L. La Rotonda

The electromagnetic calorimeter of the NOMAD experiment

Abstract A description is given of the NOMAD electromagnetic calorimeter, consisting of 875 lead-glass counters read out by two-stage photomultipliers and a low noise electronic chain. The detector operates in a 0.4 T magnetic field transverse to the counter axis. The paper discusses the design criteria, the lead-glass characteristics, the properties of the read out chain and provides a summary of the calorimeter performance.

A study of the transverse fluctuations of hadronic showers in the NOMAD electromagnetic calorimeter

Abstract The transverse shower shape of the energy deposition of hadrons in the NOMAD lead glass calorimeter has been studied by exposing a prototype of this calorimeter to pion test beams of various momenta and incident angles. Large event-to-event fluctuations in the shower shape and significant energy depositions far from the incident hadron were observed making it difficult to associate all the deposited energy to the incident hadron that caused it. Since in the NOMAD detector the momenta of charged hadrons are measured by a magnetic spectrometer, such an association is necessary to be able to subtract from the calorimeter all the energy caused by the observed charged hadrons in order to avoid double counting. Probability functions based on the measurements have been developed to describe fluctuations of the lateral shower shape. Starting from these functions, an algorithm is developed for identifying the energy deposition associated to a charged hadron. The identification and separation of overlapping showers based on these functions is also discussed. The Monte Carlo simulation of the calorimeter reproduces the test beam data well therefore allowing the application of the algorithm at angles and momenta not studied in the test beam.

Test beam performance of the electromagnetic calorimeter of the NOMAD experiment

Abstract Test beam results of the NOMAD electromagnetic calorimeter are presented showing linearity, signal uniformity, energy and position resolution measured in an electron beam. Tests were also performed placing the calorimeter in a magnetic field of 0.4 T. Results on the π rejection obtained using a combined measurement of preshower/electromagnetic calorimeter are found to be in good agreement with the project expectations. Finally the calorimeter response to the muons is discussed.

Contributions of Cherenkov light to the signals from lead tungstate crystals

Results are presented of detailed measurements of the signals generated by high-energy electrons and muons in lead tungstate crystals. A significant fraction of the light produced in these crystals and detected by photomultiplier tubes is the result of the Cherenkov mechanism. This is concluded from the angular dependence of the signals and from their time structure. Depending on the orientation of the crystals and on the particle type, Cherenkov light may account for up to 15% of the total signals. r 2007 Elsevier B.V. All rights reserved. PACS: 29.40.Ka; 29.40.Mc; 29.40.Vj

A HIGH STABILITY LIGHT EMITTING DIODE SYSTEM FOR MONITORING LEAD GLASS ELECTROMAGNETIC CALORIMETERS

Abstract We have designed, built and tested a high stability system based on blue light emitting diodes (LED) and current pulse generators for calibration and monitoring of lead-glass calorimeters. This apparatus is presently being used for the electromagnetic calorimeter of the WA96 (NOMAD) experiment at CERN. The system was developed to minimize the sensitivity to temperature variations, different loadings, and ageing effects. Tests performed both in the laboratory and in the experiment showed that the response of the lead-glass calorimeter modules to LED light pulses could be kept within the precision of ±1% for periods of several months.

Measurement of the contribution of neutrons to hadron calorimeter signals

The contributions of neutrons to hadronic signals from the DREAM calorimeter are measured by analyzing the time structure of these signals. The neutrons, which mainly originate from the evaporation stage of nuclear breakup in the hadronic shower development process, contribute through elastic scattering off protons in the plastic scintillating fibers which provide the dE=dx information in this calorimeter. This contribution is characterized by an exponential tail in the pulse shape, with a time constant of � 25 ns. The relative contribution of neutrons to the signals increases with the distance from the shower axis. As expected, the neutrons do not contribute to the DREAM Cherenkov signals. r 2007 Elsevier B.V. All rights reserved. PACS: 29.40.Ka; 29.40.Mc; 29.40.Vj

Parameterization of e and γ initiated showers in the NOMAD lead-glass calorimeter

Abstract A description of the response of the NOMAD electromagnetic calorimeter to electrons and photons is discussed. In particular, the dependence of the two-dimensional shower shape on the angle and energy of the incident particle is parametrized by analytical functions. Some applications to the neutrino event reconstruction are also reported.

Low-cost and high-reliability control and data acquisition system for the operation of a solar plant with a long-term thermal storage capability

SummaryA solar plant with a long-term thermal storage capability has been built up at the University of Calabria. In this paper it is described the control and data acquisition system for the operation of the plant. Some considerations on the controls schedule of the plant are developed.RiassuntoSi descrive un sistema di controllo e acquisizione dati a basso costo ed elevata affidabilità per la gestione di un impianto solare dotato di accumulo di calore a lungo termine.

A test of dual readout with tiles for calorimetry

A small detector (6 radiation lenghts in total) divided into two sections of four times lead-quartz-scintillator tiles, each with a separate readout for Cerenkov and scintillation light has been tested. The results for high energy muons and electrons are presented. The measured Cerenkov light yield for electrons is about 50 C.p.e. per deposited GeV.

Analysis of the managing conditions of a linear-collector network of a solar power plant

SummaryA model has been solved to evaluate the influence of different control options on the performances of a linear-collector solar power plant. The results represent a basis for the choice between the different options.RiassuntoÈ stato risolto un modello fisico-matematico per determinare gli effetti sulle prestazioni di una centrale solare a collettori lineari di differenti modalità di controllo. I risultati rappresentano un contributo al problema della scelta tra differenti criteri di gestione dell’impianto.