Status of LHC Performance

1. Status of LHC Performance Performance, problems, projection Mike Lamont for the LHC team

2. Ramp-up of number of bunches MD, technical stop Intermediate energy, TS, scrubbing 15 weeks LHC status

3. Ramp-up - performance Reached 1380 (maximum possible with 50 ns bunch spacing) on 27th June LHC status

4. Luminosity 26 pb-1/day LHC status

5. LHCb LHC status

6. Ramp-up: not all plain sailing From 3 to 1380 bunches with a previous maximum of 368 in 15 weeks elapsed (via MD, TS, scrubbing, intermediate energy) has to be regarded as pretty good, however… • UFOs • In particular at the injection kickers • Single Event Effects (SEE) • QPS, Cryogenics, Collimators, Power converters… • RF • Couplers – particularly on trips • RF wave-guide arc detectors • Beam induced heating • injection kickers, cryogenics, collimators.. • Vacuum activity LHC status

7. Increasing intensity – machine protection • Collimation always critical • Good stability - regular loss maps performed • 144 bunches from SPS • Beam quality from injector important • 144 bunches per injection from SPS - 1.2 MJ down the lines • High temperature superconducting current lead quenched (7th April) • Invoked quench of 11 magnets • Injection Kicker Flashover (18th April) • Not pretty, heavy beam loss • Injection kicker erratics (28th July) • Two incidents – not pretty, heavy beam loss Routinely dealing with 90 to 100 MJ per beam at 3.5 TeV LHC status

8. 2011 parameters - end June LHC status

9. Emittance x’ • As we move around the machine the shape of the ellipse will change as (s) changes with the varying quadrupole (de-)focusing • However the area of the ellipse () does not change • Emittance shrinks naturally as we go up in energy (pS increases, pT doesn’t) • Define energy independent normalized emittance: • Units are mm.mrad but normally use microns (and drop normalized) • Handy – constant across complex (give or take some blow-up) x  x LHC status

10. Aim: maximize peak luminosity LHC status

11. Conclusions from mini-Chamonix • Minimize (normalized) emittance (~2 microns) • Adiabatically increase bunch intensity (to ~1.6e11 ppb) • Maximum from injectors with 50 ns • Beta* = 1 m should be OK (collimation, beam-beam) • Prepare test and then possibly implement after next technical stop • Stick with 50 ns • Test 25 ns in MD & trial stable beams with limited number of 25 ns trains LHC status

12. Emittances – start of fill – from luminosity LHC status

13. Bunch intensities Emittances down, bunch intensity more-or-less constant LHC status

14. It wasn’t meant to be like this 20% of design luminosity: - half design energy - nominal bunch intensity- half nominal emittance- beta* = 1.5 m (design 0.55 m) LHC status

15. Emittance reduction • Up until a week ago we’d been working with emittance blow-up in the SPS to give around 2.0 microns injected into the LHC (having worked down from 2.5 - 3.0) • This gave good luminosity but some issues with beam losses when adjusting collisions before stable beams • When switching off the blow-up completely – emittance from SPS of 1.6 microns – miraculously everything cleaned up • Assumption: non-Gaussian tails generated by the blow-up were causing the problem… LHC status

16. Beam-beam tune shift Design report Now Tatiana Pieloni LHC status

17. Working point optimization Slight shift of the horizontal and vertical tune before collisions Positive effect on beam lifetime either by moving some of the tune footprint away a resonance, or perhaps, a 50 Hz harmonic Fill 1992 – Qh = 0.312Qv = 0.322 Coupled with the removal of transverse blow-up, removal of lifetime dip on going into collisions Gianluigi Arduini LHC status

18. Operational efficiency LHC status

19. Last week: fills above 450 GeV 1/2 LHC status

20. Last week: fills above 450 GeV 2/2 The last one took the cryogenics out for ~36 hours LHC status

21. Dumps > 450 GeV since Monday 18th July From Monday 18th July and the move back up to 1380 bunches Around 15/33 down to high intensity or high luminosity LHC status

22. Short fills hurt and in particular LHCb LHC status

23. Still managed ~210 pb-1 last week LHC status

24. Three recent headaches PROBLEMS PROBLEMS PROBLEMS LHC status

25. Luminosity driven SEE Markus Brugger LHC status

26. Markus Brugger for R2E at mini-Chamonix LHC status

27. Planned mitigation – UJ16 Shield and re-locate Christmas technical stop In the meantime – victims of our own success LHC status

28. Vacuum - right of IP2 – last week Possible explanation (V. Baglin) is the outgassing of an ion pump when the discharge is starting from time to time. Increase the interlock level on the nearby vacuum gauge temporarily to allow cleaning LHC status

29. Vacuum spikes 4L8: 23-24 July Dump Dump LHC status

30. Vacuum after technical stop Vincent Baglin • Triplets warmed up during technical stop to flush and pump absorbed gas • During the “distillation process”, most of the gas desorbed during the scrubbing run was either pumped out or flushed to the cold bore : • Hydrogen, methane and carbon monoxide were pumped out • Carbon dioxide was flushed to the cold bore • Water remained at its original location • During this process, gas was redistributed in all the vacuum sector • So, we could expect some minor reconditioning …. And indeed the spikes do appear to have calmed down LHC status

31. Injection kicker erratics Side view Kicker TDI D1 Un-kicked injected beam to upper TDI jaw Kicked circulating beam to lower jaw LHC status

32. Injection kicker – PFN & switches DS MS PFN Mike Barnes LHC status

33. MKI2 Erratic of MS3 at 18:03:09hrs ON 28/7/2011 PFNs 1 & 2 at normal voltage (~50kV) PFNs 4 at low voltage (~33kV) because of PFN3 switch erratic Erratic (untriggered) turn-on of MKI2 MS3 Mike Barnes • At 18:03:09hrs an erratic (untriggered) turn-on of MKI2 MS3 occurred during resonant charging – sending current to one of the four kicker magnets; • Interlocks did NOT detect erratic of MS3 (at 33kV): hence no immediate action was taken to turn-on other thyratrons. PFNs discharged via the DS after 4ms (no further magnet current); • The failure occurred early in the charging process, and the extraction from the SPS was inhibited; • The circulating beam which was swept over the aperture and protection elements (~17% of normal kick) for ~9µs. LHC status

34. MKI2 event no. 2 – dumped beam • BTVDD and dump line BCTs indicate that ~ 200 bunches of the circulating were not dumped  to TDI. LHC status

35. Next THREE months LHC status

36. Schedule LHC status

37. What are days for? Ah, solving that questionBrings the priest and the doctorIn their long coatsRunning over the fields. Protons: 2nd August to 29th October inclusive +25 ns studies to come during MDs (to sort out injection and beam stability issues) and possibly an operational development period to validate scrubbing and future operation 70 days at present performance, reasonable efficiency ~2 fb-1 LHC status

38. Conclusions • Start August • Excellent peak luminosity performance & production rates • Very good through inject, ramp, squeeze, collide • Effective turn around time is long: problem resolution, accesses etc…cruisingwe are not • Short fills – exposedto the intersecting failure space of a number of complex systems with huge number of components. • This failure space is inflated by high intensity and high luminosity • Holding is sometimes more effective than raising • Although the effects of “conditioning” and mitigation (UFOS, vacuum, RF, QPS, SEUs) is clear… • Will not be pushing bunch intensity aggressively until things settle down LHC status

39. Curate’s egg “parts of it are excellent” LHC status