plasma Definition and Topics - 159 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. C

    Plasma in a Solenoid

    ∇p=j×B (eq. 1) K=nI BSolenoid=μnI⇒μK (eq. 2) ∇p=-2p0r/(a2) (eq. 3) Combining these three equations: j=-2p0r/(a2μK) (θ hat direction) Feel like this is too simple and might be missing a step any help would be much appreciated!
  2. R

    Magnetic Mirror Problem

    a) I know the invariants are $\mu = \frac{0.5*m*v_{perp}^2{B} $ and $J = v_{parallel} x b) I used the invariance of $\mu$ to get the following equation: $$ v_{perp}^2 = v_{perp,0}^2(1+\alpha(t)^2 z^2) $$ I am thinking of using the Lorentz force to get $v_z$, but I'm not so clear on how to go...
  3. T

    Plasma ball radio-frequency energy

    I read Wikipedia's description of how a plasma ball works. Question: What kind of energy is the "radio-frequency energy from the transformer"? Is in the form of electric field energy, magnetic field energy, or both? Thank you! (from Wikipedia)... Although many variations exist, a plasma lamp is...
  4. T

    Energy released upon ionization of different gases

    Hi, I am interested in plasma physics. I understand that once a gas (say Argon) is ionized, light (electromagnetic radiation) is emitted. This is clearly observable from the coloured glow of the gas when it is in a plasma state. Where does the energy for these electromagnetic rays come from? Is...
  5. hagopbul

    At NIF what is the shape of the 1st stage of the plasma

    Hello all: I was wondering what is the shape of the plasma at Nif ,is it spherical ? I start to wonder that it may be spindle shaped ,or fusiform shaped . Best H
  6. T

    New approach to stabilize fusion plasmas

    https://phys.org/news/2019-01-scientists-stabilizes-fusion-plasmas.html By applying more RF power to the unstable 'bubbles' that form in the plasmas.
  7. Javier Lopez

    I Ion sensor for 1e20 ions/m3 density

    What kind of ion sensor can I use in the range 1e19to 1e22 ions/m3? (corresponds to 0.1 to 5 pascals if non ionized) Does it exist any sensor based in the charge capacity?
  8. Samuel Williams

    Are longitudinal magnetic waves possible?

    Homework Statement Are longitudinal magnetic waves possible? Give reasons for your answer. Homework Equations Working with Maxwell's equations, Lorentz force, electrostatic and electromagnetic waves in plasma. The Attempt at a Solution No idea whatsoever. I believe it is possible based on...
  9. QuarkDecay

    Plasma Pinch Pressure

    Homework Statement Prove that in an MHD equilibrium state in a pinch with flux and Bθ(r) and Bz(r), the equation for pressure is; d/dr(P + B2/8π) + Bθ2/4πr - ρ( u2θ/r)= 0 B is the total Magnetic field, uθ(r) the velocity of plasma, ρ= density, and solving in a (r,θ,z) system Homework...
  10. QuarkDecay

    I Gas density and plasma

    In general, when we say that in a fermionic gas the higher its density, the better we can consider it to be a plasma instead of gas?
  11. QuarkDecay

    A Velocity Drifts of proton-muon gas

    When do we use the equations of curvature drift ( ΔΒ⊥Β) V∇B= ±1/2u⊥rL (B x ∇B)/B2 and the general VF= c/q (F x B)/B2? For particles like muons and protons, do they need different equations to calculate a gas' drift velocity, when the gas is made of protons or muons instead of electrons? Am I...
  12. QuarkDecay

    Electron Gas (Plasma) to Muon

    When do we use the Boltzmann equation for density in a Fermi plasma? n in [cm-3] and when do we use the ρ=m/V, ρ in [Kg/m3 ] (this is not an example, I just added the equations to make my question more understandable) Is the ideal gas only when we have electron and ions? Is the Boltzmann...
  13. QuarkDecay

    Electron Plasma to Muon/Proton

    Homework Statement Cylinder electron gas with density of ne= 1010 and radius or r=1cm is inside magnetic field of B=104 Gauss. If we change the electron gas with (i) muon gas (ii) proton gas does the Drift Velocity change? Homework Equations [/B] Boltzmann equation of density...
  14. Dan Jenson

    E Field at a Glow Discharge Tube Cathode

    I am trying to understand the "strong" negative E field in the Aston Dark Space in the thin region close to the cathode or else even the cathode surface. See the diagram at: http://www.glow-discharge.com/?Physical_background:Glow_Discharges My question regards the "Electrical Field E" graph...
  15. P

    Probability per atom and per second for stimulated emission to occur

    Homework Statement We are investigating hydrogen in a plasma with the temperature 4500 ºC. Calculate the probability per atom and second for stimulated emission from 2p to 1s if the lifetime of 2p is 1.6 ns Homework Equations ##A=\frac{1}{\Sigma \tau}## $$A_{2,1} = \frac{8*\pi *h *...
  16. T

    I Calculating the curvature drift in a plasma

    How do i get this equation, $$\frac{db}{dl}=(\hat{B}.∇)\hat{b}$$ This equation is a vector whose direction is towards the centre of the circle which most closely approximates the magnetic field-line at a given point, and whose magnitude is the inverse of the radius of this circle. However I...
  17. W

    Phase relation between the electric & magnetic fields in a plasma

    Homework Statement So I have got the question below. I am asked to find the phase difference between the electric field and magnetic field of electromagnetic waves traveling in a plasma, using the electrical conductivity expression. Now I have found the frequency of the waves and I know that...
  18. Kiwimaster76

    I How does plasma act outside of a containment field?

    If you were to have some way to remove plasma out of a tokamak or stellarator, how would it act? I realize there's basically no way to actually remove plasma from those machines, but I'm curious how plasma would act in the actual atmosphere. Would it act like a plasma cutter? Would it stay...
  19. J

    Enthalpy of fusion/vaporization/sublimation to a plasma?

    I may be grossly generalizing the principle, but is there a way to calculate the energy needed to transform a solid/liquid/gas into plasma? Information is easily found on enthalpy of fusion/vaporization/sublimation, but I couldn't find anything regarding transforming to the 4th state of matter...
  20. Ryan Doucette

    Nuclear Fusion: Electron Thermal Transport Terminology

    I am an undergrad physics major in my final semester currently taking Intro to Thermodynamics. As a final project, each student must choose a topic related to thermodynamics that is more advanced than what is covered in the curriculum and write a paper and present our findings to the class on...
  21. Mzzed

    I Interpretation of spatially dependent convective derivative

    <Moderator's note: Moved from the homework forum.> Homework Statement The following equation is one of a few equations that describe a plasma model. The left hand side is the part I am having trouble with in that I can't seem to visualise what (V dot delV) actually does. My physics teacher has...
  22. chandrahas

    Do force drifts occur in highly collisional plasmas

    I've read on wikipedia that the force drifts of the guiding centers off particles in a magnetic field also occurs in cold plasma. But does it occur in a cold plasma (Partially Ionized ) in which the mean free time is less than the gyro frequency time? I thought that the drift were present...
  23. C

    Does electron gas in metals experience viscosity?

    Does electron gas in metals experience viscosity? Also, does highly charged plasma experience viscosity?
  24. S

    I Can anyone help with this satellite question?

    I must find parameters for equation [1] in this link http://onlinelibrary.wiley.com/doi/10.1002/jgra.50543/pdf for satelite in height from 100km until 300km. Have to use IRI and IGRF. Any help with answer?
  25. EL_bob

    Magnetic assisted rocket engine

    Hello everybody! I have been thinking about something for a while now. I would like to make a magnetic nozzle for a rocket engine. Basically, I would like to ionize the hot and high pressure gaz in the combustion chamber and then use a strong magnetic field to adjust the nozzle throat...
  26. Jayant Dabas

    Can we create femtosecond laser instead of buying it

    Is there a possible way to redesign femtosecond lasers to reduce cost?
  27. GurfX

    Extreme heat/plasma thruster

    My knowledge suggests when gasses are heated rapidly, they also expand due to the new energy in the gas. Is it possible to create a thruster that is able to lift 10kg via electric heating? The thruster would allow cold air to enter the chamber, where it would then be super-heated & ejected as...
  28. T

    Did i calculate the V/A/R of a plasma arc properly?

    Hello there! So i am currently sitting in my EME class and have nothing to do, so i decided to try spit-balling the V/A/R of the plasma arc my Tesla Lighter produces. note that i did not physically take it apart, and my goal was just to get a rough estimate for the arc itself or at least get a...
  29. T

    Electric field due to charged plates moving through a plasma

    Hi folks, this is not an actual HW question, but rather one of personal interest. I'm basically trying to understand your classic idealized parallel plate capacitor, but moving face-on through a plasma. 1. Homework Statement We have a diffuse neutral plasma made of free protons and electrons...
  30. Sharkey4123

    I Debye Length of a plasma

    The debye length is the effective length over which electrostatic potential disturbances are "screened out" in a plasma. So if I drop a charged point particle in a plasma, then I expect after some Debye Length, D, from this point charge, I can see no difference between any other point in the...
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