1. SINP MSU, July 7, 2012 I.Belolaptikov behalf BAIKAL collaboration

3. Depth – 1360 m with flat bed at distance > 3 km from the shore allows > 250 km3 instrumented volume ! >250 km 3 Winter expedition Summer expedition Day temperature Site properties

4. Strong ice cover during ~2 months: - Telescope installation, maintenance, upgrade and rearrangement - Installation & test of a new equipment - All connections are done on dry - Fast shore cable installation (3-4 days) Water optical properties: - Absorption length – 22-24 m - Scattering length – 30-50 m - Moderately low background in fresh water Water properties allow detection of all flavor neutrinos with high direction-energy resolution! Site properties ice slot cable tractor with ice cutter cable layer Shore cable deployment March 2011

5. NT200: 8 strings (192 OMs) Height x  = 70m x 40m, V inst =10 5 m 3 Effective area: 1 TeV~2000m² Eff. shower volume: 10 TeV~ 0.2 Mton Quasar photodetector (  =37cm) NT200+ = NT200 + 3 outer strings (192+36 OMs) Height x  = 210m x 200m, V inst = 5  10 6 m 3 Eff. shower volume: 10 4 TeV ~ 10 Mton 1998 - NT200 2005 - NT200+ ~ 3.6 km to shore, 1070 m depth

6. Gigaton Volume Detector (GVD) in Lake Baikal R&D status Objectives: - km3-scale 3D-array of photodetectors - flexible structure allowing an upgrade and/or a rearrangement of the main building blocks (clusters) - high sensitivity and resolution of neutrino energy, direction and flavor content Central Physics Goals: - Investigate Galactic and extragalactic neutrino “point sources” in energy range > few TeV - Diffuse neutrino flux – energy spectrum, local and global anisotropy, flavor content - Transient sources (GRB, …) - Dark matter – indirect search - Exotic particles – monopoles, Q-balls, nuclearites, …

7. String section, 12 OMs R ~ 60 m L~ 705 m OM 12-16 OM2-4 Sections8 Strings To the shore Section StringCluster Structure elements of the detector

8. GVD desing Configuration 10368 Optical modules, 216 Strings: 48 OM/Str., 4 Sec./Str. 27 Clusters: 8 Str/Cluster Geometry: Z = 15 m – distance between ОМ on string R = 60 m – cluster radius H = 300 m – distance between clusters Instrumented volume: ~1.5 km 3 Depth: 600-1300 m Muons: (E>1 TeV): S eff ~ 0.3 – 1.8 km 2 ; δθ med < 0.5 o ; δlg(E/E  ) ~0.4 10368 OMs 2304 OMs 10368 OMs 2304 OMs Cascades: (E>10 TeV): V eff ~0.4 – 2.4 km 3 ; δ(E/E sh ) ~25%; δθ med ~ 5 o

9. In-situ tests of basic elements of GVD with prototypes strings (2009...2010) Investigation and tests of new optical modules, DAQ system, cabling system, triggering approaches ( LED Laser Muons) NT200+ Prototype string 2009 Prototype string 2010 PMT: Photonis XP1807 6 OM Hamamatsu R8055 6 OM PMT: Hamamatsu R7081HQE 7 OM Hamamatsu R8055 3 OM GVD prototype strings 2009 - 2010

10. Zenith angular distributions of experimental and MC-simulated events after cuts - Performance of time measuring systems. - Reliability of calibration methods. - Efficiency of background suppression. Selected sample of 2010 string data: - Trigger condition: >3 hit OMs - PMT noise: ~15kHz Noise suppression procedure: The time difference between the pulses of any pair of OMs should be smaller than the light propagation time. Muon track reconstruction: Prototype string: muon reconstruction

11. Cluster 2011 technical design Optical modules The OMs house photomultipliers of different types: 16 PMT R7081HQE (Hamamatsu,  10 inch) 5 PMT R8055 (Hamamatsu,  13 inch) 3 PMT XP1807 (Photonis,  12 inch Strings Size reduced section:8 optical modules, CM and SM. CM (Central module): 2ADC board (8 chan.), Master. SM (Service module): Control and connection to the cluster DAQ center. Acoustic positioning system, 3 modules on each string. (accuracy ~2 cm, measurements each 30 sec) 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 copper cable. Connection to shore – optical cable 6 km. 11

12. BAIKAL-GVD prototype cluster: 2011 In April 2011, a prototype cluster of GVD was installed in Lake Baikal. − 3 vertical strings with 8 optical modules each. − Vertical spacing between OMs is 10 m. − Horizontal distance between strings is 40 m. − Depths is 1205 – 1275 m. 12 Sketch of prototype cluster, neutrino telescope NT200+, and communication lines locations. NT200+ communication lines NT200+ Optical cable 2011 248 “live” days

13. Present and nearest future 2012 3-strings, first full scale GVD string (24 ОМ) Data taking since April 2012 2013 Detector with 3 full scale GVD strings 2014-2015 Cluster (8 strings)  4  10 6 м 3  10 6 м 3 DAQ

14. Preproduction: 2014–2015. Full scale GVD cluster, 8 strings (192 Oms) Production (preliminary)  2014–2018: 12-14 Clusters  2018–2020: Full scale detector ( 27 clusters ) Plans 14

15. Summary 1. 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 basic string elements (2009-2010). - A prototype GVD cluster with 3 strings was installed (2011) and shows stable work for whole year. - New technology underwater optical cable was mounted (2011). - Full scale GVD string(24 OMs) with 2 “short” strings(6 OM) taking data since April 2012. 2. Full scale GVD cluster (~200 OMs) is expected at 2014-2015. GVD Technical Design Report was prepared (2011): http://baikalweb.jinr.ru/GVD/ 15

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