[Sem] SEM updates

[Jeff Miller]

Actually I've solved the imaging problems. Several years ago I designed a fairly sophisticated digitizer for my own Mini-iSEM. You can dial in resolutions of any power of two in the range of 512x512 up to 16Kx16K. It digitizes at about 800 KS/s, 16 bit resolution. It gets around the format problem by driving the X and Y axis with a pair of DACS that are updated in the same loop as the sample is taken. There are hooks in the design for dynamic focus and control of all the other parameters, though only the basic X, Y, and brightest data are currently implemented. But that's all that's really needed. 


The design uses a demo board from Silicon Labs featuring their 16 bit ADC. At the time the board was $25. It's no longer available, though you might find one by trawling on ebay. It also uses a line camera card from National Instruments which I was lucky to find on Ebay for about $300 at the time. The card comes with sufficient free demo and utility software to view and capture the imagery. 


I hand coded the software that gets downloaded to the demo board in assembly language. The demo board really just glues the ADC to the strict and quirky timing requirements of the line camera card.

I've applied test signals to the unit and I'm confident it will work as it should, though it will need signal conditioning.


I dropped the project when it came time to wire it up to the MiniSEM. I started dragging my feet when it came time to order all the mil-spec AMP circular connectors and build a complete replacement for the console. Besides, my SEM is in pieces after getting halfway through replacing all the o-rings. 


Getting rid of the console was my main goal, as I wanted to bring it around to High Schools for demonstration. 

But for "our" purposes, it should be pretty trivial to inject the driving signals into the amps and magnification divider network of the existing console. 


I don't mind lending out the digitizer. However, I was not able to find the computer that has the software the last couple times I looked. 

As for the scope's whereabouts and where it should end up, I'd like it to end up somewhere we could more or less pick up where we left off,  and where it would be available for those who were interested and for like minded individuals. 


As for sample prep, I've been gathering parts here and there that might be useful. In particular I've been collecting 
glassware which might serve as the coating chamber. I've been trying to find a nomogram for safe operating pressure of glass tubing with a given diameter and thickness. I know I've seen them before but haven't been able to find them across a few web searches in recent years. I think I saw them in catalogs either by manufacturers such as Corning and the Kimax people, or perhaps fabs like Ace Glass. 

-Jeff






________________________________
 From: Chris Murphy <chrisnoisebridge at gmail.com>
To: Alan <alan at halo.nu> 
Cc: "sem at lists.noisebridge.net" <sem at lists.noisebridge.net> 
Sent: Wednesday, March 12, 2014 7:57 PM
Subject: Re: [Sem] SEM updates
 

I wouldn't exactly call it a toy. It is a prototype. I don't think anyone has ever looked at a sputter coated specimen with it during its time at Noisebridge. 

The tough part about digitizing the signal is that it's not NTSC, PAL, etc. It's just an analog raster. If I recall, there are industrial LCDs that cost about $900 that can do this job. They are designed to replace CRTs in this kind of equipment. Otherwise one could digitize the signal by replacing the PMT with an avalanche photo diode at some cost to image quality. There are other approaches that preserve the PMT but would require some good video card and PMT hacking skills. 

The key issue is that before all this work takes place, a lab for specimen preparation and proper storage of the SEM needed to be built out. 

We tried but the endeavor was not easy in the face of noisebridge's open access policy (which I support, even at the cost of science). 

The challenge made me really contemplate what the ultimate hacker space arrangement would be.
 Both in physical layout and access policy. 

See paragraph #2 of my post here:
https://lists.sudoroom.org/pipermail/sudo-discuss/2013-September/003681.html

Chris

Sent from my iPhone

> On Mar 12, 2014, at 18:53, Alan <alan at halo.nu> wrote:
> 
> It is at Milo's house in Oakland.  
> 
> 
> If you want to use it you could probably ask him for it and he might give it to you, if you have a good place to put it.
> 
> I have used it a few times and in my opinion it is just a toy,
 I haven't been able to get any good images out of it.  
> But if you want to work on it and make it better it might be able to give you really good images.   Needs better image processing, the tv is not sufficient really.
> 
> 
> 
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> SEM mailing list
> SEM at lists.noisebridge.net
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