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Design Status of ELIC G. A. Krafft for ELIC Design Team and Medium Energy Collider Design Team

Design Status of ELIC G. A. Krafft for ELIC Design Team and Medium Energy Collider Design Team Jefferson Lab Physics Seminar Feb 6, 2009. Outline. ELIC: An Electron-Ion Collider at CEBAF Basic parameters List of recent developments/specs Some R&D Issues Electron Cooling

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Design Status of ELIC G. A. Krafft for ELIC Design Team and Medium Energy Collider Design Team

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  1. Design Status of ELIC G. A. Krafft for ELIC Design Team and Medium Energy Collider Design Team Jefferson Lab Physics Seminar Feb 6, 2009

  2. Outline • ELIC: An Electron-Ion Collider at CEBAF • Basic parameters • List of recent developments/specs • Some R&D Issues • Electron Cooling • Crab Crossing • Medium Energy Colliders and Staging • Summary

  3. ELIC Study Group & Collaborators A. Afanasev, A. Bogacz, P. Brindza, A. Bruell, L. Cardman, Y. Chao, S. Chattopadhyay, E. Chudakov, P. Degtiarenko, J. Delayen, Ya. Derbenev, R. Ent, P. Evtushenko, A. Freyberger, D. Gaskell, J. Grames, A. Hutton, R. Kazimi, G. A. Krafft, R. Li, L. Merminga, J. Musson, M. Poelker, R. Rimmer, Chaivat Tengsirivattana, A. Thomas, H. Wang, C. Weiss, B. Wojtsekhowski, B. Yunn, Y. Zhang - Jefferson Laboratory W. Fischer, C. Montag - Brookhaven National Laboratory V. Danilov - Oak Ridge National Laboratory V. Dudnikov - Brookhaven Technology Group P. Ostroumov - Argonne National Laboratory V. Derenchuk - Indiana University Cyclotron Facility A. Belov - Institute of Nuclear Research, Moscow, Russia V. Shemelin - Cornell University

  4. Jefferson Lab Now

  5. RHIC Lab Now

  6. ELIC Design Goals • Energy • Center-of-mass energy between 20 GeV and 90 GeV • energy asymmetry of ~ 10,  3 GeV electron on 30 GeV proton/15 GeV/n ion up to 10 GeV electron on 250 GeV proton/100 GeV/n ion • Luminosity • 1033 up to 1035 cm-2 s-1per interaction point • Ion Species • Polarized H, D, 3He, possibly Li • Up to heavy ion A = 208, fully stripped • Polarization • Longitudinal polarization at the IP for both beams • Transverse polarization of ions • Spin-flip of both beams • All polarizations >70% desirable • Positron Beamdesirable

  7. Evolutionof the Principal Scheme • Energy Recovery Linac-Storage-Ring (ERL-R) • ERL with Circulator Ring – Storage Ring (CR-R) • Back to Ring-Ring (R-R) – by taking CEBAF advantage as full energy polarized injector • Challenge: high current polarized electron source • ERL-Ring: 2.5 A • Circulator ring: 20 mA • State-of-art: 0.1 mA • 12 GeV CEBAF Upgrade polarized source/injector already meets beam requirement of ring-ring design • CEBAF-based R-R design still preserves high luminosity, high polarization (+polarized positrons…)

  8. ELIC Conceptual Design prebooster 30-225 GeV protons 15-100 GeV/n ions 12 GeV CEBAF Upgrade Green-field design of ion complex directly aimed at full exploitation of science program. 3-9 GeV electrons 3-9 GeV positrons

  9. ELIC Ring-Ring Design Features • Unprecedented high luminosity • Enabled by short ion bunches, low β*, high rep. rate • Large synchrotron tune • Require crab crossing • Electron cooling is an essential part of ELIC • Four IPs (detectors) for high science productivity • “Figure-8” ion and lepton storage rings • Ensure spin preservation and ease of spin manipulation • No spin sensitivity to energy for all species.

  10. Achieving High Luminosity of ELIC ELIC design luminosity L~ 2.6 x 1034 cm-2 sec-1 (150 GeV protons x 7 GeV electrons) ELIC luminosity Concepts • High bunch collision frequency (f=0.5 GHz) • Short ion bunches (σz ~ 5 mm) • Super strong final focusing (β* ~ 5 mm) • Large beam-beam parameters (0.01/0.086 per IP, 0.025/0.1 largest achieved) • Need High energy electron cooling of ion beams • Need crab crossing • Large synchrotron tunes to suppress synchro-betatron resonances • Equidistant phase advance between four IPs

  11. ELIC (e/p) Design Parameters Electron parameters are red

  12. ELIC (e/A) Design Parameters * Luminosity is given per nucleon per IP

  13. Electron Polarization in ELIC spin rotator spin rotator spin rotator with 90º solenoid snake collision point collision point collision point collision point spin rotator with 90º solenoid snake spin rotator spin rotator • Produced at electron source • Polarized electron source of CEBAF • Preserved in acceleration at recirculated CEBAF Linac • Injected into Figure-8 ring with vertical polarization • Maintained in the ring • High polarization in the ring by electron self-polarization • SC solenoids at IPs removes spin resonances and energy sensitivity.

  14. Electron Polarization in ELIC (cont.) Electron/positron polarization parameters * Time can be shortened using high field wigglers. ** Ideal max equilibrium polarization is 92.4%. Degradation is due to radiation in spin rotators.

  15. Positrons in ELIC Transverse Transverse emittance emittance 10 10 MeV MeV filter filter e+ e+ 5 5 MeV MeV Longitudinal Longitudinal emittance filter emittance filter converter converter e e - - polarized polarized source source 15 15 MeV MeV e e - - e e - - e e - - e e - - e+ e+ e+ e+ e+ e+ dipole dipole dipole dipole dipole dipole 115 115 MeV MeV e e - - During positron production: - Polarized source is off - Dipoles are turned on 15 15 MeV MeV unpolarized unpolarized source source • Non-polarized positron bunches generated from modified electron injector through a converter • Polarization realized through self-polarization at ring arcs

  16. Figure-8 Ion Ring (half) - Lattice at 225 GeV phase adv./cell (Dfx= 600, Dfy=600) 3 transition cells 42 full cells 3 transition cells 11 empty cells 11 empty cells Arc dipoles:: $Lb=170 cm $B=73.4 kG $rho =102 m Arc quadrupoles: $Lb=100 cm $G= 10.4 kG/cm • Minimum dispersion (periodic) lattice • Dispersion suppression via ‘missing’ dipoles (geometrical) • Uniform periodicity of Twiss functions (chromatic cancellations) • Dispersion pattern optimized for chromaticity compensation with sextupole families (3 × 600 = 1800)

  17. Figure-8 Electron Ring (half) - Lattice at 9 GeV phase adv./cell (Dfx= 1200, Dfy=1200) 83 empty cells 83 empty cells 54 superperiods (3 cells/superperiod) • ‘Minimized emittance dilution due to quantum excitations • Limited synchrotron radiated power (14.3MW (total) @ 1.85A) • Quasi isochronous arc to alleviate bunch lengthening (a~10-5) • Dispersion pattern optimized for chromaticity compensation with sextupole families Arc dipoles:: $Lb=100 cm $B=3.2 kG $rho =76 m Arc quadrupoles: $Lb=60 cm $G= 4.1 kG/cm

  18. Figure-8 Rings – Vertical ‘Stacking’

  19. 0.5m 3.2kG/cm 0.2m 22.2 mrad 1.27 deg 3.8m 0.6m 2.55kG/cm 8.4cm 10cm IP 1.8m 20.8kG/cm 22.9cm 3m 12KG/cm Vertical intercept Vertical intercept 14.4cm 16.2cm 4.5m Vertical intercept electron 4mm 5mm ion IP Magnet Layout and Beam Envelopes β*OK

  20. Electron (9GeV) 2.4cm 2.4cm 8.6cm 14cm 4.6cm 10 cm 10cm 4.8cm 3cm Proton (225GeV) 3cm 1.8m 20.8kG/cm 1st SC focusing quad for ion IR Final Quad Optimization • IP configuration optimization • “Lambertson”-type final focusing quad • angle reduction: 100mrad  22mrad Paul Brindza

  21. Lambertson Magnet Design Cross section of quad with beam passing through magnetic Field in cold yoke around electron pass.

  22. β Chromaticity correction with sextupoles β- functions around the interaction region, the green arrows represent the sextupoles pairs. The phase advance, showing the –I transformation between the sextupoles pairs

  23. Local Correction of Transfer Map Phase space in both transverse planes before and after applying the sextupoles Vertical plane Δp/p~0.0006 phase space after one pass through 2 IR’s No correction phase space after one pass through 2 IR’s after correction Initial phase space Y` Y

  24. Beam-Beam Effect in ELIC Electron bunch IP Proton bunch Electron bunch proton bunch y x Transverse beam-beam force • Highly nonlinear forces • Produce transverse kicks between colliding bunches Beam-beam effect • Can cause size/emittance growth or blowup • Can induce coherent beam-beam instabilities • Can decrease luminosity and its lifetime Impact of ELIC IP design • Highly asymmetric colliding beams (9 GeV/2.5 A on 225 GeV/1 A) • Four IPs and Figure-8 rings • Strong final focusing (beta* 5 mm) • Short bunch length (5 mm) • Employs crab cavity • vertical b-b tune shifts are 0.087/0.01 • Very large electron synchrotron tune (0.25) due to strong RF focusing • Equal betatron phase advance (fractional part) between IPs One slice from each of opposite beams Beam-beam force

  25. Beam-Beam Simulations(cont.) • Simulation Model • Single/multiple IPs, head-on collisions • Strong-strong self consistent Particle-in-Cell codes, developed by J. Qiang of LBNL • Ideal rings for electrons & protons, including radiation damping & quantum excitations for electrons • Scope and Limitations • 10k ~ 30k turns for a typical simulation run • 0.05 ~ 0.15 s of storing time (12 damping times)  reveals short-time dynamics with accuracy  can’t predict long term (>min) dynamics • Simulation results • Saturated at 70% of peak luminosity, 5.8·1034 cm-2s-1, the loss is mostly due to the hour-glass effect • Luminosity increase as electron current linearly (up to 6.5 A), coherent instability observed at 7.5 A • Luminosity increase as proton current first linearly then slow down due to nonlinear b-b effect, electron beam vertical size/emittance blowup rapidly • Simulations with 4 IPs and 12-bunch/beam showed stable luminosity and bunch sizes after one damping time, situated luminosity is 5.5·1034cm-2s-1 per IP, very small loss from single IP and Single bunch operation Supported by SciDAC 4IPs, 12 bunches/beam

  26. ELIC Additional Key Issues • To achieve luminosity at 1033 cm-2 sec-1 and up • High energy electron cooling • To achieve luminosity at ~ 1035 cm-2 sec-1 • Circulator Cooling • Crab cavity • Stability of intense ion beams

  27. ELIC R&D: Forming Intense Ion Beam Use stochastic cooling for stacking and pre-cooling • Stacking/accumulation process • Multi-turn (10 – 20) injection from SRF linac to pre-booster • Damping of injected beam • Accumulation of 1 A coasted beam at space charge limited emittence • RF bunching/acceleration • Accelerating beam to 3 GeV, then inject into large booster • Ion space charge effect dominates at low energy region • Transverse pre-cooling of coasted beam in collider ring (30 GeV) Stacking proton beam in pre-booster with stochastic cooling Transverse stochastic cooling of coasted proton beam after injection in collider ring

  28. Injector and ERL for Electron Cooling SRF modules solenoids 500keV DC gun buncher quads • 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)

  29. Electron Cooling with a Circulator Ring .Effective for heavy ions (higher cooling rate), difficult for protons. • State-of-Art • Fermilab electron cooling demonstration (4.34 MeV, 0.5 A DC) • Feasibility of EC with bunched beams remains to be demonstrated • ELIC Circulator Cooler • 3 A CW electron beam, up to 125 MeV • SRF ERL provides 30 mA CW beam • Circulator cooler for reducing average current from source/ERL • Electron bunches circulate 100 times in a ring while cooling ion beam • Fast (300 ps) kicker operating at 15 MHz rep. rate to inject/eject bunches into/out circulator-cooler ring

  30. Fast Kicker for Circulator Cooling Ring Estimated parameters for the kicker • 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. • 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 cavity design will be considered kicker kicker

  31. 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 * max.amplitude ** norm.,rms

  32. ELIC R&D: Crab Crossing • High repetition rate requires crab crossing to avoid parasitic beam-beam interaction • Crab cavities needed to restore head-on collision & avoid luminosity reduction • Minimizing crossing angle reduces crab cavity challenges & required R&D State-of-art: KEKB Squashed cell@TM110 Mode Crossing angle = 2 x 11 mrad Vkick=1.4 MV, Esp= 21 MV/m

  33. ELIC R&D: Crab Crossing (cont.) Crab cavity development Electron: 1.2 MV – within state of art (KEK, single Cell, 1.8 MV) Ion: 24 MV (Integrated B field on axis 180G/4m) Crab Crossing R&D program • Understand gradient limit and packing factor • Multi-cell SRF crab cavity design capable for high current operation. • Phase and amplitude stability requirements • Beam dynamics study with crab crossing

  34. ELIC at JLab Site WM Symantec City of NN VA State 920 m City of NN 360 m SURA JLab/DOE

  35. http://casa.jlab.org/research/elic/elic_zdr.doc

  36. “EICC” Proposal to Machine Groups (after EIC workshop at Hampton University: not an official EICC recommendation, but rather an informal proposal from Abhay Deshpande, Richard Milner, Rolf Ent) • eRHIC: • 1) Back to drawing board given unrealistic demands of the source. • 2) Request staging of 5+ GeV with 1032+ luminosity + cost estimates, • with appropriate upgrade paths for luminosity and energy • (including changing the RF/optics of the RHIC machine). • ELIC: • 1) 1.5 GHz seems unrealistic, 0.5 GHz may be doable. • 2) Request polarization tracking with full lattice. • 3) Request consideration of staging options, if any. • In addition, request both for estimate of achievable vacuum levels asap.

  37. MEIC “Design” Group • A. Bogacz, Ya. Derbenev, R. Ent, G. Krafft T. Horn, • C. Hyde, A. Hutton, F. Klein, P. Nadel-Turonski, • A. Thomas, C. Weiss, Y. Zhang

  38. Motivations Science • Expand science program beyond 12 GeV CEBAF fixed target program • Gluons via J/ψ production • Higher CM energy in valence region • Study the asymmetric sea for x≈m/MN Accelerator • Bring ion beams and associated technologies to JLab (a lepton lab) • Have an early ring-ring collider at JLab • Provides a test bed for new technologies required by ELIC • Develop expertise and experience, acquire/train technical staff Staging Possibilities • A medium energy EIC becomes the low energy ELIC ion complex • Exploring opportunities for reusing Jϋlich’s Cooler Synchrotron (COSY) complex for cost saving

  39. Design Goals

  40. Stage 1: Low Energy Collider • A compact booster/storage ring of 300 m length will be used for accumulating, boosting and cooling up to 2.5 GeV/cu (Z/A=1/2) ion beams or 5 GeV/c protons from an ion source and SRF injection linac. • Full injection energy electron storage ring and the ion ring act as collider rings for electron-ion collisions • More compact size enables storing higher ion beam current for the same Laslett space charge tune-shift • Two compact rings of 300 m length • Collision momenta up to 5 GeV/c for electrons & (Z/A)×5 GeV/cu for ions • Electron & stochastic cooling • One IP IP SRF Linac e p Ion Sources Booster/collider ring Electron injector 12 GeV CEBAF

  41. MEIC & Staging of ELIC: Alternative Pass The tunnel houses 3 rings: Electron ring up to 5 GeV/c Ion ring up to 5 GeV/c Superconducting ion ring for up to 30 GeV/c p p Figure-8 collider ring e e e Ion Sources p SRF Linac Electron injector 12 GeV CEBAF High Energy IP Low Energy IP (Ya. Derbenev, etc.) • Low energy collider (stage 1)  (up to 5GeV/c for both e and i) Both e and p in compact ring (~ 300 m) • Medium energy collider (stage 2) (up to 5GeV/c for e, 30 GeV/c for i) Compact superconducting ion ring (~ 300 m) • Medium energy collider (Stage 3) (up to 11 GeV/c for e, 30 GeV/c for i) Large Figure-8 electron ring (1500 m to 2500 m) • High energy collider (stage 4) (up to 11 GeV/c for e, 250 GeV/c for i) Large Figure-8 super conducting ion ring (Full ELIC)

  42. Medium Energy EIC Features • High luminosity collider • CM energy region from 10 GeV (5x5 GeV) to 22 GeV (11x11 GeV), and possibly reaching 35 GeV (30x10 GeV) • High polarization for both electron and light ion beams • Natural staging path to high energy ELIC • Possibility of positron-ion collider in the low to medium energy region • Possibility of electron-electron collider (7x7 GeV) using just small 300 m booster/collider ring

  43. Luminosity Design luminosity L~ 2×1033 cm-2s-1 (9 GeV protons x 9 GeV electrons) Limiting Factors • Space charge effect for low ion energy • Electron beam current due to synchrotron radiation • Beam-beam effect Luminosity Concepts • High bunch collision frequency (up to 0.5 GHz) • Long ion bunches with respect to β* for high bunch charge (σz ~ 5 cm) • Super strong final focusing (β* ~ 2.5 mm to 5 mm) • Large beam-beam parameters (0.015/0.1 per IP for p and e) • Need staged cooling for ion beams • Need crab crossing colliding beams • Need “traveling focusing” to suppress the hour-glass effect

  44. Parameter Table Electron parameters are red

  45. Production of Ion Beam • One Idea • SRF to 50 to 300 MeV/c • Accumulate current in Low Energy Ring • Accelerate to final energy • Store in Low Energy Ring or send on to next ring • Another Idea • Accelerate to ~ 2 GeV/c in an SRF linac • Accumulate current in Low Energy Ring • Accelerate to final energy • Store in Low Energy Ring or send on to next ring

  46. Interaction Region: Simple Optics Mon Dec 01 12:30:09 2008 OptiM - MAIN: - N:\bogacz\Pelican\IR_ion_LR.opt Mon Dec 01 12:26:08 2008 OptiM - MAIN: - N:\bogacz\Pelican\IR_ion_LR.opt 2 2 5 12000 bmax ~ 9 km bmax ~ 9 km Size_X[cm] Size_Y[cm] BETA_X&Y[m] DISP_X&Y[m] b┴* = 5mm b┴* = 5mm s* = 14mm f ~ 7 m f ~ 7 m 0 0 0 0 0 Ax_bet Ay_bet Ax_disp Ay_disp 31.22 0 BETA_X BETA_Y DISP_X DISP_Y 31.22 8 m 8 m • Beta functions • Beam envelopes (σRMS) for εN = 0.2 mm mrad s* = 14mm • Triplet based IR Optics • first FF quad 4 m from the IP • typical quad gradients ~ 12 Tesla/m for 5 GeV/c protons • beam size at FF quads, σRMS ~ 1.6 cm

  47. Interaction Region: Crab Crossing • High bunch repetition rate requires crab crossing colliding beam to avoid parasitic beam-beam interactions • Crab cavities needed to restore head-on collision & avoid luminosity reduction • Since ion beam energy now is a factor of 15 lower than that of ELIC, integrated kicking voltage is at order of 1 to 2 MV, within the state-of-art (KEK) • No challenging cavity R&D required State-of-art: KEKB Squashed cell@TM110 Mode Crossing angle = 2 x 11 mrad Vkick=1.4 MV, Esp= 21 MV/m

  48. Interaction Region: Traveling Focusing slice 1 F1 slice 1 slice 2 sextupole F2 slice 2 • Under same space charge tune-shift limit, we need to increase ion bunch length in order to increase bunch charge, and hence increase luminosity • Hour glass effect would normally kill collider luminosity if ion bunch length is much large than β* • “Traveling Focusing” scheme can mitigate hour-glass effect by moving the final focusing point along the long ion bunch. This setup enables the short electron bunch to collide with different slices of the long ion bunch at their relative focusing points • Nonlinear elements (sextupoles) working with linear final focusing block produce non-uniform focus length for different slices of a long bunch Brinkmann and Dohlus, Ya. Derbenev, Proc. EPAC 2002

  49. COSY as Pre-Booster/Collider Ring New superperiod Preserve ring optics • COSY complex provides a good solution for the EIC pre-booster/low energy collider ring • Adding 4 dipoles on each arc can bring maximum momentum of COSY synchrotron from 3.7 GeV/c to 5 GeV/c, while still preserving its optics • COSY existing cooling facilities can be reused

  50. mEIC@JLAB Unique opportunity for nucleon structure physics • Can complete a substantial part of the EIC spin / GPD / TMD program, which is difficult to do with only a high-energy collider • High luminosity at medium energy (> 1033) • Symmetric kinematics improve resolution, acceptance, and particle identification ep →epπ+ 9 /10, 3/30 3/5 10/250 10/30 Cost-effective staging path for ELIC ELIC mEIClow-E IP • Required booster rings will serve as colliders • Flexible staging options with clear physics goals • Fast track possible (small / large rings) large e- ring small e- ring

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