Reply To: X-Rays from Focus Fusion

[jamesr]

Although twisting a rubber band and seeing it twist and kink may help figuratively in picturing what is going on, it can be misleading to think that the behaviour of plasmas are that similar.

A rubber band has a fixed topology – it cannot split into separate strands or merge back together. One of the key aspects of plasma instabilities is precisely that ability to filament, form ‘magnetic islands’ and reconnect. The transfer of energy to the plasma from the magnetic field and vice versa is intimately linked to the reconnection rate & changing topology of the field.

Only through simple idealized simulations like these:
– two-stream instability
– Double tearing mode plus a shear instability.
– 3-D evolution of Kelvin-Helmholtz instability
or full device models like this:
– DIII-D tokamak simulation

What we need is for the plasma focus device simulations that Eric Lerner and others are working on to mature to the level of some of the codes the tokamak or inertial confinement fusion communities now have at their disposal. This is what is going to take lots of funding in the years ahead.

The 1D & 2D plasma focus codes around now may be sufficient to characterize the first few phases of a DPF pulse, and separate codes could start modeling the properties believed to exist in the small plasmoid. Currently no one program can model a DPF as a whole.

A fully 3D program to model plasma focus devices that can cope with the vastly different time and space scales involved (even if written as separate modules for each phase), would do wonders not only for the science but also the PR point of view. With convincing 3D graphics based on a sound underlying model it will be a lot easier to convince people, rather that the simple artists impressions we have at the moment.