Multichannel analyzer

In alpha-, beta-, and gamma spectroscopy, PHA is used to measure the energy distribution of particles emitted in nuclear decay.

[citation needed] After many pulses have been counted, the output spectrum shows the energy distribution of the radiation incident on the detector.

For example, a Geiger counter connected to an MCA in MCS mode could be used to record the amount of ionizing radiation emitted by a neutron generator at different voltages.

Specialized software processes the "sound" to perform pulse-height analysis and multichannel scaling, forming a complete MCA.

[3] Sound cards have high-speed but low-resolution (up to 192 kHz) ADC chips, allowing for reasonable gamma spectroscopy performance for a low-to-medium count rate.

A graph of number of counts against channel number
The output of an MCA used in pulse-height analysis mode to analyze a Cs-137 source
Pulse-Height Analyzer Principle: Three pulses, 1 , 2 , and 3 are detected at different times t . Two discriminators emit a counting signal if their set voltage threshold is exceeded by a pulse. Pulse 2 triggers the Lower Level E L but not the Upper Level E U . Pulse 2 is thus counted into the spectral region denoted as P . To ensure pulses are only counted into one channel, the anti-coincidence counter prevents Pulse 1 from being recorded into P .