Development of a precise hadron calorimeter

For the ZEUS detector, which is presently under construction, a prototype of the forward calorimeter was built and its performance was investigated. All measuremen were performed with the test beams of the accelerators PS and SPS at CERN in Geneva. Hadrons, electrons and muons we available in an energy range from 0.5 to 100 GeV. The calorimeter prototype consists of 16 towers with 20 cmx20 cross-section. Each tower is longitudinally segmented in a electromagnetic section with 25 cm length and two hadronic sections, each with 63 cm length. All towers are built fro plates of depleted uranium of 3.3 mm thickness and scintillator plates with 2.6 mm thickness. In previous measurements these values were determined to be the best choice, in order to obtain the best energy resolution. The light readout was performed by wavelength shifters (PMMA, doped with Y-7) and photomultiplier tubes. Some important results of these measurements are: The design energy resolution 35%/√E+2% for hadrons and 18%/√E+2% for electrons has been achieved. The e/h-ratio w determined to be 1.00±0.01. The linearity of the calorimeter was found to be better than 2% in the investigated energy range. The nonuniformity of the wavelength shifter was improved to be better than 2% by reflectors with absorbing patterns printed on it. The deviations from uniformity at the boundaries between calorimeter modules were reduced to 7% by insertion of lea sheets in the gap. A big advantage was the possibility to use the natural radioactivity of the uranium for calibrati purposes. (orig.)