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Phase II Collimators at CERN: design status and proposals

This document provides an update on the design status of Phase II collimators at CERN and proposes new design features to improve cleaning efficiency, impedance, setup time, radiation hardness, and geometrical stability. Various design options and materials are discussed, and prototypes have been successfully tested. Lab tests will begin in April/May 2009, with beam tests in the SPS planned for the 2010 run.

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Phase II Collimators at CERN: design status and proposals

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  1. Phase II Collimators at CERN: design status and proposals EuCARD/ColMat kick-off meeting 17th June, 2009 Alessandro Bertarelli

  2. Who at CERN Mechanical Engineering: Alessandro Bertarelli, Alessandro Dallocchio, Ricardo de Morais Amaral Material Science: Gonzalo Arnau Izquierdo, Romain Blanchon, PhD student Mechanical Design: Roger Perret, Arnaud Bouzoud, Bruno Feral, Marc Timmins Manufacturing: G. Favre, L. Ferreira, A. Cherif Plus many more from EN, TE and BE departments

  3. Limits of Phase I Collimators • Resistive Impedance According to RF simulations, Phase I Collimator Impedance would limit LHC beam intensity to ~40% of its nominal value! • Cleaning efficiencyCleaning efficiency (i.e. ratio escaping protons / impacting protons) should be better than 99.998% to limit risks of quench in Super Conducting magnets. Simulations predict a beam intensity limited to ~40% of Inom for perfect collimators. • Radiation HardnessOngoing tests anticipate risks of degradation of Carbon/Carbon jaws (reduction of thermal and electrical conductivity, swelling, dust …) • Set-up and calibration timeStandard methods, based on measurement of beam loss generated by jaw adjustment, lengthy, requiring specific low intensity fills

  4. Phase II goals • Gain factor ≥10 in cleaning efficiency. • Gain factor ≥10 in impedance. • Gain factor ≥10 in set-up time (and accuracy?). • Radiation hardness and easy handling. • Improved geometrical stability (in operating conditions) 20 mm • Sufficient robustness (like Phase I?). • RWA May 2008

  5. Phase II Design Features • Jaw design • Modular design (a common baseline for the jaw assembly allows the use of alternative materials for the jaw). • Back-stiffener concept to allow maximum geometrical stability (improves collimator efficiency). • Adjustable system to allow jaw flatness control and compensate gravity sag (2 versions being studied … ) • Optimized internal cooling circuit to absorb higher heat-loads. • Integrated BPMs to minimize set-up time. • Jaw materials (goals) • Tailored electrical conductivity to improve RF stability. • High thermo-mechanical stability and robustness. • Higher density (high-Z) to improve collimation efficiency. • Strong resistance to particle radiation.

  6. Phase II Design options …depending on RF and cleaning efficiency specifications…

  7. Alternative Materials Metal jaw (high electrical conductivity) vs. Ceramic jaw (non-conductive) on metal conductive support...

  8. Phase II Design baseline (v1) Modular concept to fit in alternative jaw materials ... EQUIPPED JAW BRAZED COOLER FINE ADJUSTMENT SYSTEM BACK-STIFFENER

  9. Equipped Jaw (v1) 1st version of equipped jaw (1 adjustable support) … SiC absorber shown … Ceramic tiles SiC brazed on metal (conductive) support …Cu-CD is favorite candidate Machined cooling circuit with brazed cover. Fine adjustment system

  10. Design Baseline (v2) RF contacts ensure electrical conductivity between jaw pieces Alternative design of equipped jaw based on 2 intermediate adjustable supports … Fine adjustment system Mo Back - Stiffener Cut jaw: each piece is independently supported on the back stiffener. Enhanced geometrical stability

  11. Design Baseline (v2) 3-pieces jaw independently cooled by three separate brazed coolers Jaw Jaw - Stiffener Machine cooling circuit with brazed covers Back - Stiffener

  12. Cooler prototype Using high Z-material leads to higher energy deposition (up to a factor 5 increase w.r.t. Phase I). Higher cooling capacity is essential to ensure geometrical stability… Two prototypes including machined circuit, brazed cover and jaw mock-up have been produced and successfully tested…

  13. Cooler prototype The goal is to define a complete and standardized procedure according to UHV specs. in order to qualify the design. Jaw mock-up Test successfully performed: • He leak detection • Ultrasound cartography of the brazing surfaces • Pressure test (100 bar over 1h) • Final He leak detection. Machined circuit Brazed cover

  14. BPM functional prototype Graphite inserts BPM cables OFE-Cu jaw support OBJECTIVES: • Lab. tests to start April/ May 2009 • Beam tests in SPS during 2010 run (installation dates to be determined …) Mechanical design of simplified jaws featuring BPMs… BPMs BPM buttons Motivation: BPMs integration strongly influences the design of the whole system. A rapid testing in the SPS of the BPM embedded system is mandatory to validate the concept.

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