Transcript 28} FETS Meeting 12April11 RFQ Output Matcher

Tuning the Frequency of
the RFQ High Energy End
What are the issues?
• Both input & output ends of RFQ must be
independently tuned for 324 MHz
• Design of last few modulations undecided:
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Stop RFQ at last modulation cell?
Add 5 mm radius onto end of last cell?
Add Crandall cell (for quadrupole symmetry)?
Add Crandall cell and output matcher?
• Can any/all of these designs be tuned?
• Matt Easton doing particle tracking for all
• Note: copper already purchased!
Last Few Modulations
End RFQ at last cell
310.5 MHz (can be easily tuned)
Add one βλ/4 (half-)Crandall cell
312.2 MHz (can be easily tuned)
Note: Crandall cell should be βλ/2, but wanted to save space…
Proper length cell would be similar frequency to those above.
Tuning Frequency of Output End
Varying vane cut-back
radius of curvature is
an easy way to tune
output end of RFQ,
with or without a
Crandall cell.
Output Matcher
409.9 MHz (not easily tuned!)
Assumes we use a Crandall cell to create
quadrupole symmetry after the last modulation
2βλ Input Matcher (Final Design)
1βλ Output Matcher (test)

1
LC
Much lower capacitance of an output matcher
increases local frequency to 410 MHz!
Try to Tune Output Matcher
No amount of tweaking to inductance and
capacitance can bring frequency down to 324 MHz
Summary
• Basic RFQ output end can be tuned
• Probably good to include a Crandall cell
to remove jitter in beam final energy
• Output matcher not easy to tune…
• …and not enough copper for one anyway!