Elic r&D and Realization Plan

• ELIC R&D

• and

• Realization Plan

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. Krafft, R. Li, L. Merminga, J. Musson, M. Poelker, R. Rimmer, 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-Troitsk, Russia

• V. Shemelin - Cornell University

Outline

• ELIC Design Specifications

• ELIC Overview and Design Parameters

• R&D Required for ELIC

• R&D relevant to ERL-based EIC designs

• EIC Accelerator Pre-R&D Plan

• ELIC Realization Plan

• Summary

ELIC Accelerator Design Specifications

• Center-of-mass energy between 20 GeV and 90 GeV

• with energy asymmetry of ~10, which yields

• Ee ~ 3 GeV on EA ~ 30 GeV up to Ee ~ 9 GeV on EA ~ 225 GeV

• Average Luminosity from 1033 to 1035 cm-2 sec-1 per Interaction Point

• Ion species:

• Polarized H, D, 3He, possibly Li
• Ions up to A = 208

• Longitudinal polarization of both beams in the interaction region (+Transverse polarization of ions +Spin-flip of both beams)

• all polarizations >70% desirable

• Positron Beam desirable

ELIC Layout

Design Features of ELIC

• Directly aimed at addressing the science program:

• “Figure-8” ion and lepton storage rings to ensure spin preservation and ease of spin manipulation. No spin sensitivity to energy for all species.

• Short ion bunches, low β*, and high rep rate (crab crossing) to reach unprecedented luminosity.

• Four interaction regions for high productivity.

• Physics experiments with polarized positron beam are possible. Possibilities for e-e-colliding beams.

• Present JLab DC polarized electron gun meets beam current requirements for filling the storage ring.

• The 12 GeV CEBAF accelerator can serve as an injector to the electron ring. RF power upgrade might be required later depending on the performance of ring.

• Collider operation appears compatible with simultaneous 12 GeV CEBAF operation for fixed target program.

Achieving the Luminosity of ELIC

ELIC e/p Parameters

ELIC e/p yielding L=1.6x1033 cm-2 s-1

ELIC Luminosity for Ions

Design Evolution & Recent Developments

• ELIC design evolves

• - in response to Science requirements (e.g. Rutgers mtg.)

• - towards a more robust and reliable concept which relies increasingly on

• proven state-of-the-art technology.

• Recent developments include:

• - Higher center-of-mass energy and inclusion of heavy ions, up to Pb

• - Concept of SRF ion linac for all ions (ANL design)

• - The use of stochastic cooling to accumulate intense ion beam

• - Reducing crab cavity voltage requirement by decreasing crossing angle from 100 mrad to 50 mrad and in combination with a new Lambertson-type final focus quadrupole

• - Longer [ 3 m] element-free region around the IP’s

SRF Ion Linac Concept

SRF Ion Linac Concept (cont’d)

A “Lambertson” Quad for Ion Final Focus

Accelerator R&D Required for ELIC

• To achieve luminosity at ~ 1033 cm-2 sec-1

• High energy electron cooling with circulator ring

• To achieve luminosity at ~ 1035 cm-2 sec-1

• Crab crossing
• Stability of intense ion beams
• Beam-beam interactions
• High RF frequency is included in EIC detector R&D

High Energy Electron Cooling

• Issue:

• Electron beam cooling required to suppress IBS, reduce beam emittances, provide short ion bunches.
• Very effective for heavy ions (higher cooling rate), more difficult for protons.
• Very ambitious project.

• State of art:

• Fermilab recently demonstrated relativistic electron cooling.

• Main Parameters:

• 4.34 MeV electron beam [x20 previous experience], 0.5 A DC

• Magnetic field in the cooling section - 100 G

• Feasibility of electron cooling with bunched beams remains to be demonstrated.

• R&D Plan

Electron Cooling for ELIC

• ERL-based cooler - Unique in its use of circulator cooler ring with ~100 revolutions to ease electron source and ERL requirements

• Dynamics must be simulated and understood

Crab Crossing

• ELIC crossing angle of 2 x 25 mrad requires total voltage of deflecting field on axis of:
• 2 MV for electrons – within state of art
• 40 MV for ions - Integrated magnetic field on axis of 300 G over 4 m

• Issues:

• Gradient limits of crab cavity technology need to be understood
• Phase and amplitude stability requirements
• Beam dynamics with crab crossing

Crab Crossing (cont’d)

• State-of-art:

• KEKB requirements:

• Crossing angle = 2 x 11 mrad

• Vkick=1.4 MV, Esp= 21 MV/m

Crab Crossing (cont’d)

• State-of-art (cont’d):

• JLab and Cornell estimates of KEKB crab cavity geometry yield:

• >300 G deflecting field on axis,

• 180 G for multicell cavity, higher (up to 2x) with shape optimization.

• R&D Plan:

• Explore designs with further reduced crossing angle (on-going!)
• Crab cavity shape optimizations and multicell cavity designs to increase gradient and packing factor, capable for high current operation.
• Understand phase and amplitude stability requirements
• Simulate beam dynamics with crab crossing

Stability of Intense Ion Beams

• Issue: Ion space charge at stacking in pre-booster

• R&D Plan:

• - Explore circular painting technique - similar to SNS – via numerical studies and experimental verification.

• An alternate approach:

• We are pursuing the use of stochastic cooling of coasting beam in the collider ring at injection energy as an alternate approach to overcome ion space charge limitations.

• – System design is required but parameters are within state of art

Beam-beam interactions

• Issues:

• Beam-beam interaction with multiple IP’s and crab crossing

• Beam-beam stability in linac-ring colliders

• R&D Plan:

• Analysis and simulations.

High current polarized electron source

• Issue:

• ERL-based designs require 100’s mA average electron current from a source at 80% polarization.

• State of art:

• Present state of art in polarized electron sources 0.3 mA average current, expected to reach 1 mA shortly, operating with current densities of ~ 50 mA/cm2.

• On-going and Planned R&D:

• Development of large cathode guns to provide path to electron currents of 10-100’s mA.

• Build and commission load locked gun (work in progress)
• Extend operating lifetime using large spot size (work in progress)
• Improve longitudinal emittance at high bunch charge
• Scale to voltage > 300kV, for high bunch charge operation
• Implement laser pulse shaping techniques for emittance preservation
• Boost fiber-based laser power > 20 W (factor of 10 improvement)
• Vacuum research for improved operating lifetime at high current

Multipass Energy Recovery

• Issue:

• eRHIC Energy Recovery Linac requires 10 passes – 5 up/5 down at 260 mA/pass

• State of art:

• SRF ERL: 2x10 mA at the JLab FEL

• R&D Plan:

• Explore/Demonstrate feasibility, operational
• robustness of multipass energy recovery at GeV level in
• CEBAF.

EIC Accelerator Pre-R&D Plan

• High current polarized electron source

• - Total labor: 15 FTE – years

• - Duration: 5 years

• - M&S: $800K

• [5 FTEs & $200 K consist on-going effort]

• Electron cooling simulations with circulator ring and kicker development

• - Total labor: 5.5 FTE – years

• - Duration: 5 years

• - M&S: $50K for kicker

• Prototype two 1500 MHz crab cavities and controls

• - Total Labor: 2 FTE – years

• - Duration: 2 years

• - M&S: $450K

EIC Accelerator Pre-R&D Plan (cont’d)

• Intense ion beam stability – simulations and experiment

• - Total labor: 2 FTE – years
• - Duration: 2 years
• - M&S: $500K for diagnostics development

• Beam-beam simulations for linac-ring and ring-ring options

• - Total labor: 3 FTE-years

• - Duration: 3 years

• Multipass energy recovery experiment at CEBAF

• - Total labor: 1 FTE-year

• - M&S: $600K

Updated ELIC ZDR

ELIC Performance Summary

ELIC Realization Plan

Summary

• ELIC, JLab’s EIC design, is based on a ring-ring configuration, uses CEBAF as a full energy electron injector, and can be integrated with the 12 GeV fixed target program for physics.

• ELIC has recently been extended to include heavy ions, and center-of-mass energy between 20 and 90 GeV and promises luminosity up to nearly 1035 cm-2 sec-1 for electron-proton collisions, and at or above 1035 cm-2 sec-1 (per nucleon) for electron-ion collisions.

• ELIC can reach luminosity at Lp = 1.6 x 1033 cm-2s-1 with state-of-the-art technology, except for electron cooling.

• Luminosity at Lp~1035 cm-2s-1 requires additional accelerator R&D on crab cavities and design.

• A pre-R&D plan to address EIC accelerator physics and technology issues has been developed.