Alpha spectrometric characterization of thin $^{233}$U sources for $^{229\text{(m)}}$Th production

Abstract: Four different techniques were applied for the production of $<sup>{233}$U alpha recoil ion sources, providing $<sup>{229}$Th ions. They were compared with respect to a minimum energy spread of the $<sup>{229}$Th recoil ions, using the emitted alpha particles as an indicator. The techniques of Molecular Plating, Drop-on-Demand inkjet printing, chelation from dilute nitric acid solution on chemically functionalized silicon surfaces, and self-adsorption on passivated titanium surfaces were used. All fabricated sources were characterized by using alpha spectrometry, radiographic imaging, and scanning electron microscopy. A direct validation for the estimated recoil ion rate was obtained by collecting $<sup>{228}$Th recoil ions from $<sup>{232}$U recoil ion sources prepared by self-adsorption and Molecular Plating. The chelation and the self-adsorption based approaches appear most promising for the preparation of recoil ion sources delivering monochromatic recoil ions.