Testing of the optical module inside the volume of Cherenkov water detector NEVOD
S.S. Khokhlov*, T.A. Karetnikova, V.V. Kindin, N.A. Pasyuk, A.A. Petrukhin
National Research Nuclear University MEPhI
Very Large Volume Neutrino Telescope Workshop Valencia, May 18-21, 2021 1
Introduction Neutrino telescopes are actively developing instruments for astroparticle physics.
The basic element of the Cherenkov water neutrino telescope is an optical module (OM).
One of the most important experimental problems is the calibration of different optical modules under the same conditions.
2 Variants of optical modules
Amanda (IceCube) - 1 NT 200 Baikal (2) ANTARES (3)
NEVOD (6) IceCube-Upgrade (24) KM3NeT (31) 3 The first quasispherical module (QSM) with 6 PMTs
The idea of the construction of quasispherical modules from several PMTs was presented at Cosmic Ray Conference in Kyoto in 1979 (Borog V.V. et al., Proc. 16th ICRC, 1979 10, 380)
Module with six PMTs oriented along the axes of the orthogonal coordinate system is the simplest configuration of photomultipliers, the response of which does not depend on Cherenkov light direction.
4 Cherenkov Water Detector NEVOD-91 (1994)
• Sizes 9 x 9 x 26 ~ 2100 m3 • Spatial lattice from 91 QSM with steps 2 2 2.5 m3. • Russian PMTs – FEU-49, FEU-125 (now, FEU-200) • Placement of CWD NEVOD on the ground level allows investigate all components of cosmic rays reaching the Earth’s surface, including neutrinos from the bottom hemisphere.
Registering System allows measure signals in the dynamic range from 1 to 105 ph.e. for each photomultiplier. Trggering System allows separate events produced by particles coming from the top, the bottom, and any side. 5 Cherenkov Water Detector NEVOD-91 (1994)
6 New optical module QSM-6M It is planned to create two additional vertical planes with 16 modules in each. Thus, the volume of the spatial lattice of the Cherenkov water calorimeter will be increased from 800 to 1200 m3.
FEU-200 Hamamatsu R877 New modules will be based on the PMT
Hamamatsu R877.
FEU-200 R877 Cathode flat flat Cath. Material bialkali bialkali Tube size 170 mm 133 mm Cath. Area Size 150 mm 120 mm Dyn. Structure blinds Box-grid Dynode Stages 12 10 Supply Voltage 1500 1250
7 Possibilities of CWD NEVOD for OMs calibration
In 2019-2020, the new module QSM-6M based on the PMT Hamamastsu R877 has been developed.
NEVOD facility can be used for calibration of new optical modules for the largest neutrino telescopes: IceCube, KM3NeT and Baikal-GVD.
On July 10, 2020, the patent on invention has been registered (RU 2726265 “Complex for measuring the angular dependence of the response of the optical module of the neutrino Cherenkov water telescope”).
The technique of calibration of neutrino telescope OM is being tested with the module QSM-6M.
Since April 8, 2021, the optical module QSM-6M is operating at a depth of 3.5 m. 8 General scheme of the NEVOD complex
Calibration Telescope System (CTS) Cherenkov water detector NEVOD SM07 SM06
SM00
SM01 SM05 SM04 SM03 Coordinate detector DECOR SM02
Water tank sizes 9 9 26 m3
9 System of calibration telescopes (SCT) Top view SCT detector 1.25
m
1.0 m 1.0
SCT NEVOD
QSM 2.5 m
2 layers x 40 scintillation detectors. 3 Sizes of scintillator 20 40 2 cm .
Accuracy of track reconstruction is better than 2°. 10 Response of PMTs on near-vertical muons selected by means of calibration telescopes
PMT in OM D, m Nev Eff, %
8 supermodules x 8 layers of plastic streamer tube chambers. 12 Response of PMTs on near-horizontal muons selected by means of DECOR
At distances of more than 4 meters, the response curve begins to show features associated with the reflection of Cherenkov light from the water surface. 13 Angles of arriving of Cherenkov light to QSM-6M (1 m < D < 2 m)
From April 8 to May 13, 50,000 events have been registered. After 1-2 months, the necessary statistics will be reached and the optical module can be rotated or moved to measure the response at other angles. 14 Events with big energy deposit
Experimental complex NEVOD has a special trigger “60c” (rate ~4 s-1) for detecting of events with a big energy deposit.
Such events include:
EAS;
muon bundles;
cascades generated by muons and hadrons.
15 Response of OM on events with big energy deposits
The estimated spectrum slope γ = 2.4 is smaller than the expected index for EAS γ = 2.55. This is a reasonable result, since other events 16 with a large energy losses are mixed with EAS events. Variants of mDOM calibration in NEVOD
In Muenster University, a new optical module mDOM has been developed. mDOM can be used in next generation of IceCube (IceCube-Upgrade).
17 Calibration of mDOM is planned for 2021-2022. Conclusion The new module QSM-6M based on the PMT Hamamatsu R877 has been developed.
Experimental complex NEVOD can be used as a test facility for calibration of optical modules of future neutrino telescopes.
The technique of OM calibration is being tested with the module QSM-6M.
Calibration of mDOM (optical module for IceCube- Upgrade) is planned for 2021-2022. 18
Thank you for your attention!
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