A Swimming Pool Hadron Calorimeter

A new type of hadron calorimeter is described which measures the energy of ahadronby detecting the Cherenkov light produced by the hadronic shower it initiates in a large tank of water. The device features large aperture with good uniformity, good energy containment, andmodest resolution at modest cost. The response was studied as a function of particle type and momentum. Resolution of 40% (RMS) has been achieved at 20 GeV.