Using the method of

1
Using the method of running orbit bump to
determine aperture limitations in the
DebuncherV. Nagaslaev

1. Running orbit bump method
2. Transformation to present scheme
3. Application in the Debuncher
4. Lessons

2
Beam based alignment

• 1. Centering movable devices
• Orbit correction with local bumps
• Paint aperture
• Running bumps

3
Method of Running bump
1 bump orbit
2 bumps
phase y3 depends on A and B can
probe aperture in arbitrary location
One can have correctors current change in time so
that orbit has constant amplitude and phase of
the orbit wave is running.
,
If phase advance between 2 correctors is p/2,
4
Method of Running bump - 2

• Would be possible to determine aperture and
  limiting location,
• but 2Q ambiguity (19)!
• but unable to reach aperture

5
Grouping correctors

• What if we try to make groups of correctors
  acting together?

It would have enhanced the reach of method, but
it doesnt work, of coarse
6
Heating the beam

• We could preheat the beam to a definite size so
  that the sum of
• size and wave amplitude would reach the aperture.
• Heating is made by applying a noise generator
  signal on horizontal
• or vertical damper. Then beam is scraped to
  required size.
• Assuming that we know the size of the beam and
  the orbit position
• everywhere at each time, we could measure the
  narrowest aperture
• and determine its location.
• Beam size must be stable throughout this
  measurement.

7
Heating the beam, Diffusion
Diffusion in 5 minutes 10 of beam diffuses
through the 10p mark
This makes impossible painting aperture with
the running bump.
8
New (present) approach

• Heat the beam and let running orbit run
  continuously
• auto scraping
• minimum time after scraping
• diffusion works for us
• Watch loss monitors
• sensitive to low losses
• pattern of LM activity points to the location
  of losses
• Constraints

Phase advance must be very close to p/2
y2y1p/2d
Integer part of phase advance should be 0 Tune
must be gt 0.5
Between correctors
movie
9
Trim currents and beam losses, 3 cycles
10
Loss monitors

• Populate the ring nonuniformly
• less in arcs and more straights
• more significant in straights
• Large uncertainty in sensitivity
• signal/noise varies
• response to single particle
• geometrical acceptance
• catch factor to remote showers
• Mostly recalibrated during November shutdown
• in data analysis normalization to background
  level is made
• Scalers in these studies set up to continuous mode

11
Testing the method
To test the method we ran it with horizontal and
vertical scrapers.
12
Test with vertical scraper, sector 30
time, a.u.
13
Test with vertical scraper, LM profile
snapshot of losses at step 59 and 111 LM names in
the order, not spaced backsplashing
14
Horizontal aperture search, losses in sector 60
15
Horizontal aperture search, LM profile
16
Horizontal aperture search

• Using corrector pair H403-H501 -gt 6.8p bump
• H405-H403 -gt 1.0p bump
• Running wave pointed to ESEP region
• Bump 34 (3 steps IN) applied, aperture
  increased 26.0p -gt 30.3 p
• centering cooling kicker tank-304
  30.3 -gt 32.3
• At stacking bump 34 extraction adjustment
• DebAp2 aperture increased 23.4 p -gt 29.0 p,
  
• stacking rate increased 10

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Horizontal aperture search, losses in sector 60
after correction
18
Horizontal aperture search, LM profile after
correction
19
Vertical aperture scans
Correctors H403-H401 1.3p bump
H405-H403 1.3p bump work in progress, no
much progress so far
20
Vertical scan, losses vs time
time, a.u.
21
Vertical scan, LM profile at time step 73
22
Lessons learned so far

• Method works even with very low achievable kicks
• Helped to increase horizontal aperture
• Constraint need a pair of correctors separated
  by p/2, tunegt0.5
• Loss monitors around the ring do help to choose
  between spot candidates,
• but losses pattern should be interpreted
  cautiously
• Method only points to location, real work is to
  fix the orbit