Slotfinger superconducting structure with RF focusing - PowerPoint PPT Presentation

Title: Slotfinger superconducting structure with RF focusing


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Slot-finger superconducting structure with RF
focusing

• Yu. Senichev,
• IKP, FZJ

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Supposed Scheme of HIPPI

• from JRA3 in the CARE proposal Version 26/09/2003
  with modification in annual report 2004

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At present three candidates are considered in the
energy range W3-10 MeV

• Super-conducting CH-DTL (Frankfurt Uni.)
• based on TE211 mode
• with external triplet system and 10ß? focusing
  period length
• with growing phase velocity
• Normal-conducting RFQ-DTL (IHEP)
• based on TE111 mode
• with RF focusing
• with growing phase velocity
• Super-conducting Spoke cavity(FZJ,CEA)
• based on TE211 mode
• with external focusing

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The type of structure

• Super-conducting
• higher efficiency
• higher accelerating gradient in cavity
• no requirement to shunt impedance
• but requires
• cryo-system
• Lorentz force detuning
• external quadrupoles (or strong solenoide)
• transition between the warmed-cold equipments
  decreases real accelerating gradient

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The fundamental mode

• TM010 mode
• no accelerating field variation along cavity
• easily tuning
• TE111, or TE211 mode
• - quasi-electrodynamic potential

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The transverse motion

• Focusing elements inside cryo-module
• larger acceptance
• higher current limit
• shorter drift space
• but
• requires strong field solenoide 10 T
• complicater system

• Focusing elements outside cryo-module
• simpler focusing system
• but
• smaller acceptance
• lower current limit
• additional place between cavities

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Longitudinal motion parametric resonance
3.0 MeV ltkinetic energy of protonlt20 MeV.
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RF defocusing

therefore
and defocusing kick
for initial energy 5-10 MeV the defocusing kick
17 T x Lcavity
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Main reasons, decreasing the longitudinal and
transverse acceptances of SC accelerator

• Parametric resonances
• Long focusing period
• RF defocusing in transverse planes

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New method of RF defocusing compensation
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New method of RF defocusing compensation
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The slot structure
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The slot structure highest modes
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The slot structure fundamental mode
The longitudinal component of the electrical
field in the center of the accelerating gap in
the slot and spoke resonators at Epeak40 MV/m
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The slot structure focusing component
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The slot structure field distribution
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The slot structure quadrupole component
Now the field equation is
The average meaning of the slot function is
The motion equation in the slot structure is
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The slot structure geometry optimization
Electrical field
Magnetic field
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The slot structure geometry optimization
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The slot structure comparison with spoke
CH-DTL
Slot structure
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The slot-finger structure
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The slot-finger structure highest modes
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The slot-finger structure field distribution
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The slot-finger structure flatness
Flatness
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The slot-finger structure lattice
Three options for the RF and the slot gradient
functions
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The slot-finger structure lattice
FOOD lattice
FOODDOOF lattice
where refraction angle is
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The slot-finger structure
Longitudinal-transverse coupling resonance
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The slot-finger structure
Longitudinal-transverse coupling resonance with
phase shift
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The slot-finger structure
The family- structure resonances
Nf- number of focusing period with similar
cavities
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The slot and slot-finger structureBeam dynamics

• the transverse motion equation taking into
  account the sliding factor caused by constant
  geometry in families
• the motion equation in the slot and the
  slot-finger structures
• the matrix formalism applied to the slot-finger
  rotated lattice
• the family structure resonances theory

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The slot and slot-finger structurecavity features

• due to the geometrical symmetry of resonator the
  neighbour mode TE212 is removed
• due the TE211 choice the electrodes are
  transparent for the cooling liquid
• due to the lower potential between the extreme
  electrodes and the cavity wall we have the higher
  gradient in the central cells
• due to the rotation of every second cavity we
  provide the proper lattice FOODDOF
• due to the slots we decrease the RF defocusing

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Conclusion

• We have developed the slot with and without
  finger structure based on the TE211 mode
• In comparison with the spoke it gives additional
  focusing and the technology is expected to be
  easier
• The slot-finger structure can be used in the
  range of 3-50 MeV
• The slot structure can be continued up to the
  high energy SC part
• We have investigated the beam dynamics and
  electrodynamics in the slot-finger structure
• We have analized the possible resonances in the
  slot-finger structure
• The slot-finger structure can be one of the
  candidates for the Low energy part of HIPPI

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The slot structure
TM01 mode
What is common between the wave guide with disc
and the jungle gym guide?
TM01 mode