An essential task in Mössbauer spectroscopy before evaluating a Mössbauer spectrum is to assign a velocity value to each channel of the spectrum. Principally the maximum velocity of the source motion can be determined by means of a Mössbauer calibration spectrum. Mostly a Fe-spectrum is used for this purpose.
A very comfortable and quick way of determining the velocity is to use a laser interferometer. This instrument gives a precise information on the velocity of each channel of the spectrum and permits to determine easily the linearity of the Mössbauer drive system. In contrast to the Mössbauer calibration measurement, the laser interferometer gives evidence in a wide velocity range.
The Mössbauer Calibrator MVC-450 consists of a laser interferometer, which generates an analog pulse train with continuously changing frequency. This frequency is proportional to instantaneous value of the measured velocity. The second part of the calibrator is a NIM module, which supplies the laser interferometer with power and transforms its output pulses into a digital form.
A Drive Unit MDU-1200, connected with the Mössbauer Velocity Calibrator MVC-450, shows on its 4-digit display for each channel its velocity value. By transferring the interferometer data to a PC and evaluating them by a least squares fit, the most precise velocity determination is achieved.