting in the PS for 3/2 bunch charge and 2/3 bunches (H. Damerau): • Inject 4+2 bunches in h=7 (as usual). • Double splitting from h=7 directly to h=21, consequently leaving every third bucket empty. Filling pattern: 6*(2b+1e). • Quadruple splitting of each bunch in 4 as usual. The empty bucket is virtually also split in 4. Final filling pattern: 6*(8b+4e). • Filling scheme to be finalized. Tentatively 1832 bunches or more

  3. 8b+4e scheme as a possible 25 ns-like back-up in case of e-cloud issues Merit: Significantly lower e-cloud, no cost

  4. Performance (preliminary) This could also be beneficial for earlier stages if electron cloud is an issue To be compared with 50 ns case (Verena)

  5. SC 200 MHz cavities in the LHC • Motivation: • One of the main limitations for the bunch population in the SPS is related to the maximum longitudinal emittance that can be injected in the LHC. • Installation of 200 MHz cavities in the LHC would allow to accept larger longitudinal emittance and longer bunches: • With 3 MV at 200 MHz in the LHC at injection: bunches with long. emit. of 1.5 eVs, 4 sigma bunch length 3.1 ns and sigma dp/p = 3.6 E-4. • Acceleration with 200/400 MHz needs SC technology. This was initially discarded for beam loading considerations for the 200 MHz copper capture cavities

  6. SC 200 MHz cavities in the LHC • Motivation: • Capture and acceleration of longer bunches will help in reducing the electron cloud effects and possibly IBS, heating • 200 MHz cavities allow additional margin for levelling in the longitudinal plane by varying the bunch length

  7. SC 200 MHz cavities with 400 MHz CC Full crabbing to provide head-on collisions for the core of the beam. Assumed a linear bunch shortening in time from 13-15 cm to 7.5 cm.

  8. Performance (preliminary)

  9. Others to be added (not presented today) • Crab kissing scheme proposed by Stephane • Exotic: • coherent electron cooling to reduce the beam emittance • Electron lens to reduce/compensate beam-beam head on?

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