Laser-produced silver beams at ALTO

In November 2023, the RIALTO experimental setup has enabled the production of silver (Ag) and gallium (Ga) radioactive ion beams measured at the TETRA device during the N-RI-22 experiment. RIALTO consists of three dye lasers and two Nd:YAG lasers, one of which dedicated to pumping. We can therefore generate 4 different wavelengths.

Ion production is obtained by laser resonant ionization: silver ions are produced in a 3 step-3 colour scheme, while gallium ions are produced in a 2 step-2 colour scheme. Figure 1 illustrates the two ionization schemes. The first two UV stages are obtained by doubling the frequencies of the yellow and red lasers. Thanks to a common ionization wavelength (the YAG laser), the system can easily switch between Ag and Ga elements in just a few minutes.

Figure 1 : gallium and silver ionization schemes


The laser beams, sent collinearly through a 3 mm diameter tube at a distance of 18 meters, benefit from a position control system to maintain their geometric stability. This system prevents any deviation of the beams in the ionization tube and enables them to be adjusted in real time.

Figure 2 shows a γ spectrum of 123Ag measured on the TETRA decay station, with and without the use of the laser.

Figure 2 : 123Ag decay spectrum with and without laser. The photo shows the 3 collinear beams sent through the ion source.