Reply To: X-Rays from Focus Fusion

[Aeronaut]

jamesr wrote:

Cool deal. What would the outlook look like if you were to begin with each core thinking it was measuring and projecting the weather for 960 towns, villages, crossroads, etc? Iow, we have a much smaller plasma, so we can map it more precisely.

The smaller plasma does not make it simpler. The small scale, and high density just mean the grid size & time-step for the simulation are smaller – although not quite as bad as the situation in inertial confinement fusion.

Our little cluster is tiny really – I can only model 3D grids of a few hundred points on each side, maybe a billion gridpoints for a few tens of thousands of timesteps. To model the focus of a DPF device would take much more.

My code, as do most parallel codes of this sort, works by domain-decomposition – each processor handles a small local region, say 64x64x64 grid points then exchanges the field values, densities, velocities etc at the each edge with the relevant neighbouring processor each timestep. This should in theory scale well, that is it efficiently makes use of all the processors as you run it across more & more of them.
Then I may be able to run it on the UK’s larger academic supercomputer called Hector which has 22656 cpu cores, and is currently No.20 in the top500
The Met Office’s weather modeling computer is down at No.89 in the list. All these are still small in comparison to the DOE/NNSA/LANL or Oak Ridge’s computing facilities.

If FF-1 achieves its goals then it is this scale of computer that we will want to run detailed simulations on. However well the experiments go, these days in order to manufacture any nuclear device they must be simulated to prove the physics is well understood, and dosage/shielding calculations need to be done to design the required containment (however small the dose may be).

Wow. Didn’t realize the how many processors would be needed, or how big the arrays could be. Are you assuming a combination of top-down and bottom-up prediction as the variables are developed? How long do you guesstimate a simushot would take on the Met Office’s size array? and for comparison, on the ORNL’s array? Dang I’m full of questions today!

Excellent point about the simulations and experimental confirmations of them being required for manufacturing. I should have seen that coming. And that’s just for straight pB-11 fill gasses. But I imagine it’s going to need simulations for almost any gas if it’s going to be widely distributed.