G. Kalkanis

The Barrel Ring Imaging Cherenkov counter of DELPHI

Abstract A short explanation is given of the Barrel Ring Imaging CHerenkov (BRICH) detector and its performance. We discuss in brief some of the requirements to run this detector. Special attention is paid to the functioning of the Cherenkov photon detector — a photosensitive gas-filled drift chamber where the photoelectrons drift to a MWPC of special construction. We illustrate the BRICH performance with some preliminary results.

Quantum mechanics: a systemic component of the modern physics paradigm

† Professor, Director of Science, Technology and Environment Laboratory. We consider that physics education has to meet today’s demand for a qualitative approach to the QM worldview. An effective answer to the corresponding instructional problem might allow the basic ideas of QM to be accessed at a very early stage of physics education. This fact (i) might prevent the introduction of the scientific content of modern physics in ways that provoke serious misconceptions, (ii) might enable students who are not willing to attend specialized science training to reach the core ideas of a theory that introduced radical modifications into human thought and (iii) might lead students to form a unified image of microscopic and macroscopic phenomena, compatible with the scientific one. We believe that an educational strategy aiming at a qualitative approach to QM needs a stable

NESTOR: A Neutrino particle astrophysics underwater laboratory for the Mediterranean

Abstract An underwater neutrino astrophysics laboratory, to be located in the international waters off the Southwest of Greece, near the town of Pylos is now under construction. In the last two years a group of physicists from Greece and Russia have carried out two demonstration experiments in 4km deep water, counting muons and verifying the adequacy of the deep sea site. Plans are presented for a 100, 000 m 2 high energy neutrino detector composed of a hexagon of hexagonal towers, with 1176 optical detector units. A progress report is given and the physics potential of a siggle tower with 168 phototubes (currently under construction) is described.

A search for nucleon decay with multiple muon decays

Abstract A search was made for nucleon decays which result in multiple delayed muon decays using the HPW water Cerenkov detector. No contained events were found, which is consistent with the expected neutrino background of 0.7±0.2 events. Lower lifetime limits are calculated for eleven proton decay modes and five bound neutron decay modes, ranging from 2×10 30 yr to 1×10 31 yr.

The calibration system for the DELPHI Barrel RICH detector

Abstract We have designed, constructed and installed a system that makes an accurate 3D map of the electron drift velocity and measures the space-charge distorting effects in the TPCs of the DELPHI Barrel RICH detector. Details of the design considerations, construction and production are given.

The inverse power law model for the lifetime of a mylar-polyurethane laminated dc hv insulating structure

Abstract Results of an accelerated test on the lifetime of a mylar-polyurethane laminated dc high voltage insulating structure are reported. This structure consists of mylar ribbons placed side by side in a number of layers, staggered and glued together with a polyurethane adhesive. The lifetime until breakdown as a function of extremely high values of voltage stress is measured and represented by a mathematical model, the inverse power law model with a 2-parameter Weibull lifetime distribution. The statistical treatment of the data — either by graphical or by analytical methods — allowed us to estimate the lifetime distribution and confidence bounds for any required normal voltage stress. The laminated structure under consideration is, according to the analysis, a very reliable dc hv insulating material, with a very good life performance according to the inverse power law model, and with an exponent of voltage stress equal to 6. A large insulator of cylindrical shape with this kind of laminated structure can be constructed by winding helically a mylar ribbon in a number of layers.

Elementary School teacher preparation for teaching physics - the Greek approach

Greek universities recently took responsibility for the preparation of future Elementary School teachers. Aspects of the four-year curriculum programme of the University of Athens in Physics Education are presented here and may help those planning similar programmes. Results so far have been fruitful enough for the Greek Ministry of Education to ask the universities to retrain present Elementary School teachers who attended the old-fashioned two-year studies.

A calculation of the surface charges and the electric field outside steady current carrying conductors

The surface charges and the electric field outside steady current carrying conductors has been for long the subject of many investigations. It turns out that both quantities strongly depend on the configuration of the circuit. In this work an attempt to distinguish and clarify the essential factors of this dependence is presented. To this end, a simple, three-dimensional model is proposed and quantitative results are derived which are in agreement with experimental data. In addition, the existence of electric fields outside current carrying conductors and their behaviour can be easily demonstrated in class by recourse to the model, with the help of a computer program, thus avoiding inconvenient or dangerous experimental set-ups. Zusammenfassung. Die Fl¨ achenladung und das elektrische Feld auserhalb eines gleichstromtragenden Leiters ist seit langem das Thema vieler Untersuchungen gewesen. Es zeigt sich, dasbeide Grstark von der Struktur des Stomkreises abhIn diesem Werk wird der Versuch, die wesentlichen Faktoren dieser Abhzu unterscheiden und zu erkl¨ aren, presentiert. Zu diesem Zweck wird ein einfaches dreidimensionales Modell vorgeschlagen und quantitative Ergebnisse, die in ¨ Ubereinstimmung mit experimentellen Daten stehen, werden abgeleitet. Zus¨ kann die Existenz elektrischer Felder auserhalb stromtragender Leiter und ihr Verhalten durch dieses Modell und mit Hilfe eines Computerprogramms einfach im Klassenzimmer demonstriert werden, so dasumst ¨ andliche und gef¨ ahrliche Experimentaufbauten vermieden werden k¨ onnen.

Recent results from the DELPHI barrel ring imaging Cherenkov counter

The DELPHI detector installed in the LEP (Large Electron-Positron Collider) is equipped with RICH (ring imaging Cherenkov) counters. The barrel part incorporates a liquid (C/sub 6/F/sub 14/) and a gaseous (C/sub 5/F/sub 12/) radiator, providing particle identification up to 20 GeV/c. The Cherenkov photons of both radiators are detected by TPC (time projection chamber)-like photon detectors. The drift gas (75% CH/sub 4/+25% C/sub 2/H/sub 6/) is doped with TMAE (tetrakis-dimethylamine-ethylene) by which the ultraviolet Cherenkov photons are converted into single free photoelectrons. These are drifted towards multiwire proportional chambers at the end of the drift tubes, and the space coordinates of the conversion point are determined. One half of the barrel RICH is now equipped with drift tubes and has provided results from the liquid radiator since spring 1990. The gas radiator has been tested with C/sub 2/F/sub 6/ as a preliminary filling since August 1990. The data obtained demonstrate the good particle identification potential. For the liquid radiator, the number of detected photons per ring in hadron jets is N=8, whereas for muon pairs (single tracks) N=10 has been obtained. For the gas radiator, 2.1 photons per track were observed, which demonstrates good functioning of the focussing mirrors. >

Tests of the DELPHI Barrel RICH electrical hv insulator

Abstract The expected lifetime of a cylindrical high voltage test insulator is estimated from accelerated dc high voltage test results; a method to evaluate the failure probability and the hv lifetime of insulators with similar geometry and insulating material is described; the failure probability and the expected lifetime of the electrical insulator of the planned DELPHI Barrel RICH (Ring Imaging CHerenkov) detector are evaluated. The insulating structure consists of mylar ribbons wound helically in layers, staggered and glued together with a polyurethane adhesive.