I feel like worrying about the cost/efficiency of the heat engine of a fusion device at this stage is putting the cart before the horse. 40% efficiency is reall

I feel like worrying about the cost/efficiency of the heat engine of a fusion device at this stage is putting the cart before the horse. 40% efficiency is really good when the reactants are practically free. IMO the reason that HB11 may actually succeed is that the reaction keeps most of the output energy in charged particles in the plasma, so it's more feasible to achieve true ignition than when neutrons carry most of the output energy away from the plasma.