The Water Cherenkov Test Experiment (WCTE) will be installed in CERN’s recently upgraded T9
“Test Beam” Area in Autumn 2024. It has three goals: to prototype photosensor and calibration
systems for Hyper-Kamiokande, to develop new calibration and reconstruction methods for water
Cherenkov detectors and to measure lepton and hadron scattering on water. The collaboration
performed a 3-week-long beam test in July 2023. It uses newly developed aerogel Cherenkov
threshold counters (ACTs) to perform an efficient separation of pions from muons in the sub-GeV
range, which had not been done before. Additionally, a new compact tagged photon beamline was
developed, composed of a Neodymium (N52) Halbach array permanent magnet and a hodoscope
array placed downstream of the magnet. The combination of the ACTs and tagged photon beamline
provides sub-GeV p, e, pi, mu and gamma test beams. Using this setup, the collaboration was able
to estimate the beam flux of CERN’s T9 beam.

