1. R. Assmann, June 2009 Operational Experience with the LHC Collimation System R. Assmann, CERN 8/6/2009 for the Collimation Project Team Visit TU Munich R. Assmann, CERN 8/6/2009 for the Collimation Project Team Visit TU Munich Operational Experience with the LHC Collimation System LHC Collimation Some personal info: At CERN since 1998. Senior Physicist in the CERN Beams Department. Project leader LHC collimation. Post-doc (1994) and physicist (1997) at SLAC, Stanford University. Dipl. Phys. (1991) and Dr. rer. nat. (1995) at LMU (MPI f. Physik). Some personal info: At CERN since 1998. Senior Physicist in the CERN Beams Department. Project leader LHC collimation. Post-doc (1994) and physicist (1997) at SLAC, Stanford University. Dipl. Phys. (1991) and Dr. rer. nat. (1995) at LMU (MPI f. Physik).

2. The LHC LHC is a storage ring and collider at the technical frontier of accelerator science: –Two counter-rotating beams with each 3 × 10 14 protons stored into the 27 km long ring and accelerated to 7 TeV/c particle momentum. –Protons circulate with light velocity, 11,000 times per second, for up to 24 h through the rings. –Protons of one beam collide with protons of the other beam at 4 collision points in the rings: collision products are measured by particle physics experiments. Key technical accelerator systems (not complete): –Powerful super-conducting magnets to bend and focus beams. Very sensitive to heat load. –Radio-frequency systems for beam acceleration. –Collimators to handle unavoidable power losses. A 1% system (1% of length, 1% of overall cost) which can drive overall performance. R. Assmann, June 2009

3. The LHC Goals: 7 TeV and 360 MJ The 360 MJ is a linear function of number of protons per beam 80 kg TNT factor ~200 above world record in sc storage rings factor ~7 above world record

4. Performance for Particle Physics Beam momentum or energy: Center-of-mass energy in collision is twice the particle energy, namely 14 TeV. –Determines discovery reach for particle physics. –Limited by maximum field in sc bending magnets. Event rate (luminosity): Number of useful events per time determines the time required to make a discovery. –Is optimized by “squeezing” protons into small cross-sections at interaction points (limited by field strength of sc quadrupoles). –Is optimized by storing ever higher number of protons per beam, gaining with the square or linearly with number of protons. Practical limit for number of protons that can be stored: –Unavoidable losses from stored beam, e.g. a dust particle falling through the beam, accelerator shaking with distant earth quakes, beam resonances, … –Efficiency in intercepting (cleaning) these losses  collimation R. Assmann, June 2009

5. Collimators: Preventing Quenches Shock beam impact: 2 MJ/mm 2 in 200 ns (0.5 kg TNT) Maximum beam loss at 7 TeV: 0.1% of beam (360 MJ) per second (assumed better than achieved in Tevatron/HERA) 360 kW 360 kW Quench limit of SC LHC magnet: 5 mW/cm 3 ~ 5 mW/cm 3  proportional to stored energy

6. R. Assmann, June 2009 LHC Collimators: Dilute and Stop Jaw 2 Jaw 1 Incoming: up to ~ 50 MJ/mm 2 (primary collimator) Quench limit: ~ 5 mJ/mm 2 (any SC magnet) Required “filter” factor: 1 × 10 -10 = Leakage / Dilution Leakage factor (inefficiency): 10 -4 Dilution factor: 10 6 Cannot be achieved with single collimator  therefore multi-stage collimation for betatron cleaning (x, y, skew) and momentum cleaning.

7. Multi-Stage Cleaning & Protection 3-4 Stages 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 High Z coll CFC W/Cu High Z coll Super- conducting magnets SC magnets and particle physics exp. CFC collimator R. Assmann, June 2009

8. System Design Momentum Cleaning Betatron Cleaning “Phase I” 108 collimators and absorbers in phase I (only movable shown in sketch)

9. The LHC Collimation System The by far largest and most precise system of its kind that has been built to this date: –130 phase I collimators and absorbers produced with specifications and control at 10  m level (including spares). –Phase I: In total 108 devices installed (~210 m length occupied). 97 movable collimators with a total of 194 jaws and > 450 degrees of freedom for positioning. Performance only OK for first years. All ready now. –Phase II: In total 158 devices installed (~ 310 m length occupied). 147 movable collimators. Planned up to 2014  R&D topic. –Maximum possible: In total 168 devices installed (~ 330 m length occupied). Only space reservations at this time. Investment (cost & manpower) comparable to a small accelerator. Design, R&D, prototyping, series production, installation and commissioning has been managed since late 2002 through the CERN LHC collimation project. Strong German part. R. Assmann, June 2009

10. Tunnel: Side View Phase I Collimator R. Assmann, June 2009

11. Tunnel: Cleaning Insertion IR7 R. Assmann, June 2009 BEAM PIPES COLLIMATOR TRANSPORT ZONE COLLIMATOR CABLE TRAYS RADIATION-HARD CABLE PATH WATER FEEDS PHASE I/II WATER DISTRIBUTION PHASE I/II WATER DISTRIBUTION

12. Tunnel: 3 Primary Collimators in IR7 R. Assmann, June 2009

13. 168 position sensors on 28 collimators: Repeating the same settings for 10 days, without feedback from position sensors! Example of Phase I Performance

14. Collimation-Related R&D Issues Advanced materials under extreme conditions: –New, robust materials that can survive the LHC beam while having excellent absorption and good electrical properties (composites, e.g. copper-diamond). –Efficient thermal conductivity in sandwich structures with powerful cooling. –Measurement and modeling of intense thermo-mechanical shock waves  CERN is putting up unique beam test facility. –Measurement and modeling of radiation damage. Massively parallel simulation of complex halo and collimation (Grid): –Simulating up to 30 million protons over 5,400 km beam line (200 turns) with 10 cm resolution. –Modeling leakage and dilution at the 10 -10 level. –Innovative collimation solutions: e-beam lens, crystal, plasma, … Advanced controls: Remote precision control, remote handling. –Control and monitor collimators over 27 km with precision of 10  m. –Automatic, precise and safe setup routines for ~500 degree of freedoms. R. Assmann, June 2009

15. The Phase II of LHC Collimation R. Assmann, June 2009 EMPTY PHASE II SLOT (38 IN TOTAL) OCCUPIED PHASE I SLOT Challenge: What kind of collimators do we best put into the prepared phase II positions up to 2014? Conditions in the LHC will be extreme and unique: new territory for accelerator science and technology! Innovation and new technology required and possible! Universities push the frontier in many aspects: Is there helpful expertise at TUM? Collaborating with 11 universities and institutes through FP7. 7 PhD studies. Some PhD opportunities for TUM? Good ideas can directly advance the LHC performance reach and help to make new fundamental discoveries! Challenge: What kind of collimators do we best put into the prepared phase II positions up to 2014? Conditions in the LHC will be extreme and unique: new territory for accelerator science and technology! Innovation and new technology required and possible! Universities push the frontier in many aspects: Is there helpful expertise at TUM? Collaborating with 11 universities and institutes through FP7. 7 PhD studies. Some PhD opportunities for TUM? Good ideas can directly advance the LHC performance reach and help to make new fundamental discoveries!