Questions tagged [plasma-physics]
Theory, lab and space experiments, and calculations related the physics of plasmas, i.e., matter constituted by ionized atoms.
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What Debye length should be used in plasma?
In short
Which expression should be used: (1) or (2)?
At length
Definition of the Debye length $r_D$ is following:
$$r_D=\left( \sum_{j}\frac{4\pi q_j^2 n_j}{kT_j} \right)^{-\frac{1}{2}}$$
It is ...
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1answer
20 views
Does density of states at Fermi level reduce or increase for decreasing the diameter of a nanowire?
As we decrease the diameter of a nano wire /quantum wire, does the density of the states at Fermi level increase or decrease?. If it does then, Why?
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1answer
38 views
Is there a “pinch effect” in a Tokamak?
Is there a "pinch effect" in a Tokamak, like in a linear Z-pinch or in a circular pinch (the ZETA machine from the late 50's)? Tokamaks run in a pulsed mode and a powerful circular current is induced ...
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1answer
24 views
Glow discharge : Why is the voltage stable with increasing current in the normal glow mode?
In the characteristics shown, the normal glow mode is from F to G, the voltage is stable with increasing current. I understand the explanation of how the electrode current density stays constant(the ...
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1answer
177 views
Landau's approach to collisions in plasma
I can't understand some steps in obtaining the collision term in the Boltzmann equation for plasma. For the first time it was made by L.D. Landau in his article "The kinetic equation in the case of ...
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1answer
24 views
Electron equations of motion for plasma
I'm reading through an Introduction to Plasma Physics by Francis F. Chen, and in the simplified derivation for plasma oscillation in 1D, the book quotes the electron equations of motion as:
$$mn_e\...
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0answers
46 views
Are / Why are the H II regions positively charged?
One of the questions in our recent astrophysics course homework was to find the general opacity $\kappa$ of H II regions. We know that the H II regions are almost entirely ionized hydrogen and I ...
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0answers
31 views
What are the prerequisites for a free electron and an atom/ion to recombine?
I'm mostly interested about recombination not in plasma (e.g., recombination of beta particles with atoms that they pass by), although the rules are probably the same.
Say, there's a free electron ...
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1answer
4k views
Why can’t you see at the start of the Big Bang?
I’m quite confused with regards to photon emission throughout the creation of the universe.
From what I’ve heard, there was no light (of any frequency) in the universe until 300,000 years after the ...
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0answers
16 views
Plasma Cyclotron Heating Textbook
I'm thinking of doing an independent reading course on the subject of cyclotron heating of plasmas, and I've love to hear any textbook recommendations. So far I've only found Gareth Guest's book, ...
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0answers
41 views
Saha-Boltzmann Equation
I am following Ahmed, Ahmed, Rafiqe & Baig A comparative study of Cu–Ni Alloy using LIBS, LA-TOF, EDX, and XRF paper on Laser Induced Breakdown spectroscopy.
It mentions two versions of Saha-...
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1answer
48 views
Polarisation of electron
Suppose you have a cloud of electrons each with position $\mathbf{r}_i$, basically modeling a plasma. Why can its polarisation be written as $$ \frac{-e}{V}\sum_i \mathbf{r}_i $$
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0answers
29 views
The Magnetic Field Strength of Crab nebula
Consider the spectrum of the Crab nebula shown below.
Assuming that the ~TeV photons are produced by Inverse Compton scattering of
synchrotron photons from around the peak of the synchrotron ...
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3answers
2k views
Is Sun brighter than what we actually see?
I learned from that plasma can reflect radiations of frequency less than that of its own oscillations. If so, considering the plasma in Sun's atmosphere, it should also reflect solar radiations.
That ...
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1answer
40 views
Can hydrogen plasma react with oxygen?
What if you put hydrogen in a vacuum and turned it into a plasma? There is no oxygen in the vacuum, but once you eject the plasma would it react drastically with the oxygen?
Would it explode?
Would ...
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0answers
26 views
Minimum Voltage to Sustain an Arc
I've read that after a plasma channel is created in air, the resistance decreases significantly and the arc can be sustained with a much lower voltage, as long as the heat dissipated by the plasma is ...
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0answers
77 views
Why did the Lockheed Martin compact fusion reactor failed? [duplicate]
What made the compact fusion reactor to not be compact. What assumptions did lokheed made in its simulation that showed that it could work. Can we do anything that could make it work or it is ...
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0answers
13 views
How to do elementary plasma diagnostics?
How can I do elementary plasma diagnostics if I want to know e.g. the temperature of a plasma, if it is in thermodynamic equilibrium, the temperature of the various ionic species and the temperature ...
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1answer
20 views
when a gas turns into plasma does its particles get smaller?
In expansion the space in between the particles increase, not the particles, however does that still apply to plasma? and when a gas turns into plasma do the particles get smaller?
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2answers
53 views
Plasma inside deuterium spectrum tube?
Hullo,
In a deuterium spectrum tube there is a thin capillary in the middle (see picture) that glows purplish sort of. Now, I wonder what this glowing part actually consist of? Is it a completely ...
2
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1answer
39 views
Why are soft x-ray images of plasmas considered to represent magnetic field line configurations?
I'm learning about plasma physics and I've seen a number of papers which state something like 'soft x-ray pictures reveal the magnetic field lines', and it is common to use a soft x-ray image of the ...
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1answer
94 views
What is meant by “collective behavior” in the definition of plasma?
"Plasmas are many-body systems, with enough mobile charged particles to cause some collective behavior ." [M.S. Murillo and J.C.Weisheit Physics Reports 302, 1-65 (1998)].
In the above definition ...
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0answers
15 views
Plasma tubes and accelerators
to find a relation between acceleration produced by a plasma beam accelerator and the density of the plasma and length of the plasma tube. So what is the feasibility of this idea .
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26 views
Pressure inside spectrum tube?
I asked the firm who sells them here in Sweden, but they didn't know. I asked sellers on eBay, same answer. Is it different with say neon and hydrogen? Or is it the same pressure in all? I'm ...
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0answers
18 views
Frank Hertz I-V curve
Now my question is assume here gas to be hard balls with no possibility of inelastic collisions and electrons are emitted from a cathode and they reach anode through this soup of atoms. Since ...
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0answers
36 views
Magnetic cage for keeping plasma around itself
Let's assume that we have an object in vacuum, venting hydrogen plasma around itself. This object has a powerful internal electrical source, connected to a cage of superconducting wire around it, in ...
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0answers
38 views
Number of TM Modes in Waveguide in MIM waveguide
I'm working on a practice question requiring me to find the total number of TM modes (including normal modes and SPP excitation modes) in a symmetric Metal-Insulator-Metal (MIM) waveguide only knowing ...
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1answer
42 views
Electron density Saha Ionization Equation
Saha-Boltzmann equation describes the ratio of number densities between any two consecutive ionization states and its product with the number electron density i.e.
$$n_e\frac{n_{i+1}}{n_{i}}$$
Here, ...
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1answer
37 views
Creating Aurora-like phenomenon in a laboratory
Is it possible to recreate Aurora's in a laboratory experiment? Obviously, I'm not asking if it's possible to have bands of plasma thousands of kilometers long inside a lab. But rather, is it possible ...
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2answers
75 views
How many temperatures has a plasma?
In nonthermal plasma, not all particles move in the same way. The electrons are different from other particles. Both can be described as having a temperature separately. But that would mean, one piece ...
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1answer
41 views
Do plasmas really not experience a $\nabla \vec B$ drift even though the individual particles do?
I'm currently working through Chen's Introduction to Plasma Physics and Controlled Fusion, and I just got to the chapter on the fluid theory of plasmas. Chen claims that the $\nabla\vec B$ drift does ...
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1answer
46 views
Temperatures of Galaxy Clusters
Recently I've read about clusters of galaxies and have tried to understand how one can measure their mass and temperatures.
Clearly, we can physically measure a couple of things such as the flux of X-...
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0answers
40 views
Modelling liquids like water with BBGKY-hierarchy
The BBGKY hierarchy is a well-known useful possibility to derive kinetic equations for gases and Plasma. The N-particle System is reduced to few-particle Systems by Integration over many Phase space ...
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1answer
63 views
Is looking at a toy plasma ball dangerous for your eyes?
I have a rather cheap USB toy plasma ball. Now I read, that plasma balls can be an eye hazard, if the glass does not filter the emitted UV light. I do not find many sources on how dangerous this ...
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1answer
40 views
Taking moments of the Vlasov equation
Given the following term:
$\nabla_{v} \cdot \left[ \frac{e}{m_{s}} (\textbf{E} + \textbf{v} \times \textbf{B})f_{s} \right]$
where $\textbf{E}$ and $\textbf{B}$ are the electric and magnetic fields ...
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0answers
39 views
Plasma Frequency of Indium Tin Oxide
What does determine the plasma frequency? The formula is:
$\omega_p² = \frac{4 \pi N e²}{m}$
and for frequencies above the plasma frequency the material is transparent. So for Indium Tin Oxide the ...
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1answer
30 views
Explain the equation describing total energy of the electrons in HET
I have this equation describing total energy of the electrons in HET (Hall-effect thruster):
$$\frac{\partial (\frac{1}{2}mn(v_{ex}+v_{e\vartheta})^2 + \frac{3}{2}nT_e)}{\partial t}+\frac{\partial (\...
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1answer
39 views
Would plasma that is as electron dense as lead be a better shield than lead against gamma radiation?
Imagine you somehow managed to maintain a body of plasma which had the same electron density as an identical volume of lead or other heavy metal. (Suppose you ionized lead.) Would it be a better gamma ...
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1answer
20 views
Opacity of ionized/non-ionized gases
In which state is matter more opaque to radiation? I'm talking about gaseous vs plasma. I know that opacity is a function of frequency in general, but I thought that, since a non-ionized gas has more ...
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1answer
38 views
Plasma Waves at Different Frequencies
I am trying to determine what plasma waves appear at what frequency ranges. Particularly, I am interested in exploring plasma waves occurring between 100kHz to 1MHz. Is this a bad frequency range to ...
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1answer
32 views
How to measure an electron plasma with an electrically biased probe?
I want a crude way to confirm the existence of an electron cloud in a moderate vacuum of 2 mTorr. In my set up, filaments emit electrons into a magnetic trap which concentrates them (similar to an ...
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1answer
75 views
What is a flux conserver and how does it work?
A number of plasma physics papers I've seen mention "flux conservers", e.g. this paper. However, despite my best efforts, I can't find a good description of a flux conserver or how it actually works.
...
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1answer
109 views
Unmagnetized plasmas in space
Please, I need some information about high temperature plasmas in astrophysical environments.
To my knowledge, plasmas in astrophysical environments are magnetized (is it true?). Are there ...
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0answers
50 views
Debye screening in $\mathbb{R^d}$
Consider the Poisson-Boltzmann equation
$$
\nabla^2 V(r) = -\frac{1}{\epsilon_0}en\left(1 - e^{e V(r)/k_BT}\right)
$$
which models the electrostatic potential in a spherically symmetric ideal gas of ...
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2answers
60 views
A question about the properties of plasma and its potential use in recycling
I have multiple questions linking into a potential recycling method; I'm curious if any of these ideas are possible, or if I'm having a pipe dream:
Can any gas be turned into plasma?
Can multiple ...
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0answers
49 views
Solution of the diffusion equation in a plasma
considering the diffusion equation taking into account diffusion and mobility of charged particules in a plasma of density $n(z)$ and potential $\phi(z)$, we have :
$$
\frac{n(z)}{\tau}=\frac{\...
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0answers
30 views
Timescales of plasma recombination and fluorescence?
I am currently working on a very simple model for the radiation from electric arcs.
As both fluorescence (internal electronic transition) and plasma recombination occur, I would like to compare the ...
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0answers
52 views
Question about normalizing fluid quantities (plasma physics)
I'm having trouble understanding the way the plasma fluid equations are normalized in Ch. 4 of Fitzpatrick's "Plasma Physics: An Introduction." Here's a a link to the page in question. Equations 4.147-...
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2answers
38 views
Regarding the $E x B$ drift in the Earth's magnetic field
So I have a burning question: The only reason that the E x B drift doesn't generate an electric current is because both the electrons and the positive ions move towards the same direction (towards ...
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2answers
168 views
Math needed for plasma physics? [closed]
I am curious about what kind of math is needed for studying plasma physics, especially for the magnetohrodynamics.
I know there are lots of PDEs in plasma physics, but how about real analysis? Or ...
