Questions related to Plasma Physics
Generally, the IV characteristics of Langmuir probes are defined for unmagnetized plasma. How to estimate the electron temperature and plasma density let's say if there is some axial field inside the plasma source(50-100G).
1. Should different kinds of probes be used for measuring in such situations? (Shielded probes).
2. Or the IV traces obtained should be corrected by using some theory?
Thanks in advance
Those who have been researching plasmoid and there interaction have up until now used the name plasma physics to describe the field and then bioactive plasma physics, low energy plasma physics or field plasma etc. to try be more specific and not get confused with high energy plasma physics. I would like to suggest the name Plasmoid physics which is close to plasma but not so close that they are easily confused.
Bostick, W. H., “Experimental Study of Plasmoids“ Electromagnetic Phenomena in Cosmical Physics, (1958) Proceedings from IAU Symposium no. 6. Edited by Bo Lehnert. International Astronomical Union. Symposium no. 6, Cambridge University Press, p.87
Boltzmann equation in plasma physics is a very fundamental equation in kinetic theory. What's the relation of the one in plasma physics and that in thermodynamics.
I have read somewhere that
1. if the time scales of the phenomena to be observed are larger than the times scales of plasma oscillation and
2. spatial length scales are larger than the debye length than fluid theory is applied.
I couldnt understand the second condition, means what is the significance of wavelength of launched wave greater or lower than the debye length
please explain if anybody can ...
thanks in advance
There are three major equations in MHD plasma such as momentum equation, continuity equation and energy equation.
What is the physical significance or a description of energy equation in that ?
when we study plasma waves (plasma oscillations, electron waves and ion waves) we study perturbation in density, velocity and electric field and use momentum, continuity and poison equation to start with.
after introducing perturbation in each quantity we do linerization of non-linear (or higher order terms).
Please explain why is it necessary at all to do it? what if we do not linearlize the quantity ?
Thank you in advance,
I'm doing my Master Thesis on a new design for the Ionization Stage for a micropropulsion System and I would like to learn how to use some open source software suitable for the analysis of Plasma Physics.
In a previous discussion PIConGPU was pointed out. Do you think it could be suitable for the analysis of the plasma physics inside an hollow cathode?
If yes, how should I start to learn it?
If no, do you have any other suggestion?
Thank you very much for your help!
I measured more than one megatesla close to H-B11 nuclear fuel during nuclear fusions. Must be confirmed.
Now it is open the possibility that the matter comprises quantified magnetic fields only
When we are talking about any plasma system, the resonance in the system is satisfied by the condition (ω = k · v) without any magnetic field and by (ω − nωc = kzvz ) in a magnetic field. Why it happens so? What is its physical significance? Why only the parallel component contributes in the presence of magnetic field? What are the applications of this phenomenon in different branches of plasma physics starting from the laboratory plasma to the space and astrophysical plasmas? Kindly post your suggestions in the context of your expertise field. Thank you.
I am trying to implement PIC-code for the field emission simulation. According to PIC loop particles injected after calculation of charge density. But I stuck at the problem that at some points of an emitter a field could be accelerative but not strong enough to produce a charge that at least is not lesser than the electron's charge. What should be done in this situation? Macroparticle should not be injected and charge density at these points should be equal to zero or there is some condition that I am missing?
Magnetic mirrors are well known in plasma physics. In order to work, the mean free path of the charge carriers has to be at least as long as the helical paths under the influence of the B field. Therefore, magnetic mirrors exert no mirror effect on the conduction electrons in metals under usual conditions. However, ultra-pure metals at low temperature provide a mean free path of several millimeters. If the mean free path becomes longer than the dimensions of the specimen, the conduction is called ballistic.
If a magnetic mirror had the same effect on a "ballistic electron gas" as on a plasma, different electron densities in front and at the back of the mirror would result, and hence a voltage across the mirror would appear. This voltage would be built up by using the thermal energy of the electrons. Obviously, a voltage source based on thermal energy (in the absense of a temperature gradient) violates the 2nd law of thermodynamics.
I have to admit that I do not deal with details of solid state physics on a daily basis, so this is some kind of doing "armchair physics". But I would very much like to recognize the flaw in my thinking, and I didn't find publications dealing explicitely with this topic. (Usually this means that the matter is so obvious that a publication wouldn't be worthwhile.) I wrote a short paper on this subject; the quantitative result is that one could expect an open circuit voltage of the order of 200 microvolts under feasible conditions:
Any helpful comments will be highly appreciated!
PS The magnetic flux density is assumed to be limited to about 1 T (Fermi energy = 11.1 eV (iron), B = 0.5 T => path diameter = 45 micrometer), so the magnetic field can be provided by permanent magnets. Since ballistic transport is limited to low temperature, an alternative would be the use of superconducting coils.
In a laboratory setup, the entropy of the whole system would be increased by the means for cooling the device. Assuming for the moment that the effect under consideration occurs at all, a battery of such voltage sources would however, after initial cooling, keep itself cool, provided that both the thermal insulation and the electric load, located outside the insulation, were sufficient.
Reportedly, zinc sufide (ZnS) doped with Ag or Al or Cu is the most energy-efficient scintillator: one estimate says it's 30 %, that is, for an optimized composition (doping, crystal size, etc.) a single 10 keV electron fully stopped in a thin layer of this material results in the emission of ~ 1500 photons of nominal ~ 2 eV, a total of 3 keV in photon energy, over 4 pi. I have found numerous references with data, for all kinds of scintillators (for short-emission time materials at e.g., scintillator.lbl.gov, which does not include ZnS because its long emission time excludes it from this list), but very few (and old) references to a theory (e.g., Klasen, 1947).
What is the best place to find such a theory, preferably starting with something primitive that a non-solid-state physicist can follow?
What is special about decomposition products and additives of a cellulose-based electrode that helps an electric arc during welding to be less spread out? What would be a feasible mechanism linking this phenomena with decomposition product and plasma column composition during arc welding? Typical welding handbooks and references merely state the phenomena (i.e. punchy arc by H2/CO) without explaining the mechanism behind (e.g. what chemical characteristic of these two gases provide the "punch" and penetration of arc).
In general, what are the mode of action of chemical additives of an welding arc that modifies its welding penetration characteristics?
Dear friends and colleagues,
a wide dissemination of science and knowledge is of utmost importance. Thus, Gruenwald Laboratories (www.g-labs.eu) is proud to launch a new, fully open access online journal in the field of plasma physics, the Journal for Technological and Space Plasmas.
Please visit us at: www.jtsp.eu
We are looking forward to recieve your submissions. The first issue will be published in June 2018.
with best regards
Dr. Johannes Gruenwald (editor-in-chief)
I have seen approximate formula depending on density and if it is fully or partially ionized.
I should add it to the excel table:
If there are several cases, I should like to add the cases to the excel table (I can use if inside excel formula), also visual basic can be used to include Bessel functions
To design a bias circuit (constant current source) for a plasma discharge, is there an "equivalent circuit model" for the plasma itself to simulate the circuit?
I'm trying to do both: DC and RF plasma and I need a constant DC & RF current
In a fusion reactor, after fusions or transmutations, some ions scapes at high speed. If a positive ion is ejected and a magnetic field is generated, then electrons would goes exactly in the same direction generating and opposite field that would reduced to 0 the generated electric field. Fortunately in the P+11B fusion charges goes in the opposite directions to maintain a 0 kinetic momentum, then the field is 0 and electrons could be at the start of fusion, but also could go coupled to ions and not generate any EM field
In this reference ,plasma frequency determined by Wp=(N x q2 /εzno x ε0 x m*)1/2
εzno is the relative permittivity (εr) of undoped ZnO
m* is the effective electron mass (0.28 m0)
There are some questions i want to ask:
1、Why take relative permittivity(εr) multiplied by permittivity of empty space(ε0)? (i find the permittivity of ZnO is 8.65)
2、The part of Ga content 1% in Table1
N =2.18x1020 (cm-3)
m*= 0.28m0 =0.28 x 9.11 x 10-31=2.55x10-31
To check the answer，I put the value into the formula:
Wp=(2.18x1020x(1.6x10-19)2 / 8.65x8.85x10-12x2.55x10-31)1/2
But the result is not equal 9.28x1014
Does anyone can set out the detailed calculation to help me to know whether i made any mistakes ?
Please explain to me step by step method to calculate the Electron Density of a Low-Temperature Argon DC Glow Discharge Plasma using Optical Emission Spectroscopy.
This laboratory plasma is produced by DC Glow Discharge of
(i) Argon gas
(ii) Some other gas mixed with Argon gas
The applied voltage ranges from 300 - 500 volt, whereas the pressure ranges from 0.10 - 0.20 millibar.
I expect my Electron Temperature and Electron Density to be approximate of the order of1 eV and 10^14 - 10^15 per meter cube, respectively.
I have obtained the behavior of potential as a function of distance from the probe, for different value of electronegativity, i.e., density ratio of negative ions with electrons. And, I find that potential profile initially decreases up to electronegativity equals one but later on it increases with increment in electronegativity. However, in literature I find that potential reduces with increment in electronegativity. How can I explain my results? Are they correct or not?
As can be seen in the image at https://www.researchgate.net/project/PULSOTRON-500k-SE-500KeV-THERMONUCLEAR-FUSION-REACTOR in the project log, there is an image captured during particle injection simulation. As can be seen when injecting particles perpendicular to the magnetic field (z-axis) the particles go through the reactor. I reduced particles speed and increased the injection angle but then I can not inject them in a pulsed manner.
I've already asked a question like that and followed your advice. I started studying: Plasma Physics via Computer Simulation (C K Birdsall and A B Langdon) but I really think that I need again your help.
I will work on a java project: Starfish code ( https://github.com/particleincell/Starfish ).
I I should simulate the plasma generation inside a dischage chamber coupled with a hollow cathode.
I would need to understand how to determine the boundary conditions before starting to set up my simulation
The problem is that even in the plasma physics books I have not found the right equations or models could help me.
Do you have any suggestion?
Thank you! Tommaso
I am looking for physics-based measurements that can be performed in the edge plasma (upstream, not at the divertor) that yield the separatrix position or some boundary for it. Some of the methods I am working on:
- measure the profile of plasma potential, find the peak
- measure density or ion saturated current fluctuation, find zero skewness (inner boundary)
- measure the profile of electron temperature, electron density, heat flux etc., fit it with a "broken" double exponential and find the breaking point (outer boundary)
- measure the profile of poloidal velocity (cross-correlation of poloidally spaced probes, Er x B drift etc.) and find the zero
Some of the methods I have found (some thanks to the answers below):
- in H-mode, fit the pedestal Te or ne profile with the tanh function and find its center (can optionally be corrected for some fraction of the SOL width) [G. Porter, Physics of Plasmas 5, 1410 (1998)]
- (specific to field reversed configurations with a weak external plasma source) modulate the plasma source at a known frequency and measure the floating potential profile with a Langmuir probe; the region where the frequency amplitude goes down suddenly is the magnetic separatrix [answer by S. Cohen below]
- assuming pressure balance along the field line, map divertor pressure measurements to upstream (at the divertor, the strike point position is known, e.g. Eich function fit, maximum heat flux etc.) and match it to upstream pressure profile (this can also be done with the floating potential, electron temperature, heat flux...) [C. K. Tsui, Physics of Plasmas 24, 062508 (2017)]
- develop some really specialised probes [K. Uehara et al, 2006 Jpn. J. Appl. Phys. 45 L630]
- use the power balance criterion (AKA Stangeby's two-point model) to calculate the separatrix temperature, then find it on any measured Te profile [H J Sun et al 2017 Plasma Phys. Control. Fusion 59 105010]
I am open to any suggestions, links to previous research, or your personal experience (whether you've encountered the problem of not knowing exactly where the separatrix is, whether you think it's worth addressing etc.).
My calculations with fixed probe potential for electronegative plasmas show that sheath thickness enhances with an increment in positive ions' temperature for fixed temperature of negative species, i.e. electrons and negative ions. But, I am not getting the reason why it is so.
I have read in a lot of papers related to numerical plasma physics that a separate equation named "Energy Balance Equation" (that looks a bit similar to continuity equation) is also taken under consideration for electrons only.
It is clear that the continuity equation gives the value of electron/ion density at the grid points and the Poisson equation gives the value of potential and electric field at the grid points. These Poisson-Continuity equations work together giving values to each other.
Could somebody explain me the use of Energy Balance equation in the simulation. I am not sure about what is calculated solving the Energy Balance equation.
What is the physical difference between the two and how are they used to study electromagnetic waves in parallel and perpendicular AC electric fields.
In some lecture report they say Zonal flow stands for the mode with toroidal/poloidal mode number n=m=0 mode in plasma physics. So the n=0, m!=0 Geodesic Acoustic Mode (GAM) is not Zonal flow. But in other paper, they say GAM is also a kind of Zonal flow. So who is right and who is wrong? Exactly what is zonal flow in plasma physics?
 L.W. Yan et al 2007 Nucl. Fusion 47 1673 Three-dimensional features of GAM zonal flows in the HL-2A tokamak
 L. Lachhvani, J. Ghosh, P. K. Chattopadhyay, N. Chakrabarti, and R. Pal, “Observation of geodesic acoustic mode in SINP-tokamak and its behaviour with varying edge safety factor,” Phys. Plasmas, vol. 24, no. 11, 2017.
Thank you for spending your precious time:
I am working on GOLEM TOKAMAK dataset for disruption prediction using machine learning and i found the below features play a major role in disruption prediction so,below i have attached a set of features but i find hard to download the signals because i couldn't identify which data suites the exact feature mentioned
plasma current - Ip (available)
Total input power - available
mode locked amplitude - no idea
plasma internal inductance - no idea
plasma density - no idea
poloidal beta - no idea
so,could anyone please suggest me a which data signal i have to select or from which signal i have to derive the above feature.herewith i attached the page for dataset download.
I have designed a thin torus to be filled with hydrogen or deuterium plasma accelerated to 80 kA.
This is not a standard tokamak design that have only one confination coil.
The problem is when going the particles inside it oscillates forward and backward the torus centre increasing the amplitude until the particles scapes.
This torus is a part of the Miranda reactor: https://www.researchgate.net/project/PULSOTRON-500k-SE-500KeV-THERMONUCLEAR-FUSION-REACTOR
Kindly tell me as how to use FEM in dusty plasma physics. Any paper or book related to the same if you have with you please let me know.
I have seen in most of the plasma physics textbooks the temperature versus pressure graph as shown attached with this question.
The graph as attached in this question is useful to explain the transition of a non-thermal plasma to thermal plasma. For non-thermal plasma, Te>>Tg whereas for thermal plasma Te~Tg.
The attached graph with this graph is not a real plot. It was sketched for understanding by Prof. Alan Howling. Did anybody try to obtain it through calculations ?
I would be happy for your answers and interested to obtain it with some graphical softwares like MATLAB.
It is known that high energy gamma photons can decay into electron-positron pairs in a strong background field via the multi-photon Breit-Wheeler process. This real photon is first emitted by an energetic electron, therefore this is a two-step process. There exist also one-step process, where the intermediate photon is virtual, thus one electron can directly create the pair in a strong laser field. For the trident production rate I found formulas in the literature, which is implemented in EPOCH for instance, but in the code the energy of newly created particles is zero. In the case of two-step process it is clear that the total energy of pair is equal to the photon energy, but I could not find any clear expression for this initial energy in the case of trident. I think it is assumed that their initial momentum is relatively small and their recoil effect is negligible, that's why it is approximated by zero in order to reduce the computation in PIC codes. However, I could not find any paper supporting this statement. Can someone help me in this ?
To generate a high power discharge usually a capacitor over a coil is done, but to make it at high power a great capacitor must be used and as long that frequency is inverse proportional to square root of inductance and capacitance, large capacitors should lower the frequency.
Our fusion reactor Miranda have dozens of parameters to adjust to obtain reactions.
Our simulator uses an easy algorithm to simulate our models running 16 threads but it is difficult to change all the parameters so we have few data to feed the learning algorithm, so we need a neural network with a very fast method that learns with few samples.
I heard that arc discharge with 2kv is required to ablate the surface and ionize it but i dont know the relation. i hope that this relation will help in knowing the amount of energy required to ablate various propellants
During my plasma treatment I observe increase in surface temperature on powered and grounded electrode in CCP-RF low pressure configuration.
At increased RF power, temperature of powered electrode increases.
In my case electron neutral collision frequency is higher than applied rf frequency i.e. 13.56 MHz. Thus ohmic heating is dominating.
Please explain me how to calculate the surface temperature on both powered and grounded electrode ? Any theory / equations help if we know the density and temperature of plasma ?
Thanks in advance,
I was wondering if there are free access to data for plasma physics online which can be analyzed and further work with it computationally as well. I'd glad if anyone could mention possible project ideas for undergraduates related to plasma physics.
I am trying to search for a topic in plasma for my project and I am quite new to Plasma Physics. So if you could also suggest me on how to start with this topic,it'd probably help me a lot.
I am unable to understand the origin of components of CC P-RF sheath equivalent circuit components (resistor, capacitor and diode) and that of bulk plasma (resistor and inductor).
I am not getting any simple words explanation of physics over there. Can someone please explain me or help me with suitable literature ?
Thanks in advance.
with kind regards,
What exactly changes when we use 40 KHz, 13.56 MHz or 2.4 GHz plasma source for plasma surface activation of polymers at low pressure in CCP-RF type plasma ?
Why 40 KHz gives better results compared to 13.56 MHz plasma ?
We consider small perturbation in plasma to understand the concept of plasma oscillation.
We take perturbation in velocity, density and electric field.
que-1 how do we create this perturbation (with what frequency, voltage and how ?). want to understand with physical example.
que-2 we consider small perturbation, how can we quantify this ?
que -3 what will happen if we remove the given perturbation ?
Thank you in advance,
With kind regards,
The problem is that the isolators parts of coils heat must be removed.
Isolation materials have low power transmission coefficient (about 0.6-2.5 W/mK) with respect copper (>400W/mK).
Unfortunately attaching directly copper parts to vacuum chamber wall would shortcircuit the internal coils
This problem was detected during the thermal design of Rita and Patricia fusion reactors
I've known that one of the unresolved problems is the Coronal heating problem and there are already many theories to explain the illogical temperature at the Corona. I need to know what are the other problems in the field of Solar Physics and what are the challenges to explain these problems?
In some conditions we take average K.E. if electron in plasma as 1/2 KT and sometimes we take just 'KT'.
When should we consider what and why ?
Thank you in advance,
I am working with a CH4/H2 Plasma in a cold-wall reactor. If I use conducting substrates (like metalls) there is a homogeneous plasma visible above my substrate (roughly 1-2 cm aboce the surface of the substrate). Now if I use non-conducting or semi-conducting substrates (GaN on sapphire susbtrates) there is a clearly visible "hole" in the plasma just above the substrates surface. With my humble knowledge about plasma physics, I know that the non-emitting parts of the plasma mean that there are just positive ions and no more electrons (plasma sheath).
So my question is: what is the reason for "hole" above my substrate and what exactly happens there with the precursor molecules?
I would suggest that, because of the non existing potential drop between the substrate and the electrodes, there is no acceleration of positive ions torward the substrates surface there. But what kind of molecules/atoms define this region above the substrates surface?
Is there just a huge plasma sheath and thus I see no emission or is there simply no plasma at all and no decomposition takes place in this region?
Maybe some of you already stumbled over a similar problem.
With best regards
Hello, everyone, I want to know, how to interpret the results of correlation coefficients. I have noted its explanation from the links
(ii) (http://www.dummies.com/education/math/statistics/how-to-interpret-a-correlation-coefficient-r/) as:
Correlation coefficients whose magnitude are between 0.9 and 1.0 indicate variables which can be considered very highly correlated. Correlation coefficients whose magnitude are between 0.7 and 0.9 indicate variables which can be considered highly correlated. Correlation coefficients whose magnitude are between 0.5 and 0.7 indicate variables which can be considered moderately correlated. Correlation coefficients whose magnitude are between 0.3 and 0.5 indicate variables which have a low correlation. Correlation coefficients whose magnitude are less than 0.3 have little if any (linear) correlation.
But I don't know whether I can use this in Plasma physics statistical study or not?
any help will be appreciated. thanks
Please help, it says that ECR plasma has bombardment effect, but where does the kinetic energy of ions come from? Does the substrate has to be negatively biased? I
I try to find a relation between Power (P), Argon pressure (ppm) and probably distance (cm) between cathode and plate so as to have maximum ionisation of gas.
I am currently using for the first time ICP-AES and we have encountered some ignition problem, the plasma went off suddenly and since then we haven't been able to ignite it, we get a message popping up on screen , which say magnetron voltage is too high. Can someone please highlight some of the problem they have encountered while using Agilent ICP-AES 4200 and how did you solve them?
I've read some article that the inverse bremsstrahlung is the process that a free electron absorbs a photon while it collides with an ion, so it is 3-body process.
But I don't know how it is physically explanined. Why the electron that is in collision with the ion can absorb the photon?
And I would like to know the relationship between the laser energy and the plasma electron density. I've also read the following relations.
1. If plasma angular frequency wp < laser angular frequency w : the plasma is transparent for the laser.
2. If wp = w : the plasma becomes a perfect mirror.
3. If wp > w : the plasma becomes a good laser absorber.
I can understand the 1st case as it is easily proved in a undergraduate level plasma physics course. 2nd case...is what I may accept.. But 3rd case...how can it is physically explained?
Thanks for reading this and I look forward to get any response.
The project theme is very interesting and I would like to learn the ionization process which takes place when the high energetic particles (electron/proton) enter to our inner magnetosphere-ionosphere-atmosphere system. I am doing the link between this ionization process and atmospheric electric field changes over south polar stations, so that either this ionization creates a localized capacitor system at middle atmosphere or what kind of changes been expected.?
I'm working in the plasma physics and trying to calculate the thermal conduction time or speed.
The plasma treated has cylindrical symmetry surrounded by the dielectric material.
Right now I need to calculate the time the energy or heat takes to move from the axis of the plasma to the wall with the given thermal conductivity.
I guess the time is function of not only conductivity but also temperature difference between two points thus let's assumed that the axis temperature is Te while dielectric is at room temperature..
In plasma configuration, plasma is generated by top/bottom electrode and consists of positive ion and electron. And ion-electron recombination time is very short. So my question is that how can we get ion-electron recombination time or duration in the case of SF6 plasma? For designing my experiment, ion-electron recombination time of SF6 is quite important factor but I have a difficulty in this problem. I want to get some information, comments or tips about it. Thanks
In a DC sputtering diode system, the positive ions follow the electric field direction till they hit the target to eject materials, while the electrons move in the opposite direction.
- how do the electrons reach the anode if the substrate was not conductive?
- the net current direction should be in the same direction of the electric field, where is the closed path of ion and electron currents?
We are planning experiments that will involve hydrogen-boron plasma reacting with beryllium electrodes. Since very high current densities are involved, we are interested to see if any BeB compounds that are formed will have good electrical and thermal conductivity once the current heats them up.
I need the cold plasma for decontamination of the medicinal plants.
Modified Boltzmann plot is one of the widely accepted method for electron temperature estimation in atmospheric pressure plasma jets. Since, this is based on the relative emission intensities existing in the optical emission spectrum of a particular plasma, I wanted to estimate electron temperature for Argon plasma jet. Using 14 emission lines, I obtained the value of electron temperature around 0.35 eV.
I used the same spectrums to calculate electron temperature using collisional radiative model. The electron temperature is observed to be much higher than obtained using Modified boltzmann plot.
The plots of both methods have been attached here.
Can somebody help me why there is so much variation between the electron temperatures of modified boltzmann plot and collision radiative model although I use same spectrums for calculation ??
Why the plasma ingredients become degenerate due to the influence of Pauli-exclusive principle and classical statistical assumptions is break dawn ?
I want to use RIE to etch GaN, I think I should use Cl2 and BCl3 but I need to know about the range of plasma power and working pressure.
in our lab, TaN electrode is deposited using DC sputter system and fabricate MOS capasitor composed of ALD-high-k thin film. However, reproducibility is not good specially at I-V measurement. so we guess because of plasma damage in sputter system. Is it possible? I want to ask you for advice.
The charged particled trapped in the Van-Allen belts around Earth, maybe they affected by the natural Earth's rotational or wobbling motions and their distribution get disturbed and may reflect some radio disturbances or affect the TEC distribution in the ionosphere.
I have a coaxial cylinder with a cooper wire inside which is corona discharge happening. (1st picture)
Corona discharge is happening after ionization in this coaxial cylinder. My question is about calculating E (electric field)and Q (Amount of charge) in ionization area(2nd picture)! Would really appreciate if your help is included the process before ionization (E and Q).
Thanks in advance for your help!
2nd picture is taken from: IJPEST_Vol2_No2_03_pp082-088