On April 14, Russ Blakeman wrote:
> You and I both Sellam - this is like looking at stuff when we were in grade
> school - like the fly that looked like a monster. Is this machine one the
> large heavy ones I've seen in older books or have they brought the
> electromicrograph machines to a reasonable size? I'd hate to even ask what
> one surplus would set a person back.
They're all large and heavy. Because semiconductor and computer
technology shrinks constantly, there's a natural assumption that
everything else does too, and thus anything that's large is ancient.
There's really no way to shrink the vacuum valves, pumps, high-voltage
power supplies, and stuff like that...what does shrink is the control
electronics, but that's really all. Generally speaking, there have
been NO applicable significant advances in the major technologies that
make SEMs work in the past 30 years...electron beam generation,
acceleration, and steering, vacuum chamber control, phosphorescent
electron->photon conversion, and high-speed scintillation detection.
Until fairly recently, all new SEMs had huge panels of lights,
switches, and knobs. Nowadays manufacturers are shipping SEMs with a
power switch and a PeeCee running Windows that does everything between
crashes. The average scientist hasn't really embraced this approach,
so there's a huge business building around maintaining older-style
manual-control SEMs. My SEM does happen to be pretty old, but not too
old as SEMs go. It was made in 1981. I have been in contact with the
guy who had maintained it under a service contract at its previous
installation. He is a former employee of the company that
manufactured the unit. He runs a fairly tidy business maintaining
only this make and model of SEM within driving distance (he's north of
me in Southern PA), he maintains fifty or sixty of them...indicating
that a significant number of these 20-year-old instruments are still
in service.
For your SEM hunting information, count on about a ten-to-one age
ratio compared to computer hardware...a 20-year-old SEM would be
approximately comparable to a 2-year-old computer.
> Maybe Dave can get a photo of his stuff in place and put it in the image
> library as well for use to take a look at.
I did that yesterday. Have a look at
http://www.neurotica.com/sem.
-Dave McGuire
Received on Sat Apr 14 2001 - 13:03:16 BST