Week 30 Summary week 30 26 07 02

Week 30 Summary week 30 26. 07 -02. 08 R. Bailey & J. Wenninger 9/5/2021 LHC status

Recovering from technical stop n n No physics in the week-end after technical stop. Problems to ramp nominal bunches ¨ n Monday to Wednesday were used to re-establish good ramps and squeezes and perform verifications of optics and collimation. ¨ n Significant chromaticity changes in the ramp due to 10 A/s ramp rate for ramp-down and pre-cycle. Interrupted by various problems (cryo instr, QPS, etc). Stable beams with 13 b / beam re-established Wednesday at 22: 30. Smooth fill overnight. ¨ Tricky to establish collisions in ALICE (see also later). ¨ 9/5/2021 LHC status

Beta-beat B 1 on flat top (10/11 m) Optics measurements show excellent reproducibility 9/5/2021 LHC status

Beta-beat B 2 on flat top (10/11 m) 9/5/2021 LHC status

Beta-beat B 1 at 3. 5 m 9/5/2021 LHC status

Orbit at injection n Since the introduction of the 10 A/s, much larger orbit variations are observed fill to fill at injection in the horizontal plane – signature of random b 1 error. ¨ 9/5/2021 0. 3 -0. 6 mm RMS LHC status

Periodic collimator setup validation n Validation of collimation setup for stable beams was performed on 28. 07. First validation since collimators were set up one month ago! ¨ First time with TOTEM RPs at 25 (V)/ 30 (H) sigma. ¨ Due to strong losses during squeeze, non-nominal intensity and BPM sensitivity – systematic effect on the orbit. ¨ Loss maps were OK even though B 1 vertical showed a rather high peak on a TCT in IR 2. >> To be redone this week with nominal conditions. ¨ 9/5/2021 LHC status

Loss map - Beam 1 V tune 9/5/2021 LHC status

Loss map - Beam 2 V tune 9/5/2021 LHC status

Dump setup validation n n No dedicated dump setup validation could be done. Post-mortem data analysis using the losses from beam in the abort gap indicate no anomaly. >> Proper validation to be done this week. Fill 1253 9/5/2021 LHC status

Injection n Multi-bunch injection was set up on Tuesday 27. 07 Fine energy matching R 1 -R 2 using COD of R 2 (correction of dp/p ~5 E-5) : smaller synchro loop errors, better capture. ¨ Steering and collimator settings had to be adjusted for B 1. ¨ Still issues with BLM thresholds (consistency of running sums) and loss from TL collimators adjacent MB/MQ BLMs. ¨ Injection of 25 bunches 9/5/2021 LHC status

Injection n First attempt of physics fill with 25 bunches Thursday PM. Problems with losses during injection of 4 b on B 1. ¨ Fall back to a hybrid filling scheme (can only mask IR 2 maskable BLMs below 1 E 12): ¨ n n 9/5/2021 B 2 : 4 4 1 4 4 B 1 : 4 4 12*1 LHC status

Injection revisited n Friday: another setup of multi-bunch injection for B 1. Trajectory in TI 2 moved again. Corrected, new reference. ¨ TCDIH. 29205 and TCDIH. 29050 realigned with respect to the new trajectory – shifts of 0. 1 -0. 3 mm. ¨ To get acceptable loss signals the gaps of TCDIH. 29205 and TCDIH. 29050 were opened by 0. 5 sigma to +- 5 sigma. ¨ Influence on losses: ¨ n n n Scrapping SPS : reduction by factor 10. Longitudinal blowup SPS : increase factor 9. Collimators from 4. 5 to 5 sigma : reduction by factor 4. Injection OK – but little margin on B 1 for losses. >> Better understanding of the TL trajectory changes needed – was not present with single bunch cycles. >> BLM threshold improvements. ¨ 9/5/2021 LHC status

Multi-bunch injection Friday Note that we now have 2 TCDIH in TI 2 with +/-5 sigma gaps, instead of nominal +/-4. 5 sig. ********************** *** OK for MAXIMUM 5 e 11 p+ per injection ************************ until full verification of protection settings is made. 9/5/2021 LHC status

Loss patterns Loss X-talk TI 2 LHC ring for B 1 injection Critical integration windows around ~ 2. 5 ms 9/5/2021 LHC status

Injection protection n n Phase space coverage of the protection elements (collimators) in TI 2/TI 8 needs to be checked before increasing further the intensity/injection. Downstream dipole correctors of TI 2/8 (within or downstream of collimators): Locked off for steering. ¨ Interlock settings only accessible for expert (was open to all OP). ¨ 9/5/2021 LHC status

Collisions with 25 bunches n First fill 1251 Thursday late evening Peak L seen just after colliding ~2. 8 E 30 cm-2 s-1 ¨ In STABLE BEAMS peak L ~2. 6 E 30 cm-2 s-1 ¨ TOTEM RPs at 30/25 sigma (H/V) ¨ 1. 2 MJ 9/5/2021 LHC status

Over the weekend n One fill for stable beams each night (Thursday – Sunday) Fill 1251 (Th-Fr): ¨ Fill 1253 (Fr-Sa): ¨ Fill 1256 (Sa-Su): ¨ Fill 1257 (Su-Mo): ¨ n ~ 8 hours (emerg. dump, BLMs IR 5) ~ 13 hours (prog. dump) ~ 1 hour (emerg. dump, water flow RQD S 56) 10+ hours Efficiency of ramp and squeeze hampered by various issues: Procedural >> to be fixed this week. ¨ Feedbacks >> could do with a Q feed forward. ¨ Chromaticity. ¨ 9/5/2021 LHC status

RT trims Orbit trims: • V plane very small (feed-forward + very stable), • H plane dominated here by missing MCBH. 18 R 7. B 2 Tune trims: OK on flat top, large in ramp 9/5/2021 LHC status

Intensity drop fill 1251 (G. Papotti) Color coding: - black for witness bunches (zero collisions); - red for bunches colliding in IP 1 5 and 2 (3 collisions); - blue for bunches colliding in IP 1 5 and 8 (3 collisions); - green for bunches colliding in IP 2 and 8 (2 collisions). Low lifetime on B 1 just after colliding. B 1 and B 2 different. 9/5/2021 LHC status

Intensity drop fill 1253 (G. Papotti) Color coding: - black for witness bunches (zero collisions); - red for bunches colliding in IP 1 5 and 2 (3 collisions); - blue for bunches colliding in IP 1 5 and 8 (3 collisions); - green for bunches colliding in IP 2 and 8 (2 collisions). Low lifetime on B 1 just after colliding. B 1 and B 2 different. 9/5/2021 LHC status

Cleaning in stable beams Momentum cleaning with collisions 9/5/2021 LHC status

Orbit (in physics) n Orbit changes wrt June ref. in basically all low-beta IRs: Always positive (both planes and beams) ! ¨ In most cases corrections would require suspiciously huge trims. ¨ Triplet Wire Positioning System does not indicate significant movements. ¨ n Orbit at TCTs drifted significantly in some IRs wrt June references. Most prominently in ALICE, TCTH B 2 (~ 2 sigma). ¨ Large H orbit deviations around ALICE IR can be cleaned, but to become ‘permanent’ need to change the procedure (settings organization) to move from end of squeeze to collisions. ¨ TCT alignment check in physics to be done. ¨ 9/5/2021 LHC status

Orbit on flat top – diff wrt June 9/5/2021 LHC status

MPS statistics n n n We have accumulated 171 dumps above 450 Ge. V. In all cases the MPS reacted correctly, even for yet unexplained events. There are 2 events where the cause is not understood, on July 7 th (BLM IR 7) and July 30 th (BLM IR 5). ¨ Common features: n n ¨ Event July 30 th: n n 9/5/2021 Loss at cold element – ‘bypass’ collimation (loss too fast…) Loss time scale ~2 milliseconds ~20 turns. Loss after a bending section (DS IR 7, D 1 IR 5). Orbit and trajectory stable. All PC currents rock stable – no trims etc. Orbit stable to few microns, trajectory to few tens of microns (resolution!). LHC status

Event 30 th July Loss on Q 4 L 5 from beam 2. 9/5/2021 LHC status

Program this week n n Stable physics run – MPS stability period - 25 bunches. Test ramp(s) with 1 -2 bunches: ¨ ¨ ¨ n Establish better end-squeeze to collision sequence/settings. Clean orbit in stable beams (ALICE H plane, . . ). Check TCTs. Collimator loss maps. Beam dump validation. Feedbacks OFB - 2 x 3 -4 hours tests at injection. ¨ QFB – Feed forward to reduce dependency on QFB ¨ n 9/5/2021 Hump LHC status

Interventions needed n Delay of the PM trigger of the BLM system to be set back Causes problems for PM analysis (differences of acquisition rates between diff. Cards). >> to be done ASAP (inter fill period. . . ). ¨ n n Magnetic probes in the machine for the studies related to the hump - access in point 5 (GA, LW) Repair COD MCBH. 18 R 7. B 2 Cryo instrumentation QTL 9. R 7 B 1 (cable change) – not urgent. CV need to replace a motorisation of the water valve of the sector 56 - not urgent ¨ 9/5/2021 Time estimate ~3 h LHC status