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

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

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

5. Terra Site – Vertical Laser laser

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 2HiRes 1 Air Shower

12. 30 EeV Shower

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

14. Mean 0.033 Mean 0.04 T = e -VOD T = e -VOD/sinӨ Ө VAOD - Vertical Optical Depth of Aerosol Component

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. Conclusion Installed a laser to test the reach of our HE aperture. Equivalent light production to a shower of ~6x10 19 to 10 20 eV Detectors have no trouble seeing this laser under good to worse than acceptable viewing conditions.

18. Extra Slides

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

20. Atmospheric Monitoring

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

22. 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

23. Atmospheric Measurements from Inclined Laser Shots

24. 45º 60º Detector Laser 12.6 km

25. Linearity Scaled by 10% !!!

26. 45º 60º Detector Laser 12.6 km

27. Clouds

28. Inclined Laser Shots clear hazy

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

30. 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.

31. 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