The BAIKAL-GVD project of a km3-scale neutrino telescope in Lake Baikal Vladimir Aynutdinov for the Baikal Collaboration Beijing, 17 August, International Cosmic Ray Conference 1

A.V. Avrorin 1, V. M. Aynutdinov 1, I. A. Belolaptikov 3, D. Yu. Bogorodsky 2, V.B. Brudanin 3, N. M. Budnev 2, I. A. Danilchenko 1, G. V. Domogatsky 1, A. A. Doroshenko 1, A. N. Dyachok 2, Zh.-A. M. Dzhilkibaev 1, S. V. Fialkovsky 5, O. N. Gaponenko 1, K. V. Golubkov 3, O. A. Gress 2, T. I. Gress 2, O. G. Grishin 2, A.M. Klabukov 1, A. I. Klimov 8, K.V. Konishchev 3, A.V. Korobchenko 2, A. P. Koshechkin 1, F.K. Koshel 1, V.A.Kozhin 4, V. F. Kulepov 5, D. A. Kuleshov 1, L. A. Kuzmichev 4, V. I. Ljashuk 1, S. P. Mikheev j, M. B. Milenin 5, R. A.Mirgazov 2, E. R. Osipova 4, A. I. Panfilov 1, A.L. Pan’kov 2, L.V. Pan’kov 2, A.A.Perevalov 2, D.A.Petukhov 1, E.N.Pliskovsky 3, V. A. Poleshchuk 2, E. G. Popova 4, M. I. Rozanov 7, V. F. Rubzov 2, E. V. Rjabov 2, A. V. Shirokov 4, B. A. Shoibonov 3, A. A. Sheifler 3, A.V. Skurikhin 4, Ch. Spiering 6, O. V. Suvorova 1, B. A. Tarashchansky 2, A. S. Yagunov 2, A. V. Zagorodnikov 2, V. A. Zhukov 1, and V.L. Zurbanov 2 1 Institute for Nuclear Research, Moscow, Russia 2 Irkutsk State University, Irkutsk, Russia 3 Joint Institute for Nuclear Research, Dubna, Russia 4 Institute of Nuclear Physics, Moscow State University, Moscow, Russia 5 Nizhni Novgorod State Technical University, Nizhni Novgorod, Russia 6 DESY, Zeuthen D-15738, Germany 7 St. Petersburg State Marine Technical University, St. Petersburg, Russia 8 Russian Research Center Kurchatov Institute, Moscow, Russia 2

1.Introduction 2.Baikal Neutrino Experiment - overview 3.Future Gigaton Volume Detector in Lake Baikal (BAIKAL-GVD ) - GVD technical design - Prototype GVD string: Prototype GVD cluster: Plans 5. Summary 3

A N N KM3NeT IceTop: 81 stations IceCube array: 86 strings, 5160 OM IceCub e NT200+ NEUTRINO TELESCOPES ANTARES 12 strings, 885 OM 11 strings, 228 OM Baikal-GVD project 96 strings, 2304 OM 4

5 Baikal, nm Absorption cross section, m -1 Scattering cross section, m -1 Shore cable mounting Deployment 1370 m maximum depth. Distance to shore ~4 km No high luminosity bursts from biology. Deployment simplicity (ice as a deployment platform). The BAIKAL Site Baikal water properties: Abs.Length: 22 ± 2 m Scatt.Length: m Lake Baikal, Siberia

Central part - NT200 8 strings (192 optical modules ) Height x  = 70m x 40m, V inst =10 5 m 3 Effective area: 1 TeV~2000m² Eff. shower volume: 10 TeV~ 0.2 Mton NT200+ = NT outer strings 228 optical modules Height x  = 210m x 200m, V inst = 4  10 6 m 3 Eff. shower volume: 10 4 TeV ~ 10 Mton Status of Baikal experiment ~ 3.6 km to shore, 1070 m depth NT200+ is operating now in Baikal lake The Baikal collaboration follows since several years a R&D program for a kilometer-scale Gigaton Volume Detector in Lake Baikal (BAIKAL-GVD). The main scientific goal of GVD is to map the high-energy neutrino sky in the Southern Hemisphere including the region of the galactic centre. 6

String section, 12 OM R ~ 60 m L~ 350 m Optimization Basic simulation parameters: Z - the vertical distance between OMs R - the distance between strings and cluster center H - the distance between cluster centers. Trigger conditions Hardware trigger: coincidences of nearby OM (threshold 0.5&3 p.e.). Software selection: muons – 6 triggered channels at 3 strings; cascades – 4 channels at 3 strings. An optimum for cascade detection volume and muon effective area: H=300 m, R=60 m, and Z=15 m Eff. cascade volume (trigger level) : V eff ~0.3–0.8 km 3, δ(lgE) ~0.1,  θ med ~ 3 o - 7 o (E>50TeV) Eff. muon area (trigger level): S eff ~ 0.2 – 0.5 km 2,  θ med ~ 0.5 o - 1 o (E: 10TeV - 1PeV) BAIKAL-GVD Layout 96 Strings × 24 OM String: 2 Sections × 12 OM Clusters  8 strings 2304 Optical Modules 7 12 clusters of strings 1 km

String section – low level DAQ unit Section: 12 Optical Modules & Central Module Glass pressure sphere VITROVEX (17”) OM electronics: Amplifier, HV DC-DC, OM controller Mu-metal grid PMT R7081HQE : D=10”, ~0.35QE Elastic gel 2 on-board LED flashers: 1…10 8 pe., 430 nm, 5 ns Optical Module 3 ADC boards:12 FADC channels, 200 MHz 1 OM slow-control board - Data communication between OM and CM via an underwater RS-485 bus - OM power control. 1 Master board - Trigger logic - Data readout from ADC boards - Connection via local Ethernet to the cluster DAQ center (DSL-modem, 1.2 km cable, 8 Mb ). 8

XP1807 R8055 R7081HQE R8055 BAIKAL-GVD prototype strings: in-situ tests 2009, 2010 Time parameter estimations Tests with LED LED flasher produces pairs of delayed pulses. Light pulses are transmitted to each optical module (channel) via individual optical fibers. Time between pulses dT are calculated from the waveform data. Time resolution:  (dT) = 1.6 ns Tests with LASER  T = dT EXPECTED = (r 2 -r 1 )  c water dT LASER - time difference between two channels measured for Laser pulses. LASER 110 m OM#7 OM#8 OM#9 OM#10 OM#11 OM#12 OM#1 OM#2 OM#3 OM#4 OM#5 OM#6 97 m r1r1 r2r2 Time error:  T ~ 2 ns 9

BAIKAL-GVD prototype cluster: 2011 In April 2011, a prototype cluster of GVD has been installed near NT200+ and commissioned in Lake Baikal. The cluster consists of 3 vertical strings with 8 optical modules each, deployed at depths between 1205 m and 1275 m. The vertical spacing between OMs is 10 m and the horizontal distance between strings is about of 40 m Sketch of prototype cluster, neutrino telescope NT200+, and communication lines locations. 10

Cluster technical design Optical modules The OMs house photomultipliers of different types: 16 PMT R7081HQE (Hamamatsu 10”) 5 PMT R8055 (Hamamatsu 13”) 3 PMT XP1807 (Photonis 12”) Strings 8 optical modules Central module (CM) with 8 FADC channel: 200 MHz, 12 bit. Service module (SM): OM power supply. 3 modules of acoustic positioning system - 2 cm resolution Cluster DAQ center Cluster DAQ center provides the string triggering, power supply, and communication to shore. Communication lines Connection between the strings and cluster DAQ center: 1.2 km carrier cable. Connection to shore – optical cable 6 km. 11

Cluster DAQ center Data from 3 strings are transferred through 8 Mbit DSL-modem to the cluster DAQ center. 3 DSL-modems are installed in PC-module. DAQ center is connected to shore by two optical 1Gbit Ethernet lines. Optical converters and power units are installed in Adjunction box. Communication Center (CC) provides global trigger and string power supply. CCРС GASIK Adjunction Box Shore optical cable 6 km length 3 pairs of optical fibers 3 copper lines Block diagram of the cluster DAQ center 12

Final technical design: Full scale GVD string with 24 OM Preproduction: 2012–2013(14). Full scale GVD cluster, 8 strings (192 OMs). Production (preliminary) Cost estimation 25 MEuro  2014–2015: Effective volume 0.1 – 0.3 km 3  2016–2017: Effective volume 0.3 – 0.6 km 3  2017–2018: Effective volume 0.6 – 0.9 km 3 Plans 13

Summary 1. Neutrino telescope NT200 is working in Lake Baikal for more than 10 years. 2. Preparation towards a km 3 -scale Gigaton Volume Detector in Lake Baikal is currently a central activity: - In-situ tests of the prototype string shows good performance of all string elements ( ). - A prototype GVD cluster with 3 strings was installed (2011) - New technology shore cable with optic channels was mounted (2011). 3. GVD Technical Design Report was prepared (2011) 4. Full scale GVD cluster (~200 OMs) is expected at 2013(14). 14

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