Operational experience with LHC circulating beams

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1 LHC Performance Workshop - Chamonix 2009 Centre de Congrès Le Majestic, Chamonix, France 2 nd -6 th February 2008 Operational experience with LHC circulating beams Stefano Redaelli - BE/OP

2 Acknowledgments Commissioning was possible thanks to the work of MANY people: O. Aberle, I. Agapov, M. Aiba, M. Albert, R. Alemany Fernandez, G. Arduini, R. Assmann, V. Baggiolini, R. Bailey, E. Benedetto, R. Billen, L. Bottura, O. Brüning, A. Butterworth, R. Calaga, E. Carlier, P. Collier, B. Dehning, L. Deniau, S. Fartoukh, F. Follin, D. Forkel- Wirth, K. Fuchsberger, R. Giachino, M. Giovannozzi, B. Goddard, J-J. Gras, E. Hatziangeli, P. Hagen, D. Jacquet, L. Jensen, R. Jones, V. Kain, I. Kozsar, T. Kramer, G. Kruk, M. Lamont, J. Lewis, R. Losito, A. Macpherson, A. Masi, M. Meddahi, V. Mertens, M. Misiowiec, S. Page, L. Ponce, B. Puccio, S. Redaelli, C. Roderick, S. Roesler, F. Roncarolo, M. Sapinski, F. Schmidt, R. Schmidt, W. Sliwinski, R. Steinhagen, M. Strzelczyk, Y. Sun, B. Todd, E. Todesco, R. Tomas Garcia, J. Uythoven, W. Venturini Delsolaro, Heinz Vincke, Helmut Vincke, E. Veyrunes, J. Wenninger, R. Wolf, C. Zamantzas, F. Zimmermann. Acknowledge the excellent performance of the LHC injector complex and the shift crews during the days when we needed LHC beams! Also LHC shift crew! Special acknowledgments: T. Bohl, M. Lamont, R. Steinhagen, R. Tomàs, J. Wenninger Additional fruitful discussions with: G. Arduini, A. Butterworth, E. Ciapala, S. Fartouhk, R. Jones, M. Giovannozzi, W. Venturini 2

Milestones of 60 hours of LHC beam First turn!

Circulating>15min Circulating beam: 300+ turns First tune meas.

3 Milestones of 60 hours of LHC beam First turn! 10:26 TDI-B2 out 13:34 TDI-B1 out 09:35 First turn! 14:59 Beam captured! Circulating>15min Circulating beam: 300+ turns First tune meas. Mountain range Detailed measurements Long. bunch profile Optics response measurements 6 4 Vertical [ mm ] Beta-beat measur. Extracted Beam 2 [1010p] Extracted Beam 1 [1010p] Tune meter YASP: acquisition & threading 10/09 07:00 11/09 00: Longitudinal coordinate [ km ] Fast-BCT 12/09 00:00 Beam profile from Wire Scanner 3

4 Dipole powering history 757 Current in RB circuits [A] Beam current [10 10 p] Injection currents Magnet re-cycling See talk by L. Bottura in this Session 4

5 Outline Introduction Milestones of 60 hours of LHC beam Powering history Operation of accelerator systems Threading: BPM / BLM / screens Multi-turn commissioning, first tune RF capture Additional BI Overall machine performance Orbit, tune, chromaticity, optics Comparisons with design values Conclusions 5

6 First turn (1) - Beam1 on TDI Collimators in all points were used to stop the beam: - optimize beam trajectory before going into next sector; - improve the show! IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] :33:43 TDI.4L Longitudinal position [ km ] 6

7 First turn (2) - Beam1 to IP3 IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] :40:43 TCLA.A5R3.B Longitudinal position [ km ] Horizontal trajectory Vertical trajectory 7

8 First turn (3) - beam to CMS IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] :47:43 TCTH.4L5.B Longitudinal position [ km ] Horizontal trajectory Vertical trajectory 8

B1 10-5 0 5 10 15 20 25 Longitudinal position [ km ]

9 First turn (3) - beam to CMS IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] :47:43 TCTH.4L5.B Longitudinal position [ km ] Horizontal trajectory Vertical trajectory Courtesy of CMS team 9

First turn (4) - Beam 1 to the dump IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] 10-3 10-4

10 First turn (4) - Beam 1 to the dump IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] :57:31 TCSG.4R6.B Longitudinal position [ km ] Horizontal trajectory Vertical trajectory 10

11 First turn (5) - Beam1 to IR7 IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] :08:43 TCLA.D6R7.B Longitudinal position [ km ] Horizontal trajectory Vertical trajectory 11

First turn (6) - Beam1 to IR8 IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] 10-3 10-4 10:12:13

12 First turn (6) - Beam1 to IR8 IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] :12:13 TCTH.4L8.B Longitudinal position [ km ] Horizontal trajectory Vertical trajectory 12

13 First turn (7) - Beam 1 to ATLAS IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] :19:55 TCTH.4L1.B Longitudinal position [ km ] Horizontal trajectory Vertical trajectory 13

B1 10-5 0 5 10 15 20 25 Longitudinal position [ km ] Horizontal

14 First turn (7) - Beam 1 to ATLAS IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] :19:55 TCTH.4L1.B Longitudinal position [ km ] Horizontal trajectory Vertical trajectory Courtesy of T. Wengler for the ATLAS team 14

15 Closure of first turn for beam 1 IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Beam losses [ gy/s ] :26: Longitudinal position [ km ] Horizontal trajectory Vertical trajectory 15

7 Beam size meas. : 2 σ x σ y = 2.5 ɛ x 1.6 2.0 ɛ y Amplitude [a.u.] 1 0.98 0.96 0.94 0.92 0.9 0.

16 Screens, first optics checks Al screen Ti screen Screen team + F. Follin Compare H/V beam size with measured beam sizes: β x Nominal optics : = β y 25.5 = 2.7 Beam size meas. : 2 σ x σ y = 2.5 ɛ x ɛ y Amplitude [a.u.] BTV data 1st turn 2nd turn 3rd turn Fitted H size No much more on B1 commissioning x [ mm ] 16

17 Beam loss monitoring Acquisition of all ~4000 monitors available from day-1, all 12 integrations. Used extensively during all sector tests and circulating beam commissioning! Minor list of improvements of application BLM team + F. Follin 17

Multi-turns and first tune 300+ turns established in the evening of Sep. 10 th Tune was initially on the 0.5 resonance: crucial commissioned of tune meas.

18 Multi-turns and first tune 300+ turns established in the evening of Sep. 10 th Tune was initially on the 0.5 resonance: crucial commissioned of tune meas. (BBQ) at the same time! Then, tune and chromaticity to improve lifetime Found a wrong tune knob (V) RF team... First tune measurements: R. Steinhagen + BI BBQ team 18

RF capture RF OFF RF ON phase RF ON wrong phase and frequency

Courtesy of Ed Ciapala for the RF team VERY first beam

11 th ) Beam captured in the night of Sep. 11 th.

Commissioning driven by RF team from SR4.

19 RF capture RF OFF RF ON phase RF ON wrong phase and frequency ok: beam captured! RF ON wrong freq. Courtesy of Ed Ciapala for the RF team VERY first beam circulating in the LHC for several minutes (Sep. 11 th ) Beam captured in the night of Sep. 11 th. Right after, we the beam circulated for more than 10 minutes! Commissioning driven by RF team from SR4. From CCC could only watch the longitudinal profile monitor! No particular issues were found. But we need to improve the diagnostic from the CCC. 19

Extraction - first emergency dump From the logbook of Thu., Sep. 11 th First captured beam that circulated for more than 10 minutes also experienced the first real emergency dump (Sep.

20 Extraction - first emergency dump From the logbook of Thu., Sep. 11 th First captured beam that circulated for more than 10 minutes also experienced the first real emergency dump (Sep. 11 th at 22:45) Initial commissioning of system and relevant operational modes for this phase (Inject&Dump; Circulate&Dump) were achieved. The system performed very well. Dedicated talk in this session by B. Goddard - no further details here. 20

21 Additional BI: First wire scanner profile ! x = 1.67 mm σx = 2.36mm Horizontal profile Signal amplitude [a.u.] X position [ mm ] ! y = 1.68 σy = 2.38mm Vertical profile BI team + E. McCroy (LAFS) Acquisition working on Sep. 12th!! Calculated beam sizes seem compatible with the as-measured the local beta functions! Need more commissioning time... Signal amplitude [a.u.] Y position [ mm ] Data saved by S. Gilardoni 21

22 On-line β-beat measurements R. Tomàs et al. First estimated of β-beat based of 90-turn acquisition by YASP (injection oscillations), available in CCC of Fri. Sep. 12th. Better estimates available from off-line analysis. 22

23 Outline Introduction Milestones of 60 hours of LHC beam Powering history Operation of accelerator systems Threading: BPM / BLM / screens Multi-turn commissioning, first tune RF capture Additional BI Overall machine performance Orbit, tune, chromaticity, optics Comparisons with design values Conclusions 23

24 Machine integer tunes (beam 2) Nominal integer tunes: Qh = 64; Qv = 59 24

Tune, coupling and chromaticity Tunes and coupling measured for circulating beam with BBQ (without/with chirp excitation) and turnby-turn analysis of injection oscillations: Qx = 0.3803 / 0.

25 Tune, coupling and chromaticity Tunes and coupling measured for circulating beam with BBQ (without/with chirp excitation) and turnby-turn analysis of injection oscillations: Qx = / (nom = ) Qy = / (nom = ) Coupling 0.07 / 0.06 (uncorrected) Qx Qy 30 units (preliminary) Coupling compatible with expectations S. Fartouhk (LCC, 2002): 0.06 / 0.04 No corrections implemented yet!! R. Steinhagen et al., LHC-Perf-Note-007 Problem to get the nominal tunes due to coupling. Uncertainty due also to tune reproducibility. See also R. Jones talk. R. Tomàs et al., LHC-Perf-Note

26 Closed-orbit: first day X orbit [mm] Y orbit [mm] IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Horizontal closed-orbit -10 Vertical closed-orbit Longitudinal coordinate [ km ] First closed-orbit (120 turns) in the evening of Sep. 10 th, RF off (while changes of Q and Q where still being made...) Nevertheless, peak orbit errors already close to tolerance! Disclaimer: BPM not yet fully commissioned. A few faulty or strange monitor readings were found RMS = 2.25 mm Horizontal position [ mm ] RMS = 2.14 mm Arc Tol.: ± 4 mm Vertical position [ mm ] 26

Best closed-orbit: third day 120 100 80 RMS = 1.60 mm Arc Tol.: ± 4 mm 60 40 20 0-10 -7.5-5 -2.5 0 2.5 5 7.5 10 Horizontal position [ mm ] J.

27 Best closed-orbit: third day RMS = 1.60 mm Arc Tol.: ± 4 mm Horizontal position [ mm ] J. Wenninger: optimization of closed-orbit with little effort carries out on Sep. 12 th, after RF capture. The RMS calculated excluding bad BPM s (red in plot) is: RMSH = 1.6 mm; RMSV = 1.3 mm Peak-to-peak: only a few monitors outside ±4 mm tolerance. Horizontal orbit: negative offset of -1.2 mm due to energy error RMS = 1.26 mm Vertical position [ mm ] 27

28 RF settings and beam momentum Preliminary estimate of fs (T. Bohl et al): fs 60 Hz from peak detector Schottky spectrum (fs,0 66 Hz for 8 MV) RF frequency for captured beam: Hz (Δ = 229 Hz) Theoretical value: Hz Average energy offset from closed-orbit: -9.4 units (Δp/p ) (consistent with first-turn estimates) 10 units Courtesy of T. Bohl Courtesy of J. Wenninger 28

Period of the SPS cycle (42 second) - Corresponding peak perturbation larger than 500 μm (V)!

29 Problem: effect of MSI field on orbit Transverse cross-section of injection septum Perturbation of the beam orbit found by R. Steinhagen and J. Wenninger - RMS: vertical 250 μm; horizontal 100 μm. Period of the SPS cycle (42 second) - Corresponding peak perturbation larger than 500 μm (V)!! - The perturbation is fast and cannot be easily compensated by the orbit feedback Likely source of perturbation: Residual dipole kicks from the injection septa MSI in P2 / P8, pulsed with SPS timing Solution: power the MSI in DC mode - hardware allows that - with static correction! 29

Mechanical aperture of the ring Plot by R.

done systematically in Sectors 2-3 and 7-8:

measurements done for the whole LHC ring Used

30 Mechanical aperture of the ring Plot by R. Calaga Aperture measurement during sector test done systematically in Sectors 2-3 and 7-8: Example: ARC 1-2 No systematic aperture measurements done for the whole LHC ring Used measurements of response matrices to see the largest oscillations that we could fit... We routinely achieved oscillations of ±10mm without apparent problems with losses. But: no systematic scan of oscillation phases! Cannot draw firm conclusions 30

31 Beta-beat estimates All details discussed by R. Tomàs later in this session - Horizontal beating 30%, isolated peaks 40% - Vertical beating up to % No attempts yet to correct - source likely to be found. 31

32 Conclusions Great success of 10 th Sep. event Remarkable performance of most systems So far, only tested for 450 GeV beam; I<5x10 9 p; only few h of operation! Many crucial accelerator systems deployed Impressive performance of beam instrumentation Impressive list of tools available from day 1 Initial commissioning with beam of controls, injection, RF, beam dump, machine protection, collimators,... Accurate magnetic model; remarkable magnet alignment From beam point of view, the machine looks good Linear optics according to expectations Tolerance of orbit and aperture seem within reach List of problems encountered will be fed back for next run However... a LOT of work is ahead of us!! 32

33 Reserve slides 33

34 Beam losses from collimator in IR Beam on "TCSG-A4R7-B2" "TCSG-B4R7-B2" "TCSG-A5R7-B2" "TCSG-A6R7-B2" "TCSG-A4L7-B2" "TCLA-A6L7-B2" "TCP-C6R7-B2" "TCP-D6R7-B2" "TCP-B6R7-B2" "TCSG-6L7-B2" (03:06:01) (03:13:13) (03:14:01) (03:14:49) (03:05:13) (03:08:25) (03:09:13) (03:10:49) (03:11:37) (03:12:25) 10-3 All collimators around the ring up and running IP7 Could verify of all configurations BLM signal [ Gy/s ] Validate BLM locations that optimize loss response Assess collimator HW response with (small) irradiation Calibrate BLM response simulations Beam 2 (ongoing) Longitudinal position [ km ] BLM + Collimation teams 34

35 Beam current measurements First calibrated bunch-bybunch measurement Fixed-display of LHC DC-BCT LHC Fast-BCT acquisition Courtesy of M. Ludwig Programs by M. Albert 35

36 Example of response measurement 6 4 Vertical [ mm ] Longitudinal coordinate [ km ] 36

Nominal LHC parameters

Nominal LHC parameters The nominal LHC peak luminosity L = 10 34 cm 2 s 1 corresponds to a nominal bunch spacing of 25 ns and to β = 0.5 m, full crossing angle θ c = 300 µrad, and bunch population N b