Ralph Assmann Collimation Project R. Assmann, CERN 26/4/2010 CERN Machine Advisory Committee

Outline 1.The phased approach for LHC collimation 2.LHC Design and Beam Experience 3.Completing/Upgrading/Improving LHC Collimation 4.Schedule 5.Estimated performance evolution 6.Resources 7.Conclusion Ralph Assmann 2

3 1. The Phased LHC Collimation Solution (Defined in 2004) Phase I (initial installation): –Relying on very robust collimators with advanced but conservative design. –Perceived to be used initially (commissioning) and always in more unstable parts of LHC operation (injection, energy ramp and squeeze). –Provides excellent robustness and survival capabilities. –OK for ultimate intensities in experimental insertions (triplet protection, physics debris), except some signal acceptance. –Limitations in efficiency (betatron & momentum) and impedance. –Demanding R&D, testing, production and installation schedule over 6 years. Phase II (upgrade for nominal/ultimate intensities): –Upgrade for higher LHC intensities, complementing phase I. –To be used in stable parts of operation like physics (robustness can be compromised). –Fixes limitations in efficiency, impedance and other issues. R. Assmann, CERN

The LHC Collimation Challenge R. Assmann, CERN 4 less than 1%new territory survive At less than 1% of nominal intensity LHC enters new territory. Collimators must clean unavoidable losses and survive expected beam loss… LHC quench limits: 5-30 mJ/cm 3 LHC quench limits: 5-30 mJ/cm MJ RHIC

5 Allowed intensity Quench threshold (7.6 × TeV) Loss length Cleaning inefficiency = Number of escaping p (>10  ) Number of impacting p (6  ) Beam lifetime (e.g. 0.2 h minimum) limit the intensity luminosity Collimation performance can limit the intensity and therefore LHC luminosity. Illustration of LHC dipole in tunnel Required Cleaning Efficiency BLM threshold (e.g. 30%) R. Assmann, CERN

The Phase I Collimator R. Assmann, CERN MJ proton beam 1.2 m 3 mm beam passage with RF contacts for guiding image currents Designed for maximum robustness: Advanced CC jaws with water cooling! Mostly with different jaw materials. Some very different with 2 beams! Other types: Mostly with different jaw materials. Some very different with 2 beams!

Multi-Stage Cleaning & Protection R. Assmann, CERN 7 Secondary halo p p e  Primary collimator Core Unavoidable losses Shower Beam propagation Impact parameter ≤ 1  m Primary halo (p) e  Shower p Tertiary halo Secondary collimator Without beam cleaning (collimators): Quasi immediate quench of super- conducting magnets (for higher intensities) and stop of physics. Required cleaning efficiency: always better than 99.9%. Absorber CFC W/Cu Absorber Super- conducting magnets SC magnets and particle physics exp.

2. LHC Design and Experience Most important collimation design parameters: –Cleaning efficiency. Experience: as expected –Peak loss rate of stored beam: Experience: varying, not fully optimized yet, intensity 10,000 times below nominal. –LHC quench limit. Experience: close to but not better than design. –BLM thresholds. Experience:as expected but with some problematic cases. Performance and requirements depend on design parameters and input parameters. Things might become more shaky with higher intensities. So far, no reason seen to change approach. R. Assmann, CERN 8

Beam Lifetime in Early LHC Operation Insufficient experience and not yet optimized operation. Intensity 10,000 times below nominal intensity  validity? However, easily find cases with specified minimum lifetime (can also find periods with lifetimes above 200 h)… Ralph Assmann 9 LHC design maximum peak loss: 0.1 %/s  0.2 h lifetime

Measured Cleaning at 3.5 TeV (beam1, vertical beam loss, intermediate settings) LPCC, R. Assmann IR8 IR1 IR2 IR5 Momentum Cleaning Dump Protection Col. 2m optics exposes IR’s as expected! Protected by tertiary collimators. 10

Simulated Cleaning at 3.5 TeV (beam1, vertical beam loss, intermediate settings) Ralph Assmann 11

Measured Cleaning at 3.5 TeV (beam1, vertical beam loss, intermediate settings) LPCC, R. Assmann factor 1,000 factor 4,000 Betatron Cleaning IR8 factor 600, Cleaning efficiency: > %

Simulated Cleaning at 3.5 TeV (beam1, vertical beam loss, intermediate settings) Ralph Assmann 13 factor 33,000

Meas. & Sim. Cleaning at 3.5 TeV (beam1, vertical beam loss, intermediate settings) LPCC, R. Assmann IR8 14 IR7 Confirms expected limiting losses in SC dispersion suppressor

Origin of Losses in Dispersion Suppressor Effect understood and predicted as early as Collimators in straight sections “generate” off-momentum p and ions (effectively). Off-momentum particles pass through straight sections and are deflected by first dipoles in dispersion suppressors. Downstream magnets act as off- momentum halo beam dump. SC regions off-hands: Impossible to put collimators in dispersion suppressors (as in LEP). Clear physics sources: p have single-diffractive scattering in matter, ions dissociate/fragment! Now confirmed by experimental data (also in horizontal plane). Loose factor ~10 with non- smooth aperture (alignment)! Ralph Assmann 15

16 better worse R. Assmann, CERN Nominal LHC design intensity Prediction: Intensity Limit vs Loss Rate 7 TeV Settings primary/secondary collimators: Tight: 6/7 . Intermediate: 6/10 

3. Completing/Upgrading/Improving LHC Collimation Ralph Assmann 17 Part. type Coll. Effi- ciency Impe- dance Luminosity losses Opera -tional eff. Rad. to electro- nics Radia- tion handling Losses in experimen- tal IR’s IR1/5: TCLP p > 5×10 33 IR2: new TCT p, PbZDC acce- ptance IR2: TCRYO Pb > 4×10 26 IR3: TCRYO p, Pb × 15 (?) × 0.01 IR3: combined p × 0.5 × 0.01 IR6: new TCLA p × 3 IR7: TCRYO p, Pb × 15 × 0.01 IR7: warm upgrade p × 0.5 × 0.01 Automatic Set- up p, Pb

Part. type Coll. Effi- ciency Impe- dance Luminosity losses Opera -tional eff. Rad. to electro- nics Radia- tion handling Losses in experimen- tal IR’s IR1/5: TCLP p > 5×10 33 IR2: new TCT p, PbZDC acce- ptance IR2: TCRYO Pb > 4×10 26 IR3: TCRYO p, Pb × 15 (?) × 0.01 IR3: combined p × 0.5 × 0.01 IR6: new TCLA p × 3 IR7: TCRYO p, Pb × 15 × 0.01 IR7: warm upgrade p × 0.5 × 0.01 Automatic Set- up p, Pb Completing/Upgrading/Improving LHC Collimation Ralph Assmann 18 Complicated plan and it is not easy to see in detail what we do where for what reason… Did not find a better way to show a simplified but correct picture that makes it clear (things are just complex). Sorry… For each action there is a clear reason and I am happy to explain it in detail. Just ask me… Complicated plan and it is not easy to see in detail what we do where for what reason… Did not find a better way to show a simplified but correct picture that makes it clear (things are just complex). Sorry… For each action there is a clear reason and I am happy to explain it in detail. Just ask me…

19 a) “Warm” Upgrade: Advanced Secondary Collimators for IR3 and IR7 Will not very much improve the cleaning efficiency. However, will implement other important improvements: –Reduction in impedance. –Non-invasive and fast collimator setup with BPM buttons in jaw. –Improvement of lifetime for warm magnets in cleaning insertion by factor ~3. –Improvement of lifetime for phase I collimators as radiation load is spread over phase I and phase II collimators. –Remote handling. –Radioactive air handling. Design and prototyping has started. Material will be decided based on LHC beam experience: either Cu or ceramics or advanced composites. Will not ensure collimator robustness but may include rotatable solution for handling many damages in-situ. R. Assmann, CERN

Prepared, Empty Secondary Collimator Slots for Phase 2 EMPTY PHASE II TCSM SLOT (30 IN TOTAL) PHASE I TCSG SLOT 1 st advanced phase 2 collimator CERN SLAC design

-3 m shifted in s halo Halo Loss Map Upgrade Scenario +3 m shifted in s Downstream of IR7  -cleaning transversely shifted by 3 cm cryo-collimators NEW concept Losses of off-momentum protons from single-diffractive scattering in TCP without new magnets and civil engineering b) TCRYO

Phase 1 Phase 2 Gap × 1 × 1.2 × 1.5 × 2 Ideal Inefficiency [1/m] Impedance better Collimation Solution: Scenario 1 for 7 TeV (Baseline) Small nominal gaps, tight operational tolerances achieved. Efficiency gain (factor 15-90) with collimation phase 2. Beam is stabilized by octupoles + transverse feedback or high chromaticity. 22 Acceptable Area with Transverse Feedback Stabilization R. Assmann T. Weiler E. Metral Target Inefficiency (nominal intensity, design peak loss rate) Impedance Target Phase 1 (full octupoles, no transv. feedback, nominal chromaticity) Impedance Target Phase 2 (full octupoles, no transv. feedback, nominal chromaticity) Installation of collimation phase II including collimators in cryogenic dispersion suppressors WARNING: Grid simulation here for non- nominal optics and perfect machine! Phase 1: ~ 20 times higher inefficiency for nominal optics and design imperfections! Phase 2: Expect less sensitivity to imperfections (factor 2-4 higher inefficiency? – simulation required). WARNING: Grid simulation here for non- nominal optics and perfect machine! Phase 1: ~ 20 times higher inefficiency for nominal optics and design imperfections! Phase 2: Expect less sensitivity to imperfections (factor 2-4 higher inefficiency? – simulation required).

Phase 1 Phase 2 Gap × 1 × 1.2 × 1.5 × 2 Ideal Inefficiency [1/m] Impedance better Collimation Solution: Scenario 2 for 7 TeV (Backup) Beam cannot be stabilized (octupoles + transverse feedback or high chromaticity) or limited in achievable gap size from operation. Increase gaps: Impedance reduced and relaxed tolerances. 23 Acceptable Area R. Assmann T. Weiler E. Metral Target Inefficiency (nominal intensity, design peak loss rate) Installation of collimation phase II including collimators in cryogenic dispersion suppressors WARNING: Grid simulation here for non- nominal optics and perfect machine! Phase 1: ~ 20 times higher inefficiency for nominal optics and design imperfections! Phase 2: Expect less sensitivity to imperfections (factor 2-4 higher inefficiency? – simulation required). WARNING: Grid simulation here for non- nominal optics and perfect machine! Phase 1: ~ 20 times higher inefficiency for nominal optics and design imperfections! Phase 2: Expect less sensitivity to imperfections (factor 2-4 higher inefficiency? – simulation required). Increase gaps by factor 1.5 Nominal I. Larger triplet/IR aperture or lower  * Impedance Target Phase 1 (full octupoles, no transv. feedback, nominal chromaticity) Impedance Target Phase 2 (full octupoles, no transv. feedback, nominal chromaticity)

What Does it Mean? Constructing ~60 additional collimators for warm and cold regions: –advanced secondary collimators (CERN standard design, CERN/SLAC advanced design in prototyping phase) –collimators in cryogenic regions (preliminary design starting). Constructing hollow e-beam lenses for scraping (wait for Tevatron results). Can mostly rely on already prepared infrastructure (cables, replacement vacuum chambers, supports, water connections, …). However, have to prepare infrastructure for some locations. Remote handling, radioactive air handling, absorber masks, preventive replacement of ageing components, … How to get into SC dispersion suppressor: –Shorter magnets with space for movable collimators. Discussed since years. – As long as not available: Reshuffle magnets to make space (24 magnets/IR). Ralph Assmann 24

Intermediate Step: First IR3… If only one IR can be upgraded with cryogenic collimation in 2012, then we prefer IR3 to be done first. Why: –IR3 can be used to implement a combined betatron and momentum cleaning system (memo R. Assmann in 7/2008). Use prepared, empty phase 2 slots. –While we loose efficiency with the combined system, we win with the collimators in the cryogenic dispersion suppressors. Maybe we can get already nominal (simulations ongoing)… –SC link cable in IR3 OK for 500 kW losses at primary collimators (nominal). Maybe require additional passive absorbers. –LHC collimation with 28 collimators less than now  faster setup and less beam time required. Lower impedance (20 TCP/TCS instead of 38 TCP/TCS)! –Limitations with SEE/SEU in IR7 are avoided as losses are relocated to IR3 (100 times less radiation to electronics for same beam loss in IR3). –System in IR7 kept operational in case of problems (spare system). –Much better flexibility to react to limitations. R. Assmann, CERN 25

IR3 Performance with Combined System + TCRYO (Preliminary): Vertical Betatron Cleaning Ralph Assmann 26 Vertical plane worse than horizontal! Insensitive to aperture steps, as these are shadowed by TCRYO. Almost good for nominal performance… Further optimization required. Vertical plane worse than horizontal! Insensitive to aperture steps, as these are shadowed by TCRYO. Almost good for nominal performance… Further optimization required. TCRYO Primary collimator factor 50,000 Nominal goal Shift 2 nd TCRYO to the left!? Blue losses must be below quench limit lines (“nominal goal”).

4. Schedule I - Discussions After Chamonix Ralph Assmann 27 Review 1 Review 2 Mid-2010 review will decide whether this schedule is indeed achievable…

Schedule II - Discussions After Chamonix Ralph Assmann 28 Review 1 Review 2 Review 3

Remarks General goal: Ensure collimation readiness for handling nominal and ultimate beam intensity. Starting now: Readiness between 2016 and 2018, for nominal proton and nominal ion running! Plan will be adapted to further lessons with beam, while the system is being improved. Reviews will be done at critical phases in the project: –Maybe IR3 work alone can carry us to nominal/ultimate intensity  no upgrade required of IR7. –Maybe beam losses are more/less severe than assumed  adapt solution and schedule. –Maybe collimation for luminosity driven losses is more/less important than assumed  adapt solution and schedule. –Maybe more/less radiation load to IR7  assess need and urgency of remote handling and air bypass in IR7. Ralph Assmann 29

5. Estimated Performance Evolution YearIntensity ReachFraction of nominal intensity Year Present installation3e13 p10 %now IR3 combined cleaning + TCRYO 2e14 p70 %2013/14 or 2015/16 Full upgrade1e15 p1,000 %2015/16 or 2017/18 Ralph Assmann 30 Assumes nominal maximum beam loss rate and stabilization of beams with large impedance through transverse damper. PRELIMINARY

6. MTP from Collimation Assume that the full collimation program must be implemented. This includes remote handling and air-bypass in IR7 (but excludes R2E). Numbers are bottom-up approach: WP’s defined and estimates from groups collected. Numbers are for fast approach ( ) and are broken down per year. All work assumed in-house. Resources looked into: M, P(staff), P(fellow) No effort yet to reduce cost. Groups have good experience with the required work. Industrial production can reduce cost. P resources are required resources and do not mean that resources are available. Industrial production can reduce P resources. Split available/needed remains to be done. Thanks to EN/STI, TE/MS, TE/CRG, BE/ABP, BE/BI, EN/HE, DGS/RP, EN/MME, BE/OP, EN/MEF, EN/CV, TE/VSC. Ralph Assmann 31

MTP Ralph Assmann 32 DepGroupWPType Sum I Sum IISum allCost [MCHF] Staff [FTE] Fellow [FTE] ENSTIControlsM [MCHF] ENSTIControlsP [FTE] - staff ENSTIControlsP [FTE] - fellow ENSTIMechanicsM [MCHF] ENSTIMechanicsP [FTE] - staff ENSTIMechanicsP [FTE] - fellow ENSTIFLUKAM [MCHF]0.000 ENSTIFLUKAP [FTE] - staff ENSTIFLUKAP [FTE] - fellow TEMSCSC ModificationM [MCHF] TEMSCSC ModificationP [FTE] - staff TECRGCryoM [MCHF] TECRGCryoP [FTE] - staff BEABPAlignmentM [MCHF] BEABPAlignmentP [FTE] - staff BEABPStudyM [MCHF] BEABPStudyP [FTE] - staff BEABPStudyP [FTE] - fellow BEBIInstrumentationM [MCHF] BEBIInstrumentationP [FTE] - staff ENHEInstallationM [MCHF] ENHEInstallationP [FTE] - staff ENHERemote handlingM [MCHF] ENHERemote handlingP [FTE] - staff DGSRPRadiation protectionM [MCHF] DGSRPRadiation protectionP [FTE] - staff ENMMEMech engineeringM [MCHF] ENMMEMech engineeringP [FTE] - staff ENMMEMech engineeringP [FTE] - fellow ENMMEProduction Type Phase 1M [MCHF] ENMMEProduction Type Phase 1P [FTE] - staff ENMMEProductionM [MCHF] ENMMEProductionP [FTE] - staff BEOPControlsM [MCHF] BEOPControlsP [FTE] - staff0.000 BEOPControlsP [FTE] - fellow TEVSCVacuumM [MCHF] TEVSCVacuumP [FTE] - staff TEVSCVacuumP [FTE] - fellow ENMEFIntegration & planningM [MCHF] ENMEFIntegration & planP [FTE] - staff ENMEFIntegration & planP [FTE] - fellow0.000 ENCVCooling & ventilationM [MCHF] ENCVCooling & ventilationP [FTE] - staff ENCVCooling & ventilationP [FTE] - fellow0.000 Exter nal Kurchatov CollaborationM [MCHF] Total

Collimation MTP Summary Ralph Assmann 33

7. Conclusion Collimation performs as expected  efficiency > 99.97%. Predicted leakage is confirmed with beam. Major uncertainty: magnitude of losses with high intensity, 7 TeV beams. Assume design. Start collimation work now to be fully ready in Decision 8/2010. Intensity steps: First factor ~7 (IR3) and then factor ~100 wrt now. Intermediate step (IR3) also 100 times lower radiation to electronics! Many additional benefits: catch luminosity debris, less radiation to warm+SC magnets, lower losses in experimental IR’s, radiation handling, … Work packages defined, project structure agreed, MTP info collected. Required collimation upgrade resources: ~14 MCHF/y and 50 FTE/y: –First step ( ):26 MCHF FTE + 27 FTE fellow –Full cost ( ):73 MCHF FTE + 56 FTE fellow –Phase 1 cost (2002-9):35 MCHF FTE Industrial contracts can bring down manpower (cost? phase 1 company is out!). Ralph Assmann 34

Collimation Phase 2 Project CERN Project Leader (R. Assmann) Energy deposition A. Ferrari (EN/STI) Electronics, sensors, actuation A. Masi (EN/STI) Vacuum issues M. Jimenez & V. Baglin (TE/VSC). Machine protection & beam tests R. Schmidt (TE/MTE) Beam instru- mentation B. Dehning (BE/BI) Remote & Installa- tion tools K. Kershaw (EN/HE) Mechanical engineering, lab tests, prototyping, production A. Bertarelli (EN/MME) Controls, Operation S. Redaelli (BE/OP) Install., mainte- nance, beam test support O. Aberle (EN/STI) Final assembly on surface O. Aberle (EN/STI) Tunnel and beamline activities Design, prototyping and production (above surface) Performance studies, simulations and beam tests Project Engineer for tunnel & beamline activities (O. Aberle) Project Engineer for coll. design, lab. tests, prototyping (A. Bertarelli) Radiation aspects S. Roesler (DG/SCR) Cryo interface J.P. Tock (TE/MSC). LARP/SLAC Phase 2 Collimator Work T. Markiewicz, SLAC EuCARD collaboration for collimators & materials (FP7) R. Assmann (CERN), J. Stadlmann (GSI) Ion loss issues J. Jowett (BE/ABP) Crystal Collimation Tests at SPS & Tevatron UA9: W. Scandale T980: N. Mokhov participate in collaboration Simula- tions, beam tests R. Assmann E. Metral A. Rossi (BE/ABP) Note: Phase 1 collimation project still active until end of system commissioning. In practice integrated with Phase 2! Cryo Line Responsibility & Follow-Up TE/MSC Group

The End Ralph Assmann 36