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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 (Phase 1) 80 tonnes of Pb from decommissioned Deep River Cosmic-ray station

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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 (Phase 1) 80 tonnes of Pb from decommissioned Deep River Cosmic-ray station 3He proportional counter neutron detectors plus DAQ from SNO; plus possibly 10BF3 counters To produce a Low cost Low maintenance Low impact in terms of lab resources (space) Long-term, high livetime Supernova detector Overview – an opportunity

  3. Motivation / Physics Galactic supernova are rare / little known Unique opportunity for particle physics, astronomers, SN dynamics SNEWS Lead; high  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. 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; “Individual” non-coincident alerts also possible now > 250 subscribers to e-mail distribution list > 2000 amateur subscribers through Sky & Telescope GCN (Gamma-ray burst Coordinates Network) HALO could bridge a gap between SNO and SNO+ SNEWS – Supernova Early Warning System

  6. SNO’s NCD 3He counters Current plan is for NCD removal from SNO in February & March of 2007. Close to 700 m of low background 3He counters would be stored underground until HALO deployment. Space in SNOLAB available early 2008.

  7. 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

  8. In 80 tons of lead for a SN @ 10kpc†, Assuming LMA, FD distribution around T=8 MeV for νμ’s, ντ’s. 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; ie. 1.1 n/T SN neutrino signal in HALO – Phase 1 †- Engel, McLaughlin, Volpe, Phys. Rev. D 67, 013005 (2003)

  9. Monte Carlo Studies - GEANT Phase 1 Work – 80 Tonne detector Use lead in its current geometry Shown with single NCD per column of lead (total of 95 m of counters) 88 kg / block 865 blocks 8 kg /cm 3He

  10. Monte Carlo Studies – Phase 1 Optimize for capture efficiency as function of moderator thickness 42% capture efficiency for 6mm polypropylene moderator Done in a fiducial volume to avoid confusion from edge-effects and to understand maximum efficiency.

  11. Monte Carlo Studies – Phase 1 However, with only 80 T the 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 • reduces external neutron background • from 0.1Hz from thermal flux to 0.002Hz • from ~ Hz to 0.04 Hz for fast flux

  12. Other Backgrounds Internal alphas in n-region 3.5x10-4 Hz*Length/200m Cosmic ray induced neutrons 1.3x10-5(ε) Hz Multi-neutron bursts thermalize in ~200μs Gamma Backgrounds < 1x10-5 Hz ie. small for burst detection, but still a need for more detailed simulation of backgrounds with emphasis on external neutrons

  13. Monte Carlo Studies – Phase 1

  14. Monte Carlo Studies – Phase 2 Optimize for full 700m of 3He counters (and possibly 140 m of 10BF3 counters) Allow for modification of block geometry and for purchase of additional Pb.

  15. Choice of moderator D2O versus polypropylene? Twice the volume required; O($700K) No significant gain in neutron capture efficiency dominated by neutron leakage not competition for neutron capture Stick with plastics! Distribution of moderator various options simulated best efficiency and least material for moderator surrounding 3He counters Phase 2 Monte Carlo Studies

  16. Monte Carlo Studies ** - preliminary

  17. 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 • - needs further MC work to define • Good news • – 1 kT of Pb occupies a cube only 4.5 m on a side; O($1M material) • Detailing costing and design for Phase 2 still to come …

  18. Further Work Continue with refinement of MC work SN modeling; sensitivity of Phase 2 to additional physics update Pb cross-sections, neutron energy distributions Modeling of backgrounds finalize design of Phase 2 detector Engineering work for Phase 1 installation Get ready for installation as space becomes available

  19. 3x3x3m cube for optimum efficiency Other configurations are possible Hallway would be optimum for future expansion Overhead crane for setup and movement UPS power and remote access for 100% livetime Early start date SNOLAB Requirements – Phase 1

  20. Draft Budget – Phase 1 Thanks to Charles Duba for this and other slides from his presentation at SNOLAB Workshop III

  21. 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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