Nuclear Instruments and Methods in Physics Research最新文献

A review is presented of the effects of radiation damage on silicon detectors, which are being considered for high energy physics applications. The main degradation in performance is an increase in leakage current, which can be well characterized by an empirical damage constant for many radiations. A summary of data on damage constants is given. A brief discussion of annealing effects in terms of band gap level changes is included.

We outline briefly the general structure of the Aleph detector, to place in context conceptually and physically the electromagnetic calorimeter. The calorimeter is then described, emphasizing the read-out mechanical and electronic structure, which allows adequate granularity; three layers of towers 3×3 cm², approximately 210 000 pieces of analog information. We discuss the basic properties of such apparatus with the results of tests performed on a prototype. We emphasize the peculiarities of operating such a wire gas calorimeter in a strong magnetic field parallel to the wires.

The central detector of the DELPHI (LEP) experiment will be a time projection chamber working at a pressure of one atmosphere in a 1.2 T magnetic field. We will describe the present conception of this detector and the prototype work which can change and improve the final design.

The use of streamer tubes in the construction of electromagnetic and hadron calorimeters has been considered by several groups within LEP Collaborations. The results of various tests on these calorimeters is reviewed and the possibility to have an integrated muon-hadron detection system in hadron calorimeters with streamer tubes is discussed, together with possible applications when high energy and high rates are concerned.

A giant argon bubble chamber could be a suitable detector to investigate the decay modes of nucleons in an unbiased way. We are investigating the possibility of operating such a chamber with a track sensitive duty cycle of up to ∼ 50%. A small and not very clean bubble chamber has been successfully operated in an expanded pressure stabilized mode with a duty cycle of 10%. A tentative design of a 3000 m³ argon bubble chamber is discussed.

Some of the recent work on high resolution silicon strip detectors by the TU-Munich and MPI-Munich group is presented, in particular:

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  -investigation of the factors limiting the spatial resolution;

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  -use of silicon strip detectors as on-line triggers for the study of charmed particles in hadronic reactions;

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  -development of LSI (large scale integration) readout electronics for strip detectors.

Crystalline Bismuth Germanate (BGO) scintillates. Its high density and short radiation length make it very attractive for the construction of high resolution compact electromagnetic calorimeters. The present status of development, performance and production methods will be discussed. New developments in photodiode readout allow for operation in magnetic fields. Some projects will be mentioned.

The possibilities and limitations of holographic image recording in bubble chambers and streamer chambers are reviewed. After a discussion of the relative merits of in-line and side band holography, I describe the results obtained so far both in small and large chambers. The experience from CERN experiment NA25 shows that holography is a useful and practical method of recording bubble chamber images.

A two kiloton liquid argon detector in an underground laboratory would be the ideal detector for the study of solar neutrinos and of proton decay. The physics interest in such a device and the difficulties of construction are discussed. Basic design ideas for such a large detector are described.

Physics motivations for the use of argon as a new bubble chamber liquid are discussed. Results, obtained from a 2.7 1 argon detector in SPS and SC beams at CERN, comprise its track sensitivity to ionizing particles and to a laser beam in the bubble chamber mode, its use as a calorimeter through the collection of free charges in an electric field and the recording of the scintillation light produced by ionizing particles. Various interference phenomena during the simultaneous use of the hybrid properties, as well as purity requirements on the liquid are discussed. Furthermore, nitrogen and argon/nitrogen mixtures were investigated. Applications of our technique for neutrino experiments at TeV accelerators and as vertex detectors are briefly outlined. In-line holography, successfully tested in BEBC, could simplify the optical track recording and improve the resolution in very large detectors.