Transcript Detector systems

Detector systems
1) Anti-Compton spectrometers
2) Pair spectrometers
3) Crystal spheres, walls, complex set-ups
of semiconductor and scintillation detectors
4) PET chambers
PET chamber at „Cyclotron
BioMedical de Caen“
WWW pages of this
device
Photon spectrometer TAPS
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
Anticompton spectrometer
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
Monte Carlo
simulation
Distance in which given fraction of scattered photons
is absorbed at BGO
HPGe detector with anticompton BGO
shielding ( N. Poenaru, N. Greiner: Experimental Techniques in Nuclear Physics
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
Strong background suppression, possible only for
lines with high enough energy → high enough
probability of pair production
Summation spectrometer
Simple, anticompton and
pair spectrum of anticompton
spectrometer at NPI ASCR
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
Usage of inside geometry of source placement for cascade studies
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) :
6 -21 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
Efficiency εF, Peak/Compton, resolution ΔE/E
influence of Doppler shift – dominates at ΔE/E
Usage of semiconductor (HPGE) with BGO shielding
(efficiency up to εF = 10 %)
( tenths, hundreds of detectors)
Detector set-up EUROGAM II
USA –LBNL, ANL,
from 1995 - GAMMASPHERE - 70 -110 HPGe detectors
with BGO shielding, 4π geometry
Some photos of
Set-up
GAMMASPHERE
real and also
presentation
at film Hulk
WWW pages of
experiment
Europa – Daresbury, Heidelberg, Darmstadt, ...
from 1992 - EUROGAM I, II, EUROBALL III, IV - 2002
Some photos of
set-up EUROGAM
and EUROBALL
WWW pages of
experiments
Scintillation „walls“ for high energy physics
Detection of electromagnetic showers – identification of high energy photons
Heidelberg/Darmstadt – 162 NaI(Tl) ,
SLAC-DESY – 672 NaI(Tl) elmg calorimeters
CLEO II 8000 CsI(Tl) detectors – usage of silicon
photo diods -Cornell Electron-positron Storage Ring (CESR)
1991 - TAPS 384 BaF2 detectors
Crystal length 250 mm, diameter 59 mm
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 (BaF2 has two components of light emission)
Detection of photons from hundreds keV up
to tenth GeV produced directly or by decay of
particles (π0, η, ω, φ)
TAPS worked at GSI Darmstadt,
KVI Groningen, GANIL Caen, CERN,
MAMI Mainz, Bon
Block ofBaF2 crystals - spectrometer TAPS
Photon spectrometer TAPS at GSI Darmstadt and at KVI Groningen
Electromagnetic calorimeter of LHC experiment ALICE:
photon spectrometer PHOS
Crystals of PbWO4: 15X0 → 14 cm, R0 ~ 2 cm
sizes: l = 18 cm
S = 2,2×2,2 cm2
Whole area: ~ 8 m2
Optimized for Eγ ~ 0,5 GeV – 10 GeV
Crystals of PbWO4 are ready for PHOS
PET chambers for lékařskou diagnostiku
Positron emission tomography (PET) makes possible to obtain 3D pictures of patient tissues
Detectors record coincidences of annihilation quantum pairs 511 keV
Positron + electron – annihilation in the rest →
two annihilation quanta with energy 511 keV flight
in opposite directions
Two coordinates – position of photon detection
Third coordinate – determination from detection
time difference for photon pair
From hundreds up to thousands pair detectors
γ1 (511 keV)
Annihilation
γ2 (511 keV)
Example: Standard chamber of HR+Siemens at „Cyclotron BioMedical de Caen:
576 crystals, space resolution 4,5 a 3,6 mm