Dynamic Dispersion Bump Dispersion Unsuppressor

1
MI Beam Loss upon Acceleration
9.8GeV/c
Slow loss
5E11/div
Fast loss 10 ms
9.28 GeV/c
Start of Ramp
11BLMALM634
2
Dynamic Dispersion Bump(Dispersion Un-suppressor)

• Provide a well contained limiting momentum
  aperture to catch all un-captured beam at the
  beginning of the ramp.
• Apply a dispersion time bump to MI30 zero
  dispersion straight section only on selected
  cycles (slip-stacking) to generate dispersion at
  302 (and 308).
• Use fixed collimator at 302 (radial inside) as
  the limiting momentum aperture to catch the
  un-captured beam at the start of acceleration
• Utilize local dipole time bump to assure limiting
  aperture
• Straight section optics are not effected during
  pbar transfers (i.e. zero dispersion/ nominal
  betas)
• Bump is turned on after injection (for catching
  un captured beam)
• Collapse bump to return to nominal optics after
  10 GeV.

3
Dynamic Dispersion Bump II(Dispersion
Un-suppressor)

• Concept could be expanded to potentially clean up
  uncaptured beam during the slip stacking process
  itself
• Turn dispersion un-suppressor (and dipole time
  bumps) at injection if a beta wave allows (need
  to keep matched to MI-8)
• Install collimator at 308 (radial outside) and
  use dipole bump to move higher momentum beam onto
  collimator
• Could be expanded even further to collimate
  vertically (at 301)
• Vertical beta function increases from 60 to 80
  meters at 301 during dynamic dispersion bump.

4
Some numbers

• Energy spread during slip stacking
• Df /- 1400 hz -gt Dp /- 26 MeV bucket
  separation
• Bucket height /- 7 Mev
• Total energy spread Dp /- 33 MeV
• Dp/p (max)
  /- 0.37
• sT 4.47
  mm for b 60m and e20 p
• sL 0.65 mm
  with sp/p 0.33E-3
• How fast does un-captured beam move radially
  inward? At 6 GeV/sec -gt .06 MeV/turn
  20G/s -gt .2Mev/turn
• -gt Dp/p 0.0006
  0.0022
• -gt Dx 13 mm/turn ( D of 2 m)
  45 mm/turn
• So, un-captured beam is scraped in 10 ms once it
  contacts the aperture (i.e. 66 MeV/.06MeV/turn
  1100 turns)

5
How to create Dispersion bump

• Utilize trim coils in IQC/IQD dispersion
  suppressor on either side of MI30 to create a
  symmetric matched non-zero dispersion wave in
  MI30
• MI dispersion suppressors not matched
• For meter dispersions in MI30 phase advance
  across straight section increases by .25 to.4
• Use Main Quad bus to compensate
• Install trim quads inside MI30 to create phase
  trombone to compensate (keep it local)
• Install phase trombone in MI60
• For smaller dispersion bump
• MI main quad bus is sufficient

6
Current Layout MI30
ECOOL (Between 305 307)
QXR
QXR
K304
Q301
Q229
Q314
Q302
Q305
Q309
Q308
7
Potential MI30 Layout
Fixed collimator (not motorized)
MI trim quad
TC1
TC2
V
H
TC3
TC4
H
TC5
QXR
QXR
K304
Q301
Q229
Q314
Q302
Q305
Q309
Q308
ECOOL
8
Trim Coils and Trim Quads

• Main Injector Trim quads
• Integrated strength 0.0269 T-m/m/A
• Assume max current 10A -gt Gdl .27 T (K1L 0.01)
• Trim Coils
• 16 turns 14 sq.
• IQC R 2.4 ohms L 20 mH
• IQD R 2.8 ohms L 23.4 mH
• Integrated strength 0.0585 T-m/m/A
• Assume max strength 10A -gt Gdl .59 T (K1L
  0.02)
• Voltage required to ramp to max in 50 ms
• V 24 v IR drop from cable induced
  voltage from main coil

9
Nominal MI30 Lattice functions
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Nominal Ring Lattice Functions
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Matched -1.2m solution
12
Circuit Currents for -1.2 m Solution
13
Matched -.6 m solution
14
Delta Beta/Beta for 3 Solutions
15
Revised Delta Beta/Beta for 2 Solutions
Plot Hor db/b at Hor locations and visa
versa. Dashed lines indicate dispersion
suppressor and straight
16
Conclusions / Recommendations

• Solutions for local Dynamic Dispersion insert in
  MI30 for collimating un-captured beam during
  acceleration
• Small dispersion (lt ½ m) done with only IQC/IQD
  trim coils
• Larger dispersion (gt ½ m) require trim quads in
  MI30 straight section
• Concept expanded to provide transverse and
  momentum collimation in same straight section
• Preliminary investigation has included the impact
  on RR counterwaves, QXR, and Recycler
  injection/extraction kicker. This needs further
  investigation
• Need to determine collimator design
  (single/double stage)
• Need to investigate impact on losses in ECOOL
  section
• Need to model proposed layout using collimation
  model (Sasha)
• Need to model geometry of collimators (Nikolai)
• Trim coils look to be sufficient (need to look at
  rms power)
• Need to determine max current for MQTM trim quads
  for linear excitation (and rms current)
• Need to investigate cost/time for required power
  supplies
• Since tunnel time is at a premium, I would
  recommend pulling cables ASAP to IQC/IQD on
  either side of straight section. These may be
  used for testing dynamic dispersion concept and
  lattice function measurements.