JLEIC Electron Collider Ring Design and Polarization Fanglei

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JLEIC Electron Collider Ring Design and Polarization Fanglei Lin JLEIC Collaboration Meeting Fall 2016

JLEIC Electron Collider Ring Design and Polarization Fanglei Lin JLEIC Collaboration Meeting Fall 2016 October 5 -7, 2016

Outline Electron collider design goal Electron collider ring baseline design optimization Electron collider ring

Outline Electron collider design goal Electron collider ring baseline design optimization Electron collider ring new design options Electron polarization design and simulation JLEIC Collaboration Meeting Fall 2016 2

Electron Collider Design Goal Electron beam parameters – 3 -10 Ge. V energy –

Electron Collider Design Goal Electron beam parameters – 3 -10 Ge. V energy – 3 A beam current up to 6 -7 Ge. V – ~1 cm bunch length – small emittance – < 10 MW total synchrotron radiation power – 70% or above polarization Longitudinal polarization at collision points with a long polarization lifetime Forward electron detection Up to two detectors Provision for correction of beam nonlinearity JLEIC Collaboration Meeting Fall 2016 3

CEBAF - Full Energy Injector CEBAF fixed target program – 5 -pass recirculating SRF

CEBAF - Full Energy Injector CEBAF fixed target program – 5 -pass recirculating SRF linac – Exciting science program beyond 2025 – Can be operated concurrently with the JLEIC e- collider ring Wien Filters and solenoids provide vertically polarized electron beam to the JLEIC. CEBAF will provide for JLEIC See Jiquan Guo’s talk: Electron injection scheme from CEBAF to the collide ring JLEIC Collaboration Meeting Fall 2016 4 – – Up to 12 Ge. V electron beam High repetition rate (up to 1497 MHz) High polarization (>85%) Good beam quality

Transfer Line Design requirements – No significant emittance growth – Room for matching and

Transfer Line Design requirements – No significant emittance growth – Room for matching and diagnostic region, compression chicane if needed, a spreader step if needed – PEP-II magnets (cost) Realization – Utilizes PEP-II LER 156 dipoles and 68 quadrupoles – Dipoles are grouped six as one in FODO cells with 120 phase advance – Total length of transfer line is 333. 25 meters Injection scheme --- PEP-II-like design – Dispersion free injection insertion – Septum + DC + RF kickers – Vertical injection avoiding parasitic interaction with circulating ion beams in the horizontal plane, simplifying the problem of masking the detector from particle loss during injection Courtesy of Y. Roblin JLEIC Collaboration Meeting Fall 2016 5

S pi 6 310 m n r ota t or R= 15 5 m

S pi 6 310 m n r ota t or R= 15 5 m T St une r a ig trom h t FO bo DO ne s & JLEIC Collaboration Meeting Fall 2016 in Sp CC or tat ro B e- 81. 7 Arc, 261. 7 Future 2 nd IP RF RF in Sp S p in r to ta ro ro t a tor IP Forward e- detection 784 m Circumference of 2154. 28 m = 2 x 754. 84 m arcs + 2 x 322. 3 straights Figure-8 crossing angle 81. 7

Normal Arc FODO Cell Complete FODO (Each arc has 34 such normal FODO cell)

Normal Arc FODO Cell Complete FODO (Each arc has 34 such normal FODO cell) – Length 15. 2 m (arc bending radius 155 m) – 2 dipoles + 2 quadrupoles + 2 sextupoles – 108 /108 x/y betatron phase advance Dipoles – – Magnetic/physical length 5. 4/5. 68 m Bending angle 48. 9 mrad (2. 8 ), bending radius 110. 5 m 0. 3 T @ 10 Ge. V Sagitta 3. 3 cm Quadrupoles – Magnetic/physical length 0. 56/0. 62 m – -11. 6 and 12. 8 T/m field gradients @ 10 Ge. V – 0. 58 and 0. 64 T @ 50 mm radius Sextupoles – Magnetic/physical length 0. 25/0. 31 m – -176 and 88 T/m 2 field strengths @ 10 Ge. V for chromaticity compensation only in two arcs (strengths will be determined in DA simulations) BPMs and Correctors – Physical length 0. 05 and 0. 3 m JLEIC Collaboration Meeting Fall 2016 7

Baseline Optics Parameters Electron beam momentum Ge. V/c 10 Circumference m 2154. 28 Arc’s

Baseline Optics Parameters Electron beam momentum Ge. V/c 10 Circumference m 2154. 28 Arc’s net bend deg 261. 7 Straights’ crossing angle deg 81. 7 Arc/straight length m 754. 84/322. 3 Beta stars at IP *x, y cm 10/2 Detector space m -3 / 3. 2 Maximum horizontal / vertical functions x, y m 949/692 Maximum horizontal / vertical dispersion Dx, y m 1. 9 / 0 Horizontal / vertical betatron tunes x, y 45. (89) / 43. (61) Horizontal / vertical chromaticities x, y -149 / -123 Momentum compaction factor 2. 2 10 -3 Transition energy tr 21. 6 Hor. /ver. emittance x, y (normalized/un-normalized) JLEIC Collaboration Meeting Fall 2016 8 µm rad 1093 / 219 (0. 056/0. 011)

Synchrotron Radiation Parameters Beam current up to 3 A at 6. 95 Ge. V

Synchrotron Radiation Parameters Beam current up to 3 A at 6. 95 Ge. V Synchrotron radiation power is under 10 MW at high energies Beam energy Ge. V 3 5 6. 95 9. 3 10 Beam current A 1. 4 3 3 0. 95 0. 71 MW 0. 16 2. 65 10 10 10 Linear SR power density (arcs) k. W/m 0. 16 2. 63 9. 9 Energy loss per turn Me. V 0. 11 0. 88 3. 3 10. 6 14. 1 Energy spread 10 -3 0. 27 0. 46 0. 66 0. 82 0. 91 Transverse damping time ms 376 81 26 14 10 Longitudinal damping time ms 188 41 13 7 5 Normalized Emittance um 30 137 425 797 1093 Total SR power JLEIC Collaboration Meeting Fall 2016 9

Summary of Baseline Design 2. 2 km electron collider ring was design reuse of

Summary of Baseline Design 2. 2 km electron collider ring was design reuse of PEP-II HER magnets mostly Two arcs are composed of 15. 2 m long FODO cells, dispersion suppression sections and spin rotators – FODO cell and dispersion suppression (PEP-II magnets) • dipole 5. 4 m, bending angle 2. 8 , bending radius 110. 5 m, sagitta 3. 3 cm, 0. 3 T @ 10 Ge. V, can reach 0. 362 T @ 12 Ge. V with only ~0. 2% saturation • Quadrupole 0. 56 m, field gradient <13 T/m @ 10 Ge. V with saturation <0. 4%, gradient ~14 -15 T/m @ 12 Ge. V with saturation up to ~6% • 108 /108 x/y betatron phase advance in FODO cell – Spin rotators have new dipoles, solenoids and quads (~25 T/m @ 10 Ge. V). Straight FODO cells, tune trombone and matching sections use PEP-II 0. 73 m-long PEP-II quads and some new quads Chromaticity compensation block, RF sections and detector region use new dipoles and quads. Arcs contribute ~90% emittance and ~30 -40% chromaticities. JLEIC Collaboration Meeting Fall 2016 10 10

Approaches of Reducing Emittance All following options have been investigated – Optimizing of sections,

Approaches of Reducing Emittance All following options have been investigated – Optimizing of sections, such as matching section, spin rotator, etc. , to reduce the emittance contribution (30%) • Pros: do not change the optics of the rest of the ring, except some particular sections • Cons: ~110 m additional space and 16 quads are needed – Adding (dipole) damping wigglers (50% @ 5 Ge. V) • Pros: do not change the baseline design, fast damping • Cons: need wigglers, more radiation power, larger energy spread (a factor of 2), high RF peak power if keep the same bunch length, not suitable at higher energies, affect the polarization lifetime – Offsetting the beam in quads (~ 7 to 8 mm) in arcs (48%) • Pros: do not change the baseline design • Cons: larger energy spread (a factor of 2), longer (maybe) bunch length, have to center the sextupoles – New magnets (instead of PEP-II magnets) ring but still FODO cell arcs (50%) • Pros: small dipole bending angle results in small emittance and no sagitta issue • Cons: all new magnets, large chromaticities, strong sextupoles for chromaticity compensation due to small dispersion – Different types of arc cell, such as DBA, TME (> 50%) Need combine nonlinear dynamic studies • Pros: much smaller emittance comparing to the FODO cell • Cons: possible more quads, stronger quads, possible larger ring, large chromaticities, efficient chromaticity compensation scheme JLEIC Collaboration Meeting Fall 2016 11 11

Optimized Optics of Matching Section Baseline design Optimized design: “missing magnet”-like dispersion suppressor +

Optimized Optics of Matching Section Baseline design Optimized design: “missing magnet”-like dispersion suppressor + beta function matching – Matching section dipole bending angles – Regular arc FODO cell: each dipole bending angle , phase advance – Matching section: each dipole bending angle Regular arc FODO cell Matching section – Regular arc bending angle – 8 extra dipoles (4 FODO cells) are needed Regular arc FODO cell Spin rotator Baseline JLEIC Collaboration Meeting Fall 2016 Spin rotator New 12 12

Optimized Optics of Spin Rotator Optimized design Baseline design – Lattice in the two

Optimized Optics of Spin Rotator Optimized design Baseline design – Lattice in the two dipole sets is optimized to a DBA-like optics, which has a smaller emittance than that in the baseline design. – Lattice in the two dipole sets was not optimized to have a small emittance contribution. 2 nd sol. + decoupling quads 1 st sol. + decoupling quads Dipole set New Baseline JLEIC Collaboration Meeting Fall 2016 Dipole set 13 13

Emittance @ 10 Ge. V Normalized Horizontal Emittance ( m) Section Baseline design Optimized

Emittance @ 10 Ge. V Normalized Horizontal Emittance ( m) Section Baseline design Optimized design * Regular FODO cells in two arcs 476 569 Matching sections between FODO cells and spin rotators 389 6 Spin rotators 119 84 84 85 0 0 1068 745 Straight with IP (CCB + Chicane) Straight without IP Total Extra space needed (m) JLEIC Collaboration Meeting Fall 2016 111 14 14

Summary of Optimized Baseline Design Optimized electron collider ring with reduced-emittance ring (for nonlinear

Summary of Optimized Baseline Design Optimized electron collider ring with reduced-emittance ring (for nonlinear dynamics studies) circumference of 2185. 54 m=2 x 811. 84 m arcs + 2 x 280. 92 m straights – Overall geometry of the ring does not change significantly – Optimized matching and spin rotator sections, replaced CCB w/ FODO cells, reduced beta functions in BES, reduced number of straight FODO cells and phase advance – Chromaticities: (H, V) = (-113, -120) • In the baseline design: chromaticities: (H, V) = (-149 , -123) Geometric horizontal emittance x = 9. 5 nm-rad @ 5 Ge. V, energy spread p/p = 4. 5 e-4 @ 5 Ge. V In the baseline design: geometric horizontal emittances x = 14 nm-rad @ 5 Ge. V, energy spread p/p = 4. 5 e-4 @ 5 Ge. V Note that chromaticities and emittances may vary in different chromaticity compensation schemes See Yuri Nosochkov’s talk: Electron Collider Ring Chromatic Compensation and Dynamic Aperture JLEIC Collaboration Meeting Fall 2016 15

Optimized Design FFQs e- IP Compton forward e- polarimetry region detection region FFQs e-

Optimized Design FFQs e- IP Compton forward e- polarimetry region detection region FFQs e- x(m), y(m) FFQs IP forward e- detection region Compton polarimetry region Dx(m) Baseline Design Dx(m) x(m), y(m) IP Region Optics Optimization Shorter up- and downstream detector space: from (-3, 3. 2)m down to (-2. 6, 1. 6)m Smaller beta functions at FFQs, resulting in smaller beam sizes Softer bends in the middle of chicane to reduce the synchrotron background to the Compton polarimetry detectors JLEIC Collaboration Meeting Fall 2016 16

New Electron Collider Ring Option I FODO arc cell design using new magnets, same

New Electron Collider Ring Option I FODO arc cell design using new magnets, same bending radius in the arc cells as the baseline design Complete electron collider ring with circumference of 2181. 89 m = 2 x 809. 98 m arcs + 2 x 280. 97 m straights JLEIC Collaboration Meeting Fall 2016 17 17

New Magnet FODO Arc Cell Arc FODO cell (Each arc has 54 such normal

New Magnet FODO Arc Cell Arc FODO cell (Each arc has 54 such normal FODO cells) – Length 11. 4 m (half of ion ring arc cell) – arc bending radius 155. 45 m (same as in the baseline) – 108 /108 x/y betatron phase advance Dipole – – Magnetic/physical length 3. 6/3. 88 m Bending angle 36. 7 mrad (2. 1 ), bending radius 98. 2 m 0. 34 T @ 10 Ge. V (0. 41 @ 12 Ge. V) Sagitta 1. 65 cm New Quadrupoles – Magnetic/physical length 0. 56/0. 62 m – 17. 5 T/m field gradients @ 10 Ge. V (21 T/m @ 12 Ge. V) – 0. 88 T @ 50 mm radius @ 10 Ge. V (1. 06 T @ 12 Ge. V) Sextupoles – Magnetic/physical length 0. 25/0. 31 m – -624 and 262 T/m 2 field strengths @ 10 Ge. V for chromaticity compensation of the whole ring – 1. 2 T and 0. 5 T @ 60 mm radius @ 10 Ge. V (1. 4 T and 0. 6 T @ 12 Ge. V) BPMs and Correctors – Physical length 0. 05 and 0. 3 m JLEIC Collaboration Meeting Fall 2016 18 18 Baseline

Comparison of e-Ring Parameters Baseline design (FODO arc cell) w/ PEP-II magnets Optimized baseline

Comparison of e-Ring Parameters Baseline design (FODO arc cell) w/ PEP-II magnets Optimized baseline design (FODO arc cell) w/ PEP-II magnets New design (FODO arc cell) w/ new magnets m 2154 2186 2182 Bending angle per arc / figure-8 crossing angle deg 261. 7 / 81. 7 Beta stars at IP *x, y cm 10 / 2 -149 / -123 -113 / -120 -127 / -140 Ring circumference Hor. / ver. chromaticities x, y Momentum compaction factor 10 -3 2. 2 1. 9 1. 1 (reduce bunch length or V_peak ) Energy spread @ 5 and 10 Ge. V 10 -4 4. 6 / 9. 1 4. 5 / 9. 0 4. 6 / 9. 3 Normalized emittance @ 5 and 10 Ge. V rad 137 / 1093 93 / 740 54 / 433 Hori. beam sizes at IP @ 5 and 10 Ge. V m 38 / 75 31 / 62 24 / 47 Energy loss per turn @ 5 and 10 Ge. V Me. V 0. 88 / 14. 1 0. 82 / 13. 1 0. 89 / 14. 4 Total SR power @ 5 and 10 Ge. V MW 2. 7 / 10 2. 5 / 9. 2 2. 7 / 10. 2 m 15. 2 (PEP-II cell length) 11. 4 (half of ion arc cell) dipole length / sagitta m / cm 5. 4 / 3. 3 3. 6 / 1. 65 dipole bending angle / radius deg / m 2. 8 / 110. 5 2. 1 / 98. 2 quad length/strength @ 10 & 12 Ge. V m / T/m 0. 56 / 13 / 15. 6 0. 56 / 17. 5 / 21 42 44 58 Arc FODO cell length cells per arc JLEIC Collaboration Meeting Fall 2016 19 19

New Electron Collider Ring Option II Theoretical-Minimum-Emittance(TME)-like arc cell design using new magnets, same

New Electron Collider Ring Option II Theoretical-Minimum-Emittance(TME)-like arc cell design using new magnets, same bending radius in the arc cells as the baseline design Complete electron collider ring with circumference of 2166. 82 m = 2 x 786. 08 m arcs + 2 x 297. 33 m straights JLEIC Collaboration Meeting Fall 2016 20 20

New Magnet TME-like Arc Cell Arc TME-like cell (Each arc has 26 such normal

New Magnet TME-like Arc Cell Arc TME-like cell (Each arc has 26 such normal TME-like cells) – Length 22. 8 m (same as ion ring arc cell) – arc bending radius 155. 45 m (same as in the baseline) – 270 /90 x/y betatron phase advance Dipole – – Magnetic/physical length 4. 0/4. 28 m Bending angle 36. 7 mrad (2. 1 ), bending radius 109. 1 m 0. 31 T @ 10 Ge. V (0. 37 @ 12 Ge. V) Sagitta 1. 83 cm Quadrupoles – Magnetic/physical length 0. 56/0. 62 and 1. 0/1. 06 m – 20 T/m field gradients @ 10 Ge. V (24 T/m @ 12 Ge. V) – 1. 0 T @ 50 mm radius @ 10 Ge. V (1. 2 T @ 12 Ge. V) Sextupoles – Magnetic/physical length 0. 25/0. 31 m – 400 and 604 T/m 2 field strengths @ 10 Ge. V for chromaticity compensation of the whole ring – 0. 72 T and 1. 08 T @ 60 mm radius @ 10 Ge. V (0. 86 T and 1. 3 T @ 12 Ge. V) BPMs and Correctors – Physical length 0. 05 and 0. 25 m JLEIC Collaboration Meeting Fall 2016 21 21

Comparison of e-Ring Parameters Optimized baseline design (FODO arc cell) w/ PEP-II magnets New

Comparison of e-Ring Parameters Optimized baseline design (FODO arc cell) w/ PEP-II magnets New design (FODO arc cell) w/ new magnets New design (TME arc cell) w/ new magnets m 2186 2182 2167 Bending angle per arc / figure-8 crossing angle deg 261. 7 / 81. 7 Beta stars at IP *x, y cm 10 / 2 -113 / -120 -127 / -140 -152 / -150 Ring circumference Hor. / ver. chromaticities x, y Momentum compaction factor 10 -3 1. 9 1. 1 (reduce bunch length or V_peak) 0. 5 (reduce bunch length or V_peak) Energy spread @ 5 and 10 Ge. V 10 -4 4. 5 / 9. 0 4. 6 / 9. 3 4. 5 / 9. 1 Normalized emittance @ 5 and 10 Ge. V rad 93 / 740 54 / 433 31 / 247 Hori. beam sizes at IP @ 5 and 10 Ge. V m 31 / 62 24 / 47 18 / 36 Energy loss per turn @ 5 and 10 Ge. V Me. V 0. 82 / 13. 1 0. 89 / 14. 4 0. 89 / 13. 4 Total SR power @ 5 and 10 Ge. V MW 2. 5 / 9. 2 2. 7 / 10. 2 2. 5 / 9. 5 m 15. 2 (PEP-II cell length) 11. 4 (half of ion arc cell) 22. 8 (ion ring arc cell) dipole length / sagitta m / cm 5. 4 / 3. 3 3. 6 / 1. 65 4. 0 / 1. 83 dipole bending angle / radius deg / m 2. 8 / 110. 5 2. 1 / 98. 2 2. 1 / 109. 1 quad length/strength @ 10 & 12 Ge. V m / T/m 0. 56 / 13 / 15. 6 0. 56 / 17. 5 / 21 0. 56, 1. 0 / 24 44 58 28 Arc TME-like cell length cells per arc JLEIC Collaboration Meeting Fall 2016 22 22

Electron Polarization Requirements Major JLEIC electron complex components electron collider ring 3 – 10

Electron Polarization Requirements Major JLEIC electron complex components electron collider ring 3 – 10 Ge. V/c CEBAF Polarization design requirements – Electron polarization of 70% or above with sufficiently long lifetime – Longitudinal polarization at IP(s) – Spin flipping JLEIC Collaboration Meeting Fall 2016 23

Electron Polarization Strategies Highly vertically polarized electron beams are injected from CEBAF – avoid

Electron Polarization Strategies Highly vertically polarized electron beams are injected from CEBAF – avoid spin decoherence, simplify spin transport from CEBAF to MEIC, alleviate the detector background Polarization is designed to be vertical in the JLEIC arc to avoid spin diffusion and longitudinal at collision points using spin rotators Universal spin rotator (fixed orbit) rotates the electron polarization from 3 to 12 Ge. V Desired spin flipping is implemented by changing the source polarization Polarization configuration with figure-8 geometry removes electron spin tune energy dependence – Significantly suppress the synchrotron sideband resonance Continuous injection of electron bunch trains from the CEBAF is considered to – preserve and/or replenish the electron polarization, especially at higher energies Spin matching in some key regions is considered to further improve polarization lifetime Compton polarimeter is considered to measure the electron polarization – Two long opposite polarized bunch trains (instead of alternate polarization between bunches) simplify the Compton polarimetry bunch train & polarization pattern (in arcs) 2. 1 ns 476 MHz Empty buckets … Polarization (Up) JLEIC Collaboration Meeting Fall 2016 24 … Empty buckets … Polarization (Down) …

Universal Spin Rotator (USR) Solenoid decoupling & Lattice function Schematic drawing of USR Half

Universal Spin Rotator (USR) Solenoid decoupling & Lattice function Schematic drawing of USR Half Solenoid Arc Half Solenoid Quad. Decoupling Insert IP P. Chevtsov et al. , Jlab-TN-10 -026 Parameters of USR for JLEIC 1 st sol. + decoup. quads 2 nd sol. + decoup. quads Dipole set E Solenoid 1 BDL Ge. V Spin Rotation rad 3 Arc Dipole 1 Solenoid 2 Arc Dipole 2 Spin Rotation rad BDL T·m Spin Rotation rad π/2 15. 7 π/3 0 0 π/6 4. 5 π/4 11. 8 π/2 23. 6 π/4 6 0. 62 12. 3 2π/3 1. 91 38. 2 π/3 9 π/6 15. 7 π 2π/3 62. 8 π/2 12 0. 62 24. 6 4π/3 1. 91 76. 4 2π/3 JLEIC Collaboration Meeting Fall 2016 25 25 Dipole set

Electron Polarization Configuration Unchanged polarization in two arcs by having opposite solenoid field directions

Electron Polarization Configuration Unchanged polarization in two arcs by having opposite solenoid field directions in two spin rotators in the same long straight section – figure-8 removes spin tune energy dependence and reduces the synchrotron sideband resonances – First order spin perturbation in the solenoids for off-momentum particles vanishes with opposite longitudinal solenoid fields in the pair of spin rotators in the same long straight – Sokolov-Ternov self-polarization process has a net depolarization effect, but the polarization lifetime is still large with highly-polarized injected electron beams – Two polarization states coexist in the collider ring and have the same polarization degradation e. Spi n. R ota tor Magnetic field Polarization IP Polarization orientation Arc Solenoid field JLEIC Collaboration Meeting Fall 2016 Solenoid field IP 26 26 Arc

Polarization Simulation Spin tune scan @ 5 Ge. V Preliminary spin tracking – –

Polarization Simulation Spin tune scan @ 5 Ge. V Preliminary spin tracking – – Longitudinal field spin tuning solenoid is inserted in the straight where the polarization is longitudinal. 500 particles Monte-Carlo simulation using SLICKTRACK (developed by D. P. Barber). Main field errors, quads vertical misalignment and dipole role, are introduced. – – 10 particles Monte-Carlo simulation using Zgoubi (developed by F. Meot, BNL). Initial polarization is longitudinal. Perfect machine, no errors. Optimum Spin Tune 0. 0267 with a 3 Tm solenoid Figure-8 JLEIC collider ring has no synchrotron sideband resonances ! Oscillation of spin components is due to the misaligned initial spin direction and invariant spin field. This can be experimentally calibrated by adjusting the spin rotator settings. Nasty, nasty sidebands ! JLEIC Collaboration Meeting Fall 2016 27 27

Continuous Injection Continuous injection (or top-off injection or trickle injection) has been applied in

Continuous Injection Continuous injection (or top-off injection or trickle injection) has been applied in many modern electron storage ring light sources to maintain a constant beam current, and colliders (such as PEP-II, Super. B) to gain the average luminosity – Average luminosity is always near the peak luminosity – The collider looks like a “DC” accelerator allowing an improved operational consistency From John T. Seeman, SLAC-PUB-5933, Sep. 1992 JLEIC considers the continuous injection of the electron beams to – Obtain a high average luminosity – Reach a high equilibrium polarization Lost or Extracted P 0 (>Pt) Pt – Note that • If the beam lifetime is shorter than the polarization lifetime, continuous injection maintains the beam current and improves the polarization as well • If the beam lifetime is longer than the polarization lifetime, beam lifetime has to been shorten (collimation, scraping, or reduce the dynamic aperture) JLEIC Collaboration Meeting Fall 2016 28 28

Polarization w/o Cont. Injection Relative Polarization (%) Injection pattern on polarization Averaged Pol. Time

Polarization w/o Cont. Injection Relative Polarization (%) Injection pattern on polarization Averaged Pol. Time (arbitrary scale) : Initial polarization : Depolarization time Energy (Ge. V) inj (min) opt_meas (min) (Pave/Pi)max * 3 12 160 0. 94 5 8 60 0. 88 7 4 20 0. 85 9 0. 8 6 0. 89 10 0. 5 2. 5 0. 86 : Injection time : Measurement time JLEIC Collaboration Meeting Fall 2016 29 29

Polarization w Cont. Injection Polarization w/ continuous injection Equilibrium polarization A relatively low average

Polarization w Cont. Injection Polarization w/ continuous injection Equilibrium polarization A relatively low average injected beam current of tens-of-n. A level can maintain a high equilibrium polarization in the whole energy range. JLEIC Collaboration Meeting Fall 2016 30 30

Summary and Outlook Summary – The 2. 2 km baseline design of the JLEIC

Summary and Outlook Summary – The 2. 2 km baseline design of the JLEIC electron collider ring is summarized. – The optimization of the electron ring baseline design to reduce the emittance is reported. – Two electron collider ring design options to significantly reduce the emittance are discussed. – Electron polarization design and simulation results are reported. Outlook − Finish the study of chromaticity compensation schemes to help determine the electron collider ring design − Perform a complete nonlinear beam dynamics study considering effect of misalignment, field errors and multipole fields, specify alignment and strength error tolerances − Perform electron spin tracking to study higher-order resonances, spin effect of the detector solenoid and beam-beam effect on the spin JLEIC Collaboration Meeting Fall 2016 31

Thank You for Your Attention ! JLEIC Collaboration Meeting Fall 2016 32

Thank You for Your Attention ! JLEIC Collaboration Meeting Fall 2016 32

Back Up JLEIC Collaboration Meeting Fall 2016 33

Back Up JLEIC Collaboration Meeting Fall 2016 33

Magnet Inventory of MEIC e-Ring Magnet category PEP-II HER magnet Number New magnet Max.

Magnet Inventory of MEIC e-Ring Magnet category PEP-II HER magnet Number New magnet Max. Strength Number Max. Strength Dipole 168 0. 3 T 34 0. 64 T Quadrupole 263 17 T/m 151 25 T/m Sextupole 104 600 T/m 2(? ) 32 600 T/m 2 12 2. 33 T/m 331 283 0. 02 T 48 0. 02 T Skew quadrupole BPM Corrector MEIC (total) – – – Dipoles: 202 Quads: 414 Sextupoles: 136 Skew quads: 12 Correctors: 331 JLEIC Collaboration Meeting Fall 2016 PEP-II (total, from Super. B CDR) – – – 34 Dipoles: 200 Quads: 291 Sextupoles: 104 Skew quads: 12 Correctors: 283 Study of PEP-II magnets will be discussed in Tommy Hiatt’s talk.