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