ATF2 as a test bench for CLIC BDS tuning, also R. Toms and A. Latina - - PowerPoint PPT Presentation

ATF2 as a test bench for CLIC BDS tuning, also

• R. Tomás and A. Latina (CERN)

Thanks to P. Bambade and G. White ATF2 project meeting 2007

Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.1/12

Contents

• Motivation:
• Beam based alignment in the CLIC BDS
• FFS?
• ATF2 case
• Tuning approach
• Simulation ingredients
• Results from ATF2 tuning simulations.

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Aligning the CLIC collimation section

20 30 40 50 60 70 80 90 100 20 40 60 80 100 εy [nm] quadrupole index test beam 98% nominal energy, ω1/ω0=1e5, σbpm=0.1 µm, misalignment 10 µm 1-to-1 correction, no multipoles DFS correction, no multipoles 1-to-1 correction, multipoles DFS correction, multipoles nominal

5% emittance growth after aligning only the collima- tion section.

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Aligning the full BDS?

20 30 40 50 60 70 80 90 100 20 40 60 80 100 εy [nm] quadrupole index test beam 98% nominal energy, ω1/ω0=1e5, σbpm=0.1 µm, misalignment 10 µm 1-to-1 correction, no multipoles DFS correction, no multipoles 1-to-1 correction, multipoles DFS correction, multipoles nominal

Does not work. The FFS corrupts the correction in the collimation section.

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Looking into the CLIC FFS

• 0.4
• 0.3
• 0.2
• 0.1

0.1 0.2 0.98 0.985 0.99 0.995 1 Vertical BPM reading [µm] Relative Energy (E/E0) 3 FFS BPM readings (with and without radiation)

Large error due to radiation Apparent linear and non-linear vertical dispersion

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The ATF2 FFS

• 1.4
• 1.2
• 1
• 0.8
• 0.6
• 0.4
• 0.2
• 0.02
• 0.015
• 0.01
• 0.005

0.005 Vertical BPM reading [µm] dp/p 3 ATF2 FFS BPMs bpm1 QF1 QD0

Apparent linear and non-linear vertical dispersion due to the transverse particle distribution.

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Tuning approach

A 0-th order tuning algorithm based on the Simplex:

• Observables: σx and σy at IP.
• Variables: Magnet strengths, x, y and tilt

displacements. First test via ATF2 simulations:

• Code: PLACET-Octave
• Ingredients: realistic errors but no ground motion

(yet)

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Simulation ingredients: errors

• H & V misalignments with σ = 30µm.
• Transverse roll with σ = 30µrad.
• Relative strength error with σ = 10−4.
• Measurement error of σy, σ=1nm.

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Initial σy for 150 seeds

2 4 6 8 10 12 14 16 0.5 1 1.5 2 2.5 3 3.5 4 Counts Initial σy [µm]

Up to 4µm of initial σy.

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Number of Simplex iterations

2 4 6 8 10 12 500 1000 1500 2000 2500 3000 3500 Counts Number of iterations

Below 4000 iterations required (without ground mo- tion).

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Final σy

5 10 15 20 25 30 35 36 37 38 39 40 41 42 43 44 Counts Final σy [nm]

Final σy between 37 and 44nm.

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Summary and such

• ATF2 tuning experience is extremely valuable for

CLIC.

• A 0-th order tuning algorithm has been simulated

with ATF2 based on the Simplex.

• Initial σy < 4µm gets below 44nm in less than

4000 iterations

• Consistent with Glenn’s previous results
• Ground motion to be included in future studies
• “Realism” studies from SLAC colleagues to be
• bserved (even more dramatic for CLIC!).

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