In general, spectroscopes are devices designed to measure the spectral power distribution of a source. The incident radiation generates a signal that allows to determine the energy of the incident particle.
In proportional counters, the number of electrons produced is proportional to the energy and type of the incident particle. Therefore, proportional counters are capable of particle identification and energy measurement (spectroscopy). Different energies of radiation and different types of radiation can be distinguished by analyzing the pulse height, since they significantly differ in the primary ionization (low-LET vs high-LET). Proportional counters may be used for example to analyse a spectrum of alpha radiations or a spectrum of beta particles. The energy resolution of a proportional counter, however, is limited because both the initial ionization event and the subsequent ‘multiplication’ event are subject to statistical fluctuations characterized by a standard deviation equal to the square root of the average number formed.
A large volume spherical proportional counter can be used for neutron measurements. The pure N2 gas is studied for thermal and fast neutron detection, providing a new way for neutron spectroscopy. The neutrons are detected via the 14N(n,p)14C and 14N(n,α)11B reactions.
It must be noted, for gamma spectrometry, the most common detectors include sodium iodide (NaI) scintillation counters and high-purity germanium detectors.