Department of Homeland Security funding
Posted: 19 October 2012 01:03 AM   [ Ignore ]
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I just read an interesting article:   Application of an impedance matching transformer to a plasma focus.   They claim lower costs on consumable parts and lower operating voltages for this small device.  I don’t know how it works out for bigger units.
The Department of Homeland Security funded part of this study.  Is this funding an option for LPP?

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Posted: 19 October 2012 05:45 AM   [ Ignore ]   [ # 1 ]
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That article requires a login, but it’s also available at the following location, which doesn’t need a login:
http://rsi.aip.org/resource/1/rsinak/v82/i10/p103506_s1?bypassSSO=1

Or direct download of PDF:
http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=RSINAK000082000010103506000001&idtype=cvips&doi=10.1063/1.3648117&prog=normal&bypassSSO=1

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Posted: 19 October 2012 07:48 AM   [ Ignore ]   [ # 2 ]
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I always wondered, whether a transformer would be a good idea.

 

So for example an 6-times step-down transformer as used in the paper would yield 4000-times increase of neutron yield with the same input power:

U_effective = U_input / 6
I_effective = 6 * I_input
P_input = U_input * I_input = U_effective * I_effective
N_n = const * I_effective ^ 4.7 = const * (6 * I_input) ^ 4.7 = const * 4542 * I_input ^ 4.7

But then I know that one of the goals is to reduce inductance (read it somewhere in Eric’s early papers on arXiv), to enable fast rise-time of the current, which seems to be crucial. I always thought a transformer will add inductance.

But as Bures et al. write, on the secondary side of the transformer, induction and resistance will be reduced 36-fold (with a 6-times step-down transformer). Someone with more electrical engineering background should take a look at that paper.

 

BTW: Dr. John Thompson (mentioned in the paper) also (co-)designed LPP’s DPF, see this Link.

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Posted: 19 October 2012 11:25 AM   [ Ignore ]   [ # 3 ]
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DHS was interested in a compact neutron source at high repetition rate.  The larger machines are not of interest to them for their applications.  Others have proposed it and it never worked out.  Too many neutrons per shot at high current leading to detectors getting swamped in neutrons and can’t see the signal.  DHS has moved onto advancing technology that can impact their mission in the short term. Long term, active interrogation scheme development is on hold unless you are a university and then they want very different technology like exotic particles or out there detection schemes. 

As far as the transformer goes, it requires some thought to scale up.  When the transformer PF was designed, the thought was to build a 300 kA system as the next step for another group.  The transformer has some nice properties but the mass and need for oil are downsides.  Eric contacted me about using the transformer system for his PF or next gen PF.  It is possible but I haven’t looked at it in the necessary detail.  Modeling the transformer PF is a bit more complicated due to the transformers and the approach to transformer core saturation.  I don’t think the cores in the RSI paper are saturating but there is some evidence that the transformer geometry is affecting the pinch behavior.  There is another paper in IEEE Trans plasma sci on the device (Bures Plasma Focus Neutron Generator, 2012).  Another paper is in the works dealing with 10 Hz operation and materials.  It have the first round of comments on the paper.  I am in the process of rebutting them and making corrections.  A paper looking at scaling which includes the RSI transformer PF (internally called AASC PF-2) and FoFu-1 is due out in Physics of Plasmas in Dec 2012.  I posted the keys graphs about the scaling law in the generator testing thread about a week or so ago. 

I’ve said before that our machines are similar to LPP and John Thompson is the reason.  John and I worked together for two years.  One of the things he taught me was high current pulse power design.  John consulted for our group and LPP for a while before he joined another company. 

-BB

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Posted: 19 October 2012 11:34 AM   [ Ignore ]   [ # 4 ]
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Henning - 19 October 2012 05:45 AM

That article requires a login, but it’s also available at the following location, which doesn’t need a login:
http://rsi.aip.org/resource/1/rsinak/v82/i10/p103506_s1?bypassSSO=1

Or direct download of PDF:
http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=RSINAK000082000010103506000001&idtype=cvips&doi=10.1063/1.3648117&prog=normal&bypassSSO=1

I was able to use my library card to access the science database on EBSCO through our Minnesota public libraries.  There is a listing of 522 articles just on dense plasma focus.  I’ve just started to browse these articles.
What information would be most useful to research now?

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