Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Cylindrical IEC
Date: Jan 06, 12:31 pm
Poster: Blair Bromley

On Jan 06, 12:31 pm, Blair Bromley wrote:

>>The Farnsworth team had several test units for this concept rather late in their game after 1964. I have several photos of one in particular where the cylindrical inner grid looked like a sausage about 6" long. The whole thing was in a large (12"??) conflat nipple.
>It is unclear from the papers that I have what the real configuration is (they've written a raft of theoretical papers with designs for power producing cylindrical IEC units, but the dimensions are huge). From some of the papers, it seems that the cylinder is short and squat (that is, the length of the cylinder is quite small relative to the diameter. Not much mention is made of the ends of the cylinder (does the grid just end, or is it sloped, rounded, attached to the end wall of the chamber, etc?)
>Which Miley paper actually gives experimental neutron counts from a cylinderical geometry? Most of the ones I've seen give measurements from a variety of spherical geometries.
>Of course, perhaps they are just being cagey with a potentially profitable development, and only publishing enough to establish priority?

Well, since I am doing my doctoral thesis on the computational modeling / simulation of a variant of the cylindrical IEC device, I suppose I can give a few comments on this.

Understanding the physics of this device is difficult, just as it is difficult to understand the spherical IEC device.

I can tell you (and it is documented in my master's thesis as well), that the maximum neutron output obtained from one version of the cylindrical IEC device was on the order of
2.0e+5 n/s, at voltage of about 30 kV, and a
measured electrode current of about 40 mA. The operating pressure was on the order of 1 milliTorr
of deuterium. It is possible that one could obtain much higher rates by boosting both the
operating voltage and the current. One could
also make changes with electrode geometry,
sizing, and spacing to help improve the confinement of fusion fuel ions.

To call the U of I device a "cylindrical" IEC device is somewhat misleading. I prefer to call it an axial-cylindrical IEC device because
there are a number of cylindrical hollow ring
electrodes that are spaced axially apart and
biased at different voltages. It is thought
that the primary direction of particle acceleration is axial, not radial.
At the U of I, we have tested two types of
the axial-cylindrical IEC device. The first
one was simply a single hollow cylindrical
metal cathode biased to about -30 kV, and spaced
equidistant on either of the cathode was a
grounded cylindrical plate, which we referred as
the reflector. Ions were accelerated axially
towards the hollow cathode and oscillated back
and forth until they we lost to the electrode, or
were implanted on the glass wall of the vacuum chamber. The second variant of the axial cylindrical device, which was used for the experimental data that I am using as a benchmark in my computational simulation model, has two
extra hollow cylindrical ring electrodes. There is a central hollow cathode biased to ground, then
a hollow cylindrical anode placed on either side of the cathode at some distance away, and these
are biased at some high voltage (10-100 kV) Finally, there are reflectors placed at some distance away on either side of the hollow anodes, and these are biased to ground. The reflectors
"reflect" electrons, and ideally create an
ionization zone about the anodes. The central
cathode and the region between the central cathode
and the anodes is where most of the fusion reactions are expected to occur.

Much more can be done to investigate this variant of the IEC device, both experimentally and theoretically. I have opted to pursue theoretical studies.

The cylindrical IEC device that most people probably are thinking about is what I call the radial-cylindrical IEC device. Concentric transparent electrodes are biased at different voltages, causing particle acceleration to be primarily in the radial direction. Several experiments were done in the early 1970's by
researchers at the Gaseous Electronics Laboratory here at the University of Illinois using the radial-cylindrical IEC configuration.

Here's an easily obtained reference on the first
variant of the axial-cylindrical IEC device, with
some experimental data:

Gu, Y., J.B. Javedani, J.B., and Miley, G.H., "A Portable Cylindrical Electrostatic-
Fusion Device for Neutronic Tomography," Fusion Technology., Volume 26,
Number 3, Part 2, 929-932 (1994).

Best Regards,