Talk:Pinch (plasma physics)

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I think that perhaps Z-pinch/Theta pinch fusion devices need thier own page.

The Z-pinch machine does, not sure about thete pinch devices. --Iantresman 19:19, 13 September 2006 (UTC)

Z-pinch already does have its own page...? Mgmirkin 23:04, 12 October 2006 (UTC)

Contents 1 EM Pinch used in shrinking/deforming 2 Pinch instability? 3 Carlqvist relation 4 Overly long quotes 5 Water pinching analogy 6 Proposed merger from "Pinch (magnetic fusion)" to "Pinch (plasma physics)" 7 Images

[edit] EM Pinch used in shrinking/deforming

I've added a few External Links to Teslamania and a Tesla "down under" Australian page that relate to using electricity to shrink coins and to "pinch" or crush cans. They seem to go into a bit of the practical concerns and theory behind it. Not peer reviewed, per se. But, nonetheless decent resources worth a read. Not like anyone professionally studies can crushing or coin shrinking anyway. More of a hobbyist type thing, methinks. *wink* Hope you guys find it useful and it's not too off topic. Seeing as can pinching was discussed in the article as an example of a practical use or demonstration of "pinching" something electromagnetically. Mgmirkin 23:04, 12 October 2006 (UTC)

[edit] Pinch instability?

Just wondering if Pinch instability from the Plasma Physics article request page was synonymous with this topic. If so, perhaps we should put it into the 'also known as' section and set up a redirect from Pinch instability, as well as make the mention of the topic from the Instability page (plasma instabilities section) into a WP link to this article, for internal WP consistency (trying to see if folks can get decent articles for the various plasma instabilities listed on that page, so the items listed can link to said articles). I just don't know instabilities well enough to know for certain they're the same, but I suspect they are. (Going on the assumption that Bennett pinch and Pinch instability are synonymous.) Mgmirkin 19:34, 19 November 2006 (UTC)

No. The pinch effect does not necessarily involve an instability of any sort. Of course, if you create a pinch, it may be unstable in a number of ways, like the sausage instability or the kink instability. You might want to put both topics in the same article, but a simple redirect is not enough. --Art Carlson 19:46, 19 November 2006 (UTC)

[edit] Carlqvist relation

• The Bennett relation and the Generalized Bennett Relation, are both described in the article.
• The Carlqvist relation is derived from the Generalized Bennett Relation (as was described in the article), and is verifiable. --Iantresman 20:02, 14 January 2007 (UTC)

[edit] Overly long quotes

The article contains a couple of overly long quotes. Are they copyright violations? Cardamon 12:10, 15 January 2007 (UTC)

I agree. The Pease and Northrupp footnotes simply quote text from the external references. Oz tangles 10:58, 30 August 2007 (UTC)

[edit] Water pinching analogy

• Art, where it was written, "Like plasma, the water accelerates and moves faster through the pinches", there was no implication of a similar cause or relationship, only that this is an analogy. Perhaps you can phrase it better. If you have access to Trubnikov's paper, it is he who makes the analogy. Plasma moves faster through magnetic pinches, in an analogous way that water moves faster through the pinching caused by surface tension.

If the analogy is only superficial, then it is more likely to mislead than to help the reader. Do the pinch sections of a stream of water move with the water or stay fixed relative to the faucet? If you don't have gravity, what happens then? Does the strength of the pinch depend on the velocity in either water or plasma? --Art Carlson 15:04, 15 January 2007 (UTC)

With a cursory glance at Trubnikov, I don't see any mention or relevance of flow relative to the perturbation. --Art Carlson 15:15, 15 January 2007 (UTC)

• I quite liked the description (a) because it hadn't occurred to me before, (b) the water analogy helped me visualize it. --Iantresman 14:42, 15 January 2007 (UTC)

What did it help you visualize? --Art Carlson 15:04, 15 January 2007 (UTC)

• I liked the analogy of magnetic pinch (invisible) to surface tension (visible), and the analogy of plasma flow (invisible) to water flow (visible). I also liked the idea that you can simulate your own pinch merely by turning on a tap (fawcet).
• So it may not be a perfect analogy, but I felt there were sufficient analogies to make it worthwhile to mention.
• Do you have access to Trubnikov full paper? --Iantresman 15:30, 15 January 2007 (UTC)

I don't object to the analogy between the plasma pinch and a stream of water beading. Otherwise I would have removed the whole illustration. There are, of course, limits because the beading illustrates the instability, not the equilibrium, and because a plasma is compressible but water is not. (Another problem is the non-linear development, since electromagnetic forces cannot make separate beads like surface tension does. --Art Carlson 19:47, 15 January 2007 (UTC)) What I object to is the introduction of something that sounds like Bernoulli's principle without adequate justification. --Art Carlson 16:07, 15 January 2007 (UTC) P.S. What I found from Trubnikov was this version of "On the possible generation of cosmic rays in plasma pinches".

Thanks for sending the paper. Based on this one, too, I find the formulation "Like plasma, the water accelerates and moves faster through the pinches" to be wrong for both plasma and water. He is concerned with the distribution of particle velocities, not the fluid velocity, and that everywhere, not just at the constrictions. Anyway, the present version seems just fine to me. Do you think something is missing? --Art Carlson 19:42, 15 January 2007 (UTC)

• I thought I'd check with you anyway, thank you for taking the time to look through it. In which case the current content is fine. --Iantresman 21:08, 15 January 2007 (UTC)

[edit] Proposed merger from "Pinch (magnetic fusion)" to "Pinch (plasma physics)"

A fusion pinch is obviously also a plasma pinch. The entire content of Pinch (magnetic fusion) is also appropriate to Pinch (plasma physics). Both articles are short enough that the merged article will be a reasonable length (and is not likely to grow excessively). The only reason I could think of to have a separate article for fusion aspects would be if we included a lot of information on the construction and operation of experiments and proposed reactors. Considering that pinches are now "also ran" configurations, I don't think we should write such an article. --Art Carlson 10:42, 17 January 2007 (UTC)

At this stage, I think that makes sense. In the future, the articles may well grow in length as certain aspects of detailed, in which a later separation might make sense. --Iantresman 10:53, 17 January 2007 (UTC)

While we're at it, we might want to consider encorporating Z-pinch, as well. (In any case, we need to clean up the disambiguation at Pinch and the cross references.) --Art Carlson 11:04, 17 January 2007 (UTC)

Z-pinch looks somewhat different, more about the machine than the pinch? --Iantresman 11:45, 17 January 2007 (UTC)

What's it got? A bit on the physical mechanism and some history, especially the evolution of the idea with the fusion energy program. That would fit right into the first two sections here. Any engineering details can be put in the article on the Z machine. --Art Carlson 12:53, 17 January 2007 (UTC)

Makes sense. I would suggest adding some merge tags to the articles, just to see whether anyone else can add anything. --Iantresman 13:08, 17 January 2007 (UTC)

Merging from Pinch (magnetic fusion) is fine with me. Cardamon 22:44, 18 January 2007 (UTC)

I added a "mergeto" tag to Z-pinch. That proposal should be discussed here, too. --Art Carlson 13:32, 17 January 2007 (UTC)

In my opnion, there are enough differences between both articles. I don't see what would be accomplished by merging them.--Vatic7 19:02, 31 October 2007 (UTC)

[edit] Images

Nice image of the crushed lightning rod, though it seems to have misaligned some of the other images. eg. the Bennett relation chart is no longer near the appropriate section. Perhaps the lightning image should go as it is quite common, or some of the others should be made smaller? --82.84.83.94 11:22, 30 August 2007 (UTC)