Reply To: Great News!

[asymmetric_implosion]

That’s an ambitious list.

The switch upgrade is a great idea. I hope these Raytheon switches are the ones developed for the next gen marx generators and LTDs. If they are, the switches are highly reliable and can hold off far more than 45 kV using only dry air. The data from the LTD tests at 200 kV, 1 Hz were very impressive. I know Raytheon recently purchased K-tech. K-tech was involved with the LTD work at Sandia for the 1 MA LTD modules. Moving up to the theoretical limit of the machine would be interesting.

The nitrogen/deuterium mixing should be interesting. N2 is an interesting gas. It will be an interesting study since most people shy away from heavy diatomic gases in a PF. I’m not a fan of oxygen in my PF. My limited experience with nitrogen was mixed. Some days it ran really well and other it was poor. There was no obvious rhyme or reason to the whims of the machine when we never broke vacuum.

I hope the yield number is wrong…66 kJ per shot with a 5 MW plant means 75 Hz operation…so 100 Hz operation after all is said and done. To my knowledge, one one group has operated a PF >100 kA near the 100 Hz level and it required substantial effort and the yield was well below the optimum with soft x-rays. There are substantial problems moving up in repetition rate. I’m fighting a few right now as we move one of our machines from 1 Hz to 10 Hz. It is not as straightforward as one might believe. A combination of heat, residual ionization, anode erosion and chemistry have hampered our efforts to demonstrate something near the 1 Hz neutron yield at 10 Hz. The anode erosion has been a killer. Our little machine at ~60 kA is eroding anode material at ~10 ug/shot. One might laugh at this value but the beam can be highly focused on a small part of the anode. I’ve bored holes over an inch deep into SS304 anodes. According to e-beam scaling predictions (Stygar 1982), a 1 MA PF will be far worse. If someone is going to say use a ceramic, don’t bother. Ceramics are the devil. The anode base must be metal.

The engineering issues have become far worse than the physics problems with encountered. Repetition rate introduces a set of new problems that a few shots a day will not encounter. Just a heads up in case anyone thinks it will get easier once Q>1 is demonstrated.