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L aser S afety for SAM

SAM LGS Preliminary Design Review September 2007, La Serena. L aser S afety for SAM. 1. ANSI Z136.6-2000, Safe use of Lasers Outdoors 2. Henderson, R. & Schulmeister, K., Laser Safety (2004). Andrei Tokovinin. SAM laser & LGS. Wavelength 355nm Average power 10 W

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L aser S afety for SAM

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

  2. SAM laser & LGS • Wavelength 355nm • Average power 10 W • Pulse frequency 10 kHz • Pulse duration 34 ns Energy density, W/m2 Class IV laser, dangerous! SAM PDR

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

  5. SAM PDR 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

  6. SAM PDR 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 PDR 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 PDR 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!

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