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National Synchrotron Light Source II
Damping Wiggler Beamline: XAS Preliminary Design Summary
Paul NorthrupJanuary 16th, 2008
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Overall Mission• To provide a versatile and highly productive facility for
hard X-ray Absorption Spectroscopy for a wide range of scientific disciplines: • Catalysis and energy science• Environmental science and low-temperature geochemistry• Life science and biology• Nanomaterials and condensed matter research• Earth and high pressure science
• To pursue and apply cutting-edge XAS capabilities and techniques appropriate to the advanced quality of the NSLS-II source
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Preliminary Design• Careful consideration of:
• Community input • User and scientific needs and new opportunities• Technical feasibility• Overall mission of NSLS-II
• Through: • Workshops -- local and national• Beamlines’ staff and representatives of scientific communities• NSLS UEC• White papers
• Technical, EFAC, and DOE reviews
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Beamline Requirements, Specifications
• Source requirements: • Broad spectrum, high flux, non-coherent source• Source stability (running in top-off mode):
– position within 10% of source size, – vertical angle within 1 rad (for monochromatic energy stability)
• Specifications: • Energy range: ~5.5-50 keV, provisions to use up to 90 keV• Tunable spot size from 0.2 x 0.2 mm to 5 x 55 mm• Microbeam (1 x 1 micron) available• Standard (10-4) and high (10-5) energy resolution modes available• Controlled sample environment (air-sensitive or hazardous samples)• Beamline stability scan-to-scan: position on sample within 5 microns,
energy calibration within 0.05 eV
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Beamline Design -- Overview
Top view:
Side view:
First Optic Enclosure (FOE) containing beamline optics and white-beam components
Bulk XAS (with three sample positions)
Shield wall
2 Experimental Hutches in line
Microbeam XAS Beam
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Insertion Device
• Damping Wiggler, length 3.5 meters, in high-beta straight section
• Future upgrade: two canted 3.5m wigglers independently serving microbeam and bulk endstations
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Damping Wiggler Characteristics
Flux: Brightness:
Highest hard X-ray flux at Highest brightness of broad- NSLS-II spectrum sources
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Damping Wiggler Heat Load (3.5m)
• Wiggler output 32 kW, 4 kW reaches beamline at max acceptance of 0.15 mrad (v) x 1.0 mrad (h) defined by optics
• Challenging to maintain broad energy range, stability• “Divide and conquer” approach (absorbs:)
• front end mask 25 kW• white-beam apertures 3-7 kW (pass up to 4 kW)• filters and attenuators 1-2.5 kW• white-beam mirror 0-2.5 kW• monochromator first crystal 100-700 W• monochromator second crystal (scatter)
• Preliminary thermal analyses show that this can be done• Heat load on sample may be significant (>20 mW)
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White Beam Components
• Retractable attenuators, sequentially added for higher energy experiments (water-cooled, carbon)
• White-beam mirror • 1.5 meter, Si (or GlidCop) substrate, water-cooled• Two “stripes” (bare Si and Pt-coated) available• Three positions: 2.0 or 3.15 mrad, or removed from beam
– Thus 5 configurations to cover required energy range• Vertical collimation and harmonic rejection
Beam
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White Beam Components
• High Heatload Monochromator: • LN2 cooled first and second crystals• Side-by-side sets: Si(111) and Si(311) [or Si(333) instead]
Beam
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Beamline Optics
• High energy resolution (10-5 or better) monochromator• In series with high-heatload monochromator • Passes beam when not in use• No LN2 cooling required, high precision mechanism• Several crystal types being considered (less restrictions on
material)• Synchronization with primary monochromator is required
Beam
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Beam Conditioning Optics
Focusing mirror (~2:1) • Two toroidal “stripes” match Mirror 1• Reflects in opposite sense to Mirror 1• Initial ray tracing calculations:
spot size 0.2 x 0.2 mm at sample
Beam
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Endstation 2: Bulk XAS
• Acceptance up to 0.15 x 1.0 mrad
• Spot size ~0.2x0.2 mm up to 5x55 mm
• Continuous-scan or step-scan modes of data collection• Time-resolved (minutes)
studies• 3 sample positions
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Endstation 2: Bulk XAS
Sample position 1: Classic benchtop XAS
• Transmission, fluorescence and grazing-incidence
geometries• In-situ measurements:
electrochemical cells, gas and solution flow-through cells
• Heater, cryostat and LN2 cooling• Standard and high-resolution
(energy selective) detectors• Detector for powder XRD pattern
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Endstation 2: Bulk XAS
2: Controlled environment XAS• Multi-use enclosure:
• Glove box: controlled atmosphere• Containment/fume hood for
hazardous samples• Multi-element detector • Low-concentration samples • Hazardous, nano, or radioactive
materials
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Endstation 2: Bulk XAS
3: Space for move-in apparatus• Large-volume high-pressure
or catalytic cells• High-field magnet• Available control and
data channels, utilities, etc.• ~2 x 3 m
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Endstation 1: Microbeam XAS
• Conventional K-B mirror optics• Focused spot ~1 micron• Microbeam and single-crystal XAS• Diamond anvil cell high-P XAS• Multi-use enclosure• Multi-element detector • XRD detector shared with Endstation 2
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1.E+10
1.E+11
1.E+12
1.E+13
1.E+14
1.E+15
0 10000 20000 30000 40000 50000
Estimated flux (delivered to sample at monochromator bandpass) 5.5 keV
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Estimated Flux: High Energy Resolution
1.E+10
1.E+11
1.E+12
1.E+13
1.E+14
0 10000 20000 30000 40000
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Summary: Initial Project Scope• Two endstations included, one control station• Single source and one set of optics serving both
endstations• Endstation 2 hutch can be accessed for set-up while
Endstation 1 is in use; but not vice versa• Accommodations (space, component design) made for
future canting of source• Heatload R&D
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Potential Upgrade/Build-out Path
• Add second canted wiggler source and beamline optics to provide independent beam for each endstation
• Addition of mirror in front end to divert low-energy portion of overlapped fans into a third station for high-flux bulk 2-6 keV applications
• Complementary bulk/micro XAS beamline at adjacent dipole for 1-5 keV applications
• Net potential: core cluster of XAS endstations covering 1-90 keV energy range, bulk and microbeam capability
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