Motivation for Top-Up:
A beamline perspective
David Paterson
Top-Up Workshop
4 good reasons for topup
1.stability
2.resolution
3.speed
4.flexibility
I0 incident flux
Potassium
Iron
Cobolt
X-ray fluorescence microscopy beamline
 Energy range
4.0 to 25 keV
ΔE/E =10-4 Si(111) and Si(311)
 KB mirror Microprobe
1 µm spatial resolution
 FZP Nanoprobe
Pt spectrum located in a
60 nm spatial resolution –laser interferometry
tumour cell
Hambley et al, U Sydney
 Measurements
X-ray fluorescence mapping (XRF),
X-ray absorption spectra (XAS, µXANES, µEXAFS)
 Elements accessible
Aluminium & heavier by XRF
Calcium & heavier by XAS fluorescence
 Information
Elemental mapping, chemical state mapping, ppm sensitivity
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
Fresnel Zone Plate (FZP) lenses:
~60-200 nm focus
Transmission detector:
Kirkpatrick-Baez (KB) mirrors:
APD or BNL segmented detector
1-10 µm focus (achromatic)
OSA
sample
APD or segmented
detector
X-ray beam
4-25 keV
undulator source,
monochromatic,
Si (111)
DE/E ~ 1-2 10-4
zone plate
fluorescence detector
scan stage
Vortex: Single element
silicon-drift detector
Stage: Xradia precision XYZ
Maia: planar silicon 384
~10 nm resolution (FZP mode) with laserinterferometry encoders and feedback
detector array (CSIRO-BNL)
KB mirror microprobe with Maia-96 prototype
Prototype Maia 96
detector enclosure
Be entrance
window
KB mirror pair
Microscope
Sample
holder
Sample stage (XY)
Rat brain sections 1 micron pixels, 50 hours
I0 incident flux
Potassium
Calcium
Iron
Cobolt
Zinc
Cerebral malaria in rat brain
Decay in beam
current
requires
accurate
normalisation
to quantify
concentrations Iron
Potassium
Calcium
Cobolt
Zinc
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 pattern
100 nm
Period
Scan over
16 hours
duration
2 µm
Fluorescence detector: geometry for fluorescence detection
Traditional geometry
P. Siddons, et al., AIP Conf. Proc., 705 (953) (2004).
C. Ryan, et al., Nucl. Instr. Meth. B, 260, 1 (2007).
Annular geometry
•Maximises solid angle, sample @ 90°
•No constraint on lateral sample size and scan range
Horizontal sample scan
detector
•Detector perpendicular to incident beam
•sample @ 75-45°
•Minimises elastic scatter detection
•Limits solid angle, lateral sample size and scan range
Transmission
DPC
detector
Solid angle
detector
Maia detector
Mounting
points
Electrical/
optical data
connections
Cooling/
vacuum
connections
Optimum sample position
• 1 mm from front face
• 10 mm from detector wafer
• Peltier cooled to -35 ºC
Beryllium window
Sr = Red
Fe = Green
Rb = Blue
Imaging with Maia-96 prototype
Imaging gold
Rb = Red
Au = Green
Fe = 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)
Display range:
Th ~ 800 ppm
Nb ~ 1500 ppm
Elemental map: Red = thorium, Green = niobium, Blue = titanium.
Biological samples – tissue sections
Mouse brain section
8 Megapixel image
in 10 hours
10 keV incident
Iron=Red
Manganese=Green
Zinc=Blue
Wednesday morning
Damian Myers
“X-ray Fluorescence Microscopy of
brain slices....” abs#097
1 mm
Importance of high definition images
Potentially unlimited field of view
of scanning microscopy
Statistical threshold accumulation
strategy
Explore heterogeneity
Enables 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
Gold particles
Br Au Fe
9600 x 8000 binned to 4800 x 4000
Ultrafast x-ray fluorescence enables
High definition 2D maps
Statistical accumulation strategy
But a 2D 64 megapixel image
can be divided into 3D scan
400 X 400 X 400 projections
Fluorescence tomography
Or
1000 X 1000 X 64 energy steps
micro-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 hungry
No loss of time during fills
Higher average current
No 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
1
Brightness
3
5
22 mm
undulator
90 periods
6 mm gap
0.83T max field
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!)
9
5 keV on 3rd harmonic
8.7x1018
ph/s/0.1%BW/mrad2/mm2
7
25 keV on 9th harmonic
4.6 x1015
ph/s/0.1%BW/mrad2/mm2.
Specified > 90% of theoretical flux at peak 7th harmonic,
> 85% of theoretical flux in the peak at the 9th harmonic.
Curves assume zero phase errors but
include allowance of 0.1% for energy
spread
Phase errors on undulator specified at
<2.5 degrees
Horizontal diffraction geometry
Polarization losses?
Pi polarization
Acceptance of optics
5.0 keV 50% -> 80%
10 keV 91% -> 99%