Atmospheric pressure, non-thermal plasma jets are increasingly used in many processing applications, due to their combination of inherent plasma stability and excellent reaction chemistry, which is often enhanced downstream of
the plasma source.
It is important to underline, that due to the high industrial demand for plasma
technologies and the resulting competition between system manufacturers, many of these manufacturers come to the market with closed box plasma systems (typically a plasma generator and its matching network in the single box), which
cannot be opened due to warranty issues. This leads to the situation where the only plasma diagnostic techniques available are optical techniques. Under these circumstances it is very challenging to develop an experimental approach, which would give a fundamental explanation of the impact of plasma physics on atomic physics, e.g., the role of metastable atoms, resonance energy levels, triplet and singlet energy scale, life time of electrons in an excited atom/molecular state, etc.
what do you exactly mean by "the energy of the beam"?
do you mean the excitation energy, the thermal energy the kinetic energy of the particles, the potential energy from the electric fields involved, the kinetic energy of the gas flow, ...?
Hi,
What is your mean by measuring the beams energy? I sink you want to measure the temperature? isn'nt it? If it it is so, please write me to [email protected]
It would be nice if we can think like:
We will put a substrate at a short distance apart from the jet (plasma and gas flow) output. So, how much thermal enegy or power will be imparted on the substrate?
How can we measure the electron temperature, plasma density in a simple way, the potential energy from the electric fields involved, etc.
This is quite a difficult task and is topic of current reseasch efforts.
First of all, it must be said that for a plasma jet propagating freely, without interaction with a substrate, there will be no "beam" of ions with a defined energy, but actually it will be better described by a distribution of energy. When a substrate is put in contact with the jet, an accelerating sheat may be formed, and the ion energy distribution function may be distorted. So the first thing one must have in mind in this case is that what should be measured is the ion energy distribution function (IEDF). It may happen to be sharp and peaked, but this is not always the case.
The second part to this answer is more practical: can I measure this IEDF? Yes, it is possible, and I know at least one method, but which have its drawbacks. The plasma jet may be put in contact with a very small sampling orifice, whose diameter should be not larger than 10 \mu m. The plasma particles are collected and then expanded trough some differential pumping stages, focused and accelerated into a energy analyzer in a UHV environment. In order to analyze only helium particles, one should place a mass filter after it. A SEM detector would suffice to count the particles. Many details and cautions must be taken when building such apparatus or even using commercial equipment, such as Hiden products. One of the main drawbacks of this apparatus is the fact that the sampling material interacts with the plasma, producing a sheath and distorting the IEDF. One may try to use a dielectric material similar to the substrate of the application of interest.
Any other idea or method to measure the plasma IEDF would be welcome and would surely give an important contribution to the field of plasma diagnostics.
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