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Present Approach and Status

Present Approach and Status. R. Assmann for the LHC Collimation Team. Problem: Al/Cu system would not resist irregular dumps (pre-trigger or asynchronous) and low beam lifetimes, even during early physics. Solution: Low Z material: More robust but longer.

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Present Approach and Status

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  1. Present Approach and Status R. Assmann for the LHC Collimation Team Problem: Al/Cu system would not resist irregular dumps (pre-trigger or asynchronous) and low beam lifetimes, even during early physics. Solution: Low Z material: More robust but longer. Progress: Sep 2001 LHC Beam Cleaning Study Group Jan 2002 Consensus to consider low Z material (impedance presented as non-critical) Jun 2002 Consensus on detailed requirements First tolerances Oct 2002 Project LHC Collimation, AB/ATB Jan 2003 Full simulation chain: Beam – FLUKA – ANSYS Cleaning efficiency and optics with low Z Review of impedance, other constraints

  2. Our strategy: Find the simplest solution that is compatible with the requirements of the nominal LHC. (Carbon?!) Concentrate most effort into advancing these simple solutions. Keep more complicated/less convenient concepts in mind as backup solutions. (Beryllium, Diamond, multi-layer structures, crystal collimation, renewable high-Z collimators, repairable high-Z collimators, tertiary collimators at the triplets, primary collimators covering the phase space, anti-kicker at dump …) Some “backup solutions” might help to relax operational tolerances or help for machine protection.

  3. Feb 2003: Signs of convergence? (worst case shock beam impact) FLUKA: C seems best choice, better than Be higher Z is out of question 100 mm higher-Z coating seems unfeasible Copper structure after 1 cm C seems OK ANSYS: Simple C a factor 2-3 too low in robustness (OK for first years of LHC, 1 bunch out of 3) Other forms (carbon-carbon) under study (better?). Lengths: 0.2 m and 1.0 m long C jaws OK for efficiency first preliminary optics re-match looks good Radiation: Peak activation lower (avoid remote handling) First detailed results for BLM response All based on our consensus on low Z.

  4. AP worries for fundamental system design: Impedance: Reviewed in Jan 03. More details today… E-cloud: First discussion Jan 03. No estimate yet. SNS: TiN coating on all collimators Special solenoids in collimator locations Additional worries on operational, technical, engineering issues (not for now). Goal: Decide jaw design and material(s) in April 03. Fix fundamental constraints from impedance, local e-cloud as soon as possible! There are alternatives to low Z, but fundamental concept is changed.

  5. Collimators & absorbers at 7 TeV: • Numbers are for Al, Cu system. Length is given per collimator • All collimators two-sided except noted. • Number is per beam. • TCL (D2) is an upgrade for LHC ultimate performance. • Table is for 7 TeV. • Settings are for nominal luminosity and nominal b* (n1 = 7 in the triplet). • For injection add TDI, TCL (inj), and TCDS. All around 10 s. IR1 and IR5 settings could be open for injection, others remain at similar settings.

  6. Collimators & absorbers at 7 TeV (C-based system):

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