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Detector systems 1) Anti-Compton spectrometers 2) Pair spectrometers 3) Crystal spheres, walls, complex set-ups of semiconductor and scintillation detectors.

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Presentation on theme: "Detector systems 1) Anti-Compton spectrometers 2) Pair spectrometers 3) Crystal spheres, walls, complex set-ups of semiconductor and scintillation detectors."— Presentation transcript:

1 Detector systems 1) Anti-Compton spectrometers 2) Pair spectrometers 3) Crystal spheres, walls, complex set-ups of semiconductor and scintillation detectors 4) PET chambers Progress of gamma ray measurement: Comparison of measurements by one NaI(Tl) at 1963 and by set-up EUROGAM II (1994), taken from N. Poenaru, N. Greiner: Experimental Techniques in Nuclear Physics PET chamber at „Cyclotron BioMedical de Caen“ WWW pages of this device Photon spectrometer TAPS

2 Anticompton spectrometer HPGe detector with anticompton BGO shielding ( N. Poenaru, N. Greiner: Experi- mental Techniques in Nuclear Physics HPGe detector surrounded by scintillation detector (NaI(Tl), BGO) HPGe – high energy resolution Scintillation detector – high detection efficiency of Compton scattered photons Strong suppression of Compton background and escape peaks up to one order Photons after scattering → lower energies → higher probability of photo effect Asymmetrical position of HPGe detector inside NaI(Tl) or BGO detector is advantage Distance in which given fraction of scattered photons is absorbed at BGO Monte Carlo simulation

3 Pair spectrometer HPGe surrounded by scintillator (NaI(Tl), BGO) Coincidence of HPGe and 2 × 511 keV at scintillator Suppression of all, exclude double escape peaks Summation spectrometer Again combination of more detectors – often HPGe and scintillation detectors Sum makes possible to increase intensity of full absorption peak without marked downgrade of energy resolution Spectrometer consisted of HPGe surrounded by scintillation detector can work at anticompton, pair and summation modes Strong background suppression, possible only for lines with high enough energy → high enough probability of pair production Usage of inside geometry of source placement for cascade studies Simple, anticompton and pair spectrum of anticompton spectrometer at NPI ASCR

4 Crystal spheres for nuclear structure studies Studies of very rare phenomena, high energies of nuclear excitation, high angular momenta, long cascades, superdeformed states, giant resonances, exotic nuclei First generation ( eighties) : HPGE detectors with anticompton shielding, BGO set-ups, combination of semiconductor and scintillation detectors TESSA3 (UK), Chateau de Cristal (France), OSIRIS (SRN), NORDBALL (Denmark) Superdeformed band discovery I < 0,01, cascades up to 20 transitions Second generation (nineties): Way to modular, flexible nomad set-ups, work on more accelerators Detector set-up EUROGAM II Usage of semiconductor (HPGE) with BGO shielding (efficiency up to ε F = 10 %) ( tenths, hundreds of detectors) Efficiency ε F, Peak/Compton, resolution ΔE/E influence of Doppler shift – dominates at ΔE/E

5 from GAMMASPHERE HPGe detectors with BGO shielding, 4π geometry from EUROGAM I, II, EUROBALL III, IV USA –LBNL, ANL, Europa – Daresbury, Heidelberg, Darmstadt,... Some photos of Set-up GAMMASPHERE real and also presentation at film Hulk WWW pages of experiment Some photos of set-up EUROGAM and EUROBALL WWW pages of experiments

6 Scintillation „walls“ for high energy physics TAPS 384 BaF 2 detectors CLEO II 8000 CsI(Tl) detectors – usage of silicon photo diods -Cornell Electron-positron Storage Ring (CESR) Heidelberg/Darmstadt – 162 NaI(Tl), SLAC-DESY – 672 NaI(Tl) elmg calorimeters Detection of electromagnetic showers – identification of high energy photons Crystals of CsI(Tl) - spectrometer CLEO II 1)Thin plastic detector – identification of charged particles 2)Time of flight – separation of fast particles 3)Pulse shape analysis (BaF 2 has two components of light emission) TAPS worked at GSI Darmstadt, KVI Groningen, GANIL Caen, CERN, MAMI Mainz, Bon Detection of photons from hundreds keV up to tenth GeV produced directly or by decay of particles (π 0, η, ω, φ) Crystal length 250 mm, diameter 59 mm Block ofBaF2 crystals - spectrometer TAPS

7 Electromagnetic calorimeter of LHC experiment ALICE: photon spectrometer PHOS Photon spectrometer TAPS at GSI Darmstadt and at KVI Groningen Crystals of PbWO 4 : 15X 0 → 14 cm, R 0 ~ 2 cm Whole area: ~ 8 m 2 Optimized for E γ ~ 0,5 GeV – 10 GeV sizes: l = 18 cm S = 2,2×2,2 cm 2 Crystals of PbWO 4 are ready for PHOS

8 PET chambers for lékařskou diagnostiku Detectors record coincidences of annihilation quantum pairs 511 keV Positron emission tomography (PET) makes possible to obtain 3D pictures of patient tissues From hundreds up to thousands pair detectors Positron + electron – annihilation in the rest → two annihilation quanta with energy 511 keV flight in opposite directions Annihilation γ 1 (511 keV) γ 2 (511 keV) Two coordinates – position of photon detection Third coordinate – determination from detection time difference for photon pair Example: Standard chamber of HR+Siemens at „Cyclotron BioMedical de Caen: 576 crystals, space resolution 4,5 a 3,6 mm


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