Toward a Test Facility for an ERL Circulator Ring Based e-Cooler MEIC Electron Cooler Test Facility Planning Retreat January 31, 2012

Charge of the Retreat Examine the feasibility of utilizing JLab FEL Facility for a test bad of ERL-Circulator-Ring e-cooler Determine the goals of this test facility Formulate plausible test scenarios Determine the required pre-R&D Draft a plan for this test facility

What We Want to Test/Demonstrate/Study? Production of high current/bunch intensity, high repetition beam Energy recovery of a high current electron beam after its extended stay in a circulator ring; Operation of a circulator ring including injection and ejection of the beam bunches, and advanced filling schemes; Quality of the beam bunch during a large number of circulations in a ring Collective beam effects (space charge, CSR)

e-Cooler Test Facility lattice Diagnostic element Fast kicker Cooling channel solenoid

Scaling Down Parameters: How Much? For a convincing demonstration Beam current in circulator ring: 1.5 A  15 mA ? Charge per bunch: 2 nC  0.4 nC ? ERL beam current: 15 mA  15 mA ? Fast kicker: 1.33 ns (750 MHz)  20 ns (50 MHz) ? Turns of circulation: 10 to 30 turns ?

Beam Parameters MEICFELTest Facility Energy rangeMeV11 – 5488 – – 54 Beam current in circulator cooler ringmA Bunch repetition in circulator cooler ringMHz Bunch spacing in circulator cooler ringm0.46 Circumference of circulator cooler ringm12090 Bunches in circulator cooler ring30015 Charge per bunchnC Electrons/bunch bunch revolutions in circulator cooler ring100 to to 30 Current in ERLmA15 to Bunch repetition in ERLMHz2.5 to – to 1.67 RMS Bunch lengthcm (160 fs)1 Energy spread Beam radius in solenoidmm~1

Test Scenarios Test high bunch charge injector (DC gun? SRF gun?) Test high current ERL without/with circulator ring? Test kicker/filling scheme of a circulator ring? Test beam stability/collective effects in circulator ring?

Additional Hardware & pre-R&D Magnetic lattice for the circulator ring Fast kickers Beam diagnostic instruments High bunch intensity electron source ERL for high bunch intensity beam (?) (not very fast) kicker Design and simulation

Timeline Total time: 2 years (?) Design/simulation/pre-R&D: 1.5 year commissioning: 2 months Running experiments: 4 months

High Brightness SRF Photo Injector Gun

A Polarized Ring-Ring MEIC at JLab Pre-booster (up to 3 GeV) Ion source Three Figure-8 rings stacked vertically Large booster to collider ring transfer beamline Medium energy IP with horizontal crab crossing Electron ring (3 to 11 GeV) Injector 12 GeV CEBAF SRF linac Large booster (warm) (up to 20 GeV/c) Ion collider ring (cold) (up to 100 GeV/c) Future energy/luminosity upgrade possible (250 GeV proton, 100 GeV/u ion, cm -2 s -1 )

Optimized Location of Cooling Channel 20 m Solenoid (15 m) SRF injector dumper Eliminating a long circulating beam-line could cut cooling time by half, or reduce the cooling electron current by half, or reduce the number of circulating by half Short circulating beam-line Center of Figure-8

Cooling in Ion Collider Ring Initialafter boostColliding Mode EnergyGeV/MeV15 / / proton/electron beam currentA0.5 / 1.5 Particles/Bunch / 2 Bunch lengthmm(coasted)10 / 20~30 Momentum spread / 25 / 23 / 2 Hori. & vert. emittance, norm.µm4 / / 0.07 Laslett’s tune shift (proton) Initial cooling after ions injected into the collider ring for reduction of longitudinal emittance before acceleration After boost & re-bunching, cooling for reaching design values of beam parameters Continuous cooling during collision for suppressing IBS, maintaining luminosity lifetime formulaLong.Hori.Vert. IBSPiwinskis6686 IBSMartini (BetaCool) s CoolingDerbenevs~24 IBS growth time emittance BetaCool Simulations In collision mode of MEIC, 60 GeV proton

Monitoring Bunch Evolution in Circulator Ring lattice Diagnostic element Fast kicker Cooling channel solenoid Kicking bunches out after n-th turn Diagnostic element

EnergyMeV Charge/bunchpC135 Average currentmA10 Peak currentA270 Beam powerMW2 Energy spread%0.5 Normalized emittanceµm-rad<30