HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion induced collisions. Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and dense hadronic matter. The detector system is characterized by an 85 % azimuthal coverage over a polar angle interval from 18• to 85• , a single electron efficiency of 50 % and a vector meson mass resolution of 2.5 %. Identification of pions, kaons and protons is achieved combining time-of-flight and energy loss measurements over a large momentum range. This paper describes the main features and the performance of the detector system.

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Using high-resolution γ−ray spectroscopy, the terrestrial gamma radiation in all the predominant types of geological rock formations appearing in Cyprus was measured. Soil samples were collected from each rock type, sealed in 1-litre plastic Marinelli beakers, and measured in the laboratory for 24 hours each. From the measured γ−ray spectra, activity concentrations were determined for 232 Th (range from 1.3 to 52.8 Bq kg −1 ), 238 U (from 0.9 to 90.3 Bq kg −1 ) and 40 K (from 13 to 894 Bq kg −1 ). Elemental concentrations mean values of (2.8 ± 0.7) ppm, (1.3 ± 0.3) ppm and (0.6 ± 0.1) % were extracted, for thorium, uranium and potassium, respectively. Absorbed dose rates in air outdoors were calculated to be in the range of 0.1−50 nGy h −1 , depending on the geological features, with an overall mean value of (14.7 ± 7.3) nGy h −1 . The corresponding effective dose rates per person outdoors were estimated to be between 0.1 and 61.4 µSv y −1 , assuming a 20% occupancy factor.

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