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Interleaved Filling Possibilities

Interleaved Filling Possibilities. Interleaved Filling Possibilities V. Kain , K. Cornelis, J. Wenninger. Introduction Filling the LHC – nominal concept How will we do it? What is the problem? Cycles for next year Summary. Introduction – Filling the LHC (SPS point of view).

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Interleaved Filling Possibilities

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  1. Interleaved Filling Possibilities Interleaved Filling Possibilities V. Kain, K. Cornelis, J. Wenninger • Introduction • Filling the LHC – nominal concept • How will we do it? • What is the problem? • Cycles for next year • Summary Oct 9, 2007

  2. Introduction – Filling the LHC (SPS point of view) • 2 different SPS extraction for the 2 LHC rings: • LSS6 → TI 2 → beam 1 • LSS4 → TI 8 → beam 2 • Nominal filling: 12 injections per ring • Can we fill the LHC in an interleaved way? Oct 9, 2007

  3. YES… Can we do it easily, efficiently…? Oct 9, 2007

  4. Introduction - SPS extractions • Large horizontal bump (> 35 mm) • Fast extraction kickers (~ 50 kV in LSS4, ~ 30 kV in LSS6) • Extraction septa Example: LSS4 Oct 9, 2007

  5. Filling the LHC – Ideal World - Nominal Concept • The plan (and reality) is • The Central Timing System controls the production of the LHC beams in the Injector chain via the CBCM (Central Beam and Cycle Manager) • Beams are associated with “users” in the different accelerators to define the magnetic cycles and destinations • Static destinations/ dynamic destinations • E.g.: LHC beam: static destination: SPS dump, dynamic destination: set on the fly (TI 8 dump, TI 2 dump, TI 8/LHC2, TI 2/ LHC1) • Destinations: TI 8/ LHC2, TI 2/LHC1 can only be set by the LHC sequencer • Sequencer requests: beam type (number of batches), target RF bucket, ring • Hence the required supercycles in the SPS • Supercycle: LHC nominal (~ 20 s) • Supercycle: FT + 3 CNGS + pilot (~ 43 s) • Supercycle: pilot (~ 8 s) Oct 9, 2007

  6. But…we can’t do it like this yet… • The SPS power converter control (mugef) is run by the ROCS software • The mugefs do not “understand” destination • The extraction kickers understand destination • Could always pulse both lines plus both extractions….and same scenario as before  expensive • safety issue: the bumps in the SPS • in case of problems during extraction (kicker problems,…) risk to damage both extraction channels • The ROCS system will go FESA or something similar one day • …but not for next year!!!!!!!! Oct 9, 2007

  7. How will we do it? How did we do it? • Instead of one LHC user per SPS supercycle and two destinations… • 2 LHC users per SPS supercycle (with different destinations) • = two LHC cycles per SPS supercycle Example: this year’s interleaved extractions to TT40 and TT60: 2 LHC pilot cycles in the SPS supercycle. 2 users, one for LSS4, one for LSS6. Each transfer line pulsed only once per SC. Total length: 16.8 s Oct 9, 2007

  8. So, what is the problem? (1) • Same supercycle, filling only one ring, takes 2 x as long… • Could be overcome by changing supercycle in case: Example: supercycle for interleaved nominal filling. Total length: 43.2 s SFTPRO + pilot Etc. LHC nominal Pilot interleaved Oct 9, 2007

  9. So, what is the problem? (2) • All supercycles have to be ready • The timing sequences need to be prepared as well (also for different beam types) • To be really efficient: all supercycles should be resident in the hardware • BUT…. • there are not enough users • 24 • already three for CNGS, three for coast, pstart/pstop, SFTPRO,… • the ROCS do not have enough memory • Change supercyle if cycles resident: • 1 – 2 minutes • Change supercycle if cycles not resident: • up to half an hour Oct 9, 2007

  10. Cycles for next year… • For next year we can live with the current situation • Always resident: • Supercycle: FT + 3 CNGS + LHC pilot (length ~ 43 s )…or similar • parallel MD cycle ?!?!? • Supercycle: LHC pilot(length ~ 8 s) • fine for single injections from PS: pilot, one bunch, 4 bunches, 12 bunches, 48 bunches, 72 bunches • Low intensity (up to 12 bunches) interleaved: both lines + bumps pulsing • Other cycles which will be there, but (probably) not resident: • Supercycle: LHC nominal • Supercycle: LHC nominal + LHC nominal Oct 9, 2007

  11. Prospect and proposal • ROCS will migrate in shutdown 2008/2009 • next generation software will understand destination • We would like to have more users 24 + > 8 • despite memory limitation in the ROCS • Clean up the functions for the corrector magnets Oct 9, 2007

  12. Solution for next year… About 1.3 x 1013 protons per extraction Oct 9, 2007

  13. Summary • We can fill the LHC in an interleaved way. • Current limitations for efficient and flexible filling of the LHC: • SPS mugefs (mainly the extraction bumpers) • Solution: • Migration of ROCS to FESA or similar (will come) • More users, at least 8 more Oct 9, 2007

  14. Additional complexity – no showstopper • LSS4: LHC and CNGS extraction • MBIs: main dipole chain in TI 8/ CNGS…same power converter • Electronic switch: current below 1 % of nominal during beam out • Same thing for the MBSG (switch magnet between CNGS and TI 8) • Separate beam transfer needs to be defined for TT40 • Otherwise cannot have CNGS and LHCbeam 2 transfer in the same supercycle • CTIMs to be managed by LSA Oct 9, 2007

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