Commercial fusion power plants will require strong magnetic fields that can only be achieved using state-of-the-art high temperature superconductors in the form of REBCO coated conductors. In operation in a fusion machine, the magnet windings will be exposed to fast neutrons that are known to adversely affect the superconducting properties of REBCO compounds. However, very little is known about how these materials will perform when they are irradiated at cryogenic temperatures. Here we use a bespoke in-situ test rig to show that helium ion irradiation produces a similar degradation in properties regardless of temperature, but room temperature annealing leads to substantial recovery in the properties of cold irradiated samples. We also report the first attempt at measuring the superconducting properties whilst the ion beam is incident on the sample, showing that the current that the superconductor can sustain is reduced by a factor of 3 when the beam is on.