Reply To: Repowering the electric utility industry

[asymmetric_implosion]

Joe:

Hybrid Mmagnets (Combination of superconducting magnets and normal magnets) hold records of 100 T or 1E6 Gauss in a pulse mode. Pulse current drivers like the plasma focus and Z-pinch are one of the few methods to produce such strong fields in a somewhat controlled way. Other methods are explosively driven like nuclear detonations. Annually, a meeting is held on Megagauss fields which are common in the Z-pinch community using 1 MA to 24 MA drivers to report results on 1E7 and 1E8 Gauss experiments. The reproducible demonstration of Gigagauss fields had yet to be shown. The Focus Fusion concept argues they are necessary but making a measurement of these fields directly is very challenging. Diagnostics are only now becoming available to do what is needed and they require very specific axillary facilities that are likely to exceed the cost of FoFu-1. It is likely that Gigagauss fields will be inferred from another measurement before directly measured. The problem with measurement by inference is the interpretation. Someone sees a plasmoid while others see a Rayleigh-Taylor neck or so called hot spots. To achieve a Gigagauss field using a 1 MA drive pulse, you need a pinch diameter of ~2 microns. Typical observed pinch diameter are more like 5 millimeters. The problem is more complex than this simple calculation but features less than 10 microns are required to achieve such a high field unless you are using other techniques like flux compression.

Dave:

Black body losses are not that significant in a deuterium plasma because most of the electrons are unbound leading so-called free-free radiation instead of free-bound radiation. Free-bound transitions are more frequent and generally more potent because you can excite a bound electron leading to a photon emission to return to ground. It can be rapidly excited again. In the free-free mode, you need specific interactions to generate radiation. Also, deuterium plasma is optically thin. Remind your engineer friends that a black body is the most efficient emitter of radiation at a given temperature which means it takes the most power to sustain a black body at a given temperature. Gray body and white bodies (optically thin bodies) are much easier to heat to high temperature given a fixed power input. Emissivity for plasma can be quite low or large depending upon the conditions of interest. This is a complex matter is plasma physics requiring very complex diagnostics and very intricate numerical simulations.

I would add to Jamesr’s comment about brems. Brems emission is typically related to electron temperature or energy. In pinch devices, the electron temperature is naturally lower than the ion temperature. It is commonly reported in published literature since 1958. Pinch plasma is one of the few plasma types to have hotter ions than electrons. That is a huge advantage to accessing p+11B fuel. If you can further suppress the electron temperature or increase the ion temperature using strong magnetic fields, you can benefit further.