Post on 31-Jan-2020
A Novel Position-Sensitive Radiation Detector Using a
Gaseous Photomultiplier and an UV Scintillator
Shunsuke KUROSAWAHidetoshi Kubo, Toru Tanimori,
Kojiro
Taniue
(Kyoto Univ.),
Hiroyuki Sekiya
(ICRR, The Univ.
of Tokyo), Kentaro Fukuda, Sumito
Ishizu, Noriaki
Kawaguchi,
Toshihisa
Suyama
(Tokuyama Corporation), Akira Yoshikawa, Takayuki Yanagida, Yuui
Yokota
(IMRAM,Tohoku
Univ.)
PD09 June 25, 2009 @ Shinshu Univ., Matsumoto, Japan
Contents
• Introduction – Other groups’ works
• gaseous photomultiplier(gaseous UV detector)
• VUV (vacuum ultra-violet) scintillator• Our new radiation detector• Summary
Advantage of Gaseous Photomultipliers (GPMs)
• Large Area : > ~ 1000 cm2
• Good position resolution : < ~ 1 mm• Easy to operation in a magnetic field• No vacuum• Low cost / area
Comparison with other photo detectors, especially Photomultiplier tube (PMT)
Such GPMs are better suited to Dark Matter / neutrino searches
GPMs with Bialkali photocathodeTokanai et al. in press
Bialkali(K–Cs–Sb)
Visible light
Pyrex glass capillary plat (Pitch: 300m)
160 m
Photo-electron
UV-sensitive GPMsLiq. Xe / Ar scintillators (λ<180nm)solid VUV scintillators
Bialkali: sensitive to visible light
GPMs with CsI photocathode
Semitransparent photocathode Reflective photocathode
• CsI + MPGDs (Micro Pattern Gas Detector) have been developed by other groups. – Cascade GEM / MHSP/ THGEM with rim and so on– ex) Chechik et al. NIM A 595(2008) 116 and its refs
GPMs with CsI photocathode• CsI + MPGDs (Micro Pattern Gas Detector)
have been developed by other groups. – Cascade GEM / MHSP/ THGEM with rim and so on– ex) Chechik et al. NIM A 595(2008) 116 and its refs
Semitransparent photocathodeShadow image with UV lampBellazzini et al. (2007)
Semitransparent Photocathode (CsI)+GEM +CMOS
CMOSEffective area:15 mm x 15 mmSmall size Compared to other GPMs
1mm
large area
28 cm
23cm
GEM (gas electron multiplier)
We have already operated the 30 cm size MPGD stably for a Compton camera and an X-ray imaging detector
30cm
30cm-PIC (micro pixel chamber)
2-D position sensitivegaseous detector
Concept of our new detector
1st step: Prototype of our GPM ( 10 cm size )with CsI photocathode
GPM using MPGD:larger areaLow cost / areacount rate~10MHz / mm2 with-PIC+GEM @ 17.4keV
UV Scintillator:Higher detection efficiencythan gaseous detector inhard X / gamma-ray rangeShort decay time ~ a few nsec
New hard X / gamma-ray imaging detector
Our gaseous photomultiplier (gaseous UV detector)
Overview of our GPMCsI photocathode•MgF2 window(5mm thickness)with Drift plane (Al)
GEM(gas electron multiplier)Sauli (1997), Inuzuka et al.(2004)Thickness :50 m, 100 mpre-gas-multiplier
Electric field
hv
e-
-PIC(micro pixel chamber)2-D detector
We used 2 GEMs + μ-PICGEMs for ion blocking-PIC for high position resolution,
stability in high gain,large effective area
10 cm
Sensitive to one photoelectron Total gas gain ~ 105-6
CsI Photocathode
Drift planeAl vapor deposition
PhotocathodeCsI vapor deposition50
70m
m
50m
m
34m
mMgF2 window Thickness : 5mm
CsI photocathode
for reference
Quantum Efficiency (QE)of R6835 (Hamamatsu)Using a MgF2 window
100 200 wave length [nm]
100
10
1
0.1
0.01
Qua
ntum
Effi
cien
cy QE
Graph by Hamamatsu
UV sensitive
-PIC : 2-D gaseous detector
10cm
Size: 10 cm x 10 cmPixel pitch: 400 m
~ 65,000 pixelsGas gain:
~6,000
(stable operation of more than 1 month)
400μm pitch
anode cathode
Cu
-PIC : gain and Energy spectrum
Gas gain uniformityRMS ~ 7%
Energy spectrum (55Fe)
E/E 30% @ 5.9 keV
Ar-escape
0 2 4 6 8 10Energy [keV]
We filled with Ar(90%) + C2 H6 (10%) gas at 1atm
X-ray imaging with -PIC
Test chart imagePosition resolution:120 m
AMP-Discri. BoardBased on a chip for ATLAS Thin Gap Chamber0.8V/pC
1 mm
GEM
Size : 10cm×10cm
Thickness (material) :100 m (LCP + Cu)50 m (Kapton + Cu)
plasma-etchedMade by SciEnergy
10 cm
We used 2 GEMsas pre-gas-multipliers above the -PIC
140 m
70 m
VUV scintillator
Our detector : X-ray imager
VUV scintillator
Electric field
e-
To detect hard X-rays with a higher efficiency, we used VUV (vacuum ultra-violet) scintillator on the GPM
X / gamma raysLaF3 (Nd)Maximum emission:
at 172 nm Light yield:
41080 ph / MeV @1.5mol% of Nd
Decay time: 6 nsecDensity : 5.9 g / cc
UV
Yang and DeLuca (1976)Dorenbos et al. (1990)Gruwe and Tavernier (1992) 10 cm
LaF3 (Nd) : an UV source
20 mm
160 180 200 220 240 260wave length [nm]
Made by Tokuyama corporation
Emission spectrum
172 nm
Cou
nts
(a. u
.)
Reflector : Gore-Tex
Measurement with PMT
Wave length [nm]
QE
[%]
160 170 180 190 200 210
PMT: R8778 (2-inch)(Hamamatsu)
PMT(R8778)
LaF3 (Nd)Reflector(Gore-Tex)
241Am (
source)
grease(Krytox 16350)
10
10033% @ 172 nm
Photoelectron0 20 40 60 80 100
Cou
nts
(a. u
.) ~30 p.e. (photoelectron)
~100 UV photons@ 5.5 MeV
ray
PMT QE
LaF3 (Nd) size: 15 mm x 15 mm x 15 mm
Our new radiation detector
= GPM (UV detector) + UV scintillator
Setup (1)
13 mm
2 mm
4 mm
Electric field
e-
UV
GEM : 422V-PIC: 465 VTotal gain: ~ 2.6x105
1st GEM
2nd GEM
-PIC
E = 0.3 kV / cm
E = 1 kV / cm
Ar(90%) + C2 H6 (10%) gas at 1 atm (sealed)
MgF2 window
241Am (
source)
10 cm
15 mmLaF3 (Nd): 15 mm x 15 mm x 15 mm
LaF3 + 241Am Top view
Anode signals
Oscilloscope
Pulse height : 120 mVpreAMP : 1V/pCGas gain : 2.6x105
2.9 p.e.
-PIC Anode
X 64 ch sum
CP581 preAMP(1V/pC) Clearpluse co., ltd.
Spectrum-PIC Anode
X 64 ch sum
~100 photons from LaF3 (Nd)
Our detector QE : 1-2 %
QE of CsI
QE ~2% @ 172nm
10MHz sampling ADC
CP581 preAMP(1V/pC) Clearpluse co., ltd.
Sensitive to 1 p.e.
Photoelectron0 2 4 6 8 10 12
Cou
nts
(a. u
.)
Setup (2)
2.5 mm
2.0 mm
2.0 mm
Electric field
e-
UV
GEM : 280V-PIC: 490 VTotal gain: ~ 7x105
1st GEM
2nd GEM
-PIC
E = 0.5 kV / cm
E = 2.95 kV / cm
Ar(90%) + C2 H6 (10%) gas at 1 atm (sealed)
MgF2 window
241Am (
source) LaF3 + 241Am
10 cm
20 mm
LaF3 (Nd): 20 mm x 20 mm x 20 mm
Top view
Gain: -PIC + GEMsGas: Ar(90%)
+ C2 H6 (10%) gasat 1 atm(sealed)
-PIC + double GEM
double GEM
~100Total gain:up to 7x105
106
105
104
103
102
10
1
gain
-PIC : 10 cm x 10 cm
GEMs :10 cm x 10 cm
Lens effect by Electric field
Electric field
UV
e- Lens Effect
It is possible that this effect may enhance the position resolution of the GPM by compensating for the electron diffusion in the gas.
20 mm
32mm
X 1.6
Rotation image
We can also obtain the image of LaF3 (Nd) at a 45-degree rotation
45°
Shadow images
Y projection
X projection10mm
15m
m
2mm
polyvinyl chlorideBlack tape(0.1 mm thickness)
LaF3 (Nd)
241Am
16mm
Galleries
When You Wish Upon a Star….
2 mm x 15 mm slits5 mm interval
14mm
Summary• We have developed a novel radiation detector
– Gaseous UV detector :Semitransparent CsI photocathode (3.4 cm ) 2 GEMs, -PIC (10 cm x 10 cm)
– VUV scintillator : LaF3 (Nd) • We obtained images
– Lens effect, magnification : 1.6
Future work• Measurement of collection efficiency /
ion feedback• Test of a reflective CsI photocathode• Test of large-area window• Development of large-area LaF3 (Nd) / new crystal
Thank you for your attention