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Electron microscope in the garage. High voltage / SurprizingFacts

In the very first article, I wrote an approximate plan for our series, the final point of which is working with electronics. It's time to go over to him. All the rest is undermined, the leaks are found and corrected, the vacuum system is polished to mirror luster.

From electronics for experiments we have:

The discharge is, the power supply is switched off by overload, then turns back on again.

Since the high voltage it generates, then one wants to analyze it "quantitatively", or, more simply, measure the output voltage.
He thought about the voltage divider rummaged all the reserves of radio components passive electronic components, or rather, mega-ohm resistors.

Found green EXPLOSIONS

But even at the highest current divider need 30Mom. And in general, to test this source at maximum current is not an option.

I bought thirty 10MΩ resistors with a power of 1W and soldered them like this:

The paper is attracted spectacularly, and the Soviet dial gauge adds atmospheric.

But, the fact is that (and I was informed honestly by knowledgeable people), these resistors are designed for a maximum of 500 V. And in our case, the voltage drop on each one is

 $ 30,000 / 30 = 1000 $ "data-tex =" inline "/> </math>
<p> B. As a result, for small values ​​of the voltages, it was possible to see that the adjustment works.When the voltage rises above 15kV, breakdown starts in different places By the sound is audible), and to receive any reliable indication is no longer obtained I </p>
<p> There were no resistors for higher voltage at hand, but they were enough to make sure – the source produces high voltage and allows it to be regulated, in certain limits. </p>
<p> We must go further </p>
<h2> II. The aquarium </h2>
<p> <img src=
A fairly beautiful device, especially in comparison with oil-immersed power units of old microscopes.

The aquarium performs three main functions:

  • Adjustable cathode heat
  • Control of the first electrostatic lens (Venelt cylinder)
  • Has a socket, which includes a high-voltage fork of the microscope:)

The difficulty is that the entire cathode is under a negative high voltage, and it is necessary to "add" the voltage necessary for the cathode to this voltage. It was apparently not fashionable to make pulsed power supplies at that time, so an alternating transformer with a motor drive was made here, and a huge transformer for mixing this voltage into the high voltage part.

The displacement voltage of the Venelt cylinder is changed by rotating a variable resistor (the simplest implementation, Because special precision is not required there).

But with a rosette there was a difficulty – it's obviously not at all from this microscope. But, having lathes and milling machines, as well as desire, enthusiasm and a free evening, this task turns from a problem into pleasure.

The first video in this article shows how this happened.

Well, now it's up to the little one – to heat the cathode in its place, turn on high voltage and watch the emission of free electrons.

But, There was one more unsolved element. In the aquarium there is a board that must manage this all. The problem is that all connectors are disconnected, there is no documentation.

I was able to guess where to connect the variable transformer of the cathode glow (in fact, this connector is the only one that obviously came up) and the input transformer into the high-voltage part (there the connector numbers differed by one, probably the extension cable was). Otherwise, I'm not sure, and the algorithm of operation is strange: one relay is on self-picking through an optocoupler, the second is simply controlled from the connector. From the tips there there are only a few inscriptions.

Perhaps fresh ideas will tell?

Meeting in Moscow

From 11 to 13 April in Moscow in Sokolniki there will be an exhibition VacuumTechExpo (admission is free provided that you take care of an e-ticket in advance.)

Perhaps someone of you is interested and communicate with me personally? In the garage, everything can not fit :), and the exhibition presents a fairly thematic atmosphere, well suited to the project. Preferred time to write in the comments, perhaps it's around 12:00.

Thank you for reading, always glad to read your comments to both the article and the video. Until new meetings, I hope the electron beam will also be to the next series:)