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The development of a Gas Electron Multiplier (GEM) readout as an option for the TPC of the near detector of the T2K neutrino experiment is presented. The low track density and the wide range in polar angle of particles produced by neutrino interactions drive the initial choice of relatively large squared pads (8 mm) for the performance study. The physics requirements [T2K ND280 Conceptual Design Report, http://dpnc.unige.ch:8080/nu/Members/nabgrall/t2kge/t2kge_doc/cdr.pdf ] are a momentum resolution better than 10 % at 1 GeV/c and a 3 σ dE/dx separation between muons and electrons. Micro-pattern Gas Detectors (MPGDs) such as GEMs or Micromegas show several beneficial features compared to the traditional Multi-Wire Proportional Chambers. They have been tested in the HARP TPC environment at CERN. Preliminary results form the GEM tests are reported here.

A fast level-1 trigger processor for the Active Lead Ring calorimeter (ALR) and for the Very Small Angle Tagger (VSAT) of the L3 detector has been constructed and implemented. The main application is the study of single tagged two-photon collision processes at LEP II. Particular care has been taken to preserve the timing characteristics of the signal in order to allow bunch tagging in the multi-bunch mode of LEP.

The L3 central tracking detector has been in operation since the start-up of LEP (Large Electron Positron collider) in 1989. This detector consists of a Time Expansion Chamber (TEC), a layer of Plastic Scintillating Fibers and a Z-chamber. The TEC gives a high spatial resolution and an excellent multi-track reconstruction capability. The fibers are designed to calibrate the drift velocity with high precision. The Z-Chamber provides TEC with accurate information about the z-coordinates of the tracks. A description of the design and the infrastructure of these three detectors, including the readout and data acquisition system, is given. The performance of the detectors during the 1990 and 1991 LEP running periods is presented.

A Fastbus ADC and TDC module has been developed for the trigger of the L3 experiment. It provides fast and precise integration of successive pairs of charges derived from the charge division wires of the central tracking chamber, as well as a measurement of their drift times. The minimum separation time between digitizations is 170 ns. The charges are measured with a precision of 1 pC up to charges of 600 pC. The drift times are measured in 50 ns time bins. A system including 60 modules provides data allowing the reconstruction of charged particle tracks in three dimensions. This information is used in background rejection algorithms of the second and third level triggers.

A first-level charged particle trigger based on parallel processing and look-up tables has been developed for the L3 detector. It processes analog signals generated by the central tracking detector, a drift chamber with axial wires. The trigger decision is made on the total number of tracks, the number of coplanar pairs of tracks, or on more complicated topologies found in the projection normal to the beam axis. The system is very flexible and can be adjusted to a wide range of background conditions and tracking chamber efficiencies.