1. Testing Advanced Cooling Techniques 1 Vladimir N. Litvinenko for Coherent electron Cooling team Supported by BNL (LDRDs & PD), C-AD AR&DD, and NP DoE office Accelerator R&D grant C-AD, Brookhaven National Laboratory, Upton, NY, USA Stony Brook University, Stony Brook, NY, USA, AES, Medfrord, NY, USA SLAC, Palo Alto, USA, Niowave Inc., Lansing, MI, USA, Tech X, Boulder, CO, USA Budker Institute of Nuclear Physics, Novosibirsk, Russia STFC, Daresbury Lab, Daresbury, Warrington, Cheshire, UK

2. eRHIC: Highly advanced and energy electron-ion collider arXiv:1409.1633 eRHIC peak luminosity

3. eRHIC hadron beam is 1,000 x brighter than current RHIC beams Very strong cooling is required

4. Requirement vs. current cooling techniques IBS growth time for eRHIC beam is about 20 seconds (for 250 GeV protons) and have to be contra-acted by cooling RHIC’s stochastic cooling can cool 10 9 ions in 5 nsec bucket with cooling time ~ 1 hour. It is equivalent to cooling time for eRHIC 0.3 nsec bunches: – Heavy ions > 10 hours – Protons > 100 hours Our best design for electron cooling promised to cool ion beam at 100 GeV with cooling time of one hour. Extending this $150M facility to cool 250 GeV protons will provide cooling time of bout 30 hours. It would be better than stochastic cooling, but definitely insufficient for eRHIC We need a better cooling mechanism.

5. Coherent Electron Cooling Schemes Modulator Kicker Dispersion section ( for hadrons) Electrons Hadrons High gain FEL (for electrons) EhEh E < E h E > E h EhEh E < E h E > E h Classic – FEL amplifier (2006, PRL VL & YD) E < E h Blended – laser amplifier (2007, VL) Modulator Kicker Dispersion section ( for hadrons) Electrons Hadrons EhEh E > E h Radiator Energy modulator R 56 Laser Amplifier Modulator I Kicker Dispersion section ( for hadrons) Electrons Hadrons EhEh E > E h Micro-bunching Amplifier Enhanced bunching: single stage - VL, FEL 2007 Micro-bunching: MB Amplifier, Single & Multi-stage, D. Ratner, PRL, 2013 Modulator 2 -R 56 /4 R 56 -R 56 /4 Modulator 5 -R 56 /4 5

6. “Classical: Coherent electron Cooling scheme 6 Amplifier of the e-beam modulation in an FEL with gain G FEL ~10 2 vhvh 2 R D// λ FEL 2 R Dt λ FEL EzEz E0E0 E < E 0 E > E 0 Modulator Kicker Dispersion section ( for hadrons) Electrons Hadrons l2l2 l1l1 High gain FEL (for electrons) EhEh E < E h E > E h Dispersion At a half of plasma oscillation Debye radii Density

7. Coherent Electron Cooling Schemes Enhanced bunching: single stage - VL, FEL 2007 Micro-bunching: Multi-stage 2013, D. Ratner, Modulator I Kicker Dispersion section ( for hadrons) Electrons Hadrons l2l2 l1l1 EhEh E > E h Bunching R 56 Enhanced e-cooling © VL, Gang Wang, 2013

8. CeC limits 8 Each charged particle causes generation of an electric field wave-packet proportional to its charge and synchronized with its initial position in the bunch Evolution of the RMS value resembles stochastic cooling! Best cooling rate achievable is ~ 1/N eff, N eff is effective number of hadrons in coherent sample (Λ k = N c λ ) eRHIC @ 250 GeV -> FEL wavelength 0.5 um, Λ k ~ 20 um, N eff ~3x10 7 : it is critical to see if this can be achieved Λ k ~ 38 λ fel

9. Saturation 9

10. CeC Proof-of-Principle Experiment

11. Our PoP is based on an economic version of CeC: it limits strength of the wiggler a w to about 0.5 but it is very cost effective G ENESIS parallel computation of electron beam bunching in free electron laser (FEL) shows amplification of modulator signal. VORPAL prediction of the coherent kicker electric field E k due to e-density perturbation from modulator, amplified in the FEL. V ORPAL 3D δ f PIC computation of e- density perturbation near Au +79 ion (green) vs. idealized theory (blue). On Cray XE6 cluster at NERSC. Bunching computed from charge density perturbation & entered into GENESIS FEL simulation. G ENESIS output converted into VORPAL-compatible input. Param.’s from 40 GeV proof-of-principle exp. at BNL Simulations by Tech-X 11

12. Phase 1 – Beamline installation and 112 MHz Cavity Testing

13. First beam from 112 MHz gun – June 2015 1.6-1.7 MeV (kinetic energy) in CW mode Laser-generated CW e-Beam with 3 nC @ 5 kHz 20 MV/m at photocathode It turned out to be a record performance of any CW photo-injector

14. CeC PoP 3D rendering Laser Room (New) PS Building RF and Magnets Utility Building Water/Cryogenic s Beam Line in RHIC IP Service Building Diagnostics Service Building Vacuum

15. Beamline Components

16. Phase 3 - 704 MHz 5 Cell Cavity From Niowave Delivery from Niowave – July 15, 2015 Coax in house being installed FPC welding at AES is finished 704 MHz 5 Cell SRF linac (cryomodule) assembled at NioWave Inc Cliff Brutus welcomes it at IP2

17. Three Helical PM Wigglers at BNL from BINP (Novosibirsk). BINP team visited in July 2015 Left to right: Domenick Milidantry (SMD), Pavel Vobly (BINP), Ray Ceruti (SMD), Igor Ilin, Victor and Sergey Shadrin, Vitalii Zuev (all BINP) and Igor Pinayev (C-AD) near the first assembled helical wiggler

18. We are on the move with CeC PoP

19. Schedule Assembling and tuning helical wigglersV 1/315-Aug-15 Install 704 MHz in RHIC tunnelx15-Nov-15 Install helical wigglers in RHIC tunnelx01-Dec-15 CW laser is commissionedx01-Dec-15 Beam diagnostics is intalled 15-Dec-15 Optical diagnostics is installed 15-Dec-15 Complete CeC beam-lineX15-Dec-15 Commissioning Milestones SRF cavities coldx15-Feb-16 Complete cavity conditioningX15-Mar-16 Generating first beamX01-Apr-16 Measuring beam parametersX15-Apr-16 Propagate beam to the beam dumpx01-May-16 Test co-propagation with ion beamX15-May-16 Demonstrate FEL amplificationX01-Jun-16 First cooling attemptX01-Jul-16

20. Coherent electron cooling promises to boost brightness of hadron beams by orders of magnitude Progress continues on component installation and commissioning of coherent electron cooling experiment 112 MHz SRF CW gun generated electron beam Installing the rest of equipment in 2015 “Classical” CeC test in 2016/2017 Micro-bunching amplification in CeC - 2017 Summary

21. Back-up slides

22. Detecting CeC action Ion bunch – 2 nsec Electron bunch – 10 psec Simulated Au ion beam profile evolution with CeC PoP parameters r.m.s. length of the cooled part 80-120 ps. The cooling effects can 2 GHz (or more) bandwidth using spectrum analyzer or digital scope Well above noise floor

23. Cooling full bunch Self-consistent simulations Preliminary, © G.Wang

24. FEL saturation Bunching amplitude and phase (CeC PoP) Signal grows exponentially until ~ 9 m with gain at 409 and it continues to grow and saturates with gain of 777 @ 11.5 m. Average bunching (short noise) Peak-value of the averaged Green function 10% difference between theoretical estimation and simulation © Y. Jing CeC FEL end

25. Main Beam Parameters for CeC Experiment Parameter Value Species in RHICAu +79 ions, 40 GeV/u Relativistic factor42.96 Number of particles in bucket10 9 Electron energy21.95 MeV Charge per e-bunch0.5-5 nC Rep-rate78.17 kHz Average e-beam current0.39 mA Electron beam power8.6 kW

26. Electron Beam and FEL Parameters for CeC PoP experiment Electron Beam RMS Energy Spread≤ 1×10 -3 Normalized Emittance≤ 5 μm. rad Peak Current60-100 A FEL Wiggler Length3×2.5 m Wiggler Period40 mm Wiggler Strength, a w 0.5 +0.05/-0.1 FEL Wavelength13.6 μm

27. Phase 3: Full Energy Beam Line Installation - 2015 Install 704 MHz Systems and supporting cryogenic system Install Wiggler Magnets Install RHIC beam line components: dipoles, quads, correctors, vacuum Install beam diagnostics Modify and install RHIC DX-DO chamber for FEL light diagnostics Move CeC beam dump line to final location