Production of secondary radioactive beams from 44 MeV/u Ar projectiles

Secondary beams have been produced through interaction of a 1760 MeV Ar beam with a 99 mg/cm2 Be target. An achromatic spectrometer is used to select the magnetic rigidity corresponding to a given beam, and to transport this beam over a distance of about 18 m. The beam purity is studied using a solid state ΔE-E telescope. Beams of 38S and 39Cl are produced with a purity of about 80%, and production rates of 1.5 . 10-6 I0 and 5 . 10-5 I0 respectively. Here I0 denotes the primary beam intensity. Beams of 38Ar, 39Ar and 41K are produced with about the same abundances as 39Cl but with lower purities. It is shown that, by setting properly the experimental parameters, the beam production can be improved by a factor 2 to 5. This could lead to intensities of about 2 . 106 pps for 38S, and of 107 to 108 pps for the four other beams. The possibility of purifying these beams by placing a degrader between the two dipoles of the spectrometer is shown experimentally. (orig.)