Chemistry Reference
In-Depth Information
Fig. 2.44 The sensor head of the miniaturized Mössbauer spectrometer MIMOS contains the
drive (vibrating) unit, the Mössbauer source, the detectors and amplification electronics. MIMOS
is set up in backscattering geometry [
77
,
78
]
transmission Mössbauer spectroscopy. The spectrum is a superposition of the
spectra of five different iron-containing species with percentages given in the table
on the right in Fig.
2.43
. Such measurements are carried out routinely in the
context of regular maintenance works in nuclear and conventional power plants.
2.3.6 Miniaturized Portable Mössbauer Spectroscopy
The miniaturization of Mössbauer instrumentation started under the guidance of E.
Kankeleit at Technical University of Darmstadt and continued to completion ready
for in-field-experiments by G. Klingelhöfer et al. at University of Mainz. The
result is a portable miniaturized Mössbauer spectrometer (abbreviated as MIMOS)
[
77
] as displayed in Fig.
2.44
. This instrument is set up in backscattering geom-
etry, which renders sample preparation such as the production of powders or thin
slices for many applications unnecessary and thus also enables one to perform non-
destructive measurements. The instrument can be taken to the field and simply
placed, for example, on a rock surface of interest to be analyzed as realized by the
MIMOS II instruments on the NASA Mars Exploration Rovers, which act as
robotic field geologists. Another example is the analysis of rare and precious
samples such as archaeological artefacts. The instrument is still developed further:
Currently, for the advanced MIMOS IIa [
78
], the Si-PIN diode detectors are
replaced by Si Drift Detectors, which have a much higher energy resolution. This
result in (a) significantly improved signal-to-noise ratios and therefore shorter
measurement times, and (b) allows for the simultaneous acquisition of X-Ray
Fluorescence spectra for elemental analysis, whereby the
57
Co Mössbauer source
also acts as the X-ray excitation source.
