1. Summary week 30 Week 30 R. Bailey & J. Wenninger 26.07-02.08
11/28/2018
LHC status

2. Recovering from technical stop
No physics in the week-end after technical stop.
Problems to ramp nominal bunches
Significant chromaticity changes in the ramp due to 10 A/s ramp rate for ramp-down and pre-cycle.
Monday to Wednesday were used to re-establish good ramps and squeezes and perform verifications of optics and collimation.
Interrupted by various problems (cryo instr, QPS, etc etc).
Stable beams with 13b / beam re-established Wednesday at 22:30.
Smooth fill overnight.
Tricky to establish collisions in ALICE (see also later).
11/28/2018
LHC status

3. Beta-beat B1 on flat top (10/11 m)
Optics measurements show excellent reproducibility
11/28/2018
LHC status

4. Beta-beat B2 on flat top (10/11 m)
11/28/2018
LHC status

5. Beta-beat B1 at 3.5 m
11/28/2018
LHC status

6. Orbit at injection
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 b1 error.
mm RMS
11/28/2018
LHC status

7. Periodic collimator setup validation
Validation of collimation setup for stable beams was performed on
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 B1 vertical showed a rather high peak on a TCT in IR2.
>> To be redone this week with nominal conditions.
11/28/2018
LHC status

8. Loss map - Beam 1 V tune
11/28/2018
LHC status

9. Loss map - Beam 2 V tune
11/28/2018
LHC status

10. Dump setup validation
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
11/28/2018
LHC status

11. Injection Multi-bunch injection was set up on Tuesday 27.07
Fine energy matching R1-R2 using COD of R2 (correction of dp/p ~5E-5) : smaller synchro loop errors, better capture.
Steering and collimator settings had to be adjusted for B1.
Still issues with BLM thresholds (consistency of running sums) and loss from TL collimators  adjacent MB/MQ BLMs.
Injection of
25 bunches
11/28/2018
LHC status

12. Injection First attempt of physics fill with 25 bunches Thursday PM.
Problems with losses during injection of 4 b on B1.
Fall back to a hybrid filling scheme (can only mask IR2 maskable BLMs below 1E12):
B2 :
B1 : *1
11/28/2018
LHC status

13. Injection revisited
Friday: another setup of multi-bunch injection for B1.
Trajectory in TI2 moved again. Corrected, new reference.
TCDIH and TCDIH realigned with respect to the new trajectory – shifts of mm.
To get acceptable loss signals the gaps of TCDIH and TCDIH were opened by 0.5 sigma to +- 5 sigma.
Influence on losses:
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 B1 for losses.
>> Better understanding of the TL trajectory changes needed – was not present with single bunch cycles.
>> BLM threshold improvements.
11/28/2018
LHC status

14. Multi-bunch injection Friday
Note that we now have 2 TCDIH in TI2 with +/-5 sigma gaps, instead of nominal +/-4.5 sig. ******************************************** *** OK for MAXIMUM 5e11 p+ per injection *** ******************************************** until full verification of protection settings is made.
11/28/2018
LHC status

15. Loss patterns Loss X-talk TI2  LHC ring for B1 injection
Critical integration windows around ~ 2.5 ms
11/28/2018
LHC status

16. Injection protection
Phase space coverage of the protection elements (collimators) in TI2/TI8 needs to be checked before increasing further the intensity/injection.
Downstream dipole correctors of TI2/8 (within or downstream of collimators):
Locked off for steering.
Interlock settings only accessible for expert (was open to all OP).
11/28/2018
LHC status

17. Collisions with 25 bunches
First fill 1251 Thursday late evening
Peak L seen just after colliding ~2.8E30 cm-2s-1
In STABLE BEAMS peak L ~2.6E30 cm-2s-1
TOTEM RPs at 30/25 sigma (H/V)
1.2 MJ
11/28/2018
LHC status

18. Over the weekend
One fill for stable beams each night (Thursday – Sunday)
Fill 1251 (Th-Fr): ~ 8 hours (emerg. dump, BLMs IR5)
Fill 1253 (Fr-Sa): ~ 13 hours (prog. dump)
Fill 1256 (Sa-Su): ~ 1 hour (emerg. dump, water flow RQD S56)
Fill 1257 (Su-Mo): 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.
11/28/2018
LHC status

19. Tune trims: OK on flat top, large in ramp
RT trims
Orbit trims:
V plane very small (feed-forward + very stable),
H plane dominated here by missing MCBH.18R7.B2
Tune trims: OK on flat top, large in ramp
11/28/2018
LHC status

20. 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 B1 just after colliding.
B1 and B2 different.
11/28/2018
LHC status

21. 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 B1 just after colliding.
B1 and B2 different.
11/28/2018
LHC status

22. Cleaning in stable beams
Momentum cleaning with collisions
11/28/2018
LHC status

23. Orbit (in physics)
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.
Orbit at TCTs drifted significantly in some IRs wrt June references.
Most prominently in ALICE, TCTH B2 (~ 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.
11/28/2018
LHC status

24. Orbit on flat top – diff wrt June
11/28/2018
LHC status

25. MPS statistics We have accumulated 171 dumps above 450 GeV.
In all cases the MPS reacted correctly, even for yet un-explained events.
There are 2 events where the cause is not understood, on July 7th (BLM IR7) and July 30th (BLM IR5).
Common features:
Loss at cold element – ‘bypass’ collimation (loss too fast…)
Loss time scale ~2 milliseconds ~20 turns.
Loss after a bending section (DS IR7, D1 IR5).
Orbit and trajectory stable.
Event July 30th:
All PC currents rock stable – no trims etc.
Orbit stable to few microns, trajectory to few tens of microns (resolution!).
11/28/2018
LHC status

26. Event 30th July
Loss on Q4 L5 from beam 2.
11/28/2018
LHC status

27. Program this week
Stable physics run – MPS stability period - 25 bunches.
Test ramp(s) with 1-2 bunches:
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
Hump
11/28/2018
LHC status

28. Interventions needed
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...).
Magnetic probes in the machine for the studies related to the hump - access in point 5 (GA, LW)
Repair COD MCBH.18R7.B2
Cryo instrumentation QTL9.R7B1 (cable change) – not urgent.
CV need to replace a motorisation of the water valve of the sector 56 - not urgent
Time estimate ~3h
11/28/2018
LHC status