An ink pinning assembly comprises a source of UV radiation suitable for pinning ink on a record medium. A radiation guide device has an inlet facing the source and an outlet through which radiation is emitted towards a record medium, in use, the length of the inlet being greater that the length of the radiation source. The radiation guide device has a substantially rectangular or square wall in plan surrounding a cavity extending between the inlet and outlet, the internal surface of the wall being reflective to the pinning radiation so that pinning radiation with a substantial uniform intensity is emitted from the outlet.