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Cooling for Hadron Beams Yaroslav Derbenev Thomas Jefferson National Accelerator Facility The 4th EIC Workshop Hampton, May 19-23, 2008 Cooling for HB Outline • • • • • • • • Introduction Stacking positive ions Electron Cooling for eRHIC EC for ELIC Optical Stochastic Cooling Coherent Electron Cooling Thinking on prioritizing the cooling techniques Conclusions Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Preamble: Interaction Region as a Microscope •Beam emittance: --invariant •Luminosity (p-e round beams): f f * * 00 Beam-beam tune shift: * * 2 •Requirement to bunch length: z * b F 2f • • * F f F Small transverse and longitudinal beam emittance allows one to design and use a strong final focus: b* about 5 mm or even shorter can be designed! Chromaticity F Fp / p can be an obstacle, but it can be compensated (we know exactly how to do so!) The (6D) emittance is a subject to change by cooling! Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 f What is Beam Cooling? • One needs a media with which the beam should interact incoherently • An individual charged particle creates an effective charge polarization of the media (image charge) • In response, particle motion is effected by the image field, that decelerates the particle relatively the beam frame - this is cooling! • Feedback with the right receiver - kicker phasing can be used in order to amplify the response • Influence of image fields from particle neighbors can only decrease the cooling effect (shield effect) • The achievable cooling rate and equilibrium is limited by noise in the media and amplifier Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 What cooling does for luminosity? • Decrease of beam emittances (up to reaching the beam-beam or intra-beam space charge limit) • Preventing the beam blow-up by IBS and other slow heaters • Small transverse emittance allows one to design a tight star-focus (more beam extension is available in final quadrupoles) • Short bunches allow one to: - use the designed low beta-star (no “hour glass”) - implement the crab-crossing beams – hence, increase the bunch collision rate • Beam stacking after linac (works for all species!) Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Cooling techniques and ideas Maxwell-Lorentz demon Radiation Cooling (RC) 1950th works in e± colliders, can be used in LHC.. Shrinking before plague (muons…) Ionization Cooling (IC) 1966/1981 Electron Cooling (EC) 1966 Stochastic Cooling (SC) under development towards the Neutrino Factory and Muon Collider! Thermostat of the relativistic engineer -used at low and medium energies -under development for colliders van der Meer’s demon (RF feedback) used 1968 Coherent Electron Cooling (CEC) 1980 Spoiled hybrid of EC and SC development just started… Optical Stochastic Cooling (OSC) 1993 Max’s demon (RC+optical feedback) development to start… Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Electron Cooling: The thermostat of a relativistic engineer Do not renounce from prison and money bag Landau liked to call me “The relativistic engineer”, I am very proud of that. Gersh Budker Kinetic equation (plasma relaxation) was derived by Landau in 1937. But… can it work for beams? It does! Yet very interesting and important phenomena have been discovered (magnetized cooling, super-deep cooling, christaline beams…) Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Stochastic cooling The van der Meer’s demon “Is n’t it the Maxwell’s demon?” (G.Budker) ( c ) N 2f It works!! •Works well for a coasted low current, large emittance beams. •Can it work for bunched beams? Hardly… but demonstrated by M.Blaskewitz for lead at RHIC! •May help ELIC (eRHIC?) (stacking and precooling of the coasted beam)…? Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Stochastic Cooling rate as function of # pbars (‘Fast Schottky’) Fast V Fast H 0.0 -0.5 -1.0 -1.5 2-4 GHz vertical -2.0 -2.5 Np = 186e10 Np = 124e10 Np = 51e10 Cooling rate [ mm mrad per hour] Cooling rate [ mm mrad per hour] Fast H 0.0 -0.5 -1.0 -1.5 2-4 GHz horizontal -2.0 -2.5 Np = 186e10 Np = 124e10 Cooling rate [ mm mrad] Fast H A 1/N-like dependence is clearly visible for the 2-4 GHz system but not for the other two systems (although the 1-2 GHz system shows some dependence on the # of pbars) Np = 51e10 Fast V 0.0 -0.5 -1.0 -1.5 1-2 GHz horizontal -2.0 -2.5 Np = 186e10 Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May Fast V Np = 124e10 Np = 51e10 400 3.5 350 3 300 2.5 250 2 200 1.5 150 1 100 0.5 50 0 0 Vertical e-beam offset, mm Number of antiprotons, E10 EC in Fermilab’s Recycler ring Electron cooling is used at the Recycler for cooling 8 GeV pbars 4.34 MeV, 0.1 A DC electron beam Primarily longitudinal cooling To free space for the next antiproton injection from Accumulator ring -0.5 0 5 10 15 20 140 14 120 12 100 10 80 8 60 6 40 4 20 2 0 0 0 5 10 15 Hor. emittance, mm*mrad Long. emittance, eVs Time, hr 20 Time, hr Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May Cooling strength is regulated by a vertical offset of the electron beam in the cooling section Most of the time, e- beam is shifted by ~2 mm to maximize the life time Moved on axis before extraction to minimize emittances of the extracted beam Forming high current ion beams (agenda in general) 1.Stacking in pre-booster or an accumulator ring 2. Accelerating in the pre-booster and large booster 3. Pre-cooling in collider ring at injection energy 4. Continuous cooling in collider mode Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Stacking ions • 1A ion current is required for high luminosity • Stripping injection into pre-booster can be used for proton and deuteron beam • Accumulation of He and other ions only is possible at use of beam cooling • Stochastic cooling of 1A beam is too slow • The DC EC (or CEC) is promising! • There is an experience: - Accumulating polarized protons from positive source in IUCF Proton Cooler Ring - Electron cooling of 3.10^12 pbar’s in Recycler ring of FNAL • An issue for beam accumulation in pre-booster at 200 MeV/n: large emittance caused by the space charge… This emittance cannot be “managed” by Electron pre-Cooling in collider ring • A solution seems to exist… Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Stochastic Cooling and Stacking of Ions An optimistic scenario Multi-turn (10 – 20) injection from 285 MeV SRF linac to pre-booster Stochastic damping of injected beam Accumulation of 1 A coasted beam at space charge limited emittance RF bunching and accelerating to 3 GeV Inject into large booster Fill large booster, accelerate to 30 GeV Inject into collider ring Transverse stochastic cooling of 1 A coasted ion beam in collider ring Stacking proton beam in prebooster with stochastic cooling Beam Energy MeV 200 % 1 Pulse current from linac mA 20 Cooling time min 1.5 Accumulated current A 1 Stacking cycle /fill LB duration min 4/60 Beam emittance, norm. μm 12 Momentum Spread Laslett tune shift At this stage, Ion beam is ready for electron cooling Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 0.03 Stacking positive ions by use of DC EC Stacking of positive fully stripped polarized and unpolarized ions can be realized in the accumulator-cooler ring (ACR) with electron cooling. Such method has been successfully used for accumulating of polarized beam in Proton Cooler Ring of IUCF Accumulator Ring with DC EC Design advancements : Circumference Arc radius Crossing straights length Energy/u Electron current Electron energy Cooling time for protons Stacked ion current Large norm.emittance after stacking Accumulation time m m m MeV A KeV ms A µm s 50 3 2 x 15 200 1 100 10 1 16 10 Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Beam stacking in one o f two circular modes matched with solenoid of cooling section This concept allows one to overcome space charge limit on 4D emittance, hence, increase EC precooling rate in collider ring Requirements for eRHIC 1. Protons (250 GeV): Bunch intensity: 2e11 95%, normalized emittance: 6 mm Rms bunch length: 0.2 m Peak luminosity: 2.6e33 2. Au ions (100 GeV): Bunch intensity: 1.1e9 95%, normalized emittance: 2.4 mm Rms bunch length: 0.2 m Peak luminosity: 2.9e 33 Requires pre-cooling: Au ions: factor of 6 reduction in initial emittance Protons: factor of 3-2 reduction in initial emittance Such electron cooling is possible based on RHIC-II electron cooler with 703 MHz SRF gun. Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Pre-cooling of Au ions (N=1e9) Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Pre-cooling of protons (N=2e11) Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Electron cooling section at RHIC 2 o’clock IP RHIC triplet solenoids RHIC triplet e- 100 m ` IP 2 helical wigglers e- Each electron beam cools ions in Yellow ring of RHIC then the same beam is turned around and cools ions in Blue ring of RHIC. Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 e- ERL 10 m Energy Recovery Linac (ERL) for RHIC-II Cooling of Au ions at 100 GeV/n: • 54.3 MeV electron beam • 5nC per bunch • rms normalized emittance < 4 mm • rms momentum spread < 5×10-4 Courtesy D. Kayran D. Kayran, PAC07 Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 R&D ERL at BNL 0.5 ampere SRF gun – under construction 703 MHz 5 cell SRF cavity designed by BNL and fabricated by Advanced Energy Systems. The cavity has reached its specification of 20 MV/m at a Q of 1×1010 . 5 cell cavity successfully processed Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 EC Test bed for RHIC-II and eRHIC Commissioning starts February 2009 Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Circulated Electron Cooling of ELIC Max/min energy of e-beam MeV 125/8 Electrons/bunch 1010 1 Number of bunch revolutions in CCR solenoid ion bunch Current in CCR/ERL A 3/0.03 MHz 1500/15 CCR circumference m 80 Cooling section length m 20 Circulation duration ms 27 Bunch length cm 1-3 Energy spread 10-4 1-3 T 2 Beam radius in solenoid mm 1 Cyclotron beta-function m 0.6 Thermal cyclotron radius mm 2 Beam radius at cathode mm 3 Solenoid field at cathode KG 2 Bunch repetition rate in CCR/ERL circulator cooler ring (CCR) electron bunch Cooling section Solenoid field in cooling section kicke r kicke r energy recovery path SRF Linac 100 Laslett’s tune shift in CCR at 10 MeV Time of longitudinal inter/intra beam heating electron injector dum p 0.03 ms 200 • CCR makes 100 time reduction of beam current from injector/ERL • Fast kickers operated at 15 MHz repetition rate and 2 GHz frequency bend width are required Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Cooling Time and Ion Equilibrium Cooling rates and equilibrium of proton beam Multi-stage cooling scenario: • 1st stage: longitudinal cooling at injection energy (after transverses stochastic cooling) • 2nd stage: initial cooling after acceleration to high energy • 3rd stage: continuous cooling in collider mode Parameter Unit Energy GeV/MeV Valu e Value 30/1 225/123 5 Particles/bunch 1010 0.2/1 Initial energy spread* 10-4 30/3 1/2 Bunch length* cm 20/3 1 Proton emittance, norm* mm 1 1 Cooling time min 1 1 mm 1/1 1/0.04 Equilibrium bunch length** cm 2 0.5 Cooling time at equilibrium min 0.1 0.3 0.04 0.02 Equilibrium emittance , ** x / y Laslett’s tune shift (equil.) * max.amplitude ** norm.,rms Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Electron Cooling of Ions in ELIC Staged cooling Start electron cooling (longitudinal) in collider ring at injection energy, Continue electron cooling (in all dimension) after acceleration to high energy Sweep cooling • • dN p (t 0) dN p (t ) dv|| dv|| After transverse stochastic cooling, ion beam has a small transverse temperature but large longitudinal one. Use sweep cooling to gain a factor of longitudinal cooling time 0 F(v ) v e (t ) Dispersive cooling Compensates for lack of transverse cooling rate at high energies Flat beam cooling Based on flattening ion beam by reduction of coupling IBS rate at equilibrium becomes reduced compared to cooling rate Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 v Injector and ERL for EC in ELIC • • • • ELIC CCR driving injector 30 mA@15 MHz, up to 125 MeV energy, 1 nC bunch charge, magnetized Challenges Source life time: 2.6 kC/day (state-of-art is 0.2 kC/day) source R&D, & exploiting possibility of increasing evolutions in CCR High beam power: 3.75 MW Energy Recovery Conceptual design High current/brightness source/injector is a key issue of ERL based light source applications, much R&D has been done We adopt light source injector as initial baseline design of ELIC CCR driving injector Beam qualities should satisfy electron cooling requirements (based on previous computer simulations/optimization) SRF modules solenoids 500keV DC gun buncher quads Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Fast Kicker for Circulator Cooling Ring • • • • • Sub-ns pulses of 20 kW and 15 MHz are needed to insert/extract individual bunches. RF chirp techniques hold the best promise of generating ultra-short pulses. State-of-Art pulse systems are able to produce ~2 ns, 11 kW RF pulses at a 12 MHz repetition rate. This is very close to our requirement, and appears to be technically achievable. Helically-corrugated waveguide (HCW) exhibits dispersive qualities, and serves to further compress the output pulse without excessive loss. Powers ranging from up10 kW have been created with such a device. Estimated parameters for the kicker Beam energy MeV 125 Kick angle 10-4 3 Integrated BdL GM 1.25 Frequency BW GHz 2 Kicker Aperture Cm 2 Peak kicker field G 3 Kicker Repetition Rate MHz 15 Peak power/cell KW 10 Average power/cell W 15 Number of cells 20 20 Collaborative development plans include studies of HCW, optimization of chirp techniques, and generation of 1-2 kW peak output powers as proof of concept. kicker Kicker cavity design will be considered Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 kicker Coherent Electron Cooling or how the van der Meer’s demon can spoil thermostat of the relativistic engineer Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 History of CEC idea (1980-91-95-2007) Coherent electron cooling (CEC) was proposed 27 years ago • General idea: amplify response of ebeam to an ion by a micro-wave instability of the beam • A few instabilities have been shown • CEC advantages/disadvantages compared to: EC : Gain in cooling rate Complicate BT SC : Very large FB (30 GHz – optics) Precise phasing required OSC : Effective in a wide energy range Small signal delay Intense e-beam required Signal gain is limited What changed in last 10 years? • Relativistic DC EC realized (FNAL) • ERL realized (JLab) • SASE FEL realized (UCLA - DESY) • ERL-based HEEC on the way (BNL) And more… Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 FELs and HEEC And so, my fellow FELers, ask not what storage ring can do for FELs: Ask what FELs can do for your storage rings! Vladimilr Litvinenko 29th International FEL Conference August 26-31, 2007, BINP, Novosibirsk Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 And so, my fellow Americans, ask not what your country can do for you; ask what you can do for your country. Optical stochastic cooling (OSC) Max’s demon (by Max Zolotorev, 1993) ----Proton radiates light in undulator (“receiver”) ----optical amplifier------“proton interacts with the amplified light in the end undulator “kicker”) 2000 - OSC considered for cooling of halo particles in the VLHC, by Barletta, Chattopadhyay, Zholents, Zolotorev Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Why we need OSC if we have electron cooling 1.5 10 Cooling rate Beam profile 8 . 1 OSC 6 4 0.5 . Electron cooling 0 0 2 4 6 8 2 10 0 4 2 0 2 4 Optical stochastic cooling can effectively reduce number of the particles in the beam tails. This will increase lifetime of the beam and reduce detectors background. Custom beam shaping might be possible. Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Optical Stochastic Cooling Horizontal and longitudinal cooling time 1hr for the full gold beam requires 16W of power l = 12 mm Bandwidth ~ 3 THz LDRD test at ATF for Optical Parametric Amplification Gold beam Optical amplifier on 3.5 cm CdGeAs2 crystal with d14=236 pV/m s p p s Pump laser i = p - s; kp = k s + ki Amplified signal Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Freshly grown crystals at Lockheed Sanders, NH Optical Parametric Amplifier OPA 3 cm length crystal → intensity gain 3 105 Parametric process is photon interaction in which one high frequency photon is annihilated and two lower frequency photons are created, i.e.: (pump) =(signal) +(idler) where photon energy is conserved. In addition, photon momentum is conserved by the wave vectors: k(pump) =k(signal) +k(idler) . Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Critical studies on Cooling for Hadrons • Pre-cooling for eRHIC: Non-magnetized, space charge dominated e-beam transport • CEC for eRHIC: all physics and design • EC for ELIC: ERL - CCR super-fast kicker for e-beam • OSC (of “beam halo”): Parametric optical amplifier • SC for beam stacking and pre-cooling (ELIC): Limits for coasted beams • DC EC (and CEC) for beam stacking (alternative to SC): Accumulator-cooler design and all beam physics Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 My view of Current prioritization of potential employment of cooling techniques at EIC by taking into account : Potential efficiency + Conceptual readiness + Proximity to realization Service: Stacking Pre-cooling Core Cooling Tail cooling I DC EC HE EC CR EC OSC II DC CEC CR EC HE CEC HE CEC III SC SC IV HE CEC HE EC EC – electron cooling; DC - direct current; HE - high energy (ERL based) CR – cirulator ring; CEC - coherent EC; SC - stochastic cooling; OSC - optical stochastic cooling Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Conclusions • The studies and designs of cooling for EIC are getting mature. The projects are well profiled in the goals and expected performance. • The engineering works and test studies for 1 hundred MeV scale ERL started at BNL. A prototype of ERL will be built, which, as minimum, will serve pre-cooling of ions to reach luminosity in eRHIC. • Conceptual development of 125 MeV ERL + Circulator Ring scheme of electron cooling for ELIC will finalize soon (in 1-1.5 year) at JLab. Could such scheme also be implemented in eRHIC to raise the cooler efficiency? Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Conclusions (cont-d) • Recent development of Optical Stochastic Cooling brings a realistic promise to extend luminosity lifetime and ease the EC design, by cooling beam tail. The OSC, however, can work only in a relatively narrow beam energy region of the collider ring. • The new perspectives for cooling hadron beams in colliders seem to be open with development of the Coherent Electron Cooling, which starts at BNL. It invites SASE FEL amplifier to cooling section of a collider. • The efficiency of colliders can be frequently increased by stacking positive ions in a small ring after linac. Here, the EC or CEC on a non-relativistic DC e-beam could be employed to accumulate 1 A level of ion current. Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 We entering an exciting era of the new generation of high luminosity colliding beams provided by the Advanced cooling techniques! Thank you! Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008 Making sense of the different cooling techniques •Stochastic Cooling: beam error signal is measured by a pickup, amplified by RF amplifier and corrected in the kicker Works over wide range of the ion beam energies Can be used for stacking Limited by amplifier bandwidth ~5GHz Possibly can cool only tails of the RHIC beam • Optical SC: Similar to SC, but at optical wavelength Not limited by amplifier bandwidth ~3THz Can cool whole RHIC beam in one hour with16W of optical power Favors large amplitudes, Greatly reduces requirements on electron current if used with EC Works only over limited ~5-10% range of the ion beam energies Requires challenging RHIC lattice modifications No demo, yet •Electron cooling: ion beam “heat” transferred to “cold” electron beam Works over wide energy range Effective for the beam core and against IBS (faster cooling for the colder beam) Complimentary with OSC as it effective against IBS (main growth in RHIC) Requires ERL and long solenoid High e-efficiency in the ERL+CCR advance scheme Can be used for stacking Was not demonstrated at high energies • Coherent Electron Cooling: response of e-beam to an ion is amplified by a microwave instability of the e-beam (SASE FEL) Strong image interaction Very large FB (30 GHz – optics) Effective in a wide energy range Small signal delay Requires high current ERL Signal gain is limited Needs more study, no demo yet Ya. Derbenev /TJNAF/ . 4th EIC Workshop, Hampton, May 2008