Pulse Height Analysis Discrimination of Photons

The y-detector of a Mossbauer spectrometer converts the incident y-photons into electric output pulses of defined charge (see Sect. 3.1.6). The detector signals are electronically amplified and shaped by an amplifier network to obtain strong needle pulses with well-defined rise time, so that the pulse height is proportional to the energy of the incident photon. The amplifiers are usually adjusted to obtain 

For the visualization of the SCA discrimination window on the MCA screen, the TTL pulses, which map the coincidently incoming y-pulses, can be used to mark the range of channel numbers corresponding to the selected voltage range. The marks allow instantaneous control while setting the dials for lower and upper limits to the 

In summary, pulse-height analysis (PHA) prior to a Mossbauer measurement is an essential step in tuning a Mossbauer spectrometer. PHA allows the adjustment of the y-detection system to the Mossbauer photons and the reduction of noise by rejecting nonresonant background radiation. 

---