RIB production by photofission in the framework of the ALTO project: First experimental measurements and Monte-Carlo simulations

The ALTO facility (Accélérateur Linéaire auprès du Tandem d’Orsay) has been built and is now under commissioning. The facility is intended for the production of low energy neutron-rich ion-beams by ISOL technique. This will open new perspectives in the study of nuclei very far from the valley of stability. Neutron-rich nuclei are produced by photofission in a thick uranium carbide target (UCx) using a 10 μA, 50 MeV electron beam. The target is the same as that already had been used on the previous deuteron based fission ISOL setup (PARRNE [F. Clapier et al., Phys. Rev. ST-AB (1998) 013501.]). The intended nominal fission rate is about 1011 fissions/s. We have studied the adequacy of a thick carbide uranium target to produce neutron-rich nuclei by photofission by means of Monte-Carlo simulations. We present the production rates in the target and after extraction and mass separation steps. The results from Monte-Carlo simulations are compared to experimental data either with the ALTO facility (in the first step of commissioning, i.e. 100 nA of the electron beam current intensity), or with fast-neutron-induced fission generated from a 26 MeV deuteron beam. The results obtained support the suitability of FLUKA simulation code used to describe all the photofission process with an electron beam energy of 50 MeV.