Transcript HALO - a Helium and Lead Observatory Outline

HALO
- a Helium and Lead Observatory
Outline
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Overview
Motivation / Physics
SNEWS
Signal and Backgrounds
Monte Carlo studies
Further Work
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
Overview – an opportunity
• 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
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
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.
SNOLAB Workshop V, Sudbury, 21-23 August 2006
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 V, Sudbury, 21-23 August 2006
C.J. Virtue
SNEWS – Supernova
Early Warning System
• 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+
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
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.
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
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
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
SN neutrino signal in HALO – Phase 1
• 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
†- Engel, McLaughlin, Volpe, Phys. Rev. D 67, 013005 (2003)
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
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
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
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.
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
Monte Carlo Studies – Phase 1
However, with only 80 T the volumeaveraged 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
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
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
SNOLAB Workshop V, Sudbury, 21-23 August 2006
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 m
2.7 kg/cm
41%
36
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
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.
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
Phase 2 Monte Carlo Studies
• 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
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
Monte Carlo Studies
Tonnes of Pb
Neutron
Capture
Efficiency
(fid. volume)
Detected
Neutrons
(SN @ 10kpc)
(Phase 1)
Detected
Neutrons **
(SN @ 10kpc)
(Phase 2)
1000
55%
---
432
8 kg/cm
560
60%
(cf. 42% phase 1)
22/80 T
238
4 kg/cm
280
79%
31/80 T
131
2.7 kg/cm
189
83%
36/80 T
83
Pb / 3He ratio
(700 m NCDs
- Phase 2)
14 kg/cm
** - preliminary
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
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 …
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
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
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
SNOLAB Requirements – Phase 1
• 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 Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue
Draft Budget – Phase 1
Capital costs 05-06 $CDN
Unit cost
Move 80 tonnes Pb to 6800
Etch surface
Move to final location
Schedule 80 PP moderator tubing
Steel platform
Framework for detector/reflector
Water boxes
Side panels
Unit
Qty
20
m
90
3
100
box
ea
400
5
Mechanical SubTotal
RF caps
Preamp connector and SHV
HV power supplies
LV power supplies
Rack
VME crate
Bit3
Shaper/ADCs
Preamps
Cables
Computer
Fiber Optic LAN
Total
18,000
5,000
1,000
1800
2000
3000
1200
500
32,500
10
ea
30
ea
700
ea
500
ea
500
ea
3000
ea
3500
ea
2000 8-ch card
100
ea
1 batch
5000
ea
3000
ea
Electronics Subtotal
Labor
Travel
Subtotal
Contingency
0.2
TOTAL
SNOLAB Workshop V, Sudbury, 21-23 August 2006
50
50
4
4
1
2
2
12
100
5000
2
2
500
1500
2800
2000
500
6000
7000
24000
10000
5000
10000
6000
75300
50000
20000
177,800
35560
213,360
Thanks to Charles
Duba for this and
other slides from his
presentation at
SNOLAB Workshop III
C.J. Virtue
Collaboration “Members” as of 8/05
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
SNOLAB Workshop V, Sudbury, 21-23 August 2006
C.J. Virtue