A programmable-velocity smooth-driven Mössbauer data acquisition system

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

Lima

Conferencia; LACAME10, XII Latin American Conference on the Applications of the Mössbauer Effect; 2010

Quality of Mossbauer spectra strongly relies upon performance of the relative velocity modulator between source and absorber. Traditional electromechanical driving techniques demand hard-edged square or triangular velocity displacements that introduce long settling times and demand careful tuning. For this work, the behavior of regular velocity transducers and drive units was carefully studied under different working conditions. Selected alternatives for velocity reference waveforms in both constant-acceleration and constant-velocity techniques were tested. Significant improvement in spectrometer efficiency and accuracy was achieved replacing triangular and square hard edges with continuous smooth-shaped transitions. A criterion for best waveform selection and synchronization is presented and attainable enhancements are evaluated. In order to fully exploit this novel driving technique, a compact microprocessor-based architecture is proposed for a suitable data acquisition system implementation. It combines a programmable highresolution digital waveform generator synchronized with a versatile multichannel scaler. This arrangement can be configured in constant-acceleration mode with velocity reference and number of channels that best fit a given application. The same hardware can also be used to drive the source in programmable constant-velocity mode, providing a tool for recently developed tracking [1,2] and scanning [3] techniques. Calibration and efficiency tests were addressed. A complete transmission spectrometer including the new data acquisition system was tested. Linearity and energy resolution of the instrument are presented and compared with conventional instrumentation performance.