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

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Presentation on theme: "I. Ben-Zvi, 2 nd EIC Workshop, March 15-17, 2004 Electron Cooling of the Relativistic Heavy Ion Collider: Overview Ilan Ben-Zvi Collider-Accelerator Department."— Presentation transcript:

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

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

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

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

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

6 I. Ben-Zvi, 2 nd EIC Workshop, March 15-17, 2004 Structure of the RHIC Electron Cooling R&D Electron cooling R&D Experimental R&D ERLLinac cavity Guns Laser, photocathodes Benchmarking experiments Theory / simulations Beam dynamics Electron cooling Friction, IBS Dynamics Also: Cost and schedule. Work in progress.

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

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

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

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

11 I. Ben-Zvi, 2 nd EIC Workshop, March 15-17, 2004 Two-stage cooling Pre-cooling protons at 27 GeV, N p =1x10 11, Betacool with Derbenev-Skrinsky formula. N e =5x10 10 and 1x10 11 N e =1x10 11 Subsequent emittance growth at 250 GeV of initially pre-cooled protons

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

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

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

15 I. Ben-Zvi, 2 nd EIC Workshop, March 15-17, 2004 Parameters Cooling Section: Energy: 55 Mev Energy spread: 1 · 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 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

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

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

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

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

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

21 Goals for ERLs e-cooler prototype Generate and accelerate bright (  n < 50  mrad) intense (i.e mA) magnetized (i.e. with angular momentum) electron beam to the energy of 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 mA) electron beam with energy ~ 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

22 I. Ben-Zvi, 2 nd EIC Workshop, March 15-17, 2004 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, CsK 2 Sb cathode depositions started. Cathode will be provided for photoinjector in FY05.

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

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

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

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

27 I. Ben-Zvi, 2 nd EIC Workshop, March 15-17, 2004 High current ERL SRF cavity See 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.

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

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

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

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

32 I. Ben-Zvi, 2 nd EIC Workshop, March 15-17, 2004 Conceptual Design of Solenoid Copper Solenoid 20 mT; 1.83 m long Dipole Corrector

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

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


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