Shashlyk electromagnetic calorimeter modules with an energy resolution of about 3%/ E (GeV) for 50−1000 MeV photons has been developed, and a prototype tested. Details of these improved modules, including mechanical construction, selection of wave shifting fibers and photo-detectors, and development of a new scintillator with improved optical and mechanical properties are described. How the modules will perform in a large calorimeter was determined from prototype measurements. The experimentally determined characteristics of the calorimeter prototype show energy resolution of σ E /E = (1.96 ± 0.1)% ⊕ (2.74 ± 0.05)%/ √ E, time resolution of σ T = (72 ± 4)/ √ E ⊕ (14 ± 2)/E (ps), where photon energy E is given in GeV units and ⊕ means a quadratic summation. A punch-through inefficiency of photon detection was measured to be ǫ ≈ 5 × 10 −5 (Θ beam > 5 mrad).

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Surface-barrier structures based on thin high-purity GaAs epilayers with a polyethylene converter were studied as fast neutron detectors. A continuous Schottky barrier with a large area of 5 × 5 mm 2 to the high-purity GaAs epilayers was fabricated using a Pt/TiN/Au metallization system. Results of measurement of electric parameters and α-particle spectra are presented. The fast neutron spectra from the 241 Am-Be source measured by the recoil proton method for various thicknesses of the polyethylene converter and various operating biases are shown as well. The proposed detectors have shown high neutron detection efficiency of 1.30 • 10 −3 puls./neutr. and an acceptable signal-to-background ratio (at level of 50) as well as the capability to operate efficiently without any external bias.

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