Scintillation counter method of intercomparing neutron source strengths by means of a manganous sulfate bath

It has proved feasible to use a scintillation counter to m eas ure th e relative activity of a large manganous sulfate bath, thereby de termining the neutron-emission rates of n eutron sources relative to the national standard neutron so urce of the National Bureau of Standards. A scintillat ion counter a llows the calibration of sources weaker by a factor of seven than those it was previously possible to calibrate by m eans of a Geiger-Muller counter. Th e use of CS137 as a reference pulse height to which the scintillation counter system is adjusted by m eans of a two channel pulse he ight a nalY7,er m akes pos ible t h e reliable reproduction of r es ults from day to day. By using the scintillation counter the ratio of t he national reference standard neutron so urce (NBS-II ) to the national s tand a rd neu t ro n so urce (NB -I ) has bee n red etermined and is found to be 0.9393 0 .0017.