CESR-c and CLEO-c Physics Extending the energy reach of CESR
CESR-c Status CESR Layout - Pretzel, Wigglers, solenoid compensation Performance to date Design...
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Transcript of CESR-c Status CESR Layout - Pretzel, Wigglers, solenoid compensation Performance to date Design...
CESR-c StatusCESR Layout - Pretzel, Wigglers, solenoid compensationPerformance to dateDesign parametersOur understanding of shortfallPlans for remediationInstrumentationOngoing studiesProjections
CESR-cEnergy 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)
12 superconducting wigglers 1.4 T < Bpeak < 2.1 T - Reduce radiation damping time from 500ms to 50ms at 1.9GeV beam energy Injection rate damping rate Instability thresholds damping rate Increased beambeam limit, tolerance to long range beam-beam effects - Increase emittance from 30nm to ~100-200nm
CESR-c Energy dependence
Damping and emittance control with wigglers
7-pole, 1.3m 40cm period, 161A, B=2.1T
Superconducting wiggler prototype installed fall 2002
Solenoid compensation scheme
• PM, Q1, Q2 are rotated 4.5 degrees about axis, designed to compensate 1.5T solenoid at 5.3 GeV• Skew quad coils are superimposed on Q1 and Q2 for fine tuneing and energy
reach• Skew quad 3, is third component in “3-pair” compensation scheme• The first bending magnet is immediately beyond skew quad 3
Q2 Q1PM
CLEO solenoid
Skew quad 3 sk_q03w
sk_q03e
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
Wiggler Beam Measurements 6 wiggler lattice
-Injection
30 Hz 68mA/80sec 60 Hz 67ma/50sec
Wiggler Beam Measurements
-Single beam stability
1/ = 4.5 s-1 1/ = 10.9s-1
2pm + 1 sc wigglers 6 sc wigglers
D303.2004, 8X5, *=12mm
Performance
D303.2004
Performance
Performance
Integrated from startOf cesrc
Integrated/dayIncluding best day
CESR-c design parameters
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
Bunch current2mA/bunch vs 4mA/bunch Limited by parasitic interactions (Single bunch current limit > 4mA) Our scaling from 5.3GeV beam energy neglected contribution to beam size from energy spread and high field wigglers => large energy spread
Beam current 8X5 vs 9X5 (ion effects)
Beam beam tune shift parameter Large energy spread, energy dependence of solenoid compensation dilutes beam size at low current Large energy spread, small * => high synchrotron tune, synchrobetatron resonances limit tune shift at high current
Performance vs design
Weak strong beambeam simulation
• Comparison with measurements• In simulation, tune scan yields operating point• Data: Assume all bunches have equal current and contribute equal luminosity
CESR-c1.89 GeV, 12 2.1T wigglersPhase III IR
Weak strong beambeam simulation• Comparison with measurements
• In simulation, tune scan yields operating point• Data: Assume all bunches have equal current and contribute equal luminosity
CESR-c1.89 GeV, 12 2.1T wigglersPhase III IR
5.3GeVPhase II IR
Weak strong beambeam simulation
– Lifetime
€
1
τ=
1
N
dN
dt=
1
N
ΔN
nturns
f rev
Loss of 1 of 5000 particles in 100 k turns => 20 minute lifetime
CESR-c 9X5 CESR-c 9X4
Measure lifetime limited current ~ 2.2mA/bunch(9X5), ~2.6mA/bunch(9X4)
Q2 Q1PM
CLEO solenoid
Compensating solenoid
Skew quad
Anti-solenoid in IR
+
+
pQx+qQy+rQz=n|p|+|q|+|r| ≤3
Qz=0.05
Qz=0.1
pQx+qQy+rQz=n|p|+|q|+|r| ≤4
+
+
Qz=0.05
Qz=0.01
Longitudinal emittance• 12 wigglers, 1.89GeV/beam
E/E ~ 0.084%, ~ 50 ms, h = 120nm p = 0.0113 v
* = 12mm– Then l = 12mm => Qs= 0.089
• Element M inserted in ring opposite IP– Then l = 12mm => Qs= 0.049 or Qs =0.089 => l = 7.3mm
Longitudinal emittance• Reduced momentum compaction and no solenoid
Luminosity projection
Instrumentation
Turn by turn position at IPFast luminosity monitor Bunch by bunch luminosityBunch by bunch position/beam sizeStreak camera
Palmer
(magnification ~ 3.6)Palmer
Ongoing study
NonlinearitiesOptical distortion due to parasitic crossingsResonance remediationLow momentum compaction optics