  The NA62 experiment at CERN utilises a differential Cherenkov counter with
achromatic ring focus (CEDAR) for tagging kaons within an unseparated
monochromatic beam of charged hadrons. The CEDAR-H detector was developed to
minimise the amount of material in the path of the beam by using hydrogen gas
as the radiator medium. The detector was shown to satisfy the kaon tagging
requirements in a test-beam before installation and commissioning at the
experiment. The CEDAR-H performance was measured using NA62 data collected in
2023.
