Fusion
Science
7 rabbit holes · 6 people exploring
Common starting questions
- Why does magnet strength matter so much for fusion?
- How does the sun manage fusion at only ~15 million degrees?
- What actually happened with cold fusion?
- Did we actually get more energy out of fusion than we put in?
Rabbit holes
- stellarators look like someone crumpled a donut on purpose
A tokamak gets the twist in its magnetic field partly by driving a huge current through the plasma, which can go unstable. A stellarator gets it entirely from the shape of the coils, which is why they look insane. Spitzer came up with it at Princeton in 1951 and it lost to the tokamak for decades, partly because nobody could build coils that precise.
Dev Malhotra · 6 sources
- people build working fusion reactors in their garages
A fusor is basically a spherical grid inside a vacuum chamber with a bit of deuterium and tens of kilovolts. It genuinely fuses atoms and you can detect the neutrons. It also uses vastly more power than it makes, which is fine because the point is doing it. Among hobbyists, detecting neutrons is the bar for having actually done it.
Kate Lindqvist · 6 sources
- why fusion people got excited about superconducting tape
Tokamak performance climbs very steeply with magnetic field strength. Tape made from REBCO superconductors allows much stronger magnets that also run warmer, so in theory a tokamak a fraction of ITER's size could do a similar job.
Maya Rivers · 6 sources
- the sun's core makes less heat per cubic meter than a compost heap
The core produces apparently a few hundred watts per cubic meter, roughly like a compost pile or a lizard's metabolism. The sun is bright because it is unimaginably big, not because each bit is intense.
Arash Mohammadi · 6 sources
- in 1969 British scientists took a laser to Moscow to check a Soviet fusion claim
The Soviets reported tokamak temperatures that Western physicists didn't believe. So a team from Culham brought their own laser diagnostic to the Kurchatov Institute, in the middle of the Cold War, and confirmed it. After that basically everyone started building tokamaks.
Daniela Ruiz · 6 sources
- cold fusion: the 1989 press conference
Two respected electrochemists announced at a press conference that they'd gotten fusion in a cell of heavy water with a palladium electrode. Labs everywhere tried to replicate it within weeks and mostly couldn't, and the neutrons you'd expect from that much fusion weren't there.
Yuki Tanabe · 6 sources
- what 'fusion ignition' at NIF actually meant
Dev Malhotra · 6 sources