An RF mass spectrometer of the L. G. Smith type was built with 2 aims:
to provide an experimental test of the CPT invariance (proton-antipro
ton mass comparison) and to measure the atomic masses of nuclei far fr
om stability produced in the ISOLDE-PS Booster facility. As a priority
was given to the first application, the features of the spectrometer
are presented in this framework. Then, a discussion is made about the
adaptation, currently under way, to the second application.