About Me

My Photo

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




Saturday, March 26, 2011

DIY Scanning Electron Microscope - Sources, Costs and References

Metal aluminum window screen

Just a few linearity problems ;)

I used an oscilloscope's X and Y amplifiers for these images. It has much better linearity than my own, but not enough differential voltage or offset range.

The sum total of the big-ticket items shown in the video is $1485. This does not include hoses, wiring, raw metal, teflon, screws, a cabinet, etc. It also does not include an oscilloscope, which can be a very simple model (under $100 on eBay) as long as it has a z axis (brightness) input. Your diffusion pump or diffusion pump baffle may also require a water chiller.

Here are a list of information sources that helped me with this project:

Teralab - Homebuilt electron gun and other great projects

Popular Mechanics video on commercial desktop SEM

Hamamatsu - Supplier of PMTs

TV to oscilloscope circuit

CRT oscilloscope clock circuit

Charged particle optics simulation program

"A Simple Scanning Electron Microscope" P.J. Spreadbury -- Advances in Imaging and Electron Physics Vol 133 Chapter 2.5 (no link).

ISI SEM refurb at home

Great technical info on cathodes and wehnelt cup spacing. Most of the article concerns LaB6 cathodes, but there is a short paragraph on tungsten cathodes.

Numerous websites that gave background and operational information about SEMs.
Lots of web searches

Nearly all raw materials for this project were purchased from McMaster-Carr. All power supplies were purchased on eBay, or I already had them, in which case they came from a surplus store or flea market. Nearly all of the electronic components came from Jameco.

Monday, March 21, 2011

DIY scanning electron microscope - Overview video

Today, I finally produced an image with my DIY scanning electron microscope. I've spent the last few months working on this project, and am encouraged by today's success. There is still a lot of work left to do in making the image higher resolution, and eliminating sources of noise, however this image proves that all parts of the microscope are operating as designed.