Transcript Development of photodetection system based on multipixel

DEVELOPMENT OF
PHOTODETECTION SYSTEM BASED
ON MULTIPIXEL AVALANCHE GEIGER
PHOTODIODES WITH WLS FOR LXE
LOW-BACKGROUND DETECTORS
D.Yu. Akimov, A.V. Akindinov,
I.S. Alexandrov, A.A. Burenkov, M.V. Danilov,
A.G. Kovalenko, V.N. Stekhanov
University Department, State Scientific Centre of Russian
Federation Institute for Theoretical and Experimental Physics
(ITEP), 25 Bolshaya Cheremushkinskaya str.,
Moscow, Russia
DARK MATTER EXPERIMENTS
Xenon10,100
at Gran Sasso
XMASS at Kamioka
All detectors utilizes
PMTs for detection of the
LXe VUV light.
ZEPLIN III at
Boulby mine
LUX at SUSEL
At present, PMTs (even
low-background) are the
most radioactive
elements of detector.
Search for a replacement of PMTs for
the future detectors is actual.
THE AIM OF THIS STUDY
The aim of the current work is to
demonstrate experimentally:
 The
possibility of the use of MPGP (Multi
Pixel Geiger Photodiode) for detection of
the LXe luminescence light together with a
wavelength shifter
 To estimate the global PDE of such a
system
MULTIPIXEL AVALANCHE GEIGER
PHOTODIODE
Readout
-Voper
Scheme of MRS APD
View of matrix cells
Structure of 1 cell
MULTIPIXEL AVALANCHE GEIGER
PHOTODIODE
Multiplication: M = C*(U - Ubr)
Charge: Q = e*Ncell*C*(U - Ubr)
Photon Detection Efficiency:
PDE= Q.E.*RG*ε geom
Typical PDE for CPTA 2x2 mm2
CPTA “green” – blue, green, IR
CPTA “blue” – blue, green, IR
WAVELENGTH SHIFTER
LXe emission, p-terphenyl absorption and
emission spectra and PDE of
“blue” CPTA photodiode
EXPERIMENTAL SETUP
LXe
LXe
1
1
2
2
3
3
4
7
4
5
6
5
8
a)
b)
Scheme of measurements. a) The p-terphenyl deposited layer between two optical windows,
b) p-terphenyl is coated by a poly-para-xylylene film. 1 – PMT Hamamatsu R7200, 2 – αsource 241Am,
optical
window
(sapphire), 4 – p-terphenyl, 5 – MRS APD, 6 – optical
2 x32- mm,
1584
pixels
window, 7 – Ar gas between the window, 8 - poly-para-xylylene film.
Photo of assembled constructions
(Ar gas between the windows)
EXPERIMENTAL SETUP
Photo multiplayer
MRS APD
k
Scheme of measurements
EXPERIMENTAL SPECTRUMS
noise
CPTA “blue”
PMT
α peak
pedestal
1 cell
2 cells
Pulse area, V·ns
RESULTS & PDE CALCULATION
84 cells
RESULTS & PDE CALCULATION
Sapphire
Ω2
Ω1 WLS
MRS APD
1
4
PDE      N cells 
2
  f  N 0  10
0
N cells
1  2
 N0  f 

   ,
4 4
N0=Eα/w, were Eα= 5.486 MeV
is the energy of alpha particle
w = 16.3 ± 0.3 eV
f - total attenuation coefficient
of the light in the windows
η - efficiency of transformation
of the VUV light to
the visible region
ξ - photo detection efficiency of
the photodetector in the
wave range of WLS emission
2
    PDE
4
1  2
10 1

 

4 4
4 2
RESULTS & PDE CALCULATION
Series of
measuremts
Ncells
µ
f
Figure 1a) 24±0.5 0.74 0.68
Ω
1.35*10-3
Figure 1b) 72±1.5 0.17 0.75 1.99*10-2
P. Benetti, et al., Nucl. Instr. Meth. A505,
89 (2003).
For a blue sensitive PMT (QE ≈20%) with
WLS.
PDE0 ,%
9.7
±1.2
8.4
±1.1
FUTURE PLANS
MGPD matrix
WLS
Electroluminescence, detected by MGPD
GEM/THGEM
Gaseous Xe
Electroluminescence, detected by PMTs
LXe surface
Grid
e-
LXe
Fig. 2. Possible design of high precision detection system for two-phase noble gas detectors with THGEM + WLS +MGPD.
CONCLUSION
•
•
•
The capability of operation of WLS in LXe with
protection has been shown.
Poly-para-xylylene film is good protection items
in LXe.
The results of experiment allow one to build a
detection system based on WLS.
Type of construction WLS
PDE, %
p-terphenyl is sealed between two
optical windows
p-terphenyl is coated by a poly-paraxylylene film.
9.7±1.2
8.4±1.1
One can build a system with low radioactive
background for a two-phase detector sensitive to
very low ionization.