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I previously worked on Virtual Reality and other hardware at Valve.  I currently work at Google[x].

Prior to starting at Valve, I built computer peripherals such as keyboards, mice, and joysticks that were designed to be used inside MRI machines.  My company, Mag Design and Engineering, sold these devices directly to researchers at academic institutions who used them to publish scientific papers in peer-reviewed journals.

After work, I spend time on many different types of projects that usually involve circuit design, machining, material selection, and general fabrication/hacking.  My favorite place to be is my home workshop.

ben dot krasnow at gmail




Monday, January 6, 2014

Ruby laser design process

I describe the basics of ruby laser design. I'm building a laser with about 8KJ of electrical pump energy.






  1. Hi Ben,

    as always: Great work!
    You might want to check this website: http://www.pulslaser.de/
    The owner is building all kinds of lasers including ruby and YAG ans q-switched ones.
    Also check his other website: http://www.rapp-instruments.de/
    Both sites are a great source of inspiration albeit in germen. But you will get the point.
    Keep up that great work.


  2. Ben, here is the link for the pop sci story abt "Build Your Own Laser!"


  3. Pump with 8 KJ energy - or 5 kW power?

  4. Have you looked at the waveform across your cap bank? I would imagine that with such high currents, it would be almost impossible to get a high enough dI/dt to avoid pretty severe ringing, and you'd be seriously limiting the life of those 'lytics.

  5. Joshua, the original cap bank was used at 900V in the Speedotron, and did not include balancing resistors or intentional inductors. It had an underdamped discharge into the stock 4.8KJ tube. It's true that at higher voltages with more caps in series, I might have more problems. I haven't noticed any ringing though. The ESR of the caps and the resistance of the xenon arc itself add up to 5-10 ohms probably.