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Filling Schemes for the 2010 Heavy Ion Run

Filling Schemes for the 2010 Heavy Ion Run. Updated version of the LHC-BCWG talk on 18 th September taking Jörg’s comment into account. Content: Introduction Limitations on Injection Kicker Timings to keep Abort Gap Original 62 bunches/ring EARLY scheme

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Filling Schemes for the 2010 Heavy Ion Run

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  1. Filling Schemes for the 2010 Heavy Ion Run Updated version of the LHC-BCWG talk on 18th September taking Jörg’s comment into account Content: Introduction Limitations on Injection Kicker Timings to keep Abort Gap Original 62 bunches/ring EARLY scheme A 60 bunches/ring variant of the original scheme respecting kicker restrictions The 140 bunches/ring scheme presented on 28th September (minimum spacing 500 ns) A 128 bunches/ring variant (of the 140 bunches scheme) respecting kicker restrictions The 124 bunches/ring scheme presented on 28th September (minimum spacing 600 ns) Summary and Conclusions: Revision of the original EARLY scheme and adaptations to increase Luminosity … Higher lumi with more bunches increase (minimum) filling time to ~7 mins/ring Which scheme to be used … may-be further variant to be studied? (Is injection kicker timing limitation (to keep abort gap) required for ions?) Discuss with relevant SPS and LHC (RF, BI, machine protection …?) experts October 2010 Filling Schemes proposed for the 2010 Ion Run C.Carli and J.Jowett 1/10

  2. Introduction • EARLY scheme adopted in 2003 for the first ion run(s): • Luminosity 5×1025 cm-2 s-1 (instead of NOMINAL 1027 cm-2 s-1) • Running conditions (b*=3.5 m instead of 1.0 m and half the design energy): • Further drop of the luminosity to ~0.7×1025 cm-2 s-1 • Compensate partly by increasing (roughly doubling for the schemes presented here) the number of bunches • “Only” adaptation of the EARLY scheme • No variants of the NOMINAL scheme proposed … keep it simple • Transparent for Linac3, LEIR and PS (one LHC ion bunch per cycle) • SPS accumulates four PS transfers … keep SPS magnetic cycle • Decrease distance between bunches in SPS (some change for RF, timings) to create space • Increase number of SPS cycles to fill one LHC ring …. and, thus, the LHC filling time to a minimum of ~7 min/ring • All three experiments (ALICE, CMS and ATLAS) taking ion data request non-colliding bunches • Restrictions on possible injection kicker timings to keep abort gap free taken into account (see comment by Jörg in the LHC-BCWG on 28th September) • … can this limitation be removed for ions (lower intensities, stored energy …)? October 2010 Filling Schemes proposed for the 2010 Ion Run C.Carli and J.Jowett 2/10

  3. Limitations on Injection Kicker Timings to keep Abort Gap 1st bunch of last batch bucket 31 101 o.k, bucket 31 201 not o.k. 1st bunch of 1st batch in bucket 1 Dump Kicker 3.0 ms Injection kicker 7.8 ms fixed w.r.t. 1st bunch of batch time or bunch position Minimum distance between 1st bunches of last and first batch between 11 225 ns and 11 350 ns • Issue raised by J. Wenninger at the LHC-BCWG on 18th September 2010 with detailed explanations by B. Goddard • Aim: make sure that the abort gap cannot be filled accidentally by restricting injection kicker timings • LHC injection kickers possibly filling the abort gap are not allowed • Implies minimum distance between first bunch of last batch and first bunch of first batch …value between 11 225 ns and 11 350 ns (precise value could be found if needed) • No restriction for LHC filling with typical proton bunch trains (SPS accumulates 4 PS batches) • A limitation with short ion bunch trains as envisaged for the “EARLY” ion scheme October 2010 Filling Schemes proposed for the 2010 Ion Run C.Carli and J.Jowett 3/10

  4. Original 62 bunches/ring EARLY schemeFilling scheme and pattern 62 bunch/ring EARLY by R.Bailey and P.Collier (as I understood it from LHC project Note 323) • Filling scheme formula taken from Note - First SPS to LHC transfer with two bunches (?) - All further batches with 4 bunches • Last batch cannot be injected with present LHC injection kicker limitation (too late) October 2010 Filling Schemes proposed for the 2010 Ion Run C.Carli and J.Jowett 4/10

  5. Minor Adaptation of original EARLY scheme with 60 bunches/ring Leave out one full batch with 4 bunches • Increases the dump kicker gap • Advances the first bunch of the last batch October 2010 Filling Schemes proposed for the 2010 Ion Run C.Carli and J.Jowett 5/10

  6. The 140 bunches/ring scheme presented on 28th Sept. Very regular filling pattern (is this a real advantage?): • Basic building block - SPS accumulates 4 bunches (1 per transfer from PS) spaced by 500 ns - 975 ns for LHC injection kicker - total duration: 2475 ns or 99 “25ns positions” • 35 times this basic building block (36 times would fill an LHC ring 36*99 = 3564) • longer gap for the dump kicker • Not compatible with present LHC kicker limitations! October 2010 Filling Schemes proposed for the 2010 Ion Run C.Carli and J.Jowett 6/10

  7. A 128 bunches/ring scheme • Based on the 140 bunch scheme • Reduced number of batches to cope with injection kicker limitations • Basic building block: • Four bunches spaced by 500 ns • Injection kicker: 975 ns • 9 such blocks fill exactly one LHC quarter • Very long abort gap • Compatible with present LHC kicker restrictions! October 2010 Filling Schemes proposed for the 2010 Ion Run C.Carli and J.Jowett 7/10

  8. A 128 bunches/ring schemeCollision pattern (scheduling) with first bunches encounter at point 7 Abort gap ring 2 First bunch (both rings) Abort gap ring 1 • Collision patterns, if first bunches encounter (just an example) at point 7 • Black: collisions • Red and Blue: bunches in ring 1 and 2 not colliding with bunch in other ring • Many non-colliding bunches for all experiments • 112 collisions per turn (same for all experiments) October 2010 Filling Schemes proposed for the 2010 Ion Run C.Carli and J.Jowett 8/10

  9. A 128 bunches/ring schemeCollision pattern (scheduling) optimized for ALICE Abort gap ring 2 First bunch (both rings 5o from ALICE) Abort gap ring 1 • Collision patterns optimized with first bunches of trains encountering close to ALICE (±50) • Black: collisions • Red and Blue: bunches in ring 1 and 2 not colliding with bunch in other ring • 124 bunch encounters for ALICE and 112 for CMS and ATLAS October 2010 Filling Schemes proposed for the 2010 Ion Run C.Carli and J.Jowett 9/10

  10. The 124 bunches/ring scheme presented on 28th Sept. • Basic building block: • Four bunches spaced by 600 ns • LHC injection kicker 975 ns • Total duration: 2775 ns or 111x25 ns • Filling of one regular quarter: • Eight of above blocks plus 75 ns (increase spacing to 1050 ns • Abort gap: for one quarter leave one building block1050 ns + 2775 ns = 3825 ns • Not compatible with present LHC kicker restrictions! October 2010 Filling Schemes proposed for the 2010 Ion Run C.Carli and J.Jowett 10/10

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