Implementation of a preamplifier-amplifier system for radiation detectors used in Mossbauer spectroscopy

We report the assembly and testing of a preamplification and amplification system for pulses produced by gaseous radiation detectors commonly used in Mossbauer spectroscopy. The system is composed by a pair of commercial integrated circuits A203 and A206, which operate as charge sensitive preamplifier-shaping amplifier and linear amplifier-low level discriminator, respectively. The integrated circuits were interconnected in the unipolar output mode and placed inside a metallic shielding, which prevents noise amplification for a suitable signal-noise ratio. The system was tested by irradiating a proportional counter LND-45431 with characteristic X rays of 6.3 keV and gamma rays of 14.4 keV emitted by a Mossbauer radioactive source of Co-57 (Rh). Unipolar pulses with Gaussian profile were obtained at the output of the linear amplifier, whose amplitudes were close to 0.4 V for 6.3 keV X rays and 1.4 V for 14.4 keV gamma rays. Pulse height spectra showed that the system allows a satisfactory identification of the X-rays and gamma rays emitted by the Co-57 source, giving the possibility to make a good selection of the 14.4 keV peak for having a suitable signal-noise ratio in the Mossbauer spectra. Absorption percentages of 14 % were found by taking the Mossbauer spectra of a natural iron absorber. The assembly and tests of the system are presented through this paper.