Post subject: Cryotron circuits? Posted: Mon Nov 17,
2008 1:10 pm
Joined: Tue Dec 26, 2006
Anyone here ever use a Cryotron? Ever seen
one? I am curious when (if) they fell out of use.
"the transistor" become faster than a cryotron?
When did "the
transistor" become cheaper than a cryotron?
Do you know
of any interesting applications of these things other than as logic
/ memory devices?
These were not ever RF circuits (were
they?). However, I thought I would check here to see if anyone has
any experience or stories about these things.
Post subject: Posted: Tue Nov 18, 2008 11:48 am
Joined: Thu Sep 25, 2003 1:19 am
The following information is just
off of the top of my head. I did not find this is on Wikipedea.
The cryotron is a switch that operates using superconductivity.
The cryotron works on the principle that magnetic fields destroy
superconductivity. This simple device consists of two superconducting
wires ( e.g. tantalum and niobium) with different critical temperature
(Tc). A straight wire of tantalum ( having lower Tc) is wrapped
around with a wire of niobium in a single layer coil. Both wires
are electrically isolated from each other. When this device is immersed
in a liquid helium bath both wires become superconducting and hence
offer no resistance to the passage of electric current. Tantalum
in superconducting state can carry large amount of current as compare
to its normal state. Now when current is passed through the niobium
coil (wrapped around tantalum) it produces a magnetic field, which
in turn reduces (kills) the superconductivity of the tantalum wire
and hence reduces the amount of the current that can flow through
the tantalum wire. Hence one can control the amount of the current
that can flow in the straight wire with the help of small current
in the coiled wire. We can think tantalum straight wire as a "Gate"
and coiled niobium as a "control".
A planar cryotron was
invented in 1957, made of thin films of lead and tin. This was one
of the first integrated circuits, although using superconductivity
rather than semiconductivity. In the next few years a demonstration
computer was made and and arrays with 2000 devices operated. A short
history of this work is in the newsletter of the IEEE History Center,
number 75, November 2007.