Andrew Smith

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miniHAWC
g
mini- High Altitude Water Cherenkov
experiment

• Andrew Smith
• University of Maryland

2
Lexicon

• Milagro Existing water Cherenkov all-sky
  gamma-ray observatory.
• HAWC A ambitious effort to construct an all-sky
  observatory with point source sensitivity of the
  Whipple 10m.
• miniHAWC Demonstrate HAWC technology at low
  cost with Milagro PMTs and instrumentation, with
  potentially large scientific payoff.

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Detector Layout
HAWC 5625 or 11250 PMTs (75x75x(1 or 2)) Single
layer at 4m depth or 2 layers at Milagro
depths Instrumented Area 90,000m2 PMT spacing
4.0m Shallow Area 90,000m2 Deep Area 90,000m2
miniHAWC 841 PMTs (29x29) 5.0m spacing Single
layer with 4m depth Instrumented Area
22,500m2 PMT spacing 5.0m Shallow
Area 22,500m2 Deep Area 22,500m2
Milagro 450 PMT (25x18) shallow (1.4m)
layer 273 PMT (19x13) deep (5.5m) layer 175 PMT
outriggers Instrumented Area 40,000m2 PMT
spacing 2.8m Shallow Area 3500m2 Deep
Area 2200m2
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Detector Layout
Milagro
1.5 m
Milagro 2 layers at depths 1.5m Air Shower
Layer 5.5m Muon Layer
5.5 m
2.8 m
miniHAWC Single intermediate layer opaque
curtains between cells
miniHAWC
5 m
4m
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Milagro Instrumentation

• 899 8 Hamamatsu PMTs
• Bases, encapsulation
• Single rg59 cable for data and HV.
• Custom front end boards
• Signal shaping and
• threshold detection
• Trigger primitive
• generation
• Pulse height through
• TOT method.
• FastBus TDCs
• Capable of 2000Hz or
• 6MB/s readout
• VME-FastBus interface
• for readout

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Gamma/Hadron Separation
Lateral distribution of EM energy and muons.
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Gamma/Hadron Separation
Size of miniHAWC
Size of Milagro deep layer
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Effective Area
Gamma Area qlt30o nTop/cxPEgt5.0 Dqlt1.0O
200 PMT Trigger 80 PMT Trigger 20 PMT Trigger
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Detector Performance
50 PMT Trigger 200 PMT Trigger
s 0.4 deg
s 0.25 deg
Angular Resolution
g/hadron Separation
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miniHAWC Sensitivity Basic Analysis
Energy (Crab Spectrum, nTop/cxPEgt5., qlt30O)
Significance from Crab Transit (5 hr) 4s
5s point source sensitivity reach
60mCrab of 1 year survey Energy
Resolution 30 above median Angular
Resoultion 0.25O/0.40O
S/B (hard cuts) 11 for Crab Typical day 20
excess on 25 bkg
Q(Milagro ? miniHAWC) 15!
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Point Source Weighting
Std Cuts NFITgt20,Cgt2.5
Hard Cuts NFITgt200,Cgt6.0
Excess 5410, Off 1218288, SB 1225 ?hadron
background 0.1
Excess 60, Off 140, SB 12.3 ?hadron
background 1x10-5
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GRB Sensitivity
Milagro
miniHAWC
Fluence Sensitivity to 100s GRB. Both Milagro
and miniHAWC can self trigger and generate
alerts in real time. GRB rate in FOV 100
GRB/year (BATSE rate)
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Point Source Survey Sensitivity
7 min/fov
4 min/fov
1500 hrs/fov
1500 hrs/fov
Assuming 800 hrs/yr for IACTs
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Pond Design

• Fiducial volume 150m x 150m x 4m
• Actual size 170m x 170m x 5m
• 11 slope at perimeter
• 4½m depth to allow for 4m over PMTs.
• Total volume 115 Ml

170m
6m
4.5-5.0 m
150m
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Building Construction

• Prefabricated steel building
• Components manufactured at factory.
• Shipped to site (9 trucks)
• Beams bolted not welded.
• Cost 1M (not installed)
• Building installation 400 k
• Pond excavation 300 k
• Liner cost 600 k
• Total facility cost 2.5-3.0M

170m
170m
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Sierra Negra, Mexico
1 ½ hr drive from Puebla 4hr drive from
Mexico City Saddle between Sierra Negra
(z4500m) and Orizaba (z5600m) Site under
development as a multiuse scientific facility.
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Sierra Negra, Mexico
Availability of water under investigation. Probabl
y need to pump from wells at 1000m lower
elevation.
(More details from Alberto Carramiñana)
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Sierra Negra, Mexico
LMT 50m dish
Elevation 4030m Latitude 19O 00N Longitude
97O 17 W
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La Paz, Bolivia

• Population 1 Million
• Elevation 3900-2900 meters
• Airport in El Alto
• lt 30 min from downtown
• Elevation 4100 m
• El Alto pop. 0.5 Million

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El Alto viewed from Mt. Chacaltaya
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Potential Sites
Mt. Chacaltaya Cosmic Ray Laboratory

• 4806 meters - 13 meters
• South 16 deg 22.381
• West 68 deg 08.758
• 4443 meters - 10 meter
• South 16 deg 24.837
• West 68 deg 08.979

Grid on Map is 1 km x 1km
Water is plentiful, maybe too much so. Latitude
16O 30 S Longitude 68O 11 W
La Paz
El Alto
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YBJ Laboratory Tibet, China
Elevation 4300m Latitude 30O 13
N Longitude 90O 28 E Lots of space. Available
power. Available water.
Tibet Air Shower Array
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YBJ Laboratory Tibet, China
Also home of ARGO observatory. ARGO utilizes
RPCs for EM particle detection. No Calorimetry.
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Geomagnetic Cutoff
Singles rates at sites under consideration are
reduced by 20-30 due to improved geomagnetic
cutoff.
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Triggering and DAQ

• Milagro DAQ in its current form should be capable
  of triggering to multiplicities as low as 80
  PMTs. (1800 Hz)
• Simulation indicates that we can reconstruct
  gamma-ray events as small as 20 PMTs.
• Potentially huge sensitivity increase to GRBs if
  DAQ can be easily upgraded.

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DAQ Upgrade

• Move to VME TDC bases DAQ.
• CAEN 1190
• Capable of gt40MB/s
• 10-20kHz Readout.
• Cost 100k

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Costs

• Facility 3M
• Excavation, Liner, Building, Roads etc.
• Water Recirculation System 50k
• Cabling DAQ Upgrade 200k
• Other costs 300k?
• Computing, Archiving, Monitoring, Cooling,
  Shipping
• Getting the Water (site dependent)
• Electrical (site dependent)
• Communications (site dependent)

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Conclusion