Advances in constant-velocity Mössbauer Instrumentation

A. VEIGA; N. MARTÍNEZ; P. MENDOZA ZÉLIS; G. A. PASQUEVICH; F. H. SÁNCHEZ

Montpellier, Francia

Conferencia; International Conference on the Application of the Mössbauer Effect; 2005

A prototype of a programmable constant-velocity scaler is presented. This microcontroller-based instrument allows the acquisition of partial Mössbauer spectra in selected energy regions using standard SCA, drivers and transducers. No additional multichannel scaler is required. It can be fully operated by a remote application, thus data acquisition can be automated. The instrument consists of a programmable counter and a constant-velocity reference. The reference waveform generator is amplitude modulated with 13 bit resolution, and is programmable in a wide range of frequencies and waveforms in order to optimize the performance of the transducer. The counter is compatible with most standard SCA, and is configured as a rate-meter that provides counts per selectable time slice at the programmed velocity. >As a direct estimation of the performance, a partial Mössbauer spectrum of a natural iron foil was repeatedly taken. Positive energies were recorded in 512 channels ranging from 0 to 10 mm/s, accumulating 20 seconds per channel. A line width of 0.20 mm/s was achieved in all cases, what is equivalent to the line width of the spectrum taken with the same transducer, servo amplifier and SCA, using a constant-acceleration technique with a Nucleus MCS-II multi channel scaler. Long term stability proved to be satisfactory and overall efficiency reached 80%. This constant-velocity technique has been recently applied in different experiments. We show two non conventional applications of this technique: the determination of Fe hyperfine field temperature dependence in the FeSn2 compound, and the study of the Iron magnetic moments dynamics in the nanocomposite Fe90Zr7B3 submitted to an AC magnetic field.