Atmospheric Monitoring at HiRes

Status

Enhancements

Lawrence WienckeHiRes NSF ReviewNov. 22 2002Washington 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

Shower Detector

Atmospheric Monitoring

Clear Air Location - Go to a remote Desert

ReduceGround 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

SimulationData

ph

oto

ns

Scattering Angle

Fit of Horizontal Laser Shot

Example of Extracting phasefunction

Mean 0.040

What is Vertical Optical Depth?

T = e-VOD

T = e-VOD/sinӨ

Ө

VAOD - Vertical Optical Depth of Aerosol Component

Mean 0.033

Mean 0.043

Normalize toClear Night Data

Normalize To Simulated Data (no aerosols)

north

south

HR1detector

laser

Test Horizontal Uniformity

DetectorLaser

3.5 km2.5 km

Compare VAODfor different heights

DetectorLaser

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

Sh

ow

er

Axis

Pick commonly viewed track segment

For each eye, reconstruct amount of light from that segment

Correct fordistance and atmospheric attenuation

Compare results at both eyes

If the correction is too large the further reconstruction is brigher

VAOD = 0.1HAL = 12 kmSC = 1.2 km

VAOD = 0.0

VAOD = 0.04HAL = 25 kmSC = 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) = 0.04 +/- 0.02(sys) +/- 0.001 (stat)

Horizontal Aerosol Scattering Length at ground level (HAL)HAL(avg) = 25km

Combined VAOD*HAL -> effective scale heightSH(avg) = 1km

Also in Progress.. Reconstruction of inclined laser shots

Enhancements in Progress

Roving Laser TestsShoot The ShowerDistant Laser and Mirror

Shoot the Shower• HR1 detector -> HR2SLS

HR2

FADC

Request RequestedList

Check Requests

ServicedList

Shot Pattern

hr2sls

inte

rrup

t

RequestedList

Somethinginteresting

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 20-35 km distances• Of light sources we understand

– Increased sensitivity to atmospherics

– Less sensitivity to absolute calibration

35 km

25 kmhr1

hr2

Terra SiteInteresting Features

Similar Elevation to HR1, HR2Power and Phone available22 km to hr1, 35 km to hr2Nearly in line with hr1, hr2Not on Dugway!!!!!~1hr 20 minutes to U of U

hr2 hr1Terra

Terra Site

laser

Vertical Laser Shot Fired from Terra as recorded

by HiRes2 32.7 km distant

Laser Energy ~3.5mJLaser Wavelength 355nm

Npe ~300

Npe ~200

Npe ~40

Terra - StatusLaser Installed, will begin operation for next run

Mirror will follow in a month or two

Portable mirror in a “connex” shipping container.

HR1 HR2 Terra

Co-Linear Arrangement of mirrors and lasers

5km

10km

15km