1. SAM PDR1 Laser S afety forSAM Andrei Tokovinin SAM LGS Preliminary Design Review September 2007, La Serena 1. ANSI Z136.6-2000, Safe use of Lasers Outdoors 2. Henderson, R. & Schulmeister, K., Laser Safety (2004)

2. SAM PDR2 SAM laser & LGS Wavelength 355nm Average power 10 W Pulse frequency 10 kHz Pulse duration 34 ns A3 10 7 B4 10 5 C415 D1.6 10 5 Energy density, W/m 2 Class IV laser, dangerous!

3. SAM PDR3 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

4. SAM PDR4 MPE levels (ANSI Z136.6) Laser beam Expanded beam Spot at 7km: 11ms LLT beam Aversion time 10s SAM is safe for condors! SAFE

5. SAM PDR5 Safe working distance for 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

6. SAM PDR6 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

7. SAM PDR7 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

8. SAM PDR8 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!