D. P. ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging. PIXEL 2000 International Workshop on Semiconductor Pixel Detectors for Particles and X-Rays Genova - Porto Antico - Magazzini del Cotone (Sala Libeccio) June 5-8, 2000 C. D'Ambrosio 1 , F. de Notaristefani 2 , H. Leutz 1 , D. Puertolas 2 , E. Rosso 1 1 CERN, 2 INFN Section of Rome, Italy
25
Embed
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
PIXEL 2000 International Workshop on Semiconductor Pixel Detectors for Particles and X-Rays Genova - Porto Antico - Magazzini del Cotone (Sala Libeccio) June 5-8, 2000. ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging. - PowerPoint PPT Presentation
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
D. P.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray
Imaging.
PIXEL 2000
International Workshop on Semiconductor
Pixel Detectors for Particles and X-Rays Genova - Porto Antico - Magazzini del Cotone (Sala Libeccio)
June 5-8, 2000
C. D'Ambrosio1, F. de Notaristefani2, H. Leutz1, D. Puertolas2, E. Rosso1
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
D. P.
OUTLINE
Short introduction to the ISPA-tube
“Conventional” designs of gamma cameras based on ISPA-tubes and results
Present developments : scintillating windows (YAP:Ce)
Conclusions and future outlook
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
D. P.
Position-sensitive photon detection with an ISPA-tube
Signal out(pixel binaryreadout)
Signal out(global analog
readout)
Pixel electronics500m x 50m
Pixel detector500m x 50m
VACUUM
Photoelectron
Photon
Photocathode
Optical inputwindow
Solder bump
- + - ++ - + -
Electron- hole pairs(typ. 5- 6500)
H. V
. (ty
p. 2
0-25
kV
)B
ias
volt
age
(typ
. 50-
70 V
)
Pixel chip developedby CERN/EP-MIC
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
D. P.
The self-triggering principle
detector chip
electronics chip
Fast, analog and global information
Trigger for strobe
Immediate calibration in photoelectron or energy
Selection of a window in
energy possible
Pixel signals out (with present chip, pixel response is binary
Precise space information
2-D imaging
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
D. P.
Photocathode (-25 kV)
Input window
Photoelectrons
Photons
Silicon pixel array (1024 elements)
Fast (10 ns) global analog information
Binary pixel pattern read out in 10 µs
VACUUM
30 lead-throughsBump bonds
Co source57
122 keV 's
Lead phantom
YAP-detectorRear contact
Electronics pixel array (1024 elements)
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
Detection of -rays with an ISPA-tube
chip assembly developed by RD19 collaborationPixel size 75mmx500mm
D. P.
-imaging with an ISPA-tube coupled to YAP:Ce crystal detectors *
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
Properties of pure YAPChemical formula YAlO3 (inert, non hygroscopic)Crystal structure Orthorhombic (no cleavage)Density g.cm-3 5.37Molecular weight 168.88Zeff 34Hardness Moh 8.6Refractive index n at 400 nm 1.97
at 500 nm 1.95Transparency nm 240 to >1000
Additional properties of YAP doped with CeLight emission peak nm 365Light decay (1/e) ns 27Radiation length cm 2.7Avr. K X-ray energy of Yttrium keV 15.2Refractive index n at 400 nm 1.92
at 500 nm 1.91
* Our YAP crystal detectors are produced by Crytur Ltd, Turnov, Czech Republic
Due to its properties YAP can be easily machined and optically polished.Arrays of small individual elements (1mm2 down to 300m2 can be assembled)
D. P.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
Performances of ISPA-tubes in imaging
The overall performances of the ISPA-tube rely on both
The input window arrangement: the goal is to collect as many photoelectrons as possible while preserving the “localisation” of the gamma event
The anode pixel chip: the goal is to detect as many photoelectrons Npe as possible on the detector plane (energy resolution considerations) and to get a binary pattern reproducing the light spot on the photocathode with a number of firing pixels Nhit (<Npe) allowing a precise c.o.g calculation (analysis event per event)
D. P.
X- or - ray
Photons
YAP:Ce array
Quartz window
Photoelectroncluster
X- or - ray
YAP:Ce plate
Photoelectroncluster
Fibre opticwindow
X- or - ray
X- or - ray
YAP:Ce array
YAP:Ce plate
Photoelectroncluster
Photoelectroncluster
Photons
Photons
Photons
Different possible configurations
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
(FWHM)~2-2.5 mm (FWHM)>3.5 mm
(FWHM)~crystal elements (FWHM)~2mm
D. P.
Result summary
Fibre window ISPA-tube:
++ excellent spatial resolutionfrom 100 m (array) to 300 m (plate)
+ good E-resolution at 122 keVfrom 20% FWHM (plate) to 40% FWHM (array) 200 p.e. 80p.e.
see IEEE TNS, vol. 42, no6, p. 2221 and vol. 44, no5, p.1747
ISPA-tube with larger active surface (40 mm diameter)+ The demagnification (~4) principle has been also successfully applied for gamma imaging applications, with sub-millimeter spatial resolution see NIM, A442, (2000), p.279
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
D. P.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
0
1000
2000
3000
4000
5000
0 50 100 150 200 250 300 350
Number of photoelectrons
coun
ts [
a.u.
]
122 keV
(FWHM) ~ 22%
Compton edge
(39 keV)
Pb ~ 80 keV
+ b. sc.
0
1000
2000
3000
4000
5000
0 50 100 150 200 250
Number of photoelectrons
coun
ts [
a.u.
]
60 keV
(FWHM) ~ 26.5%
Compton edge
(11keV)
Energy spectra of some different sourcesEmissions converted in the YAP:Ce window of the ISPA-tube Pulse height distributions measured on the silicon chip rear
side
57Co
241Am
D. P.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
0
1000
2000
3000
4000
5000
0 20 40 60 80 100 120 140 160 180 200
Number of photoelectrons
coun
ts [
a.u.
]
22 keV
(FWHM) ~ 40%
Y escape
(6.3 keV)
(x20)
88 keV
0
1000
2000
3000
4000
5000
6000
0 5 10 15 20
Number of photoelectrons
coun
ts [
a.u.
]
5.9 keV
Energy spectra of some different sourcesEmissions converted in the YAP:Ce window of the ISPA-tube Pulse height distributions measured on the silicon chip rear
side
109Cd
55Fe
D. P.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
Energy spectra of some different sourcesEmissions converted in the YAP:Ce window of the ISPA-tube Pulse height distributions measured on the silicon chip rear
side
0
1000
2000
3000
4000
0 100 200 300 400 500 600 700
Number of photoelectrons
coun
ts [
a.u.
]
279.2 keV
two K lines
(72.19 keV) 203Hg
D. P.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
y = 1.7468x - 0.203
R2 = 0.9994
0
50
100
150
200
250
300
350
400
450
500
550
0 50 100 150 200 250 300
Energy [keV]
Num
ber
of p
hoto
elec
tron
s
203 Hg
241 Am 203 Hg K
109 Cd
203 Hg L
57 Co
109 Cd Ag X 55 Fe Mn X
Photoelectron numbers versus the energies of total absorption peaks for several gamma
sources measured with the YAP-window ISPA-tube
D. P.
Image of a 60 keV -source (241Am) through a 2-holes (0.35 mm ) lead collimator (5 mm
thick)
~1 mm
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
x 0.352 + 0.2142 = 0.4102 <===> FWHMxmeas. = 0.452 mm
y 0.352 + 0.2062 = 0.4062 <===> FWHMymeas. = 0.435 mm
The difference between the estimated values and the measured ones can be related to the tails in the residual distributions, which worsens the precision in the c.o.g. calculation.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
The estimation of the spatial resolution is simply given by:
D. P.
CONCLUSIONS
First results with the YAP:Ce window ISPA-tube are very encouraging (cluster size /2, Npe x1.2).
They can be used to detect a wide range of energies (window thickness can be adjusted).
Better matching of refractive index if coupled to other standard crystals.
The performances can be further improved with those of future pixel chip anode.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
D. P.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
FUTURE OUTLOOK
Developments on heavier Ce-doped scintillators and of larger dimensions.
Implementation of ALICE chip.
Possible use of thinned detector unit.
D. P.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
Attenuation coefficients of Cerium-doped RE3+ perovskyte scintillators
0.1
1
10
100
0.01 0.1 1Energy (MeV)
Lin
ear
atte
nuat
ion
coef
fici
ent
(cm
-1)
YAP
LuAP
Lu0.1Y0.9AP
Lu0.3Y0.7AP
140 keV(99mTc)
D. P.
ISPA-Tubes with YAP:Ce Active Windows for X and Gamma Ray Imaging.
Rel. L. Y. Density Peak emission Light decay%NaI(Tl) (g.cm-3) (nm) (ns)
NaI(Tl) 100 3.67 415 230
BGO 20 7.13 480 300
YAP:Ce 40 5.37 365 27
Lu0.1Y0.9AP:Ce - 5.73 - -
Lu0.3Y0.7AP:Ce - 6.19 - -
LuAP:Ce 20-50 8.34 360-370 <20
Some properties of Cerium-doped RE3+ perovskyte scintillators
@ 140 keV with a 3-mm thick scintillating window:
YAP;Ce ~30% efficiency (~55% total absorption)Lu0.1Y0.9AP:Ce ~45% efficiency (~70% total absorption)Lu0.3Y0.7AP:Ce ~65% efficiency (~80% total absorption)LuAP:Ce ~95% efficiency (~95% total absorption)