CHARACTERIZATION OF FLUOR CONCENTRATION AND GEOMETRY IN ORGANIC SCINTILLATORS FOR IN-SITU BETA-IMAGING

Development of a small area (1-2 cm(2)) in situ beta imaging device in cludes optimization of the front end scintillation detector, which is fiber optically coupled to a remote photon detector, Thin plastic scin tillation detectors, which are sensitive to charged particles, are the ideal detectors due to the low sensitivity to ambient gamma backgroun ds, The light output of a new binary plastic scintillator was investig ated with respect to increasing concentrations of the fluor (0.5-2.0% by weight) and varying thickness cylindrical configurations of the int ended imaging detector, The fluor had an emission maximum increasing f rom 431 to 436 mn with increasing fluor concentration, The decay time( s) had two components (0.38 and 1.74 ns), There was an similar to 20% increase in light output with increasing fluor concentration, measured with both (TI)-T-204 betas and conversion electrons from Bi-207, The highest light output of this new scintillator was measured to be simil ar to 30% lower than BC404. Simulations predicted the 1.5 mm scintilla tor thickness at which light output and energy absorption for similar to 700 keV electrons (e,g,, from Tl-204, F-18) were maximized, which c orresponded with measurements, As beta continua are relatively feature less, energy calibration for the thin scintillators was investigated u sing Landau distributions, which appear as distinct peaks in the spect ra, As the scintillators were made thinner, gamma backgrounds were sho wn to linearly decrease.