## 1 Introduction  
Alpha-particle spectroscopy is commonly used for applications in various fields such as nuclear [1; 2; 3; 4], environmental [5; 6; 7; 8], artistic [9; 10], and biological [11; 12; 13; 14] samples. Conventional approaches for the preparation of alpha-particle sources generally include (i) radiochemical separation and purification [15; 16], (ii) preparation of weightless and thin solid source onto a suitable backing material [17; 18; 19], and (iii) alpha-particle spectroscopic measurements under vacuum conditions using solid-state semiconductor detectors [20; 21; 22; 23; 24]. High-resolution alpha-spectrometry is always neededfor qualitative identification and accurate determination of the alpha-emitting radioactive isotopes concerned. For this purpose, the preparation of low mass solid sources with high uniformity that reveals a significant feature is still today extensively investigated. Conventional approaches include vacuum sublimation, drop-casting, co-precipitation, and electro-precipitation [16; 17; 21; 25; 26]. While drop-casting generally allows relatively poor resolution with a large low-energy tail contribution, vacuum sublimation requires an elaborated set-up and gives a relatively poor deposition yield, and co-precipitation is very time-consuming since the sample must be pretreated using chromatography for separation and purification of the actinides. Finally, electro-precipitation represents a more straightforward and spreading route allowing a quantitative alpha-emitter deposition with a high-quality solid radioactive source deposited in the form of a very thin and uniform coating. With regard to electro-precipitation techniques, this method was firstly developed in the early 1950s [27; 28] and extensively explored since, following the works published in 1972 by [PERSON] et al. [29] and [PERSON] [30] using ammonium salt with various counter anions as electrolytes. The main principle of this method is based on the use of a negative current for depleting water into OH\({}^{-}\) hydroxyl ions generated close to the cathode electrode which subsequently reacts with highly and positively charged actinide ions (Ac\({}^{n+}\)) affording actinide hydroxides, very insoluble compounds, precipitated onto cathode electrode surfaces. The electrolyte generally represents a large number of complex anions (Cl\({}^{-}\), ClO\({}_{4}\)\({}^{-}\), SO\({}_{4}\)\({}^{2-}\), HSO\({}_{4}\)\({}^{-}\), NO\({}_{3}\)\({}^{-}\)) and acidic medium to prevent dramatic hydrolysis of actinide ions into actinide hydroxides in bulk solution [31; 32]. Otherwise, experimental conditions represent significant features to obtain a quantitative deposition of radionuclides. The work published by [PERSON] et al., [29] demonstrated that using optimized conditions, e.g., ammonium oxalate-chloride mixture, pH value of 2, a current density of 400 mA.cm\({}^{-2}\), and typical 1 h of precipitation onto conductive substrates from 5-8 cm\({}^{2}\), could enable high precipitation yields of more than 98% for several different actinides (\({}^{230}\)Th, \({}^{237}\)Np, \({}^{239}\)Pu, \({}^{241}\)Am, and \({}^{244}\)Cm). High-resolution alpha sources can be obtained with typically full width at half maximum (FWHM) values of e.g., 24 keV for \({}^{241}\)Am. Conventional substrates are metals, and often stainless steel. In the precipitation process, another thing should be remarked on, namely the presence of interfering metal ions such as iron, aluminum, natural thorium, and zirconium, etc. [PERSON] et al. [29] demonstrated that using fluoride-complexing anions enable the overcoming of such interference. However, the use of such fluoride anions dramatically decreases precipitation efficiency proved by [PERSON]'s work.