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Electron Cooling of the Relativistic Heavy Ion Collider: Overview

Electron Cooling of the Relativistic Heavy Ion Collider: Overview. Ilan Ben-Zvi Collider-Accelerator Department Brookhaven National Laboratory. Motivation. The motivation for electron cooling of RHIC is to increase luminosity by reducing emittance and overcoming IBS.

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Electron Cooling of the Relativistic Heavy Ion Collider: Overview

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  1. Electron Cooling of the Relativistic Heavy Ion Collider:Overview Ilan Ben-Zvi Collider-Accelerator Department Brookhaven National Laboratory I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  2. Motivation • The motivation for electron cooling of RHIC is to increase luminosity by reducing emittance and overcoming IBS. • Increase the integrated luminosity for gold on gold collisions by an order of magnitude, also higher P-P luminosity (RHIC II). • Increase the luminosity of protons and ions on electrons and shorten ion bunches (eRHIC) • Both RHIC II and eRHIC are on the DOE’s 20 years facilities plan. RHIC luminosity decay (3.5 hours) I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  3. IP#12 - main Linac-ring eRHIC: Main-stream - 5-10 GeV e- Up-gradable to 20+ GeV e- IP#10 - optional IP#2 - optional Luminosity up to 1 x 1034 cm-2 sec-1 per nucleon Place for doubling energy linac IP#4- optional Electron cooling RHIC EBIS Booster Linac AGS I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  4. What is special about cooling RHIC The cooling takes place in the co-moving frame, where the ions and electrons experience only their relative motion. RHIC ion are ~100 times more energetic than a typical cooler ring. Relativistic factors slow the cooling by at least factor of 2. So, first and foremost, we must provide a factor of 2 more cooling power than typical. Other points: Cooling of a bunched beam, cooling of a collider, recombination and disintegration, use of a high-temperature electron beam. Transport of a magnetized (angular momentum dominated) beam without a continuous solenoid. We cannot use conventional accelerator techniques. We require a high-energy (54 MeV), high-current (0.1 to 0.3 A) electron beam for the cooler, based on an Energy Recovery Linac. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  5. R&D issues • High current, energetic, magnetized, cold electron beam. Not done before • Photoinjector (inc. photocathode, laser, etc.) • ERL, at x100 the current of current JLAB ERL • Beam dynamics study (magnetized beam AND space-charge AND discontinuous solenoid) • Understanding the cooling physics in a new regime, must reduce uncertainty • bunched beam, recombination, IBS, disintegration • electron cooling simulations with some precision • A very long, super-precise solenoid (30 m long, 1-2 Tesla, 8x10-6 error) I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  6. Structure of theRHIC Electron Cooling R&D Also: Cost and schedule. Work in progress. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  7. Electron cooling group (Reporting to Thomas Roser) and collaborators. Ilan Ben-Zvi, Vladimir Litvinenko, Andrew Burrill, Rama Calaga, Xiangyun Chang, Alexei Fedotov, Dmitry Kairan, Joerg Kewisch, David Pate, Mike Blaskiewicz, Yuri Eidelman, Harald Hahn, Ady Hershcovitch, Gary McIntyre, Christoph Montag, Anthony Nicoletti, George Parzen, James Rank, Joseph Scaduto, Alex Zaltsman, Animesh Jain, Triveni Rao, Kuo-Chen Wu, Vitaly Yakimenko, Yongxiang Zhao. GSI/INTAS collaboration: O. Boine-Frankenheim, others. JLAB: J. Delayen, Ya. Derbenev, P. Kneisel, L. Merminga. JINR (Dubna), Russia: I. Meshkov, A. Sidorin, A. Smirnov, G. Trubnikov BINP, Russia: V. Parkhomchuk, A. Skrinsky, many others. FNAL: A. Burov, S. Nagaitsev. SLAC: D. Dowell. Advanced Energy Systems: M. Cole, A. Burger, A. Favale, D. Holmes, A. Todd, J. Rathke, T. Schultheiss. Tech-X, Colorado: D. Abell, D. Bruhwiler, R. Busby, J. Cary. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  8. Electron cooling theory, simulations and benchmarking experiments • Lead – Alexei Fedotov Objective: Reduce the extremely large uncertainty in calculating cooling rates, develop new software tools and benchmark them. Status: Three software tools in various stages of development. Expect solid results in FY05. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  9. Outstanding issues 1. Complete development of code and benchmarking, obtain accurate estimates for cooling times. 2. Cooling with bunched electron beam. 3. Cooling with “hot” electrons: RHIC Typical coolers transverse : 1000 eV 0.1-1 eV longitudinal : 50 meV 0.1 meV 4. Do we have sufficient magnetized cooling? 5. What are the optimum parameters for electron beam? 6. Detailed IBS. 7. Dynamics of the cooled ion beam, such as the impact on threshold of collective instabilities. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  10. Cooling gold at 100 GeV/A Transverse profile Luminosity increase Longitudinal profile I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  11. Two-stage cooling Pre-cooling protons at 27 GeV, Np=1x1011, Betacool with Derbenev-Skrinsky formula. Ne=1x1011 Ne=5x1010 and 1x1011 Subsequent emittance growth at 250 GeV of initially pre-cooled protons I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  12. Electron dynamics R&D • Lead - Joerg Kewisch The objective is a complete design of the electron accelerator, including start-to-end simulation. Understanding emittance growth under high space-charge forces is important as well transport and matching of magnetized electrons. Status: Basic simulation tools at hand, initial start-to-end simulation done, new understanding of physics gained. To be completed in FY2006 with a test. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  13. Layout of RHIC electron cooler Gun ERL cavities Beam dump Solenoid Stretcher Each electron bunch is used just once. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  14. Layout I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  15. Parameters • Arcs: • Max.Dispersion: 6 m • Max. Beam Size (rms): 5 cm • Stretch factor: 33 m • Gun: • Normal Conducting • 700 MHz 2½ Cell • Bunch charge: 10 nC • Bunch frequency: 9.8 MHz • Beam Energy: 2.5 MeV • Power: 1MW Cooling Section: Energy: 55 Mev Energy spread: 1· 10-4 Bunch length: 15 cm Bunch radius: 1mm Emittance: 50 mm mrad Solenoid: 1 Tesla Linac: 700 MHz Cavities: 4 Gradient: 15 MV/m 2100 MHz Cavities: 3 Gradient: 7.5 MV/m Power amplifiers: 50 kW I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  16. Front to End Simulation: Beam Size I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  17. Front to End Simulation: Emittance • Method: • Track electrons using PARMELA including space charge • Apply linear transformation to make transport axial symmetric, remove dispersion • Apply solenoid fringe field matrix • Measure emittance I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  18. Development of complete ERL • Lead - Vladimir Litvinenko The objective is to build an ERL comprising a CW photoinjector, superconducting cavity and beam transport and test it for the RHIC/eRHIC current limits. Status: Basic beam optics design done for up to 0.5 amperes. Testing system in 2006. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  19. ERL - Bldg. 912 e- 30-40 MeV e- 15-20 MeV Controls & Diagnostics Magnets, vacuum Cryo-module Vacuum system Laser e- 2.5MeV Beam dump e- 2.5MeV Gun SRF cavity 1 MW 700 MHz Klystron 50 kW 700 MHz Klystron PS I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  20. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  21. Generate and accelerate bright (n < 50 mrad) intense (i.e. 150+ mA)magnetized (i.e. with angular momentum) electron beam to the energy of 54.677 MeV Cool the ion beam(s) Decelerated the electron beam to few MeV and to recover its energy back into the RF field Generate and accelerate bright (n < 50 mrad) intense (i.e. 150+ mA) electron beam with energy ~ 20-40 MeV Decelerated the electron beam to few MeV and to recover its energy back into the RF field Test the concepts and stability criteria for very high current ERLs Goals for ERLse-coolerprototype I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  22. Photocathode and laser • Lead – Triveni Rao The objective: Develop a photocathode material that has a high quantum efficiency in the green and long life. Develop suitable laser technology. Status: UHV deposition chamber operational, CsK2Sb cathode depositions started. Cathode will be provided for photoinjector in FY05. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  23. CW - Photoinjector -Glidcop, 703.75 MHz Solenoid RF input coupler New 703 MHz CW Photoinjector Under construction LANL and Advanced Energy Systems I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  24. Superconducting gun AES – BNL – JLAB gun Possible direction? Rossendorf like gun with CsK2Sb or similar cathode I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  25. CsK2Sb Photocathode UHV photocathode preparation system I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  26. Q.E. as a function of Cs deposition I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  27. High current ERL SRF cavitySee presentation by Ram Calaga in WG • Lead – Ilan Ben-Zvi Objective: Develop a cavity for high average current (about 100 times the JLAB ERL), with large-charge bunches (difficult HOM power handling) Status: Design successfully finished, contract for manufacturing in place. Cold test June 2004, cavity delivered for tests in May 2005. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  28. HOM calculated By MAFIA. All HOMs are extremely well damped. Ferrite HOM damper Cryomodule Copper cavity parts I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  29. Low impedance: 6 times smaller than TESLA cavity I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  30. Cavity quality: • Ep / Ea ~2 • R/Q = 807  •  = 225  • Hp/Ea = 5.8 mT/MV/m Qualities important for ERL service: • Loss factor 1.2 V/pC (less HOM power) • BBU threshold about 1.5 to 2 amperes • Mechanically very stiff cavity, lowest mechanical resonance over 100 Hz I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  31. Superconducting solenoid • Lead –Animesh Jain Objective: Develop a prototype superconducting solenoid and its measurement system, demonstrate ability to deliver ultra-high precision in two 13 m long sections, 1 T superconducting solenoid. Status: Solenoid principles established, Prototype design under way. Correction system under tests. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  32. Copper Solenoid20 mT; 1.83 m long Dipole Corrector Conceptual Design of Solenoid I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  33. Simulated Correction Net Field after correction from 10-4 initial error I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

  34. Conclusions • High energy electron cooling looks feasible, but requires R&D. • An aggressive and comprehensive R&D program is in place. • We recognize the challenges, but we are confident that cooling RHIC will work well. • In about three years we expect to resolve all outstanding R&D issues. I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004

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