Large-surface diodes and even neon lamps can function as radiation sensors. The circuit shown in the figure operates with a voltage close to the ionization of an ordinary neon lamp, which then becomes sensitive to ionizing radiation. When an ionizing particle passes between the electrodes of the neon lamp it conducts a current pulse that appears in the power field effect transistor gate. Amplified, this pulse results in an audible pulse on the speaker. An important point to note is that the glass of the neon lamp blocks less penetrating radiation like alpha particles and that the small dimensions of the lamp make it inefficient in detecting radiation from low intensity sources.
