Specification –EPMA/SEM
Background
An electron microprobe (EPMA) OR scanning electron microscope (SEM) capable of delivering
high precision quantitative chemical x-ray analysis of sub-micron areas is required for the
pursuance of a research project to study diffusion mechanisms in minerals.
We require analyses of elements with detection limits of down to about 50 parts per million at
highest achievable spatial resolution. We envisage the microscope will thus incorporate both
wavelength and energy dispersive detectors.
We are tendering for two instruments with the most likely outcome being that only one lot will be
purchased.
Lot 1 is specifically a multi wavelength dispersive spectrometer EPMA and lot 2 a Field Emission
sourced Scanning electron microscope. A subset of lot 2 will be the additional provision of energy
and wavelength dispersive spectrometers.
The instrument will form one of a suite of three laboratories to compliment existing tungsten
sourced EPMA and SEM in the long established electron microbeam laboratory of the dept of
Earth Sciences under the management of Dr Stuart Kearns.
Specification – Lot 1 EPMA
Category (weighting)
Required
Desirable
1. EPMA – Vendor
Vendor must supply specifications for:
supplied performance Beam current stability/drift
specifications (5%)
% Accuracy of accelerating voltage at range of
voltages
Beam diameter at set voltage/beam current
Faraday Cup measurement stability
Absolute accuracy of magnification readouts
SE/BSE resolution
FE source lifetime
WD and ED resolution and performance
1.1 WD Analysis
5 vertically mounted Wavelength dispersive
spectrometers
Combination of appropriate Gas Flow and/or
sealed proportional counters including
necessary gas regulators.
In total 4 PETs, 3 TAPs and 3 LIFs
1.2 ED Analysis
Integrated EDS – SDD-type detector (128eV at
MnKa resolution) Ultra thin window for boron xray.
Capable of Spectral Imaging (storage of
spectrum for every pixel on x-ray map)
At least three specs to have
‘high count-rate’ set-up
(large crystals and/or small
Rowland circle)
At least one spectrometer to
have slits option.
Either high and low pressure
counters or xenon counters.
1 spectrometer to have
capacity for analysis of
B,C,N and O.
125eV resolution or better.
1.3 Electron Column
1.4 Electron Imaging
System
1.5 Vacuum System
1.6 Computing (5%)
Software Control
Package
1.7 Optical
microscope
1.8 Specimen
Chamber, Stage,
(5%)
Stage Control
Sample Holders
1.9 Documentation
(5%)
High Resolution source electron gun (not
tungsten)
kV range of 1-30kV
Regulated beam current 1-200nA
Long term beam current stability
Automated pulsed faraday cup
Externally selectable final aperture
Capable of taking a EDS spectrometer
supplied by a third party vendor with detailed
mechanical drawings of the EDS mounting
system, aperture and port configuration.
Everhardt-Thornley type Secondary electron
detector
Multiple diode solid-state backscatter detector
Fully automated vacuum system. Sufficient
length to extend rotary pumps into adjacent
room (5m)
High specification PC platform
Minimum of two dedicated screens for software
package and a third screen for EDS
Separate monitor for electron image viewing
Separate monitor for optical image viewing
Complete software system to perform
quantitative and qualitative x-ray microanalysis
and image acquisition (from all detectors) and
processing options. To include Thin film
analysis routines. It is a requirement that the
software can acquire both ED and WD
simultaneously and integrated for combined
analysis. It is a further requirement that an
element can be analysed by summing the
signal from more than one spectrometer for
both quant and x-ray mapping.
2 licences of the software to be supplied
Free upgrades to latest version for 10 years
including change to new operating systems.
Light microscope with zoom optics and
autofocus capability
Digital Image store of optical image.
Large specimen chamber. Versatile 50x80mm
movement in X and Y with preferably 5mm
movement in Z. Airlock exchange of
specimens.
High precision X,Y and Z stage movement with
dedicated trackball/joystick to move in X and Y.
Minimum of 4 sample holders and shuttles
where required to take range of specimen
mounts including 6x25mm diameter, and 3x
thin sections (48x28mm).
All mechanical and electrical drawings to be
included. All manuals for third party items
supplied by the vendor (e.g. vacuum products).
List of all spare parts and catalogue/order
information.
FEG source
1-40kV
Regulated to 500nA
3 licences
Transmitted light option
100x100mm X,Y movement
0.5 micron reproducibility in
X, Y and Z..
All documentation to be in English
Paper copy of all instruction manuals
List of specialised tools required for
maintenance
1.10 Support and
Warranty (10%)
Training
1.11 Demonstration
(50%)
1.12 Pricing and
delivery (20%)
1.13 Final Acceptance
1.14 Options
Warranty to last 12 months after final
acceptance. Four years full service cover to
follow 12 month warranty period.
On-site training required for lab manager.
Assumed to be 6 days.
See below
All components must be operational before
final acceptance – no exceptions.
Upon repeat analysis of demonstration tests on
same samples to the approval of lab manager
to be undertaken after all specification checks
have been performed.
To be listed and priced separately
1- UPS system
3- Panchromatic cathodoluminescence
detector
Demonstration required will evaluate those components not weighted above. Proportional
weightings in brackets:
1) (10%) WDS qualitative scans on sample of Monazite (20kV, 20nA 5micron spot, to take 1
hour)
a) PET across range of U-Th on both gas flow counters (at more than one pressure
where applicable and xenon counters)
b) LIF in range Ce-Gd L lines
c) PET in range La-Nd (if possible)
2) (10%) WDS qualitative scans on Apatite across Fluorine peak using both integral and
differential PHA modes on TAP and 60Angstrom spaced crystal (e.g. PC0) at 15kV, 10nA,
10micron spot, to take 30mins)
3) (20)X-ray image of orthopyroxene acquired at highest possible spatial resolution using
10kV, 200nA beam for Al, Mg, Fe, Ca, Na on WDS and simultaneous acquire full spectrum
image on EDS. Image to be quantified (i.e with background correction and ZAF processed).
Slow scan image to run for several hours overnight.
4) (10%) Line profiles across orthopyroxene (same elements and conditions as above).
Maximum resolution across a 50micron line using both stage and beam move to take 30mins
each.
5) (10%) High resolution SE image (1, 5 and 25kV) – gold coated foram
6) (10%) BSE image to demonstrate high Z contrast – using oscillatory carbon coated zoned
mineral
7) (30%) Quantitative analysis of 3 mineral specimens – monazite, kaersutite, olivine.
Repeat of 10 analyses on each at 10kV and 20kV.Quantitative analysis of small silicate and
oxide crystals in experimental charge.
All analyses will be benchmarked against analysis at UoB on Cameca SX100 #837 under
same operating conditions. Estimated 2 days of analysis including overnight. All samples
and primary calibration standards to be supplied by UoB.