Beams Document 7139-v1

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3.27 GHz IIR Notch Filter for the 2-4 GHz Stacktail Momentum Cooling System

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Submitted by:
Edward W. Cullerton
Updated by:
Edward W. Cullerton
Document Created:
19 Mar 2019, 15:00
Contents Revised:
19 Mar 2019, 15:00
Metadata Revised:
20 Mar 2019, 08:59
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The stacktail momentum cooling system of the Antiproton Accumulator has
been upgraded to 2-4 GHz operation. Due to beam pipe dimensions and kicker design, a
waveguide transverse resonance at 3.27 GHz has been observed. This resonance causes
transverse heating of the core Pbar beam, hence limiting the maximum gain for the
stacktail system and ultimately the achievable stacking rate. Historically, there has been
a set of transverse kickers in that system to suppress the undesirable transverse kick
applied by the longitudinal kickers. In the original 1-2 GHz system, no such resonance
was observed allowing cancellation of the transverse kick by utilizing four correction
kickers spaced 90 degrees apart in betatron phase advance, two in each horizontal and
vertical planes. The new 2-4 GHz system presents a slightly different transverse
resonance from each of the eight kicker tanks, making it impossible to cancel the
resonance with the four installed kickers. An attempt to understand and eliminate the
source of the transverse kick has failed. It has been decided to design a special filter to
notch out the narrow resonance from the transfer function. The filter must be narrow
and not effect the phase flatness of the rest of the band. For this reason, an Infinite
Impulse Response (IIR) filter was chosen.
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