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Indula
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I have observed a layer like structure (made of plasma) in a cold plasma and wonders what causes it. Following image shows the observation.
What's the pressure and kind of gas you are using? At lower pressures current contribution due to high drift velocities of charge carriers may be important. Change the frequency and observe what happensIndula said:Yes there is a high electric field. About 15kV of sinosoidal voltage is applied. Frequency was about 23 kHz.
Indula said:wonders what causes it.
Vanadium 50 said:Why don't you describe what you are doing in some detail? If you let information out slowly, you will only get your answer slowly.
zoki85 said:What's the pressure and kind of gas you are using? At lower pressures current contribution due to high drift velocities of charge carriers may be important. Change the frequency and observe what happens
Indula said:Yes. What I'm trying to do is to build a sensor array that would measure the plasma density of the plasma inside. So I have implemented a circular disk like plates inside the chamber and I'm measuring the current sensed by each plate.
Then these are the striations stimulated/supported in low pressure argon by RF fields.Indula said:Here I'm using Argon gas and the gas pressure is about 500 milliTorrs. Actually the gas pressure changes since I'm keeping the vacuum pump working the whole time.
Thank you for your detailed explanation.Fred Wright said:I have the following observations due to my experience with thin film coating using a magnetron sputtering machine. If an inert gas such as argon is included in a cathode gas tube, the free ions and electrons are attracted to opposite electrodes and a small current is produced. As voltage is increased some ionization is produced by collision of electrons with gas atoms, named the "Townsend" discharge. When the voltage across the tube exceeds the breakdown potential, a self sustaining glow discharge occurs - characterized by a luminous glow. The current density and voltage drop remains relatively constant, the increase in total current being satisfied by the area of the glow increasing. Increasing the supply voltage increases current density and voltage drop, this is called the "abnormal glow region". Further increase in supply voltage concentrates the glow into a cathode spot and arc discharge is apparent.
Once the condition for a sustained discharge is met, the tube exhibits the characteristic glow discharge, so called because of the associated luminous glow. It has been established that free ions and electrons are attracted to opposite electrodes producing a discharge - however for a discharge to be self-sustaining requires regeneration of the electrons by the positive ion bombardment of the cathode. This produces secondary electrons and enhances ionization. The resulting positive ion excess creates a positive space charge near the cathode. The voltage drop experienced is termed the "cathode fall". If the discharge is established in a long narrow tube it exhibits a glow pattern in five regions of the tube. They are, proceeding from cathode to anode:
1. "Cathode glow" (intense and narrowly distributed).
2. "Crookes dark space" (no glow) .
3. "Negative glow" ( intense and broadly distributed).
4. "Faraday dark space" (no glow).
5. "Anode glow" (not so intense and broadly distributed).
The positive ion density in the "Crookes dark space" is very high; as a result a significant voltage drop is experienced between it and the cathode. The resulting electric field accelerates the positive ions which produce secondary electron emission from the cathode. These electrons accelerated in the direction of the anode cause ionization, generating positive ions to sustain the discharge. Subsequently, excitation of the gas results in intense illumination in the negative glow region. From this stage the electrons have insufficient exciting or ionising energy, resulting in the "Faraday dark space". Towards the anode a small accelerating field can produce ionization and excitation, the gas again becoming luminous.
These observations may have nothing to do with your experiment, but your pressure and applied voltage roughly correspond to the parameters of a magnetron sputtering machine.
I have given more details above about this experiment I did.Vanadium 50 said:More slow oozing of information. "in some detail" means "more than two sentences". Could anyone build the experiment based only on what you posted? I am guessing (!) you have only a roughing pump. Could it be vibrations from that? If the answer is "that's stupid", I would claim you will get fewer stupid answers if you describe your setup.
A layer-like structure in a cold plasma occurs due to the presence of charged particles and their interactions with each other and the surrounding environment. As the plasma cools, the particles become more organized and form layers due to their different densities and charges.
Several factors contribute to the formation of a layer-like structure in a cold plasma, including the temperature, density, and composition of the plasma, as well as external influences such as magnetic fields and electric fields.
Yes, a layer-like structure in a cold plasma can be controlled or manipulated by adjusting the external factors that influence the plasma, such as temperature, density, and electric and magnetic fields. Researchers can also use different techniques to manipulate the plasma, such as applying radio frequency waves or using lasers.
The layer-like structure in a cold plasma has various applications in fields such as materials science, plasma physics, and astrophysics. It can be used to study the behavior of charged particles in extreme conditions and to develop new technologies, such as plasma-based propulsion systems and plasma-based materials processing techniques.
The presence of a layer-like structure in a cold plasma can greatly impact plasma-based technologies. It can affect the efficiency and stability of plasma-based devices, such as plasma thrusters and plasma reactors, and also influence the properties of materials processed using plasma-based techniques. Therefore, understanding and controlling the layer-like structure is crucial for the development and advancement of plasma-based technologies.