ATF2 optics, tuning method and tolerances of initial alignment, magnets, power supplies etc.

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ATF2 optics, tuning method and tolerances of
initial alignment, magnets, power supplies etc.
presented at the Third Mini-Workshop on Nano
Project at ATF KEK, May 30-31, 2005 http//acfahep
.kek.jp/subg/ir/nanoBPM/nano.project/third/third.h
tm selected pages will be used to illustrate
discussion of ATF2 project and collaboration that
happened on May 28-29.

• Andrei Seryi
• for the ATF2 optics design team

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ATF2 design goals.Learn to achieve
Optics Design of ATF2
Beam
(A) Small beam sizeObtain sy 35nmMaintain for
long time (B) Stabilization of beam center
Down to lt 2nm by nano-BPM Bunch-to-bunch
feedback of ILC-like train
PAC 05 paper
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Emphasis on the optimal layout
New final focus

• Extend diagnostics section

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Emphasis on the optimal layout
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Optimal layout

• Better optics
• Allow extension of diagnostics section
• about 13m of additional space is possible
• Better location
• Avoids many issue
• Give more suitable schedule for the international
  partners to find their contribution

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Coupling Correction and Emittance Diagnostics for
the ATF2 Extraction Line, Mark Woodley

• ideally
• correction section with 4 independent skew
  quadrupoles, followed by
• 2D (4 wire scanner) emittance measurement section
• optics for orthogonal control of the 4 coupling
  phases
• minimize ey once with each skew quadrupole
• in present ATF extraction line
• non-optimal optics in EXT straight section
• wire scanners and skew quads interspersed
• each wire scanner has x, y, and u/v (small
  angle, 10) wires

provide space for various experiments
Coupling Correction / Emittance Diagnostics
ATF Extraction Line
FONT
Compton / laserwire
ODR
nBPM
nBPM
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Ideal skew correction / e diagnostic section
SQ
SQ
SQ
SQ
WS
WS
WS
WS
x y
90 90
180 90
90 90
45 45
45 45
45 45
See http//www.slac.stanford.edu/cgi-wrap/getdoc/
slac-pub-8581.pdf
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Existing extraction line diagnostic section
WS
WS
WS
WS
WS
SQ
SQ
SQ
SQ
x y
L 11.43 m
5 8
13 20
30 36
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Ideal skew correction / e diagnostic section
for ATF2
Mark Woodley
SQ
SQ
SQ
SQ
1.2
1.2
1.7
1.7
1.1
1.1
1.3
1.1
0.9
0.9
0.9
0.7
1.3
WS
WS
WS
WS
WS
x y
32 48
51 21
32 58
58 32
L 20.58 m ?L 10 m
sWS gt 5 µ
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Tuning of ATF2 final focus

• Procedure for ATF FF would be based on methods
  implemented at SLC FFS and FFTB, developed
  further
• beam-based alignment using, e.g., shunting method
• verify first order optics with trajectories fits
• fix the phase advance between sextupoles
• set sextupoles to minimize chromaticity
• use global tuning correctors (knobs) to tune both
  the first-order and the nonlinear corrections
  using beam size measurements
• Extensive simulations of tuning for GLC/NLC and
  TESLA, but not always all possible sources of
  errors were included
• e.g. position errors included but not field
  strength, or vice versa
• Simulations of the ATF2 tuning procedure started
  by UK colleagues, James Jones et al.

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Tuning of NLC BDS, Yuri Nosochkov, Aug. 2002
Errors
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Analysis of Multipole and Position Tolerances for
the ATF2 Final Focus Line James Jones, ASTeC,
Daresbury Laboratory

• Analysed tolerances for all multipole components
  up to 20pole -gt will be used to optimize magnet
  designs
• Start analysis of position tolerances, including
  the effects of orbit correction and tuning knobs
  -gt jitter and static position tolerances

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Field Tolerances Individual Quads Multipole
Errors
Normal

• Tolerance for 10 beam growth due to the
  multipole field in an individual magnet, in units
  of
• Multipoles from
• Order 10 (20 pole) Red..
• Order 5 (10 pole) Light Green..
• Order 2 (Quad) Orange

Skew
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Position Tolerances effect of individual magnets
2 Increase in beam size OR 2 change in
positionbeamsize
2 Increase in beam size ONLY
Tolerance mm-1
Tolerance mm-1

• Global tolerances are be determined considering
  the combined effect of all elements, including
  capabilities of correction methods
• The global tolerances will need to match the
  goals A and B of ATF2
• 30 beam jitter for goal A and 10 (or a bit
  more?) beam size increase
• for goal B, rely on intra-train feedback to
  reduce jitter, or aim to reduction of beam jitter
  to 5 by providing better stability?

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Effect of all quads (jitter)

• Look at the results without the final doublet as
  these have the tightest tolerances
• More likely to be specially mounted and aligned
• Quadrupoles only (2 change of IP position)
• X-plane 14.5nm
• Y-plane 0.87nm
• Roll Angle 6.9?rad
• If we aim for 30, this scales to 12nm in
  verticalthe goal of 5 would corresponds to 2nm
• Feasibility of the latter, especially, need to be
  determined

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Position Tolerances ? with correction

• Assuming that the correction system will maintain
  the beam at the correct position, and looking
  only on beam size increase
• Quadrupoles only (2 increase)
• X-plane 585 nm
• Y-plane 197 nm
• Roll Angle 1.48 ?rad
• Start developing tuning knobs (?x, ?y, ?x waist ,
  ?y waist ) and orbit correction and include them
  into procedure (no coupling correction yet)
• Quadrupoles only (2 increase)
• X-plane 16 mm
• Y-plane 141 nm
• Roll Angle 3.5 ?rad
• Procedure, knobs, orbit corrections, is being
  further optimized ? final tolerances will be then
  determined

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Strategy for Commissioning the Beam chapter of
ATF2 proposal Frank Zimmermanns questionnaire
and some answers

• Are all magnets on movers? ? yes
• Are there dipole steering correctors? ? yes,
  several. Optimal locations TBD
• How many BPMs and are they tightly attached to
  magnets ? attached to all quads, sextupoles and
  bends
• Are there beam loss monitors and current monitors
  (toroids)? ? Yes. Location?
• Are all magnets on individual power supplies? ?
  Yes.
• Do we have conventional wire scanners and/or
  screens/profile monitors? ? Yes. Locations and
  how many?
• What other existing diagnostics may be suitable
  for the commissioning? ?
• Does the various diagnostics, including BPMs,
  read out bunch by bunch or single bunch or
  integrated over a train? ?

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Other minor optics improvements needed

• To make the design more construct-able
• change bends from sector bends to rectangular
• use 0.8m bens (as used in ATF) instead of 1m for
  better field stability and more space
• space near octupoles is too tight ? modify
• QM14 is the strongest quad, and is close to max
  field of BT quads ? reoptimize

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Summary

• Between now and BDIR workshop the team will
  concentrate on the optimal layout extended
  diagnostics optics, continue development of the
  tuning methods and finalize the numbers for
  tolerances