A new technique for preparation of targets of powdered materials

Various targets of powdered materials have been made for nuclear experiments by developing a centrifugal precipitation method, which is particularly useful in the cases of: (a) metals with high melting point and low vapour pressure, (b) oxides or carbonates which are difficult to be handled by the usual vacuum evaporation technique and (c) some enriched isotopes which are generally very minute in quantity (less than approximately 10 mg). The powdered samples were suspended in liquid paraffin with an ultrasonic vibrator, and then centrifugally precipitated on a thin backing film of Mylar or aluminium. Uniformity in the thickness of the targets obtained in this way was measured with an α-ray thickness gauge and was known to be satisfactory. Inspection for any impurities contained in the materials used or contaminated during the preparation process was carried out by measuring the scattered protons from the targets. No significant impurity was detected larger than 10-4 mg/cm2. (Auth.)