JLEIC Luminosity Studies Large BeamBeam Parameter Low Emittance
JLEIC Luminosity Studies • Large Beam-Beam Parameter • Low Emittance for High Electron Energy Yuhong Zhang JLEIC Accelerator R&D Meeting, March 16, 2017
EIC Community Review Report Page 6 and 40 While the BNL RR design is near the beam-beam limit, JLEIC is far from such a limit operating with much smaller IP beta functions. These observations suggest that neither design is fully optimized and that one could enhance the performance of JLEIC, e. g. , by accepting higher beam-beam tune shifts, and the performance of the BNL RR design by further squeezing the beta functions. Depending on the acceptable IP divergence, the luminosity of either design could possibly be raised by a factor of 2 -3. We further speculate that similar design parameter optimizations can be performed for other beam energies.
EIC Community Review Report Page 20 Some of the design beam parameters appear as quite demanding (e. g. , high proton and electron bunch intensities, electron beam-beam parameter) when compared to achieved parameters in the only previous e-p collider (HERA) and other lepton colliders (e. g. , LEP) while imposing new injection procedures such as the bunch exchange injection during the beam collision process. Validation of the presented parameter choices and operation mode depends to a large extend on scaling from past colliders and on beam simulations.
Beam-Beam Parameters and Luminosity • Luminosity formula • Beam-beam parameter
e+e- Collider Luminosity Strategy Super-KEK-B, FCC/CEPC • Increasingle bunch charge Ne- and Ne+ single instabilities • Increase electron and positron beam current Ie- and Ie+ SR power multi-bunch • Decreasing vertical emittance εne-y and εne+y optics design • Decreasing vertical beta-star β*e-y and β*e+y IR design, beam dynamics
Example of Super-KEK-B
Example of Super-KEK-B Vertical emittance reduction: 14 to 18 Sub-mm beta-star demands a very different IR design (1 st FF quads very close to IP (<0. 5 m)
FCC-ee/CEPC mm beta-star Modest beam-beam nano beam (vertical emitt ~ pm)
JLEIC Parameter Constraints JLEIC additional contraints • Increasingle bunch charge Ne and Np single bunch instabilities Proton/ion bunch intensity limited by electron cooling (intensity) • Increase electron and proton beam current Ie and Ip SR power Proton beam-beam tune-shift multi-bunch Proton/ion beam limited by electron cooling (average current) • Decreasing vertical emittance εney and εnpy optics design Proton/ion emittance limited by electron cooling Electron emittance limited by synchrotron radiation • Decreasing vertical beta-star β*ey and β*py IR design, beam dynamics Large detector space for proton/ion (7 m) and electron (3 m)
JLEIC Baseline Parameters CM energy 21. 9 (low) Ge. V 44. 7 (medium) 63. 3 (high) p e p e 40 3 100 5 100 10 Beam energy Ge. V Collision frequency MHz Particles per bunch 1010 0. 98 3. 7 3. 9 3. 7 Beam current A 0. 75 2. 8 0. 75 0. 71 Polarization % 80 80 80 75 Bunch length, RMS cm 3 1 1 1 2. 2 1 Norm. emitt. , hor. /vert. μm 0. 3/0. 3 24/24 0. 5/0. 1 54/10. 8 0. 9/0. 18 432/86. 4 Horizontal & vertical β* cm 8/8 13. 5/13. 5 6/1. 2 5. 1/1 10. 5/2. 1 4/0. 8 Beam spot size at IP μm 476 23. 5 / 23. 5 476/4=119 16. 7 / 3. 3 29. 6 / 5. 9 Vert. beam-beam param. 0. 015 0. 092 0. 015 0. 068 0. 008 0. 034 Laslett tune-shift 0. 06 7 x 10 -4 0. 055 6 x 10 -4 0. 056 7 x 10 -5 3. 6/7 3. 2/3 Detector space, up/down m Hourglass(HG) reduction Luminosity/IP, w/HG, 1033 cm-2 s-1 1 0. 87 0. 75 2. 5 21. 4 5. 9
JLEIC Luminosity Optimization • In terms of Limited by cooling electron beam-beam (cooling bunch intensity) parameter Limited by electron ring (magnets, lattice/optics) Limited by SR power, proton beam-beam SR power at higher energy reduces current Limited by SR power • In terms of proton single bunch instabilities Limited by IR design (detector space, chromatic comp. , dynamic aperture) beam-beam parameter Limited by cooling (cooling bunch intensity) Limited by IR design (detector space)
JLEIC Baseline Parameters CM energy Ge. V baseline 44. 7 (medium) However, it could be a way for a future p e luminosity upgrade Beam energy doubling. Ge. V 100 5 to 952100 5 collision frequency MHz doubling. MHz beam current to ~1. 5 A for proton Collision frequency 476 ~3. 5 A for electron Particles per bunch 1010 0. 98 3. 7 0. 98 2. 6 Beam current A 0. 75 2. 8 0. 75 2 Polarization % 80 80 Bunch length, RMS cm 1 1 Norm. emitt. , hor. /vert. μm 0. 5/0. 1 54/10. 8 0. 5/0. 1 25/5 0. 35/0. 07 25/5 Horizontal & vertical β* cm 6/1. 2 5. 1/1 6/1. 2 10. 9/2. 2 6/1. 2 7. 7/1. 5 Beam spot size at IP μm Smaller emittance Large beta-star 16. 7 / 3. 3 p e 100 5 476 80 80 Smaller bunch 1 1 charge/current Smaller emittance 14 / 2. 8 Vert. beam-beam param. 0. 015 0. 068 0. 015 0. 15 Laslett tune-shift 0. 055 6 x 10 -4 3. 6/7 3. 2/3 Reach 3. 6/7 limit 3. 2/3 Reach 3. 2/3 limit 3. 6/7 Detector space, up/down m Hourglass(HG) reduction 0. 87 0. 92 0. 86 Luminosity/IP, w/HG, 1033 cm-2 s-1 21. 4 22. 6 21. 5 Same luminosity
• Global Optimization of Luminosity Over a Broad Range of Beam Energy
JLEIC e-p Luminosity • Reduction of current • Increase of emttiance
Limiting Factors of Luminosity at 100 x 10 Ge. V SR power density, Limited to 10 k. W/m • Synchrotron radiation power • Equilibrium emittance • Matching beam spot size at IP enlarge increase • Optimization lowering electron emittance at higher energy however, preserving emittance at medium and low energies
JLEIC Parameters Present baseline p e p e 100 10 Beam energy Ge. V Collision frequency MHz Particles per bunch 1010 3. 9 3. 7 Beam current A 0. 75 0. 71 Polarization % 80 75 Bunch length, RMS cm 2. 2 1 Norm. emitt. , hor. /vert. μm 0. 9/0. 18 432/86. 4 1/0. 2 213/43 0. 85/0. 17 107/21 Horizontal & vertical β* cm 10. 5/2. 1 6/1. 2 5/1 6/1. 2 8. 7/1. 7 Beam spot size at IP μm 476/4=119 4/0. 8 29. 6 / 5. 9 476/4=119 23. 6 / 4. 7 476/4=119 21. 8 / 4. 4 Vert. beam-beam param. 0. 008 0. 034 0. 008 0. 068 0. 009 0. 14 Laslett tune-shift 0. 056 7 x 10 -5 0. 05 4 x 10 -5 0. 059 9 x 10 -5 3. 6/7 3. 2/3 Detector space, up/down m Hourglass(HG) reduction Luminosity/IP, w/HG, 1033 cm-2 s-1 0. 75 0. 81 5. 9 9. 4 11. 9
Luminosity at 100 Ge. V x 10 Ge. V 12 476 MHz bunch rep rate 238 MHz bunch rep rate 119 MHz bunch rep rate Luminosity (1033/cm 2/s) 10 8 Present baseline 6 4 2 0 0 100 200 300 Normalize electron emittance (µm) 400 500 Present baseline
Electron Beam Emittance Normalize Electron Emittance (µm) 500 Present. Series 1 Baseline (FODO lattice) 400 300 200 Ideal value 100 0 3 4 5 6 7 Electron Energy (Ge. V) 8 9 • Need reducing electron emittance at 10 Ge. V by a factor of 4 • However, we want to preserve emittance at low and medium energy 10
Change of e-Beam Emittance: Bending Radius High Energy Ring PEP-II Low energy ring dipoles High energy ring dipoles Low Energy Ring Matching emittance Matching beta-star
Change of e-Beam Emittance: Bending Radius M. Sullivan • Multi-bend High energy medium energy Bending radius: 2 R turn-off Low energy turn-off Bending radius: 3 R turn-off Bending radius: R turn-off
Change of e-Beam Emittance: Bending Radius • Wiggling dipoles M. Sullivan e. RHIC ring-ring Super-bend
Change of e-Beam Emittance: Optics • High electron energy: TME lattice • Medium/low electron energy: FODO lattice • “Soft” switch between different lattices
HERA Upgrade Design Parameters
KEK-B Design Parameters
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