Talk:Double layer

message: Art, I restored "Quasi-neutrality" and "Particle flux" items, together with some reference. Perhaps I have misunderstood them?
I'm still not sure whether a Debye Sheath is synonymous with a Double Layer (is a Debye Sheath the name of one half of a double layer?). In which case, perhaps ion fluxes across Debye Sheaths and Double layers are different. --Iantresman 13:49, 8 October 2005 (UTC)
replies: text: I see everything as a Debye sheath because that's my specialty. (If your only tool is a hammer, everything starts looking like a nail.) I hope I can get a better grip on it with the help of your references. I'll continue to rephrase you if I don't understand your physics. Maybe between the two of us we'll get it right in the end. --Art Carlson 17:58, 8 October 2005 (UTC)
replies: text: Many thanks, appreciated. --Iantresman 18:12, 8 October 2005 (UTC)
thread_title: Untitled

message: I'm trying to describe how a double layer may form without resorting to maths. I am proposing the diagrams, right, and the text below. Since I am no expert, and my understanding may be incorrect, and would welcome criticisms before adding it to the main page. --Iantresman 19:36, 18 October 2005 (UTC)
replies: text: This explanation is about as good as any I could come up with. (I hope it's also right.) I think this mechanism can only explain weak double layers. Something additional, perhaps a net current, is needed to explain strong double layers. --Art Carlson 16:13, 19 October 2005 (UTC)
thread_title: Double Layer formation text

message: I have only quickly read through the page as it is now, and I think it needs major reconstruction. Here is some of the comments I have so far.
1st Paragraph
A double layer … in a plasma. 
You have to be more specific here what kind of double layers you want to discuss. There are the
DLs in current carrying plasmas and there are the DLs at the boundary of two different plasmas, 
these are not the same. The first one gets created, e.g. when the current gets too strong and the 
flow velocity of the current carriers is higher then the thermal velocity of the plasma, or when 
there is too little density and the current carriers have to be accelerated to maintain the current 
(this last one is comparable to the faster flow of a fluid through a narrowing of the flow channel).
Large potential drops and layer separation. 
The layer separation has nothing to do with the acceleration of the particles. The final 
increase in energy of the electrons and ions is given by the voltage drop ΔV and not by the length L 
between the pos en neg layer. 
Which in inhomogeneous … radiation. 
There is no need for inhomogeneous magnetic fields, let alone some obscure term like Bennett 
pinch. Charged particles in ANY magnetic field will “twirl” around the magnetic field lines and emit 
synchrotron of cyclotron radiation. There is no need to make this so highly complicated.
Double layers may self … into contact. 
Here we have the dichotomy. How do you mean self generate (there has to be a cause that they get
generated, I guess you mean here the DLs in a current carrying plasma). Then you also, like I said 
above, say that there are two kinds of DL, the second of which, does not carry any net current.
Classification, 1st item
Time-dependent: 
You mix up here the time-dependent and time-independent terms. A time-Independent DL is an 
idealized form, where as real DLs are time-DEPENDENT.
Particle acceleration: The same as I said above, with respect to the magnetic field presence and 
synchrotron radiation.
Formation: 
Rather than a magnetic field one. The original term is electrostatic double layers, why would 
anyone expect that the formation would be an magnetic field phenomenon?
Energy supply: 
I am not sure if you can write here that voltage drop and total current are directly 
proportional. It tends to be highly dependent on the properties of the plasma that the DL is 
embedded in.
Magnetized plasmas: 
Most of the plasmas in space are magnetized (if not all) why would you want to make a comment on
having the magnetic field keep the plasma from the walls? That is a very special case in the 
laboratory. Furthermore, that seems to suggest an initial thought that all DLs are produced by 
boundary effects, which is not the case.
Oblique DLs: 
A smooth bore magnetron. I think at least you mean Bohr. If there is truly a connection between 
an oblique DL and a Bohr magnetron I do not think so. AFAIK a Bohr magnetron has something to do with
the electron circling around a proton in a hydrogen atom. It sets a value for a basic magnetic unit.
 
The DL may also drift: 
but this is not only the case for oblique DLs.
Simulation: 
I think if you wanted to keep the page without math but then come with a BGK approach, that is
making rather strange choices. Also, I think that only the magneto-acoustic DLs are described like 
that.
DL formation needs to be totally rewritten, as it only discusses the boundary double layer, which 
does not carry any current. The current carrying double layers, which are e.g. in the Earth’s 
magnetosphere form in a different way. These are also the DLs that you are so interested in, the ones
that accelerate particles and can create beams etc. 
Almost per definition, the boundary DLs are marginally strong DLs always on the order of the thermal 
energy of the hot plasma.
I do not understand the strange boxes in the page, but I don't care :-)
:Have at it! I think Ian and I may be slightly out of our depth on this subject, so we welcome more expert knowledge. I hope to learn something from you. --Art Carlson 17:47, 20 November 2005 (UTC)
replies: text: I've made some tweaks to the double layers page based in your comments. --Iantresman 12:18, 24 November 2005 (UTC)
thread_title:  Changes for Wiki Double Layers 

message: I have made the changes in these sections and I added also the formation section as it seemed to be the logical location. --Tusenfem 13:28, 29 March 2006 (UTC)
thread_title: Changes Classification and Quasi-Neutrality

message: Okay, as there were no comments on the last I continued editing the page. I have now changed it untill the list of characteristic double layers.
I still have trouble with the bore magnetron, but added a link in which it is dicsussed. There is no wiki page that discusses it, it only gets mentioned on one page.
For the next part, naturally the formation will be deleted, as that has been already discussed above. And the history needs to be replaced. Maybe also some figures need to be moved. --Tusenfem 19:05, 2 April 2006 (UTC)
thread_title: Changes to the last part as proposed above

message: Okay, I edited on, changed the history of the DLs and I have started the mathematical part of the page. More will follow. 
I need to find the figure I need in the history part, which shows the potential structure in the DL. I don't have it on this laptop.
Cheers --Tusenfem 11:58, 9 April 2006 (UTC)
thread_title:  On and On and On 

message: hi all, I have just finished writing up my PhD thesis on simulation of double layers. In particular, I work in the group that has invented the Helicon Double Layer Thruster (based on current-free double layers). I don't have much time at the moment to put into the DL wikipedia page, however, once my thesis is accepted, I am happy to send it to you guys - you may interested in the intro. I have noticed a few things that are stated in the article and that are not really true.
Cheers, Albert Meige
:Sounds great. I think there is also a Wiki page devoted to the Helicon Double Layer Thruster --Iantresman 08:37, 19 April 2006 (UTC)
replies: text:  Hey Albert! Nice to hear about another person who wrote his thesis on DLs. I would love to read it. My topic was "strong double layers in astrophysical plasmas". Good luck and cheers, Martin. --Tusenfem 20:10, 19 April 2006 (UTC)
thread_title:  thesis on double layers 

message: I'd like to tap the expertise which is obviously present here. Whether it will ultimately benefit the article I can't say yet.
I worked many years with Langmuir probes in strong magnetic fields. The usual picture is an electrode that draws current from a plasma, and the current flows mostly along the magnetic flux tube intersecting the electrode. There are many things that are still not understood. Above all, the ratio of the electron saturation current to the ion saturation current is usually several times less than the value expected (roughly the square root of the mass ratio). In extreme cases the electron saturation current is even smaller than the ion saturation current! Another problem is that the current apparently does not (always) follow the flux tube. In extreme cases it seems to flow across the field (in the direct of E, not the direction of EXB) as easily as along it. Over the years I considered many theories, but I never thought much about double layers. Double layers are simply not well-known in the fusion research community.
That leads me to my first question. Is there a reason to expect that double-layers are not important in fusion plasmas? Is it possible they are important but have been overlooked? Where would double layer effects most likely be manifest in a tokamak? That brings us to the second question. Is there any obvious or at least plausible way that a double layer somewhere in the current tube can explain the strange features of Langmuir probes?
If I were still active in the field I would dig into the literature and figure it out myself. As it is, I am now working in astrophysics and must treat the question more or less as a hobby. But if you can throw me a chunk of meat, I might still take up the chase.
Thanks. --Art Carlson 10:31, 15 May 2006 (UTC)
thread_title:  Langmuir probes 

message: I have changed the text regarding the Bohr Magnetron (h e / 2 pi m), which is not a unit of energy, to which it was changed, it is a unit of magnetic moment. First when multiplied by the magnetic induction B it becomes an energy. --Tusenfem 22:03, 19 May 2006 (UTC)
thread_title:  Bohr Magnetron 

message: I disagree with the biophysics part about cellular structure, Ian. I hope you understand that the cells in biophysics are totally different from the cells that Alfven was talking about. Biological cells have membranes that are corpuscular, whereas plasma cells do not.--Tusenfem 19:33, 26 May 2006 (UTC)
replies: text: Indeed, I agree they are difference, but there is at least one peer-reviewed paper using electric double layers to help explain cellular double layers... so I figured that Alfvén and Langmuir's comments were relevant. Perhaps you could take a look at the refernces by Mituo Uehara and Jennifer Gimmell, and explain the analogy better? --Iantresman 19:47, 26 May 2006 (UTC)
thread_title:  Biophysics