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