Photo of a gas-filled neutron detector. 

Gas-filled detectors may be used to detect either thermal neutrons via nuclear reactions or fast neutrons via recoil interactions. The walls of the detector are about 0/5 mm thick and are manufactured from either stainless steel or aluminum. Both materials provide satisfactory performance; however, since steel walls absorb about 3% and of neutrons and aluminum walls absorb only about 0.5% of the neutrons, aluminum tubes are usually preferred as having a higher detection efficiency.

The images, below, show the typical set-up for gas-filled neutron detectors

The following graph shows the relationship between pulse height and applied voltage curves: