# Presentation: 837146

## APEXHF Schottky Calibration

- Peter Cameron and Al Dellapenna

- 17 Mar 2006

## Outline

- BBQ – parasitic to resonance compensation
- “Mission Accomplished”, but......
- 3D sensitivity to beam loss
- Emittance calibration of HF Schottky
- Preparation – parasitic behind a store
- The experiment
- Conclusion – high resolution, significant potential value
- Chromaticity Calibration
- A caution to Operations
- Artus in chrom application did not give meaningful and reliable chrom measurements during this study.
- Is this also sometimes the case during normal operations?
- HFS chrom measurements are presently useless. This requires further study, algorithm refinement

- 17 Mar 2006

## BBQ

- Steve Peggs – “declare Victory”
- Peter Cameron – “Mission Accomplished”
- One messy little detail
**BBQ sensitivity to electrons/beam loss (thank you Mike Brennan)**
- We are working on it

- 17 Mar 2006

## BBQ during tune scan ( const)

- Vert
- I and Q

- Tunes and beam decay

- Horiz
- I and Q

- ~.01 units of tune

- 17 Mar 2006

## BBQ – effect of beam loss

- Vert
- I and Q

- Tunes and beam decay

- Horiz
- I and Q

- loss of lock

- 17 Mar 2006

## BBQ

- Steve Peggs – “declare Victory”
- Peter Cameron – “Mission Accomplished”
- Steve Peggs – “tell them what you’re going to tell them, then tell them, then tell them what you told them”** **
- Peter Cameron – “Mission Accomplished”
- Just one messy little detail
**Sensitivity to beam loss/electrons**
**And one more puzzle**
**Anomalous sensitivity to tune separation (at small and large tune separations, but not at intermediate ie <700Hz) when fully decoupled**

- 17 Mar 2006

## Outline

- BBQ – parasitic to resonance compensation
- Emittance calibration
**Preparation – parasitic behind a store**
- The experiment
- Chromaticity Calibration

- 17 Mar 2006

##  calibration - the principle

- Simple
- Schottky pickup is moveable      controllable beam offset
- Schottky signal is macro-particle of charge sqrt(N), where N is number of beam particles
- This macro-particle deposits power in the spectrum at both revolution and betatron frequencies
- Beam offset at which power in rev line equals power in betatron line is the rms beam sigma (see next slide)
- For preliminary exploration we just did this by eye

- 17 Mar 2006

## Spectra at 3 pickup positions

**Spectra at 3 pickup positions**

- Counts = 75

- Counts = 1275

- Counts = 675

- 17 Mar 2006

## mirrored down

- for least squares fit

- Departure from straight line indicates non-Gaussian profile, **can be fit** **to determine profile**

- 17 Mar 2006

## Comparison with IPM

**Comparison with IPM**

- Blue IPM and Schottky are both at the Q4 end of sector 2, a few meters apart
- Schottky says **** ~ 0.8mm
- IPM says **** ~ 1.68mm * sqrt(20/29) = 1.4mm
- With difference gives ~factor of 2? Where?

- 17 Mar 2006

## More comparison with IPM

**More comparison with IPM**

- Resolution > x10 better
- No beam kick
- May be useful on ramp
- Schottky point every 4 sec

- flattop

- 17 Mar 2006

## Yet more comparison with IPM

**Yet more comparison with IPM**

- These differences are meaningful – related to shape of transverse profile

**IPM**

- Schottky

- 17 Mar 2006

## The experiment

**The experiment**

- Preliminary data was taken at store
- This experiment at injection
- Large distorted revolution line – problem for cal only
- Distorted betatron lines - from turning Landau off?
- Abandoned this part of the experiment (can be done parasitically to stores) to concentrate on chromaticity

- 17 Mar 2006

## Schottky emittance measurement

- Has excellent resolution
- Beam decay monitor more useful than Current monitor for tuning
- Might an ‘emittance decay monitor’ (% emittance gain/hr) be more useful than an emittance monitor?
- Schottky has sufficient resolution to permit this
- Data is always there, for free – does not perturb the beam
- Can be given absolute calibration via moveable pickup
- Profile can be extracted from position scan
- For the most part agrees well with IPM. When it does not, there is useful information (shape of transverse profile)
- Relatively small effort to make this available at store
- Slightly larger effort to make it available at injection and on the ramp (LO frequencies need to be tied to frev)

- 17 Mar 2006

## Outline

- BBQ – parasitic to resonance compensation
- Emittance calibration
- Preparation – parasitic behind a store
- The experiment
**Chromaticity Calibration**

- 17 Mar 2006

##  calibration - the principle

- Simple
- Measure linear and non-linear chrom via standard radial shift method, using Artus and BBQ
- Compare with Schottky
- Change the chromaticity
- Repeat

- 17 Mar 2006

## Blue at the start

- Artus drawn to other eigenmode?

- 17 Mar 2006

## Blue tunes

**** +2 both planes

**** +1 both planes

**** +2 both planes

**** +1 both planes

- 17 Mar 2006

## Blue chromaticity

**** +2 both planes

**** +1 both planes

**** +2 both planes

**** +1 both planes

- 17 Mar 2006

## Blue summary

- Data pretty confusing, the only one I trust is BBQ in this data set
- A caution for operations?
- Schottky algorithm needs refinement
- Present calculation is ad hoc, complex, many fudge factors
- Need to incorporate calculation of non-linear chromaticity

- 17 Mar 2006

## Yellow overall

- Opposite shift - Artus is wrong sign for +chrom at integer minus tune

- h +2

- h +1
- v +1

- restore

- 17 Mar 2006

## Yellow Summary

- Data dumped to elog was for Blue!
- Are chrom measurements archived?
** ****if not, they should be**
- If we can find chrom data, will go back and analyze yellow
- Overall summary:
- Schottky CAN give good chrom data, requires attention

- 17 Mar 2006