Alpha-Particle Densitometer with Variable Response

An alpha-particle gas densitometer is described with an instrument response that can be tailored to given specifications by shaping the energy distribution of the radioactive alpha source. Relations are derived to establish the connection between a specified densitometer response and the corresponding source distribution. Shaped sources can be constructed by mounting contoured baffles on alpha sources. The operation of the densitometer is demonstrated experimentally for a linear and a logarithmic instrument response to air density variations.