Probing the HiRes Aperture near 1020 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

Experimental Configuration

Laser vs. Air Showers

Cross Check Atmospheric Aerosol Optical Depth

35 km

HiRes 1

HiRes 2

Terra (Laser)

Terra Site – Vertical Laser

laser

Laser Parameters

Wavelength 355nm

Energy 2-6mJ (adjustable)

Distance 34km to HiRes 222km to HiRes 1

Direction Fixed - Vertical

Polarization Random

Laser Beam – polarization measurements

LA

SE

RP

robe

Depolarizer

Analyzer

Linear Polarization

Random Polarization

Vertical Laser Shot Fired from Terra as recorded by HiRes2

34 km distant

Laser Energy ~3.5mJ

19km

10km

HiRes 1

HiRes 2

Terra (Laser)

Shower~30 EeV

How does the laser compare to a shower?

HiRes 2 HiRes 1

Air Shower

HiRes 2 HiRes 1

Air Shower

30 EeV Shower

Laser Shower Equivalent4mJ 6x1019 eV

6mJ ~1020 eV

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

Compare vertical aerosol optical depth

Terra Laser + HiRes2 detectorHiRes2 Steerable Laser + HiRes1 detector

What is Vertical Optical Depth?

T = e-VOD

T = e-VOD/sinӨ

Ө

VAOD - Vertical Optical Depth of Aerosol Component

Ө2Ө1

LASER DETECTOR

TA2 TM2TA1 TM1

NL NOBS

SA + SM

Measurement of VAOD

2A2MAM1A1MLOBS TT)S(STTNγNγ

2MM1MLMOL TSTNγNγ

MOL

OBS

21 N

Nln

sinθ1sinθ1

1VAOD

)sin/( VAODA eT

MA SS Then for

Atmospheric Measurements from Inclined Laser Shots

45º

60º

DetectorLaser

12.6 km

HiRes 1 detector measuring inclined laser track

HiR

es2

dete

ctor

m

easu

ring

Ter

ra L

aser

Tra

ck

Conclusion

Installed a laser to probe the reach of our HE aperture (34 km Distant)

Equivalent light production to a shower of ~6x1019 to 1020 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

Extra Slides

Linearity

Scaled by10% !!!

45º

60º

DetectorLaser

12.6 km

Clouds