EDXRF-Geoscanner

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EDXRF Geoscanner method

based on the physical interaction of primary x-rays with atoms in the sample and acquisition of secondary fluorescent x-rays by an energy dispersive detector.

Instrumentation

• HV-Generator (R. Seifert & Co. ISO-DEBEYEFLEX 3003
• long fine focus Philips XRD Mo-tube Type PW 2275/2, 3 kW, 60kV mounted on a yz-stage
• COX capillary optics (flat beam 50 µm x 2000 µm)
• energy dispersive Peltier-cooled RÖNTEC drift chamber detector of 149 eV resolution at Mn (Ka) mounted at 45°
• evacuated nozzle mounted between detector and sample
• optical camera for image acquisition (y-stage)
• rotating sample holder (6 positions up to 1m)
• density line detector
• computer control

Evaluation

Data are stored as full spectra for each point. The full spectra can be corrected by fundamental parameters, quantified and compared with standards, stored in spreadsheets and plotted as element distribution profiles.

Kinetic effects can be obtained by comparison of time series.

Advantages

• in-situ method for chemical analyses of liquid, powder, solid or biogenic matter
• minimum sample preparation
• fast non-destructive data acquisition from points and 1D-profiles (full spectrum evaluation)
• high spatial resolution; focus <50 µm Ø
• variable step size and acquisition time
• all elements from Mg to U can be analyzed
• detection limits range from 0.x to 0.000x %

Disadvantages

• light elements cannot be detected (till Na)
• absorption by air of light elements (Mg, Al, Si)
• matrix correction is hinderd due to changing matrix
• inhomogeneities and geometry of the sample
• quantification is not yet optimized
• crystallographic interference

Standard measurement conditions

• 45 kV, 30 mA, 50µm step size, 5 sec

Application

Environment, sedimentology, magmatic cryptic layering, exploration, climate, experiments

For details see poster (PDF files):

• Geoscanner (PDF, 438 KB)
• High resolution EDXRF-scanning deciphering seasonal variation in laminated marine and varved lacustrine sediments (PDF, 367 KB)