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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747 views

Child-Langmuir space charge law for non-zero cathode potential (non-zero initial electron velocity)

I'm trying to reconcile some conflicting results that I've found in publications that address the idea of the current in a vacuum diode in the case where the cathode has a non-zero potential, in other ...
5
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1answer
187 views

Integrating Factor Solution for Plasma Wave Equation

As part of a derivation in Bernstein '58 [1] a linear first-order (eqn. (9) in the image) appears: But the general solution I would usually take (as appears in Gradshteyn and Ryzhik and checked in ...
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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: ...
2
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1answer
126 views

Difference between fusion plasma and fluorescent lamp plasmas

How is the plasma in a compact fluorescent lamp (CFL) different from a plasma in say ITER or the sun? Why does ITER need 100MK and a CFL can work at practically room temperature (apart from the ...
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289 views

Who invented the term “Coulomb logarithm”?

Who is the author of the term "Coulomb logarithm"? In fact, Coulomb logarithm was computed by Langmuir in his paper of 1928 where the term "plasma" was introduced into physics, but the term "Coulomb ...
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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A recent popular report states (beware, I believe it is not peer reviewed and this slightly smells like a PR stunt) that a private company TriAlpha has made some notable progress towards ...
3
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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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65 views

Why do rings form on microwaved CD/DVDs?

Here's a microwaved CD. As you can see, the disc has been destroyed, but there are very clear circular rings bridged with lines. Why are rings formed when microwaving discs?
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108 views

nuclear fusion scaling with reactor size

Thinking about physics of thermonuclear fusion, I have always intuitive sense, that making fusion feasible is matter of reactor size. In other words I feel like: if the fusion reactor is big enough ...
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24 views

Why do the high curvature bends in CFLs have their phosphor coating erode?

I have this pretty old compact fluorescent (CFL) bulb from several years ago still going strong. There was a period where the bulb sat unused when I moved away from home and put the lamp in storage. ...
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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} ...
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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 ...
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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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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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26 views

Why are low m,n modes more dominant?

Consider an axially symmetric, toroidal, magnetized plasma with some safety factor (q) profile. A flux surface has q=m/n where m is the number of toroidal transits and n is the number of poloidal ...
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183 views

Calculating the magnetic permeability of a known plasma

I have a plasma, of which I know the composition, temperature, exact electron/ion/particle densities. How can I then calculate a theoretical permeability of the plasma. Is this even possible? I ...
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72 views

Particle acceleration at magnetized shocks by convective electric fields?

Let us assume we have a flow of charged particles in a quasi-neutral state (i.e., a plasma) convecting at some speed, $\mathbf{V}_{sw}$ = V$_{sw}$ $\hat{x}$, and the particles have species-dependent ...
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97 views

After quantization of electron vibrations, do we need electrons anyway?

The title question is not ment in a general context, but one in which goes to the plasmon theory. In that case, how is are the statistics (boson vs. fermions) of plasmons determined? And is there an ...
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56 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 ...
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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 ...
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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 ...
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38 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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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 ...
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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?
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34 views

How does electron positron plasma act compared to normal plasma?

When an electron positron plasma is formed, will it react to magnetic fields the same way? With the gamma ray photons resulting from the annihilation, would the plasma be of greater energy? Thanks!
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46 views

Calculate energy-density of known plasma in microwave?

Let's assume I want to create a plasma in a regular household microwave similar to this home-made experiment. Although I am dealing with a small amount of mass, I assume that the addition of microwave ...
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46 views

Boltzmann factor predicts arbitrarily large numbers of electrons at high potential?

In deriving the Debye shielding length we are told that the Boltzmann factor for particles of charge $q$ is: $n_{q}=n_{0}\exp(-q\phi/kT)$ If we assume the potential $\phi$ is positive, then the ...
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71 views

Physical reason for magnetic mirroring?

I understand the mathematical derivation of magnetic mirroring, which usually starts from the conservation of the magnetic dipole moment (e.g. in a plasma). But physically: a mirrored particle is ...
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202 views

Intensive radiative heat transfer in very hot gas ( >5000K, gas core nuclear reactor related )

The question: At temperatures above ~5000K are not stable any solid or liquid materials or even more complex molecules (such as fullerenes and Polycyclic aromatic hydrocarbons) which emit/absorb ...
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19 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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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 ...
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22 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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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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32 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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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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52 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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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 ...
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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 ...
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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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57 views

What about the Electric energy density of the toroid?

But what about $U_{E}$, the electric field energy density?
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25 views

What is the effect of a magnetic field on a plasma speaker?

I have been doing some research for the past couple years investigating the effect of a magnetic field on a plasma speaker. More specifically, if you apply a relatively uniform magnetic field in no ...
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35 views

Production of Inductively Coupled Plasma

I am working on an experiment hat requires the usage of inductively coupled plasma, but unfortunately, I do not have any equipment at the moment that can produce such plasma, and I really need your ...
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44 views

Betatron vs Fermi acceleration

According to the reference below, the plasma in a planetary radiation belt increases its temperature anisotropy through radial diffusion; temperature perpendicular to the background magnetic field ...
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30 views

Finite Value of Cross Section of (Scattering/Absorption) of Localized Surface Plasmon at Resonance

According to textbook written by Stefan A. Maier, ch.5, p.70, cross section of scattering and absorption are defined as: $$C_{sca}=\frac{8\pi}{3}k^4a^6 ...
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171 views

Electrostatic ion thruster neutralizers

All electrostatic Ion thrusters have a neutralizer electron beam, but why are they required? Is avoiding the accumulation of negative charge the only reason? I would've thought that the main reason ...
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111 views

Magnetic fields in plasma at equilibrium

I'm wondering if it is possible to have a plasma reach an equilibrium state where no more entropy is produced but it still has frozen-in magnetic field lines. The problem is the field lines have a ...
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59 views

Fusion plasma compression with liquid metal

General Fusion plans to use an imploding shockwave of molten lead to compress a magnetized plasma "spheromak" target in order to make it burn more efficiently. How come the lead does not quench the ...
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54 views

Under what conditions is it possible to ionize atoms using an electron gun?

Using the electron bombardment method, if I wanted to ionize, for example, Xenon gas electrons with an electron gun, under what conditions is it possible to do so? (Heat, pressure?)