  Measurements of proton-nucleus scattering and high resolution
neutrino-nucleus interaction imaging are key to reduce neutrino oscillation
systematic uncertainties in future experiments. A High Pressure Time Projection
Chamber (HPTPC) prototype has been constructed and operated at Royal Holloway
University of London and CERN as a first step in the development of a HPTPC
capable of performing these measurements as part of a future long-baseline
neutrino oscillation experiment such as the Deep Underground Neutrino
Experiment. In this paper we describe the design and operation of the prototype
HPTPC with an argon based gas mixture. We report on the successful hybrid
charge and optical readout, using four CCD cameras, of signals from Am-241
sources.
