Reply To: minimal size device for focus fusion to work?

[zapkitty]

delt0r wrote: Not what i was talking about. The reaction is p+11B-> 12C* -> 8Be*+alpha -> 3alpha +gamma. These gammas are below the 7MeV range IIRC. These gammas are quite rare (not that rare however, it is why the energy distribution of the resultant alphas are the way they are) but that does not change the fact that even .1W of gammas is a *lot*, and you are talking about 60MW or more, so even these quite small background levels are still on the order of kW and then you need a lot of shield to get than down to levels that are safe for humans to not worry about. Even the low level of background neutrons will matter at these power levels for something that is suppose to be flight weight.

The problem is that 1W out of 60MW is only much less than 1ppm, but still very bad for human health, and gammas are really hard to stop.

I am not claiming they are hard to deal with generally. I am claiming they are hard to deal with for something that needs to be flight weight. Power density in aircraft is critical.

… this would seem to somewhat contradict the “less than background” that Lerner speaks of so it would be good to have clarification and details. An overly excited 8Be decays into 2 alphas and a gamma?

The neutrons are also supposed to be less than background which would make an FF unit a bit of a neutron sink… but massing the units would increase the neutron count?