PbPb run 2018 tasks Optics and bump configuration

Pb-Pb run 2018 - tasks • Optics and bump configuration – Backup plan if aperture problems in IR 2 – ALICE polarity reversal switch strategy (Avoid 2 injection&Ramp setups, end of squeeze? separation plane rotation for squeeze? ) – New proposal today for greater safety (JMJ, SF) – Details for collimation simulation – Checks with collimation and MPP • ~45/30 o MKD-TCT phase for Beam ½ - RB today • Commissioning and run plan (JMJ, JW, everyone …) – Optics cycle partly commissioned (flat) on 22/8/2018 • See next slide – – – BFPP bumps under way (MS, JMJ) Ramp-up steps from MPP (JMJ, RB, …) Integrate crystal collimation tests during MD 4, ramp-up Aperture measurements in IR 2 (RB et al) Survey data for BFPP (MG, RB, SU group) • Collimator and BLM settings (RB, …) – Plan discussions at BLMTWG and r. MPP meetings • Levelling and filling schemes (JMJ, MS, LPCs) – Some discussion with LPC – Backup schemes in case of total-intensity limit with 75 ns (100 ns? ) J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 1

Optics commissioning – more details from RT next meeting Intensity limited on 22/8/2018 due to vacuum in SPS – opportunity to start optics commissioning of 6. 37 Z Te. V HI cycle in LHC. β*=(0. 5, 1. 5) m will be lowest value ever for ALICE and LHCb. New combined ramp and squeeze to β*=(1, 1, 1, 1. 5) m followed by short squeeze. Successful commissioning of full cycle with flat orbits. Coupling compensation knobs established. β-beating reduced to < 10% peak with local corrections of IRs only. Next: measurement and correction with all bumps, global corrections, aperture measurements in IR 2. J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 2

Upcoming meetings • https: //indico. cern. ch/category/7179/ More frequent meetings now and up to start of run. (May not need all of them. ) Calendar invitations sent to essential people only, nearer the time, but open to everyone. NB some are on THURSDAY! First report to LMC on 29/8/2018 Anton Lechner proposes BLMTWG meeting for heavy-ion run on the 18 th of Sep (in the usual time slot at 14 h 00, possibly changed to 10: 30 ? ). J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 3

ALICE polarity reversal, new proposal • As usual, ALICE requires spectrometer polarity switch halfway through the run • ALICE also requires small net crossing angle at the IP for ZDC (injection elements limit aperture) • Ramp and squeeze with the same external crossing angle to avoid recommissioning time. • After ALICE polarity reversal, we must reverse the external crossing angle after the final squeeze to physics conditions, potentially passing through conditions with small separation at parasitic beam-beam encounters in IR 2. • Now we have more encounters (75 ns? ) and lower β* than in 2015, also lowering of ALICE IP by -2 mm • Show critical stages in following slides, only phase after end of squeeze, some checks on earlier phases still to do. J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 4

IR 2 ALICE –ve, end squeeze Horizontal parallel separation increased to ± 3 mm IP shift bump still off Favourable polarity with respect to IP (neutrons moving up) J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 5

IR 2 ALICE –ve, end squeeze, beam-beam for Beam 1 n 1 plots from S. Fartoukh J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 6

IR 2 ALICE +ve, end squeeze Horizontal parallel separation increased to ± 3 mm IP shift bump still off Must still reverse external bump to unfavourable polarity with respect to IP (neutrons moving down) J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 7

IR 2 ALICE +ve, end squeeze, beam-beam for Beam 1 n 1 plots from S. Fartoukh J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 8

IR 2 ALICE +ve, external angle zero Horizontal parallel separation increased to ± 3 mm IP shift bump still off Transition through zero external bump to unfavourable polarity with respect to IP (neutrons moving down) J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 9

IR 2 ALICE +ve, external angle zero, beam-beam Beam 1 Separations at outermost encounters have been increased by larger horizontal separation. Beam-beam tune-shifts remain small. J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 10

IR 2 ALICE +ve, external angle reversed Horizontal parallel separation still at ± 3 mm, could have started to bring it down before this point IP shift bump still off Reversed external bump to unfavourable polarity with respect to IP (neutrons moving down) J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 11

IR 2 ALICE +ve, external angle zero, beam-beam Beam 1 Not yet physics … J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 12

Summary for ALICE polarity reversal • New proposal for larger horizontal parallel separation in IR 2 at end of squeeze – Check how soon we should bring it in • Allows better separation for +ve polarity and reversal of external angle • Parallel separation can be reduced as IP shift bump is brought in at the end of collision beam process • Many more plots than I have shown here • In physics we also have levelling bump to avoid exceeding ALICE saturation luminosity J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 13

BACKUP SLIDES J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 14

Case 1: Beam-beam separation at end of squeeze - vertical Horizontal parallel separation by 2 mm Favourable polarity with respect to IP (neutrons moving up) Dashed lines show potential beam-beam encounters with 25 ns beam, bunches in 100 ns or 75 ns beam only sample some of them. J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 15

Case 1: Corrector strength usage J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 16

Case 2: 10σ Beam envelopes at end of squeeze - vertical Horizontal parallel separation by 2 mm After switch: unfavourable polarity with respect to IP (neutrons moving down) J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 17

Case 2: Beam-beam separation at end of squeeze - vertical Horizontal parallel separation by 2 mm After switch: unfavourable polarity with respect to IP (neutrons moving down) Dashed lines show potential beam-beam encounters with 25 ns beam, bunches in 100 ns or 75 ns beam only sample some of them. J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 18

Case 2: Corrector strength usage Need to check! J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 19

Case 3: 10σ Beam envelopes at end of squeeze - vertical Horizontal parallel separation by 2 mm During switch: zero external crossing angle J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 20

Case 3: Beam-beam separation at end of squeeze - vertical Horizontal parallel separation by 2 mm During switch: zero external crossing angle Dashed lines show potential beam-beam encounters with 25 ns beam, bunches in 100 ns or 75 ns beam only sample some of them. J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 21

Case 3: Corrector strength usage J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 22

Conclusions • Beam separation in transition to opposite polarity looks adequate, not much worse than previous years – Analysis will continue • Propose to continue without recommissioning ramp and squeeze. – Possibly look at how to do it in emergency … J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 23

Status of planning for HI 2018 Pb-Pb run • Michaela at Evian, Dec 2017 – https: //indico. cern. ch/event/663598/contributions/2782520/ • JMJ at Chamonix, Jan 2018 – https: //indico. cern. ch/event/676124/contributions/2767841/ • Stephane presents optics, Mar 2018 – https: //indico. cern. ch/event/708091/ – Optics strategy choice has been made • Further evolution meanwhile – – Use 75 ns filling scheme if possible, otherwise 100 ns Ion source refills pencilled in O-O pilot run at the end, suggested, dropped Resumption of usual planning meetings from now: • https: //indico. cern. ch/category/7179/ (tentative dates …) J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 24

Run plan, requirements • Commissioning and validation with: • 6. 37 Z Te. V, ramp to β*=(1, 1, 1, 1. 5), then squeeze to β*=(0. 5, 1. 5), • BFPP bumps in ATLAS, CMS • ALICE: crossing angle for ZDC, vertical IP shift • ALICE polarity reversal at integrated luminosity mid-point, NOT for LHCb • Collimator settings to avoid any unwanted loss locations • Levelling by separation and filling schemes to share luminosity • Van der Meer scans, as required by experiments • Ion source refills – already planned but can adapt • MD/physics fill to explore maximum luminosity in ATLAS/CMS • BFPP quench MD to confirm 2015 result (around ATLAS? ) • Collimation (crystal? ) MDs ? J. M. Jowett, HI 2018 preparation meeting, 11/9/2018 25