Cours de méca du point L1 UJF

Subatomic particle detectors Johann Collot collot@in2p3.fr http://lpsc.in2p3.fr/collot UdG P. 1G eneral properties of detectorsA detector always has an active medium in which particlesinteract and generate signal carriers (ion-electron pairs, Signal photons, electron-hole pairs.) which are subsequently collectionparticlecollected to form an electronic signal. deviceexample 1 : ionization chambercharged A ctive medium particle scintillatorexample 2 : scintillating counterphotomultiplier converts light into electronic signalelectronic preamplifiersignalanode collectingionized electrons electronic charged reflector for signal particle photon collectionJohann Collot collot@in2p3.fr http://lpsc.in2p3.fr/collot UdG P. 2modes of detector operationt1C urrent mode : Measures current averaged over time interval T : It= it'dt'∫T t−Ti(t)This mode is used when only the average currentinduced by particle interactions is of interest orI (t) when the interaction rate is much too high.Examples : neutron flux detectors in nuclear reactors.A ctive dosimeters. B eam diagnostics. tPulse mode : The characteristics (time, amplitude..) of each pulse are individually i(t) measured. This mode is used when detecting individual particles is ofinterest. I t requires fast electronics.Examples : all kinds of particle detectors used in high energy physics.tt t t1 2 3Johann Collot collot@in2p3.fr http ...