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Exploring Electron Cloud Phenomena in SPS: Experimental Studies and Future Plans

This document outlines various studies related to electron cloud effects in the Super Proton Synchrotron (SPS) at CERN. It discusses contributions to a proposal on electron cloud and presents findings from simulation studies and experimental activities, including beam quality studies and scrubbing procedures. Key outcomes such as signal monitoring from electron cloud monitors, the influence of a-C coating, and performance recovery strategies are highlighted. Future plans post-LS1 are also covered, emphasizing ongoing simulations and characterizations aimed at understanding and mitigating electron cloud challenges.

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Exploring Electron Cloud Phenomena in SPS: Experimental Studies and Future Plans

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  1. LIU-SPS e-cloudcontributionto TDR • First draft by end of February 2014. Between 5 to 10 max pages per chapter, refer to existing publications • Proposal concerning electron cloud • Simulation study of SPS chambers  ECLOUD12 paper summarizes the outcomes • Experimental activities at SPS • Beam quality studies, signal from e-cloud monitors, experiment with a-C coated pipe and solenoids at both ends to explain pressure rise  all described in the note published last year, CERN-ATS-Note-2013-019 MD needs to be compressed in few pages • Doublet beam tests (optimized scrubbing)  IPAC paper • Future plans (post-LS1, strategy coating vs. scrubbing)  Hannes’ paper from RLIUP Electron cloud meeting, 17/02/2014

  2. Future studies (SPS) • Simulations • Simulation of main quadrupoles QD and QF (SEY threshold) • E-cloud monitors (including the holes) • COLDEX – meeting with TE/VSC colleagues to define the needs • Instability thresholds with all chambers (MBB, MBA, QD, QF, SS1, SS2)? • Experimental activities at SPS (scrubbing run 2014 + MDs) • 25 ns beam(standard and BCMS) • Recover 2012 performance • Push performance to maximum intensity (possibly higher brightness thanks to the PSB-PS larger longitudinal emittance transfer), • Monitor scrubbing process based on e-cloud observables (liners, beam lifetime, emittances, tune shift along the train, chromaticity needed to stabilise). • Characterization of the a-C coated cell. In-situ SEY measurements device? • Doublet beam, full set up (need to set up slower acceleration cycle, Q20 and Q26) • High Bandwidth Feedback System tests on single bunches of a multi-bunch beam (using directly data with ECI, if possible) • Test 8b + 4e scheme (e-cloud efficient ?) • COLDEX measurements with cold a-C coating (probably in 2015?) Electron cloud meeting, 17/02/2014

  3. Injectorschedule 2014 Electron cloud meeting, 17/02/2014

  4. Future studies (LHC) • Simulations (no experiments in 2014) • Simulation of all SAMs and semi-SAMs (SEY threshold) • Comparison with heat load data to determine • Evolution of SEY • Present value of SEY • Heat load in dispersion suppressor to determine fractions of e-cloud in arc dipoles and quads • Comparison with stable phase shift measurements including alos the contribution from arc quads + SAMs + semi-SAMs • Extract all the heat load data from ITs (2011 – 2013) • Define a strategy to determine the scrubbing history with both 50 and 25 ns beams (simulations of some selected points) • Project for summer student submitted • Simulation of higher order magnets (sextupoles, octupoles) • Do we need to include also the drifts in all our comparisons with heat load data? (usually cryostats include long drift portions) • Holes in the beam screen: effect in dipoles ? • E-cloud in BSRT chamber? Can we change the magnetic field and measure heat load? • Stability for different octupole polarities (to explain hunchback instability) Electron cloud meeting, 17/02/2014

  5. Future studies (PS) • Simulations • Simulation of the new e-cloud monitors in SS98 (expected signal) • Instability simulations ?  self-consistent approach needed, maybe start with concatenating PyECLOUD and HEADTAIL (how easy through cobra-HEADTAIL?) • Experimental activities at PS • Measurements with the new monitors installed (25 and 50 ns, different bunch lengths over the last part of the cycle) • Cover higher intensities, up to LIU values, if achievable after LS1 with the new longitudinal feedback • More instability data? • New Technical student will start in March 2014  Annalisa Romano Electron cloud meeting, 17/02/2014

  6. Future studies (Miscellaneous) • More LHC and HL-LHC studies • BGV, MKI, TDI, BSRT … • HL-LHC  Triplets in IP2 and IP8, include D1 with new triplets in IP1 and IP5, SAMs from matching sections  April • CLIC damping rings • Check electron cloud in the electron ring for the rebaselining? (possible resonant values for which there could be electron accumulation even in electron ring) • Check for cyclotron resonances in wigglers? (scan in magnetic field between -2.5 and 2.5 T) • FCC • Define possible electron cloud issues in the FCC and injector chambers (defined by magnet and resistive wall constraints) • Scan over bunch intensities and spacings under consideration Electron cloud meeting, 17/02/2014

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