First look at collimation in cold regions around

First look at collimation in cold regions (around IR's) R. W. Assmann, G. Bellodi, R. Bruce, J. Jowet, L. Lari, S. Redaelli, A. Rossi, T. Weiler, D. Wollmann 1 st Hi. Lumi / LARP collaboration meeting 17 November 2011

Outline n n n n The LHC collimation system Collimation efficiency Leaks in DS regions for protons and ions Interim conclusions Origin of losses Improving collimation efficiency Studies made so far Summary and conclusions A. Rossi Preliminary Meeting on Interface 11 T - Cold Collimation, 05. 10. 11 2

Layout of LHC collimation system Two warm cleaning insertions, 3 collimation planes IR 3: Momentum cleaning per beam 1 primary (H) 4 secondary (H) 4 shower abs. (H, V) IR 7: Betatron cleaning per beam 3 primary (H, V, S) 11 secondary (H, V, S) 5 shower abs. (H, V) Local cleaning at triplets 8 tertiary (2 per IP) per beam Passive absorbers for warm magnets Momentum cleaning Betatron cleaning Physics debris absorbers Transfer lines (13 collimators) Injection and dump protection (10) Total of 108 collimators (100 movable). Two jaws (4 motors) per collimator! Picture by C. Bracco 3

Collimation for beam cleaning and machine protection Betatron cleaning insertion n Three-stage cleaning system for the protection of the arc cold aperture at injection. n At collision machine bottleneck at superconducting triplets. Tertiary collimators closed (four-stage cleaning system). Horizontal (TCTH) and vertical (TCTV) tertiary collimators are installed upstream of the triplet magnets to provide protection during squeeze and collision. The halo leakage to cold aperture must be below quench limit! Courtesy of C. Bracco for injection and collision (7 Te. V)

Collimation for beam cleaning and machine protection R. Bruce IPAC’ 11 Betatron cleaning insertion β* 3. 5 m β* 1 m β* 0. 55 m n Primary and secondary collimators are robust (Carbon-based). For Hi. Lumi secondary collimator in metal-diamond (higher absorption, lower impedance). n Absorbers and tertiary collimators (Tungsten) are not and must be protected.

The Phase I Collimator 1. 2 m 3 mm beam passage at top energy, with RF contacts for guiding image currents Tunnel inbeam IP 2) 360 MJ proton 1. 4 m total length, flange to flange Water cooling system (capacity for 420 k. W in IR 7 installation (TCT and 160 k. W in IR 3). 6

Typical geometry (here hor TCT) W Jaws Maximum energy deposition for W plastic deformation (one shot) 480 J/cm 3≈ 1 E 9 p+ (5 Te. V*) *Extrapolated Water cooling pipes from V. Kain’s talk at Chamonix 2009, for a squeezed beam Joint LBS & LPC meeting 18 January 2010

Collimation measured performance n Local cleaning efficiency § Ntotal = Total no. of particles leaving the cleaning insertion with a normalised amplitude > A in Ds § Nabs = Total no. of particles undergoing inelastic interactions and being absorbed at collimators 2010 -2011 Efficiency at Q 8 downstream IR 7 at 3. 5 Te. V, B 1 and B 2 Measured with loss maps (losses at BLM when blowing the beam) 10 -3 99. 960 % 10 -4 99. 995 % 8

Losses during physics, 1308 b nom. at 3. 5 Te. V • Losses in DS of experimental Regions could become limiting IR 5 lumi mom-clean. intensity IR 1 lumi IR 2 lumi A. Rossi -clean. intensity IR 8 lumi dump protection 9

Losses during physics, 1308 b nom. at 3. 5 Te. V Zoom in IR 7: betatron losses -clean. A. Rossi 10

Losses during physics, 1308 b nom. at 3. 5 Te. V Parameter Fill #2156, 3. 5 Te. V 7 Te. V HL-LHC scaled Luminosity 0. 296 × 1034 cm-2 s-1 2 × 1035 cm-2 s-1 Loss @ BLM 2. 1 × 10 -5 Gy/s 2. 8 × 10 -3 Gy/s Limit @ BLM 5 × 10 -4 Gy/s ~3 × 10 -4 Gy/s - Does not include significant loads from ion operation. - Does not include effect of * Zoom in IR 5: luminosity losses TAN TAS A. Rossi | MBWX | 11

Global view of losses, Pb-Pb stable beams Record luminosity, the last fill of 2010 208 Pb 81+(BFPP Momentum collimation: 208 Pb 82+ (IBS) 207 Pb 82+ (EMD 1) at ATLAS) 208 Pb 81+(BFPP at ALICE) G. Belodi - LHC Collimation Review 2011 208 Pb 81+ BFPP at CMS Betatron collimation: 206 Pb 82+ (EMD 2 in TCP) + many other nuclides from hadronic fragmentation and EMD in TCPs Possibly: 206 Pb 82+ (EMD 2 at IPs), other nuclides from collimation ? ? 14/06/2011 J. M. Jowett, Chamonix 2011

Interim conclusions n The present collimation system works very well. Reached 99. 995% collimation efficiency with 50% smaller gaps than design. n It is predicted to work for proton nominal intensity (Collimation review June 2011), and for ions? n HL-LHC requires catching losses in the DS regions. Even if such losses do not quench the magnets, they may cause damage if permanently close to quench limit. n DS collimators are needed in 5 Interaction Regions for: IR 1 and IR 5 for proton luminosity ¨ IR 2/1/5 for ion luminosity ¨ IR 3/7 for proton and ion intensity ¨ Priority: DS 1 – 2 – 5 then 3 – 7 then 8 ¨ A. Rossi 13

Collimator Origin of Losses in Dispersion Suppressor Warm cleaning insertion (straight line) Off-momentum particles generated by particle-matter interaction in collimators and by collision at IPs (proton single diffractive scattering, and ion dissociation/fragmentation) pass thorough LSS SC bend dipole (acts as spectrometer) SC quad for p, and dipoles for ions (hit by halo) Ideal orbit (on momentum) Already predicted in 2003 R. Assmann, T. Weiler, 2003

Improving Collimation Efficiency n Collimator n Reduce number of off-momentum protons produced (phase 2 primary and secondary collimators, with higher absorbtion). Does not work for ions. Install collimators into SC area, just before loss locations to catch off-momentum particles before they get lost in SC magnets. Add collimator, using space left by missing dipole Warm cleaning insertion (straight line) SC bend dipole (acts as spectrometer) SC quad Ideal orbit (on momentum)

Example 1 studied: protons n DS 3 -7 collimators (present solution at RT) Beam 1 Q 7 MB MB TCRYOA Q 8 MB MB Q 9 MB MB TCRYOB Q 10 MB MB Q 11 Tungsten collimators in front of Q 8 and Q 10 to catch off momentum particles (from Single Diffractive scattering at collimators, from collisions …) at high dispersion regions. ¨ Layout and optics checked with MADX. No problem for the optics and survey seen. Optics change (move of Q 7) small even without optics rematch. ¨ Space assumed for two 2 -sided (for ions), 1 mx(20 x 34)mm W jaw insert, with tapering (10 cm per side), RF fingers, cooled for 500 W (ions) ¨ A. Rossi Collimation Upgrade Review 2011 16

IR 3 Dispersion Suppressor Collimator Beam vacuum sector valves Manual quick connect flanges, electrical and water plugs, but Standard interconnects Collimator not remote handling Bypass cryostat BLM’s “Standard” baked vacuum sector Collimator with independent support/alignment A. Dallocchio 17 Collimator replacement without re-alignment June 14, 2011

Zoom into DS downstream of IR 7 quench level T. Weiler Impact pattern of protons on DS collimator 1 R. Assmann - HHH 2008 Impact pattern of protons on DS collimator 2

Example 2 studied: IR 2 solutions for ions Collimators in dispersion suppressors around experiment(s) will be needed to overcome luminosity (not intensity) limit for Pb-Pb collisions. 19 Optimal position for one “DScollimator/beam. J. M. Jowett, LHC Performance Workshop, Chamonix 27/1/2011

Summary and conclusions n The present collimation system works very well. Reached 99. 995% collimation efficiency with 50% smaller gaps than design. n Present system is predicted to work for nominal LHC proton intensity, but for ions? n BUT there are still losses in the DS regions due to off-momentum particles that go through the LSS and are caught at SC magnets. This is a basic limitation coming from physics processes. n DS collimators (1 m active tungsten jaw) have been shown to solve this limit (factor of 15 improvement in cleaning efficiency, also confirmed by FLUKA) n HL-LHC needs DS collimators in 5 Interaction Regions for: IR 1 and IR 5 for proton luminosity ¨ IR 2/1/5 for ion luminosity ¨ IR 3/7 for proton and ion intensity ¨ Priority: DS 1 – 2 – 5 then 3 – 7 then 8 ¨ A. Rossi Preliminary Meeting on Interface 11 T - Cold Collimation, 05. 10. 11 20

BACKUP slides A. Rossi 21

Betatron losses fully confirmed B 1 Simulations: perfect machine, B 1 vertical, 3. 5 Te. V, IR 7 superimposed on Betatron loss maps Intermediate settings Q 7 Q 8 Q 10 Q 9 Q 11 Tight Settings 99. 995% efficiency with tight settings When will they quench ? Q 7 Q 8 Q 10 Q 9 Q 11 A. Rossi Preliminary Meeting on Interface 11 T - Cold Collimation, 05. 10. 11

Ions: Beam 2 Leakage from IR 7 Collimation (much worse than for protons, as expected) Level simulated RWA 6/14/11

Ion commissioning loss maps vs simulation – Nov 2010 DS COLD TCT B 1 H B 1 h 0. 02 0. 006 1. 0 × 10 -4 B 1 v 0. 027 0. 005 0. 001 B 2 h 0. 03 0. 011 8× 10 -5 B 2 v 0. 025 0. 006 1. 4× 10 -4 B 1+B 2 pos. off mom 0. 045 8 e-4 0. 06 B 1+B 2 neg. off mom 0. 007 2 e-4 0. 005 14/06/2011 G. Bellodi - LHC Collimation Review 2011

DS collimator designed for IR 3 Collimator Module Cryo-bypass A. Dallocchio 25 June 14, 2011

Simulation results for IR 3 combined cleaning, vertical B 1 BLM threshold after MD Cleaning inefficiency without DS collimator. Simulation for ideal machine, 7 Te. V, vertical A. Rossi Preliminary Meeting on Interface 11 T - Cold Collimation, 05. 10. 11 26

Simulation results for IR 3 combined cleaning, vertical B 1 Cleaning inefficiency without DS collimator. Simulation for ideal machine, 7 Te. V, vertical A. Rossi Preliminary Meeting on Interface 11 T - Cold Collimation, 05. 10. 11 27

Cleaning inefficiency with DS collimators B 1 IR 3 combined cleaning for ideal machine with DS collimator at 15 s, 7 Te. V, vertical A. Rossi Preliminary Meeting on Interface 11 T - Cold Collimation, 05. 10. 11 28

Cleaning inefficiency with DS collimators B 1 Zoom in IR 3 Calculations including alignment imperfections show a worsening in the vertical plane only by max. a factor of ~ 7. 5 (average 4. 5) A. Rossi Preliminary Meeting on Interface 11 T - Cold Collimation, 05. 10. 11 29

Cleaning inefficiency with machine alignment imperfections RMS offsets (measured) in the horizontal and vertical planes defined for families of elements. DS collimator at 15 s. 7 Te. V, vertical sheet beam 1, Studies with aperture imperfections Performance worsen by max. a factor of ~ 7. 5 (average 4. 5) in the vertical plane, ~ 2 (average 0. 7) in the horizontal plane (over 10 cases studied) A. Rossi 30

IR 3 combined cleaning for ions Without TCRYO Sector Family Half gap LSS 7 TCP IR 7 Open TCSG IR 7 Open TCLA IR 7 open TCP IR 3 6 TCSG IR 3 7 TCLA IR 3 10 TCTH 8. 3 TCTV 8. 3 LSS 1/2/5/8 t=12 min lifetime 7× 107 × 592= 4. 14× 1010 ions E=7 Z Te. V eq. Max TCP load ~ 4500 W Peak loss in DS 3 ~ 20 W/m h (local) = 0. 0044 With TCRYO 14/06/2011 G. Bellodi - LHC Collimation Review 2011

Fill 2156: proton beam - physics Ramp and collision Loss maps Increase due to increasing lumi in IP 1 Tune trim of +0. 001 on beam 2 H A. Rossi Preliminary Meeting on Interface 11 T - Cold Collimation, 05. 10. 11 32

p – C Interaction: Multiple Coulomb & Single-Diffractive Scattering 6/14/11

Monte-Carlo Simulation of Realistic Beam Halo and Interactions 6/14/11