January 13, 2004D. Rubin - Cornell1 CESR-c BESIII/CLEO-c Workshop, IHEP January 13, 2004 D.Rubin for the CESR operations group

January 13, 2004D. Rubin - Cornell2 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)

January 13, 2004D. Rubin - Cornell3 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

January 13, 2004D. Rubin - Cornell4 CESR-c IR  * ~ 10mm H and V superconducting quads share same cryostat 20cm pm vertically focusing nose piece Quads are rotated 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

January 13, 2004D. Rubin - Cornell5 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

January 13, 2004D. Rubin - Cornell6 CESR-c Energy dependence Beam-beam effect In collision, beam-beam tune shift parameter ~ I b /E Long range beam-beam interaction at 89 parasitic crossings ~ I b /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

January 13, 2004D. Rubin - Cornell7 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 (P t /P) In bending magnets, synchrotron photons radiated parallel to particle momentum  P t /P t =  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

January 13, 2004D. Rubin - Cornell8 CESR-c Energy dependence Radiation damping In CESR at 5.3 GeV, an electron radiates ~1MeV/turn ~>  ~ 5300 turns (or about 25ms) SR Power ~ E 2 B 2 = E 4 /  2 at fixed bending radius 1/  ~ P/E ~ E 3 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

January 13, 2004D. Rubin - Cornell9 CESR-c Energy dependence Emittance L ~ I B 2 /  x  y = I B 2 / (  x  y  x  y ) 1/2  x ~  y (coupling) I B /  x limiting charge density Then I B and therefore L ~  x CESR (5.3GeV),  x = 200 nm-rad CESR (1.9GeV),  x = 30 nm-rad

January 13, 2004D. Rubin - Cornell10 CESR-c Energy dependence Damping and emittance control with wigglers

January 13, 2004D. Rubin - Cornell11 CESR-c Energy dependence In a wiggler dominated ring 1/  ~ B w 2 L w  ~ B w L w  E /E ~ (B w ) 1/2 nearly independent of length (B w limited by tolerable energy spread) Then 18m of 2.1T wiggler ->  ~ 50ms -> 100nm-rad <  <300nm-rad

January 13, 2004D. Rubin - Cornell12 Optics effects - Ideal Wiggler B z = -B 0 sinh k w y sin k w z Vertical kick ~  B z

January 13, 2004D. Rubin - Cornell13 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

January 13, 2004D. Rubin - Cornell14 7-pole, 1.3m 40cm period, 161A, B=2.1T Superconducting wiggler prototype installed fall 2002

January 13, 2004D. Rubin - Cornell15 Wiggler Beam Measurements -Measurement of betatron tune vs displacement consistent with modeled field profile and transfer functon

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January 13, 2004D. Rubin - Cornell20 6 wigglers installed spring 2003

January 13, 2004D. Rubin - Cornell21 6 Wiggler Linear Optics Lattice parameters Beam energy[GeV]1.89  * v [mm]  * h [m] Crossing angle[mrad] Q v Q h Number of trains Bunches/train Bunch spacing[ns] Accelerating Voltage[MV] Bunch length[mm] Wiggler Peak Field[T] Wiggler length[m] Number of wigglers  x [mm-mrad]  E /E[%]

January 13, 2004D. Rubin - Cornell22 Machine Status Commissioning with 6 wigglers beginning in August Measure and correct linear optics -Characterize - wiggler nonlinearity -Injection -Single beam stability -Measure and correct “pretzel” dependent /sextupole differential optics

January 13, 2004D. Rubin - Cornell23 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

January 13, 2004D. Rubin - Cornell24 Wiggler Beam Measurements -Injection 1 sc wiggler (and 2 pm CHESS wigglers) -> 8mA/min 6 sc wiggler -> 50mA/min 1/  = 4.5 s -1 1/  = 10.9s -1

January 13, 2004D. Rubin - Cornell25 Wiggler Beam Measurements 6 wiggler lattice -Injection 30 Hz 68mA/80sec60 Hz 67ma/50sec

January 13, 2004D. Rubin - Cornell26 Wiggler Beam Measurements -Single beam stability 1/  = 4.5 s -1 1/  = 10.9s -1 2pm + 1 sc wigglers 6 sc wigglers

January 13, 2004D. Rubin - Cornell27 Measurement and correction of linear lattice Measured - modeled Betatron phase and transverse coupling

January 13, 2004D. Rubin - Cornell28 Sextupole optics Modeled pretzel dependence of betatron phase due to sextupole feeddown Difference between measured and modelled phase with pretzel after correction of sextupoles

January 13, 2004D. Rubin - Cornell29 Beam profiles due to horizontal excitation Best luminosity Solenoid compensation Coupling parameters in the interaction region

January 13, 2004D. Rubin - Cornell30 CESR-c Peak Luminosity

January 13, 2004D. Rubin - Cornell31 CESR-c integrated luminosity

January 13, 2004D. Rubin - Cornell32 1-jan-2004

January 13, 2004D. Rubin - Cornell33 2.5pb -1 /day 28-Dec-2003

January 13, 2004D. Rubin - Cornell34 CESR-c parameters ParameterMeasured (Design) Beam energy[GeV]1.88 (1.88) Luminosity[10 30 /cm 2 /s ] 45 (300) I b [ma/bunch]1.7 (4) I beam [ma/beam]55 (180) vv (0.04) hh Wigglers6 (12)  E /E[10 -4 ] 0.8 (0.81)  [ms] 110 (55) B w [T]2.1(2.1)  * v [mm] 13 (10)  h [nm]160 (220)

January 13, 2004D. Rubin - Cornell35 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

January 13, 2004D. Rubin - Cornell36 CESR-c design parameters

January 13, 2004D. Rubin - Cornell37 Machine modeling -Wiggler transfer map -Compute field table with finite element code -Tracking through field table -> transfer maps

January 13, 2004D. Rubin - Cornell38 Machine modeling - Fit analytic form to field table

January 13, 2004D. Rubin - Cornell39 Machine modeling -Wiggler map Fit parameters of series to field table Analytic form of Hamiltonian -> symplectic integration -> taylor map

January 13, 2004D. Rubin - Cornell40 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 ~ turns