The radiation detector output is often shaped into Gaussian
or quasi-Gaussian shape to improve the measurement performance. An
adaptive digital Step-Gaussian filter is presented for
quasi-Gaussian pulse shaping in this paper. It can be applied for
both exponential decay input and step input. The transfer function
of the filter is established. The amplitude-frequency features of
the new filter are compared with the PZC-(RC)
n
filter and the
CR-(RC)
n
filter. The results indicate that the new filter has
the same amplitude-frequency features as the PZC-(RC)
n
filter
and it possesses more effective filter performance than the
CR-(RC)
n
filter. An X-ray fluorescence measurement system based
on a FAST-SDD detector is set up for experiments. The proposed
filter is verified by the measured pulses that are generated from a
manganese sample. The shape of the filter output shows that the
Step-Gaussian filter can eliminate the undershoot that exists in the
CR-(RC)
n
filter output. The amplitude spectrums with different
shaping times are created to study the shape of the characteristic
peak. The results show that the Step-Gaussian filter can cancel the
low-energy peak tailing of the 5.89 keV peak. The peak shape
parameter, FWTM/FWHM ratio, is also introduced to evaluate the
performance of peak shape improvement. The 5.89 keV peaks of the
spectrums that are generated by using Step-Gaussian filter are
closer to Gaussian distribution than that of the CR-(RC)
n
filter.