SNO+ ARTFEST, MAY 2014, KINGSTON DR. CHRISTINE KRAUS, LAURENTIAN UNIVERSITY

Transcription

1 SNO+ ARTFEST, MAY 2014, KINGSTON DR. CHRISTINE KRAUS, LAURENTIAN UNIVERSITY

2 SNO+ IS LOCATED AT SNOLAB 300 km Canada Ontario Sudbury Creighton mine use existing SNO cavity 2 km or 6000 m.w.e. Artfest 2014, Christine Kraus, Laurentian University 2

3 SNO DETECTOR (INHERITED) Acrylic vessel AV, filled with 1000 tonnes of heavy water: data taking in 3 phases (different n detection methods) sunset in Sudbury DCR = Deck Clean Room 12 m acrylic vessel 1000 tonnes D2O 1700 t H2O (inner) 18 m PSUP 780 tonnes liquid org. scintillator Hold-down ropenet 5300 t H2O (outer) ~9500 PMTs 54% coverage 3

4 LIQUID SCINTILLATOR SNO+ liquid scintillator Detector to be filled with 780 tonnes of organic liquid scintillator (LS) scintillator More light yield!~100 than times Čerenkov more light, around yield than 400 Čerenkov p.e./mev, ~ lower energy enabling lower threshold energy threshold Linear alkylbenzene!linear alkylebenzene (LAB) (LAB) High light yield Long attenuation length Safe: high flash point and low toxicity!2g/l PPO fluor shifts the wavelength of the emitted light into More affordable detectable than region other scintillators Add wavelength shifter!detector to be filled with 780 tonnes of organic liquid - High light yield - Long attenuation length - Safe: high flash point and low toxicity - Cheaper than other scintillators Initial plan: 2g/L PPO fluor 27 4

5 SNO+ PHYSICS GOALS Neutrinoless double beta decay scintillator loaded with 130 Te (0.3% loading 800 kg of 130 Te) Geo- and Reactor neutrinos Supernova neutrinos Solar neutrinos (pep, CNO, low 8 B) Nucleon decay, sterile neutrinos Multi-purpose detector 5

6 NEUTRINOLESS DOUBLE BETA DECAY Loading the scintillator with isotope Can compare with and without source in the same detector Can in principle investigate several isotopes with the same detector What is the best isotope? Originally decided on 150 Nd due to it s high Q-value and phase space (away from many backgrounds), were hoping for possibility to enrich In principle SNO+ can measure different isotopes (source in/out) 6

7 DOUBLE BETA ISOTOPES 35 known isotopes Decay candidate Q- value (MeV) 48 Ca 48 Ti % natural abundance 76 Ge 76 Se Ca 82 Kr Zr 96 Mo Mo 100 Ru Pd 110 Cd Cd 116 Sn Sn 124 Te Te 130 Xe Xe 136 Ba Nd 150 Sm

8 SNO+ WITH TELLURIUM Fall 2011: Biller and Chen initiate new investigation by subgroup of collaboration Early 2012: new loading techniques for Te in liquid scintillator was developed by Yeh at al. Detailed studies of purification, optics properties, backgrounds by the collaboration followed Also independent review and verification studies were completed March 2013 collaboration decides to focus on 130 Te as the double beta isotope to pursue 8

9 ADVANTAGES OF TELLURIUM 34% natural abundance 2νββ rate is low no inherent optical absorption lines High values of loading feasible (default 0.3%) Internal U/Th background can be actively suppressed by identifying 214 Bi- 214 Po alphas 9

10 LOADING SCINTILLATOR (BNL) Conventional Loading Method Carboxylate Organometallic Complex New loading technique (BNL): Dissolve telluric acid in water and add a few percent of this mixture to LAB using a surfactant. Clear and stable has been demonstrated for more than 1 year. ICP-MS determined U/Th content of telluric acid to be 2-3 times g/g U/Th purification factors of >400 in a single pass have been achieved. 10

11 PERCENT LOADING OF TELLURIUM 0.3%, 0.5%, 1%, 3%, 5% (from left to right)

12 SNO+ EXPECTED SPECTRUM Expected sensitivity is below 100 mev for 0.3% loading (800 kg) 2 years lifetime and fiducial volume cut at 3.5 m (20%) > 99.99% efficient 214 Bi tag, 97% efficient internal 208Tl tag Factor 50 reduction 212BiPo and negligible cosmogenic isotopes m 0ν2β = 200 mev assumed for this plot 12

13 SNO+ PROJECTED SENSITIVITY 13

14 SOLAR NEUTRINOS: PEP pep solar neutrino component is favorable: - single energy (1.442 MeV) and well predicted flux (1.1%) Probes the vacuum-matter transition region Can be measured during pure liquid scintillator phase Probability vs. Energy Simulated spectrum CNO pep 8 B 14

15 CONSTRUCTION STATUS Hold-down system completed, Hold-up ropes exchanged Water fill of cavity started Cleaning the inner surface of AV completed Scintillator purification plant coming together STF completed, testing upcoming PMT repairs ongoing Calibration hardware starting to be installed Detector electronics commissioning air filled running New covergas system installed and commissioned Fiber system and camera system partially installed 15

16 HOLD-DOWN SYSTEM Feb. 2011: Install tarp Cleanliness protection May 2011: drill holes Pre-tensioning Jan 2013 Jan 2012 Install rope net May 2013: Set positions for AV and hold-down sys. Jan 2012: Replace hold-up ropes Sep 2013 Shorten hold-up ropes Completed! 16

17 JANUARY 2012 AND SEPTEMBER 2013 Jan 2012: Replace hold-up ropes Sep 2013 Shorten hold-up ropes

18 AV CLEANING COMPLETE! Suspended platform Carousel and access Cleaning ladder Cleaning entire Inner surface: Jan-Mar 2013 Inside AV, looking down Outside AV 18

19 CAVITY WITH WATER 19

20 Large column SCINTILLATOR PLANT All vessels, kettles, etc. underground and installation ongoing He-leak checking of components mostly completed Slung, arriving UG 2h fire walls Piping to do Fire protection and suppression to be completed 20

21 DETECTOR Upgrade electronics, bring everything online Repair PMTs ~300 so far DAQ tests, LED system tests, air-filled running Install UI and acrylic pipes May 2013 Getting ready for running with water

22 SNO+ DARK RUNNING DECEMBER 2013 AND FEBRUARY 2014 With about 200 PMTs under water, turned on complete detector with HV and ran for 8 days Training detector experts and commissioning system components Weekend and night shifts operated from surface Took full set of PMT calibration data: electronics and timing Data to test PMT calibration code Testing new monitoring tools

23 WATER LEVEL ABOVE PMTS

24 WATER LINE DECEMBER (out of 19) crates with HV, rates for PMTs Under water higher (as expected)

25 USING INSTALLED FIBERS FEBRUARY 2014 Timing calibration data Testing system Stress test for DAQ Optical calibration without need to Insert source into the detector, Minimize contamination risk. Water level 12 ft from cavity floor

26 FIBER DATA 11.2 million events total for timing calibration

27 MUON

28 NEW COVER GAS SYSTEM WAS INSTALLED AND TESTED

29 Cover Gas Pictures

30 SUMMARY AND OUTLOOK Water fill has begun, plan to be filled by the end of the year Remaining PSUP installations (fibers, cameras, etc.) Water phase data taking (2014) Fill with scintillator start background studies Introduction of isotope in stages: 2015 Exciting times ahead 30

31 Queen s University Laurentian University University of Alberta TRIUMF SNOLAB University of Pennsylvania University of Chicago University of Washington Armstrong Atlantic University University of North Carolina UC Berkeley and LBNL UC Davis Oxford University Sussex University Liverpool University Queen Mary University Lancaster University LIP Lisboa and Coimbra Technical University of Dresden YESTERDAY S COLLABORATION PHOTO August 2013 Collaboration meeting 31

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33 BACKUP SLIDES

34 OPTICAL PROPERTIES Absorption vs. wavelength Triggers vs. Total Charge Te does not have absorption lines Optically clear Wavelength shifter options under investigation to further improve Average light level hits/mev 34

35 BACKGROUNDS target level ~2.5x10-15g U /g cocktail ~3x10-16g Th /g cocktail Several α and βemissions Direct backgrounds 212 Bi- 212 Po w coinc. 98% rejection 214 Bi- 214 Po w coinc. 99.8% rejection 214 Bi- 214 Po iw coinc. 98% rejection 212 Bi- 208 Tl coinc. 97% rejection Continue to investigate, improve 214 Po 164.3μs Q-value: 3.27 MeV External backgrounds from AV, rope net, PMTs, water shield Attenuated by fiducial volume, 50%time likelihood cut 212 Po 3x10-7 s Q-value: 2.25 MeV 35

36 SOLAR NEUTRINOS: CNO 36

37 SOLAR NEUTRINOS Background studies in pure scintillator will be available years before to determine strategy to achieve background goals Radon daughters have accumulated on the surface of the AV over the last few years in a significant way. If these leach into the scintillator, the purification system has the capability to remove them. However, depending on the actual leach rate, that removal might be inefficient and the 210 Bi levels in the scintillator too high for a pep/cno solar neutrino measurement without further mitigation. Mitigation should include enhancing online scintillator purification, draining the detector and sanding the AV surface to remove radon daughters, or deploying a bag Double beta decay and low energy 8 B solar neutrino measurements are not effected by these backgrounds. 37

38 GEO- AND REACTOR NEUTRINOS 38

39 NUCLEON DECAY AND SN NEUTRINOS Water phase will allow to look for invisible nucleon decay modes by observation of characteristic gammas. SN neutrinos for a SN within our galaxy. See presentation by Belina Von Krosigk on Sunday Interesting physics by combining with results from HALO (a dedicated SN detector at SNOLAB) CC and NC combinations 39

40 COSMOGENICS Short and long living isotopes can be produced by cosmogenic activation of Tellurium detailed studies by V. Lozza Isotopes with value larger than 2 MeV and with half-life longer than 20 days have been considered as potential backgrounds. Productions rates were estimated using the program ACTIVIA and the neutron and proton flux parameterization a sea level from Armstrong and Gehrels. Low energy rand (E<200 MeV) used TENDL database for cross sections where available Purification factors needed have been determined based on exposure of one year at sea level. Purification at surface will be able to reduce induced cosmogenics by a factor larger than Further purification underground and cooling times on the order of month for isotopes produced during transport will also be needed. With these measures, cosmogenic isotopes are a negligible background contribution 40