According to Stefan Boltzmann Pout=e*s*A*T^4.
The greatest part of emissivity is due to the electrons temperature. If the plasma density is very low the emissivity must be low also because there are fewer electrons.
In very high pressure plasma, the emissivity must be low because plasma at high pressure reflects the emissions to the inside of the plasma.
I have measured plasma emissivity at Pulsotron-2 tests as low as 0.1% at high density (>3:1 compression with respect solid) by comparison of injection power to the plasma and also radiation power of such plasma.
Do there exist measurements and/or equations made of plasma emissivity coefficient with respect to its pressure?
Dear Javier,
I cannot be sure, but there is not such equation for the general case. The problem is that the emissivity depends on many parameters, also from the geometry of the plasma. Increasing the pressure completely changes the plasma kinetic and evolution in a way not always simple to predict. When you talk about the emissivity, I suppose you are talking about continuum radiation, that is very important in high density-high temperature plasma. I will not talk about reflection in a plasma, because it should be re-absorption of emitted photons. In the case of continuum, the dominant process is the radiative recombination/photon ionization. The ionization is proportional to the square of the electron density, while the photoionization to the neutral density. But if the density increases, the radiative recombination becomes competitive with the three body recombination (2e+A^+=A+e) which is proportional to the cube of electron density, reducing the photon emission. Moreover, increasing the pressure, you change also the energy seeding in the plasma. Therefore, the plasma itself is different. You can have regions with high energy density, surrounded by regions with low temperature.
You can estimate a law, balancing the different processes according to their cross sections and should also be adapted to your system, including the geometry. The QSS (quasi-steady state) approximation can help you, but neglects all the nonlinear effects.
Hope it helps
Dear Marcel and Gianpiero, both responses are helpful for me.
How modify the radiation the presence of a magnetic field?
If somebody heats up only ions what would be its emission power?
Dear Javier,
I'm not sure if this is of any help, but I wonder if you may find useful the open-source Atomic Data Analysis Structure (ADAS) link http://open.adas.ac.uk/adf15 which stores the PEC coefficients as a function of temperature, density etc.
For more information the ADAS website http://www.adas.ac.uk/manual.php or feel free to get in contact directly.
Dear Stuart
Thank you very much, It is really helpful: I found the radiation power for hydrogen in W/cm3.
There is also the emission of the excited ions (ADAS206)
There are emissivity for other elements as a function of density and temperature, but I do not find for isotopes. Do you know if there is any table of emission coefficients for deuterium?
I'm very pleased to hear that this has been useful.
I'm not sure if the PECs for deuterium have been tabulated, although I would imagine the difference between the two coefficients is small - do you require this higher resolution?
Well, the electron emission must be the same, but not the ion emission, as long as deuterium has about twice the mass of the hydrogen.I wrote the following excel formulas about Bremsstrahlung losses:
Useful formula and excel tables for plasma physics, plasma thrusters, fusion and particle accelerators V02
See formulas 41,42 and 43 in the "Fisica" folder:
Data Useful formula and excel tables for plasma physics, plasma t...
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