cesr-c status

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