What is Plasma: Definition and 675 Discussions

Plasma (from Ancient Greek πλάσμα 'moldable substance') is one of the four fundamental states of matter, first systematically studied by Irving Langmuir in the 1920s. It consists of a gas of ions – atoms or molecules which have one or more orbital electrons stripped (or, rarely, an extra electron attached), and free electrons.
Plasma can be artificially generated by heating a neutral gas or subjecting it to a strong electromagnetic field. The presence of free charged particles makes plasma electrically conductive, with the dynamics of individual particles and macroscopic plasma motion governed by collective electromagnetic fields and very sensitive to externally applied fields. The response of plasma to electromagnetic fields is used in many modern technological devices, such as plasma televisions or plasma etching.Depending on temperature and density, a certain amount of neutral particles may also be present, in which case plasma is called partially ionized. Neon signs and lightning are examples of partially ionized plasmas.
Unlike the phase transitions between the other three states of matter, the transition to plasma is not well defined and is a matter of interpretation and context: Whether a given degree of ionization suffices to call the substance "plasma" depends on a specific phenomenon being considered. In other words, plasma is a matter which cannot be correctly described without the presence of charged particles taken into account.
Excluding dark matter and the even more elusive dark energy, plasma is the most abundant form of ordinary matter in the universe. Plasma is mostly associated with stars, including our Sun,
and extending to the rarefied intracluster medium and possibly the intergalactic regions.

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  1. M

    What does magnetically sealed possibly mean?

    I remember one of my favorite parts of the original Star Wars movie was when Luke, Leia, Chewie and Han jump into the trash compactor. Han tries to blast his way out and the blaster bolt ricochets off the walls of the compactor until it eventually hits a piece of garbage. Luke screams “WILL YOU...
  2. A

    Why does a plasma ball emit light?

    Is the cause of the lighting due to the impact of electrons with the nucleus
  3. R

    Why can't we simply use an atomic bomb to get the fusion working?

    why can not simply explode an atomic bomb inside a recint with plasma and hydrogen so the temperature and power generated will make the fusion working
  4. environes

    A Is it possible to obtain excess energy from a Townsend discharge?

    Let us assume a continuous flow of gas that can be ionized between the electrodes where an electric discharge is generated. According to the principle of conservation of energy, energy cannot be created or destroyed, but it can be transformed from one form to another with losses, e.g. in the...
  5. Zarude22

    The Saha equation (degree of ionization in plasma)

    I tried to understand the equation and plug in the numbers, but I just don't get how that is supposed to give us a ratio (with no units!), when it only has the temperature/energy to the power of 3/2 and that multiplied by m^3. Other units (in the exponent of e) cancel each other out. Thank you.
  6. I

    I Doubling Ionization of Tungsten: Effects on Energy?

    Lets say that i have i mole of tungsten atoms. They are all ionized, only one electron is removed from each atom. If i accelerate this mole of tungsten atoms through one electron volt, i would get 96.48 kj. If the mole of tungsten was doubly ionized, two electrons removed from each atom, and...
  7. niranama

    A Plotting Potential in Plasma Sheath

    Hi! everyone. I'm looking to plot potential of quasi-neutral plasma as a function of length. I know that plasma potential will drop at front of the wall from particle acceleration by electric field. I assume plasma is an electrostatic and cold (less collision). However, I'm trying to plot plasma...
  8. D

    I Quark Numbers in Quarks-Gluons Plasma: Avogadro's Number

    Why quarks numbers of the three colors where exactly equal in the initial quarks-gluons plasma? Seeing the Avogadro number, even a 10E-20 additional excess in one color should give a lot of free quark tracks in bubble chamber.
  9. A

    B Pinched plasma inside a neutral beam injector

    Let me start this off with saying I am just a uneducated idiot, But after reading about Zap Energies sheared flow pinch reactor I was wondering if you could use a similar concept in a neutral beam injector? Like could you first compress and heat the plasma inside of a NBI using a pinch, then...
  10. gary808

    I Mercury as a plasma at 150 Kelvin

    I was reading up on a theoretical engine employing the following, “Mercury plasma pressurized at 250k atmospheres, at a temperature of 150 degrees kelvin (-123° C), and swirled within its accelerator to 50k RPM.” Does pressurizing mercury so much somehow allow a plasma to form at such sub-zero...
  11. Astronuc

    Plasma thruster - plasma instability in magnetic nozzle

    Plasma instability may be a solution for magnetic nozzle plasma thrusters https://phys.org/news/2022-12-plasma-instability-solution-magnetic-nozzle.html Kazunori Takahashi (Tohoku University), Christine Charles (ANU, Canberra, AU) & Rod W. Boswell (Tohoku University) Wave-driven electron...
  12. redirmigician

    I Acceleration in an electron field

    I read something about accelerators using nanotubes. I am a little concerned about the design mentioned in the "High Density with Perpendicular Carbon Nanotubes" part of this paper(https://doi.org/10.3390/photonics8060216). Can wakefield acceleration be done in an electron field? Or maybe I...
  13. redirmigician

    B Plasma recovery at wakefield accelerators

    Is it possible to keep the plasma ionized almost indefinitely. No additional heating is required.
  14. redirmigician

    I Can surface plasmons be used to build GeV gamma-ray lasers?

    I read a paper about coherent surface plasmon amplification by free electron pumping in an article a few days ago. It seems to work as some kind of free electron laser-like light source, and I wonder how high the energy of photons can go in this way. Also I read in another paper about...
  15. B

    I Separation of Plasma into positive nucleus and negative electrons

    Im wondering if plasma is possible to be separated into a positive nucleus and negative electrons and contained within a magnetic bottle ? If possible, what is the most efficient method of achieving it ?
  16. tarakmytar

    I Water converted to plasma -- how does this work?

    In its path to the exit it is, disassociated, and still trapped in this enclosure with only a path forward. So now it is in two forms of gas, so the pressure of the expansion in the enclosed enclosure and now traveling at high speed towards the exit, and most likely ionized. It is then subjected...
  17. ergospherical

    How the charge imbalance in a plasma changes with time

    I put the net charge density ##\rho_q = e\delta## so that ##\nabla \cdot \mathbf{E} = e\delta / \epsilon_0##, then I tried Maxwell IV:\begin{align*} \dot{\mathbf{E}} + c^2 \mu_0 \mathbf{J} &= 0 \overset{\mathrm{div}}{\implies} e\dot{\delta} + \nabla \cdot \mathbf{J} = 0 \end{align*}but this...
  18. C

    A Penetration depth of a ion beam coupled with an EM wave

    A Ion source is a device that allows creating ion beams (e.g. argon ions) and to project them outside the device, for example to be further processed by a particle accelerator, or to irradiate materials or biological tissues etc. Now, suppose the ion beam is coupled with an EM wave, especially...
  19. LUFER

    What is the Electromagnetic Cross Section in this plasma deposition process?

    What is Electromagnetic Cross Section? (shock section) Hello, I have a question regarding the manufacturing process of electronic components in the case of the silicon deposition and corrosion process. My biggest doubt is the behavior of the plasma interacting in the reactor, I don't know if...
  20. A

    Idiot with a Vision: Using a Diverter to Purify Plasma

    Let me start off with saying I am just a idiot with a high school level education (and a learning disability ). But i have a idea of using a diverter with a plasma actuator equiped, to generate a stream of negatively charged electrons to attract spent alpha particles and impurities. Tuned to...
  21. Jd1431

    I What makes a plasma collisionless?

    Hi, I'm trying to understand what determines whether a plasma will be collisionless or collisional. I understand that a diffuse plasma with large mean free path will be collisionless but I don't really understand it from an electromagnetic point of view
  22. Spinnor

    I Back of the envelope estimate, energy flow in a box of plasma

    Say we look at a spherical region of the sun where energy is mainly transported by radiation. Say this happens between some particular radius R and R + dr. Let the temperature at R be giving by T(r). At this particular radius let the gravitational acceleration be a reasonably well know function...
  23. D

    How do plasma membranes prevent ions from diffusing?

    Hi everyone Explanations of diffusion that I've seen mention that the polarity of phospholipid layer stops ions from diffusing without specifying how. I'm assuming that ions with the same polarity as the membrane will be repelled. Would it be correct to say that ions with the opposite...
  24. JD_PM

    How to determine the minimum grid length | Numerical Plasma Physics

    Summary:: I am learning particle-in-cell (PIC) python 3X code. PIC currently represents one of the most important plasma simulation tools. It is particularly suited to the study of kinetic or non-Maxwellian effects. I am learning particle-in-cell (PIC) python code. PIC currently represents one...
  25. mcas

    Evaluate reflectance of an aluminum mirror

    Note: for some reason frequency on this lecture is indicated by \omega. I wanted to calculate the reflectance using one of these equations that were given to us during the lecture: R=1 where \omega < \omega_p...
  26. naviakam

    I What Specifications Are Needed for a Plasma Device Power Supply?

    In a plasma device, the plasma is generated by applying high voltage in a gas. What are the specifications for the power supply producing such plasma? The output must be AC or DC? Pulsed or not? What are the current, voltage, etc...?
  27. Leo Liu

    How does a pulsed plasma thruster work?

    I really can't get my head around the concept of pulsed plasma thruster. All I know now is that it utilizes ##\vec F=q \dot {\vec r}\times \vec B##. Could someone explain the mechanism to me, please? Thanks!
  28. R

    B Which lines are the quark-gluon plasma?

    I'm curious what are those lines? Which one are the quark gluon plasma?
  29. B

    Trouble with Plasma Frequency Calculation

    This would appear to be a straightforward algebra problem, but it just doesn't pass the smell test for me. The issue might be with the number of electrons per cubic meter, as that was calculated in a previous problem, so let me know if that number seems wrong. My plasma frequency (##\nu##) not...
  30. Shreya

    Understanding the Plasma Confinement in Tokamak Reactor

    Please be kind to help. How is an electric field formed due to toroidal magnetic field? How does the introduction of a poloidal magnetic field confine the plasma? Please answer in the context of Nuclear Fusion Reactor (tokamak).
  31. P

    Current generated by plasma of uneven density in a Magnetic Field

    I am only asking about part (b)(i) and (b)(ii). Below is the explanation for (b)(i). What is going on in the above? I understand up till the 3rd line, about the left/right hand circular motion. What is the "upward motion" the solution mentioned? Is it suggesting that ions are moving...
  32. Shreya

    Plasma Experiment Involving Magnetic Fields

    I want to perform an experiment to show that magnetic fields can control plasma. (Can even be a slight repulsion) Please Suggest one. I have no idea where I can obtain plasma - I have access to candle flame (though it's not a proper plasma) & fluorescent lights. I have a permanent magnet (not a...
  33. Twigg

    What's the deal with plasma physicists setting heat cap. ratio to 3?

    This has persistently bugged me in my intro plasma course. They keep using ##\gamma = 3## aka ##N_d = 1## (where ##N_d## is the number of degrees of freedom in the molecule) as an approximation. See for example, the Bohm-Gross dispersion curve. I can tell you from deriving this that the factor...
  34. G

    Plasma ball and effects luminous

    Are the effects luminous we see in plasma ball come from electron or ions ? Or the two ?
  35. G

    Could you point me to interesting videos about plasma balls?

    Could you point me to interesting videos about plasma ball?
  36. G

    Question about Plasma Ball (can I leave it running all night?)

    Hi there! I wanted to know if i can leave the Plasm Ball turned on all night in my room without any problem. Thanks in advance!
  37. B

    Is this an idea or a device? (fusion plasma confinement configuration)

    The idea itself is to create in a toroidal chamber a spiral-shaped plasma filament with a singularity in the form of a ring of rotating plasma, in which the concentration of ions and the duration of nuclear interaction increase during electrostatic compression. For this, it is proposed to wind a...
  38. H

    I Transparency of a gas compared to a plasma

    I imagine an empty region of space, in between stars, or even galaxies. This void is filled only with a uniform distribution of hydrogen particles. I won't specify how dense this field is, but I would like to know which is more transparent to photons, a gas of hydrogen atoms, hydrogen...
  39. G

    I Electrostatic waves in a plasma

    I’m having A bit of confusion regarding this. In a plasma by turning on an electric field ,wouldn’t this cause an oscillation of the electrons about the ions,effectively a oscillating dipole thus inducing a magnetic field, by amperes law? My text (plasma physics by F.Chen )has curlE =0 I’m not...
  40. F

    Tokamak question: What happens when you shine a laser on the plasma?

    I really enjoy learning strange facts and while i would never assume to be a "Smart" person i do have the power to ask. So with a plasma fusion reactor like the tokamak or any other they have a viewing window to see the plasma bound in the toroidal magnetic field so what would happen if you...
  41. J

    What do the different colors of plasma in spark gaps mean?

    Hi, I am looking at videos of spark gaps and see that there are different colors of plasma. I really should've been a physicist because this may be fundamental, but I'm wondering what the different colors mean? I have seen purple and white. My guess is that white is a higher energy discharge...
  42. brainbaby

    Troubleshooting my LG plasma TV - no picture display

    Hi friends, Let me brief, long story short.. I am working on an LG plasma TV model 42PQ30R. The fault is no display. The tv is turning on, the blue led is working, however there is no standby (red light), tv automatically going in run mode (i.e blue led) Note: sometimes gets off automatically...
  43. S

    B What is Plasma? Is Tungsten Vapour a Gas or Plasma?

    What is "plasma"? How is a fluid measured to be either a gas or a plasma? Mercury boils at 359 Celsius (632 Kelvin). Mercury vapour is poorly conductive, little ionized (incidentally - monoatomic) and generally defined as a gas. However, tungsten boils at 5930 C (6203 K). Photosphere of Sun...
  44. Thomas Sturm

    B Amount of Plasma [g] in nuclear fusion designs

    Hi everyone, I am trying to figure out the following question: What is the typical mass of the plasma (in typical working configuration) in current nuclear fusion reactor designs? https://en.wikipedia.org/wiki/ITER: "...plasma volume of 840 cubic meters..." So all I need is the plasma density...
  45. A

    A Collision-dominated plasma (stellar coronae)

    The paper is "Helium-like ions as powerful X-ray plasma diagnostics" Proceedings of “X-ray Astronomy 2000”, Palermo, Sep. 2000 ASP Conference Series, Vol. TBD (in press), 2001 R. Giacconi, L. Stella, S. Serio [Mentors note: arXiv link at https://arxiv.org/abs/astro-ph/0012218v2] By the way, why...
  46. Fnux

    A Unveiling the Mystery of ε(∞): Exploring Its Role in Plasma Dielectrics

    During the derivation of the dielectric function of a plasma (Kittel 8. ed. chap. 14), this somewhat mysterious quantity ε(∞) is inserted to account for the high-frequency dielectric contribution of the ionic background. In some ways, I see how this is related to the "external" charge density in...
  47. K

    I What is the Ideal Plasma Pressure for Successful Fusion?

    I am trying to wrap my head around the concepts in fusion. They talk about ion density, but I don't ever see that expressed in pascals, for instance. Why is that? I understand that confinment time is also important for successful fusion and that they go hand in hand, but I'm not concerned about...
  48. E

    Traveling to Mars with plasma rockets

    Plasma-powered rockets could reduce the travel time to Mars by roughly half. https://theconversation.com/traveling-to-mars-with-immortal-plasma-rockets-58705
  49. patrykh18

    Physics Internship possibilities: Plasma physics

    Hi guys. I'm a third year physics student. Next year I'll be in my final year. I'm interested in studying fusion in the future. Unfortunately I have not done plasma physics as part of my degree so I don't know much about it yet. However I'd like to do an internship abroad this summer. Ideally I...
  50. patrykh18

    What Are Suitable Plasma Physics Project Ideas for an Undergraduate?

    Summary:: I am looking for topics to give a presentation on. Hi everyone. If this is in the wrong section feel free to move it. Anyway, as part of our lab course, on top of doing experiments we will also have to prepare a 20 minute presentation on a chosen topic on physics. This is not like...