Laser ablation opens a material-independent method to produce ions from transition metals for laser spectroscopy. To overcome some drawbacks of this process, an ion source is under development at TU Darmstadt. A distinctive feature of this source is that ions are produced via laser ablation in presence of helium buffer gas where they stop and cool in the process of their collisions with the buffer gas atoms and are then extracted by the gas flow into low-pressure conditions through the supersonic nozzle. The compact RF-only funnel ion guide placed on the axis behind the nozzle exit allows for effective extraction of highquality ion beams into a pressure region below 10 −4 mbar. The extraction is realized by using the gas flow trough a supersonic nozzle and an RF-only funnel ion guide, followed by a second nozzle and an RF+DC funnel representing two differential pumping stages. The technical details of this laser ablation ion source are described and the results of the first tests with the RF-only funnel are presented.

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A laser ablation ion source has been built and tested at the COALA beamline. Time-of-flight measurements for various elements are sufficiently accurate to confirm the production of the intended ion species. Furthermore, the isotope shift between 40Ca+ and 44Ca+ has been determined on these bunched beams by collinear laser spectroscopy and compared to previous measurements. The frequency of the $4s{}{}^{2}\textit {S}_{1/2} \rightarrow 4p{}{}^{2}\textit {P}_{1/2}$ 4 s 2 S 1 / 2 → 4 p 2 P 1 / 2 transition has been determined to $\nu ^{\mathrm {D1}}_{0}=755 222 766.8(15)$ ν 0 D 1 = 755222766.8 ( 15 ) MHz for 40Ca+, as well as the corresponding isotope shift of 44Ca+ to 848.1(23) MHz. This is in a good agreement to more accurate measurements performed in a recent ion trap experiment and demonstrates the strength of the collinear-anticollinear approach to reduce systematic effects caused by the broad velocity distribution generated in the ablation process.