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Jamie Holder University of Leeds August 2005
Status and Performance of Status and Performance of the First VERITAS Telescopethe First VERITAS Telescope
VERITAS Telescope I
• 12m diameter reflector– Davies-Cotton
F/1.0– 110m2
• 499 PMT Camera
• Steel OSS
• Installed at Mt. Hopkins Basecamp (1275m) in January 2005
Mechanical Performance
• Alt-Az mount
• Slew speed– 0.3/sec– 1.0/sec modified
• Tracking accuracy– Still evaluating– Encoders give <0.005– Source location good
Optical Performance
• 350 mirror facets– glass– aluminium coated on-
site
• reflectivity >90% at 320nm
• PSF– 0.09 FWHM initially– 0.06 now PSF plot (with PMT size)
Camera• 499 PMTs
– Photonis XP2970– 0.15 spacing– 3.5 FOV
• PMT Gain = 2 105
• NSB ~100 - 200 MHz
• No light cones yet Single photoelectron peak
(5 times operating voltage)
Trigger
• Each channel has programmable CFDs
• CFD output sent to pattern selection trigger– any 3 adjacent PMTs
• Trigger rate ~ 150Hz
Data Acquisition
• PMT signals digitized with 500MHz sampling FADCs
• Data rates– 24 samples/channel– 13.5 kb/event– 10% deadtime @ 150 Hz– 4% with zero supression
Timing
• Define optimum integration gate (10ns)
Poster: “Exploiting VERITAS Timing Information” Holder et al.
Results • Crab Nebula observations
– 3.9 hours ON/OFF– 19.4 – 10 /hour
• Note– Engineering data– Preliminary analysis– No light cones– cf Whipple 10m (7/hour)
• Mkn 421 and Mkn 501 also detected (Poster: Cogan et al)
Results
• Local Muon background– ~150 GeV trigger
threshold – ~400 GeV analysis
threshold
• Need Stereo!
Local Muons
Kitt Peak Site
• Horseshoe Canyon– 1800m– KPNO
• Completed– Site Clearance– Power– Telescope Pads
• Temporary access problems
Temporary Site
• 2 Telescopes at Mt. Hopkins Basecamp– 88m baseline
• First light October 2005
• Test – array trigger– array analysis
• 4 telescopes on Kitt Peak October 2006