Electron Probe Microanalysis (EPMA)

As of 20-MAR-96 a digital CAMECA SX100 Electron Microprobe (introduced Sept'94) was being installed in Clausthal. The SX100 replaces an aging JEOL JXA-3 installed and operational since 1967, which was retired in May 1995 after 27 years of service. It is now on public view in the department as a museum piece.

Features:

40 kV electron gun, W-filament

Spectrometers:
Four vertical wavelength-dispersive spectrometers (PC0 - PC3 = synthetic multilayers):

No.	Crystals	Special features
1	TAP, PET, PC1, PC2	extended 2theta range, allowing O Ka to be measured on the TAP xtal
2	LIF, PET	changeable counter slit to obtain higher spectral resolution
3	LLIF, LPET	large area ("L") crystals
4	TAP, PC0, PC1, PC3	--

Element range covered:

Crystal Formula 2d [Å] K shell L shell

PC3 Mo/B₄C Multilayer 200 Be - B

PC2 Ni/C Multilayer 95 B - O

PC1 W/Si Multilayer 60 C - F

PC0 W/Si Multilayer 45 O - F

TAP C₈H₅O₄Tl 27.745 F - P Mn - Nb

PET C₅H₁₂O₄ 8.742 Si - Mn Sr - Tb

LIF LiF 4.027 Sc - Rb Te - U

The system is (software-) integrated with a PGT thin-window liquid nitrogen cooled ED-system, specified resolution 138 eV.

Specimen stage:
The minimum step size is 0.5 µm. Accommodation of a wide range of samples sizes, including 40mm round, 48*28mm, 30*30mm, but the standard size being 1 inch (25.4mm) round, the maximum specimen size 75*50*25 mm. A maximum of 6 samples/standards of the standard size (1in) can be loaded at the same time. All samples will have to be polished, and for quantitative work samples must be flat and mounted perpendicular to the electron beam. Materials must be stable under electron bombardment and vacuum conditions.

Optical microscope:
reflected and transmitted light optics and polariser. The magnification is fixed to 400. An attached color CCD camera provides an image on the computer screen.

Vacuum system:
Oilfree vacuum system based on a Leybold magnetic-bearing Turbovac and Alcatel Drytel-31 combination. Anticontamination measures comprising a liquid nitrogen cold finger near the point of impact of the electron beam, and an oxygen jet to burn off carbon contamination.

Instrument control via a SUN SPARCstation5 running under Solaris 2.5.1. The instrument is fully automated for unattended overnight operation, including a Z-axis autofocus system. This is helped by an uninterruptable power supply (UPS).

Bal-Tec MED 020 sputter-coater for coating (carbon, Ag, Au, etc) of non-conductive specimens to facilitate a stable electron beam.

A second SUN workstation with
- Cameca SX software running in dummy mode for offline data processing, image analysis and software training.
- Attached CD-recorder and DAT tape streamer for data archiving and exchange.
A networked PC with

locally made point logging device using a standard ZEISS polarizing petrographical microscope (following a design by Dr. S.J.B. REED, Cambridge University) to enable offline point selection. Dr. Bernd Prause developed the software both for the pointlogger-control and data conversion.
The MinIdent-PC programme by Prof. Dorian G.W. Smith and David Pierre Leibovitz to help identify a mineral given its (microprobe) analysis

A variety of standard materials that cover most geological and materials science applications is available. The original file format of analysis data is ASCII, but can be converted to Excel 5. Possible image formats are "Cameca" (ASCII), Sun Raster or TIFF. Only the Cameca format contains information about magnification and analysis conditions. Data transfer by floppy, CD-R, DAT tape or ftp.

Contact Klaus Herrmann for details.

Department of Mineralogy, Geochemistry and Salt Deposits
Institute for Mineralogy and Mineral Resources
Technical University Clausthal

last updated Dec, 2001

Crystal	Formula	2d [Å]	K shell	L shell
PC3	Mo/B₄C Multilayer	200	Be - B
PC2	Ni/C Multilayer	95	B - O
PC1	W/Si Multilayer	60	C - F
PC0	W/Si Multilayer	45	O - F
TAP	C₈H₅O₄Tl	27.745	F - P	Mn - Nb
PET	C₅H₁₂O₄	8.742	Si - Mn	Sr - Tb
LIF	LiF	4.027	Sc - Rb	Te - U