Atmospheric Monitoring at HiRes Status Enhancements

1. Atmospheric Monitoring at HiResStatusEnhancements Lawrence Wiencke HiRes NSF Review Nov. 22 2002 Washington DC

2. At 1999 ICRC - Preliminary results from monocular measurement of CR energy spectrum ~6 super GZK candidates • At 2001 ICRC - HiRes reported monocular measurement of CR energy spectrum ~2x statistics, but ~2 super GZK candidates What Happened?

3. Shower Detector Atmospheric Monitoring Essential - The Calorimeter Challenging - Light Propagation

4. Location Matters Clear Air Location - Go to a remote Desert Reduce Ground Effects - Put detectors on Hills

5. Technique • Use Lasers as a “test” beam • Observe the tracks they make with the same detector that observes tracks from extensive air showers

6. Laser Detector

7. Parameters Measured • Vertical Aerosol Optical Depth • Horizontal Scattering length at Ground Level

8. Fit of Horizontal Laser Shot photons Simulation Data Scattering Angle

9. Example of Extracting phase function

10. Mean 0.040

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

12. Mean 0.033 Mean 0.043 Normalize to Clear Night Data Normalize To Simulated Data (no aerosols)

13. north HR1 detector laser south Test Horizontal Uniformity

14. Compare VAODfor different heights 3.5 km 2.5 km Detector Laser

15. 3.5 km 1.5 km Laser Detector

16. Why to we think the 0.04 average is correct? Check using showers observed by both eyes. Shower Axis HiRes - I HiRes 2 Pick commonly viewed track segment For each eye, reconstruct amount of light from that segment Correct for distance andatmospheric attenuation Compare results at both eyes If the correction is too large the further reconstruction is brigher

17. Apply three different aerosol models to same data VAOD = 0.1 HAL = 12 km SC = 1.2 km VAOD = 0.0 VAOD = 0.04 HAL = 25 km SC = 1 km

18. Characterized the average atmosphere at Dugway Vertical Aerosol Optical Depth (VAOD) VAOD(avg) = 0.04 +/- 0.02(sys) +/- 0.001 (stat) Horizontal Aerosol Scattering Length at ground level (HAL) HAL(avg) = 25km Combined VAOD*HAL -> effective scale height SH(avg) = 1km This work also tests calibration Average has been verified with stereo air shower data

19. Also in Progress.. Reconstruction of inclined laser shots

22. Enhancements in Progress Roving Laser Tests Shoot The Shower Distant Laser and Mirror

23. Shoot the Shower • HR1 detector -> HR2SLS hr2sls Something interesting interrupt HR2 Shot Pattern Date, Time, Mirror, 1st PMT, Last PMT, Pseudo Distance, Trigger Flag Check Requests FADC Requested List Serviced List Request Requested List

24. Roving Laser • Motivation • Portable “Test Beam” • Study Calibration and detector response • Features • 0.1 degree pointing accuracy • 355nm wavelength • Absolute calibration to within 10%

26. Energy Balance Simpsons Springs Roving Laser Shots

27. Adding a distant Laser and Mirror • First HiRes results are consistent with GZK feature (cutoff?). • How well do we understand detector response for GZK candidates? • Do the “Big? One’s” get away? • Can we really see as far as we think we can? • Dugway lockout provided motivation to test this. • Set up equipment off base • Make routine, redundant measurements • Over 20-35 km distances • Of light sources we understand • Increased sensitivity to atmospherics • Less sensitivity to absolute calibration

28. 35 km hr1 25 km hr2

29. Terra Site Interesting Features Similar Elevation to HR1, HR2 Power and Phone available 22 km to hr1, 35 km to hr2 Nearly in line with hr1, hr2 Not on Dugway!!!!! ~1hr 20 minutes to U of U hr2 hr1 Terra

30. laser Terra Site

31. Vertical Laser Shot Fired from Terra as recorded by HiRes2 32.7 km distant Npe ~40 Npe ~200 Npe ~300 Laser Energy ~3.5mJ Laser Wavelength 355nm

32. Terra - Status Laser Installed, will begin operation for next run Mirror will follow in a month or two Portable mirror in a “connex” shipping container.

33. Terra Co-Linear Arrangement of mirrors and lasers 15km 10km 5km HR1 HR2