Jamie Holder University of Leeds August 2005

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Status and Performance of the First VERITAS
Telescope
Jamie Holder University of Leeds
August 2005
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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

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Mechanical Performance

• Alt-Az mount
• Slew speed
• 0.3?/sec
• 1.0?/sec modified
• Tracking accuracy
• Still evaluating
• Encoders give lt0.005?
• Source location good

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Optical Performance

• 350 mirror facets
• glass
• aluminium coated on-site
• reflectivity gt90 at 320nm
• PSF
• 0.09? FWHM initially
• 0.06? now

PSF plot (with PMT size)
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Camera

• 499 PMTs
• Photonis XP2970
• 0.15? spacing
• 3.5? FOV
• PMT Gain 2 ? 105
• NSB 100 - 200 MHz
• No light cones yet

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Trigger

• Each channel has programmable CFDs
• CFD output sent to pattern selection trigger
• any 3 adjacent PMTs
• Trigger rate 150Hz

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Data Acquisition

• PMT signals digitized with 500MHz sampling FADCs
• Data rates
• 24 samples/channel
• 13.5 kb/event
• 10 deadtime _at_ 150 Hz
• 4 with zero supression

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Timing

• Define optimum integration gate (10ns)

Poster Exploiting VERITAS Timing Information
Holder et al.
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Results

• Crab Nebula observations
• 3.9 hours ON/OFF
• 19.4 s
• 10 s/hour
• Note
• Engineering data
• Preliminary analysis
• No light cones
• cf Whipple 10m (7s/hour)
• Mkn 421 and Mkn 501 also detected (Poster Cogan
  et al)

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Results

• Local Muon background
• 150 GeV trigger threshold
• 400 GeV analysis threshold
• Need Stereo!

Local Muons
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Kitt Peak Site

• Horseshoe Canyon
• 1800m
• KPNO
• Completed
• Site Clearance
• Power
• Telescope Pads
• Temporary access problems

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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