Gigaton Volume Detector in Lake Baikal: status of the project Zh.-A. Dzhilkibaev (INR, Moscow) Zh.-A. Dzhilkibaev (INR, Moscow) for the Baikal Collaboration for the Baikal Collaboration QUARKS-2010, Kolomna, 6-12 June, 2010

1. Institute for Nuclear Research, Moscow, Russia. 2. Irkutsk State University, Russia. 3. Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia. 4. DESY-Zeuthen, Zeuthen, Germany. 5. Joint Institute for Nuclear Research, Dubna, Russia. 6. Nizhny Novgorod State Technical University, Russia. 7. St.Petersburg State Marine University, Russia. 8. Kurchatov Institute, Moscow, Russia.

Telescope (E,  ) input water, ice Physics (  E,   ) Target muon (  ) cascade ( e     ) output muoncascade E,E, muons (long tracks) -   ~ 0.3 o – 1 o,   ~ 0.3logE cascades –   > 30 o (ice);   ~ 3 o – 6 o (water) ! Cherenkov radiation cascades muon Absorption Scattering Detection Principle – M. Markov 1960 energy, direction resolution L s < 3 m L s ~ m 42 o

A NT200+/Baikal-GVD (~2017) N N KM3NeT (~2017) /IceCube Amanda/IceCube(~2011) ANTARES 73 Strings in operation

Precursors of km3-scale neutrino telescopes: NT200 AMANDA ANTARES (Baikal) (South Pole) (Mediterranean Sea) Results: Astrophysics HE-neutrinos WIMPs in the Sun & the Earth Neutrinos from GRB Atm. neutrino flux Magnetic monopoles etc. Obtained results prove the detection principle and motivate the requirements of km3-scale facilities IceCube (South Pole) GVD (Lake Baikal) KM3NeT (Mediterranean Sea) MACRO Limits on all flavor HE neutrino flux

IceCube (South Pole) 4800 Optical Modules 80 Strings m depth ~1 km 3 instrumented volume Ice-Top – shower detection Deep Core – low-energy neutrinos 6 additional strings with dense OM spacing yr (Deep Core) – installed IceCube will be completed in 2011/ : 13 Strings : 8 Strings : 1 String : 18 Strings 1450 m 2450 m : 18+1 Strings

KM3NeT (Mediterranean Sea – TDR 2010)  8-inch PMT31 3-inch PMTs Optical Module ? Research Infrastructure Detection Unit (DU) ? Buoy OM Slender String 300 DU SITE ? Flexible tower 127 DU

Next Steps and Timeline  Next steps: Prototyping and design decisions - organised in Preparatory Phase framework - final decisions require site selection - expected to be achieved in ~18 months  Timeline: CDR: TDR: Mar 2012 Design decision Construction Data taking 2015

4км from the shore 1366 м depth Shore Station Location of the BAIKAL neutrino telescope

Location: - Northern hemisphere – GC (~18h/day) and Galactic Plane survey - Flat 1350 m depth Lake bed (>3 km from the shore) – allows ~ 30 km 3 Instr. Volume! 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 – m - Scattering length – 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

Since 1980 Site tests and early R&D started 1990 Technical Design Report NT NT NT36 started: - the first underwater array - the first neutrino events NT200 commissioned: 1998 NT200 commissioned: start full physics program. NT200+ commissioned (NT200 & 3 outer strings) NT200+ commissioned (NT200 & 3 outer strings) Start R&D toward the Gigaton Volume Detector (GVD) 2008 In-situ test of GVD electronics: 6 new technology optical modules 2008 In-situ test of GVD electronics: 6 new technology optical modules Prototype strings for GVD Prototype strings for GVD GVD cluster (3 strings), Technical Design Report GVD cluster (3 strings), Technical Design Report

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 Quasar photodetector (  =37cm) NT200+ = NT outer strings (36 optical modules) Height x  = 210m x 200m, V inst = 5  10 6 m 3 Eff. shower volume: 10 4 TeV ~ 10 Mton Status of NT200+ LAKE BAIKAL ~ 3.6 km to shore, 1070 m depth NT200+ is operating now in Lake Baikal (~10 months/yr. persistent data taking)

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 > 10 TeV - Diffuse neutrino flux – energy spectrum, local and global anisotropy, flavor content - Transient sources (GRB, …)

ClasterStr. section m GVD - Preliminary design Layout: ~2300 Optical Modules, 96 Strings, 12 Clusters String comprises 24 OMs, which are combined in 2 independent Sections Cluster contains 8 strings Instrumented volume: 0.4 – 0.6 km 3 Detection Performance Cascades: ( E>100 TeV): V eff ~0.3 – 0.8 km 3 δ(lgE) ~0.1, δθ med ~ 3 o -6 o Muons: ( E>10 TeV): S eff ~ 0.2 – 0.5 km 2 δθ med ~ 0.3 o -0.5 o

Cable communication to shore 1370 m maximum depth Distance to shore 4 … 5 km 12 clusters × 192 OM 12 cables ~ 6 km GVD cluster 12 Shore cables ~6 km 1350…1370 m Shore Center 12 GVD clusters NT200+

Optimisation of GVD configuration (preliminary) Parameters for optimization: Z – vertical distance between OM R – distance between string and cluster centre H – distance between cluster centres Muon effective area R=80 m R=100 m R=60 m The compromise between cascade detection volume and muon effective area: H=300 m R = 60 m Z = 15 m Trigger: coincidences of any neighbouring OM on string (thresholds 0.5&3p.e.) PMT: R7081HQE,10”, QE~0.35

GVD – R&D ( ) GVD - Key Elements and Systems: - Optical Module - FADC-readout system - Section Trigger Logics - Calibration - Data Transport - Cluster Trigger System, DAQ - Data Transport to Shore OM 12 OMs2 Sections8 Strings to Shore SectionStringCluster

Optical module XP1807(12”), R8055(13”) ‏, R7081HQE(10”) QE ~0.24 QE ~0.2 QE~0.35 HV unit: SHV12-2.0K,TracoPower OM controller Amplifier: K amp = 10 LED calibration system (2 LEDs) Functional scheme of the optical module electronics XP1807 R8055 R7081 HQE Relative sensitivities of large area PMs R8055/13” and XP1807/12”

Measuring channels BEG PMT 1 AmplifierFADC 1 90 m coax.cable OM PMT 12 AmplifierFADC m coax. cable … BEG (FADC Unit) -3 FADC-board: 4-channel, 12 bit, 200 MHz; -OM power controller; -VME controller: trigger logic, data readout from FADC, connection via local Ethernet

Section – basic detection unit Section: - 12 Optical Modules - BEG with 12 FADC channels and trigger unit - Service Module (SM): LEDs for OM calibration, OM power supply, acoustic positioning system. Basic trigger: coincidences of nearby OM (threch. ~0.5&3 p.e.) expected count rate < 100 Hz Communications: BEG  cluster centre: DSL-modem, expected dataflow < 1Mbit/s BEG  OMs: RS-485 Bus (slow control)

Cluster DAQ center Cluster of strings 8 Strings String consists of 2 sections (2×12 OM) Cluster DAQ Centre (4 modules) 1. PC-module with optical Ethernet communication to shore (data transmission and synchronization) 2. Trigger module with 8 FADC channels (time mark of string trigger) 3. Data communication module (8 DSL-modems for communication to strings, ~10 Mbit/s for 1 km ) 4. Power control system

In-situ tests of basic elements of GVD with prototypes strings ( ) 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 XP OM Hamamatsu R OM PMT: Hamamatsu R7081HQE 7 OM Hamamatsu R OM GVD prototype strings

R7081HQE R8055 Prototype string deployment: April 2010 PC BEG1 SM BEG2

Time resolution of measuring channels (in-situ tests with LED) LED flasher produces pairs of delayed pulses. Light pulses are transmitted to each optical module (channel) via individual optical fibers. Delay values are calculated from the FADC data. Measured delay dT between two LED pulses LED1 and LED 2 pulse amplitude Example of a two-pulse LED flasher event (channel #5) LED1 LED2  (dT) 1.6 ns

Time accuracy (in-situ test with Laser) 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 Differences between dT measured with Laser and expected dT in dependence on distances between channels dr  T < 3 ns Test with LASER  T = dT EXPECTED = (r 2 -r 1 )  c water dT LASER - time difference between two channels measured for Laser pulses (averaged on all channel combinations with fixed (r 2 -r 1 ))

Distribution of time difference  T between muon pulses for two up-ward looking PMTs: experiment and expectation from atm. muons.  T between muon pulses detected with different channels are studied and compared with simulation of the string response to the atmospheric muon flux. Trigger: 3-fold OM coincidences Muon detection MC

Monitoring of Optical Module operation OM temperature PMT voltage OM monitoring parameters: - PMT high voltage; - PMT count rate; - Temperature; - OM low voltages: 12 V, 5 V, -5 V … OM3 OM5 Example of PMT voltage monitoring : Example of PMT count rate monitoring

Schedule: >2006 Activity towards the Gigaton Volume Detector Prototype Strings ( test of GVD key elements and systems) Technical Design Report Preparatory Phase, Prototype of Cluster (in-situ test) Fabrication (OMs, cables, connectors, electronics) Construction ( ) GVD