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%