Colin Humphreys: 1960s electron microscopes

Let’s say you have an optical microscope and let’s say you put a leaf say in the side of an optical microscope and you turn up the magnification, it still looks like a leaf, you know, I mean you see the veins in the leaf, they get bigger and bigger and so on but you can sort of tell it’s a leaf. You put something in an electron microscope, the image looks nothing like the object, so the key thing is to get back from the image and say what the object is. And that’s what my calculations did. So we were looking at defects in crystals, and my calculations enabled you to say what sort of defect it was in the crystal and the defects often control the properties of the crystal so they’re really important. An electron microscope was typically about eight feet tall, you had to be quite tall to operate it because a lot of the controls, you know, you stood on tip toe with your hands above your head operating something and there are knobs to turn and the – so you know, disadvantage if you were short. The electrons hit what was called a fluorescent screen so the electrons come down and you can’t see the electrons but they hit a screen which fluoresces when the electrons hit it so they send out green light and you look at this green light through a piece of lead glass. Because you need lead glass to stop – because there’s x-rays generated as well as electron. And so you watch this piece of lead glass and then there’s a lever and you flip the screen up and then the electrons hit a photographic plate and you just timed a recording. And in the old days you guessed this, you looked at the picture and said, ‘Hmm, that doesn’t look very bright, that’s probably five seconds exposure,’ and so, you know, you flip the screen up and counted one, two, three, four, five, flip the screen down and you hoped you’d got an image. And it was that crude at that time. I mean it’s crude but it did involve judgement as well. There were technicians to help maintain them but students tended to do this themselves so the technicians did a lot of the photography because there was just so much of that but even so if you were a really good photographer and you had a really important image you often would actually develop yourself and so you’d just go into the darkroom and there’d be developing dishes, you know, you’d go into developer and fixer and so on. Yeah, and in fact, and then your magnified image yourself, you know, going through – you produce a print and magnify from the negative onto the print and so on. So if it’s really important you probably did it yourself.

  • Interviewee Colin Humphreys
  • Duration 00:02:19
  • Copyright British Library Board
  • Interviewer Thomas Lean
  • Date of interview 10/19/2012
  • Shelfmark C1379/88

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