jamesr wrote: Given that the bulk plasma in the device should not cool between each pulse below ~800C or so, you could just extend the helium gas cooling needed for the anode to the rest of the walls (making them out of something like tungsten), and run it through a brayton cycle turbine.

But as has been said before it would be much better to avoid having to use a thermal cycle and just extract even just 10-15% directly from the xrays to push over the Q=1 and dump the rest as waste heat.

asymmetric_implosion: The 500kV pinch voltage does not relate to the energy of the x-rays. The x-ray energy peak from bremsstrahlung is a function of electron temperature (http://en.wikipedia.org/wiki/File:Bremsstrahlung_power2.svg ). If the electrons are at ~150keV then the bremsstrahlung peak will be around a quarter of this – so around 30-40keV.

Brems in the plasma might agree with a thermal spectrum if the electrons remain confined in the plasmoid but brems from the electron beam will not obey a thermal spectrum. The run away electron beam that impacts the anode is much higher energy. It hast to be to escape the B-field. Literature from as early as 1977 (Krompholz et al Appl Phys 13, 29-35, 1977) has verified this. The mean e-beam energy is near the pinch voltage with electron energies up to 1 MeV in ~100 kA machines. It gets worse as you go up in pinch current. If the electron beam remains the dominant x-ray sources the brems spectrum will be harder than the thermal spectrum prediction requiring a thicker onion. I’ve been fighting this particularly vexing problem of the hard x-ray spectrum for a couple years because it complicates my application for the plasma focus.

If the x-ray emission is dominated by the plasmoid emission, most of the x-rays will be lost in the vacuum spool before the onion if they are separate pieces. Based upon LPP’s recent release of copious x-ray above 100 keV it seems that the beam is still king as 30-40 keV x-ray would have been significantly attenuated by the copper filters. It seems pretty reasonable for a 1 MA pinch that the mean x-ray energy is near 250 keV (typical pinch impedance is 0.25 Ohm with ~ 1MA so 250 kV). To my knowledge LPP doesn’t measure the voltage during the pulse outside vacuum. Pinch voltage is hard to back out without both the current and voltage outside vacuum. Published techniques exist to calculate the pinch voltage if the data is taken. You can use models to estimate the pinch voltage if you wish but I’ve always preferred a maximum data, minimum model approach.