Powering scheme for Hollow Electron Lens D. Mirarchi, S. Redaelli On behalf of the LHC Collimation team CWG #232, D. Mirarchi

Introduction Present collimation system designed to handle up to 360 MJ, HL-LHC design ~700 MJ How much of this energy is in the tails? Halo population probed by means of collimator scans BLM signal calibrated using BCT signal Scaling to HL-LHC parameters: ~33.6 MJ in the tails! ~5% of the beams in the tails (>3.5 s) while 0.22% if Gaussian G. Valentino Orbit jitter Crab cavity phase slip Fast failure scenarios: Magnet quench Permanent damage to TCPs Possible consequences: CWG #232, D. Mirarchi

Hollow e-lens assisted collimation Working principle: hollow electron beam surrounds the p beam as additional hierarchy layer Primary halo Secondary halo Tertiary halo + hadronic shower TCP TCSG TCLA Circulating beam Hollow e-lens Primary halo e- beam TCP Increased diffusion speed and depleted halo population em-field acting only on halo particles CWG #232, D. Mirarchi

Possible working mode continuous (DC) Stochastic: Stochastic-ONOFF: Stochastic-amplitude: Resonant: Resonant-turn: Resonant-tune: Stochastic-amplitude + Resonant-turn J. Wagner CWG #232, D. Mirarchi

HL-LHC filling pattern Baseline HL-LHC filling pattern: 72 bunches train 25 ns spacing Gap between injection into the SPS 200 ns Gap between injection into the LHC 800 ns Abort gap 3 ms 88.924 ms CWG #232, D. Mirarchi

HEL requirements At least one train of 72 bunches not affected by HEL due to machine protection reasons e-beam ON/OFF 3 times in one turn: 35 kHz repetition rate Modular selection from 1 train of 12-48 bunches to full beam (excluding abort gap) e-beam pulse length in the range from 1.2 ms to 86 ms Possibility to switch e-beam ON/OFF within LHC trains pulse rise-time (10%-90%) of 200 ns due to internal structure coming from SPS Ideally full range of current 0 – 5 A always available studies on-going to define margins Specs available at: new HL-LHC TDR being published (see next slide) CWG #232, D. Mirarchi

HEL specs CWG #232, D. Mirarchi