Hello there, could anybody here explain how the fine gain and coarse gain affect the spectra from NaI(Tl) detector? It's written in the manual of MCA that there is no exact adjustment of coarse gain and fine gain (so you can adjust randomly until you get the desired spectra), but is it true?
The coarse/fine gain effects, how much the original signal (pulse height) is amplified. If you choose higher gain, your signals will be sorted a higher range of channels of your MCA, so you get a higher resolution. On the other hand, if the gain you choose is to high, you will cut the high-energy part of your spectrum.
In priniciple, you can choose any gain you want, and afterwards you make a energy/channel calibration using standards with known gamma energies.
One important point you have to remember is dynamic range of MCA is always fixed during measurement. Usually, dynamic range of Ortec or Canberra MCAs are 10 Volts.
Second, output signal from amplifier has adjustable amplitude, which you can change by setting coarse/fine gain. Because it is adjustable while dynamic range of MCA is fixed, coarse/fine gain can shift the peak position in the spectrum (Ex: if you set gain = x5, the peak is located at channel 500, if you set gain x10, the peak is shifted to channel 1000).
Setting coarse/fine gain as your desire. usually, one consider the energy range for measuring to adjust coarse/fine gain properly.
Hello, check the attachment picture, it is related with coarse gain.
Source: Experimental γ Ray Spectroscopy and Investigations of Environmental Radioactivity BY RANDOLPH S. PETERSON.
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