Beam Dynamics Update

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Beam Dynamics Update

• P.N. Ostroumov, I. Gonin, T. Khabibulin
• August 10, 2006

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BD update

• 200 mm space for beam instruments
• Re-tune lattice
• HOM issues
• Monopoles
• Dipoles

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Space for beam instrumentation 200 mm
200 mm
200 mm
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(No Transcript)
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RMS emittance growth (43.25 mA) ref. lattice
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RMS emittance growth (43.25 mA) new lattice
with the increased inter-cryostat spaces
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HOM

• MWS predicts total 69 monopoles up to 2616 MHz
• Dipole modes total 96 modes up to 2416 MHz
• Except several modes, all modes have very low
  shunt impedance

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F675.43 MHz, Q1070. Rd/Q0.81
F689.44 MHz, Q1144.
F652.56 MHz, Q6.34e8. Rd/Q1775
F689.44 MHz, Q1144. R/Q0.001.
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F2500.07 MHz, Q8100.
F717 ?.
F2551.29 MHz, Q1.47e7
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Monopoles

• Resonance with beam structure very dangerous,
  will generate significant power load to
  cryogenics
• Resonance frequencies nf0??mfchopper, due to
  high Q the resonance width is very narrow

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Example
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Total beam induced power in all monopole HOMs in
SSR

• Total power is 12 mW due to bunch structure
• Total power is 46 mW due to chopped beam
  structure
• Study of full set of resonances is required

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Dipole mode 652 MHz (HFSS), 650.88 MHz (MWS)

• Strong deflecting field
• High shunt impedance
• High Qext6.5?107
• Can be problem if frequency is stable

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Estimate of the BBU for the case of exact
resonance

• Shunt impedance
• Estimate of the beam instability in a single
  cavity (steady-state)

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Dipole mode

• Estimate of beam instability in the section with
  20 cavities (steady state)

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Dipole mode

• Solenoid focusing changes beam displacement with
  respect to the mode polarization
• High Q means very narrow bandwidth. Include
  microphonics into the beam-cavity interaction
• More studies are required
• Frequency jitter due to microphonics take
  measurements
• Rshunt as a function of azimuth
• TRACK simulation in realistic field distribution
• There are possible cures
• Forced frequency modulation ( 1 kHz) with a
  piezoelectric tuner
• Beam centroid modulation ( 1 kHz)

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HOMs in Spokes

• Quick analysis and preliminary estimates show
  that HOMs in spoke resonators are not direct
  danger both for resonator operation and beam
  quality
• More studies are required to create detailed
  report to convince community of accelerator
  physicists