1. BAIKAL-GVD: status, results and plans Zh.-A. Dzhilkibaev, INR (Moscow), for the Baikal Collaboration for the Baikal Collaboration Amsterdam, October 17, 2015

2. The site

3. Shore station Ice thickness ~ 60-90 cm (sometimes up to 120 cm) Winter expedition Summer expedition Day temperature Baikalsk Jan Jun Dec 25-30 m 900 m

4.  Nominal PMT gain 1  10 7 (PMT voltage 1250 – 1650 V)  Amplifier, k amp =10;  Pulse width ~20 ns  ADC: 12 bit 200 MHz FADC (5 ns time bin);  Waveform information is recorded in a programmable interval (up to 30 mks)  Linearity range: 1 ─ 100 p.e.; Measuring channel Time, 5 ns A, mV PMT Amplifier FADC 90 m coax.cable Optical module Central module threshold

5. Triggering and Data Transmission SECTION CLUSTER ADC 200MHz 12 bit 12 channels

6. Engineering arrays (2012-2015) 2012 3 strings, first full-scale GVD string (24 ОМs) Data taking from April 2012 yr. 2013 3 full-scale strings (72 OMs), update of section electronics Data taking from April 2013 yr. 2014 5 strings (120 OMs) Data taking from April 2014 yr. DAQ

7. Section module development 2012 - 6 circuit boards & Eth Modem - FPGA Spartan 3 TrRate MAX  10 Hz; Thr: 4-fold coin. 2013 - FPGA Spartan 6 - on-line zero suppression TrRate MAX  50 Hz; Thr: 3-fold coin. 2014 - 2 circuit boards & Eth Modem - FPGA Spartan 6 TrRate MAX  100 Hz; Thr: 1.5×4 pe. 2015 - Hardware level of zero suppression TrRate MAX  1000 Hz; Thr: 0.5×3 pe. DAQ History Section central module 2012 - 2013 Section 2015 Section central module 2013 - 2014 Problem: Eth. Modem (1 km)  10 Mbit/s One ADC frame = 2048 Byte (5 mks)

8. Expedition plans on 2015  Three new Strings  Completion of reduced-size String #2  Replace Spartan-3 to Spartan-6 in two Masters in String #7  Replace acoustic modem on String #1  Add one additional section to one standard String

9. 2015: Unusually warm winter

10. Stage 1 Timeline: 3-5 days Divers attach the rope to the top of the string Using echo-sounding device 10.03 – 27.03 – work on ice

11. 15.03 – 23.03 - deployment of 3 new strings

12. First Demonstration Cluster “DUBNA” (April 2015) String section, 12 OMs R ~ 40 m L~ 345 m  192 OMs at 8 Strings 2 Sections per String 12 OMs per Section  DAQ-Center  Cable to Shore  Acoustic Positioning System  Instrumentation String with detector calibration and environment moni- toring equipment  Two LED beacons for interstring calibration Active depth 950 – 1300 m Instrumented volume 1.7 Mt Cable MEOC - OE Cable Buoy Station - Instrumentation string - DAQ center Final Layout

13. №1 198(d) 197(u) №2 206(d) 200(u) №3 192(d) 199(u) №4 202(d) 201(u) №5 204(d) 195(u) №6 203(d) 205(u) №7 191(d) 196(u) №8 194(d) 193(u)  4 OMs out of operation  1 acoustic modem at Str.1 Status after deployment

14. Operation - 2015 Cumulative number of records The time difference between subsequent events. 3 April – 1 October - 181 days Operation: 117 days Efficiency: 64.6.1% Total: 259 Runs Data : 5.12∙10 8 events Record rate ~ 500 Hz

15. April – October 2015 Operation - 2015  Sections connection losses

16. Operation - 2015  Performance of acoustic positioning system:  data every 30 seconds  high resolution ~ 3-5 cm L = c∙t/2, c ~ 1500 m/s

17. 06/05/13 Coordinates of transponder: May-2015 timeX, m Y,m Z,m X, m Y,m Z,m

18.  Amplitude calibration LED1 Low Int. LED2 high Int. Calibration methods: 1 – two LEDs with high and low (~10% OM detection probability) intensities 2 – analysis of noise pulses 1 ph.el. Code/ph.el. OM number

19.  Time calibration – two methods PMT signal delay = dt-dt 0 Signal delay of each channel LED 15 m- distance between OMs dT 0 = 64.9 ns – expected time difference Time difference of two channels dt 0 =500 ns The time delays of the channels measured with a reference pulse depending on the PMT voltage (72 channels, strings 4, 5, 6 ). Consistency of two calibration procedures dT LED – dT TST OM number

20. Str#2 vs Str#8 Calibration of different strings with LED beacon LED beacon comprises 6 pairs of blue LEDs: six pointed upward and six pointed horizontally. Acoustic positioning system provides string coordinates. 6 7 5 1 2 3 4 8 LED beacon 42 3 1 8 5 OM#185 Time offset of Str#8 vs Str#5 Time difference between OMs: expected and measured values. expected data Calibration accuracy ~2 ns (including channel calibration uncertainties).

21. GVD - I OMs2302 Clusters (8 Strings) 8 Sections (12 OMs) 3 Sec./Str. Depths, m750 – 1275 Instr. volume0.4 km 3

22. Upgrade of DUBNA array in 2016  288 OMs at 8 Strings 3 Sections per String 12 OMs per Section  DAQ-Center  Cable to Shore  Acoustic Positioning System  Instrumentation String with detector calibration and environment moni- toring equipment  Two LED beacons for interstring calibration Active depth 750 – 1275 m Instrumented volume 6.0 Mt Cable MEOC - OE Cable Buoy Station - Instrumentation string - DAQ center R ~ 60 m 525 m  96 OMs at 8 sections  Replace system modules on Str.#7  Replace acoustic modem on Str.#1

23. JINR (Dubna)

24. GVD-1 timeline -pro Cumulative number of clusters vs. year Year201520162017201820192020 Cluster 192 OM 1 192 1 192 3 576 5 960 7 1344 10 1920 Cluster- 288 OM 2/3 192 1 288 2 576 4 1152 6 1728 8 2304

25. Conclusion: The first demonstration cluster “Dubna” of GVD was deployed and commissioned in April 2015 In the 2016 cluster “Dubna” will be upgraded to baseline configuration comprising 288 OMs Completion of the GVD Stage 1 is expected in 2020

26. 2015: FIRST GVD-CLUSTER “DUBNA”

27. Cluster performance for cascades detection Reconstruction of a cascade vertex: Iterative procedure- OMs with residual δt > 15 ns are excluded and final N hit is obtained for following analysis. δr = |r rec – r gen | ~ 2 m (median value) Distance between generated and reconstructed vertices Energy resolution for cascades: δE/E ~ 30%, averaged by E -2 e spectrum Averaged by E -2 e spectrum Averaged by E -2 e spectrum N hit > 10 (Zh.Dzhilkibaev, session D)

28. Directional resolution for cascades: Median value of mismatch angles ~ 3 °- 4° depending on energy and cuts Distribution of mismatch angles Cumulative distribution N hit > 10

29. Neutrino Effective Area GVD-Cluster: Events per Year from IC-flux (E 2 F IC =3.6·10 -8 GeV cm -2 s -1 sr -1 ) ~1 Event/Year (>100 TeV) Cut on number of hit OMs after vertex reconstruction significantly suppresses background atm. neutrinos Applied cuts: N hit > 20; E rec > 100 TeV

30. Sensitivity on one flavor E -2 flux (preliminary, without systematics) 5 σ discovery potential for IC neutrino flux with E -2 spectrum Applied cuts: N hit > 20 (after vertex reconstruction) Vertex reconstruction filter: -270< z rec <200 m (OMs location: -172.5  +172.5 m) E rec > 100 TeV Expected number of events for 1 year exposition: Signal: 1 ev. from astrophysical IC flux (3.6x10 -8 GeV cm -2 s -1 sr -1 ) Background: 0.05 ev – atm. ; 0.05 ev. – atm. μ Cluster performance for cascades detection

31. Baikal-GVD: performance 31 E > 100 TeV: ~1 event/cluster/year Expected #events from IC flux E 2 F IC =3.6·10 -8 GeV cm -2 s -1 sr -1

32. 1. Optical modules: One OM connector (SubConn LF, 5 pin) instead of two coax. conn: - reliability increasing; - separation of power supply and analog pulse lines  decreasing the channel thresholds (0.5 p.e. to 0.25 p.e.) 2. Section central module electronics: - 2013: Master boards : new FPGA Xilinx “Spartan 6” instead of “Spartan 3” for on-line data processing (cut out waveform data without pulses). - 2014: new 12-channels ADC board instead 4-ch ADC. ADC modernization and on-line data processing provides increasing the event transmission rate with 10 Mbit DSL-modem to factor ~100 (10Hz  1 kHz) Main modernizations ( ) 12-ch 200 MSPS ADC

33. Time calibration – two methods PMT signal delay = dt-dt 0 Signal delay of each channel LED 15 m- distance between OMs dT 0 = 64.9 ns – expected time difference dT Time difference of two channels dt 0 =500 ns The time delays of the channels measured with a reference pulse depending on the PMT voltage (72 channels, strings 4, 5, 6 ). Consistency of two calibration procedures dT LED – dT TST