The ANTARES collaboration is building a deep sea neutrino telescope in the Mediterranean Sea. This detector will cover a sensitive area of typically 0.1 km 2 and will be equipped with about 1000 optical modules. Each of these optical modules consists of a large area photomultiplier and its associated electronics housed in a pressure resistant glass sphere. The design of the ANTARES optical module, which is a key element of the detector, has been finalized following extensive R&D studies and is reviewed here in detail.

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The ANTARES neutrino telescope is a large photomultiplier array designed to detect neutrino-induced upward-going muons by their Cherenkov radiation. Understanding the absorption and scattering of light in the deep Mediterranean is fundamental to optimising the design and performance of the detector. This paper presents measurements of blue and UV light transmission at the ANTARES site taken between 1997 and 2000. The derived values for the scattering length and the angular distribution of particulate scattering were found to be highly correlated, and results are therefore presented in terms of an absorption length λ abs and an effective scattering length λ eff sct . The values for blue (UV) light are found to be λ abs ≃ 60(26) m, λ eff sct ≃ 265(122) m, with significant (∼15%) time variability. Finally, the results of ANTARES simulations showing the effect of these water properties on the anticipated performance of the detector are presented.

Abstract. We present the current status of CRESST (Cryogenic Rare Event Search using Superconducting Thermometers) project and new results concerning detector development. The basic technique involved is to search for WIMPs by the measurement of non-thermal phonons, as created by WIMP-induced nuclear recoils. Combined with our newly developed method for the simultaneous measurement of scintillation light, strong background discrimination is possible, resulting in a substantial increase in WIMP detection sensitivity. CRESST and the Dark Matter ProblemAfter a long period of development, cryogenic detectors are now coming on line and deliver significant results in particle-astrophysics and weak interactions. The goal of the CRESST project is the direct detection of elementary particle dark matter and the elucidation of its nature. Particle physics provides a well motivated dark matter candidate through the lightest supersymmetric (SUSY) particle, the 'neutralino' and one can find candidates in a wide mass range [1]. Generically, such particles are called WIMPS (Weakly Interacting Massive Particles). WIMPS are expected to interact with ordinary matter by elastic scattering on nuclei. Conventional methods for direct detection rely on the ionization or scintillation caused by the recoiling nucleus. This leads to limitations connected with the relatively high energy involved in producing electron-hole pairs. Cryogenic detectors use the much lower energy excitations, such as phonons. Since the principal physical effect of a WIMP nuclear recoil is the generation of phonons, cryogenic calorimeters are well suited for WIMP detection. Further, when this technology is combined with charge or light detection the resulting background suppression leads to a powerful technique to search for the rare nuclear recoils.The detectors developed by the CRESST collaboration consist of a dielectric target-crystal with a small superconducting film evaporated onto the surface. When this film is held at a temperature in the middle of its superconducting to normal conducting phase transition, it functions as a highly sensitive thermometer. The detectors presently employed in Gran Sasso use tungsten (W) films and sapphire (Al 2 O 3 ) absorbers, running near 15 mK. The technique can 2 J. Jochum CRESST collabroation also be applied to a variety of other materials. The small change in temperature of the superconducting film resulting from an energy deposit in the target leads to a relatively large change in the film's resistance. This change in resistance is measured with a SQUID. A small separate detector of the same type is used to see the light emitted when the target is a scintillating crystal. Present Status of CRESSTThe task set for the first stage of CRESST was to show the operation of four 262 g sapphire detectors, with a threshold of 500 eV under low background conditions. Meeting this goal involved the setting up of a low background, large volume, cryogenic installation and the development of massive, low background detectors with low ...