Vertical Emittance Measurements using a Vertical Undulator K

Vertical Emittance Measurements using a Vertical Undulator K. P. Wootton, G. N. Taylor, R. P. Rassool Uni. Melbourne M. J. Boland, B. C. C. Cowie, R. Dowd, Y. -R. E. Tan Australian Synchrotron Y. Papaphilippou CERN

Overview • • • Measurement of vertical emittance Undulator spectra Photon beam brilliance Vertical undulators Measurements of undulator spectra Future directions Wootton – CLIC DR Meeting – 13/09/2012 2

Vertical emittance • Collider damping rings and Super B-factory storage rings • demand 0. 5 -2. 0 pm rad Collective effects lead to growth – IBS, electron cloud • Storage ring light sources as test accelerators – SLS, ATF 2, CESR, ASLS, Diamond, … (ALS? ) • Need measurements of vertical emittance Wootton – CLIC DR Meeting – 13/09/2012 3

Indirect measurement • Orbit response matrix • • fitting Touschek lifetime – Eigen as opposed to projected emittances Beam ellipse tilt (bending magnet) Dowd PRSTAB 14, 012804 (2011) Wootton – CLIC DR Meeting – 13/09/2012 4

Direct measurement Laser wire scanner • Scanning laser waist through electron beam – Inverse Compton gamma rays • Shintake monitor – Interference pattern narrower than laser waist Boogert PRSTAB 13, 122801 (2010) Shintake NIMA 311, 453 -464 (1992) Wootton – CLIC DR Meeting – 13/09/2012 5

Direct measurement Vertical emittance monitors • Andersson, NIMA 591, 437 -446 2008 Masaki DIPAC 01, PS 17 Flanagan PAC 09, TH 5 RFP 048 Nakamura PAC 01, TPAH 307 Scheidt, DIPAC 05 CTWM 01 Wootton – CLIC DR Meeting – 13/09/2012 6

Undulator diagnostics • Focus on odd (useful!) • harmonics Horizontal undulators – Imaging – Projection – Absolute spectral brilliance (pinhole flux) Moreno JSR, 19 179 -84 (2012) • Energy spread, dispersion, ‘large’ emittance Hahn JSR 4, 1 -5 (1997) Wootton – CLIC DR Meeting – 13/09/2012 7

Undulator beam projection Undulator 25 periods 75 mm period K = 3. 85 Pinhole 50 x 50 um 15 m distance Wootton – CLIC DR Meeting – 13/09/2012 8

Undulator projection measurements Horizontal undulator Undulator 25 periods 75 mm period K = 3. 85 Vertical undulator Wootton – CLIC DR Meeting – 13/09/2012 9

Photon beam brilliance • Horizontal undulator – No contrast • Vertical undulator – Even harmonics Wootton – CLIC DR Meeting – 13/09/2012 10

Photon beam brilliance Wootton – CLIC DR Meeting – 13/09/2012 11

Fitting spectra • Convolve beam emittance • with undulation ‘It is evident that the second-harmonic brightness is proportional to the beam emittance …’ Dattoli PRE 52(6) 6809 -17 (1995) • I add to this: … the emittance in the direction of undulations – How do we measure photon beam brilliance? Dattoli PRE 52(6) 6809 -17 (1995) Wootton – CLIC DR Meeting – 13/09/2012 12

Advanced Planar Polarised Light Emitter-II Modes of operation Wootton – CLIC DR Meeting – 13/09/2012 13

SXR undulator beamline Wootton – CLIC DR Meeting – 13/09/2012 14

SXR undulator beamline • APPLE-II undulator • White beam slits first optical element • All focussing, monochromator downstream Slits Monochromator Wootton – CLIC DR Meeting – 13/09/2012 Photodiode 15

Detector • Measuring vertical • emittance with one large pixel! Beamline optics – – Grating monochromator Au-coated mirrors Energy-defining slit Photodiode (Ga. As. P, Si) • Au-coated mirrors – Transmission varies with photon energy Wootton – CLIC DR Meeting – 13/09/2012 16

Photodiode choice • Early experiments – Hamamatsu Ga. As. P • Ratio of peaks • Absorption edges – Silicon photodiode • Keithley picoammeter – Spans many orders of magnitude in current Krumrey, Tegeler (1992) Rev Sci Instrum 63 (1), p. 797 -801 Wootton – CLIC DR Meeting – 13/09/2012 17

Undulator projection measurements Horizontal undulator Vertical undulator K = 3. 85 E = 3 Ge. V 75 mm period Wootton – CLIC DR Meeting – 13/09/2012 18

Measured undulator spectrum • Measured • Modelled Wootton – CLIC DR Meeting – 13/09/2012 19

Emittance envelopes • Wootton – CLIC DR Meeting – 13/09/2012 20

Where to? • Fixed pinhole diameter • SOLEIL Diag. On (fixed • • • energy 367. 5 e. V) SPring-8 BL 45 XU (vertical IVU) Higher undulator k Lower beam energy (IBS studies) Moreno JSR, 19 179 -84 (2012) – Same minimum gap, higher undulator k Wootton – CLIC DR Meeting – 13/09/2012 21

Summary • Wootton – CLIC DR Meeting – 13/09/2012 22