The 3He long-counter TETRA at the ALTO ISOL facility

Abstract A new β -decay station (BEDO) has been installed behind the PARRNe mass separator operated on-line at the electron-driven ALTO ISOL facility. The station is equipped with a movable tape collector allowing the creation of the radioactive sources of interest at the very center of a modular detection system. The mechanical structure was designed to host various assemblies of detectors in compact geometry. We report here the first on-line use of this system equipped with the 4π 3 He neutron counter TETRA built at JINR Dubna associated with HPGe and plastic 4π β detectors. The single neutron detection efficiency achieved is 53(2)% measured using the 252 Cf source. For β-delayed neutron measurements the neutron detection efficiency was derived from the comparison of gated γ-spectra. The on-line commissioning of the TETRA setup was performed with laser-ionized gallium beams. β and neutron events were recorded as a function of time. From these data we report P 1 n ( 82 Ga)=22(2)% and T 1 / 2 ( 82 Ga)=0.604(11) s in good agreement with values available in the literature. The new detection system will be used in other experiments aimed at investigations of β-decay properties of neutron-rich isotopes produced at ALTO.