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: More bad news for fusors
Date: Jul 18, 5:47 am
Poster: Mark Harriss

On Jul 18, 5:47 am, Mark Harriss wrote:

>In a thesis written by Dr. Todd Rider entitled "Fundamental Limitations on Plasma Fusion Systems Not in Thermodynamic Equilibrium" (like in non-Maxwellian plasmas or fusors) he points out that even if fusors can overcome all other losses, ion collisions, electron losses and so fourth there is an even larger loss mechanism that they may not be able to solve, and that is Bremsstrahlung losses.
>To me it makes sense that this would be a larger loss mechanism in a fusor than in a Tokamac, because Bremsstrahlung is electromagnetic radiation that occurs when electrons are decelerated over a very short distance. This obviously applies to fusors.
>According to the paper, losses in non-Maxwellian plasmas are much larger than in Maxwellian plasmas and the losses are especially high in advanced fuel cycles such as D-He3 or He3-He3 and especially for the P-B11 fuel cycle, it is looking much worse than the D-He3 cycle.

A Dr Arthur Carlson has an interesting critique of Dr Todd Rider's thesis at http://www.ipp.mpg.de/~Arthur.Carlson/rider.html in which he states:

The first table in the thesis lists the ratio of bremsstrahlung to fusion power for various fuels under the assumption that the only chain of energy transfer is fusion
products to fuel ions to electrons to bremsstrahlung (sometimes referred to as the "hot ion mode") and under the assumption of nearly Maxwellian velocity
distributions. The first assumption is wildly optimistic, the second is examined in detail in the rest of the thesis. What comes out is:

fuel P_brem/P_fus
------- ------------
D-T 0.007
D-He3 0.19
D-D 0.35
He3-He3 1.39
p-B11 1.74
p-Li6 4.81

In other words, D-T has no problem with bremsstrahlung. D-He3 and D-D can in principle overcome bremsstrahlung loss, but they can't afford to lose much on any
other front. The nearly aneutronic fuels are not merely more difficult, but are impossible, unless you can find a very large loophole.

Well, maybe the assumption of Maxwellian distributions was too severe.

I'm selectively quoting Dr Carlson but he states that there is no real bremsstrahlung problem with D-T reactions. NOW! where do i get some tritium??.