I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I - - PDF document

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

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' Ambr osio1, F. de Not ar ist ef ani2, H. Leut z1, D. Puer t olas2, E. Rosso1

1 CERN, 2 I NFN Sect ion of Rome, I t aly

• D. P.

CERN INFN-Roma III (HIRESPET* Collaboration) Institute of Physics, Academy of Sciences-Prague Alice and LHCb exp. at CERN EP-TA2 and EP-MIC groups at CERN Industrial partners: D.E.P. (NL) Crytur Ltd. (CZ) Edgetek (FR) *http://www.roma1.infn.it/~hirespet/index.html

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

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OUTLI NE

Short int roduct ion t o t he I SPA-t ube “Convent ional” designs of gamma cameras based on I SPA-t ubes and result s Pr esent development s : scint illat ing windows (YAP:Ce) Conclusions and f ut ur e out look

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

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Position- sensitive photon detection with an I SPA- tube

Signal out (pixel binary readout) Signal out (global analog readout)

Pixel electronics 500µm x 50µm Pixel detector 500µm x 50µm

VACUUM

Phot oelect ron Photon Photocathode Optical input window Solder bump

• + - +
• + - +
• + - +
• + - +

+ - + - + - + - + - + - + - + -

Electron- hole pairs (typ. 5- 6500)

• H. V. (typ. 20-25 kV)

Bias voltage (typ. 50-70 V) Pixel chip developed by CERN/EP-MIC

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

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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

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

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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-throughs Bump bonds Co source

57

122 keV γ's Lead phantom YAP-detector Rear contact Electronics pixel array (1024 elements)

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

Detection of γ

γ γ γ- rays with an I SPA- tube

Ω chip assembly developed by RD19 collabor at ion Pixel size 75mmx500mm

• D. P.

γ γ γ γ- imaging with an I SPA- tube coupled to YAP:Ce crystal detectors *

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

P r opert ies of pur e YAP Chemical formula YAlO3 (inert, non hygroscopic) Crystal structure Orthorhombic (no cleavage) Density g.cm-3 5.37 Molecular weight 168.88 Zeff 34 Hardness Moh 8.6 Refractive index n at 400 nm 1.97 at 500 nm 1.95 Transparency nm 240 to >1000 Addit ional propert ies of YAP doped wit h Ce Light emission peak nm 365 Light decay (1/e) ns 27 Radiation length cm 2.7

• Avr. K X-ray energy of Yttrium

keV 15.2 Refractive 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 t o it s pr opert ies YAP can be easily machined and opt ically polished. Ar rays of small individual element s (1mm2 down t o 300µm2 can be assembled)

• D. P.

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

Perf ormances of I SPA- tubes in imaging

The overall per f or mances of t he I SPA-t ube r ely on bot h The input window ar rangement : t he goal is t o collect as many phot oelect rons as possible while pr eser ving t he “localisat ion” of t he gamma event The anode pixel chip: t he goal is t o det ect as many phot oelect rons Npe as possible on t he det ect or plane (energy r esolut ion considerat ions) and t o get a binar y pat t ern r epr oducing t he light spot on t he phot ocat hode wit h a number of f ir ing pixels Nhit (< Npe) allowing a precise c.o.g calculat ion (analysis event per event )

• D. P.

X- or γ γ γ γ- ray

Phot ons

YAP:Ce array

Quartz window

Phot oelect ron clust er

X- or γ γ γ γ- ray YAP:Ce plate

Phot oelect ron cluster

Fibre opt ic window

X- or γ γ γ γ- ray X- or γ γ γ γ- ray YAP:Ce array YAP:Ce plate

Phot oelect ron cluster Phot oelect ron clust er Phot ons Phot ons Photons

Dif f erent possible conf igurations

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

(FWHM)~2-2.5 mm (FWHM)>3.5 mm (FWHM)~crystal elements (FWHM)~2mm

• D. P.

Result summary

Fibr e window I SPA-t ube: ++ excellent spatial resolution from 100 µm (array) to 300 µm (plate)

• - poor E-resolution (only a few photoelectrons)

Quar t z window I SPA-t ube: ÷ acceptable spatial resolution from 500 µm (array) to 700 µm (plate) + good E-resolution at 122 keV from 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 I SPA-t ube wit h lar ger act ive surf ace (40 mm diamet er) + The demagnification (~4) principle has been also successfully applied for gamma imaging applications, with sub-millimeter spatial resolution see NIM, A442, (2000), p.279

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

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I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

Current I SPA prototype

Phot oelectron clust er Phot ons

YAP:Ce window X- or γ γ γ γ- ray

Phot oelect ron cluster Phot ons

YAP:Ce plat e X- or γ γ γ γ- ray quartz window

LHC1* chip implementation

new electronics ☛✝ amplifier 100 ns peaking time, globally adjustable threshold, adjustable delay line, coincidence logic and memory smaller pixel size ☛✝(50x500µm) Electrical tests ☛✝~7.5% (150) pixels are masked (noisy) ✝✝✝✝✝✝✝✝✝✝✝✝✝✝☛ test input ~4900e- γ=1710 (~85%) pixels respond with an efficiency of ~95%

≠* The LHC1 chip has been developed at CERN by the RD19 and the EP/MIC group YAP:Ce scintillating window

• D. P.

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

Quantum ef f iciency of S20 photocathode

• n YAP:Ce scintillating window

P erf ect st abilit y observed over 2 years

5 10 15 20 25 30 200 250 300 350 400 450 500 550 600 650 700 750 800 Q.E YAP-window HPMT Q.E Quartz-window HPMT Q.E. YAP-window ISPA Q.E. Quartz-window ISPA Quantum Efficiency [%] Wavelength [nm]

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I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

1000 2000 3000 4000 5000 50 100 150 200 250 300 350

Number of photoelectrons counts [a.u.]

122 keV (FWHM) ~ 22% Compt on edge (39 keV) P b ~ 80 keV + b. sc.

1000 2000 3000 4000 5000 50 100 150 200 250

Number of photoelectrons counts [a.u.]

60 keV (FWHM) ~ 26.5% Compt on edge (11keV)

Energy spectra of some dif f erent sources

Emissions conver t ed in t he YAP:Ce window of t he I SPA-t ube Pulse height dist r ibut ions measur ed on t he silicon chip r ear side

57Co 241Am

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I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

1000 2000 3000 4000 5000 20 40 60 80 100 120 140 160 180 200

Number of photoelectrons counts [a.u.]

22 keV (FWHM) ~ 40% Y escape (6.3 keV)

(x20)

88 keV

1000 2000 3000 4000 5000 6000 5 10 15 20

Number of photoelectrons counts [a.u.]

5.9 keV

Energy spectra of some dif f erent sources

Emissions conver t ed in t he YAP:Ce window of t he I SPA-t ube Pulse height dist r ibut ions measur ed on t he silicon chip r ear side

109Cd 55Fe

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I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

Energy spectra of some dif f erent sources

Emissions conver t ed in t he YAP:Ce window of t he I SPA-t ube Pulse height dist r ibut ions measur ed on t he silicon chip r ear side

1000 2000 3000 4000 100 200 300 400 500 600 700

Number of photoelectrons counts [a.u.]

279.2 keV t wo K lines (72.19 keV)

203Hg

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I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

y = 1.7468x - 0.203 R2 = 0.9994 50 100 150 200 250 300 350 400 450 500 550 50 100 150 200 250 300

Energy [keV] Number of photoelectrons

203 Hg γ 241 Am γ 203 Hg K 109 Cd γ 203 Hg L 57 Co γ 109 Cd Ag X 55 Fe Mn X

Photoelectron numbers versus the energies of total absorption peaks f or several gamma sources measured with the YAP- window I SPA- tube

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I mage of a 60 keV γ

γ γ γ- source (241Am) through a

2- holes (0. 35 mm φ

φ φ φ) lead collimator (5 mm thick)

~1 mm

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

20 k-events

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5 10 15 20 25 30 35 40 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00

c.o.g. coordinate projection x(mm)

mean1 = 2.80 mm sigma1 = 0.195 mm mean2 = 3.70 mm sigma2 = 0.190 mm

I ntensity prof ile of the two holes along the X- direction

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

distance of the two holes = 0.90 mm on chip

• FWHMxmeas. = 0.452 mm

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I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

Average number of f iring pixel per gamma event: Nhit

100 200 300 400 500 600 10 20 30 40 50 60 70 80 90 100 110 120

Number of hits per event

mean at ~50 hits

Not e: Nhit ~50 is < t o Npe~100. The great est part of t he dif f erence is due t o “overlap” ef f ect

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I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging. 5000 10000 15000 20000 25000 30000

• 4
• 3
• 2
• 1

1 2 3 4

c.o.g. residuals x(mm)

Center- of - gravity residual projection along the X- direction

=(FWHM)resX = 1.50 mm on chip

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2 2 2

) (FWHM N FWHM

hit res

=

• +

φ

(FWHM)resX = 1.50 mm; (FWHM)resY = 1.46 mm; Nhit ~50 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.

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

The estimation of the spatial resolution is simply given by:

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CONCLUSI ONS

First result s wit h t he YAP:Ce window I SPA- t ube are very encouraging (clust er size / 2, Npe x1.2). They can be used t o det ect a wide range of energies (window t hickness can be adj ust ed). Bet t er mat ching of ref ract ive index if coupled t o ot her st andard cryst als. The perf or mances can be f urt her improved wit h t hose of f ut ure pixel chip anode.

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

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I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

FUTURE OUTLOOK

Development s on heavier Ce-doped scint illat ors and of larger dimensions. I mplement at ion of ALI CE chip. Possible use of t hinned det ect or unit .

• D. P.

I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

Attenuation coef f icients of Cerium- doped RE3+ perovskyte scintillators

0.1 1 10 100 0.01 0.1 1 Energy (MeV) Linear attenuation coefficient (cm-1)

YAP LuAP Lu

• 0. 1Y0. 9AP

Lu

• 0. 3Y0. 7AP

140 keV (99mTc)

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I SPA-Tubes wit h YAP:Ce Act ive Windows f or X and Gamma Ray I maging.

• 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 wit h a 3-mm t hick scint illat ing window: YAP;Ce ~30% ef f iciency (~55% t ot al absor pt ion) Lu0.1Y0.9AP :Ce ~45% ef f iciency (~70% t ot al absor pt ion) Lu0.3Y0.7AP:Ce ~65% ef f iciency (~80% t ot al absor pt ion) LuAP:Ce ~95% ef f iciency (~95% t ot al absor pt ion)