Stellarator Performance Improved with Boron Addition

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Dennis P Brown
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Stellarator Performance Improved with Boron Addition

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So it looks like an issue for stellarators - the problem of too great of a temperature gradient across the plasma - can be significantly reduced by adding a small amount of boron to the plasma. This apparently improves containment - a rather important effect, you'd think for these devices. Stellarators are, unlike tokamak's, far more stable and not anywhere near as prone to magnetic field disruption/failure. So this is an interesting development since stellarators look more promising than tokamaks. Strange (but maybe not surprising - they are physicist) that this development is only now being explored - apparently this element has been used in tokamaks for some time to address similar issues. Maybe these two groups might - in the interest of not being totally stupid - read each other's papers (as a desperate last resort, maybe) and determine if they offer insights to their own plasma issues.

See: https://phys.org/news/2022-01-common-ho ... ffort.html
Richard Hester
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Re: Stellarator Performance Improved with Boron Addition

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The boron treatment serves to coat the containment vessel walls with a low-Z material to reduce high-Z impurities in the plasma. I ran into a paper a few years back describing the procedure for coating Alcator's containment vessel using diborane. It was somewhat hair-raising reading, describing the use of full containment breathing gear to handle poisonous and pyrophoric diborane. Diborane is usually provided win diluted form (H2 or He) to counter its tendency to polymerize.
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Nicolas Krause
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Re: Stellarator Performance Improved with Boron Addition

Post by Nicolas Krause »

That's very interesting Dennis, is that a common property of plasma's with boron in them? That they have a smaller temperature delta across the plasma? Or is that specific to stellarators?
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Dennis P Brown
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Re: Stellarator Performance Improved with Boron Addition

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Not up at all on the plasma physics anymore but current stellarator's (like the W-7X) are highly stable* - unlike tokamak's - and anything that improves their performance is certainly a plus. Once someone is crazy enough ... I mean dedicated enough to ever try burning tritium and deuterium in a stellarator for power, the very last concern they'd have is toxic issues from boron. But of course, no such issue exists for the foreseeable future so that toxic aspect would certainly be a problem for most facilities. Interesting the Japanese went ahead and did this experiment. They'll need to do a lot to catch up with the Germans with their Wendelstein 7-X.

* A relative term; only appropriate when comparing to a tokamak or mirror machine
John Futter
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Re: Stellarator Performance Improved with Boron Addition

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Boron is not toxic to humans
it is to insects hence boric treatment of timber
we use it in our washing machines --Borax

I think you are confusing with beryllium which is very toxic to humans
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Joe Gayo
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Re: Stellarator Performance Improved with Boron Addition

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They use diborane to treat tokamaks and stellarators to deposit a thin coating of boron and diborane is very toxic - https://pure.mpg.de/rest/items/item_321 ... 43/content
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Re: Stellarator Performance Improved with Boron Addition

Post by John Futter »

Joe
yes nealy all hydrides are poisonous due to their reaction capability
DiBorane silane etc are spectacularly prorophoric.
My problem was with the startement "Toxic issues from Boron"
in the end you get native Boron deposited
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Dennis P Brown
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Re: Stellarator Performance Improved with Boron Addition

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Turns out they used simple boron and ionized it for the plasma.
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Re: Stellarator Performance Improved with Boron Addition

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That would make a great deal of sense from a safety point of view
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Re: Stellarator Performance Improved with Boron Addition

Post by Richard Hester »

If I ever tried to inject boron into a plasma, I would use a laser to vaporize little dings off of a boron target. I gave up on ever wanting to use boron hydrides a long time ago, as their poisonous and pyrophoric tendencies make them spectacularly poor house guests.
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Dennis P Brown
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Re: Stellarator Performance Improved with Boron Addition

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As a totally irrelevant point but related to those boron materials - I believe the XB-70 Valkyrie super sonic high altitude strategic bomber used a boron based fuel. And yes, the fuel was extremely toxic and dangerous.
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Re: Stellarator Performance Improved with Boron Addition

Post by John Futter »

No problem making targets for implantation out of native Boron powder (brown in Colour)
Using a sputter ion source no problem getting a 1-2mA boron beam on target
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