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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
latticeDiagnostic element
Fast kickerFast 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 ParametersMEIC FEL Test Facility
Energy range MeV 11 – 54 88 – 165 11 – 54
Beam current in circulator cooler ring mA 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
Bunches in circulator cooler ring 300 15
Charge per bunch nC 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 mA 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 JLabPre-booster
(up to 3 GeV) Ion source
Three Figure-8rings stacked
vertically
Large booster to collider ring transfer
beamline
Medium energy IP withhorizontal 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, 1035 cm-2s-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
Initial after boost Colliding Mode
Energy GeV/MeV 15 / 8.15 60 / 32.67 60 / 32.67
proton/electron beam current A 0.5 / 1.5 0.5 / 1.5 0.5 / 1.5
Particles/Bunch 1010 0.416 / 2 0.416 / 2 0.416 / 2
Bunch length mm (coasted) 10 / 20~30 10 / 20~30
Momentum spread 10-4 10 / 2 5 / 2 3 / 2
Hori. & vert. emittance, norm. µm 4 / 4 0.35 / 0.07
Laslett’s tune shift (proton) 0.002 0.005 0.06
• 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
formula Long. Hori. Vert.
IBS Piwinski s 66 86
IBS Martini(BetaCool)
s 50 100 1923
Cooling Derbenev s ~24 IBS growth time
emittance
BetaCool SimulationsIn collision mode of MEIC, 60 GeV proton
Monitoring Bunch Evolution in Circulator Ring
lattice
Diagnostic element
Fast kicker
Fast kicker
Cooling channel solenoid
Kicking bunches out after n-th turn
Diagnostic element
Energy MeV 80-200
Charge/bunch pC 135
Average current mA 10
Peak current A 270
Beam power MW 2
Energy spread % 0.5
Normalized emittance
µm-rad <30