1 / 36

Future geoneutrino detectors: SNO+, EARTH, Baksan, and Homestake

Future geoneutrino detectors: SNO+, EARTH, Baksan, and Homestake. Nikolai Tolich University of Washington. Current status. KamLAND demonstrated method. Current purification will significantly reduced 13 C(  ,n) backgrounds.

azia
Download Presentation

Future geoneutrino detectors: SNO+, EARTH, Baksan, and Homestake

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Future geoneutrino detectors: SNO+, EARTH, Baksan, and Homestake Nikolai Tolich University of Washington

  2. Current status • KamLAND demonstrated method. • Current purification will significantly reduced 13C(,n) backgrounds. • Preliminary results with 4 times the statistics gives ~36% measurement, sensitivity will always be limited by reactor background. • Borexino has recently started collecting data, but small size may limit precision of result. Candidates 152 events Expected reactor 80.4 ± 7.2 Expected (,n) 42 ± 11

  3. Statistics • Currently we are statistics limited. • Our largest non-earth model systematic is ~9% due to neutrino oscillations. • To maximally constrain earth models with a single detector we should make a ~9% measurement of the geoneutrino flux. • With no backgrounds this requires an exposure of 21032 proton years or ~2-3 year measurement with a KamLAND sized detector. • The time approximately scales with background.

  4. More detectors • KamLAND’s location is not ideal since the geology of Japan complicates the contribution from the crust. • Ideally we would like to make a measurement in the ocean to probe the contribution from the mantle. • The heat flow in the lower and middle crust is not very well constrained and multiple measurements on different types of continental crust would also be extremely useful. • Ultimately a detector that could measure neutrino directions could provide a detailed map of the U and Th distributions in the Earth.

  5. 111 93 75 56 37 21 3 Future detectors EARTH ?? kton Homestake 1-?? kton LENA 50 kton Baksan 5 kton KamLAND 1 kton SNO+ 1 kton Borexino 0.3 kton Hano hano 10 kton • www.fe.infn.it/~fiorenti

  6. Studies of geoneutrinos and supernovae with a large scintillation detector at Baksan Neutrino Observatory G. Domogatsky, Institute for Nuclear Researches Russian Academy of Science V. Kopeikin, L. Mikaelyan, V. Sinev RRC Kurchatov Institute

  7. Baksan detector summary • Borexino or KamLAND type detector of mass 5 kt (or 5x1032 protons) • 4800 mwe overburden. • Background from power plants: 350 events/year (w/o oscillations) • Expected rates: • Geoneutrinos (U+Th) 450 events/year (according Fiorentini) • Georeactor 150-550 events/year (w/o oscillations) • SN at 10 kpc 1150-1500 IBD events/flash • We propose using a 1 MCi movable 90Sr-90Y source of antineutrinos for detector calibration resulting in 30000 antineutrino events/year • References: • Georeactor: Phys. Atom. Nucl. 68, 69 (2005), arXiv:hep-ph/0401221 • Geoneutrinos: Phys. Atom. Nucl. 69, 1894 (2006), arXiv:hep-ph/0409069 and arXiv:hep-ph/0411163 • Supernovae: Phys. Atom. Nucl. 70, 1081 (2007), arXiv:0705.1893

  8. A geoneutrino detector at Homestake N. Tolich University of Washington Y.-D. Chan, B. K. Fujikawa, K.T. Lesko, A.W.P. Poon, J. Wang Lawrence Berkeley National Lab.

  9. Homestake detector summary • Homestake was recently chosen as the preferred site for a national underground laboratory in the US. • Background from power plants is 11 per 1032 target proton yr (below 3.4MeV) • Expected U+Th geoneutrino rate is 64 per 1032 target proton yr (Montavani) • Expected signal from a 6TW georeactor is 40 per 1032 target proton yr • To observe a 6TW reactor at the Earth’s core at 3 would require exposure of 0.81032 proton years. • Sensitive to georeactor power down to ~1TW. U geoneutrinos Th geoneutrinos 6TW georeactor Commercial reactors

  10. EARTH • Finland: • University of Jyväskylä (Wladek Trzaska) • Netherlands: • ASTRON (Lars Venema, Rik ter Horst, Ramon Navarro) • Univ. Groningen (Heinrich Wörtche) • EARTH (Jacob Dekker, Reinhard Morgenstern, Henk Koopmans, Rob de Meijer) • Slovenia: • Jozef Stefan Institute (Matjaz Vencelj) • South Africa: • University of Cape Town (Frank Brooks, Rudolph Nchodu) • University of the Western Cape (Robbie Lindsay, David le Roux, Rob de Meijer) • University of Stellenbosch (Greg Hillhouse, Shaun Weingaart) • iThemba LABS (Ricky Smit, Zinhle Buthelesi, Richard Newman, Krish Baruth Ram)

  11. Detector concept • Addition of 10B reduces the neutron random walk, and better preserves the direction information carried by the neutron. • Direction sensitivity requires detector units with a high spatial resolution (1-2cm) for e+ and n. • Leads to a detector comprising of many modules, each containing many detector units.

  12. Development strategy • Use existing, proven technologies and demonstrate the Proof Of Principle (POP) of direction sensitive antineutrino detection near a nuclear power plant. • Develop in parallel new technologies for light detection, detection materials, signal analysis and processing, data storage. Only after sufficient testing incorporate them in the detector set ups. • Scale-up detector dimensions step by step. (Started very small, next step is still small but afterwards we intend to reach our goal in one or two steps of development) • Apply new technologies if appropriate. • During development, look for applications (financing).

  13. Successful first phase Double Pulses • Use existing small (3.8x2.5cm) detectors. • Simulate double pulse events with n-source. • Determine time characteristics of coincidences and pulse shape. Pulse shape (tail) is particle dependent. Important for background suppression.

  14. Delayed coincidences • Double pulse well detectable; there is a difference in shape between n and g. • Addition of 10B leads to a much shorter capture time and hence reduces background (accidental coincidences). • Ready for the next steps with “real” antineutrinos. 400ns mean capture time N0=116; T0=400ns

  15. Design Intermediate Detector GiZA(Geoneutrinos in ZA) • Positron and neutron-capture event positions are determined by triangulation using the four detector signals. • Antineutrino direction determined from neutron-capture position offset Muon-shield g + n shield

  16. Background suppression • Delayed coincidences (~106); • Position requirements (~10); • Pulse shape (~101-2); • Constant magnitude a-pulse (~101-2); • (Anti-)coincidences (~102-3); • Overall expected suppression factor: 1010-1014

  17. Goals for the next phase • Measure real antineutrino signature with Giza and tubular detectors; • Check triangulation possibilities; • Investigate pulse characteristics and light attenuation gelled detectors; • Investigate background reduction in underground laboratories (Gran Sasso, Italy, and Pyhäsalmi Finland); • Design prototype reactor monitor. Future scenario ?

  18. EARTH summary • For direction sensitivity a completely different detector concept is needed. Modular instead of monolithic. • A number of problems of the monolithic detectors (background) disappear, new challenges (read-out of many detectors) come in return. • Design phase: Computer simulations to determine the dimensions of the detector units and to optimize neutron detection. • Direction-sensitive detection is a prerequisite. EARTH is the first program addressing this issue. • Direction-sensitive antineutrino detection is physics-wise possible and seems feasible with the state of the art technologies on a small scale.

  19. SNO 1000 tonnes D2O 12 m diameter acrylic vessel 18 m diameter support structure; 9500 PMTs (~60% photocathode coverage) 1700 tonnes inner shielding H2O 5300 tonnes outer shielding H2O Urylon liner radon seal depth: 2092 m (~6010 m.w.e.) ~70 muons/day

  20. SNO+ • Plan to fill the SNO detector with a liquid scintillator in 2009-2010 • Linear alkylbenzene (LAB) • compatible with acrylic undiluted • high light yield, long attenuation length • safe: high flash point, low toxicity • low cost! • Physics goals: pep and CNO solar neutrinos, geoneutrinos, reactor neutrino oscillations, supernova neutrinos, double beta decay with Nd

  21. Queen’s University M. Boulay, M. Chen, X. Dai, E. Guillian, P. Harvey, C. Kraus, C. Lan, A. McDonald, V. Novikov, S. Quirk, P. Skensved, A. Wright University of Alberta A. Hallin, C. Krauss Carleton University K. Graham Laurentian University D. Hallman, C. Virtue SNOLAB B. Cleveland, F. Duncan, R. Ford, N. Gagnon, J. Heise, C. Jillings, I. Lawson Brookhaven National Laboratory R. Hahn, M. Yeh, Y. Williamson Idaho State University K. Keeter, J. Popp, E. Tatar University of Pennsylvania G. Beier, H. Deng, B. Heintzelman, J. Secrest University of Texas at Austin J. Klein University of Washington N. Tolich, J. Wilkerson University of Sussex K. Zuber LIP Lisbon S. Andringa, N. Barros, J. Maneira SNO+ collaboration new collaborators are welcome!

  22. Geoneutrino signal KamLAND: 33 geoneutrino and 142 reactor events per year (1000 tons CH2) SNO+: 44 geoneutrino and 38 reactor events per year (1000 tons CH2) SNO+ geo-neutrinos and reactor background KamLAND geo-neutrino detection July 28, 2005 in Nature Old, stable, thick continental crust surrounds Sudbury

  23. Double beta decay • Plan to add an isotope which undergoes double beta decay to the liquid scintillator • 150Nd selected: • High endpoint: 3.37 MeV (Above most backgrounds) • Isotopic abundance: 5.6% • A liquid scintillator detector has poor energy resolution; but enormous quantities of isotope (high statistics) and low backgrounds help compensate • Large, homogeneous liquid detector leads to well-defined background model • fewer types of material near fiducial volume • meters of self-shielding • Possibly source in–source out capability

  24. Nd scintillator light output • 1% Nd-loaded scintillator is blue because Nd absorbs light. • Fortunately it is blue, it means the blue scintillation light can propagate through. • Monte Carlo predicts 47±6 pe/MeV light output in SNO+ if using 1% Nd loading. • Monte Carlo predicts 400±21 pe/MeV light output in SNO+ at 0.1% loading: good enough to do the experiment • With enriched Nd (e.g. enrich to 56% 150Nd up from 5.6%) could have the same neutrinoless double beta decay sensitivity using 0.1% Nd loading.

  25. 150Nd consortium • SuperNEMO and SNO+ are supporting efforts to maintain an existing French AVLIS facility (Menphis) that is capable of making 100’s of kg of enriched Nd • Menphis facility • 1st full scale exp. 2003 • Enriched 204 kg of U (from 0.7% to 2.5%) in several hundred hours

  26. Sensitivity • For 50% enriched 150Nd (0.1% Nd LS in SNO+) 3s statistical sensitivity reaches 30 meV • assuming background levels (U, Th) in the Nd LS similar to KamLAND • Systematic error in energy response will likely be the limit of the experiment and not the statistics • Preliminary studies show that we can understand the energy resolution systematics at the level required to preserve sensitivity down to 50 meV Test <m> = 150 meV Klapdor-Kleingrothaus et al., Phys. Lett. B 586, 198, (2004) simulation: one year of data

  27. Steps required • Acrylic vessel hold down • Liquid scintillator procurement • Scintillator purification • “minor” upgrades • cover gas • electronics • DAQ • calibration

  28. SNO+ hold down net sketch of hold-down net Acrylic vessel hold down ropes Existing acrylic vessel support ropes rope tension calculation as input for finite element analysis

  29. SNO+ summary • Good double beta decay sensitivity and very timely • Well defined background model, large volume gives self-shielding • Q-value is above most backgrounds, thus “insensitive” to • internal radon backgrounds • external backgrounds (2.6 MeV ) • Th, Ra purification techniques are effective • Submission of full capital proposals 2008 • Ready for scintillator 2010 • Will likely be the next operational geoneutrino experiment • Reactor signal ~1/4 KamLAND’s • Well defined old continental crust

  30. Conclusions • We can learn a lot with more geoneutrino experiments, both on the ocean floor and in the continents. • It helps for funding if the experiment has multiple uses. • SNO+ could be operational by 2010. • Homestake and Baksan funding would benefit from useful results from SNO+. They would provide results in different crust, to constrain crust models. • EARTH is being ambitious, and is developing the next generation directional detectors.

  31. Recent developments….. lead to new opportunities: High-position resolution from differences in arrival times (Triangulation)

  32. Solar neutrinos • SNO+ is at 6000 m.w.e. depth • muon flux reduced a factor 800 compared to Kamioka and a factor 100 compared to Gran Sasso • recall KamLAND’s post-purification goal KamLAND and Borexino will try to tag and veto the 11C to suppress at SNO+ depth this background is already smaller than the signal and one can still tag and veto 3600 pep events/(kton·year), for electron recoils >0.8 MeV

  33. Background requirements • Radiopurity requirements • 40K, 210Bi (Rn daughter) are important • 85Kr, 210Po (as seen in KamLAND) not a problem since pep signal is at higher energy than 7Be • U, Th not a problem if one can duplicate KamLAND or Borexino levels of scintillator radiopurity • note: Borexino succeeded to fill with little 210Bi contamination by minimizing radon exposure of the scintillator

  34. Candidate selection

  35. from Elliott and Vogel, hep-ph/0202264 v1 (2002) 0.1 is Staudt, Muto and Klapdor 0.2 is Faessler and Simkovic; Toivanen and Suhonen from Rodin et al., corrected (2007) value is 0.2-0.3 Nd matrix elements

More Related