DESIGN AND TEST OF A FORWARD NEUTRON CALORIMETER FOR THE ZEUS EXPERIMENT

A lead scintillator sandwich sampling calorimeter has been installed i n the HERA tunnel 105.6 m from the central ZEUS detector in the proton beam direction, It is designed to measure the energy and scattering a ngle of neutrons produced in charge exchange ep collisions. Before ins tallation the calorimeter was tested and calibrated in the H6 beam at CERN where 120 GeV electrons, muons, pions and protons were made incid ent on the calorimeter. In addition, the spectrum of fast neutrons fro m charge exchange proton-incite collisions was measured, The design an d construction of the calorimeter is described, and the results of the CERN test reported. Special attention is paid to the measurement of s hower position, shower width, and the separation of electromagnetic sh owers from hadronic showers. The overall energy scale as determined fr om the energy spectrum of charge exchange neutrons is compared to that obtained from direct beam hadrons.