1. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 High Altitude Water Cherenkov experiment  HAWC Andrew Smith, University of Maryland

2. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Detector Layout Milagro: 450 PMT (25x18) shallow (1.4m) layer 273 PMT (19x13) deep (5.5m) layer 175 PMT outriggers Instrumented Area: ~40,000m 2 PMT spacing: 2.8m Shallow Area:3500m 2 Deep Area:2200m 2 HAWC: 900 PMTs (30x30) 5.0m spacing Single layer with 4m depth Instrumented Area: 22,500m 2 PMT spacing: 5.0m Shallow Area:22,500m 2 Deep Area:22,500m 2 HAWCMilagro

3. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Detector Layout Milagro: 2 layers at depths 1.4m – “Air Shower” Layer 5.5m – “Muon” Layer HAWC: Single intermediate layer Opaque curtains between cells 4m 5.5 m 5 m 2.8 m 1.4 m

4. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Curtains HAWC single muon rate = ~1MHz Install curtains to optically isolate the PMTs. Intrinsic Gamma hadron separation

5. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 4300m 2600m Difference between 2600m (Milagro) and 4300m: ~ 6x number of particles ~ 2-3x lower energy threshold Altitude

6. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Milagro Instrumentation 900 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 TDC’s –Capable of ~2000Hz or 6MB/s readout VME-FastBus interface for readout

7. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Gamma/Hadron Separation Lateral distribution of EM energy and muons. Particle Density (Arbitrary Units)

8. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Triggering with Curtains Multiplicity trigger at ~80 PMTs gives same trigger rate as Milagro at 50 PMTs Much higher Gamma area. Milagro HAWC Gamma-Ray Rate

9. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006  = ~0.4 deg  = ~0.25 deg Angular Resolution nTrigger = 50PMTs nTrigger = 200 PMTs

10. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Gamma/Hadron Separation Gammas Protons 30 GeV70 GeV230 GeV 20 GeV70 GeV 270 GeV Size of HAWC Size of Milagro deep layer Energy Distribution at ground level

11. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Gamma/Hadron Separation “Compactness” Use new  /hadron discrimination variable for HAW that excludes the core location. C Milagro = (nPMTs > 2 PE) (Max “muon layer” hit) C HAWC = (nPMTs > 2 PE) (Max “muon layer” hit >30m from core)

12. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006  / hadron Separation Cut: nTop/cxPE>5.0 Eff  = 34% Eff CR= 3% Cut: nTop/cxPE>5.0 Eff  = 56% Eff CR= 1.5% Q Factor (sig/√bg) Cuts soft hard HAWC 2.0 4.5 HESS 3.2 4.4   = 56% -> 28%  CR = 3% -> 0.4% (shape only) HESS

13. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Effective Area Gamma Area:  5.0  <1.0 O 200 PMT Trigger 80 PMT Trigger 20 PMT Trigger Area of GLAST Detector Size

14. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Energy (Crab Spectrum, nTop/cxPE>5.0.,  <30 O ) Significance from Crab Transit (~5 hr) 4  Crab signif/year ~80  5  point source sensitivity reach ~60mCrab of 1 year survey Energy Resolution ~30% above median Angular Resolution0.25 O -0.40 O S/B (hard cuts) ~ 1:1 for Crab Typical day 20 excess on 25 bkg Q (sig/√bg) ( miniHAWC/Milagro) = 15 HAWC Sensitivity

15. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Sensitivity Increase (Q factor) 15x Sensitivity increase over Milagro ~3x from Altitude, Area ~3x from  /hadron separation ~1.5x from Angular resolution ~60mCrab sensitivity (5  in 1year)

16. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 GRB Sensitivity Fluence Sensitivity to 100s GRB. Both Milagro and HAWC can “self trigger” and generate alerts in real time. GRB rate in FOV ~100 GRB/year (BATSE rate) Milagro HAWC

17. Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 The Diffuse Galactic Plane Use Neutral H map to trace out VHE Gamma-Ray flux. Normalize to Milagro observed TeV diffuse emission from the Galactic plane. HAWC Diffuse Galaxy in 1 year Galactic Neutral Hydrogen

18. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Pond Design Fiducial volume: 150m x 150m x 4m Actual size: 170m x 170m x 5m 1:1 slope at perimeter 4½m depth to allow for 4m over PMTs. Total volume: 115 Ml 170m 150m 4.5-5.0 m 6m

19. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Building Construction Prefabricated steel building –Components manufactured at factory. –Shipped to site (~9 trucks) –Beams bolted not welded. –Cost ~1.5M$ (not installed) Building installation ~400 k$ Pond excavation ~300 k$ Liner cost ~600 k$ Total facility cost ~3.0-3.5M$ 170m

20. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Sierra Negra, Mexico ~1 ½ hr drive from Puebla ~4hr drive from Mexico City Saddle between Sierra Negra (z=4500m) and Orizaba (z=5600m) Site under development as a multiuse scientific facility.

21. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Sierra Negra, Mexico Water available from wells in valley and may be available at the site.

22. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Sierra Negra, Mexico Elevation = 4030m Latitude = 19 O 00’N Longitude = 97 O 17’ W LMT – 50m dish

23. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 YBJ Laboratory – Tibet, China Elevation: 4300m Latitude: 30 O 13’ N Longitude: 90 O 28’ E Lots of space. Available power. Available water. Tibet Air Shower Array

24. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Geomagnetic Cutoff Milagro:3.5 GV Tibet- 13.1 GV La Paz: 12.0 GV Sierra Negra: 7.7 GV Singles rates at sites under consideration are reduced by ~20-30% due to improved geomagnetic cutoff.

25. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 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.

26. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 DAQ Upgrade Move to VME TDC bases DAQ. CAEN 1190 Capable of >40MB/s 10-20kHz Readout. Cost ~100k$

27. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Costs Facility ~$3.5M –Excavation, Liner, Building, Roads etc. Water Recirculation System ~$100k Cabling DAQ Upgrade ~$200k Other costs: ~$600k –Computing, Archiving, Monitoring, Cooling, Shipping… Getting the Water (site dependent) Electrical (site dependent) Communications (site dependent) Price ~$200/m 2

28. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Detector Sensitivity (Single Location) HAWC HAWC II GLAST EGRET Crab Nebula Whipple VERITAS/HESS Current synoptic instruments

29. HAWC Andrew Smith - University of Maryland TeV Astrophysics II, August 28,2006 Conclusion Surface arrays complement IACTs –Variable Sources –Diffuse Sources –GLAST/IceCube Coincidence –High Energy Sensitivity computations don’t include weighting techniques used by Milagro. –Expect >~x2 sensitivity increase (or more). Harder spectra favor high energy instruments. –For an  =-2.0 source that extends to >~10TeV 30 mCrab HESS(180GeV) source = 300 mCrab Milagro(10 TeV w/Weighted Analysis) –Milagro would detect hard HESS GP sources if it was in the Southern Hemisphere. –HAWC sensitivity is an order of magnitude lower.