Hodoscope spectrometer for high-energy gamma-ray detection

A scintillation hodoscope spectrometer developed at the Institute of High-Energy Physics is described. This spectrometer makes it possible to measure simultaneously the coordinates of several high-energy gamm-quanta (with an accuracy of about 2 mm) and their energies (5-10%). The instrument contains 648 scintillation counters assembled in a plane and interlayed with steel converters. The spectrometer working area is equal to about 1 m2. The pulse amplitude analysis is carried out for each counter by a system of amplitude-to-code converters with 4096 discrimination levels. The information is analyzed and processed by an on-line computer at a rate of 106 bits/s. The gamma-quanta coordinates are determined by the gravity centre of the shower energy release in the scintillators. To improve the reproduction of events the coordinates are measured in three projections turned through 120 deg. The total thickness of the spectrometer over the beam amounts to 20 radiation-length units of steel. This ensures the total absorption of gamma-quanta and electrons with energy up to 1000 GeV. The spectrometer allows to register more than 90% of energy up to 1000 GeV. The spectrometer operating characteristics and its operating experience during experiments with 70 GeV beams at the Institute of High-Energy Physics are described