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HALO - a Helium and Lead Observatory

HALO - a Helium and Lead Observatory. Outline Overview Motivation / Physics SNEWS Signal and Backgrounds Monte Carlo studies Further Work. Use materials on hand 80 tonnes of Pb from decommissioned Chalk River Cosmic-ray station 3 He proportional counter neutron detectors To produce a

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HALO - a Helium and Lead Observatory

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  1. HALO - a Helium and Lead Observatory Outline • Overview • Motivation / Physics • SNEWS • Signal and Backgrounds • Monte Carlo studies • Further Work

  2. Use materials on hand 80 tonnes of Pb from decommissioned Chalk River Cosmic-ray station 3He proportional counter neutron detectors To produce a Low cost Low maintenance Low impact in terms of lab resources Long-term Supernova detector Overview

  3. Motivation / Physics Galactic supernova are rare / little known Unique opportunity SNEWS Lead; high v x-sect., low n cap. x-sect.

  4. Neutrinos from supernovae • Neutrinos leaving star are expected to be in a Fermi-Dirac distribution according to escape depth: • Oscillations redistribute neutrino temperatures • SK, Kamland are primarily sensitive to νe • HALO’s sensitivity to νe and NC valuable

  5. NCD Energy Spectrum Energy spectrum from one NCD string with an AmBe neutron source. 764-keV peak 191-keV shoulder from proton going into the wall

  6. Energy vs Duration

  7. Inter- experiment collaboration to disseminate the news of a galactic SN Coincidence between detectors required in 10 second window SNEWS is “live” – a “GOLD” coincidence would be sent to subscribers > 250 subscribers to e-mail distribution list > 2000 amateur subscribers through Sky & Telescope GCN (Gamma-ray burst Coordinates Network) Amanda joined recently; Kamland soon HALO could bridge a gap between SNO and SNO+ SNEWS – Supernova Early Warning System

  8. Signal In 80 tons of lead for a SN @ 10kpc†, Assuming LMA, FD distribution around T=8 MeV for νμs, ντs. 68 neutrons through νe charged current channels 30 single neutrons 19 double neutrons (38 total) 21 neutrons through νx neutral current channels 9 single neutrons 6 double neutrons (12 total) ~89 neutrons liberated †- Engel, McLaughlin, Volpe, Phys. Rev. D 67, 013005 (2003)

  9. Backgrounds Norite (α,n) neutrons 0.1(ε) Hz Internal alphas in n-region 3.5x10-4 Hz*Length/200m Cosmic ray neutrons 1.3x10-5(ε) Hz Multi-neutron bursts thermalize in ~200μs Gamma Backgrounds < 1x10-5 Hz

  10. Monte Carlo Studies - GEANT Phase 1 Work – 80 Tonne detector Use lead in its current geometry Start with single NCD per column of lead (though ~300m available) 88 kg / block 865 blocks 8 kg /cm 3He

  11. Monte Carlo Studies Optimize for capture efficiency as function of moderator thickness 42% capture efficiency for 6mm polyethylene moderator Done in a fiducial volume to avoid confusion from edge-effects and to understand maximum efficiency.

  12. Monte Carlo Studies However, volume-averaged efficiency falls to 17.5% (60% loss relative to “fiducial volume” one) • Add reflector • 20 cm water adequate • recover to 25% capture efficiency (volume averaged); 40% loss

  13. Monte Carlo Studies – phase 1

  14. Monte Carlo Studies – phase 2 Optimize for full 700m of 3He counters Allow modification of block geometry if advantageous Define footprint

  15. Monte Carlo Studies ** - naïve scaling – not MC

  16. Monte Carlo Studies • Phase 2 Interpretation - More is better; but what is optimum? • # of 2n events detected varies mass * capture efficiency 2 • Optimizing on m*ε2 with fiducial volume efficiency suggests optimum • near 1.5kT, but • - insufficient points done • - using volume averaged efficiency will reduce the optimum • mass, suspect closer to 1kT • - needs further MC work to define • Good news • – 1 kT of Pb occupies a cube only 4.5 m on a side • - great quality Pb (Doe Run) ~1.5M USD / kT, but this quality is not required

  17. Further Work Continue with refinement of MC work SN modeling Pb cross-sections Neutron energy distributions Modeling of backgrounds design of phase 2 detector Engineering work for phase 1 installation Ready for installation as space becomes available

  18. 3x3x3m cube for optimum efficiency Other configurations are possible Hallway would be optimum for future expansions Overhead crane for setup and movement UPS power and remote access for 100% livetime Earliest possible start date SNOLAB Requirements

  19. Draft Budget Thanks to Charles Duba for this and Slides from his Presentation at SNOLAB Workshop III

  20. University of Washington Peter Doe, Charles Duba, Joe Formaggio, Hamish Robertson, John Wilkerson Laurentian University Jacques Farine, Clarence Virtue, Fabrice Fleurot, Doug Hallman Los Alamos National Laboratory Jaret Heise, Andrew Hime Lawrence Berkeley National Laboratory Kevin Lesko Carleton University Cliff Hargrove, David Sinclair Queen’s University Fraser Duncan, Tony Noble Duke University Kate Scholberg University of Minnesota Duluth Alec Habig Collaboration Members as of 8/05

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