Motivation for Top-Up:A beamline perspective
David PatersonTop-Up Workshop
4 good reasons for topup
1.stability
2.resolution
3.speed
4.flexibilityCoboltIron
I0 incident flux Potassium
Energy range4.0 to 25 keV
ΔE/E =10-4 Si(111) and Si(311) KB mirror Microprobe
1 µm spatial resolution FZP Nanoprobe
60 nm spatial resolution –laser interferometry Measurements
X-ray fluorescence mapping (XRF), X-ray absorption spectra (XAS, µXANES, µEXAFS)
Elements accessibleAluminium & heavier by XRF Calcium & heavier by XAS fluorescence
InformationElemental mapping, chemical state mapping, ppm sensitivity
X-ray fluorescence microscopy beamline
Pt spectrum located in a tumour cellHambley et al, U Sydney
1. Stability
• Beamline optics
• constant heat load on critical optics can ensure maximum stability
• Micro and nano-focus optics
• depend on stable illumination especially angular
Conceptual design D. Paterson, et al., AIP Conf. Proc. 879, 864 (2007).B. Lai, et al., AIP Conf. Proc. 879, 1313 (2007).I. McNulty, et al., Rev. Sci. Instrum. 67, 9 CD-ROM (1996).
Beamline optics: horizontal diffracting DCM
B. Lai, et al., AIP Conf. Proc. 879, 1313 (2007).
DCM stability for XANES spectroscopy
Monochromator reproducibility
Tandem scanning of undulator and horizontal DCM
1st derivative peak centroid
~ 0.05 eV
Data courtesy of
Andrew Berry, Imperial College
X-ray Fluorescence Microprobe
OSA
scan stage
sample
zone plate
APD or segmented detector
fluorescence detector
Fresnel Zone Plate (FZP) lenses: ~60-200 nm focus
Kirkpatrick-Baez (KB) mirrors: 1-10 µm focus (achromatic)
Vortex: Single element silicon-drift detector
Maia: planar silicon 384 detector array (CSIRO-BNL)
Stage: Xradia precision XYZ
~10 nm resolution (FZP mode) with laser- interferometry encoders and feedback
Transmission detector:
APD or BNL segmented detector
SXRF elemental
imaging
Phase contrast
imaging
X-ray beam 4-25 keV undulator source, monochromatic, Si (111) E/E ~ 1-2 10-4
KB mirror microprobe with Maia-96 prototype
Beam
Prototype Maia 96 detector enclosure
Be entrance window
KB mirror pair
Sample stage (XY)
Microscope
Sample holder
Rat brain sections 1 micron pixels, 50 hours
Cobolt
Calcium
ZincIron
I0 incident flux Potassium
Cerebral malaria in rat brain
ZincCoboltIron
CalciumPotassium
Decay in beam current requires accurate normalisation to quantify concentrations
2. Resolution
• Beam stability
• Microprobe optics require beam stability especially angular stability from source
• Improve emmitance
• Low beta function see 4. Flexibility
Resolution test of nanoprobe with 100 nm Δr zone plate
Cr test pattern100 nmPeriod
Scan over 16 hours duration
2 µm
Fluorescence detector: geometry for fluorescence detectionTraditional geometry•Detector perpendicular to incident beam
•sample @ 75-45°
•Minimises elastic scatter detection
•Limits solid angle, lateral sample size and scan range
Annular geometry•Maximises solid angle, sample @ 90°
•No constraint on lateral sample size and scan range
Horizontal sample scan
detectordetector
Solid angleSolid angle
detectordetector
Transmission Transmission DPC DPC
detectordetector
P. Siddons, et al., AIP Conf. Proc., 705 (953) (2004). C. Ryan, et al., Nucl. Instr. Meth. B, 260, 1 (2007).
Maia detector
Cooling/vacuumconnections
Optimum sample position• 1 mm from front face• 10 mm from detector wafer• Peltier cooled to -35 ºC
Electrical/optical dataconnections
Beryllium window
Mountingpoints
Incident beam
Imaging with Maia-96 prototype
Sr = Red Fe = Green Rb = Blue
Imaging gold
Rb = RedAu = GreenFe = Blue
8000 X 8000 pixels, 1.25 µm, 1.6 msec dwell
X-ray fluorescence map of ilmenite concentrate
8000×3600 1.25 µm pixels collected in 6 hours (0.75 msec/pixel)
Elemental map: Red = thorium, Green = niobium, Blue = titaniumBlue = titanium.
Display range:Th ~ 800 ppmNb ~ 1500 ppm
Mouse brain section8 Megapixel imagein 10 hours
10 keV incidentIron=RedManganese=GreenZinc=Blue
1 mm
Wednesday morning Damian Myers “X-ray Fluorescence Microscopy of brain slices....” abs#097
Biological samples – tissue sections
Importance of high definition imagesPotentially unlimited field of view of scanning microscopyStatistical threshold accumulation strategyExplore heterogeneityEnables 3D studies…….
As Fe Br
Image area is 8.0 x 7.2 mm2, 6400 x 5760 pixels, each 1.25 µm (cropped from 12 x 10 mm2, 9600 x 8000 pixels), 0.6 msec/pixel dwell
Br Au Fe9600 x 8000 binned to 4800 x 4000
Gold particles
Ultrafast x-ray fluorescence enablesHigh definition 2D maps
Statistical accumulation strategy
But a 2D 64 megapixel image can be divided into 3D scan
400 X 400 X 400 projectionsFluorescence tomography
Or
1000 X 1000 X 64 energy stepsmicro-XANES imaging.
Martin de Jonge“Fast fluorescence tomography of Cyclotella at 200 nm resolution” abs#294
Fluorescence tomography
Martin de Jonge, et al., abs#294
3. Speed
Scanning microscopy is coherent flux hungryNo loss of time during fillsHigher average currentNo settling time required after fills
Fluorescence tomography
4. Flexibility
• To try unusual operation modes with potentially poor lifetime
• Low emittance e.g. low beta function
• Timing modes
• Special beam size
Undulator tuning curves Tuning Curves for in vacuum 22mm, 90 period, 6 mm minimum gap undulator with 0.83 T max field. Harmonics to 15 are shown. (achieved 0.97 T!)
Brightness
5 keV on 3rd harmonic
8.7x1018 ph/s/0.1%BW/mrad2/mm2
25 keV on 9th harmonic
4.6 x1015 ph/s/0.1%BW/mrad2/mm2.
Curves assume zero phase errors but include allowance of 0.1% for energy spread
Phase errors on undulator specified at <2.5 degrees
22 mm undulator90 periods6 mm gap0.83T max field
1
3
5
7
9
Specified > 90% of theoretical flux at peak 7th harmonic, > 85% of theoretical flux in the peak at the 9th harmonic.
Horizontal diffraction geometry
Polarization losses?Pi polarization
Acceptance of optics
5.0 keV 50% -> 80%10 keV 91% -> 99%
Top Related