Mike Martens, Page 1

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Studies of the Chromaticity, Tune, and Coupling
Drift in the Tevatron
Mike Martens, Jerry Annala, Pierre Bauer,
Vladimir Shiltsev, Gueorgui Velev 2005 Particle
Accelerator Conference Knoxville, Tennessee May
16, 2005
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b2 Drift Snapback
980 GeV Flattop
Effects discovered during Tevatron commissioning
150 GeV Injection Porch
Tevatron Energy Ramp
90 GeV Reset
b2 snaps back at start of ramp
b2 drifts at 150 Gev
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Whats New

• Discovery of Tune and Coupling Drift
• Documented and compensated for first time in Run
  II
• Challenge of Run II beam intensities
• From 6?6 to 36?36
• Improved Magnet Measurements
• P. Bauer (MOPA001), G. Velev (TPAPO29)
• Beam Measurements
• Focus of this talk
• Improved compensation algorithms
• Better understanding of dynamic effects
• Elimination of the Dry Squeeze Pre-cycle

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Tune Drifts in the Tevatron
Horizontal Tune
Vertical Tune
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Coupling Drifts in the Tevatron
Horizontal Tune
Vertical Tune
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Tune Snapback on the Ramp
After fixes
0.02 tune units
153 Gev
Desired tunes (red lines) at 0.575 and 0.583

• Large tune/coupling excursions near start of
  ramp (150 ? 153 Gev)
• Tune/coupling changes of (0.02 tune units, 0.02
  minimum tune split)
• Variations fixed with tune/coupling snapback
  correction at start of ramp.

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Magnitude of Drifts
Magnitude of drifts requires compensation using
corrector magnets.
After 1 hour on Injection Porch
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Explore dependence of ramp history with offline
magnet measurements.
Example Magnitude of drift depends on flattop
time
?b2 (units _at_ 1 inch)
Saturates after 1 hour at flattop.
Time at flattop (min)
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Parameterization of Dynamic Effects
Fast drift for few secs, then log drift with ts
300 sec
Gaussian Snapback
More drift means longer snapback time.
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Chromaticity in the Tevatron
b2
?
?
?
?
?
Measure
Measure
Calculate
Calculate
Measure
Measure/estimate average b2 in the Tevatron
dipoles
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Measured b2 Drift in Tevatron
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Measurement of snapbackat the start of Tevatron
Ramp
1 hour front porch
6 sec. front porch
b2,hysteretic (?E) -4.75 0.063 ? ?E 0.00049
? (?E)2
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Measurement of snapback
6 sec front porch b2(t) b2,hyst
0.21?exp(-(t/1.45)2)
1 hour front porch b2(t) b2,hyst
1.69?exp(-(t/4.75)2)
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Tune Drift _at_ 150 Gev
After correction algorithm was implemented
We like ??(t) lt 0.002
Why does the tune drift? Is it related to b2
drift?
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Conclusions

• Chromaticity, Tune, and Coupling Drift and
  Snapback have been measured in the Tevatron.
• Understanding has been improved and led to
  updated correction algorithms.
• Agreement between magnet measurements and
  Tevatron measurements