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: Current scaling in fusor III
Date: Apr 16, 8:04 am
Poster: IJV

On Apr 16, 8:04 am, IJV wrote:

I pulled out that paper I mentioned and read it again, its:

Innovative Technology for and Inertial Electrostatic Confinement Fusion Propulsion Unit.
G.H Miley et al
paper 94-3321 30th AIAA/ASME/SAE/ASEE Joint Propulsion Conference 1994

Interestingly enough their experimental setup was different enough from yours as to make a comparison highly problematic.

The main features of their setup was

1. They were running in pulse mode
2. Voltage was held steady at 10 & 15 kV
3. ~10ms current pulses were used at up to 200mA
4. They are also in the glow discharge regime and a 5-20mA sustaining current was used between pulses

Other things of note are

1. At 10 kV neutron count varies with I^2
2. At 15 kV neutron count varies with I^1.3, but overall neutron counts are higher.

3. Their explanation for this is that at lower voltages, the ions spend more time in the central fusion region.

4. With steady state conditions they report ~10^6 neutrons/sec (D-D reaction), the current and voltage was not mentioned tho.

5. Their models predict that higher current scaling laws should start to kick in at about the 1A region for D-He3. The pulsed experiments were done with deuterium if I understood the paper correctly.

Does anyone know of what if any progress they have made since then?


>>This is a for Richard Hull mainly.
>>Have you gained enough experience with fusor III to form an idea of how the fusion reaction rate (as given by the neutron count) scales with current?.
>Superb question!
>Interestingly enough, at the low levels of voltage I have used it scales strictly with voltage! I am so low on the curve (cross section) that volts are power and not current. (bad engineering speak, but good logic speak.) The glow mode is so non-linear and I am working so close to the ragged edge that the current hangs in the 5-10ma region only and never drifts higher without threatening the grid. At 20 ma the tantalum grid is near incandesence! the neutron rate doesn't increase all that much as the resistor limited supply voltage dips accordingly.
>Miley, et al, published results on the nearly linear scaling of fusion rate with current is, I am sure, correct. The entire fusor should behave better if one can get out of the simple fusor's non-linear glow mode region. This is an advantage sought in my Hirsch-Meeks, fusor IV nearing completion. Still, the learning with fusors I, II, and III in this tossing deck region of plasma physics is of incalculable value for, as Mark Twain said "I have not let my schooling get in the way of my understanding". RH
>>I remember reading a paper by Miley a few years ago that predicted that the reaction rate should vary non-linearly with current. Starting off linear and then switching to I^2 and then to I^3, I^4 etc as the current was increased.
>I too have read this, but this was an older paper, I believe. (94?) I would have to see that or have hard data in hand to believe it. I haven't been there yet. As my pal Tom Ligon says, the total envelope just has not been fully explored yet.
>I am seeing voltage scaling as I am still on the steep part of the cross section curve. (it is probably power scaling, more likely)
>I really believe that what I am doing is sort acting as a human servo mechanism with inate and often unconcious understanding to limit the POWER to the grid by sacrificing current or lowering the pressure as the voltage crawls upward. by doing this in this narrow zone, I am seeing a voltage scaled fusion rate increase. It is so easy to draw the wrong conclusions with multiple variables moving about in a totally non-linear process.
>Good science would demand freezing all but one variable and making statements based on data taken, but that so codifies and restricts a system, it says nothing about WHOLE system dynamics.
>If you ever get there, or here, you will understand the richness and damning nature of this beast.
>Richard Hull