[cromwellian]

Which tech isn't ready? The plasma behavior for that volume was already shown by JET @ 1.5 bar. MIT Alcator C-Mod which achieved a record 2-bar pressure that won't be beaten by ITER for 15 years. Arc also predicts a 2-bar pressure plasma. The difference is, they did it with non-superconducting magnets (copper), and paid a huge price in losses due to resistance. Arc's HTS magnets won't suffer the same problem, will have triple the field strength, and will be structurally stronger.

Arc is doing what JET and Alcator C-Mod did (with a radius very similar to JET), just with a much more power efficient confinement system, so the input power is lower, and the magnetic field is a factor of 2.6 stronger. The basic physics show that stronger fields actually make the plasma more well behaved, not less, so the major variable vs JET (a proven existing tokamak with Q=0.67) that's changing is not likely to lead to surprising results.