1. Probing the HiRes Aperture near 10 20 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 1.3.22 Aug. 2 2003 Tsukuba Japan

2. Experimental Configuration Laser vs. Air Showers Cross Check Atmospheric Aerosol Optical Depth

3. 35 km HiRes 1 HiRes 2 Terra (Laser)

4. Terra Site – Vertical Laser laser

5. Laser Parameters Wavelength355nm Energy2-6mJ (adjustable) Distance34km to HiRes 2 22km to HiRes 1 DirectionFixed - Vertical Polarization Random

6. Laser Beam – polarization measurements LASER Probe Depolarizer Analyzer Linear Polarization Random Polarization

7. Vertical Laser Shot Fired from Terra as recorded by HiRes2 34 km distant Laser Energy ~3.5mJ 19km 10km

8. HiRes 1 HiRes 2 Terra (Laser) Shower ~30 EeV How does the laser compare to a shower?

9. HiRes 2 HiRes 1 Air Shower

10. HiRes 2HiRes 1 Air Shower

13. 30 EeV Shower

14. LaserShower Equivalent 4mJ 6x10 19 eV 6mJ ~10 20 eV

15. Mean 0.033 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

16. Compare vertical aerosol optical depth Terra Laser + HiRes2 detector HiRes2 Steerable Laser + HiRes1 detector

17. What is Vertical Optical Depth? T = e -VOD T = e -VOD/sinӨ Ө VAOD - Vertical Optical Depth of Aerosol Component

18. Ө2Ө2 Ө1Ө1 LASERDETECTOR T A2 T M2 T A1 T M1 NLNL N  OBS S A + S M Measurement of VAOD Then for

19. Atmospheric Measurements from Inclined Laser Shots

20. 45º 60º Detector Laser 12.6 km

21. HiRes 1 detector measuring inclined laser track HiRes2 detector measuring Terra Laser Track

22. 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 10 20 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

23. Extra Slides

24. Linearity Scaled by 10% !!!

25. 45º 60º Detector Laser 12.6 km

26. Clouds

27. Inclined Laser Shots clear hazy

28. HiRes 1 detector measuring inclined laser track HiRes2 detector measuring Terra Laser Track

29. 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 6/28/2003 337nm – HR1 Erecon/Elaser 0.75 M. Seman Analysis 355nm HR1 0.80 337nm HR2 0.81 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) 1. 2. 3.

30. Clouds Laser found clouds on 25% of nights that the operator called clear HR3VLS Clouds 219 Hours operation w/ stereo Jan-May 2003 119 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