  A mesoscopic hybrid Normal/ Superconducting (NS) ring is characterized by a
dense Andreev spectrum with a flux dependent minigap. We measure the linear
response to a high frequency flux, in a wide frequency range, with a multimode
superconducting resonator. We find that the current response contains, beside
the well known dissipation-less Josephson contribution, a large dissipative
component. At high frequency compared to the minigap and low temperature we
find that the dissipation is due to transitions above the minigap. In contrast,
at lower frequency there is range of temperature for which dissipation is
caused predominantly by the relaxation of the Andreev states' population.
