Probing the HiRes Aperture near eV with a Distant Laser C. Cannon, L. Pedersen, R. Riehle, M. Seman, J. Thomas, S. Thomas, L. Wiencke for the HiRes Collaboration 2003 ICRC HE Aug Tsukuba Japan
Experimental Configuration Laser vs. Air Showers Cross Check Atmospheric Aerosol Optical Depth
35 km HiRes 1 HiRes 2 Terra (Laser)
Terra Site – Vertical Laser laser
Laser Parameters Wavelength355nm Energy2-6mJ (adjustable) Distance34km to HiRes 2 22km to HiRes 1 DirectionFixed - Vertical Polarization Random
Laser Beam – polarization measurements LASER Probe Depolarizer Analyzer Linear Polarization Random Polarization
Vertical Laser Shot Fired from Terra as recorded by HiRes2 34 km distant Laser Energy ~3.5mJ 19km 10km
HiRes 1 HiRes 2 Terra (Laser) Shower ~30 EeV How does the laser compare to a shower?
HiRes 2 HiRes 1 Air Shower
HiRes 2HiRes 1 Air Shower
30 EeV Shower
LaserShower Equivalent 4mJ 6x10 19 eV 6mJ ~10 20 eV
Mean Mean 0.04 Under good to moderately hazy conditions, laser is always visible. Triggering efficiency for 4mJ shots begins to drop about 0.15 VAOD We consider “good weather” VAOD <0.01
Compare vertical aerosol optical depth Terra Laser + HiRes2 detector HiRes2 Steerable Laser + HiRes1 detector
What is Vertical Optical Depth? T = e -VOD T = e -VOD/sinӨ Ө VAOD - Vertical Optical Depth of Aerosol Component
Ө2Ө2 Ө1Ө1 LASERDETECTOR T A2 T M2 T A1 T M1 NLNL N OBS S A + S M Measurement of VAOD Then for
Atmospheric Measurements from Inclined Laser Shots
45º 60º Detector Laser 12.6 km
HiRes 1 detector measuring inclined laser track HiRes2 detector measuring Terra Laser Track
Conclusion Installed a laser to probe the reach of our HE aperture (34 km Distant) Equivalent light production to a shower of ~6x10 19 to eV Detectors have no trouble seeing this laser under good to acceptable viewing conditions. Aerosol optical depth measured by Terra Laser/HiRes2 correlates with that measured by HR2SLS and HiRes1 detector
Extra Slides
Linearity Scaled by 10% !!!
45º 60º Detector Laser 12.6 km
Clouds
Inclined Laser Shots clear hazy
HiRes 1 detector measuring inclined laser track HiRes2 detector measuring Terra Laser Track
3 Comments on Calibration Evidence of a ~10% gain change at HiRes1 Nov 2000 probably a shift in roving flasher calibration Absolute Photometric scale of HiRes 4km vertical laser shots 6/28/ nm – HR1 Erecon/Elaser 0.75 M. Seman Analysis 355nm HR nm HR Need to cross check this with another analysis! Wrong Constants.. We are now twice bitten. 2 months ago: wrong wavelength used for YAG laser (Nevis Stereo Analysis) Yesterday wrong effective molecular scale height (Utah Stereo Analysis)
Clouds Laser found clouds on 25% of nights that the operator called clear HR3VLS Clouds 219 Hours operation w/ stereo Jan-May Hours – laser tracks show obvious clouds 100 Hours - no obvious clouds 119/219=56% of hours there were clouds in our aperture 831Cloudy 0132Mixed 1 09Clear CloudyMixedClear Operator Logs HR3VLS (Terra) Nightly Comparison