mheslep said:
Per wiki, Lockheed's design is a magnetic mirror concept, which is decades old. No IEC. The high beta aspect appears new, as is the small rector size.
I'm not sure if Lockheed's design is a pure magnetic mirror or if it's a magnetic mirror IEC hybrid. Skunk Works is intentionally vague in many of the details surrounding their device. Skunk Works is a secretive branch of Lockheed Martin, so this isn't really that surprising. In my experience they have been particularly secretive on their intent to use a virtual cathode or not to. The wikipedia article doesn't really tell you enough to figure out if Lockheed Martin's design is a cusp confinement concept with a virtual cathode (making it IEC) or a cusp confinement concept without a virtual cathode (not IEC).
I suspect that they plan to use a virtual cathode based on the following:
Dr. T McGuire's , the lead scientist on the Lockheed Reactor, background is in IEC.
Arguably the most promising IEC devices use a virtual cathode. All devices that use a virtual cathode need some way to confine the cathode to it's center. Cusp magnetic field configurations have traditionally been used to this end (the Polywell for example). For this reason cusps are popular in the IEC community.
The cusp as a pure magnetic confinement concept has a number of flaws related to end losses. You need to address these flaws in order for it to be a viable fusion reactor.
I argue that if someone with a background in IEC is proposing a reactor that uses cusp confinement, then there is a good chance that they are going to use a virtual cathode unless they specifically say otherwise. Of course this isn't proof. Do you know of any instance where they have directly addressed this question? If so I'd be interested to hear what they said.
High beta is a reference to a theory by Harold Grad that dates back to the early days of fusion research. The theory suggests that the confinement of a cusp should improve at high beta. It's certainly not a new idea, and it is not unique to the Lockheed's design. The Polywell will also benefit from this effect. In fact the improved confinement was recently observed on a Polywell.
Sorry, this is one of my peeves. The small reactor size idea also isn't new. Almost everyone in the fusion community recognizes the benefits that a small reactor would provide. However, there really isn't any data that suggests Lockheed Martin's design will achieve that goal, and there is decades of research into a variety of different concepts that suggests that it is a lot harder to build a compact fusion reactor than advertised. Lockheed isn't the only ones considering a small reactor concept. Many of the venture capital funded firms are promoting some sort of small reactor design. As a fusion scientist I wish them all luck, and I think it's good that they're trying out some alternative concepts. But the models that these "small" reactor designs are based on ignore turbulence. Turbulence is the dominate transport mechanism in every mature magnetic confinement concept to date. If it wasn't for turbulence we would have likely solved fusion decadesago. Turbulence is the reason why we can't build a small tokamak reactor with existing technology. If you want to make a compelling argument that a small reactor can ignite, then you need a realistic turbulence model.
