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John Arthur
Mirror effects [email protected]
June 23, 2006 1
Effects of LCLS X-Ray MirrorsJohn Arthur
Presenting work by Peter Stefan and Mike Pivovaroff
John Arthur
Mirror effects [email protected]
June 23, 2006 2
24mm offsetSiC 1.5mrad
SiC 1.5mrad
Offset mirrors in the FEE
FEL radiation reflected (>95%)
Background from high harmonics and Bremsstrahlung not reflected
Upstream of all LCLS experimentsWill remove high-energy background radiation
John Arthur
Mirror effects [email protected]
June 23, 2006 3
Hard x-ray mirrors
Soft x-ray mirrors
~14m
X-ray mirror locations in FEE
John Arthur
Mirror effects [email protected]
June 23, 2006 6
NEH
X-ray pump-probe
AMO SXR
soft x-ray line
hard x-ray line
Hutch 1 Hutch 2 Hutch 3
John Arthur
Mirror effects [email protected]
June 23, 2006 7
FEH
XPCS Coherent x-ray
imaging
High energy density science
Hutch 4Hutch 5 Hutch 6
John Arthur
Mirror effects [email protected]
June 23, 2006 8
Effects of Mirror Imperfections
Imperfections happen on all length scalesPower Spectral Density function (PSD) typically shows fractal power law behavior (with smaller errors at shorter wavelengths)
RoughnessErrors on x-ray wavelength scale
Cause scatter far out of direct beam
Slope errorsErrors on micron scale (larger than , but small compared to beam footprint)
Cause broadening of beam divergence
John Arthur
Mirror effects [email protected]
June 23, 2006 9
100 80 60 40 20 0 20 40 60 80 100
1.10
5
1.10
4
1.10
3
0.01
0.1
1
Ideal FEL Beam
Offset Mirror Output
: 0.15 , 0.5 Scattering and Divergence Increase nm microradian errors
( )Vertical Angle to Beam Axis microradian
( )FEL Intensity normalized to ideal beam
Beam profile downstream of imperfect mirror
Ideal beam
Beam distorted by mirror
Broadening due to slope error
Scatter due to roughness
John Arthur
Mirror effects [email protected]
June 23, 2006 10
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 effects [email protected]
June 23, 2006 11
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 effects [email protected]
June 23, 2006 12
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 100-200mm is needed.
John Arthur
Mirror effects [email protected]
June 23, 2006 13
0.4 0.2 0 0.2 0.4
0.4
0.2
0
0.2
0.4
1 microradian error0.5 microradian error0.1 microradian error
NEH1 FWHM Contours for 1.5 nm
Horizontal Axis (mm)
Vertical Axis (mm)
NEH Hutch 1
1.0 µrad Slope Errors
0.5 µrad Slope Errors
0.1 µradSlope ErrorsHorizontal Axis
_max _min _max _min _max _min
Effective Source Distance (m) 102.6 75.4 118.8 105.3 126.4 134.0FWHM Source Divergence (µrad) 10.53 7.68 8.80 4.99 8.17 3.73FWHM Beam Size in Hutch (µm) 1083.3 584.4 1048.6 530.8 1035.9 505.7
800eV 2keV 2keV 2keV800eV 800eV
Using short B4C mirrors at 15mrad incidence
z=117.1m (distance from end of undulator)
Vertical Axis _max _min
Source Distance (m) 127.2 138.2FWHM Source Size (µm) 81.59 76.03FWHM Source Divergence (µrad) 8.11 3.60FWHM Beam Size in Hutch (µm) 1034.8 503.1
800eV 2keV
John Arthur
Mirror effects [email protected]
June 23, 2006 14
0.6 0.4 0.2 0 0.2 0.4 0.6
0.6
0.4
0.2
0
0.2
0.4
0.6
1 microradian error0.5 microradian error0.1 microradian error
NEH2 FWHM Contours for 1.5 nm
Horizontal Axis (mm)
Vertical Axis (mm)
1.0 µrad Slope Errors
0.5 µrad Slope Errors
0.1 µradSlope ErrorsHorizontal Axis
_max _min _max _min _max _min
Effective Source Distance (m) 113.6 86.4 129.8 116.3 137.4 145.0FWHM Source Divergence (µrad) 10.53 7.68 8.80 4.99 8.17 3.73FWHM Beam Size in Hutch (µm) 1198.8 668.3 1145.1 585.1 1125.5 546.3
800eV 800eV 800eV2keV 2keV 2keV
NEH Hutch 2
Using short B4C mirrors at 15mrad incidence
z=128.1m
Vertical Axis _max _min
Source Distance (m) 138.2 149.2FWHM Source Size (µm) 81.59 76.03FWHM Source Divergence (µrad) 8.11 3.60FWHM Beam Size in Hutch (µm) 1123.8 542.3
800eV 2keV
John Arthur
Mirror effects [email protected]
June 23, 2006 15
0.2 0.1 0 0.1 0.2
0.2
0.1
0
0.1
0.2
1 microradian error0.5 microradian error0.1 microradian error
NEH3 FWHM Contours for 0.15 nm
Horizontal Axis (mm)
Vertical Axis (mm)
1.0 µrad Slope Errors
0.5 µrad Slope Errors
0.1 µradSlope ErrorsVertical Axis
_min _max _min _max _min _max
Effective Source Distance (m) 62.9 95.7 86.3 127.4 170.0 157.8FWHM Source Divergence (µrad) 6.77 7.57 3.52 4.90 1.30 3.66FWHM Beam Size in Hutch (µm) 430.6 728.8 310.0 629.1 228.4 582.8
8keV 8keV 8keV2keV 2keV 2keV
NEH Hutch 3
Using 1m SiC mirrors at 1.3mrad incidence
z=138.8m
Horizontal Axis _min _max
Source Distance (m) 193.1 159.9FWHM Source Size (µm) 59.94 76.03FWHM Source Divergence (µrad) 1.10 3.60FWHM Beam Size in Hutch (µm) 221.4 580.4
8keV 2keV
John Arthur
Mirror effects [email protected]
June 23, 2006 16
1 0.5 0 0.5 11
0.5
0
0.5
1
1 microradian error0.5 microradian error0.1 microradian error
FEH1 FWHM Contours for 0.15 nm
Horizontal Axis (mm)
Vertical Axis (mm)
1.0 µrad Slope Errors
0.5 µrad Slope Errors
0.1 µradSlope ErrorsVertical Axis
_min _max _min _max _min _max
Effective Source Distance (m) 289.0 321.8 312.4 353.5 396.0 383.9FWHM Source Divergence (µrad) 6.77 7.57 3.52 4.90 1.30 3.66FWHM Beam Size in Hutch (µm) 1958.9 2438.1 1102.3 1735.0 517.2 1407.6
8keV 8keV 8keV2keV 2keV 2keV
FEH Hutch 4
Using 1m SiC mirrors at 1.3mrad incidence
z=364.9m
Horizontal Axis _min _max
Source Distance (m) 419.2 386.0FWHM Source Size (µm) 59.94 76.03FWHM Source Divergence (µrad) 1.10 3.60FWHM Beam Size in Hutch (µm) 466.6 1391.0
8keV 2keV
John Arthur
Mirror effects [email protected]
June 23, 2006 17
1 0.5 0 0.5 1
1
0.5
0
0.5
1
1 microradian error0.5 microradian error0.1 microradian error
FEH2 FWHM Contours for 0.15 nm
Horizontal Axis (mm)
Vertical Axis (mm)
1.0 µrad Slope Errors
0.5 µrad Slope Errors
0.1 µradSlope ErrorsVertical Axis
_min _max _min _max _min _max
Effective Source Distance (m) 309.6 342.4 333.0 374.1 416.6 404.5FWHM Source Divergence (µrad) 6.77 7.57 3.52 4.90 1.30 3.66FWHM Beam Size in Hutch (µm) 2098.4 2594.0 1174.8 1835.9 543.7 1482.9
8keV 8keV 8keV2keV 2keV 2keV
FEH Hutch 5
Using 1m SiC mirrors at 1.3mrad incidence
z=385.5m
Horizontal Axis _min _max
Source Distance (m) 439.8 404.6FWHM Source Size (µm) 59.94 76.03FWHM Source Divergence (µrad) 1.10 3.60FWHM Beam Size in Hutch (µm) 489.2 1465.0
8keV 2keV
John Arthur
Mirror effects [email protected]
June 23, 2006 18
1 0.5 0 0.5 1
1
0.5
0
0.5
1
1 microradian error0.5 microradian error0.1 microradian error
FEH3 FWHM Contours for 0.15 nm
Horizontal Axis (mm)
Vertical Axis (mm)
1.0 µrad Slope Errors
0.5 µrad Slope Errors
0.1 µradSlope ErrorsVertical Axis
_min _max _min _max _min _max
Effective Source Distance (m) 330.2 363.0 353.6 394.7 437.3 425.1FWHM Source Divergence (µrad) 6.77 7.57 3.52 4.90 1.30 3.66FWHM Beam Size in Hutch (µm) 2237.9 2749.9 1247.3 1936.9 570.3 1558.2
8keV 8keV 8keV2keV 2keV 2keV
FEH Hutch 6
Using 1m SiC mirrors at 1.3mrad incidence
z= 406.1m
Horizontal Axis _min _max
Source Distance (m) 460.4 427.2FWHM Source Size (µm) 59.94 76.03FWHM Source Divergence (µrad) 1.10 3.60FWHM Beam Size in Hutch (µm) 511.8 1539.0
8keV 2keV
