Reply To: Where are Japan and China in funding Focus?

[jamesr]

Hi, and welcome to the forum!

Its good to think about novel ways of achieving the Lawson criteria. The trouble is the density, temperature & confinement time product is a very large number. In a spherical compressive model as you propose, the slight asymmetry would introduce Rayleigh-Talyor like instabilities way before the compressive wave could reach the centre. So peak density & temperature would be far lower than needed.

If it were that simple, the spherical imposive method of detonating plutonium bombs, would also work for fusion. To ignite a fusion burn wave at the centre of a spherically compressed volume you need the compression, heating and ignition to occur faster than any of the instabilities have time to develop. The instability grows exponentially in time, but is proportional to the size of the initial perturbation. Or in other words your large sphere being driven at the outside would have generate a spherical wavefront perfect to less than one atom width.

By increasing the size of the sphere to increase the ratio of driving oscillation to proposed peak oscillation in the centre, the wave takes longer to reach the centre and so reduces the tollerence on the sphereical accuracy. The exponential growth of the instablilty will always be faster then the cubic growth in geometric scaling.

On the other hand if by some miracle you could get it to work – having that much fusionable fuel in a sphere would make a very big bomb. The few mm size of the pellets, in a 10m radius vacuum chamber used in devices like NIF to a large extent due to the limited load the walls could take when it detonates. If as in your case the rest of the volume was full of ‘fuel’ then you would blow up the city!