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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46 views

Mathematical form of distribution function with high energetic beam

Maxwell Boltzmann distribution function (MBDF) has the form $$f(v)=n(\frac{m}{2\pi k_BT})^{\frac{3}{2}} exp(-\frac{mv^2}{2k_BT})$$ [Basic Space Plasma Physics by Rudolf A. Treumann & Wolfgang ...
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80 views

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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23 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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51 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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32 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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184 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
35 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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51 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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35 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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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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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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64 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
50 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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35 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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57 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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68 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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105 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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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
24 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
58 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 ...
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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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2answers
342 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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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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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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19 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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44 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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42 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
54 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
44 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
90 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
42 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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48 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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45 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
78 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
46 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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56 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 (...
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34 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
41 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
44 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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43 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
101 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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126 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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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
102 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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59 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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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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68 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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51 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 ...