northern lights

Plasma is not a human invention: it is found in stars, in tails of comets or in flashes of lightning. Spectacular appearances of plasmas are the northern lights. The word "plasma" comes from the Greek and means "form" or "shape".

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Yes, this is the case - common distinctions are:

• Equilibrium vs. non-equilibrium plasma
  • equilibrium (or "thermal") plasma: Here the energy distributions of all particles are similar. The plasma is relatively hot. A flame is an example of an equilibrium plasma.
  • non-equilibrium (or "non-thermal") plasma: Here the energy distributions of ions, atoms and electrons differ. This kind of plasma is relatively cold. A neon lamp is a well known example of a non-thermal plasma.
    
    
• Stationary vs. non-stationary plasma
  • a stationary plasma has similar properties down to a microscopic scale. Examples are RF or microwave excited plasmas.
  • a non-stationary plasma consists of a large amount of statistically distributed streamers (single arcs). Corona discharges are an example of this kind of plasma.

CYRANNUS^® technology generates a non-equilibrium and stationary kind of plasma.

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what is the influence of the chamber wall on a plasma?

Plasmas are usually contained in a chamber, e.g. a quartz tube. Concerning the interaction between the wall of that chamber and the plasma two cases are possible:

	(1) Plasma dominated by wall interaction		(2) Plasma dominated by gas phase processes
	Low pressure and large free mean path of particles in the plasma Collision of particles with the wall is the dominating interaction in the plasma		High pressure and short free mean path of particles in the plasma Collisions of particles within the gas phase is the dominating interaction in the plasma

					Intensive plasma chemical processes due to strong interaction within the gas phase Heating of plasma through coupled power possible depending on the exchange rate of the gas
		Cooling of plasma gas at the walls Erosion of wall material Slow plasma chemical processes due to low level of particle-particle interaction

Plasma generated by a CYRANNUS^® I source is dominated by gas phase processes.

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what are the differences between direct and remote plasma treatment?

	Direct plasma process					Remote plasma process for up or down-stream treatment
	Pros and Cons: + intensive treatment, if preferred + large amount of activated species available - treatment of electrical conducting materials is limited				Pros and Cons: + moderate treatment, if preferred + treated area on material can be larger than source diameter - use of processing gas / inert gas necessary
			remote plasma above a CYRANNUS® I

The CYRANNUS^® I plasma source can be configured for both, direct or remote applications.

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what are the innovative features of CYRANNUS^® I plasma sources?

•	plasma from low pressure to atmospheric pressure: from 10-2 mbar to 1 bar
•	arbitrary type of gas for plasma generation: no limitation on Argon as process gas
•	spatially homogeneous plasma: no hot spots
•	3-dimensional plasma volume: no concentration of plasma at certain areas (even at higher pressure)
•	long term stable plasma: continuous operation for days without maintenance
•	non-equilibrium plasma (non-thermal): electron energy is much higher than ion and gas energy
•	excitation without electrodes: no contamination of plasma with evaporated material from electrodes

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are these features not already known from other sources?

It is true that some of the mentioned features are known from conventional plasma sources. However, until now there was no possibility to achieve the above mentioned properties simultaneously. E.g., plasmas at increased pressure were inhomogeneous or had only a small extension and operation time was short.

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does it make sense to use microwave plasmas for industrial applications?

Up to now microwave plasmas were limited to a pressure range below 1 mbar as soon as spatial homogeneity was required. In consequence, the processing technology depended on a batch mode. CYRANNUS^® I sources offer plasma generation up to atmospheric pressure as well as a symmetric configuration with two open flanges. These advantages allow a switch to an in-line production mode. The plasma sources are completely sealed. Customers are free to integrate the source into a given process. Connections are possible via standard flanges or with tailored adapters. These features come along with low maintenance requirements making CYRANNUS^® technology attractive for industrial processes.

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how much maintenance do CYRANNUS^® sources need?

CYRANNUS^® plasma sources are designed for long operating cycles without maintenance. Since the plasma process is excited via external coupling elements there is no direct contact between microwave coupling unit and plasma. A high reliability is given because continuous material attrition, e.g. on antennas or electrodes, does not exist. From time to time a cleaning of the plasma chamber may be appropriate. The sources´ design ensures an easy handling. The exchange of the quartz plasma chamber wall does not take more than 10 minutes.

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are there restrictions for the application of CYRANNUS^® I plasma sources?

Yes, there are some limitations for certain materials and set-ups. The energy coupling via microwaves may cause problems for the treatment of metallic materials. For such applications the electrical field distribution within the resonator has to be taken into consideration. Users should also think about remote plasma processes, were the plasma treatment occurs outside the resonator.

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are microwave plasmas environmentally friendly?

Plasma processes are environmentally friendly by nature, often they are working with pure air or oxygen. This is possible because the physical or chemical plasma reactions are based on the high particle energy and not on electrochemical potentials (like e.g. in wet chemical processes). This avoids recycling or disposal of chemical waste.

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what is the meaning of "CYRANNUS"?

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