# Presentation: 188853

## Debuncher “phase jump” project

- Decouple Debuncher RF frequency from MI 120 GeV frequency
- 53.103080 MHz could move by ~1-2 kHz
- Can center beam in Debuncher (Steve W’s ESME graphs)
- Added degree of freedom will facilitate 8 GeV energy match with RR
- Could even stack at higher flat-top energy

## MI RF at 120 GeV (say 53.103 MHz):

- Desired Debuncher RF (say 53.101 MHz):
- digitally synthesized with DAC driven by programmable logic

- On MIBS $79 event, jump phase of synthesized Debuncher RF to match **measured** phase of MI RF, plus programmable offset
**phase jump ******** bucket-to-bucket transfer still works**

## Implementation: reprogram spare MI damper board

- CPU
- slow control

- FPGA
- signal processing

- TTL I/O

- ADC input (x4)
- 12 bit, 212 MS/s

- DAC output (x4)
- 12 bit, 424 MS/s

- Ethernet (Acnet etc)

- Fast ADC + digital logic measures MI phase
- Digital logic + fast DAC replaces VCO in Debuncher LLRF

## The FPGA (programmable logic) coding looks like something in between writing a program and drawing a schematic.

## Debuncher LLRF (AP50)

- Damper board

## For now, we swap out VCO module during tests (DDS signal replaces raw VCO)

## Initial test: looked at MI RF, new RF, and BPM signal on scope, to see that MI RF and new RF line up on first turn
Last Friday: Dave P. and I plugged in modified VCO module toward end of Keith’s bump studies, and stayed in once stacking started back up
Flux capacitor scope showed that once we set synthesizer’s phase offset, it continued to match up on future $29 cycles
Is there a way to plot measured phase on a FTP?
Stacking rate (~3.7E10/hr, with a stack of ~180E10) with synthesizer was about the same as stacking rate once VCO was put back
But cavities had detuned by the time we started stacking, so we couldn’t check the bunch rotation
Is it easy to look at momentum spread just after bunch rotation?
Other good Debuncher diagnostics I should learn to use?

- Last Friday: Dave P. and I plugged in modified VCO module toward end of Keith’s bump studies, and stayed in once stacking started back up
- Flux capacitor scope showed that once we set synthesizer’s phase offset, it continued to match up on future $29 cycles
- Is there a way to plot measured phase on a FTP?
- Stacking rate (~3.7E10/hr, with a stack of ~180E10) with synthesizer was about the same as stacking rate once VCO was put back
- But cavities had detuned by the time we started stacking, so we couldn’t check the bunch rotation
- Is it easy to look at momentum spread just after bunch rotation?
- Other good Debuncher diagnostics I should learn to use?

## Next test (this week?)

- Get DDS amplitude right (took us a while last time)
- See if stacking works OK during a long test
- Plot flux capacitor error signal over many cycles?
- Look at momentum spectrum after bunch rotation, before and after swapping VCO modules
- Try moving MI frequency (to MI central orbit), keeping Debuncher constant, and see if stacking rate is preserved
- How long to retune if Debuncher moved down from 53.103 to 53.102?  (Then look at tails in post-bunch-rot momentum spectrum.)
- How easy for me to learn what these studies could break and how to fix it or re-tune it?

## Rotator cavities on, 219us before beam arrives; stay on for 306us (DRF1-2 fanback shown).  Need phase stable before this (no problem: phase jump occurs 295us before beam).