Supraleitende Magnete für den LHC Proton-Proton Collider

Supraleitende Magnete für den LHC Proton-Proton Collider

CERN LHC - challenges in handling beams exceeding 140 MJ Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ Rdiger Schmidt, CERN 17 September 2012 page 1 CERN ..a long history Introduction to the LHC and its challenges Machine protection and collimation Even before the drawing-board stage, the farsighted John Adams noted in 1977 Operational cycle and observations that the tunnel for a future large electronpositron (LEP) collider should also Final remarks be big enough to accommodate another ring of magnets. Rdiger Schmidt

LHC - challenges in handling beams exceeding 136 MJ page 2 CERN ..a long history This presentation is an introduction to LHC challenges, details are presented in a large number of presentation on LHC and its Injectors during this workshop Even before the drawing-board stage, the farsighted John Adams noted in 1977 This presentation is on behalf of the large team working on LHC and its that the tunnel for a future large electronpositron (LEP) collider should also injectors. Acknowledgements to many colleagues for their help and material. be big enough to accommodate another ring of magnets. Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 3 CERN LHC nominal versus LHC today

Nominal Proton momentum: Peak Luminosity: Stored energy/beam: 7 TeV/c 1034 [cm-2s-1] 2808 bunches (25 ns): 362 MJoule Operation in 2008-2011 LHC start of beam operation in 2008, followed by the accident LHC re-start of beam operation limited to 3.5 TeV in 2009 Successful operation in 2010 and 2011 at 3.5 TeV Operation in 2012 Proton momentum: Peak Luminosity: Stored energy/beam: Rdiger Schmidt 4 TeV/c 7.71033 [cm-2s-1] 1380 bunches (50 ns): 140 MJoule LHC - challenges in handling beams exceeding 136 MJ page 4 CERN

Peak luminosity evolution during 2012 Start-up phase for machine protection Rdiger Schmidt Recovering from technical stop and increase approaching limits Recovering from technical stop, approaching limits, changing parameters LHC - challenges in handling beams exceeding 136 MJ page 5 CERN Integrated luminosity in 2012 Smaller *, smaller emittances, higher bunch currents Rdiger Schmidt

LHC - challenges in handling beams exceeding 136 MJ >14 fb-1 page 6 CERN LHC operation: a success? excellent Rdiger Schmidt acceptable LHC - challenges in handling beams exceeding 136 MJ disappointing page 7 CERN LHC operation: a success? acceptable

Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 8 CERN LHC operation: a success? excellent ATLAS Collaboration, Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC, Phys.Lett.B (2012) CMS Collaboration, Observation of a new boson at a mass of 125 GeV with the CMS experiment Schmidt LHC - challenges in handling beams exceeding 136 MJ at Rdiger the LHC, Phys.Lett.B (2012 page 9

CERN LHC luminosity (nominal parameters at 7 TeV) Number of protons per bunch limited to about 1-31011 due to the beam-beam interaction and beam instabilities, nominal 1.151011 f = 11246 Hz Emittance given by injectors, nominal emittance constant Beam size 16 m m, for = 0.5 m ( function) is a function of the lattice) L = for one bunch L= with 2808 bunches (every 25 ns one bunch) L = 1034 [cm-2s-1] Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ

page 10 CERN Role of injector complex The luminosity depends on the emittance and the intensity per bunch (=> high brightness), given to a large extent by the complex chain of injectors (LINAC, Booster, PS and SPS) Other parameters are the number of bunches Beam structure (25 ns or 50 ns bunch spacing), also defined by the injectors Number of bunches in a batch (e.g. 144 bunches/batch from SPS -> LHC) In total, 1380 bunches in 2012 A large amount of work is going on to understand and improve the beam parameters in the injector complex

Understanding and improving present performance Improvement program during the next decade Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 11 CERN Reports related to the improvements of the injectors Brightness Evolution for LHC Beams during the 2012 Run, Bettina Mikulec (CERN, Geneva) Low gamma transition optics for the SPS: simulation and experimental results for high brightness beams, Hannes Bartosik (CERN, Geneva) Beam Stability and Tail Population at SPS Scrapers, Bettina Mikulec (CERN, Geneva) Review of longitudinal instabilities in the SPS and beam dynamics issues with high harmonic RF systems in accelerators, Elena Shaposhnikova (CERN, Geneva) Tune Spread Studies at Injection Energies for the CERN Proton Synchrotron Booster, Bettina Mikulec (CERN, Geneva) Longitudinal Beam Loss Studies of the CERN PS-to-SPS Transfer, Helga Timko (CERN, Geneva)

Fully 3D long-term simulation of the coupling resonance experiments at the CERN PS, Ji Qiang (LBNL, Berkeley, California) Longer term programme The high intensity/high brightness upgrade program at CERN: status and challenges, Simone Silvano Gilardoni (CERN, Geneva) Linac4 beam dynamics and commissioning strategy, Jean-Baptiste Lallement (CERN, Geneva) Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 12 CERN Challenges Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 13 CERN The LHC: just another collider ? Start

Type Max proton energy Length [m] B Field [Tesla] Luminosity [cm-2s-1] [GeV] TEVATRON Fermilab Illinois USA HERA DESY Hamburg RHIC Brookhaven Long Island

LHC CERN Factor Rdiger Schmidt Stored beam energy [MJoule] 198 3 p-pbar 980 6300 4.5 4.3 1032 1.6 for protons

199 2 p e+ p e- 920 6300 5.5 5.1 1031 2.7 for protons 200 0 Ion-Ion p-p 250 3834 4.3

1.5 1032 0.9 per proton beam 200 8 Ion-Ion p-p 7000 26800 8.3 1034 362 per beam 100 Now 4000 7

Now 6 1033 4 2 LHC - challenges in handling beams exceeding 136 MJ 20 page 14 CERN Challenges: High Luminosity and Machine Protection Large amount of energy stored in the beams Injecting beams, performing the energy ramp and bringing the beams into collisions . without quenching or even damaging accelerator and experiments Dumping 130 MJ beam without quenching magnets

Detecting all failures that could lead to uncontrolled beam losses Avoiding beam losses, in particular in the superconducting magnets Superconducting magnets might quench when 10 -8-10-7 of beam (106107 protons) hit magnet Beam cleaning using collimators (betatron and momentum cleaning) is vital during operation Radiation, in particular in experimental areas from beam collisions Single event upset in the tunnel electronics Radiation induced damaged of material (not yet observed) Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 15 CERN Challenges: High Luminosity and Beam Dynamics

Beam-Beam effects, head-on and long range Beam instabilities due to the machine impedance Collimators with jaws very close to beam contribute to the impedance Collimator position depends on energy and on beta function at collision point (collimators move close to the beam during energy ramp) Heating of components close to the beam (kickers, collimators, beam instruments, vacuum bellows, ), already (limited) damage of components Electron cloud effects Photo electrons, generated by beam losses - accelerated by the following bunches lead to instabilities Tools to fight instabilities

Octupoles, chromaticity, transverse damper, Head-on beam-beam effect provides stability (tune spread) Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 16 CERN 7 TeV and 2800 bunches 360 MJoule - what does this mean? The energy of an 200 m long fast train at 155 km/hour corresponds to the energy of 360 MJoule stored in one LHC beam 360 MJoule: the energy stored in one LHC beam corresponds approximately to 90 kg of TNT 8 litres of gasoline 15 kg of chocolate Its how easy the energy is

released that matters most !! Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 17 CERN 360 MJoule - what does this mean? The energy of an 200 m long fast train at 155 km/hour corresponds to the energy of 360 MJoule stored in one LHC beam An experiment on hydrodynamic tunnelling of the SPS high intensity proton beam at the HiRadMat facility, Juan Blanco (CERN, Geneva) High Energy Tests of Advanced Materials for Beam Intercepting Devices at CERN HiRadMat Facility, Alessandro Bertarelli (CERN, Geneva) Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 18

CERN SPS experiment: Beam damage with 450 GeV proton beam Controlled SPS experiment 81012 protons clear damage beam size x/y = 1.1mm/0.6mm Beam direction above damage limit for copper 21012 protons below damage limit for copper 25 cm 6 cm A B D C

Damage limit ~200 kJoule 0.1 % of the full LHC 7 TeV beams Energy in a bunch train injected into LHC: factor of ~10 above V.Kain et al Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 19 CERN Beam losses Particles are lost due to a variety of reasons

Continuous beam losses are inherent to the operation of accelerators Beam-gas interaction Losses from collisions Losses due to the beam halo touching the aperture Losses due to instabilities Losses due to failures (e.g. power converters, RF, controls, .) End of a physics fill Taken into account during the design of the accelerator Accidental beam losses are due to a multitude of failures mechanisms The number of possible failures leading to accidental beam loss is (nearly) infinite Any failure must result in beam dumps to avoid uncontrolled beam loss

Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 20 CERN Machine protection and collimation Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 21 LHC Layout Beam dump blocks CERN IR5:CMS eight arcs (sectors) eight long straight section (about 700 m

long) IR4: RF + Beam instrumentation Signal to kicker magnet IR6: Beam dumping system IR3: Moment Beam Cleaning (warm) IR7: Betatron Beam Cleaning (warm) IR8: LHC-B IR2: ALICE Detection of beam losses with >3600 monitors around LHC IR1: ATLAS Injection Rdiger Schmidt

from SPS LHC - challenges in handlingBeams beams exceeding 136 MJ Injection page 22 Layout of beam dump system CERN To get rid of the beams (also in case of emergency!), the beams are kicked out by a ultra-high reliable system of kicker magnets with and send into a dump block ! Septum magnets deflect the extracted beam vertically Kicker magnets to paint (dilute) the beam Beam dump block

about 700 m 15 fast kicker magnets deflect the beam to the outside about 500 m The 3 s gap in the beam gives the kicker time to reach full field. quadrupoles Beam 2 Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 23 CERN Dump line Beam dump line and graphite absorber at the end Rdiger Schmidt

LHC - challenges in handling beams exceeding 136 MJ page 24 CERN Beam dump with 1380 bunches Beam spot at the end of the beam dumping line, just in front of the beam dump block Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 25 CERN View of a two sided collimator about 100 collimators are installed in LHC RF contacts for

guiding image currents 2 mm Beam spot Faster alignment technique for the LHC collimation length about 120 system, Stefano Redaelli (CERN, Geneva) cm Experimental Verification for a Collimator with InJaw Beam Position Monitors, Daniel Wollmann (CERN, Geneva) Ralph Assmann, Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 26 CERN Betatron beam cleaning Cold aperture Primary collimator

Secondary collimators Tertiary collimators Shower absorbers SC Triplet Tertiary beam halo + hadronic showers Circulating beam Arc(s) Cleaning insertion Arc(s) IP Illustration drawing Rdiger Schmidt

LHC - challenges in handling beams exceeding 136 MJ page 27 CERN Beam Loss Monitors Ionization chambers to detect beam losses: Reaction time ~ turn (40 s) Very large dynamic range (> 106) ~3600 chambers distributed over the ring to detect abnormal beam losses and if necessary trigger a beam abort (happened many times) Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 28 CERN Operational cycle and observations Rdiger Schmidt

LHC - challenges in handling beams exceeding 136 MJ page 29 CERN 2 10 Beam Intensities and Luminosity, 11-18/6/2012 Stable performance 14 Beam intensity 6 10 Stable performance 33 Luminosity Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ

page 30 CERN Overview of fills 51 % of time in stable beams; total of 1.3 fb-1 in one week ! Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 31 CERN LHC operational cycle Stable beams Injection process at 450 GeV Energy ramp to 4 TeV Squeezing beta

functions from 11m to 0.6m (IP1 and IP5) Adjust: bringing beams into collisions Record fill 2692 in 2012, fill with max. integrated luminosity Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 32 CERN Excellent fill 2195 in 2011 ~15 MJ ~130 MJ Stable beams

Injection and ramp Beam dump A nice long fill of about 18 hours Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 33 CERN Separation and crossing: example of ATLAS Horizontal plane: the beams are combined and then separated 194 mm ATLAS IP ~ 260 m Common vacuum chamber Vertical plane: the beams are deflected to produce a crossing angle at the IP

to avoid undesired encounters in the region of the common vacuum chamber ~ 7 mm a Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ Not to scale ! About 60 parasitic crossings in LHC forpage 5034ns CERN Injecting 1370 bunches - in batches of 144 bunches ~15 MJ ~1.4 MJ Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 35

CERN Zoom: injection of first batch with 12 bunches ~1.6 MJ ~0.13 MJ Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 36 CERN Zoom: injection of first bunch with pilot bunches Inject very safe beam If beam circulates, inject reasonably safe beam If beam circulates, inject unsafe beam Conditions are ensured by an interlock system based on hardware ~700 J

Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 37 CERN June 2011, Fill 1875, 3.5 TeV, 2011, 1092 bunches 12.8 MJoule 06:15:01 end adjust 05:48:22 end ramp 05:49:11 start squeeze Rdiger Schmidt 05:59:41 end squeeze Beam losses <<1%

LHC - challenges in handling beams exceeding 136 MJ page 38 CERN June 2012, Fill 2733, 4 TeV, 2012, 1380 bunches/beam 12.8 MJoule 02:16:47 end ramp 02:20:03 start squeeze Rdiger Schmidt 02:36:20 end squeeze 02:43:01 end adjust Beam losses ~5%

LHC - challenges in handling beams exceeding 136 MJ page 39 CERN August 2012, Fill 2993, 4 TeV, 2012, 1374 bunches 12.8 MJoule 05:47:18 end adjust 05:16:39 end ramp 05:23:13 start squeeze 05:39:55 end squeeze Beam losses >5% Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 40

CERN ATLAS Experiment beam losses before bringing beams into collisions ALICE Experiment Rdiger Schmidt Momentum Cleaning RF and BI CMS Experiment Beam dump LHC - challenges in handling beams exceeding 136 MJ Betatron

Cleaning LHCb Experiment page 41 41 CERN ATLAS Experiment beam losses when bringing beams into collisions ALICE Experiment Rdiger Schmidt Momentum Cleaning RF and BI CMS

Experiment Beam dump LHC - challenges in handling beams exceeding 136 MJ Betatron Cleaning LHCb Experiment page 42 42 CERN ATLAS Experiment beam losses after bringing beams into collisions ALICE Experiment Rdiger Schmidt

Momentum Cleaning RF and BI CMS Experiment Beam dump LHC - challenges in handling beams exceeding 136 MJ Betatron Cleaning LHCb Experiment page 43 43 CERN Fill 2602, also a typical fill in 2012.

21:57:33 start adjust 21:37:59 end ramp Rdiger Schmidt 22:07:15 end adjust 21:41:24 start squeeze LHC - challenges in handling beams exceeding 136 MJ page 44 Bunch loss pattern for fill 2593 CERN

Typical beam loss pattern no all bunches are affected in the same way (e.g. few bunches that are not colliding) Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 45 CERN Operating closer to the limits Initially, the BLM thresholds were set to dump the beams when the beam power loss exceeded about 50 kW By gaining experience we observed that the cleaning worked very well and there was no risk to quench magnets

The thresholds of the BLMs for beam losses in the range of few seconds was increase, to allow for beam power losses of up to 200 kW This has been done for slow beam losses, with time constants of about one second and more There is still some margin, the power deposition in the collimation insertion can go up to a value between 500 kW 1 MW Rdiger Schmidt Beam losses at LHC and its injector, Laurette Ponce (CERN, Geneva) Colliding High Brightness Beams in the LHC, Tatiana Pieloni (CERN, Geneva) LHC impedance model: experience with high intensity operation in the LHC, Benoit Salvant (CERN, Geneva) Quench tests at the LHC with collimation losses at 3.5 TeV, Stefano Redaelli (CERN, Geneva) LHC - challenges in handling beams exceeding 136 MJ page 46 CERN

An object falls into the beam Detection of 'unidentified falling objects' at LHC, Eduardo Nebot Del Busto (CERN, Geneva) Bunch to Bunch Diagnostics with Diamond Detectors at the LHC, Maria Hempel (BTU, Cottbus) Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 47 CERN ATLAS Experiment Rdiger Schmidt Accidental beam losses during collisions ALICE Experiment CMS Momentum

RF and Beam Experiment Cleaning BI LHC - challenges in handling beams exceeding 136 MJdump Betatron Cleaning page 48 LHC Experiment 48 CERN Zoom one monitor: beam loss as a function of time 1 ms Beam dump (7 beam dumps in stable beams due to UFOs in 2012) Rdiger Schmidt

LHC - challenges in handling beams exceeding 136 MJ page 49 CERN Final remarks Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 50 CERN What else? Longitudinal beam dynamics excellent performance of the RF system Performances and future plans of the LHC RF, Philippe Baudrenghien (CERN, Geneva) Batch-by-batch longitudinal emittance blow-up in the LHC, Philippe Baudrenghien (CERN, Geneva) Measurements of the LHC longitudinal resistive impedance with beam, Juan Esteban Muller (CERN, Geneva) Excellent performance of the transverse damper (feedback)

Fighting transverse instabilities Damping injection oscillations Cleaning of beam abort gap Produce beam losses on selected bunches for validation of cleaning hierarchy Measuring betatron tunes Swiss German animal: Eierlegendewollmilchsau Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 51 CERN What we learned.. High-intensity operation close to beam instability limits Established * reach (aperture, collimation, optics) Luminosity levelling via offset tested works fine in LHCb! Head-on beam-beam effect is not a limitation Long range beam-beam effects have to be taken seriously

As small as possible emittances are good Instabilities were observed and to some extent understood Need separation of 10 -12 (otherwise bad lifetime and beam loss) For small beam offsets at collision point while going into collisions, . Impedances (kicker, collimator heating), collective effects, ... Availability of such ultra-complex machine Single Event Upsets, vacuum pressure increase, UFOs, cryogenics, magnet protection system, .. Vigorous follow-up and consolidation Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ

page 52 LHC Operation after the shutdown 2013/14 CERN Energy 6.5 TeV during 2015 Bunch spacing 25 ns (in case of problem fall back to 50 ns) Beta-function at experiments ~0.5 m Pile-up of events in the experiments assume acceptable Performance could be impacted by

Depends on bunch spacing and squeeze beyond 0.5 m Beta* luminosity-levelling to mitigate the initial large pile-up UFOs at higher energy and with 25 ns bunch spacing Radiation to electronics SEUs Electron cloud & high energy & at 25 ns Long-range beam-beam & smaller crossing angle & at 25 ns Single- and bunch-by-bunch beam instabilities (impedances...) It should be possible to achieve nominal luminosity of 1034 [cm-2s-1] or more Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 53 Summary CERN Operation in 2012 is at 4.0 TeV In 2012 the peak luminosity exceeded 7.5x1033 cm-2s-1 in ATLAS and CMS with beams of 50 ns spacing

The stored energy of the beams exceeded by a factor ~50 that of existing or previous machines No beam induced magnet quench with stored beams Integrated luminosity for 2012 is in excess of 14 fm-1, hope to reach more than 20 fm-1 until the end of the run in February 2013 The consolidation of the splices between magnet will be done in 2013/14 , to restart autumn 2014/ 2015 at about 6.5 TeV UFOs could become a limitation for the availability of LHC at 6.5 TeV Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 54 CERN Reserve slides Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ

page 55 CERN Thanks for your attention Rdiger Schmidt LHC - challenges in handling beams exceeding 136 MJ page 56

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