Transcript CESR-c Status - Cornell University

CESR-c Status
CESR Layout
- Pretzel, Wigglers, solenoid compensation
Performance to date
Design parameters
Our understanding of shortfall
Plans for remediation
Instrumentation
Ongoing studies
Projections
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)
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
Superconducting wiggler
prototype installed fall 2002
7-pole, 1.3m
40cm period,
161A, B=2.1T
Solenoid compensation scheme
Q2
Q1
PM
sk_q03e
Skew quad 3
sk_q03w
CLEO solenoid
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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
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
Wiggler Beam Measurements
-Injection
30 Hz 68mA/80sec
6 wiggler lattice
60 Hz 67ma/50sec
Wiggler Beam Measurements
-Single beam stability
2pm + 1 sc wigglers
1/ = 4.5 s-1
6 sc wigglers
1/ = 10.9s-1
Performance
D303.2004, 8X5, *=12mm
Performance
D303.2004
Performance
Integrated/day
Including best day
Integrated from start
Of cesrc
CESR-c design parameters
CESR-c Energy dependence
In a wiggler dominated ring
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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
Performance vs design
Bunch current
2mA/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
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-c
1.89 GeV, 12 2.1T wigglers
Phase III IR
Weak strong beambeam simulation
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Comparison with measurements
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In simulation, tune scan yields operating point
Data: Assume all bunches have equal current and contribute equal
luminosity
CESR-c
1.89 GeV, 12 2.1T wigglers
Phase III IR
5.3GeV
Phase II IR
Weak strong beambeam simulation
– Lifetime
1


1 dN 1 N

f rev
N dt N n turns
Loss of 1 of 5000 particles in 100 k turns => 20 minute lifetime
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CESR-c 9X5
CESR-c 9X4
Measure lifetime limited current ~ 2.2mA/bunch(9X5), ~2.6mA/bunch(9X4)
Compensating
solenoid
Q2
Q1
PM
Skew quad
CLEO solenoid
Anti-solenoid in IR
+
Qz=0.05
pQx+qQy+rQz=n
|p|+|q|+|r| ≤3
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Qz=0.1
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Qz=0.05
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pQx+qQy+rQz=n
|p|+|q|+|r| ≤4
Qz=0.01
Longitudinal emittance
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12 wigglers, 1.89GeV/beam
– E/E ~ 0.084%,  ~ 50 ms, h = 120nm
– p = 0.0113
– v* = 12mm
– Then l = 12mm => Qs= 0.089
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Element M inserted in ring opposite IP
– Then l = 12mm => Qs= 0.049 or Qs =0.089 => l = 7.3mm
Longitudinal emittance
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Reduced momentum compaction and no solenoid
Luminosity projection
Instrumentation
Turn by turn position at IP
Fast luminosity monitor
Bunch by bunch luminosity
Bunch by bunch position/beam size
Streak camera
Palmer
(magnification ~ 3.6)
Palmer
Ongoing study
Nonlinearities
Optical distortion due to parasitic crossings
Resonance remediation
Low momentum compaction optics