  Many nuclear reactions used to create radioactive isotopes for nuclear
research produce, in addition to the isotope of interest, many contaminants,
which are often produced in much larger amounts than the isotope of interest.
Many installations using the ISOL approach are therefore equipped with
high-resolution mass separators to remove at least isotopes with a different
mass number. In the present paper, we present the results of the commissioning
of the DESIR HRS presently under development at LP2I Bordeaux (formerly CENBG).
Optical aberrations are corrected up to 3rd order and a mass resolution of
M/$\Delta$M of 25000 is reached with a transmission of about 70% for a 133Cs+
beam at 25 keV.
