PoS(ICRC2021)1097 International th 12–23 July 2021 July 12–23 37 SICS CONFERENCE SICS CONFERENCE Berlin | Germany Berlin 1 Berlin | Germany Cosmic Ray Conference Ray Cosmic ICRC 2021 THE ASTROPARTICLE PHY ICRC 2021 THEASTROPARTICLE PHY https://pos.sissa.it/ 1 1 ONLINE A. A. Shikhin, B. K. Lubsandorzhiev, 1 1 and D. M. Voronin 1 T. V. Ibragimova, A. Yu. Sidorenkov, 1 3 , 1 E. P. Veretenkin 1 D work aimed to develop light concentrators for the Baksan & V. N. Gavrin, ∗ , 2 , 1 N. A. Ushakov, Yu. M. Malyshkin, 3 1 [email protected] International Cosmic Ray Conference (ICRC 2021) Presenter ∗ th At the Baksan Neutrino Observatoryto deployed develop, in at the a North depth Caucasus correspondingon mountains, to a about it 4700 liquid is mwe, proposed scintillator a with large-volumelow-energy neutrino a neutrino detector target based physics, mass astrophysics of and 10crucial geophysics. kt. for such detectors. The The To main highest improvedetectors, light physics possible light yield goals concentrators and light are of energy often yield the resolution mounted is in on detectorefficiency photomultiplier large-volume are tubes neutrino of to optical increase the photons detection from scintillationWe present or the Cherenkov results light of induced recent bylarge-volume charged liquid R particles. scintillator neutrino detector. Institute for Nuclear Research of Russian AcademyMoscow of Institute Sciences, of Physics Moscow and 117312, Technology Russia (National Research University),Joint Dolgoprudny Institute 117303, for Russia Nuclear Research, Joliot CurieE-mail: 6, Dubna, Moscow Region 141980, Russia Copyright owned by the author(s) under the terms of the Creative Commons 1 2 3 © Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). A. D. Lukanov , O. Yu. Smirnov, A. N. Fazliakhmetov, Light concentrators for large-volume detector atBaksan the Neutrino Observatory 37 July 12th – 23rd, 2021 Online – Berlin, Germany PoS(ICRC2021)1097 D work aimed to & A. N. Fazliakhmetov 2 5t detector prototype design Figure 1: A new large-volume Baksan neutrino telescope (10 kt liquid scintillator) will be developed at Section 2 presents the detector prototypes design. The method for optimization of the concen- The neutrino telescope project is divided into four stages with increasing detection mass of D work. & the Baksan Neutrino Observatory of the Institute for Nuclearat Research Russian a Academy of depth Sciences of about 4700detector mwe are (meter low-energy water neutrino equivalent) physics, [1],[2], geophysicsyield [3]. and is astrophysics. The crucial main The for physics highest detector goals(PMTs) possible is of development. light the one of Mounting the lighton ways concentrators to an to entrance increase aperture photomultiplier light over tubes collection a givenaperture efficiency. angular of range Such the and device reflects PMT takes by photocathode. light aby curved incident minimizing Additionally, surface concentrators the to can required a number smaller reduce exit of totalsuccessfully PMTs. used experiment by costs Light several concentrators neutrino based experiments, onimaging for Winston example, atmospheric the cone Cherenkov SNO [4] telescopes. [5] was We and present Borexino the [ 6] and results of recent R trator shape will be describedR in Section 3. In Section 4, we present the2. results of concentrators 5t prototype design liquid scintillator target: fromfull-scale 0.5t detector prototype (10kt) on to the 5t last phase.Currently, (second The prototype), the first 100t and first second (third prototypes stage stage)construction. have a of and two-zone design. the the project is being completed, the second prototype (5t) is under Light concentrators for large-volume detector at the Baksan Neutrino Observatory 1. Introduction develop light concentrators for the Baksan large-volume liquid scintillator neutrino detector. PoS(ICRC2021)1097 will be > 5 5 − (the left border 2DC 1 % A. N. Fazliakhmetov \ < \ connecting the points C>C0; ! and PMT photocathode with curvature . Holding the length fixed, we trace out $ 1 % to the top. Rotating the profile about the axis of 3 1 % The String method principle illustration. Figure 2: , let’s stretch the "string". One end of the "string" is tied on point K, another end on which is the right boundary of the photocathode surface. We choose the length of the 1 2 $ % Between scintillation sphere with the centre at point Implementation of the string method was done by using python3 programming language with 1 Figure shows 5t detector prototype design. The central zone is an acrylic sphere filled with The concentrator shape was developed using the String method (also known as Winston cone centre point "string" so that, when taut, it wraps around the photocathode and reaches point NumPy library. Firstly, we calculate the total length of the string of the photocathode). Put the tip of a pencil at point reflected onto the photocathode. For 3Dthe case, case the of light skew incident collection rays efficiency the will arch reduce of because the in photocathode will be lower than at the 2D profile. the concentrator profile as thesymmetry tip moves gives from the concentrator shape. In 2D case, any incident rays with an ultrapure liquid scintillatorzone. (linear The alkylbenzene second (LAB) zone + isas filled PPO) muon with and veto. water to surrounded The protect by scintillator(220 against a sphere mm. external radioactivity is second diameter and surrounded photocathode). also by On serves to 42 the increase second 10-inch total prototype, Hamamatsu light we R7081-100 decided yield. PMTs to Their use shape light optimisation concentrators method is described3. in the next section. Concentrator shape optimisation method [4]) which considers theshape shape calculation of based on the based photocathode. on the2 Figure Stringillustrates method. the concentrator Light concentrators for large-volume detector at the Baksan Neutrino Observatory PoS(ICRC2021)1097 (1) we try / was calculated ) 1 of point ,H 2 A. N. Fazliakhmetov 1 G . Emiting a tangent to G ) ( 2 ) ,H 2 G ( 2 , we can calculate the length of 2 . ◦ /& 50 = 2 ≈ B28=C.B ?ℎ. ) 2 ' H = . Varying coordinate > 5 5 − ) 2 0 − , &, /, ), % 3 ) ! 4 H H 2DC − 4 \ with the coordinates + ( − 2 / 3 ) H 2 C>C0; Calculated cone profile. G ! + ( ( − 2 3 ) G 4 ( G − Figure 3: 3 G ( and the residual 0 ! . Then we randomly chose the point 2 ,% The calculated concentrator shape is presented in3. Figure The diameter of the exit aper- 1 , % ture (224 mm.) is areasons. little bit more Because than of the thelength diameter limited of of the the size PMT cone of photocathode is the dueexit bounded to water aperture by construction tank 300 size. and mm. supporting Theyield The grid nearly entrance cone 3 constraints, shape aperture times is the compared diameter optimized to total is bare for 405 this PMT and mm. length and given The concentrator increases light Light concentrators for large-volume detector at the Baksan Neutrino Observatory the scintillation sphere and solving the system of equations: we obtain the coordinates ofin the the touch-point Q. same The way. coordinate Havingthe of the modified point coordinates string of points to minimize residual. Repeatingsurface. this algorithm, we obtain a set of points characterizing the cone 4. Results PoS(ICRC2021)1097 , (1996) 579. J. Phys. Conf. , 370 Light concentrators A. N. Fazliakhmetov ]. , Academic Press, Burlington (2004) 453. 1909.03229 530 Light concentrators for Borexino and CTF (2021) 012037. 5 Nonimaging Optics (2020) 162920[ Nuclear Instruments and Methods in Physics Research 1787 , 951 Modeling of a MeV-scale Particle Detector Based on Organic Liquid New large-volume detector at the Baksan Neutrino Observatory: J. Phys. Conf. Ser. , Baksan large volume scintillation telescope: a current status Nucl. Instrum. Meth. A , (2020) 012244. 1468 Now the concentrator prototype is under development. It will be made of carbon-fibre- This work was supported by the Russian Foundation for Basic Research (project No. 20-32- (2005), . https://doi.org/10.1016/B978-012759751-5/50004-X for the Sudbury Neutrino Observatory Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Nuclear Instruments and Methods in PhysicsSpectrometers, Research Detectors Section and A: Associated Accelerators, Equipment Detector prototype Ser. Scintillator [5] G. Doucas, S. Gil, N. Jelley, L. McGarry, M. Moorhead, N. Tanner et al., [4] R. Winston, J.C. Miñano and P. Benítez, [6] L. Oberauer, C. Grieb, F. Feilitzsch and I. Manno, reinforced polymer with chrome-based reflective surface insideally, and both matte surfaces finish of outside. the concentrator Addition- will be covered with a protective layer. 5. Acknowledgments 90059/20) and the Russian Science Foundation (project No. 17-12-01331). References [1] N.A. Ushakov et al., Light concentrators for large-volume detector at the Baksan Neutrino Observatory [2] V.B. Petkov et al., [3] Y.M. Malyshkin et al.,