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Intensity Limits and Beam Performances in the H igh- E nergy S torage R ing

Intensity Limits and Beam Performances in the H igh- E nergy S torage R ing. HESR-Consortium: FZJ, GSI, TSL, and Univ. of Bonn and Dortmund. HESR Layout Beam Equilibrium Beam Losses and Luminosity Other Intensity Limiting Effects Summary & Outlook.

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Intensity Limits and Beam Performances in the H igh- E nergy S torage R ing

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  1. Intensity Limits and Beam Performances in the High-Energy Storage Ring HESR-Consortium: FZJ, GSI, TSL, and Univ. of Bonn and Dortmund • HESR Layout • Beam Equilibrium • Beam Losses and Luminosity • Other Intensity Limiting Effects • Summary & Outlook A. Lehrach, HESR, Coulomb ’05

  2. Accumulation and Accelerationof Antiprotons at FAIR • Antiproton production • Linac:50 MeV H- • SIS18:5·1012 protons / cycle • SIS100:2-2.5·1013 protons / cycle • 26 GeV protons • bunch compressed to 50nsec • Production target: antiprotons • 3% momentum spread • CR:bunch rotation and stochasticcooling at 3.8 GeV/c • RESR:accumulation at 3.8 GeV/c • Production rate 2·107/s (7·1010/h) antiprotons A. Lehrach, HESR, Coulomb ’05

  3. HESR Layout • One half of the arc super-period • Momentum range 1.5 – 15 GeV/c • 6-fold symmetry arcs with a length of 155 m each. • Mirror symmetric FODO structure • designed as pseudo second order achromat with dispersion suppression. • Two straight sections of 132 m length each. Ring circumference 574 m. Qx = 12.16 Qy = 12.18 γtr = 6.5i A. Lehrach, HESR, Coulomb ’05

  4. Experimental Requirements PANDA (Strong Interaction Studies with Antiprotons): Momentum range: 1.5 to 15 GeV/c A. Lehrach, HESR, Coulomb ’05

  5. Electron Cooler Feasibility study of magnetized electron cooling for the HESR 9/2003 (Budker Institute, Novosibirsk, RUS) • HV section electrostatic accelerator 0.45 - 8 MV, up to 2 A charged by H- beam • Cooling section sc solenoid • length 30 m • magnetic field 0.2 - 0.5 T • straightness 10-5 • beam diameter 6 - 10 mm • Bending section electrostatic up to 21 KV/cm bending radius 4 m HESR Electron Cooler High voltage (8 MV) tank 12 m Acceleration column Charger: H- Cyclotron HESR beam Cooling section Solenoid 8 m 30 m A. Lehrach, HESR, Coulomb ’05

  6. Fit to Parkhomchuk formula CELSIUS measurement Dec. 2004 Measurements at CELSIUS seem to predict an accuracy of the longitudinal Parkhomchuk force within a factor of 2 Electron Cooling Force Parkhomchuk model (*particle frame): Effective Coulomb log: Coolig rate: Longitudinal force (momentum spread ): A. Lehrach, HESR, Coulomb ’05

  7. Pellet target (WASA@CELSIUS) Formation of frozen hydrogen pellets H2 (=0.08 g/cm3) 60000 pellets/s  Beam spot d=30 m <n> = 5x1015 cm-2 1 mm • HESR: Target will be switched on after injection and cooling/IBS equilibrium • Transverse heating is required to ensure 1 mm spot size on the target A. Lehrach, HESR, Coulomb ’05

  8. Beam Heating • Transverse emittance growth in the target: • βx,y small, D=D‘=0, θrms: Mean Coulomb scattering angle • Longitudinal emittance growth in the target: • βs=h|η|/Qs (bunched beams), δrms: Mean relative momentum deviation • Multiple IBS: • (Soerensen or ‘plasma’ model) Diffusion constant: A. Lehrach, HESR, Coulomb ’05

  9. Equilibrium for Core Particles(rms analytic model) Results compare very well with BetaCool simulations With fixed emittance With equilibrium emittance 1011 particles 1011 particles 1010 particles 1010 particles Electron Cooler: L = 30 m Ie = 0.2 A veff = 2·104 m/s c = 100 m Target: Pellet Stream dt = 4·1015 cm-2 t = 1 m O. Boine-Frankenheim et al. A. Lehrach, HESR, Coulomb ’05

  10. INTAS Project“Advanced Beam Dynamics for Storage Rings” FZ Jülich,GSI Darmstadt, JINR Dubna, Univ. Kiev, ITEP Moscow, TSL Uppsala • Kinetic simulation of cooling dynamics • Benchmarking of different models for IBS, cooling forces and beam-target interaction • Analytical and numerical studies of instability thresholds in the presence of cooling and space charge • Impedance library • Kinetic simulation studies of accumulation schemes A. Lehrach, HESR, Coulomb ’05

  11. Beam Loss Mechanisms • Hadronic Interaction • Single Target Scattering out of the acceptance • Energy straggling out of the acceptance • Single IBS Scattering (Touschek loss rate) A. Lehrach, HESR, Coulomb ’05

  12. Hadronic Interaction Loss rate: PDG nt = 4·1015 cm-2 frev = 443, 519, 521 kHz σppbar = 100, 57, 51 mbarn A. Lehrach, HESR, Coulomb ’05

  13. Single Coulomb Scattering Loss rate: εt = 1 mm mrad nt = 4·1015 cm-2, Hydrogen frev = 443, 519, 521 kHz Rutherford Cross Section A. Lehrach, HESR, Coulomb ’05

  14. Energy Loss Straggling Single collision energy loss probability ( energy loss): Maximum energy transfer: Scaling quantity (~ mean energy loss): A. Lehrach, HESR, Coulomb ’05

  15. Energy Loss Straggling Lossprobability per turn Loss rate: δeff= -εeff/(β20E0)=10-3 frev = 443, 519, 521 kHz A. Lehrach, HESR, Coulomb ’05

  16. Single IBS: Touschek Loss Rate Single IBS changes the scattered particle momentum sufficiently that it excides the momentum acceptance of the accelerator Loss rate: δeff=10-3 1/T0 = frev = 443, 519, 521 kHz Touschek (IBS) lifetime increases with larger emittance A. Lehrach, HESR, Coulomb ’05

  17. Beam Life Time L0: initial luminosity τ: beam lifetime texp: experimental time tprep: beam preparation time np: number of particle nt: target desnity frev revolution frequency A. Lehrach, HESR, Coulomb ’05

  18. HESR Nominal Cycle A. Lehrach, HESR, Coulomb ’05

  19. Average Luminosity for HL for different pbar production rates! A. Lehrach, HESR, Coulomb ’05

  20. Effects on the Beam • Injection: Losses due to injection oscillation and RF capture • Pre-Cooling: Cooled and hot beams merge • Ramp: Snapback • Non-linear part of the ramp • Tune and Chromaticity control • Beam preparation: Squeeze • Orbit Control for beam-target overlap • Physics: Beam-Target Interaction, IBS, beam losses A. Lehrach, HESR, Coulomb ’05

  21. Effect of Electron Beam • Tune shift: • Coherent Dipole Instabilities: In the presence of the electron beam in the cooling section, both longitudinal and transverse instability could take place for the circulating beam due to ion clouds at lowest momentum ξ: neutralization factor • Electron heating . Theoretical “forecast”: N.S.Dikansky, V.V.Parkhomchuk, D.V.Pestrikov, Instability of Bunched Proton Beam interacting with ion “footprint”, Rus. Journ. Of Tech. Physics, v.46 (1976) 2551. P. Zenkevich, A. Dolinskii and I. Hofmann, Dipole instability of a circulating beam due to the ion cloud in an electron cooling system,NIM A 532(October 2004). A. Lehrach, HESR, Coulomb ’05

  22. Summary & Outlook • Beam equilibrium is dominated by IBS  heat the beam transversely • Major beam losses are induces by beam-target interaction  sufficient pbar production rate needed at low momenta • Beam effects and losses during cycle • Effect of the electron beam on the circulating beam A. Lehrach, HESR, Coulomb ’05

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