Vertical Emittance Measurement with a Vertical Undulator

Vertical Emittance Measurement with a Vertical Undulator

Mark BolandAustralian SynchrotronUniversity of Melbourne

On behalf of

Kent WoottonUniversity of Melbourne

Oxford, 10 July 2013Low Emittance Ring Workshop

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Abstract• Method developed to measure the vertical emittance in a storage

ring using a vertical undulator. (K. P. Wootton, M. J. Boland, et al. (2012). "Observation of Picometer Vertical Emittance

with a Vertical Undulator." Physical Review Letters 109(19): 194801.)

• Measure the ratio of the odd and even harmonic peaks.• Observed ultra low vertical emittance on SLSA storage ring.• Characterised the undulator radiation and got good agreement

with calculated radiation using measured magnetic field maps.• Improved sensitivity by scanning the e-beam and collect statistics• Planned improvements by measuring the photon polarisation.

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Overview of the Method• APPLE II undulator on the Soft X-ray

beamline at the Australian Synchrotron(B. C. Cowie, A. Tadich, and L. Thomsen, AIP Conf. Proc.

1234, 307 (2010).)

• Phase the magnets to vertical polarisation

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Spectral Measurement Results

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Cross Check with X-ray Pinhole Camera

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Sensitivity to Pinhole Size and Beam Decay

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Undulator Characterisation

• Blade scans to observe vertical distribution

• Asymmetry observe between the top and bottom peak

• Comparison with SPECTRA simulations of 2D radiation

• SPECTRA tracks of e-beam through measured magnetic field also produce assymetry

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New Approach

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• Time averaging• Normalise to beam current

due to 1 hour lifetime at minimised emittance

• Beam bumps instead of blade scans

• Electron beam Orbit bumps through the undulator

• Parallel position bump and vertical angle bumps

Angle scan of the e-beam through the undulator for three different harmonics (red odd, blue even, black odd)

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Measurement of Latest Emittance Minimisation

• Not sensitive enough to sub pm emittance

• Need to separate p and s modes in the photon beam

• 2D x-ray pixel detector may also help resolve ultra low emttances

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Polarisation Simulations

• Improved sensitivity with selection of only vertical photon polarisation

• Acknowledgement of Spring-8 Takano work

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S. Takano, EMIT’ 97, KEK Proceedings 97-20 (1997)

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Conclusions/further work

• Not sensitive enough for sub pm emittance• Planning polarisation measurements• Seeking interested collaborators (with 2D x-ray detectors?)

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