A system for measurement of less than 1 ppt (parts per trillion) of helium contained in a solid within the range of mass between 100 mg and 1 g has been developed for the primary purpose of measuring neutron‐induced helium production cross sections. The system consists of an apparatus based on ultrahigh vacuum techniques, computer codes to estimate suitable parameters for the given experimental conditions and to control data acquisition parts, and an appropriate routine of operation of the system. The system apparatus consists of a gas releaser, a mass spectrometer, and a standard helium supply. A sample containing helium is evaporated in the gas releaser and the gas is analyzed with the mass spectrometer after purifying it for helium to decrease background gases. The background of helium for a dummy sample of silicon is measured to be 0.04 ppt. The total uncertainty of the apparatus is 4.4% in the range of (0.5–5.0)×1010He measurement. ©1996 American Institute of Physics.