Reducing the momentum spread of 8-GeV Booster beams via the excitation of the bunch length oscillation (simulation results)

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Reducing the momentum spread of 8-GeV Booster
beams via the excitation of the bunch length
oscillation(simulation results)

• X. Yang, A. Drozhdin, and W. A. Pellico

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Motivation
In order to reduce the beam loss for slip
stacking in Main Injector, the momentum spread of
8 GeV Booster beams is required to be less than 8
MeV (95). Bunch rotation at the end of a cycle
via rf voltage reduction was applied for such
purpose. However, the fast rf voltage reduction
often causes beam loading problems to Booster rf
stations, which effect the reliability of
extracted beams. An alternative method, which
introduces bunch length oscillations at the end
of a cycle via the modulation of the rf
accelerating voltage with twice the synchrotron
frequency, has been tried. The 8 GeV beam is
extracted at the time when the bunch length
reaches the maximum and the momentum spread
becomes the minimum.
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Including space charge effect and radial
feedback, at the extraction intensity of 4.9e12,
with the operational rf voltage of 0.4 MV in the
beginning of the rf modulation. RF voltage vs.
turn number are printed at the top with four
different amplitude modulations, 15 (red), 25
(green), 35 (blue), and 45 (magenta). ?P in
95 vs. turn number are printed at the bottom.
Turn number
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dP, MeV
dP, MeV
dP, MeV
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df, radian
Longitudinal phase plane at turns 18633
(intial), 19006 (dp max), 19081 (dp9.0MeV min),
19145 (dp max), 19220 (dp7.7MeV min), 19285 (dp
max), 19358 (dp7.5MeV min), 19424 (dp max), and
19495 (dp8.45MeV min) are printed. 95 momentum
spread vs. turn number is shown at the top right
with labels of where those turns are.
Turn 19424
Turn 19495
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Including space charge effect and radial
feedback, at the extraction intensity of 4.9e12,
with the rf voltage of 0.65 MV in the beginning
of the rf modulation. RF voltage vs. turn number
are printed at the top with four different
amplitude modulations, 15 (red), 25 (green),
35 (blue), and 45 (magenta). ?P in 95 vs.
turn number are printed at the bottom.
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Measured bunch length in 4s at 14 (stacking
cycle) vs. sample point.
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Un-calibrated rf voltage and bunch length
signals. RF accelerating voltage (magenta) and
bunch length (blue) from peak detector vs. time.
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Conclusions