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

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. What is RC (rotating collimator)? HiRadMat Scientific Board Meeting - 14 March 2014

Jaw Design HiRadMat Scientific Board Meeting - 14 March 2014

RC Prototype with Apertures Designed for Testing in SPS beam HiRadMat Scientific Board Meeting - 14 March 2014

SLAC design details Ratchet Gear Drive RC-0 Jaw (copper) RC-1 Jaw (Glidcop) LHC IR7 Style BPM Buttons 4 per end LHC IR7 Style BPM Buttons 4 per end Flex Support Tank geometry allows a 60mm facet-to-facet gap in fully retracted Jaw position Tank geometry allows a 60mm facet-to-facet gap in fully retracted Jaw position Ferrite could mount to Base Plate facing Jaw facet Ferrite could mount to Base Plate facing Jaw facet BPM assemblies at each end are fiducialized to Collimator Base Plate Drive Mechanism RF foils carry image current and shields Rot. Mech. HiRadMat Scientific Board Meeting - 14 March 2014

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) HiRadMat Test Goals HiRadMat Scientific Board Meeting - 14 March 2014

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. Diagnostics HiRadMat Scientific Board Meeting - 14 March 2014

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 “machine readiness” for other beam tests. Short Status of RC collimator prototype HiRadMat Scientific Board Meeting - 14 March 2014

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! HiRadMat Scientific Board Meeting - 14 March 2014

Conclusions HiRadMat Scientific Board Meeting - 14 March 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 Will propose to postpone this experiment by 1 (or 2) year if we conclude that other beam tests will be needed before.

Other upcoming collimation experiments at HRM 1.RC SLAC tests 2.Individual collimator jaws with advanced design/materials 3.Collimator jaw with embedded wire for long-range beam- beam compensation schemes. 4.Material sample characterization against shock impacts 5.Present CFC collimator robustness with HL-LHC injected beams (done in the past at TT40, with nominal LHC case) HiRadMat Scientific Board Meeting - 14 March 2014