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

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