Working parameters of the electron - beam-generated ion source for ISOL facilities

An electron-beam generated plasma (EBGP) ion source for nuclear spectroscopy purposes at YASNAPP (YAdernaya Spektroskopya NA Putchkah Protonov - nuclear spectroscopy using proton beams) isotope separation on-line facility is presented. Working conditions both in on- and off-line mode are presented and discussed. Formation of a potential trap inside a discharge chamber is an advantage of the presented construction, enabling relatively high ionization efficiencies (2-5%) even for hard-to-ionize elements like Be, Ti, V, Zr, Nb, Mo, Tc, Ru, Rd, Hf, Ta, W, Re, Os, Ir, Pt. The paper presents estimation of critical values of working parameters that enable formation of the ion trap leading in consequence to high efficiency of ionization. The optimal temperature of the discharge chamber and cathode walls is found to be in the range 2600-2800 K. Calculations of the output rates of ions produced in the on-line mode are also presented as well as the constraints on the half-life time of obtained nuclides imposed by construction details like the target material and its thickness.