High-Speed PIXE A spatially resolved PIXE setup at the 6 MV Tandem accelerator Josef Buchriegler J.v. Borany, D. Hanf, F. Munnik, S. Nowak, A. Renno, O. Scharf, R. Ziegenrücker SLcam® User Workshop – 16. Jan. 2014

Outline PIXE fundamentals & Motivation Experimental setup Data evaluation & First results Prospects & Challenges

PIXE + Fundamentals of PIXE: Particle Induced X-ray Emission Photon Particle Electrons + e.g. Mg Particles: charged ions (mostly protons or He-ions with 2 – 4 MeV) Ionisation cross-section σ: probability for an inner-shell ionisation Fluorescence yield ω: probability for a X-ray (or Auger-electron) emission Photons: typical energies from 1 – 30 keV (K- and L-lines)

PIXE Fundamentals of PIXE: X-Ray detection & data evaluation Detector: cooled semi-conductor crystal  Si(Li) or Ge (energy dependent efficiency) Spectrum: detected X-ray photons as a function of energy Elements in spectrum: X-ray lines: needs model for X-ray lines (shape) and intensity ratios Background: subtraction by using a filtering method or background-model Pileup: caused by (almost) simultaneous detection of two photons Si escapes: interaction of photons with the detector crystal  considering all these points  fit X-ray intensities to deduce elemental composition

PIXE Fundamentals of PIXE: classical micro-beam setup Object 50x50 μm2 Aperture 1x1 mm2 Lens Target plane High-energy proton beam (3 µA) proton beam on sample: 0.5 nA Focus beam and scan over sample big detector as close as possible  new approach: position sensitive detector High energy proton beam (<1 µA) Target plane

Motivation High-Speed PIXE Why a new PIXE analysis method should be developed? Requirements defined by geologists: fast method to find trace elements (e.g. rare earth elements) lateral resolved informations large throughput big samples for grain size determination intergrowth analysis, etc. to avoid: additional processing steps in mining industry (braking, milling, floating)  save energy & time Solution: novel combination of PIXE as analytical method position sensitive detector  pixel-detector poly-capillary X-ray optics fast data acquisition system established evaluation software  GeoPIXE High-Speed PIXE

Experimental setup High-Speed PIXE setup data acquisition scanning system 3–4 MeV protons SLcam® beam diagnostic chamber sample analysis chamber

pixel detector + poly-capillary optics  SLcam© Experimental setup How to get lateral & spectral resolved images? Particle beam induces divergent X-rays in sample Capillaries are collimating and guiding the “right” photons towards the pixels pixel detector + poly-capillary optics  SLcam©

Experimental setup SLcam®: X-ray Colour Camera 1:1 optics 6:1 optics 1.2 mm Ø 19 mm 82 mm 12 cm Pixels 264 x 264 = 69696 Pixels size 48 x 48 µm² Framerate 400 / 1000 Hz Sensitive thickness 450 µm Quantum efficiency >95% @ 3-10 keV >30% @ 20 keV Window 50 µm Be 1:1 optics 6:1 optics Lateral resolution 50 µm 10 µm Picture size 12 x 12 mm² 1.2 x 1.2 mm² Distance to sample < 10 mm 0.8 mm

Data evaluation SLcam Imager: real-time data analysis ~5 cm

Data evaluation Limits of SLcam Imager Columbite

Data evaluation GeoPIXE: established evaluation software for geological samples Quantitative evaluation: detector properties sample properties (matrix) corrections for the optics X-ray line model background model pileup correction  Deconvolution of spectra

First results Lateral resolution: lateral resolution ~ 67 µm Measurement of known structure: 67 µm Cu-stripes on Si-wafer distances: 200/135/67 µm intensity distribution along green line Gauss-fits at several lines lateral resolution ~ 67 µm (Rayleigh criterion)

First results Trace elements: Geological sample: Cassiterite measurement time: ~45 Min. beam current: ~700 nA (3 MeV)

Prospects & Challenges Beam alignment homogeneous illumination of samples proton yield on samples Automation movement of samples inside analysis chamber integration of optical microscope logging of experimental parameters logging of radiation doses data management Calibration detector efficiency influence of optics windowless operation Data evaluation full integration of GeoPIXE:  concentration maps in real-time

Thank you for your Attention Acknowledgement Johannes von Borany¹ Daniel Hanf¹ Frans Munnik¹ Thank you for your Attention Stanislaw Nowak³ Axel Renno² Oliver Scharf³ René Ziegenrücker² ¹ Helmholtz-Zentrum Dresden-Rossendorf, Ion Beam Center (HZDR) ² Helmholtz-Institut Freiberg für Ressourcentechnologie (HIF) ³ Institute for Scientific Instruments (IfG)