CROSS-SECTIONS MEASUREMENTS ON FAST-NEUTRON REACTIONS LEADING TO VERYSHORT HALF-LIFE NUCLEUS

A SODERN sealed tube neutron generator producing 14 MeV neutrons has b een used in order to detect radionuclides with a half-life from about 20 microseconds to 1 second. An interesting feature presented by this kind of neutron generator is its capability adjustable pulses from 5 m icroseconds to 10 milliseconds width or more, at frequencies from cont inous mode to 10 kHz. This capability makes it possible the study of v ery short half-lived isotopes down to a few microseconds with the cycl ic activation method and without any transfer system. A semiconducteur gamma rays detector Ge(HP) with MCA was used for measurement of gamma lines. The half-life measurement of short-lived activation products i s performed with a fast multiscaler. Fifteen isomerics states have bee n successfully studied by the cyclic activation method. The isomeric s tates activation cross-sections have been measured.