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CESR-c

CESR-c. BESIII/CLEO-c Workshop, IHEP January 13, 2004 D.Rubin for the CESR operations group. CESR-c. Energy reach 1.5-6GeV/beam Electrostatically separated electron-positron orbits accomodate counterrotating trains Electrons and positrons collide with ±~3.5 mrad horizontal crossing angle

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CESR-c

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  1. CESR-c BESIII/CLEO-c Workshop, IHEP January 13, 2004 D.Rubin for the CESR operations group D. Rubin - Cornell

  2. CESR-c Energy reach 1.5-6GeV/beam Electrostatically separated electron-positron orbits accomodate counterrotating trains Electrons and positrons collide with ±~3.5 mrad horizontal crossing angle 9 5-bunch trains in each beam (768m circumference) D. Rubin - Cornell

  3. CESR-c IR Summer 2000, replace 1.5m REC permanent magnet final focus quadrupole with hybrid of pm and superconducting quads Intended for 5.3GeV operation but perfect for 1.5GeV as well D. Rubin - Cornell

  4. CESR-c IR * ~ 10mm H and V superconducting quads share same cryostat 20cm pm vertically focusing nose piece Quads are rotated 4.50 inside cryostat to compensate effect of CLEO solenoid Superimposed skew quads permit fine tuning of compensation At 1.9GeV, very low peak  => Little chromaticity, big aperture D. Rubin - Cornell

  5. CLEO solenoid 1T()-1.5T() Good luminosity requires zero transverse coupling at IP (flat beams) Solenoid readily compensated even at lowest energy *(V)=10mm E=1.89GeV *(H)=1m B(CLEO)=1T D. Rubin - Cornell

  6. CESR-c Energy dependence • Beam-beam effect • In collision, beam-beam tune shift parameter ~ Ib/E • Long range beam-beam interaction at 89 parasitic • crossings ~ Ib/E (for fixed emittance) • (and this is the current limit at 5.3GeV) • Single beam collective effects, instabilities • Impedance is independent of energy • Effect of impedance ~I/E D. Rubin - Cornell

  7. CESR-c Energy dependence (scaling from 5.3GeV/beam to 1.9GeV/beam) • Radiation damping and emittance • Damping • Circulating particles have some momentum transverse • to design orbit (Pt/P) • In bending magnets, synchrotron photons radiated • parallel to particle momentum Pt/Pt = P/P • RF accelerating cavities restore energy only along • design orbit, P-> P+ P so that transverse • momentum is radiated away and motion is damped • Damping time  ~ time to radiate away all momentum D. Rubin - Cornell

  8. CESR-c Energy dependence • Radiation damping • In CESR at 5.3 GeV, an electron radiates ~1MeV/turn • ~>  ~ 5300 turns (or about 25ms) • SR Power ~ E2B2 = E4/2 at fixed bending radius • 1/ ~ P/E ~ E3 • so at 1.9GeV,  ~ 500ms • Longer damping time • Reduced beam-beam limit • Less tolerance to long range beam-beam effects • Multibunch effects, etc. • Lower injection rate D. Rubin - Cornell

  9. CESR-c Energy dependence • Emittance • L ~ IB2/  xy= IB2/ (xyxy)1/2 • x~y (coupling) • IB/ x limiting charge density • Then IB and therefore L ~ x CESR (5.3GeV), x = 200 nm-rad CESR (1.9GeV), x = 30 nm-rad D. Rubin - Cornell

  10. CESR-c Energy dependence • Damping and emittance control with wigglers D. Rubin - Cornell

  11. CESR-c Energy dependence • In a wiggler dominated ring • 1/  ~ Bw2Lw •  ~ Bw Lw • E/E ~ (Bw)1/2 nearly independent of length • (Bw limited by tolerable energy spread) Then 18m of 2.1T wiggler • ->  ~ 50ms • -> 100nm-rad <  <300nm-rad D. Rubin - Cornell

  12. Optics effects - Ideal Wiggler Bz = -B0 sinh kwy sin kwz Vertical kick ~  Bz D. Rubin - Cornell

  13. Optics effects - Ideal Wiggler Vertical focusing effect is big, Q ~ 0.1/wiggler But is readily compensated by adjustment of nearby quadrupoles Cubic nonlinearity ~ (1/ )2 We choose the relatively long period ->  = 40cm Finite width of poles leads to horizontal nonlinearity D. Rubin - Cornell

  14. 7-pole, 1.3m 40cm period, 161A, B=2.1T Superconducting wiggler prototype installed fall 2002 D. Rubin - Cornell

  15. Wiggler Beam Measurements • Measurement of betatron tune vs displacement consistent with • modeled field profile and transfer functon D. Rubin - Cornell

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  20. 6 wigglers installed spring 2003 D. Rubin - Cornell

  21. 6 Wiggler Linear Optics Lattice parameters D. Rubin - Cornell

  22. Machine Status • Commissioning with 6 wigglers beginning in August 2003 • Measure and correct linear optics • Characterize • wiggler nonlinearity • Injection • Single beam stability • Measure and correct “pretzel” dependent /sextupole • differential optics D. Rubin - Cornell

  23. Wiggler Beam Measurements Beam energy = 1.89GeV -Optical parameters in IR match CESR-c design -Measure and correct betatron phase and transverse coupling - Measurement of lattice parameters (including emittance) in good agreement with design D. Rubin - Cornell

  24. Wiggler Beam Measurements • Injection 1 sc wiggler (and 2 pm CHESS wigglers) -> 8mA/min 1/ = 4.5 s-1 6 sc wiggler -> 50mA/min 1/ = 10.9s-1 D. Rubin - Cornell

  25. Wiggler Beam Measurements6 wiggler lattice • Injection 30 Hz 68mA/80sec 60 Hz 67ma/50sec D. Rubin - Cornell

  26. Wiggler Beam Measurements • Single beam stability 6 sc wigglers 2pm + 1 sc wigglers 1/ = 10.9s-1 1/ = 4.5 s-1 D. Rubin - Cornell

  27. Measurement and correction of linear lattice Measured - modeled Betatron phase and transverse coupling D. Rubin - Cornell

  28. Sextupole optics Modeled pretzel dependence of betatron phase due to sextupole feeddown Difference between measured and modelled phase with pretzel after correction of sextupoles D. Rubin - Cornell

  29. Solenoid compensation Coupling parameters in the interaction region Beam profiles due to horizontal excitation Best luminosity D. Rubin - Cornell

  30. CESR-c Peak Luminosity D. Rubin - Cornell

  31. CESR-c integrated luminosity D. Rubin - Cornell

  32. 1-jan-2004 D. Rubin - Cornell

  33. 28-Dec-2003 2.5pb-1/day D. Rubin - Cornell

  34. CESR-c parameters D. Rubin - Cornell

  35. CESR-c Status Remaining 6 (of 12) wigglers will be installed is spring 2004 Double damping decrement -> Faster injection -> Higher single beam current -> Reduced sensitivitiy to current limiting parasitic crossings -> Higher beambeam current limit -> Increased tune shift parameter Machine studies/beam instrumentation in progress -> Improved correction of linear and nonlinear optical errors -> More precise and reliable correction of coupling errors -> Improved tuning “knobs” and algorithms D. Rubin - Cornell

  36. CESR-c design parameters D. Rubin - Cornell

  37. Machine modeling • Wiggler transfer map -Compute field table with finite element code -Tracking through field table -> transfer maps D. Rubin - Cornell

  38. Machine modeling - Fit analytic form to field table D. Rubin - Cornell

  39. Machine modeling • Wiggler map Fit parameters of series to field table Analytic form of Hamiltonian -> symplectic integration -> taylor map D. Rubin - Cornell

  40. Simulation • -Machine model includes: • Wiggler nonlinearities • Beam beam interactions • (parasitic and at IP) • -Synchrotron motion • -Radiation excitation and • damping • -Weak beam • -200 particles • - initial distribution is gaussian • in x,y,z • - track ~ 10000 turns D. Rubin - Cornell

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