Look at this review, may be you'll find out the answer.

P J Bruggeman et al. Plasma Sources Sci. Technol. 23 (2014) 023001

You can measure the emission spectrum and use specair program or other alternatives. A large body of literature exists around this.

I suggest you select some emission line of the gas plasma and measure their intensities. From the line intensities you can draw a so called Boltzmann plot , line intensities against upper level energies. This is well established technique and you can find more details in a number of papers on Laser Induced Breakdown Spectroscopy (LIBS). These papers are normally published in Spectrochemica Acta part B; You can just write the name of Ominetto on the net and you will find his very informative papers on LIBS.

The quick way is just consider two spectral lines of same gas which lie in the nearly the same wavelength region but their upper levels are different. There intensities should follow the relation:

I1/I2 = (g1/g2) .EXp(Del E/KT)

From this relation you can quickly deduce the plasma temperature.

Aslam

Muhammad Aslam Baig

thanks Dr. Aslam Baig. i think from this formula i can estimate electron temperature in plasma. i calculate this formula and i obtain Tg=10000K. it is too much for my setup. i guess the gas temperature is about 300-1000k. so i think the best way is Boltzmann plot. may you send me some reference of this method?

Dear Shahab Salimi,

Two papers are attached. I am sure you will get the answer for your quarries.

with best wishes,

Aslam

N.N. Misra

Hi Dr. Misra. thanks for your answer. may you send me this app with email? or give me the link?......thanks alot

Using the Boltzman equation or Spacair are good for plasma containing molecular component. In this case, rotational structure of molecular bands is recorded.

For atomic plasma, spectral line profile may be used. See, e.g., the paper by Pipa et al. Applied Physics Letters, 2015, v.106, 244104

Yuriy Z Ionikh

thanks Dr. Ionikh. but i could not reach the Specair application. i have an question, Boltzmann plot use Doppler velocity? and on the other hand can i measure gas temperature?...i want it to calculate H/H2 and i need Tg.

Look at this review, may be you'll find out the answer.

P J Bruggeman et al. Plasma Sources Sci. Technol. 23 (2014) 023001

@Shahab: You have to purchase the license for Specair; it used to be free but not any more. Alternatively, you can use the open source python program, massiveOES written by Dr Jan Vorac et al, MUNI, CZ.

For hydrogen plasma I would suggest to measure Fulher bands of the H2.

It requares relativly good resolution and sensetivity of the spectrometer, but it would allow to estimate the ratio H/H2 experimentally.

Article On determination of the degree of dissociation of hydrogen i...

Article On determination of the degree of dissociation of hydrogen i...

Andrei V. Pipa

Thanks Dr. Pipa. I exactly follow these artile. But spectrometer resolution is about 0.1nm. I think we have not enough resolution to determine this fraction. By the way formula that introduce in these article would be usefull if you know the gas temperature. So i should determine it.

Shahab Salimi:

You can try our package, as Dr. Misra proposed:

https://bitbucket.org/OES_muni/massiveoes

If there is some obstacle for you, let us know. We may find a bit of time to improve the programme, depending on the complexity of the change required.

Btw., we do not have a database for H2, but if you are willing to build it, we can provide support.

https://www.researchgate.net/profile/Jan_Vorac

Thanks Dr.Vorac. i would try it immediatly and will report you result.

0.1 nm resolution can be sufficient, unfortunately different people define the resolution in different way. However Doppler broadening is inaccessible and if it is no impurities of the N2 (or other molecules) then the Fulher band would be the only information source for the gas temperature. See my dissertation attached, page 93-94, an examples of the measured spectra. It should be possible to resolve Q1 line (3c22a2Q1) but Q3 line can be overlaped with 3c12a1Q9, but Q5 line should be again Ok. I think the estimations of the Tg should be possible. Do not forget a second order filter during spectra acquisition. See pages 55-58 for details.

Dear Jan Vorac,

I enjoyed watching the videos of your excellent program to fit molecular bands and to find plasma temperature. Good job.

Have you developed a similar simulation program for the Atomic Spectra and to determine the plasma temperature and other plasma parameters?

Particularly , I am interested to simulate a self absorbed line profile and to extract the plasma temperature and electron number density. I will appreciate if you help me.

Aslam

[email protected]

thanks for all

i found that for determine gas temperature at first we should have spectrometer with high resolution. from the papers and books that you send i consider two ways to measure gas temperature.

1. use Fulcher band and relative intensity as Dr.Pipa send in page 55.

2. use Doppler Broadening FWHM as discuss in paper that Dr.Ionikh send.

pleas suggest more method that you know.

Best Regards

Shahab,

Actually I've meant the collisional line profile rather than the Doppler one. In the latter case the profile may be much wider and spectrometer of moderate resolution can be used as is described in that paper. But for your case of H2 plasma this approach is not applicable. Doppler width is ok, but spectometer with very high resolution or even Fabry-Perot interferometer are required. So I believe the Fulcher is the best chice.

Shahab,

you can use Langmuir probes technique for determination of gas temperature in plasma. there are some links for detailed study

http://www.chm.bris.ac.uk/pt/diamond/stuthesis/chapter5.htm

https://doi.org/10.1002/ctpp.2150300202

Laser-induced Rayleigh scattering can be a good choice for measuring gas temperature of non-thermal plasmas

Jiajian Zhu

you right Dr. Zhu but our method is OES and we don not have this technique.

thanks

That is pretty difficult. AOptical methods aren't great for obvious reasons (like IR thermometers), and of course a metallic thermocouple is not an option.

I'd recommend this. If it's a jet, use some high-boiling liquid (no more than 100 uL) exposed to it for about 1 min. Since the liquid won't evaporate, it will then just be heated up by the gas. And using a thermocouple in the liquid /immediately/ after the exposure is what you need.

Hope this helps.

I think at first, we should know what kind of plasma do you have?

Hot or Cold?

In atmospheric conditions or vaccum?!