SAM PDR 1

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SAMSAM

Andrei Tokovinin

SAM LGS Preliminary Design Review September 2007, La Serena

1. ANSI Z136.6-2000, Safe use of Lasers Outdoors2. Henderson, R. & Schulmeister, K.,Laser Safety (2004)

SAM PDR 2

SAM laser & LGS

Wavelength 355nm

Average power 10 W

Pulse frequency 10 kHz

Pulse duration 34 ns

A 3 107

B 4 105

C 415

D 1.6 105

Energydensity,W/m2

Class IV laser, dangerous!

SAM PDR 3

Laser radiation hazards

Eye damage (visible at >380nm)

Thermal damage of skin & cornea

Photo-chemical damage ( <320nm)

Only thermal damage is relevant for SAM

Maximum Permissible Exposure (MPE)for skin and cornea is the same. However, skin regenerates, eyes don’t

SAM PDR 4

MPE levels (ANSI Z136.6)

Laser beam

Expanded beam

Spot at 7km: 11ms

LLT beam

Aversion time 10s

SAM is safefor condors!

SAFE

SAM PDR 5

Safe working distancefor scattered radiation

For 10-s exposure: 6cm

For 8h exposure: 3.1m

Light scattered into the dome is not dangerous

Other hazards

High voltage (Pockels cell in SAM)

Fire & smoke if something burns

SAM PDR 6

Airplanes & satellites

Airplane moving at >4 km/h crosses the 1-cm spot in <11ms, SAFE. Letter to DGAC to waive laser spotters. Helicopters need coordination

Satellites can be illuminated (estimate 10% probability per satellite in 500 nights of SAM operation)

Space Command clearing house is informed, waiver possible? (beam divergence 43 rad or 8”)

At worst, we submit the target lists, as other LGS AO

SAM PDR 7

Safety engineering

Mode 1: SAM is not used Prevent accidental switching of the laser (remove the key)

Mode 2: SAM observations It is safe to be inside the dome with laser on

SAM LGS must be safe in case of single-mode failure

Engineering measures: interlocks, UV detector

Mode 3: Maintenance and alignment Potentially dangerous, laser-trained persons only!

Develop detailed plans (think first, then act)

Use green alignment laser and CCD detectors when possible

Wear protective clothes and goggles

SAM PDR 8

Summary

The 355nm wavelength is good for safety

Class I (embedded) during normal use, no

precautions needed

Maintenance may be risky

Coordination with the Space Command may

complicate the use of SAM (like any LGS)

Similar lasers are used in the mask-cutting machines at Gemini

Class III laser in each DVD burner!