atf2 optics … 1 3 rd mini-workshop on nano project at atf atf2 optics, tuning method and...

ATF2 optics … 1 3rd Mini-Workshop on Nano Project at ATF

ATF2 optics, tuning method and tolerances of initial

alignment, magnets, power supplies etc.

Andrei Seryi

for the ATF2 optics design team


Optics Design of ATF2

Beam

ATF2 design & goals.Learn to achieve:(A) Small beam size

Obtain y ~ 35nmMaintain 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:


Emphasis on the optimal layout

New final focus

• Extend diagnostics section


Emphasis on the optimal layout


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


nBPMnBPM

FONT Compton / laserwireODR

ATF Extraction Line

Coupling Correction /Emittance Diagnostics

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 εy 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


“Ideal” skew correction / ε diagnostic sectionSQ SQ SQ SQ

WS WS WS WS

90°90°

180°90°

90°90°

45°45°

45°45°

45°45°

– x– y

See http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-8581.pdf


– x– y

5°8°

13°20°

30°36°

SQ SQ SQ SQ

WS WS WS WS WS

L = 11.43 m

Existing extraction line diagnostic section


SQ SQ SQ SQ

L = 20.58 mΔL ≈ 10 m

WS WSWS WS WS

32°48°

51°21°

32°58°

58°32°

– x– y

1.1 1.11.3 1.10.9 0.9 0.9 0.7 1.31.2 1.2 1.7 1.7

σWS > 5 μ

“Ideal” skew correction / ε diagnostic section for ATF2Mark Woodley


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.


Tuning of NLC BDS, Yuri Nosochkov, Aug. 2002

Errors:


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


Field Tolerances – Individual Quads Multipole Errors

Skew

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

n

n

n x

B

BK

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?

2% Increase in beam size OR 2% change in position[beamsize] 2% Increase in beam size ONLY

Tol

eran

ce [m

-1]

Tol

eran

ce [m

-1]

Position Tolerances – effect of individual magnets


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: 6.9rad

• 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


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 m• Y-plane: 141 nm• Roll Angle: 3.5 rad

• Procedure, knobs, orbit corrections, is being further optimized final tolerances will be then determined


“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?


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


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 … 1 3 rd mini-workshop on nano project at atf atf2 optics, tuning method and...

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