Atmospheric Monitoring at HiRes Status Enhancements Lawrence Wiencke HiRes NSF Review Nov Washington DC

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?

Essential - The Calorimeter Challenging - Light Propagation ShowerDetector Atmospheric Monitoring

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

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

Laser Detector

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

Simulation Data photons Scattering Angle Fit of Horizontal Laser Shot

Example of Extracting phase function

Mean 0.040

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

Mean Mean Normalize to Clear Night Data Normalize To Simulated Data (no aerosols)

north south HR1 detector laser Test Horizontal Uniformity

Detector Laser 3.5 km 2.5 km Compare VAOD for different heights

Detector Laser 3.5 km 1.5 km

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

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

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

Also in Progress.. Reconstruction of inclined laser shots

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

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

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

Energy Balance Simpsons Springs Roving Laser Shots

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 km distances Of light sources we understand –Increased sensitivity to atmospherics –Less sensitivity to absolute calibration

35 km 25 km hr1 hr2

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

Terra Site laser

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

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.

HR1HR2 Terra Co-Linear Arrangement of mirrors and lasers 5km 10km 15km