Measurement of Thermal Neutron Flux

A new technique has been developed for the measurement of thermal neutron flux. Small glass beads (~ 1 mm radius) are made black to thermal neutrons by the inclusion of B10. In addition, a 1/v activation such as cobalt, dysprosium, or indium is incorporated in the glass to measure the fluence (nv¿t). Following activation over a measured time interval, the absolute source strength of a Co bead is determined by ¿-¿ coincidence. The flux is directly proportional to the source strength. The Dy and In beads are calibrated relative to a Co bead.