Open Source Freakin' Scanning Electron Microscope

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With all the relatively cheap thermal, high speed cameras and other misc. scientific equipment out there, the age of the citizen scientist has never looked better. Even equipment costing tens of thousands of dollars just 10 years ago has dropped to the point where many people can actually afford them without selling a kidney. You'd think that after 79 years the same could be said for electron microscopes. Due to their size, mandatory accessories and operating needs, you can't just go out, find a used one, plug it in and go. Hopefully, with a few compromises and the right design, it'll be possible to build one with commonly available and inexpensive parts.

A project like this isn't for the faint of heart, but when you have an ISI-100A SEM that needs some control electronics and is missing some hardware just sitting across the street collecting dust, the light at the end of the tunnel gets a little brighter. It's been sitting unused for ~15-20 years in a school then museum; no one really remembers, so it needed a little TLC first. When I tore this thing down and realized just how simple the hardware is, I knew I had to take this opportunity to help design an SEM that others with access to a basic machine shop can build. Now all the maintenance and busywork has been finished, the microscope itself is now ready for some development.

Hate to throw this out, but for now, this is being powered by fairy dust, unicorn farts, and a budget that would make the poorest of students look like Donald Trump, so if there's anything you can spare, you just might save the lives of all our orphaned puppies. They really need some components:

-ANY information on this microscope - I've reverse engineered most of the electron optics stuff and ET detector, but the backscatter detector, HV supply is still, unknown

-Some kind of fast ADC; I've got some slower, high-resolution ones I've mocked up and tested, but they're are only like 10 Ksps (though have 16 channels, those I'd like to save for other instrumentation). I've got an older 60MHz 100 Msps TDS100 scope, but It's not mine and I seriously doubt the owner will enjoy coming to the hackerspace and seeing that.I'd like to use something someone could simply buy without mucking.

-Vacuum grease - a friend 'borrowed' a used tube from his place of employment (I swear officer, it wasn't me, I'm unemployed... no really), but after having to cut the tube open to extract every last bit, it's safe to say I'm out.

-Thin tungsten wire - I got a filament, but I have no idea how long it'll last, if it works at all

-Some kind high-vacuum gauge - I've got my old Edwards low-vacuum piranni gauge, but it is waaay out of whack since the backstreaming incident with my mirror coater. PROTIP: Always assume that, if the power goes out while pumping down, and there's no safety valve, the bottom of the vacuum chamber gets flooded with oil.... so don't mount the gauge THERE. Thankfully, though, I've got a lower-vacuum thermocouple gauge now that kinda works - it twitches all over the place most of the time. Some percussive maintenance usually helps. But I still need a high-vacuum gauge.

-Anything else at all

So please, think of the puppies :)

  • Alas, 'tis no more...

    Adam Guilmet08/21/2017 at 19:10 1 comment

    Well, so much for that.

  • Juicing up the ISI-100A Scanning Electron Microscope - Power Supplies

    Adam Guilmet12/26/2016 at 03:43 0 comments

    Looks I've stacked quite the array of old power supplies here! Coincidentally, I've got the same high-voltage power supply Ben Krasnow used in his SEM build (3rd from the top.) I think all these should cover the various lower voltage supplies I'll be needing. I've got a power supply for the filament heater, the physical vapor deposition rig (that's going to be a separate project unto itself), the photomultiplier tube, and the Everhart-Thornley detector's grid. The 10 kV phosphor screen supply is still needed, but I've building that one. Next up is the 30kV acceleration supply...

  • Roughing up the ISI-100A Scanning Electron Microscope

    Adam Guilmet12/03/2016 at 01:58 0 comments

    Now to get the vacuum system plumbed and get a roughing gauge hooked up. The scope originally had an 'Environmental Control Module' but the strange thing was that there was no way it could be actually connected. I think it must have be used with a matching vacuum deposition rig or something. So I just tapped a fitting on the anti-suckback valve that way I can actually save some trouble and just use the ECM's gauge and venting solenoid

    Now all I have to do is turn it on and pray I didn't anger the vacuum gods somehow.

    SUCCESS! I was dreading roughing this thing down for the first time, and NO LEAKS! That's some serious luck right there. Seems like the major surgery went OK. I don't want to test out the diffusion pump just yet, though. I first have to locate a high vacuum gauge and a known good low vacuum gauge because I have absolutely no idea how accurate this one is. Hopefully, it's not too far off. Damn, what a mess. Now to clean up and hope that I don't cause any leaks....

  • Hacking the ISI-100A Electron Microscope - Scanning Coils and Stigmator

    Adam Guilmet11/30/2016 at 15:24 7 comments

    Now part that turns this from high-energy flashlight into an SEM; the scanning coils. Once the beam has been through the condensing coils, it passes through the scanning coils. These are saddle shaped coils that guide the beam from in a rectangular raster pattern across the the sample stage.

    You'd think there'd be only two coils; one for X and one for Y, but I'm not so lucky. On this particular unit, there's eight scanning coils. The designers must have hated the assemblers, because of all the small heatshrunk connections and tied up with wax string. Whole lot of nope; probably would have destroyed it moving bundles out of the way to see underneath. It's hard to see in the picture below, but with the help of a long strand of hair I stole from another member, a drill bit and webcam, it was a simple matter to just brute force it.

    Voila! Drill bit electron beam!

    It is exceptionally difficult to create a magnetic system with an acceptable beam without some form of correction. Those eight small coils at the bottom actually have nothing to do with the scanning; they are the stigmator. It serves to correct the misshapen beam, which is pretty much unavoidable. They stretch and squash the beam to help to get as close to a circle-shaped spot to trace across the sample.

    In the first photo above, there are actually two sets of scanning coils, one upper and one lower. I really don't have a clear reason why they are separated like this. My gut tells me that it's to reduce the inductance and allow for a faster scan speed, or since it had a fully analog scan system, maybe it had something to do to with helping correct for distortion that couldn't be easily done otherwise, but I don't really know for sure. Are there any SEM engineers out there that can shed some light on this?

  • Hacking the ISI-100A Scanning Electron Microscope - Focusing Coils

    Adam Guilmet11/30/2016 at 07:12 0 comments

    So first thing on the way to getting this thing operational again is to figure out what the hell all these coils actually do. In the photos below, you can see the objective and the two condenser focusing coils. The coils look beefy but I'm guessing each of these coils would carry a maximum of a couple amps, as the feeding wires are only around 20 gauge and had a 8 foot run back to the original controller. As I have ZERO information on this SEM, most of the specs for the electronics is going to be pulled out of my nether regions and tweaked until it works, so if anyone has any better starting parameters, please share!

    The assembly of the these is fairly straight forward; everything just stacks together on the steel beam tube. The great thing is that the only section in this assembly actually carrying high vacuum is this tube.

    This is the business end of the stack. The entire stack is then inserted into a quite thick steel liner. The deflection and stigmator coils(more on those later) fit right inside the objective coil here. As of now, I'm still figuring out the pinout, field shape, etc.

    Notice the coils are each fully surrounded by the steel jacket on the outside and the steel discs on the top and bottom, and that tube at the center is made of sections of a high-permeability copper alloy and steel. The copper affects the magnetic field relatively little so it effectively acts as the gap in the picture below. The gap is important to effectively 'shape' the electron beam to a tight point.

    (from definitelyGO HERE if you want to learn more)

    EDIT: Here's a better photo so you can see what I mean about the copper gaps

  • Restoring the ISI-100A Scanning Electron Microscope - Pregame

    Adam Guilmet11/29/2016 at 10:53 0 comments

    Being around 35-40 - years old and being neglected for almost half that, there is quite a bit to work on to just get the microscope to a point where I can work on the real man's stuff:

    -Full teardown to replace o-rings and grease

    -Cleaning the god-awful, ancient gunk out of the diffusion pump. Then cleaning everything sticky around me.

    -Making a couple port covers; one with a mount for a vacuum gauge

    -Fixing the broken cage on the secondary electron detector.

    -Quite a bit of other small stuff

    Most of that stuff was finished before I started using, so sorry, no pictures or anything.

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Butch O'Dowd wrote 08/21/2020 at 19:18 point

Challenging project, and good luck. A long time Electron Microscope Field Service Company is liquidating lots of  TEMs,  parts, accessories and even service manuals. Also parts for SEMs, and other lab equipment spanning decades of different production lines. Philips, Zeiss, JEOL, Amray, and more. Auction will continue to have more listings added throughout September.!/philips-em420-electron-microscope-199684!/auctions?ilt=1&sid=40479

Their twitter page @ScientificInst2 

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felixk1991 wrote 11/06/2019 at 11:17 point

Very nice project, thank you for sharing with us!

I think i can answer your question regarding the necessity for two separated scanning coils:

You always need two sequential deflectors, because with one deflector, you can not induce a beam shift with out creating an unwanted tilt of the electron beam. If you have two deflectors you can tune the scanning unit in a way to have tilt-free shift of the electron beam and vice versa.

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helge wrote 12/25/2016 at 13:38 point

eye-wateringly beautiful project. Love it!

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David C. Bishop wrote 12/22/2016 at 22:18 point

You know you can go from a SEM to a electron beam lithographer with the edition of a beam blanker. Then make your own microchips ☺

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Jerry Biehler wrote 12/03/2016 at 00:13 point

Nice. Used SEMs are all over the place, just look on ebay. I have seen some really nice scopes go though ebay in the past 6 months I would have loved to have and dont have the room/money. A friend now has three sitting in his garage that he got for cheap on ebay.

If you give up on it I would love to buy that backscatter detector from you. I am trying to rig up backscatter on my Hitachi at home. 

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zakqwy wrote 12/01/2016 at 17:02 point

Definitely need to ping @Ben Krasnow on this one...

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ajlitt wrote 11/29/2016 at 14:08 point


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