Reply To: Great News!

[asymmetric_implosion]

Anode erosion does not have to be a show stopper. As with any system, go in knowing it could be a problem and design for it. In my case, I didn’t consider e-beam a significant problem as my low rep-rate sources (~0.1 Hz) didn’t have any problems. Operating at 1 Hz all day for 10+ days showed a problem. We pulled an anode after 250,000 shots and found a deep bore hole in the anode that nearly broke out of our vacuum vessel. We thought refractory materials or ceramics would solve the problem. Ceramics were a miserable as they erode into gases and other things that made matters worse. We tried alumina and boron nitride. Refractory metals did a bit better but they were not the knight in shining armor we needed. The real goal should be to spread the e-beam out far from the pinch region (inches if not feet) and let the e-beam impact a specifically designed beam dump that will handle the e-beam. Our experiment does not allow us to do this so we have taken other steps that will work in the short term. Our next move is to implement a more reliable solution like magnetic deflection onto a beam dump. This should give us anode lifetimes that are on the order of our switch lifetime (~1E7 shots). For the purpose of illustration, our current solution is good for 50K to 100K shots. We need 100X increase in materials lifetime to make our source viable.

The LPP source could do better with plasmoid confinement of the e-beam but a switch that operates at 200 Hz for >1E8 shots and high voltage, high current is currently unavailable and again for materials reasons might not be possible. The solid state option is difficult to imagine working well at the 2-3 MA level with 50-100 kV on the bank. It is not impossible but you only get one case to screw up. Solid state will last forever (>1E9 shots if not 1E10 shots) if it is treated right but one bad step and it is done. It is my opinion that the switches will determine the tolerable lifetime for the other components.