1)National Research Nuclear University “MEPhI”, Moscow
2) SSC RF Institute for Theoretical and Experimental Physics
of National Research Center “Kurchatov Institute”, Moscow
3)Enikolopov Institute of Synthetic Polymeric Materials of the Russian
Academy of Sciences
Victor Stekhanov - PhotoDet 2015 – Moscow - Troitsk
The first studies of VUV detection by the SiPM have shown that
it is necessary to use a WLS. Some manufacturers produce
native VUV sensitive SiPMs at present. Collaborations Gerda,
MEG, NEXT, nEXO plan to use these SiPMs in their detectors.
The PDE of these SiPMs is lower than green or blue sensitive
SiPMs. In our previous studies, it was obtained in the WLS +
SiPM system is about 50% of the sensitivity of the SiPM.
We started to develop a WLS + SiPM system for using it in the
nEXO prototype. In this study, we used the SiPMs developed at
the MEPhI (MEPhI-KETEK) and SensL and nanostructured
organosilicon luminophores (NOL) as the WLS from the ISPM
RAS.
Wavelength shifter from 175nm to 420nm activity
• Development SiPM + WLS system for UV light detection. • The nanostructured organosilicon luminophore (NOL) wave length shifter for shifting light of
175 nm (Xe luminescence light) to 420 nm wavelength has been developed and created at Enikolopov Institute of Synthetic Polymeric Materials.
• Details can find in the poster: BORSHCHEV, Oleg (Enikolopov Institute of Synthetic Polymeric
Materials of Russian Academy of Sciences), Nanostructured organosilicon luminophores as effective spectral shifters in a wide spectral region.
• The SiPM optimized for 420 nm (PDE ~ 30%) developed and created by MEPhI research group
was used with this WLS.
• The assembly for SiPM testing with different thickness of NOL deposited on the SiPM surface was designed and made at ITEP.
Light absorption (in arbitrary units of optical density) and luminescence for NOL WLS.
PDE spectrum of SiPM without NOL WLS
PDE calculated spectrum for SiPM + NOL WLS
NOL WLS absorption
NOL WLS emission
For example, for PDE420 = 0.3 => PDESiPM+WLS ~ 0.12 for 170 nm – 300 nm region.
D.Yu. Akimov et al., NIM A 695 (2012) 403
4π
2πPDEPDE 420WLSSiPM
φ - fluorescence quantum yield (~80%)
PDE 420 – SiPM PDE at maximum
~0.4 PDE420
Schematic drawing of nanostructured Si-organic luminophore.
1–absorption fragment, 2–luminophore,3–Si atom
Amplifier for SiPM
255nm UV LED
SiPM This assembly was used for SiPM testing
with NOL WLS with different thickness.
255 nm UV LED
SiPM
Amplifier
Output signal
0 50 100 150 200 250 300 350
300
400
500
600
700
800
900
1000
1100
1200
1300Dependence of the SiPM signal
on the shifter thickness
Source light
UV Led 255nm, 150 ns, 1 kHz
sig
nal (d
ata
ph
.e. in
im
pu
lse)
coating thickness, nm
The signal amplitude dependence versus thickness of WLS, deposited on the
SiPM surface and irradiated with 255 nm light.
The 300 nm thickness is the optimal value.
WLS
Light source
Sig
na
l a
mp
litu
de
(p
h.e
. p
er
pu
lse
)
SensL MicroFC-30035-SMT SiPM testing
As a possible candidate of SiPM to use with NOL we consider the SensL SiPM 3x3mm with 35µm cell size. The SensL SiPMs have two outputs: normal and fast. This SiPM was tested at 27V voltage and (2.5V overvoltage) with 420nm blue LED at room temperature.
Measured total noise count rate - 3kH.
Pulse height spectrum with up to 9 separated photoelectron peaks was measured.
35µm cell 3x3 mm SensL FC-30035-SMT SiPM signal shapes
Pulse height spectrum
1pe
2pe
3pe 4pe
5pe
6pe
7pe
8pe
9pe
Development of UV sensitive SiPM.
MEPhI group continue to work on UV sensitive SiPM technology. Already made uncoated sample of SiPM with 1x1mm size and 100µm cell shows PDE=26±3% at U=38.0V (Ubreakdown = 33.52V), at room temperature and at λ=240nm.
The SiPM has good single photoelectron spectrum.
This photodetector is the first step towards development of the SiPM sensitive to 175 nm Xe luminescence.
Status with R&D study with SiPMs in liquid Xenon
• It is expected that NOL WLS will not dilute in LXe because of the large atomic weight, and thus, not decrease electron lifetime in liquid xenon.
• We are close to start cryogenic tests of system for SiPM + NOL WLS in liquid Xe. Initial version of the electrode system with SensL MicroFC-60035-SMT SiPMs is designed and it’s now under assembling.
Electrode structure for perspective testing 96 SiPMs in liquid Xe
Thermosyphone based cryogenic system
Liquid nitrogen
thermosyphone volume
Vacuum thermo-insulation
Electrode system
Conclusion
• The use of WLS is a simple way enhance UV-sensitivity of commercially
available SiPMs. WLS applied on the surface of the SiPM directly.
• Nanostructured organosilicon luminophores is a big step forward in
development of WLS.
• WLS emission peak can be tuned to the wavelength of SiPM max
sensitivity. In UV region PDESiPM+WLS ~ 0.4 PDEmax . In our case ~12 %
for ≤ 350 nm (PDE max = 30%).
• PDE=26±3% at 240 nm is obtained for MEPhI SiPM.
• We are about to start cryogenic tests with SiPM + NOL WLS in liquid
