Status of the MEIC Machine Design Andrew Hutton Associate Director, Accelerators For the JLab EIC Study Group

Outline Introduction and the big picture Machine design status Critical R&D and path forward Summary

Electron Ion Colliders EnergiessDesign Luminosity to 11 x Close to Future Up to 11 x 250 (20? x 250) (20000?) Close to Staged Up to 5 x Close to to 20 x 325 (30 x 325) (39000) Close to to 3 x 15180Few x to 150 x Close to Design Goals for Colliders Under Consideration World-wide Present focus of interest (in the US) are the (M)EIC and Staged MeRHIC versions, with s up to ~3000 and 5000, resp.

ELIC: JLab’s Future Over the last decade, JLab has been developing an electron-ion collider (ELIC) based on the CEBAF recirculating SRF linac The future nuclear science program drives ELIC design, focusing on: High luminosity per detector (up to cm -2 s -1 ) in multiple detectors High polarization (>80%) for both electrons & light ions We have made significant progress on design optimization The primary focus is a Medium-energy Electron Ion Collider ( ) as the best compromise between science, technology and project cost Energy range is up to 60 GeV ions and 11 GeV electrons Well-defined upgrade capability to higher energies is maintained (ELIC) High luminosity & high polarization continue to be the design drivers

EICAC (November 2010) Report From report by Allen Caldwell to CU Collaboration Meeting

Comments from EICAC Report “The highest priority on the facility side is to develop the JLAB design to a stage similar to where the BNL design is at present” This is our highest priority and we are making progress “The JLab... concept is at a less mature state... It is difficult to assess the credibility of predicted performance, due to many unresolved but very challenging accelerator aspects” We have been addressing the accelerator aspects and integrating more closely with the detector design “On the other hand, luminosity performance is predicted to be very high” More space for the detector means lower luminosity But more physics!

Comments from EICAC Report “design should be able to be credibly costed, and should identify a comprehensive table of performances including center of mass energies and luminosities that can be achieved” We are aiming for performance estimates by Q2FY11 and a cost estimate by Q1FY12 “the highest R&D priority for JLAB should be the design, even if that activity is not strictly considered R&D, and resources need to be made available to do the work” Resources have been made available Thanks to DOE-NP for additional funding This talk presents the present state of the design

8 EIC Realization Imagined Activity Name Gev Upgrade FRIB EIC Physics Case NSAC LRP CD0 Machine Design/R&D CD1/D’nselect CD2/CD3 Construction

Outline Introduction and the big picture Machine design status Critical R&D and path forward Summary

Highlights of recent Design Activities Continuing design optimization Optimizing main machine parameters to match the science program Now aim for high luminosity AND full detector acceptance Simplified design and reduced R&D requirements Focused on detailed design of major components Completed baseline design of the two collider rings Completed first design of the ion linac and Figure-8 pre-booster Completed beam polarization scheme with universal electron spin rotators Updated IR optics design Selected bunch collision frequency of 750 MHz Made considerable progress on beam synchronization Continuing work on critical R&D Beam-beam simulations Nonlinear beam dynamics and instabilities Chromatic corrections

Short-Term Strategy MEIC accelerator team is developing an integrated MEIC design MEIC accelerator team will create a complete design with sufficient technical detail to evaluate performance Design basis will be reviewed every ~ 6 months and specifications updated to reflect developments in: Nuclear science program Accelerator R&D The current design is conservative, restricting the design parameters to close to the present state of the art Maximum peak field of ion superconducting dipole is 6 T Maximum synchrotron radiation power density is 20 kW/m Maximum beta at final focus quad is 2.5 km (field gradient <200 T/m)

Short-Term Strategy Present design (assuming 6T magnets) has the following features: Center-of-mass energy up to 51 GeV: GeV electron, 20 – 60 GeV protons, GeV/u ions Upgrade option to high energy 3 interaction regions, 2 available for medium energy collisions Luminosity up to ~10 34 cm -2 s -1 per collision point Full acceptance for at least one medium-energy detector Large acceptance with a higher luminosity for other detector High polarization for both electron and light ion beams

MEIC : Medium Energy EIC Three compact rings: 3 to 11 GeV electron Up to 12 GeV/c proton (warm) Up to 60 GeV/c proton (cold) low-energy IP polarimetry medium-energy IPs

Detailed Layout cold ring warm ring

ELIC: High Energy & Staging StageMax. Energy (GeV/c) Ring Size (m) Ring TypeIP # pepe Medium ColdWarm3 High ColdWarm4 Serves as a large booster to the full energy collider ring

Ring-Ring Design Features Very high luminosity Polarized electrons and polarized light ions (longitudinal and transverse at IP) Up to 3 interaction regions (detectors) for high science productivity Figure-8 ion and lepton storage rings Ensures spin preservation and ease of spin manipulation Avoids energy-dependent spin sensitivity for all species Only practical way to accommodate polarized deuterons 12 GeV CEBAF meets electron injector requirements for MEIC Simultaneous operation of collider & CEBAF fixed target program possible Experiments with polarized positrons would be possible

Luminosity Approach High luminosity at B factories comes from: Very small β* (~6 mm) to reach very small spot sizes at collision points Very short bunch length (σ z ~ β*) to avoid hour-glass effect Very small bunch charge which makes very short bunch possible High bunch repetition rate restores high average current and luminosity Synchrotron radiation damping  KEK-B and PEPII already over 2  cm -2 s -1 KEK BMEIC Repetition rateMHz Particles per bunch10 3.3/ /2.5 Beam currentA1.2/1.80.5/3 Bunch lengthcm0.61/0.75 Horizontal & vertical β*cm56/0.5610/2 (4/0.8) Luminosity per IP, cm -2 s (14.2) These concepts are the basis for the MEIC design

solenoid electron FFQs 50 mrad 0 mrad ion dipole w/ detectors ions electrons IP ion FFQs 2+3 m 2 m Detect particles with angles below 0.5 o beyond ion FFQs and in arcs. detectors Central detector Detect particles with angles down to 0.5 o before ion FFQs. Need 1-2 Tm dipole. EM Calorimeter Hadron Calorimeter Muon Detector EM Calorimeter Solenoid yoke + Muon Detector TOF HTCC RICH RICH or DIRC/LTCC Tracking 2m 3m 2m 4-5m Solenoid yoke + Hadronic Calorimeter Very-forward detector Large dipole 20 meter from IP (to correct the 50 mr ion horizontal crossing angle) allows for very-small angle detection (<0.3 o ) High Acceptance Detector Pawel Nadel-Turonski & Rolf Ent 7 meters

MEIC Design Parameters For a Large-Acceptance Detector Full Acceptance DetectorProtonElectron Beam energyGeV605 Collision frequencyGHz0.75 Particles per bunch Beam CurrentA0.53 Polarization%  70~ 80 Energy spread10 -4 ~ 37.1 RMS bunch lengthcm107.5 Horizontal emittance, normalizedµm rad Vertical emittance, normalizedµm rad Horizontal β*cm10 Vertical β*cm22 Vertical beam-beam tune shift Laslett tune shift0.07Very small Distance from IP to 1 st FF quadm 73.5 Luminosity per IP, cm -2 s

High-Luminosity DetectorProtonElectron Beam energyGeV605 Collision frequencyGHz0.75 Particles per bunch Beam currentA0.53 Polarization%> 70~ 80 Energy spread10 -4 ~ 37.1 RMS bunch lengthmm107.5 Horizontal emittance, normalized µm rad Vertical emittance, normalizedµm rad Horizontal β*cm44 Vertical β*cm0.8 Vertical beam-beam tune shift Laslett tune shift0.07Very small Distance from IP to 1 st FF quadm Luminosity per IP, cm -2 s

Proton Energy Electron Energy sCM Energy Luminosity (L=7m, β*=2cm) Luminosity (L=4.5m, β*=8mm) GeV GeV 2 GeV10 33 cm -2 s Proton Energy Electron Energy Ring Circumference Luminosity (L=7m, β*=2cm) Luminosity (L=4.5m, β*=8mm) GeV m10 33 cm -2 s / / The second option is using 1 km medium-energy ion ring for higher proton beam current at 30 GeV protons for lowering the space charge tune-shift ELIC Luminosity: 2.5 km Ring, 8 Tesla Full acceptanceHigh luminosity

Figure-8 Ion Rings Figure-8 is optimum for polarized ion beams Simple solution to preserve full ion polarization by avoiding spin resonances during acceleration Energy independence of spin tune g-2 is small for deuterons; a figure-8 ring is the only practical way to accelerate deuterons and to arrange for longitudinal spin polarization at interaction point Transverse polarization for deuterons looks feasible

Siberian snake Ion Ring Electron Ring Spin rotators RF IP Potential IP Figure-8 Collider Rings

MEIC Design Details Our present design is mature, having addressed -- in various degrees of detail -- the following important aspects of MEIC: Beam synchronization Ion polarization (RHIC-type Siberian snakes) Electron polarization Universal spin rotator Electron beam time structure & RF system Forming the high-intensity ion beam: SRF linac, pre-booster Synchrotron rad. background Beam-beam simulations Beam stability Detector design IR design and optics Electron and ion ring optics

Outline Introduction and the big picture Machine design status Critical R&D and path forward Summary

MEIC Critical Accelerator R&D Level of R&DLow-to-Medium Energy (12x3 GeV/c) & (60x5 GeV/c) High Energy (up to 250x10 GeV) Challenging Semi Challenging Electron cooling Traveling focusing (for ion energies ~12 GeV) Electron cooling IR design/chromaticity LikelyIR design/chromaticity Crab crossing/crab cavity High intensity low energy ion beam Crab crossing/crab cavity High intensity low energy ion beam Know-howSpin tracking Beam-Beam Spin tracking Beam-beam We have identified the following critical R&D issues for MEIC: Interaction region design and limits with chromatic compensation Electron cooling Crab crossing and crab cavity Forming high-intensity low-energy ion beam Beam-beam effect Depolarization (including beam-beam) and spin tracking Traveling focusing for very low energy ion beam

Design goal Up to 33 MeV electron energy Up to 3 A CW unpolarized beam (~nC bunch 499 MHz) Up to 100 MW beam power! Solution: ERL Circulator Cooler ERL provides high average current CW beam with minimum RF power Circulator ring for reducing average current from source and in ERL (# of circulating turns reduces ERL current by same factor) Technologies High intensity electron source/injector Energy Recovery Linac (ERL) Fast kicker Electron circulator ring Electron Cooling: ERL Circulator Cooler Derbenev & Zhang, COOL 2009

Ongoing Accelerator R&D We are concentrating R&D efforts on the most critical tasks: Focal Point 1: Forming high-intensity short-bunch ion beams & cooling Sub tasks:Complete design of the RF linac and pre-booster Ion bunch dynamics and space charge effects (simulations) Led by Peter Ostroumov (ANL) Focal Point 2: Electron cooling of medium-energy ion beam Sub tasks:Electron cooling dynamics (simulations) Complete design of the ERL-based circulator cooler Dynamics of cooling electron bunch in ERL circulator ring Focal Point 3: Beam-beam interaction Sub tasks: Include crab crossing and/or space charge Include multiple bunches and interaction points

Collaborations Established IR/detector designM. Sullivan (SLAC) MEIC ion complex front end P. Ostroumov (ANL) (From source up to injection into collider ring) Ion sourceV. Dudnikov, R. Johnson (Muons, Inc) V. Danilov (ORNL) SRF LinacP. Ostroumov (ANL), B. Erdelyi (NIU) Chromatic compensationA. Netepenko (Fermilab) Beam-beam simulation J. Qiang (LBNL) Electron cooling simulationD. Bruhwiler (Tech X) PolarizationA. Kondratenko (Novosibirsk) Electron spin trackingD. Barber (DESY)

EIC Study Group A. Accardi, A. Afanasev, A. Bogacz, J. Benesch, P. Brindza, A. Bruell, L. Cardman, Y. Chao, S. Chattopadhyay, J.P. Chen, E. Chudakov, P. Degtiarenko, J. Delayen, Ya. Derbenev, R. Ent, P. Evtushenko, A. Freyberger, D. Gaskell, J. Grames, V. Guzey, L. Harwood, T. Horn, A. Hutton, C. Hyde, N. Kalantarians, R. Kazimi, F. Klein, G. A. Krafft, R. Li, F. Marhauser, L. Merminga, V. Morozov, J. Musson, P. Nadel-Turonski, F. Pilat, M. Poelker, A. Prokudin, R. Rimmer, H. Sayed, M. Spata, A. Thomas, M. Tiefenback, B. Terzić, H. Wang, C. Weiss, B. Wojtsekhowski, B. Yunn, Y. Zhang - Jefferson Laboratory staff and users W. Fischer, C. Montag - Brookhaven National Laboratory D. Barber - DESY V. Danilov - Oak Ridge National Laboratory V. Dudnikov - Brookhaven Technology Group P. Ostroumov - Argonne National Laboratory B. Erdelyi - Northern Illinois University and Argonne National Laboratory V. Derenchuk - Indiana University Cyclotron Facility A. Belov - Institute of Nuclear Research, Moscow, Russia R. Johnson - Muons Inc. A. Kondratenko - Novosibirsk

Outline Introduction and the big picture Machine design status Critical R&D and path forward Summary

MEIC is optimized to collide a wide variety of polarized light ions and unpolarized heavy ions with polarized electrons (or positrons) MEIC covers an energy range matched to the science program proposed by the JLab nuclear physics community (~ GeV 2 ) with luminosity up to 1.4x10 34 cm -2 s -1 An upgrade path to higher energies (250x10 GeV 2 ) is being maintained, which should provide luminosity of close to cm -2 s -1 The design is based on a Figure-8 ring for optimum polarization, and an ion beam with high repetition rate, small emittance and short bunch length Electron cooling is absolutely essential for cooling & bunching the ion beam We have identified the critical accelerator R&D topics for MEIC, and are presently working on them Our present MEIC design is mature and flexible, able to accommodate revisions in design specifications and advances in accelerator R&D We are aiming for performance estimates by Q2FY11 and a cost estimate by Q1FY12