Reply To: Military Effects

[asymmetric_implosion]

Lerner: You don’t need 10 people to design a switch that already exists. (http://www.amazing1.com/sparkgap.htm) Scroll to the bottom. Look at Rail gap. Typically a 16 week lead. Switch N2 to Ar-O2 (10%) as listed by Maxwell pulse power and you get a 75 kV, 1 MA switch. This is not the first time I’ve said it and I’m sure John Thompson has mentioned it to you more than once as John introduced me to the switches. You need a ~100 kV trigger to take them down with ~10ns jitter. North Star High Voltage can build it if they have the time. Richard Adler is one of the best if not the best person for the job. I have used North Star triggers at ~40 kV with a jitter of 20-30 ns for years and we have never had a problem that wasn’t our own doing. We run up to ~100 kA per switch for over 10,000 shots without opening the switches for cleaning. I’ve run over 1000 shots without changing the working gas. You should be able to get at least 250 shots without any maintenance. Maintenance is polishing the rails and wiping away any built up deposit. Takes about 1-2 hr per switch at most. (Brian L. Bures, Mahadevan Krishnan and Robert E. Madden “Relationship between Neutron Yield and Macro-scale Pinch Dynamics of a 1.4 kJ Plasma Focus over Hundreds of Pulses” IEEE Trans. Plasma Sci. Vol. 39 No 12 pp 3351-3357 (2011) doi: 10.1109/TPS.2011.2170588)

If you don’t like the Rail gap, look for the MMCS switch the French use on the Sphinx machine (50-100 kV, 1 MA). Sandia uses laser triggered spark gaps with 1 ns jitter so there is always that option if you want to spend the money for four of those.

You speak of the black art of pulse power and I agree to a point. I am no pulse power expert, more of a dabbler and user, and there are three (really two as Sandia’s switch costs way too much) alternatives that will work without designing a custom switch and are much faster than 20 mon.

Vacuum leaks: Derek is on the right track. Buy an RGA and find the leak with helium. RGA is 4-6 weeks away from SRS if they don’t have one in stock.

Joe: My frustration is that it looks like we will see a 1000 ways to make a PF pulse power system wrong before it is made reliable. There are at least 3 if not more 300-500 kA machines in this country put together on a shoe string budget. One might say that they are not as big but they contain all the key parts to make a 3 MA machine. I know Eric has hardly talked to our group at AASC. I get it; we are a company. I know KSU folks helped build the machine but I don’t know more than that. The UNLV folks used a design by Bruce Freeman, formally of Texas A&M, now with Raytheon (probably designing the new switches). Bruce operated a 2 MA PF at A&M for years and I’m sure he didn’t have these problems. NsTec has a 3 MA PF and I’m pretty sure they don’t have these problems. There are always the folks at NTU/Singapore, DENA or Pavel Kubes. There are a number of folks in the US and around the world that have solved these problems and moved on to study the physics. The PF community is very open to new members and very willing to help whether it is physics, pulse power or components. Great in roads have been made between LPP and physicists around the world (Iran, UK) but why are they not seeking help from an expert in pulse power that would visit and clean up the pulse power problems? This is my concern for LPP in more detail.

I really appreciate the small group as the AASC group is only 4-5 and I know the struggles. The key for us was to bring in folks that were experts as consultants at the right time. We let them solve the problem and tell us to become users and more slowly advanced users. We will never replace these experts in skill but we learned to stand on our own. When we trip, we run back to them asking for more help. We had a good team in place and we still had to talk to experts to keep moving forward. I can tell you that it never took the experts more than a few weeks to identify a problem and propose a fix whether it was a switch, transmission line or machining problem. The parts can take a while but more than a few months seems unreasonable.