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Comment by sdeyerle | Hacker News Reader

In the original proposal for the ARC reactor, they were proposing making the magnet separable so the top and bottom of the reactor could be separated and the vacuum vessel removed. (See pg. 5 of https://library.psfc.mit.edu/catalog/reports/2010/15ja/15ja0...)

It doesn't look like they are targeting that here. Does anyone know if that is ARC (not SPARC) specific, or if that has been abandoned?

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The demountable magnets for ARC are so the blanket and vacuum vessel can be swapped out as a whole unit for replacement during maintenance. SPARC has no blanket and will only be used for some thousands of ten second shots or the equivalent of a week or two of continuous operation. The magnets being unshielded will probably fail before the vacuum vessel does.

CFS will be building a lot more magnets, not only for SPARC but for other customers, physics experiments and medical equipment, so I expect they will be working on many additional features including demountable joints for ARC.

One of the early tests they did of the VIPER cable at the SULTAN test facility in Switzerland involved a joint formed by clamping the ends of two cables to a copper bar. It does show that resistive joints are possible with HTS cables, unlike LTS cables, but the actual configuration of a joint for a large magnet is obviously a different matter. Luckily they will have a few years to work on it.

The article says this is from an "MIT-CFS collaboration" which is "on track to build the world’s first fusion device that can create and confine a plasma that produces more energy than it consumes. That demonstration device, called SPARC, is targeted for completion in 2025."

So, sounds like it's for SPARC.

Yeah, they are definitely building SPARC. I had just been under the impression they were trying to do the separable magnets in SPARC, and was curious if I misunderstood their plan or if their plan had changed.

Yeah--I misread your question. :)

I think that's ARC-specific. SPARC is a prototyping platform, they aren't designing it for long term use or to be refurbished.

Since there is no actual use planned for any power released in this gadget, no maintenance will be performed. When they finish playing, they scrap it, pocket the money, and go their separate ways.

No commercial reactor will ever be built, so this is just for showing off.

The only real good to come from these efforts is employment of plasma fluid physicists. I just hope non-military work can be found for them when this stuff fizzles. Solar Physics is fascinating and important, but has limited budget.

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