Transcript Optimization of betatron collimation

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.htm
selected pages will be used to illustrate discussion of ATF2 project and
collaboration that happened on May 28-29.
ATF2 optics, tuning method and
tolerances of initial alignment,
magnets, power supplies etc.
Andrei Seryi
for the ATF2 optics design team
ATF2 optics …
1
3rd Mini-Workshop on Nano Project at ATF
ATF2 design & goals.
Learn to achieve:
Optics Design of ATF2
Beam
(A) Small beam size
Obtain sy ~ 35nm
Maintain for long time
(B) Stabilization of beam center
Down to < 2nm by nano-BPM
Bunch-to-bunch feedback of
ILC-like train
PAC 05 paper:
ATF2 optics …
2
3rd Mini-Workshop on Nano Project at ATF
Emphasis on the optimal layout
New final focus
• Extend diagnostics section
ATF2 optics …
3
3rd Mini-Workshop on Nano Project at ATF
Emphasis on the optimal layout
ATF2 optics …
4
3rd Mini-Workshop on Nano Project at ATF
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
ATF2 optics …
5
3rd Mini-Workshop on Nano Project at ATF
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
+ provide space for
minimize εy once with each skew quadrupole
various experiments
• 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
Coupling Correction /
Emittance Diagnostics
FONT
ODR
nBPM
ATF2 optics …
ATF Extraction Line
Compton / laserwire
nBPM
6
3rd Mini-Workshop on Nano Project at ATF
“Ideal” skew correction / ε diagnostic section
SQ
SQ
SQ
SQ
WS
90°
90°
180°
90°
90°
90°
45°
45°
WS
45°
45°
WS
WS
45°
45°
–x
–y
See http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-8581.pdf
ATF2 optics …
7
3rd Mini-Workshop on Nano Project at ATF
Existing extraction line diagnostic section
WS
WS
SQ
SQ
SQ
WS
WS
SQ
L = 11.43 m
5°
8°
ATF2 optics …
WS
13°
20°
–x
–y
30°
36°
8
3rd Mini-Workshop on Nano Project at ATF
“Ideal” skew correction / ε diagnostic section for ATF2
Mark Woodley
SQ
SQ
SQ
SQ
1.2
1.1
1.3
1.1
0.9
0.9
0.9
0.7
1.3
1.1
WS
32°
48°
L = 20.58 m
ΔL ≈ 10 m
1.2
WS
1.7
WS
51°
21°
1.7
WS
32°
58°
WS
58°
32°
–x
–y
σWS > 5 μ
ATF2 optics …
9
3rd Mini-Workshop on Nano Project at ATF
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.
ATF2 optics …
10
3rd Mini-Workshop on Nano Project at ATF
Tuning of NLC BDS, Yuri Nosochkov, Aug. 2002
Errors:
ATF2 optics …
11
3rd Mini-Workshop on Nano Project at ATF
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 -> will be used to optimize magnet designs
• Start analysis of position tolerances, including the effects of
orbit correction and tuning knobs -> jitter and static position
tolerances
ATF2 optics …
12
3rd Mini-Workshop on Nano Project at ATF
Field Tolerances – Individual Quads Multipole Errors
Normal
• Tolerance for 10% beam
growth due to the multipole
field in an individual magnet,
in units of
1 nB
Kn 
B x n
• Multipoles from:
– Order 10 (20 pole) : Red..
– Order 5 (10 pole): Light Green..
– Order 2 (Quad): Orange
Skew
ATF2 optics …
13
3rd Mini-Workshop on Nano Project at ATF
2% Increase in beam size OR 2% change in position[beamsize]
2% Increase in beam size ONLY
Tolerance [mm-1]
Tolerance [mm-1]
Position Tolerances – effect of individual magnets
• 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?
ATF2 optics …
14
3rd Mini-Workshop on Nano Project at ATF
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: 6.9mrad
• If we aim for 30%, this scales to ~12nm in vertical
the goal of 5% would corresponds to ~2nm
– Feasibility of the latter, especially, need to be determined
ATF2 optics …
15
3rd Mini-Workshop on Nano Project at ATF
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 mrad
• 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 mrad
• Procedure, knobs, orbit corrections, is being further optimized 
final tolerances will be then determined
ATF2 optics …
16
3rd Mini-Workshop on Nano Project at ATF
“Strategy for Commissioning the Beam” chapter of ATF2 proposal
Frank Zimmermann’s 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? 
ATF2 optics …
17
3rd Mini-Workshop on Nano Project at ATF
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
ATF2 optics …
18
3rd Mini-Workshop on Nano Project at ATF
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
ATF2 optics …
19
3rd Mini-Workshop on Nano Project at ATF