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SLAC rotating collimator for HiRadMat beam tests

US LHC Accelerator Research Program CERN – LHC Collimation Project. SLAC rotating collimator for HiRadMat beam tests. 14 March 2014 S. Redaelli, A. Bertarelli, CERN T. Markiewicz, SLAC. What is RC (rotating collimator)?.

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SLAC rotating collimator for HiRadMat beam tests

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  1. US LHC Accelerator Research Program CERN – LHC Collimation Project SLAC rotating collimator for HiRadMat beam tests 14 March 2014 S. Redaelli, A. Bertarelli, CERN T. Markiewicz, SLAC

  2. What is RC (rotating collimator)? • Two jaw collimator made of Glidcop; same dimensions as the standard LHC collimator; possibility to rotate the jaws if the surface is damaged by beam accidents. • Advantages: • Not exotic material • High Z for efficiency • Low resistance for impedance • Elemental for high radiation resistance • Disadvantages: • Glidcop WILL be damaged in asynchronous beam abort • Complex design – robustness against worst-case scenarios needs to be validated.

  3. Jaw Design

  4. RC Prototype with Apertures Designed for Testing in SPS beam

  5. SLAC design details RC-1 Jaw (Glidcop) RF foils carry image current and shields Rot. Mech. Tank geometry allows a 60mm facet-to-facet gap in fully retracted Jaw position BPM assemblies at each end are fiducialized to Collimator RC-0 Jaw (copper) Ratchet Gear Drive LHC IR7 Style BPM Buttons 4 per end Base Plate Flex Support Ferrite could mount to Base Plate facing Jaw facet Drive Mechanism

  6. HiRadMat Test Goals • Verify that the rotation mechanism will continue to operate after beam impact • Measure the full extent of the GlidCop collimator jaw that melts and vaporizes as a function of deposited energy • Determine the extent of the molten and vaporized spray released from the surface, how far it travels and how it congeals to the hit surfaces. Effect on other jaw? • Verify that the water cooling circuit survives a beam impact with no water to vacuum leak. • Determine if nearby facets will get deposited with molten material from a hit facet. • Measure permanent deformation (jaw bending?) from beam impact. • Note: this goals can be achieved without additional instrumentation (standard collimator alignments with pilot beam, existing BLMs)

  7. Diagnostics • On-line measurements: • - Standard positioning system (jaw monitoring) • - Usual beam orbit and BLMs • - Transient vacuum and temperature during impacts • Post mortem (main conclusions expected from this!) • - SPS RC Prototype has • 15 view ports: Visual or camera viewing Laser micrometers to measure deformation? • - Eventually open the vacuum tank for detailed inspection and metrology measurements on jaws.

  8. Short Status of RC collimator prototype • The SLAC collimator was delivered to CERN in Dec. 2013! • The delivered prototype looks very nice. “Pity” to do only HRM destruction tests. • Presently exploring its “machinereadiness” for other beam tests.

  9. Status and timeline of CERN tests • Our test program plans to address: - Vacuum aspects (so far, leak tests are ok) - Transverse positioning accuracy of jaws - Jaw rotation mechanism - Impedance of present tank design (trapped modes). • Timeline: expect main results by the end of April 2014(planning to report status at the US-LARP CM22 in BNL) • IF the RC SLAC prototype is compatible with SPS or LHC, we will consider testing it with circulating beams before carrying out the HRM destructive beam tests!

  10. Conclusions • - The HRM test with the SLAC RC collimator was presented.This is an advanced “consumable” collimator concept relying on rotatable jaws, providing in theory 20 catastrophic failures per jaw before being replaced. • - Before relying on such advanced concept, beam tests are deemed necessary to assess the rotation mechanism functionality after beam impacts. Tests at HRM are crucial to validate this design. • - The SLAC collimator is now at CERN and will be ready anytime to HRM • - This device was conceived and built by SLAC within a strong collaboration with USA: we are committed to get as much a possible out of this design. • - We are therefore exploring the possibility to test this device also with circulating beams before performing destructive tests at HRM! • - We will have the indications of the feasibility to install it in the SPS (or even LHC) in about 2 months. Decide then on the HRM plans for 2015.Will propose to postpone this experiment by 1 (or 2) year if we conclude that other beam tests will be needed before.

  11. Other upcoming collimation experiments at HRM • RC SLAC tests • Individual collimator jaws with advanced design/materials • Collimator jaw with embedded wire for long-range beam-beam compensation schemes. • Material sample characterization against shock impacts • Present CFC collimator robustness with HL-LHC injected beams (done in the past at TT40, with nominal LHC case)

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