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Overview of MEIC Electron Collider Ring

Overview of MEIC Electron Collider Ring. Yuhong Zhang. Electron Collider Ring Design Goals. A storage ring is capable of providing the following features Overall Electron energy 3 to 11 GeV

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Overview of MEIC Electron Collider Ring

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  1. Overview of MEIC Electron Collider Ring Yuhong Zhang

  2. Electron Collider Ring Design Goals • A storage ring is capable of providing the following features Overall • Electron energy 3 to 11 GeV • Accepting and accumulating full energy injected electron beam from CEBAF (No requirement of further upgrade of 12 GeV CEBAF) • Option of “top-off” current operation Geometric • Be large enough to accommodate 3 IPs (detectors) and all necessary components including RF system, spin manipulating, polarimetry, injection/ejection • Sharing a same (figure-8 shape) footprint with the ion collider ring of 60 (30) GeV/u protons (ions) Beam qualities • Be able to store a high average current (up to 3 A) and high bunch repetition rate (up to 1.5 GHz) CW electron beam • Be able to maintain a reasonable long beam life time • Small transverse emittance and short bunch length

  3. Electron Collider Ring Design Goals (cont.) Polarization • high (>80%) polarization over a reasonable long period of time (>10 min) • Longitudinal spin direction at all interaction points • Capability of spin flipping beam • Be able to accommodate and self-polarizing positron beam Technical and cost-wise • Limiting synchrotron radiation power density below 20 kW/m, and also minimizing total radiation loss for requiring less RF power • Constructed with warm magnets Stability or operability • Achieving high stability & operability through modulation optics design • Consideration of beam control and diagnostics • Large momentum acceptance and dynamical aperture

  4. Figure-8 Electron Collider Ring Footprint Ions from big booster Spin Rotator (8.8°/4.4°, 50 m) 1/4 Electron Arc (106.8°, 117.5 m) IR(60 m) IR(60 m) Spin Rotator (8.8°/4.4°, 50 m) Experimental Hall (radius 15 m) RF (20 m) Figure-8 crossing angle: 2x30° Spin Rotator (8.8°/4.4°, 50 m) Compton polarimeter (28 m) 1/4 Electron Arc (106.8°, 117.5 m) 3rd IR (60 m) Spin Rotator (8.8°/4.4°, 50 m) Injection from CEBAF

  5. ComprehensiveParameter Table

  6. Figure-8 Electron Ring Design Parameters

  7. Formation of Stored Beam in the Collider Ring From CEBAF SRF Linac 0.67 ns (20 cm) 1.5 GHz < 3.3 ps (1 mm) 0.2 pC Microscopic bunch duty factor 5x10-3 10-turn injection 33.3μs(2 pC) Stored beam in collider ring 40 ms (~5 damping times) 25 Hz Macroscopic bunch duty factor 8.5x10-3 40 s • Full energy injection from CEBAF • 10-turn injection followed by phase space damping

  8. More Topics • Electron collider ring optics design Alex Bogacz • RF systems for electron collider ring Haipeng Wang • Electron beam stability ByungYunn • Electron beam polarization VasiliyMorozov

  9. Backup Slides

  10. Compton Polarimeter Layout chicane separates polarimetry from accelerator scattered electronmomentum analyzed in dipole magnet measured with Si or diamond strip detector pair spectrometer (counting mode) e+e– pair production in variable converter dipole magnet separates/analyzes e+ e– sampling calorimeter (integrating mode)count rate independent Insensitive to calorimeter response • Geometry: • Total dipole chicane length = 28 m • Dipoles = 3 m long, 2T • Electron beam deflection between dipoles 1-2 = 94 cm • scattered electron 6.7 cm (3.3 cm) from beam at endpoint at asymmetry zero crossing (green laser) • Photon detector 54 m from laser-electron interaction point David Gaskell

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