From: terry@asl.dl.nec.com
Subject: Re: electrostatic fusion
Originator: terry@aslss01
Organization: (Speaking only for myself)
Date: Thu, 31 Dec 1992 05:51:18 GMT

Hi folks,

(No, I have not disappeared.  I will be sending a largish contribution on
the issue of cavitation fairly soon.  It scared the daylights out of me when
my off-the-cuff ramblings came so close to real experiments of which I had
no knowledge.  Cold glycerin/water cavitation _really does_ give UV?  Wow!)


In article <1992Dec29.112835.62319@cc.usu.edu> system@cc.usu.edu writes:

> Introduction:  Researchers at Hill Air Force Base have recently
> submitted a patent application concerning the use of electrostatic
> devices for creating nuclear fusion ...
> The sharp points produce enormous fields. In the phenomena known as
> Saint Elmo's fire, a corona is observed at the edges of leaves where
> the charge on the leaves leaks off into the surrounding atmosphere.

Sigh.  While I like seeing this kind of serious entry, this one immediately
raised a red flag.  Sharp points do indeed increase field gradients, and this
in combination with quantum tunneling permits very sharp points to release
electrons from room temperature cathodes.

However, there is an entire mini-electronics-industry in the process of
forming around this very effect, mainly because thin-film diamonds happen to
be very good at releasing elecrons from such sharp points.  In the not-to-far
future you are likely to see extremely tiny true vacuum tubes being made with
this effect, since to this day there are things you can do with triods that
you just cannot achieve very easily with true solid state devices.

In short, there is a _lot_ of literature on the subject of the field emission
effect.  I recall field-effect microscopes from back in my childhood days, and
quantification of the effect mathematically extends well before that, I'm sure.

The thing to remember about these field emission effects is that while they
do permit electrons to stream off in a decidedly non-classical fashion from
a cold needle, the total acceleration provided by the effect is no higher
than it would be for the same voltage differential without the sharp points.

Why?  Because the region of extremely high field gradient is also very, very
short.  It has to be -- a voltage difference is a voltage difference is a
voltage difference, and if you "use up" most of the gradient in a very short
distance, the rest of the gradient will just be very shallow.  E.g.:

        +5V -  _                            +5V ---------------
                  -  _                                         \
                        -  _                                    \
                              - 0V                               \ 0V

The curve to the right ends with a whopper of a voltage gradient, but just as
a rock released on either of the gravitational equivalent of these two slopes
would still hit with (ideally) exactly the same energy at the end of the slope,
the final energy of the electron will be determined only by the difference
in height (volage), not by how steeply the voltage changes in some regions.

I have not read through the article in detail, and so will of course cannot
say for sure how I will react to their arguments.  But I am very, very sure
that field gradients due to physically sharp points do not produce phenomenally
high final accelerations _unless_ a very large voltage difference already
exists -- which would make the whole issue rather moot, since no one denies
that very high voltages can accelerate ions to very high speeds.

Additionally, there are some quantum issues that cannot be ignored.  Even the
intial "acceleration" of the electron in a field effect needle is not really
a traditional acceleration, but a type of tunneling -- the electron more-or-
less "loses itself" for a brief time and finds itself suddenly on the wrong
side of an "impassible" energy barrier at the surface of the metal.  It then
moseys on out at a rather modest acceleration and final velocity.

At any rate, best of luck to the authors and I hope they will continue to
work on this one.  But I would strongly recommend a detailed search of the
literature on the field emmission effect and "cold cathode" electronics.

(And by the way, one of the reasons I'm a bit adamant is that I followed
pretty much this same path about two years ago and eventually abandoned it
when I realized that I had been confusing some of the issues of field
gradients and voltage differences.  It's very interesting stuff, at any
rate, and well worth a closer look by anyone interested in oddball solid
state effects.)

				Cheers,
				Terry