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

In this paper the source preparation procedures for high-resolution U-238 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 U-238. U-238 was deposited from organic (iso-propanol) and inorganic-H2SO4/(NH4)(2)SO4, 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 U-238 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 mu g cm(-2) surface density, similar to 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.