A method for preparing a large sized, uniform and stable built-up film of 109Cd icosanoate as a radioactive source by utilization of an extremely small amount of substrate solution

A stable radioactive source in vacuo was obtained by a modified horizontal lifting method of Langmuir-Blodgett (L/B) film. In spite of the slight consumption of the substrate solution (only 2 - 2.5 ml) for preparing a 15 mm x 25 mm sized L/B film containing four molecular layers of 109Cd icosanoate, the deposition of the film was complete. The reliability of the deposited films by this method was confirmed by their radioactivities, deposition ratios and autoradiographs. The condition to obtain a larger sized homogeneous L/B film (20 - 25 mm x 102 mm) was also examined. Two or four molecular layers of nonradioactive Cd icosanote deposited on the L/B film of 109Cd icosanoate did not influence the intensity of the γ-ray of 88.0 KeV. Concequently, it is possible to obtain the high radioactive source by the deposition of the multilayers of 109Cd icosanoate. Spectra of L2 and L3 conversion electrons from the 109Cd in its built-up film were also determined. In conclusion, the present depositing method for the L/B film is excellent for the manufacturing the radioactive source and thought to be also applicable for the deposition of other valuable materials. (author)