This work intends to give the state-of-the-art of our knowledge of the
performance of LEKIDs at millimetre wavelengths (from 80 to 180~GHz). We
evaluate their optical sensitivity under typical background conditions and
their interaction with ionising particles. Two LEKID arrays, originally
designed for ground-based applications and composed of a few hundred pixels
each, operate at a central frequency of 100, and 150~GHz (Δν/ν
about 0.3). Their sensitivities have been characterised in the laboratory using
a dedicated closed-circle 100~mK dilution cryostat and a sky simulator,
allowing for the reproduction of realistic, space-like observation conditions.
The impact of cosmic rays has been evaluated by exposing the LEKID arrays to
alpha particles (241Am) and X sources (109Cd) with a readout sampling
frequency similar to the ones used for Planck HFI (about 200~Hz), and also with
a high resolution sampling level (up to 2~MHz) in order to better characterise
and interpret the observed glitches. In parallel, we have developed an
analytical model to rescale the results to what would be observed by such a
LEKID array at the second Lagrangian point.Comment: 7 pages, 2 tables, 13 figure