Preparation of high-resolution 238U α-sources by electrodeposition: a comprehensive study

In this paper the source preparation procedures for high-resolution ²³⁸U sources are described and compared. This work was done within collaboration between CIEMAT and IRMM in the frame of MetroFission, a project of the European Metrology Research Programme, in order to determine the alpha-emission probabilities of ²³⁸U. ²³⁸U was deposited from organic (iso-propanol) and inorganic-H₂SO₄/(NH₄)₂SO₄, saturated NH₄NO₃-electrolyte solutions on metal backings. The parameters affecting electrodeposition were studied and optimized. The activity distribution of uranium was checked by autoradiography. Results show that the ²³⁸U source quality is significantly better using the saturated NH₄NO₃ than the two other electrolytes. By this method, sources of 18.6–22 mm diameter, 26 μg cm^?2 surface density, ~15–18 keV resolution and a peak to valley ratio higher than 50 could be made. This reconciles the inherently opposing requirements of high resolution and sufficient count rate needed to determine the alpha–emission probabilities accurately.