Theory, lab and space experiments, and calculations related the physics of [plasmas](https://en.wikipedia.org/wiki/Plasma_(physics)), i.e., matter constituted by [ionized atoms](https://en.wikipedia.org/wiki/Ion).

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1answer
54 views

What state of matter is thunder? [on hold]

I know of solid, liquid and gaseous states of matter but what state of matter is thunder? Is it gas, liquid or solid?
6
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1answer
106 views

Why is a stellarator-type nuclear fusion reactor so oddly-shaped?

My first impression: It's a mess. Why is it shaped like that? I can't find any info about its shape other than it's a special arrangement of magnetic coils. (link) Here's some more images of it on ...
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69 views

Why did they start Wendelstein 7-X With Helium?

Just saw the first Hydrogen plasma at the Wendelstein reactor. I haven't found anywhere that gives a good explanation as to why they first used a Helium plasma - can anyone shed any light?
1
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1answer
36 views

Potential energy of a spherically symmetric charge density in a spherically symmetric electrostatic potential

I'm interested in calculating the potential energy of a spherically symmetric charge density in a spherically symmetric electrostatic potential. More specific, I'm currently trying to calculate the ...
0
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1answer
23 views

Differences between thermal and non-thermal plasmas

I have a doubt about plasmas which may as well be trivial or very stupid, but I couldn't get a clear and straightforward answer anywhere I looked, and I can't get the grasp of it since I wasn't given ...
2
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0answers
54 views

Estimating temperature with Boltzmann relation with split emission lines

I'm trying to estimate the temperature of a plasma through the use of hydrogen lines, $H_{\alpha}$ and $H_{\beta}$ using the Boltzmann relation: $$ \frac{ n_{2} }{ n_{1} } = \frac{ g_{2} }{ g_{1} ...
1
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1answer
35 views

Difference between reflection mechanisms in dielectric, metals and plasma

How the reflection and transmissions mechanism are different in metals, dielectric and plasma? I know that the density of free electrons is playing the role. Can anyone give an insight what is ...
0
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0answers
16 views

Plasma Ball and effect of Humans

If one brings a fluorescent bulb close to a plasma ball, why does the touch of a finger cause the bulb to become brighter when touched? Why, when you hold the metal portion of the bulb, as opposed ...
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0answers
55 views

Response function in plasma

I am reading an article where authors investigate how a particular type of electrostatic waves propagates in a plasma. They start with the Poisson's equation in the next form: $$\nabla^2 ...
2
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2answers
93 views

Would a mass of bare iron nuclei be visible ?

As I understand it most of how objects look is because of how photons interact with electrons and photons emitted when excited electrons fall to lower energy levels producing photons. So if one traps ...
3
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1answer
36 views

Liquid/solid to plasma?

During a phase change we can go from solid to gas via the process of sublimation. The diagram given below indicates that there is no analogous process for the transition from solid (or liquid) to ...
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21 views

Why is the enclosed area of a voltage-charge Lissajous figure to the dissipated energy per cycle?

These Lissajous figures turn up in the study of Dielectric Barrier Discharges driven by AC voltages, but I believe the concept of the "dissipated energy=area enclosed curve" is much more general. By ...
3
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2answers
41 views

What is crater's influence on laser ablation?

In many laser ablation experiments (especially Pulsed Laser Deposition), target is moving to avoid crater formation. But I can't find any source that says why it is needed to avoid it. So why is ...
1
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1answer
51 views

What is meant by infinite wavelength?

1#When an electromagnetic wave propagates in a plasma, with increase in plasma density the phase velocity ($v=\frac{\omega}{k}$) of wave increases. So at cut-off point $k=0$, and phase velocity ...
1
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2answers
56 views

The basic physics behind the plasma frequency

The dispersion relation of ordinary wave in plasma is \begin{equation} \omega^2=\omega_{p}^{2}+c^{2}k^{2}, \end{equation} where $\omega_{p}=\sqrt{{4\pi n_{0}e^{2}}/{m}}$ is the plasma frequency. ...
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21 views

plasma frequency in terms of thermal energy

The relativistic factor (in terms of momentum) is given by \begin{equation}\label{} \gamma=1/\sqrt{1-v^{2}/c^{2}}=\sqrt{1+p^{2}/m^{2}_{0}c^{2}}, \end{equation} When thermal momentum is greater ...
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0answers
48 views

Can a spheromak propagate in vacuum?

I recently learned about (and am now fascinated by) spheromaks. I am no expert on plasma physics, but as I understand they are analogous to propagating toroidal vortices (smoke rings), but with plasma ...
2
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2answers
66 views

What defines a cold plasma?

Been looking for this very simple answer for a while now, and google returns a face cream with the words cold plasma in it. Very frustrated. Just wondering, what constitutes a cold plasma in the ...
0
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0answers
56 views

How much do we know about the characteristic time for electron-ion recombination for a dense plasma?

As mentioned, how much do we know about the characteristic time for electron-ion recombination for a dense (noble gas) plasma (i.e. density of electrons at $\approx 10^{21} \textrm{cm}^{-3}$) at ...
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0answers
31 views

What are the equations needed to determine pressure and velocity/acceleration of a plasma in a electromagnet coil

I am trying to develop a new type of fuel injector, however I am having trouble finding the plasma dynamics equations I need. I also am having trouble finding the equations to determine the ...
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25 views

The change of length of positive column in glow discharge

When I was doing the experiment of glow discharge, I lowered the voltage between electrodes and find that the length of positive column will increased quickly around a certain voltage(the interval of ...
2
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0answers
43 views

Pair correlation function of the QHE “plasma”

I am trying to teach myself the theory of quantum Hall effect, and realized that I can not reproduce a basic textbook result. Let me closely follow Girvin's Les Houches lectures ...
3
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0answers
56 views

What is the effective electron mass in a plasma?

Is there a way to calculate the effective electron mass in plasmas? Effective electron mass is usually defined as varying from the vacuum electron mass in solid state physics. However, momentum ...
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14 views

Generation of negative ions in air [duplicate]

What is the main physical mechanism behind the generation of negative ions in air by a high negative voltage electrode ?
2
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2answers
61 views

Limitations of particle in cell method for high desnity plasma

Are there any limitations of particle in cell (PIC) method for high density plasma? To be more specific, is modelling of a narrow channel of high density plasma possible or are there any limitations ...
9
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1answer
231 views

Does matter found at densities of white dwarfs “feel” more like a solid, liquid or gas?

I'm wondering what it would be like to touch or interact with very dense degenerate matter like this found at white dwarfs. I understand that white dwarfs are initially very hot, but for the sake of ...
2
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0answers
50 views

How much of the Solar convection zone is completely ionized?

I was reading about the energy transportation in stars here, and I found this: "The outer portion of solar mass stars is cool enough that hydrogen is neutral and thus opaque to ultraviolet photons, so ...
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1answer
43 views

Fire: Understanding the states of matter and its mass

If the fire is a state of matter (plasma) and every matter has mass. My question is: how we can calculate the mass of a fire?
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29 views

How do you calculate the brightness of an electronic arc through a gas?

Quick question: I want to model the brightness of a xenon flash tube when a capacitor is discharged through it, but I can not find any equations related to this. It only has to be a rough model, just ...
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1answer
45 views

Does venus have plasma in its atmosphere?

Is it hot enough on Venus for thermal collisions to ionize molecules? If not, what temperature would it have to be?
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1answer
74 views

How does a Pulsed Plasma Thuster work?

My friend was describing a Pulsed Plasma Thruster (PPT) to me, and we couldn't figure out how it actually worked. The setup involves two conducting plates with a potential difference and a solid, ...
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0answers
36 views

Why can xenon gas stay ionised after the “trigger voltage” is removed?

From my understanding of a Xenon flash circuit, a storage capacitor and a trigger capacitor are charged up to about 240V (both with similar RC values, but less capacitance is needed for the trigger ...
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0answers
57 views

What happens to Hydrogen-Boron plasma at 3 billion Kelvin?

A recent popular report states (beware, I believe it is not peer reviewed and this slightly smells like a PR stunt) that a private company TriAlpha has made some notable progress towards ...
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51 views

Units in Plasma Physics

What are the units people use in plasma physics? I am having hard time converting an equation from an old paper to SI units. I saw temperature being defined in $eV$. I assume this is $eV/k_B$ with ...
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44 views

What is the role of the Cowling, Pedersen and Hall resistivities (or conductivities) in plasma physics?

The current density $\vec{j}$ can be computed as $\vec{j} = \vec{\vec{\sigma}} \vec{E}$, where $\vec{\vec{\sigma}}$ is the conductivity tensor and $\vec{E}$ is the electric field. This conductivity ...
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1answer
93 views

Using ion beam to create strong magnetic field

Consider, I want to make very strong magnetic field in some spot in space ( focus ) but I cannot put any solid material ( like metal conductor, or superconductor ) close to that spot (e.g. because ...
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0answers
65 views

Is thermal and electrical conductivity correlated for all phases of matter?

After reading this interesting post about why copper is a great heat conductor, I wondered if a plasma would conduct heat better than a gas. Or, are some properties like density more important for ...
2
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1answer
59 views

Electron beam in magnetic field - increase or decrease the field?

When I fire an electron beam into homogenous magnetic field ( eg. inside Helmholtz coil ) it will bend into a circle => it will form a coil ( = current loop ) itself. The magnetic field created by ...
2
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1answer
43 views

Induction equation in a rotating frame

In his book, Tom Cravens refers to the induction equation (perfectly conducting limit) in a rotating frame, the Sun. See link below: ...
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0answers
14 views

Measured versus Predicted Energy gain in Tokamaks with size

Does there exist a known relationship between the energy gain of Tokamaks in dependence of their size? How do fusion engineers can predict how much gain will a given Tokamak size deliver? Do they just ...
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22 views

What is the resistance of ionised Xenon gas?

I need to know the typical resistance of ionised xenon gas inside a xenon flash tube, so I can use circuit analysis to calculate the flash duration. I know that a 180uF capacitor is charged to ...
2
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0answers
59 views

Geometry of magnetic field lines in plasmas/MHD

So I'm trying to gain an intuitive grasp of plasmas and magnetohydrodynamics. There's a couple of questions I have. What does it means magnetic field lines are frozen into "plasmas"? Is it that ...
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0answers
95 views

How to calculate electrical and thermal conductivity, enthalpy and density of plasma column in air for a series electric arc?

I am modeling an electric arc according to "Lowke's Simple theory of free burning arc". Its a very interesting theoretical arc model and I want to implement it in Matlab/Simulink. But here, the arc ...
1
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1answer
242 views

Book suggestion for introductory plasma physics

I have an undergraduate background of electrodynamics, special theory of relativity and quantum mechanics. I would like to study plasma physics by myself so please suggest a few introductory books on ...
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0answers
18 views

why is clear electron saturation not obtained in a Langmuir probe experiment?

I recently conducted an experiment to study the I-V characteristics of a Debye sheath, but I can't obtain electron saturation. Why does it happen?
5
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3answers
152 views

Is magnetic reconnection reconcilable with magnetic field lines neither starting nor ending?

According to Maxwell's equations, magnetic fields are divergence-free: $\nabla \cdot \mathbf{B} = 0$. If I understand this correctly, this means that magnetic field lines do not start or end. How can ...
2
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1answer
129 views

What happens to charge during laser ablation in water?

One of my friends from lab makes gold nanoparticles in the following manner: He puts a gold plate in water (without surfactants or other additives) He fires laser at the plate After 5 minutes ...
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0answers
24 views

Are x-rays in fusion plasmas mostly from collisions with high atomic number ions?

Say you have a hot (100eV-1keV) hydrogen plasma with no impurities in it and no collisional interaction with the wall. Would this plasma radiate x-rays? X-rays are from bremsstrahlung, so could ...
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1answer
48 views

Is plasma an intermediate stage of matter? [duplicate]

Can it truly be called a stable state? Fire is stable while it has fuel but isn't it really just a transition point for solid to gas?
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0answers
50 views

Find the fraction of atoms in specific quantum state in stellar atmosphere [closed]

Consider gas consisting of hydrogen atoms at temperature about $T \sim 5 \cdot 10^6 \text{ K} \approx 431 \text{ eV}$ and concentration $N \sim 10^{11} \text{ cm}^{-3}$. I need to find the fraction of ...