Impact of beam motion on soft xray beamlines

Impact of beam motion on soft x-ray beamlines Darío Arena, Steve Hulbert, Ruben R. NSLS – II Stability Workshop 19 April 2007

NSLS-II CDR SXR Concept Experimental Station Side view, single beam mode Beam Chopper Plane Mirror Exit Slit Plane Grating EPU Cylindrical Collimating Mirror EPU Side view, canted beam mode, fast switchable Elliptical cylinder KB refocusing mirrors

Vertical Source Motion: Effect on Resolution Ultra-High Resolution (UHR, 3600 l / mm) High Flux (HF, 400 l / mm) UHR 1000 e. V HF 1000 e. V (300 l/mm) UHR 200 e. V HF 200 e. V (300 l/mm) Beamline Resolution 11 me. V 114 me. V 21 me. V Energy Shift 4 mm beam motion 0. 89 me. V 11 me. V 0. 08 me. V 1 me. V

Horizontal Beam Motion: Large Demag Helps • NSLS-II: small divergence (~15 mrad vert. , ~20 mrad hor. @1000 e. V) Element Position From Source M 1 28 m M 2 ~29 m Grating ~30 m Exit Slit 50 m M 3 51. 8 m M 4 52. 3 m Sample 53. 3 m • CDR concept: no horizontal focusing until after exit slit (M 3) • Effective horizontal demagnification: ~50: 1 • Sample position: spot ~ 4 mm (v) x 8 mm (h) • 0. 5 mm beam motion (h) 0. 01 mm beam motion on sample • Beam spot insensitive to vertical motion (imaging exit slit)

Beam Divergence Motion • Beamline design: operation 100 e. V up to ~2400 e. V • hv = 100 e. V: s. V’ ~ 40 mrad, s. H’ ~ 45 mrad • 10% values: ~ 4 mrad (vert. ), ~ 4. 5 mrad (hor. ) • hv = 2000 e. V: s. V’ ~ 10 mrad, s. H’ ~ 20 mrad • 10% values: ~ 1 mrad (vert. ), ~ 2 mrad (hor. ) • Dk ~ k * sin q ; Dk / k ~ sin q • Contribution to uncertainty of wavevector from beam angular motion is on order few parts in 106

Conclusions • Spectroscopy and diffraction experiments in the soft x-ray range are very forgiving • 10% criterion is sufficient for spectroscopy and scattering • Imaging as another story (c. f. Chris Jacobsen’s talk)