BeamBeam and Electron Lens Work Alexander Valishev US
Beam-Beam and Electron Lens Work Alexander Valishev US LARP DOE Review June 1 -2, 2011
Outline Historical view of beam-beam and e-lens tasks • Beam-beam simulations • § § § • Hollow electron beam collimator § § • 2 Code development Tune and offset scans Beam-beam at HE-LHC Concept Recent experimental results Plans US LARP Do. E Review, June 1 -2, 2011
Beam-Beam Task • Goals § § § • Contributors § • BNL, LBNL, FNAL, (SLAC) Past work highlights § § § 3 Develop and maintain simulation tools Support beam-beam related experiments at existing machines Support development of means of beam-beam effect mitigation Beam-beam effects at Tevatron Long-range compensation with wires Head-on compensation with electron lens US LARP Do. E Review, June 1 -2, 2011
Simulations for Wire Beam-Beam Compensation Experiment at RHIC The concept of long-range beam-beam compensation with wires was adopted by LHC BBSIM Simulations (T. Sen, H. J. Kim) 4 US LARP Do. E Review, June 1 -2, 2011
Electron Lens for Head-on Beam-Beam Compensation • • 5 Electron lens is a low energy electron beam (5 -10 k. V) that interacts with circulating hadron beam e- beam with proper shape of transverse charge density distribution can be used to compensate head-on beam-beam effect 2 electron lenses are installed at the Tevatron (TEL). Used for correction of bunch-by-bunch long-range beam tune shift and for abort gap cleaning 2 electron lenses are under construction at RHIC, funded by ARRA US LARP Do. E Review, June 1 -2, 2011
Head-on Beam-Beam Compensation Results in FY 10 Experiments at Tevatron • Demonstrated tune shift, tune spread • Stable operation during HEP • Could not demonstrate compensation because of Tevatron beam conditions (unequal emittances) • Experiments finished in 2010 Simulations for LHC • Predict benefit at intensities above 3 x 1011 protons per bunch • Head-on beam-beam not an issue at nominal parameters • E-Lens not likely to be needed BBC=on BBC=off 6 US LARP Do. E Review, June 1 -2, 2011
Beam-Beam Simulations in FY 11 Effect of E-Lens Misalignment Simulation reproduces Tevatron experiment 7 US LARP Do. E Review, June 1 -2, 2011
Beam-Beam Simulations in FY 11 Code Development • • 8 Single-particle tracking results were compared for two codes Sixtrack (CERN ) and Lifetrac (FNAL ) for full LHC model. Good agreement in a wide range of conditions US LARP Do. E Review, June 1 -2, 2011
Beam-Beam Simulations in FY 11 Support of Tevatron Experiments • • • 9 FNAL, CERN, BNL expressed interest in conducting beam studies at the end of Run II. Accelerator physics study period was originally planned at the end of run. Now decided to plan 2 -week periods with study periods interleaved with luminosity operation. Beam-beam period planned at the end of August • Diffusion Due to Beam-Beam S. White, BNL Resonances • Phase Averaging • Coherent Beam-Beam Modes • Beam-Beam vs Transverse Separation • AC Dipole with colliding beams 4 -5 study periods, each with 2 special 3 x 3 colliding stores. CERN, BNL participation expected US LARP Do. E Review, June 1 -2, 2011
Beam-Beam Simulations in FY 11 Parameter Scans for LHC Vertical emittance growth vs. tune Emittance growth vs. beam separation J. Qiang, S. Paret, LBNL 10 US LARP Do. E Review, June 1 -2, 2011
Beam-Beam Simulations in FY 11 HE-LHC Beam energy 16. 5 Te. V Number of IPs 2 Bunch population 1. 3× 1011 Initial normalized transverse emittance 3. 75, 1. 84 (x, y) mm Energy loss per turn U 0=206. 3 ke. V SR power P=67 k. W Emittance damping time tx, ty=1. 93 h t. E=0. 96 h Normalized SR equilibrium emitance ex 0=0. 01 mm Equilibrium momentum spread d 0=3. 4× 10 -6 Horizontal IBS emittance growth time 82 h Longitudinal IBS emittance growth time 72 h 11 US LARP Do. E Review, June 1 -2, 2011
Collimation with Hollow Electron Beam The Concept • • In LHC at full intensity primary collimators cannot be placed close to beam Enhance diffusion with hollow e- beam V. Shiltsev et al EPAC 08 12 US LARP Do. E Review, June 1 -2, 2011
Collimation with Hollow Electron Beam Modification of Tevatron Electron Lens Are bends essential? Tungsten dispenser cathode with convex surface. Diameter 15 mm, hole 9 mm Gun installed in TEL-2 in Aug. 2010 First experiments Oct. 2010 13 US LARP Do. E Review, June 1 -2, 2011
Collimation with Hollow Electron Beam Halo Particle Removal • • Successfully demonstrated slow halo particle removal ! No effect on luminosiity ! G. Stancari, et al FNAL 14 US LARP Do. E Review, June 1 -2, 2011
Collimation with Hollow Electron Beam Method of Diffusion Measurement Mess and Seidel, NIM A 351, 279 (1994) 15 US LARP Do. E Review, June 1 -2, 2011
Collimation with Hollow Electron Beam Diffusion Measurement at Tevatron • • First diffusion measurement at Tevatron Hollow beam clearly enhances diffusion and suppresses loss spikes • Control train • Affected train G. Stancari, et al FNAL 16 US LARP Do. E Review, June 1 -2, 2011
Collimation with Hollow Electron Beam 1 -inch Gun Design • • • 17 Test of technical feasibility • 25 mm diameter, 13. 5 mm hole • Up to 3 A at 5 k. V All parts ordered, delivery in June Assembly in July US LARP Do. E Review, June 1 -2, 2011
Conclusions and Outlook • Simulation codes produce results in good agreement with observations § Benchmarking required for complex 6 -D dynamics and coherent beam-beam effects • § • Need to implement elements of collimation systems Significant progress in development of the Hollow Electron Beam Collimator concept § § Successful proof-of-principle demonstration at Tevatron Strong support from CERN, work towards installation in LHC in 2016 • 18 Tevatron experiments will provide data Develop detailed concept for LHC US LARP Do. E Review, June 1 -2, 2011
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