The MASS (Multi-Aperture Scintillation Sensor) instrument consists of a 14-cm off-axis reflecting telescope and a detector unit which measures the scintillations of single stars in four concentric zones of the telescope pupil using photo-multipliers. Statistical analysis of these signals yields information of the vertical turbulence profile with a resolution of dh/h=0.5. We describe the instrument and present the results of its first field tests, including comparisons with DIMM seeing monitor and generalized SCIDAR. MASS will be used to obtain the extensive statistics of turbulence profiles at potential sites of future giant telescopes, as needed to predict the quality of adaptive seeing compensation.

DELPHI (DEtector with Lepton, Photon and Hadron Identication) is a detector for e + e physics, designed to provide high granularity o v er a 4 solid angle, allowing an eective particle identication. It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.(To be submitted to Nucl. Inst. and Meth.) ii

The spin density matrix elements for the 0 , K 0 (892) and produced in hadronic Z 0 decays are measured in the DELPHI detector. There is no evidence To be submitted to Physics Letters B ii

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