1. The prototype string for the km3 scale Baikal neutrino telescope VLVnT08 22-24 April 2008 Vladimir Aynutdinov, INR RAS for the Baikal Collaboration for the Baikal Collaboration Toulon, 24 April 2008

2.  Institute for Nuclear Research, Moscow, Russia.  Irkutsk State University, Russia.  Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia.  DESY-Zeuthen, Zeuthen, Germany.  Joint Institute for Nuclear Research, Dubna, Russia.  Nizhny Novgorod State Technical University, Russia.  St.Petersburg State Marine University, Russia.  Kurchatov Institute, Moscow, Russia. Collaboration

3. Outline Introduction 1. Prototype string as part of NT200+ 2. Design and installation 3. Preliminary in-situ tests Summary

4. Ultimate goal of Baikal Neutrino Project: Gigaton (km3) Volume Detector in Lake Baikal Sparse instrumentation: 91 – 100 strings with 12 – 16 OMs (1300 – 1700 OMs) - Effective volume for >100 TeV cascades - ~ 0.5 -1.0 km³ dlg(E) ~ 0.1, d θ med < 5 o - Detects muons with energy > 10 - 30TeV 624 m 280m 70m 120 m 208m Introduction

5. Km3 Baikal Neutrino Telescope NT200+ current status Prototype string Installation of a “new technology” prototype string as a part of NT200+ (spring 2008)  Investigations and in-situ tests of basic elements of future detector: optical modules, DAQ system, new cable communications.  Studies of basic DAQ/Triggering approach for the km3-detector.  Confrontation of classical TDC/ADC approach with FADC readout. Objectives of string installation External string

6. Prototype string as part of NT200+ 1. Data communications between shore station, central uw-PCs, and external string controllers (Str1... Str3) on the basis of DSL-modem 2-wire line. 2. Time synchronization: the measuring of time interval between string trigger (request) and global trigger (acknowledgement): Time accuracy 2 ns 3. Prototype string data communication and time synchronisation are the same as for external string. NT200 Str1 Str2 Str3 Protot. Str DSLTrigger uwPC Prototype string - FADC unit - PC unit - LED flasher - 6 OMs ~1 km depth To shore (DSL- modem line, 1 Mbit) LASER Time synchronization: Request & Acknowledgment signals DSL-modem line: data & control

7. 60 m Basic string elements (1) FADC sphere: 8-channel 12-bit 200 MHz FADC + Ethernet controller. (2) String PC unit: Data transmission and OMs control (3) LED Flasher unit: OM time and amplitude calibration 6 optical modules: 4 x PM XP1807 (Photonis). 2 x PM R8055 (Hamamatsu) 1 2 3 String control center Optical Module (OM)

8. FADC unit Analog outputs of all 6 PMs are connected through coaxial cables with 8-channel 12 bit 200 MHz FADC board, located in the FADC unit. (two FADC channels are used to measure low-gain channels of two upper PMs) OM power supply (12V) is provided through the analog cables (with possibility to switch on/off each individual module). String trigger is formed by the FADC controller: 1….4-fold majority trigger within coincidence window 10ns … 1 us. 1 2 3

9. String PC unit Data from the FADC are transmitted through an Ethernet line to the underwater micro-PC for on- line analysis and data-compressing. Communication between PC-unit and underwater control center of NT200+ is provided by DSL modems trough 2-wire line about 1 km length (twisted pair, now @ 2Mbps). OM slow control and monitoring and LED flasher operation is provided by PC unit through RS-485 underwater bus. The main slow control functions are the regulation of PM high voltage, the control of LED flasher intensity and pulse delay, and the measurement of the PMT rates. String PC unit – rather a temporary solution. Future: integrate into FADC unit. 1 2 3

10. LED Flasher Time and amplitude calibration is provided by the string LED flasher unit. Light pulses from flasher are transmitted to each OM through plastic optical fibers with calibrated length. The LED flasher provides all relative time shifts, and allows to monitor the single electron spectrum of all PMs. The LED flasher glass sphere also houses the low noise DC-DC converters for the OM power supply. DC-DC noise amplitude ~3 mV << A(1 p.e.) LED flasher parameters: - 2 independent LED - Pulse FWHM ~ 5 ns - Pulse delay between LED1/2 from 0…1000 ns (10 steps) - Pulse amplitude can be set from 1 to 200…1000 p.e. on PMs (~10 4 steps). 1 2 3

11. Optical Module (OM) 1.PMT: XP1807 (Photonis, ~12”) R8055 (Hamamatsu, ~13”) Divider 17 MOhm Gain 3...5 x 10 7 2.Preamplifier: K a ~ 5 for high gain ch. K a ~1.5 for low gain ch. 3.HV unit: PHV12-2.0K DC-DC converter VIP-2A (Irkutsk) converter 4. OM controller: microcontroller C8051F124 - RS-485 interface - PM pulse counter with regulated threshold - HV monitor - 2-LED calibration system (LED amplitude and pulse delay regulation, like in LED Flasher Unit).

12. Upward looking OM

13. Cable communications Time synchronization with NT200+: 2 coaxial cable, Trigger Request & Acknowledgment Connection to NT200+ centre: DSL 2-wire line, 2 Mbps OM slow control: RS-485 bus with coaxial cable FADC and PC unit connection: Ethernet with 2 coaxial cables OM signal & power supply: individual coaxial cable to each module Time calibration with LED flasher: individual optical fiber to each module

14. Prototype string installation

15. Basic parameters of prototype string Number of optical modules: 6 Number of spectrometrical channels: 8 Type of PMT: XP1807 (12”), R8055 (13”) Dynamic range: high gain chan. 0.2 … ~100 p.e (*) low gain chan. 0.5 … ~300 p.e. Time window: 5 mks Time resolution: < 5 ns (*) – range of spectrometrical channel linearity

16. Final string deployment.... 7.4.2008

17. Prototype string in-situ tests (LED flasher) Time shift estimation with LED flasher: time difference between neighbored OMs OM#1 OM#2 OM#3 OM#4 OM#5 OM#6 3 2 1 4 6 5 ~20 m coax cable ~20 m A, V Example of LED flasher event PRELIMINARY ~20 m coax cable ~20 m

18. Prototype string in-situ tests (Laser events) Example of laser event measured with all channels (time shift correction with LED flasher) 2 1 3 6 5 4 PRELIMINARY OM#1 OM#2 OM#3 OM#4 OM#5 OM#6 50 m LASER Examples of laser events measured with OM#2 (low gain channel) for 5 laser intensities I1I2 I3 I4\I5 Laser RUN: events rate vs. time. 5 laser intensities: I1, I2,…,I5. I i /I i+1 ~ 2.5…3

19. Prototype string in-situ tests (muon events) Examples of down-going muon events Trigger: 3-fold coincidence 2 1 3 6 5 4 PRELIMINARY OM#1 OM#2 OM#3 OM#4 OM#5 OM#6

20. Summary 1. For the planned km3-detector in Lake Baikal, R&D-activities have been started. R&D-activities have been started. 2. The existing NT200+ allows to verify all key elements and design principles of the km3-detector. and design principles of the km3-detector. 3. A “new technology” prototype string with 6 OMs and FADC technology was installed in spring 2008 and FADC technology was installed in spring 2008 as a part NT200+. as a part NT200+. 4. First in-situ tests of the prototype string with underwater laser, LED flasher and muons shows good performance of all string elements.