PS2 Orbit Correction

Wolfgang BartmannPS2 Meeting, 16-Nov 07

Outline

• Error Assignment• Sensitivity of the orbit to different errors• Placement of monitors and correctors• Results for the orbit before/after correction• Summary• Further steps

Apr 21, 2023 PS2 Orbit Correction 2

Error Assignment

• MisalignmentsDipoles: 0.3 mm shift and 0.3 mrad

angle for all axesQuadrupoles: 0.2 mm shift and 0.3 mrad

angle for all axes

• Field ErrorsDipoles ΔBL/Bρ : 0.510-3

All errors are gaussian distributed with a cut-off at 2σ

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Sensitivity to different errorsError Aver. maximum

displacement in [mm]

Hor. Vert.

Relative dipole field error ΔBL/Bρ 0.87 10-3 TGAUSS(2) 15.0 -

0.60 10-3 TGAUSS(2) 10.3 -

0.50 10-3 TGAUSS(2) 8.5 -

Transverse quadrupole shift DX, DY 0.300 mm TGAUSS(2) 15.8 11.7

0.285 mm TGAUSS(2) 15.0 11.2

0.200 mm TGAUSS(2) 10.5 7.8

Longitudinal dipole shift DS 0.300 mm TGAUSS(2) 0.5 -

Tilt of dipoles about s-axis DPSI 0.300 mrad TGAUSS(2) 0.1 4.0

Calculated with a sample of 50 machines; Qx,Qy = 14.21 (µ = 88.2°)

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Monitors and Correctors

• Monitors measuring in both planes placed close to the quadrupoles (116 monitors)

• Horizontal/Vertical Correctors placed at QFs/QDs (58 hor./58 vert.)

• Phase advance between elements approx. 90°

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Placement of monitors and correctors

µ=90 °

Results before/after correctionBefore correction After correction

Horizontal Vertical Horizontal Vertical

Average of max. displacement [mm] 17.5 12.3 1.4 0.9

Max. absolute displacement [mm] 42.0 29.1 10.8 8.7

Average of r.m.s displacement [mm] 7.0 4.9 0.6 0.4

• Calculated with a sample of 500 machines

• Qx,Qy = 14.21 (µ = 88.2°)

• Corrector kicks are below 1 mrad

• All BPMs and Correctors are used

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Orbit before correction, hor.500 machines

Apr 21, 2023 8PS2 Orbit Correction

Orbit after correction, hor.500 machines

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Orbit before correction, vert.500 machines

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Orbit after correction, vert.500 machines

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Summary• Orbit distortion caused by magnet misalignments and field errors is

comparable to other machines

• Sensitivity of the orbit to different errors shows:– dipole field errors and transverse quadrupole shifts give the main error contributions for

the horizontal plane– the transverse quadrupole shift and the tilt of the dipoles about the longitudinal axis

dominate the error for the vertical plane

• Correction of the uncorrected orbit with xmax up to 2 cm works well (factor 10 for uncorr/corr.) and gives a corrected xmax of below 2 mm; above 2 cm uncorr. orbit, the correction gives a factor of 3-4

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Further steps to be studied:• Position of monitors and correctors in the dispersion suppressor and in

the middle of the arc needs to be improved

• Orbit correction for different tunes

• Effect of the failure of monitors and correctors on the correction

• Corrector strengths for different energies

• Local orbit corrections at septa and sextupoles

Apr 21, 2023 PS2 Orbit Correction 13