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Experimental work at the Australian Synchrotron relevant to CLIC DR design

Experimental work at the Australian Synchrotron relevant to CLIC DR design. Mark Boland , Rohan Dowd, Eugene Tan Australian Synchrotron Kent Wootton, Roger Rassool The University of Melbourne. Talk Summary. Coordinate System Storage Ring Lattice Calibration Vertical Emittance Minimisation

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Experimental work at the Australian Synchrotron relevant to CLIC DR design

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  1. Experimental work at the Australian Synchrotron relevant to CLIC DR design Mark Boland, Rohan Dowd, Eugene Tan Australian Synchrotron Kent Wootton, Roger Rassool The University of Melbourne

  2. Talk Summary • Coordinate System • Storage Ring Lattice Calibration • Vertical Emittance Minimisation • Emittance Measurements • Future Plans/Ideas CLIC Workshop 2014 - M.J. Boland

  3. The Australian Coordinate System CLIC Workshop 2014 - M.J. Boland

  4. $38M New Building Programme Completed Medical Imaging Beamline User Accommodation Offices BBQ Synchrotron Light Source Storage National Synchrotron Science Centre Engineering Workshop Metrology Laboratory RF Laboratory CLIC Workshop 2014 - M.J. Boland

  5. 2012 New National Centre for Synchrotron Science CLIC Workshop 2014 - M.J. Boland

  6. User Beam Available since 2007 CLIC Workshop 2014 - M.J. Boland

  7. Australian Synchrotron Storage Ring • 3 GeV e, BDA, 14 cells, 216 m • Qx,y=13.29, 5.21, x=16 nm rad, nominal 1% coupling for increased lifetime J. W. Boldeman and D. Einfeld, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 521 (2-3), 306 - 317 (2004). CLIC Workshop 2014 - M.J. Boland

  8. Low Emittance Magnet Alignment • Alignment error: 26 μm Quadrupoles, 18 μm Dipoles • Intrinsic Fiducial and assembly error: 16 μm (Quad), 6 μm (Dipole) • Full ring realignment conducted ~2 every years. • Current ‘natural’ emittance coupling = 0.059% - Very Low! CLIC Workshop 2014 - M.J. Boland

  9. Low Emittance Lattice Calibration with LOCO Input Data: • BPM noise • Dispersion • Model Response Matrix Optics Correction: • Measure response matrix • Fit for example quadrupole strengths • Apply, re-measure, iterate CLIC Workshop 2014 - M.J. Boland

  10. Gradient Dipole Measured CLIC Workshop 2014 - M.J. Boland

  11. Gradient Dipole Model CLIC Workshop 2014 - M.J. Boland

  12. Beam Energy Measurement for Dipole Characterisation • Describes adiabatic spin evolution • For a storage ring, simplify to • By comparison with the cyclotron frequency Thomas – BMT equation CLIC Workshop 2014 - M.J. Boland

  13. Resonant Spin Depolarisation CLIC Workshop 2014 - M.J. Boland

  14. High Efficiency Beam Loss Monitor System CLIC Workshop 2014 - M.J. Boland

  15. Measured Polarisation time CLIC Workshop 2014 - M.J. Boland

  16. Spin Tune Frequency Measurement • 17.81977(4) MHz • 3.013408(8) GeV CLIC Workshop 2014 - M.J. Boland

  17. Measured Momentum Compaction Factor CLIC Workshop 2014 - M.J. Boland

  18. Momentum compaction factor Conclusion: • split-bends model is an excellent representation of the constructed gradient dipole bending magnets. • We have a very good calibrated model, as a result we have very good control over the lattice very well. • Details in: K. P. Wootton, M. J. Boland, et. al., Physical Review Special Topics-Accelerators and Beams 16 (7) (2013). CLIC Workshop 2014 - M.J. Boland

  19. Quantum Limit of Vertical Emittance • Opening angle of synchrotron radiation puts a limit on the smallest possible vertical emittance • Australian Synchrotron storage ring quantum limit ey = 0.5 pm • QLOVE Prize – case of French Champagne? q=1/g photon p CLIC Workshop 2014 - M.J. Boland

  20. Vertical emittance minimisation method • Take orbit response matrix and dispersion data. • Analyse with LOCO, fit skew quad components to every multipole in the ring. Weigh vertical dispersion highly in fit. • Use LOCO calibrated lattice to calculate equilibrium beam envelope in AT, using Ohmi method (K.Ohmi et al. Phys.Rev.E. Vol.49. (1994)). Calculate emittance ratio from this. • Feed calculated emittance ratio into minimisation algorithm which adjusts the skew quadrupole currents in the model to minimise the ratio (or set it to a desired value) • Apply skew quadrupole settings onto machine and re-do LOCO analysis. Calculate emittance ratio from calibrated lattice. R. Dowd, M. Boland, et. al., Phys. Rev. ST Accel. Beams 14 (1), 012804 (2011). CLIC Workshop 2014 - M.J. Boland

  21. Beam Based Magnet Alignment • Coupling terms rise from quadrupole rolls and sextupole vertical offsets. • Our Alignment surveys seemed to be progressively making our coupling worse! • Alignment survey positioning doesn’t tell you what is happening at the magnetic centre. • Can you get better accuracy using the beam? • Orbit response analysis using LOCO should allow you to find the sextupole offsets. (E.g. V. Sajaev, A Xiao, IPAC10) • Need to take care with the LOCO fitting. Simultaneous measurements found not to work due to ‘smearing’ of fitted coupling. • Separate, family by family measurements taken. CLIC Workshop 2014 - M.J. Boland

  22. Sextupole offsets • Shunt each sextupole magnet family to different strengths and take a response matrix at each point • Perform LOCO analysis and fit skew quadrupole terms to each sextupole. • Gradient of skew field vs sextupole field gives vertical offset. • Shim Magnets to reduce offsets CLIC Workshop 2014 - M.J. Boland

  23. Emittance coupling – Quadrupole rolls • Turn off Sextupoles and perform LOCO analysis. • Fit skew quadrupole terms to each Quadrupole only • Roll Girders by the amount indicated in the LOCO analysis and re-measure. • Method was found to be accurate to ±0.05 mrad. Rolls now reduced to < 0.2 mrad. Another iteration possible CLIC Workshop 2014 - M.J. Boland

  24. Cross Check Measurements Lifetime vs coupling Tune crossing X-ray pinhole beam profile Beam profile tilt CLIC Workshop 2014 - M.J. Boland

  25. Skew magnet re-positioning. • Ran simulation of using all 56 skew quadrupole coils. • One magnet seen to have large effect on total coupling • Power supply was swapped from adjacent skew quad to power this coil. Simulated minimised emittance result dropped from 0.8 to 0.3 pm. • 4 New skew quad power supplies are currently being installed CLIC Workshop 2014 - M.J. Boland

  26. Touschek Lifetime Analysis Results Current minimal εy is now ~0.5pm, quantum limit is 0.35 pm. Now in quantum dominated region and we still have some options for reducing further. CLIC Workshop 2014 - M.J. Boland

  27. Summary • Main issues: • Beam based alignment – LOCO accuracy is sensitive to BPM density and phase advance. Not suitable for simultaneous measurements, but done carefully, accuracy can be quite high. • Direct measurements are still very challenging, lifetime measurements track well with model estimates.. • Further developments • Measurements using εx = 7 nm lattice (~ 30% improvement) • Re-shim some sextupoles. • Incorporate new skew quads • Calibrate skew quads. CLIC Workshop 2014 - M.J. Boland

  28. 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. CLIC Workshop 2014 - M.J. Boland

  29. Cross Check with X-ray Pinhole Camera CLIC Workshop 2014 - M.J. Boland

  30. 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 CLIC Workshop 2014 - M.J. Boland

  31. Spectral Measurement Results CLIC Workshop 2014 - M.J. Boland

  32. 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 CLIC Workshop 2014 - M.J. Boland

  33. 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 CLIC Workshop 2014 - M.J. Boland

  34. Polarisation Simulations • Improved sensitivity with selection of only vertical photon polarisation • Acknowledgement of Spring-8 Takano work S. Takano, EMIT’ 97, KEK Proceedings 97-20 (1997) CLIC Workshop 2014 - M.J. Boland

  35. Emittance Measurement • Not sensitive enough for sub pm emittance • Planning polarisation measurements • Seeking interested collaborators (with 2D x-ray detectors?) CLIC Workshop 2014 - M.J. Boland

  36. Future Plans • Beta function manipulation to make measurements easier • Optical measurements: ODB2, interferometer, depth of field effects • X-ray measurements: undulator, strip detectors, two slit measurement • IBS measurements • Damping from 4 T SC Wiggler • Multiband Instability Monitor: optical and RF pickups • Pinger kicker magnet for non-linear optics studies CLIC Workshop 2014 - M.J. Boland

  37. Australian Collaboration for Accelerator Science

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