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treefor_js t1_iyvuhla wrote

Reply to comment by [deleted] in Why not use hydrogen and deuterium in fusion reaction rather than tritium and deuterium? by Curious_user4445

This is not correct. Temperature is a measurement of the average kinetic energy of the particles - you express plasma temperature in units of eV (energy unit). If one element is heavier then it'll have a slower average velocity. DT reactions require lower temperatures to achieve their highest cross section for fusion reactions. Meaning you need to put less energy into the system.

  • HEDP plasma physicist
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ChipotleMayoFusion t1_iyw8hte wrote

Isn't that exactly what Robus said? The DT reaction is favorable because it reaches high reactivity at lower temperatures. https://upload.wikimedia.org/wikipedia/commons/thumb/d/d0/Fusion_rxnrate.svg/330px-Fusion_rxnrate.svg.png

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treefor_js t1_iyw9ick wrote

That was the conclusion, yes. However, the reasoning was not correct.

Edit: the other thing to note here is not just that it takes a lower temperature to reach higher reaction cross sections but the loss mechanisms that scale with temperature as well. It's a balancing act to keep the plasma warm to use the fusion products to keep burning the fuel without it cooling off rapidly. Bremsstrahlung radiation - x-rays generated by accelerated charged particles, is the main culprit here.

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ChipotleMayoFusion t1_iywmfex wrote

Ok, thanks for the clarification. Maybe I misunderstood what his post was getting at. I have heard that proton-Boron is basically impossible because the brems losses at the temperature where reactivity is sufficient will always be higher, or almost always higher. I think this is what you are saying, you can't just focus on the temperature. Sam Wurzel had a great talk on this at APS 2021, clarifying Qeng vs Qsci and how that changes depending on your recirculating power fraction and other factors.

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treefor_js t1_iywn305 wrote

Oh nice. I didn't get a chance to go to that one. Came down with a stomach bug for a day or two in Pittsburgh. Also wish I had time to go to the commercial fusion breakout this year, but alas. There's always next year.

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ChipotleMayoFusion t1_iywnxfg wrote

I'm glad you were able to attend at all, a lot of the US national labs people were not there due to COVID travel rules.

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treefor_js t1_iywoopg wrote

I sat in on one of the MagLIF sessions and I think there was one live talk with like 10 recorded ones. It was a weird conference. Basically just networked with university folks. So much better turn out this year with national lab folks returning.

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