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

In this paper the source preparation procedures for high-resolution 238 U 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 238 U. 238 U was deposited from organic (iso-propanol) and inorganic-H 2 SO 4 /(NH 4 ) 2 SO 4 , saturated NH 4 NO 3 -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 238 U source quality is significantly better using the saturated NH 4 NO 3 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.