Toward a Test Facility for an ERL Circulator

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 Diagnostic element Fast kicker Cooling channel solenoid lattice Fast kicker

Scaling Down Parameters: How Much? For a convincing demonstration • • • Beam current in circulator ring: 1. 5 A 15 m. A ? Charge per bunch: 2 n. C 0. 4 n. C ? ERL beam current: 15 m. A ? Fast kicker: 1. 33 ns (750 MHz) 20 ns (50 MHz) ? Turns of circulation: 10 to 30 turns ?

Beam Parameters MEIC FEL Test Facility 88 – 165 11 – 54 Energy range Me. V 11 – 54 Beam current in circulator cooler ring m. A 1500 150 Bunch repetition in circulator cooler ring MHz 748. 5 50 Bunch spacing in circulator cooler ring m 0. 4 6 Circumference of circulator cooler ring m 120 90 300 15 Bunches in circulator cooler ring Charge per bunch n. C 2 0. 135 0. 4 Electrons/bunch 1010 1. 25 0. 084 0. 25 bunch revolutions in circulator cooler ring 100 to 300 10 to 30 Current in ERL m. A 15 to 5 9. 1 15 Bunch repetition in ERL MHz 2. 5 to 7. 5 0. 58 – 74. 85 5 to 1. 67 RMS Bunch length cm 1 -3 0. 005 (160 fs) 1 Energy spread 10 -4 1 -3 40 10 Beam radius in solenoid mm ~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 Large booster to collider ring Large booster (warm) transfer beamline (up to 20 Ge. V/c) Pre-booster (up to 3 Ge. V) Ion source SRF linac Ion collider ring (cold) (up to 100 Ge. V/c) Three Figure 8 rings stacked vertically Medium energy IP with horizontal crab crossing Electron ring (3 to 11 Ge. V) Injector 12 Ge. V CEBAF Future energy/luminosity upgrade possible (250 Ge. V proton, 100 Ge. V/u ion, 1035 cm-2 s-1)

Optimized Location of Cooling Channel 20 m id no e l o ) m (15 S injector SRF Short circulating beam-line Center of Figure-8 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 dumper

Cooling in Ion Collider Ring • 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 Initial after boost Colliding Mode Ge. V/Me. V 15 / 8. 15 60 / 32. 67 A 0. 5 / 1. 5 Particles/Bunch 1010 0. 416 / 2 Bunch length mm (coasted) 10 / 20~30 Momentum spread 10 -4 10 / 2 5/2 3/2 Hori. & vert. emittance, norm. µm 4/4 Energy proton/electron beam current Laslett’s tune shift (proton) 0. 002 In collision mode of MEIC, 60 Ge. V proton formula Long. Hori. IBS Piwinski s 66 86 IBS Martini (Beta. Cool) s 50 100 Cooling Derbenev s ~24 0. 35 / 0. 07 0. 005 0. 06 Beta. Cool Simulations Vert. 1923 emittance IBS growth time

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

Energy Me. V 80 -200 Charge/bunch p. C 135 Average current m. A 10 Peak current A 270 Beam power MW 2 % 0. 5 µm-rad <30 Energy spread Normalized emittance