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