1. 1 Detector of the reactor AntiNeutrino based on Solid-state plastic Scintillator (DANSS) M.Danilov M.Danilov Representing the DANSS Collaboration (ITEP (Moscow) & JINR(Dubna)) (ITEP (Moscow) & JINR(Dubna)) ICHEP-2014 Valencia July 5 th, 2014 Sensitivity of the DANSS detector to short range neutrino oscillations

2. 2 DANSS Goals Cosmic muon veto ( PS plates) Sensitive volume ~ 1m 3 (2500 PS strips) Cu frames (inner part of passive  -shielding ) Pb (external part of passive  -shielding) CH 2 + B (n-shielding) Reactor monitoring using neutrinos: 1. to measure the thermal reactor power with accuracy of 1.5% per day; 1. to measure the thermal reactor power with accuracy of 1.5% per day; 2. to define the fuel composition and amount of the produced 239Pu with accuracy 2. to define the fuel composition and amount of the produced 239Pu with accuracy of 6% in 10 days of measurements; Search for short range neutrino oscillations DANSS Parameters: IBD detection efficiency ~70% ν counting rate up to 10000/day Background rate ~1% Distance to reactor core (center to center) 9.7-12.2m (change in 5min) Energy resolution ~24% at 1MeV Total weight – 13t + lifting gear

3. 3 Each scintillator strip is read out individually by a Silicon Photo Multiplier (SiPM) via a WLS fiber. Sensitivity is ~15 p.e./MeV Light attenuation ~20%/m 50 strips are combined into a Module which is also read out by a small PMT (via 2 additional WLS fibers per strip). Sensitivity is ~15 p.e./MeV The frame of a Module is made of radio-pure electrolytic copper and thus shields the sensitive part against insufficiently pure components of front-end electronics placed outside the frame. Gd-containing light-reflecting coating~6mg/cm2 glue WLS- -fiber ○ 1.2 mm PS X-plane Y-plane Copper frames View of a Module (under construction). DANSS Design SiPMs (MPPC S12825-050C)

4. 4 Strip properties Transverse nonuniformity Strip response to cosmics (2.2MeV) at different distances to SiPM Near end Far end Center 35% of strips produced. All strips ready in August Strip

5. 5 Energy resolution is modest. It smears L/E like the large size of reactor core Energy Resolution GEANT4 simulation with non-uniformity of response N Number of p.e. for 5 MeV e + Ideal case L smearing L&E smearing

6. 6 Calibration Calibration is extremely important for stable energy scale Shifts in energy scale can imitate oscillations and reduce sensitivity Elaborated system of calibration is foreseen in DANSS 1. Several radioactive sources can be put into 10 special tubes inside every section of 100x100x20 cm 248 Cm neutron source provides signals similar to IBD 2. Gd signal will be monitored with 10000 events/day 3. High granularity of DANSS allows cosmic calibration with ~4000 0 events/strip/day. Cosmics spans E range 2-5 MeV for individual strips with SiPM readout and 10-40MeV for modules of 50 strips read out by one PMT 4. SiPM amplification will be calibrated continuously

7. 7 Scintillation cube of 2500 strips Each strip → SiPM Each group of 50 strips → PMT Detector readout 2500 SiPM signals 50 PMT signals 6U VME readout board 64 channels 12 bit x 125 MHz 5 Xilinx XC6S75T FPGA chips 512 Mbyte DDR3 RAM VME64x or 1 Gbit Ethernet 6U VME readout board 64 channels 12 bit x 125 MHz 5 Xilinx XC6S75T FPGA chips 512 Mbyte DDR3 RAM VME64x or 1 Gbit Ethernet 6U VME readout board 64 channels FADC 12 bit x 125 MHz 5 Xilinx XC6S75T FPGA chips 512 Mbyte DDR3 RAM VME64x or 1 Gbit Ethernet 44 boards 6U VME readout board 64 channels FADC 12 bit x 125 MHz 5 Xilinx XC6S75T FPGA chips 512 Mbyte DDR3 RAM VME64x or 1 Gbit Ethernet Dedicated trigger board trigger Trigger: ~0.2MeV threshold on total energy. No correlation between positron and neutron signals at trigger level. Maximum trigger rate < 15 kHz (prototype measurements <1kHz at 0.25MeV thr.) SiPM 1ph.e. noise level ~ 100 kHz. Average number of occupied channels ~ 15/trigger. Average event size ~ 600 bytes. Data rate ~ 9 Mbyte/s or 0.8 Tbyte/day. More complex trigger logic is also possible. 200 ns ~120 ns

8. 8 DANSS is placed on a movable platform with a lifting gear Detector distance from reactor core 9.7-12.2 m (center to center) Typical reactor building with WWER-1000 3 GW thermal power 238U + (3.5-5)% 235U 5*10^13 ν/s/cm2 @10m Core: h=3.5m  =3.12m Reservoirs with technological liquids ~ 60 mwe DANSS placed under WWER-1000 reactor at Kalinin NPP Electronics crates Lifting gear Already installed

9. 9 Handling is much safer (non-flammable, non-caustic)  no restrictions to move the detector very close to the reactor core  higher neutrino flux => better sensitivity. High segmentation (2500 strips) => space information  better IBD signature => stronger BG suppression.  possibility of continuose calibration with cosmics for every strip PS is not doped with Gd, but interleaved with it  better stability of the scintillator. Dual readout with SiPM and usual PMT => better control of systematic Detector on movable platform under reactor => better control of systematic low cosmic background DANSS advantages DANSS disadvantages Worse energy resolution in comparison with liquid scintillator Relatively large number of readout channels

10. 10 Calibration r/a source: 60 Co 22 Na 137 Cs 248 Cm ~3 n A small prototype - “DANSSino” 50+50=100 strips 20 cm  20 cm  100 cm 1/25 of the DANSS 40 kg (movable) 2 PMT (X  odd, Y  even) No SiPM readout Purpose: Study of background conditions Tests of shielding efficiency Measurements of trigger rates Properties: ν p e + n (Inverse Beta Decay) Efficiency e + (Prompt) - 47% (E>1MeV) Efficiency n (Delayed) – 28% (E>1 MeV)

11. 11 Background under reactor is order of magnitude lower than on surface Heavy material shielding increases muon induced IBD background (and IBD detection efficiency)

12. 12 Reactor power Rate of neutrino-like events detected per day Clear correlation between reactor power and DANSSino counting rate

13. Raw counting rates during reactor ON and OFF periods No change inside shielding! Thermal neutrons inside shielding (Hz)

14. 14 Spectrum simulated for 235 U fission Background subtracted rate of neutrino-like events / 0.5 MeV / day Energy MeV Neutrino rate ~ MC expectations

15. 15 True IBD Random  -n  -induced 248 Cm Delayed signal time distribution for different types of events T μsec

16. 16 Comparison of counting rates for reactor On and OFF periods for different selection criteria Evidence for neutrino detection (~70/day) with S/B~ 1 DANSSino confirmed DANSS design parameters Reliable estimates of DANSS sensitivity and background

17. Ratio of positron spectra at 12.2 and 9.7m for Δm 2 =2eV 2, Sin 2 2θ 14 =0.1 (errors correspond to million evt. at each distance - 8 months of running) Distortions are perfectly seen E [MeV]

18. Most interesting parameter space is well covered Sensitivity estimates (1 year, 90% CL, shape only, without systematics) Studies of systematic effects are in progress Preliminary results indicate small reduction of sensitivity Use of e+ spectrum and rate information increase sensitivity sin 2 2θ Δm2Δm2

19. 19 Summary Details can be found in arXiv:1305.3350 [physics.ins-det]arXiv:1305.3350 arXiv:1311.2777 [physics.ins-det] High granularity, good stability, very low background, high neutrino flux and changeable distance to reactor core should allow DANSS to study the most interesting parameter region of possible oscillations to the 4 th neutrino. DANSS design parameters have been confirmed by the DANSSino results In spite of a small size (4% of DANSS), non perfect shielding and μ veto DANSSino detected about 70 events/day with S/B ~ 1. DANSS data taking will start late in 2014

20. 20 Backup slides

21. SiPM Calibration without LED