Halo Properties in Helium Nuclei from the Perspective of ...
HALO - a Helium and Lead Observatory
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Transcript of HALO - a Helium and Lead Observatory
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
HALO - a Helium and Lead
ObservatoryOutline
• Overview• Motivation / Physics• SNEWS• Signal and Backgrounds• Monte Carlo studies• Further Work
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
• 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-termSupernova detector
Overview
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
• Galactic supernova are rare / little known• Unique opportunity• SNEWS• Lead; high v x-sect.,
low n cap. x-sect.
Motivation / Physics
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
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
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
NCD Energy Spectrum
191-keV shoulder from proton going into the wall
764-keV peakEnergy spectrum from one NCD string with an AmBe neutron source.
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
Energy vs Duration
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
• 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
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
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)
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
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
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
Phase 1 Work – 80 Tonne detector– Use lead in its current geometry– Start with single NCD per column of lead
(though ~300m available)
Monte Carlo Studies - GEANT
88 kg / block865 blocks8 kg /cm 3He
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
Optimize for capture efficiency as function of moderator thickness
Monte Carlo Studies
42% capture efficiencyfor 6mm polyethylenemoderator
Done in a fiducial volumeto avoid confusion fromedge-effects and to understand maximumefficiency.
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
However, volume-averaged efficiency falls to 17.5% (60% loss relative to “fiducial volume” one)
Monte Carlo Studies
Add reflector• 20 cm water adequate• recover to 25% capture efficiency (volume averaged); 40% loss
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
Monte Carlo Studies – phase 1
# NCDs per column
Total NCD length
Pb / 3He ratio(80 Tonnes Pb
- Phase 1)
Neutron Capture
Efficiency(vol. aver.)
Detected Neutrons
(SN @ 10kpc)
1 95 m 8 kg/cm 25% 22
2 190 m 4 kg/cm 35% 31
3 285 m2.7
kg/cm41% 36
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
Monte Carlo Studies – phase 2
Optimize for full 700m of3He counters
Allow modification of blockgeometry if advantageous
Define footprint
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
Monte Carlo Studies
Pb / 3He ratio(700 m NCDs
- Phase 2)Tonnes of Pb
Neutron Capture
Efficiency(fid. volume)
Detected Neutrons
(SN @ 10kpc)(phase 1)
Detected Neutrons **
(SN @ 10kpc)(phase 2)
14 kg/cm 1000 55% 216
8 kg/cm 560
60%(cf. 42% - phase
1)
22/80 T 132
4 kg/cm 280 79% 87
2.7 kg/cm
189 83% 62
** - naïve scaling – not MC
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
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
Monte Carlo Studies
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
• 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
Further Work
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
SNOLAB Requirements
• 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 Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
Capital costs 05-06 $CDNUnit cost Unit Qty Total
Move 80 tonnes Pb to 6800 18,000Etch surface 5,000Move to final location 1,000Schedule 80 PP moderator tubing 20 m 90 1800Steel platform 2000Framework for detector/reflector 3000Water boxes 3 box 400 1200Side panels 100 ea 5 500
Mechanical SubTotal 32,500RF caps 10 ea 50 500Preamp connector and SHV 30 ea 50 1500HV power supplies 700 ea 4 2800LV power supplies 500 ea 4 2000Rack 500 ea 1 500VME crate 3000 ea 2 6000Bit3 3500 ea 2 7000Shaper/ADCs 2000 8-ch card 12 24000Preamps 100 ea 100 10000Cables 1 batch 5000 5000Computer 5000 ea 2 10000Fiber Optic LAN 3000 ea 2 6000
Electronics Subtotal 75300Labor 50000Travel 20000Subtotal 177,800Contingency 0.2 35560TOTAL 213,360
Draft Budget
Thanks to CharlesDuba for this and Slides from his Presentation at SNOLAB Workshop III
SNOLAB Workshop IV, Sudbury, 15-17 August 2005 C.J. Virtue
Collaboration Members as of 8/05
University of WashingtonPeter Doe, Charles Duba, Joe Formaggio, Hamish Robertson, John
Wilkerson
Laurentian UniversityJacques Farine, Clarence Virtue, Fabrice Fleurot, Doug Hallman
Los Alamos National LaboratoryJaret Heise, Andrew Hime
Lawrence Berkeley National LaboratoryKevin Lesko
Carleton UniversityCliff Hargrove, David Sinclair
Queen’s UniversityFraser Duncan, Tony Noble
Duke UniversityKate Scholberg
University of Minnesota DuluthAlec Habig