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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How is a plasma with only nuclei and electrons different?
How is a plasma with only bare nuclei and electrons, different from a plasma where the positive ions have some electrons attached?
I have looked in plasma physics books but never seen any mention of ...
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2answers
18 views
What is causing plasma confinement instability according to Erik Witalis?
Erik Witalis mentions problems with traditional plasma confinement like the one in tokamaks and particle beams. Instead he mentioned a different technique.
What is the problem with plasma confinement ...
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17 views
How much energy does it take to form a plasma channel with a laser?
The usage is for something like this https://en.wikipedia.org/wiki/Electrolaser
I know that the laser is powered for an instant in which a plasma channel is formed for the electricity to flow through,...
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14 views
Criteria for electrostatic approximation in microscopic/kinetic plasmas
I started pondering about the electrostatic approximation in relation to plasmas, where a particle's motion $\mathbf x(t)$ is governed by the Lorentz force:
$$
m\ddot{\mathbf x}=q(\mathbf E+\dot{\...
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1answer
22 views
Discrepancy when using Saha equation?
I was trying to calculate the level of ionization using Saha eq. for hydrogen gas at 1 atm pressure at 10 000 K and upwards. I used an Excel spreadsheet and the values I get don't match with other ...
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2answers
64 views
Lasers for plasma
Recently I had the same idea as given at A question about the properties of plasma and its potential use in recycling, or a similar one, rather. The basic idea is: could you turn stuff into plasma ...
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1answer
76 views
Why the geomagnetic field become stronger when solar wind is stronger?
The following description is from the webpage of Niels Bohr Institue's Former Centre for Ice and Climate
The Earth reacts to the solar wind by increasing the strength of the shielding magnetic ...
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22 views
How is the gyrating motion of a charged particle in a non uniform magnetic field?
In a uniform magnetic field it is simply a circle in 2D(x,y) and a helix with constant pitch in 3D(x,y,t).
How does this change when the magnetic field is not uniform ?
For reference : $\mathbf B = ...
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1answer
23 views
Magnetic compression of plasma?
What is the mechanism for plasma compression in the video below?
I provide a still from the video and a link to the actual video on YouTube.
https://www.youtube.com/watch?v=gsjWGz3YE5o
BTW, is ...
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35 views
How hot is a laser beam going to be when strong enough to create a plasma channel?
The type of laser I'm referring to comes from here: https://en.wikipedia.org/wiki/Electrolaser
Would an extended use of it be able to burn stuff?
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11 views
How is the electron (&ion) temperature measured in plasmas using Langmuir probes?
I want to know the concept behind the temperature measurement and what exactly the "probe" does apart from introducing potential in the plasma.
Also, while deriving an expression for electron ...
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1answer
60 views
Electric field of electron in alternating potential
I am considering the case of an electron placed in an alternating sinusoidal potential, of frequency 13.56 MHz (frequency typically used for RF plasma generation).
Suppose I have a simple 1D set up, ...
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1answer
215 views
How do we find the equation for the gyrating motion of a particle in a uniform magnetic field and a non-uniform Electric field? [closed]
Considering the gyrating motion is not negligible and also retaining the guiding center drift, how do we get the trajectories x(t),y(t),z(t) of the particle?
In this case is the variation in the ...
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18 views
Question about spatial uniformity of particle density in plasmas (from Bellan)
Early in Bellan he asks us to consider a finite-temperature plasma and assume that the ion and electron densities are initially equal and spatially uniform. He approaches the problem of calculating ...
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26 views
What is the equation for the gyrating motion of a particle in non-uniform magnetic field?
Consider a magnetic field B = Bo($1+x^2$) where Bo is a constant. And B is in the z-direction.
All the standard textbooks on Plasma Physics seem to skip over this part and only consider the guiding ...
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1answer
30 views
Temperature anisotropy in plasmas
If a species of a plasma is described by a distribution function $f(\mathbf{r},\mathbf{v},t)$, is it possible to have different temperature (thermal energy) values for different directions (x, y and z)...
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2answers
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Problem while constructing langmuir probe
I am working on DC glow discharges and want to construct a langmuir probe. Circuit I am using is as shown in the picture
Also, I am applying ~1KV across cathode and anode.
Problem I am facing is that ...
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1answer
40 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})$$ [Basic Space Plasma Physics by Rudolf A. Treumann & Wolfgang ...
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What Debye length should be used in plasma?
In short
Which expression should be used: (1) or (2)?
At length
Definition of the Debye length $r_D$ is following:
$$r_D=\left( \sum_{j}\frac{4\pi q_j^2 n_j}{kT_j} \right)^{-\frac{1}{2}}$$
It is ...
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1answer
21 views
Does density of states at Fermi level reduce or increase for decreasing the diameter of a nanowire?
As we decrease the diameter of a nano wire /quantum wire, does the density of the states at Fermi level increase or decrease?. If it does then, Why?
3
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1answer
44 views
Is there a “pinch effect” in a Tokamak?
Is there a "pinch effect" in a Tokamak, like in a linear Z-pinch or in a circular pinch (the ZETA machine from the late 50's)? Tokamaks run in a pulsed mode and a powerful circular current is induced ...
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1answer
29 views
Glow discharge : Why is the voltage stable with increasing current in the normal glow mode?
In the characteristics shown, the normal glow mode is from F to G, the voltage is stable with increasing current. I understand the explanation of how the electrode current density stays constant(the ...
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1answer
182 views
Landau's approach to collisions in plasma
I can't understand some steps in obtaining the collision term in the Boltzmann equation for plasma. For the first time it was made by L.D. Landau in his article "The kinetic equation in the case of ...
2
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1answer
33 views
Electron equations of motion for plasma
I'm reading through an Introduction to Plasma Physics by Francis F. Chen, and in the simplified derivation for plasma oscillation in 1D, the book quotes the electron equations of motion as:
$$mn_e\...
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0answers
49 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
34 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
17 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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49 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
49 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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30 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
41 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
33 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
85 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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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
21 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
54 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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2answers
137 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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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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27 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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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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38 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 ...
1
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1answer
45 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
39 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
78 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
47 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-...
