A radiotracer system for sup(119m)Sn using time-interval analysis

The application of time-interval analysis to the detection of the isotope sup(119m)Sn is described. This is thought to be the first time that the technique has been used to detect an isotope with such a short half-life (19ns) and such low energy radiation (<40keV). After-pulsing in the photomultiplier is found to be a problem since a high gain is necessary to detect the sup(119m)Sn radiation. In spite of this the counting system developed will measure sup(119m)Sn activities within the range 3μCi to 1pCi. The lower limit corresponds to a mass of 2 x 10-12g of tin at specific activity of 400mCi g-1. In this investigation tin radiotracer was diffused into tin-doped GaAs substrates under strictly controlled conditions typical of those experienced during growth by liquid-phase epitaxy, and diffusion profiles were measured. (author)