Tuning the Frequency ofthe 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:

– 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 ModulationsEnd RFQ at last cell Add one βλ/4 (half-)Crandall cell

Note: Crandall cell should be βλ/2, but wanted to save space…Proper length cell would be similar frequency to those above.

310.5 MHz (can be easily tuned) 312.2 MHz (can be easily tuned)

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

Assumes we use a Crandall cell to create quadrupole symmetry after the last modulation

409.9 MHz (not easily tuned!)

2βλ Input Matcher (Final Design)

1βλ Output Matcher (test)

Much lower capacitance of an output matcher increases local frequency to 410 MHz!

LC

1

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!