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 NuclearPhysics
PET chamber at „CyclotronBioMedical de Caen“ WWW pages of thisdevice
Photon spectrometer TAPS
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 resolutionScintillation 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 detectorinside NaI(Tl) or BGO detector is advantage
Distance in which given fraction of scattered
photons is absorbed at BGO
Monte Carlosimulation
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 markeddowngrade 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 andpair spectrum of anticomptonspectrometer at NPI ASCR
Crystal spheres for nuclear structure studies
Studies of very rare phenomena, high energies of nuclear excitation, highangular momenta, long cascades, superdeformed states, giant resonances, exotic nuclei
First generation ( eighties) :
6 -21 HPGE detectors with anticompton shielding, BGO set-ups, combinationof 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 εF = 10 %)
( tenths, hundreds of detectors)
Efficiency εF, Peak/Compton, resolution ΔE/E
influence of Doppler shift – dominates at ΔE/E
from 1995 - GAMMASPHERE - 70 -110 HPGe detectors with BGO shielding, 4π geometry
from 1992 - EUROGAM I, II, EUROBALL III, IV - 2002
USA –LBNL, ANL,
Europa – Daresbury, Heidelberg, Darmstadt, ...
Some photos ofSet-upGAMMASPHERE
real and also presentationat film Hulk
WWW pages ofexperiment
Some photos ofset-up EUROGAMand EUROBALL
WWW pages of experiments
Scintillation „walls“ for high energy physics
1991 - TAPS 384 BaF2 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 particles2) Time of flight – separation of fast particles 3) Pulse shape analysis (BaF2 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 ofparticles (π0, η, ω, φ)
Crystal length 250 mm, diameter 59 mm
Block ofBaF2 crystals - spectrometer TAPS
Electromagnetic calorimeter of LHC experiment ALICE:photon spectrometer PHOS
Photon spectrometer TAPS at GSI Darmstadt and at KVI Groningen
Crystals of PbWO4: 15X0 → 14 cm, R0 ~ 2 cm
Whole area: ~ 8 m2
Optimized for Eγ ~ 0,5 GeV – 10 GeV
sizes: l = 18 cm S = 2,2×2,2 cm2
Crystals of PbWO4 are ready for PHOS
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
γ1 (511 keV)
γ2 (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