John Arthur Mirror June 23, Effects of LCLS X-Ray Mirrors John Arthur Presenting work by Peter Stefan and Mike Pivovaroff

John Arthur Mirror June 23, mm offset SiC 1.5mrad Offset mirrors in the FEE FEL radiation reflected (>95%) Background from high harmonics and Bremsstrahlung not reflected Upstream of all LCLS experiments Will remove high-energy background radiation

John Arthur Mirror June 23, Hard x-ray mirrors Soft x-ray mirrors ~14m X-ray mirror locations in FEE

John Arthur Mirror June 23,

John Arthur Mirror June 23,

John Arthur Mirror June 23, NEH X-ray pump- probe AMO SXR soft x-ray line hard x-ray line Hutch 1Hutch 2Hutch 3

John Arthur Mirror June 23, FEH XPCS Coherent x-ray imaging High energy density science Hutch 4 Hutch 5 Hutch 6

John Arthur Mirror June 23, Effects of Mirror Imperfections Imperfections happen on all length scales Power Spectral Density function (PSD) typically shows fractal power law behavior (with smaller errors at shorter wavelengths) Roughness Errors on x-ray wavelength scale Cause scatter far out of direct beam Slope errors Errors on micron scale (larger than, but small compared to beam footprint) Cause broadening of beam divergence

John Arthur Mirror June 23, Beam profile downstream of imperfect mirror Ideal beam Beam distorted by mirror Broadening due to slope error Scatter due to roughness

John Arthur Mirror June 23, For the LCLS, mirror roughness should not be a big problem. Realistic values of roughness will remove <5% of the beam intensity from the central spot. Slope errors will broaden the beam and reduce its brightness. This is our major concern.

John Arthur Mirror June 23, We considered three cases for slope error: rms = 1 µrad, 0.5µrad, and 0.1µrad 1 µrad mirrors are readily available from several vendors 0.5 µrad mirrors are probably available, for a price 0.1 µrad mirrors may not be available today, but will be within a few years The state of the art for 1m-length mirrors:

John Arthur Mirror June 23, Note: shorter mirrors are better (World record: 0.01µrad rms, for a 100mm-long mirror) The 1m length of the LCLS hard x-ray mirrors is driven by the desire to reflect 24keV radiation, and the desire to accept all of the beam at 2 keV, and still not hit the end regions of the mirror. Also note: the soft x-ray mirrors are short. They operate at a steeper angle, so a length of only mm is needed.

John Arthur Mirror June 23, NEH Hutch 1 800eV 2keV 800eV Using short B 4 C mirrors at 15mrad incidence z=117.1m (distance from end of undulator) 800eV 2keV

John Arthur Mirror June 23, eV 2keV NEH Hutch 2 Using short B 4 C mirrors at 15mrad incidence z=128.1m 800eV 2keV

John Arthur Mirror June 23, keV 2keV NEH Hutch 3 Using 1m SiC mirrors at 1.3mrad incidence z=138.8m 8keV 2keV

John Arthur Mirror June 23, keV 2keV FEH Hutch 4 Using 1m SiC mirrors at 1.3mrad incidence z=364.9m 8keV 2keV

John Arthur Mirror June 23, keV 2keV FEH Hutch 5 Using 1m SiC mirrors at 1.3mrad incidence z=385.5m 8keV 2keV

John Arthur Mirror June 23, keV 2keV FEH Hutch 6 Using 1m SiC mirrors at 1.3mrad incidence z= 406.1m 8keV 2keV