8 GeV Injector

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8 GeV Injector Linac
Proton Driver
Front End Status 2
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Short focusing period, variable ? and moderate
accelerating rate. More details.
cavity
Simplified model of longitudinal motion
constant accelerating rate, constant period,
thin cavities, no current But it is not
adiabatic.
L
particle
?s 30
? 2
Theory
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Short focusing period, variable ? and moderate
accelerating rate. More details.
P.Bertrand for GANIL
?0.07 ?30? L0.5 m HWR
? gt90
For ? gt 90 we get unstable longitudinal motion
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Short focusing period, variable ? and moderate
accelerating rate. More details.
? gt 90
Parametric resonance
We are restricted by L ? 40 cm, ?W ? 300 keV
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Three reasons in favor of variable beta.
1) We can not afford low efficiency due to the
beam sliding relatively of RF wave.
2) Due to the bigger phase oscillation the
particles are appeared in the nonlinear part
of the separatrix, which one causes the
growth of the longitudinal emittance.
3) Variable beta is not a big deal for RT
cavities.
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Current variant is still under consideration
(J-PARC DTL is a back up)
But short SDTL variant is rejected
14.3 m
Ion Source
RFQ
MEBT
Short CH cavities SC solenoids
SSR
3- ?15 MeV
? 15-30 MeV
3 MeV
12.5 cm
4 gap CH
2?? 14.8 cm
SC quadrupole in individual cryostat
35 cm ?
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Cross-bar H-type cavities.
Drift tube inner diameter 12 mm for all
cavities (it was 20 mm). This morning a new
table arrived 20 cavities from 3 to 18 MeV,
aperture 12 mm for cavities 1-10, 15 mm
for cavities 11-20.
Still well below 1MW for all cavities beam
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How CH looks today
Ez(z)
E field
Surface currents
This kind of design may save a lot of space
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• Conclusion
• RT cavities between RFQ and SC is a right
  decision. Due to several reasons which are
  discussed in the paper there is a huge
  advantageous to use independently phased RT
  CH-cavities between the RFQ and SC sections in
  the energy range 3-15 MeV. (P.Ostroumov et all
  for PAC05, to be published)
• Parameters of front end are still changing every
  day, but in our search we are well beyond all
  restrictions (power, accelerating rate, length)
• Our goal 1 at the moment prepare full set of
  fields for beam dynamic simulations at ANL. Even
  if it is not final version.