John Arthur X-Ray Optics October 12, 2004 X-Ray Prototype Optics Specifications John Arthur

X-Ray Optics October 12, 2004 The Project scope includes  facilities for production and transport of a bright, high-current electron beam  an undulator system in which the electron beam will generate the x-ray beam  facilities for transport, diagnostics and optical manipulation of the x-ray beam  endstations and related facilities for x-ray experiments  conventional facilities for the accelerator systems and x-ray experiments  a central lab office building to house support staff and researchers From the LCLS Global Requirements document: This talk will elaborate on the specifications for the LCLS x-ray optics and diagnostics

John Arthur X-Ray Optics October 12, 2004 The X-ray Optics

John Arthur X-Ray Optics October 12, 2004 Functions of the x-ray optics Confinement (masks, slits, local apertures) Intensity attenuation (gas attenuator, solid attenuator) Focusing (K-B mirror) Spectral filter (mirror low-pass filter, monochromator) Beam direction (flipper mirrors) Temporal filter (pulse split/delay)

John Arthur X-Ray Optics October 12, 2004 High peak power (fluence) poses a challenge for x-ray optics Response of material to ultra-high power x-ray pulse is untested LLNL codes can describe all aspects of the response EXCEPT initial conversion of x-ray energy into hot electrons. Uncertainty due only to lack of understanding of non-linear response We have good arguments that the non-linear response will be negligible Therefore, we will use linear absorption cross sections with confidence LLNL will do precise calculations (assuming linear cross sections) as part of optics design Until those calculations are done, use conservative approximation based on known melting points of materials

John Arthur X-Ray Optics October 12, 2004 NEH FEH FEE LLNL Expected LCLS fluence compared with melt fluence for various materials Approximation assumes FEL pulse energy instantly deposited in atoms within absorption volume (using linear absorption cross section). If resulting energy/atom much less than melt energy/atom, then the material will not be damaged.

John Arthur X-Ray Optics October 12, 2004 Some proposed solutions to the peak power problem Grazing-incidence slits Graded-density absorber Low-z materials (Be, B 4 C, C) Grazing incidence Gas attenuator Distance from source

John Arthur X-Ray Optics October 12, 2004 Basic specifications for slits and attenuators Slit aperture range2 x 4  beam 800 eV Slit precision1 µm Attenuator rangeup to 10 4 at any energy eV Attenuator precision1% of attenuation, steps 3/10/100/10 3 /10 4

John Arthur X-Ray Optics October 12, 2004 X-ray focusing (DESCOPED) K-B focusing mirrors Produce high flux density Useful energy range eV Focus size< 1 µm Efficiency>10%

John Arthur X-Ray Optics October 12, 2004 X-ray mirrors for LCLS (DESCOPED) Double-mirror low-pass filter Energy low-pass filter Beam redirection Low-pass mirror critical energyvariable 1200 eV eV Mirror mechanical stabilitybeam jitter < 10% of beam size

John Arthur X-Ray Optics October 12, 2004 X-ray monochromators Energy bandpass filter Energy range800 eV eV Bandpass< 2 x10 -4 Rapid scan range10%

John Arthur X-Ray Optics October 12, 2004 X-ray pulse split and delay Provides precise time delay between pulses Pulse split/delay using thin Si crystals Energy 8000, eV Delay range0-200 ps

John Arthur X-Ray Optics October 12, 2004 X-ray diagnostics are required for characterization of the FEL and spontaneous radiation, as means of assessing SASE performance The X-ray Diagnostics

John Arthur X-Ray Optics October 12, 2004 Specifications for the x-ray diagnostics Position of beam centroid5% of beam size Beam transverse dimensions10% of beam size Beam divergence10% of divergence Photon energy0.02% of energy Photon energy spread20% of energy spread

John Arthur X-Ray Optics October 12, 2004 Summary The XTOD group will provide facilities for transporting the LCLS x-ray beam, for measuring the beam characteristics, and for manipulating the characteristics in controlled ways X-ray optical elements will aperture, attenuate, focus, and monochromate the x-rays Some of the desired optical components are not in the current project scope A suite of x-ray diagnostics will allow characterization of SASE performance