Magnum-psi, a new linear plasma generator for plasma-surface interaction studies in ITER relevant conditions

Groot, B. de; Ahmad, Zahoor; Dahiya, R.P.; Engeln, Rah Richard; Goedheer, W. J.; Cardozo, N.J. Lopes; Veremiyenko, V.P.

doi:10.1016/s0920-3796(03)00174-1

Cited by 33 publications

(21 citation statements)

References 3 publications

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“…We can see that the departure from excitation equilibrium is high when the input power is low and the CH 4 content is high. As mentioned before, the lower discharge power means a lower T e at certain CH 4 concentration, and inputting CH 4 gas would lead to decrease in T e at certain (5) n e (m −3 ) > 1.6 × 10 12 T 1/2 e (�E) 3…”

Section: Discussionmentioning

confidence: 88%

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Determination of the number densities of CH(X2Π) and CH(A2Δ) radicals in a DC cascaded arc discharge plasma

Wang

et al. 2015

Appl. Phys. B

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radical-based chemistry generally dominates in any eventual material processing in the plasma jet.The CH radical is a common intermediate in reactive chemical systems with hydrocarbons [6]. Monitoring CH provides an insight into the reaction mechanism. CH radicals and C atoms contribute to the experimentally observed high and nonuniform diamond growth rates in the highpower Bristol reactor [7]. The level of CH concentration agreement between the model prediction and the experimental measurement can be used to test model predictions of hydrocarbon chemistry [8]. CH also is a probe species to determine the chemical erosion of carbon-based materials in divertor [9].Optical emission spectroscopy (OES) is arguably the simplest and most straightforward means to investigate the CH behavior in the plasma. The OES signal is proportional to the population density of the upper state, and the interpretation of OES data is complicated which needs a proper understanding of the various species excitation and de-excitation processes, especially when the plasma does not close to local thermodynamic equilibrium (LTE). Generally, the ground electronic state radicals and molecules are inevitably present in higher concentrations than their electronically excited counterparts and dominate the thin film deposition [10]. Thus, it is necessary to measure the majority species populating ground and low-lying electronic states.To diagnose the ground state, absorption spectroscopy is a preferred approach. Cavity ring-down spectroscopy (CRDS) [11] provides the diagnostic of choice to obtain the absolute number densities without the need for additional calibration standards. The technique measures the time decay of a laser pulse trapped in a high-finesse optical cavity. Effectively, it is a multi-pass technique in which the optical path length may be tens of kilometers. Thus, it is a versatile, highly sensitive, linear absorption technique.Abstract A combination of optical emission spectroscopy (OES) and cavity ring-down spectroscopy (CRDS) has enabled to determinate the number densities of CH(A 2 Δ) and CH(X 2 Π) radicals simultaneously in a cascaded arc plasma reactor operating with a CH 4 /Ar mixture. It is found that the number density of CH(A 2 Δ) radical increases with discharge current at first and then decreases. However, the number density of CH(X 2 Π) radical decreases with discharge current when the rate of CH 4 flow to total flow is lower than 1 %, while it increases slightly with discharge current when the rate is 1.5 %. The results reveal that CH radicals are deviation from excitation equilibrium. Although OES is the simplest and most straightforward means to investigate the CH radical behavior, it is not enough to provide the information of the CH(X 2 Π) number density, and additional methods, such as CRDS, are needed in the cascaded arc plasma jet.

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Section: Discussionmentioning

confidence: 88%

“…It is also the core component of linear plasma generator with cascaded arc plasma source [5] which is used to study the divertor plasma surface interaction in fusion field. Neutral molecule and 1 3…”

Section: Introductionmentioning

confidence: 99%

Determination of the number densities of CH(X2Π) and CH(A2Δ) radicals in a DC cascaded arc discharge plasma

Wang

et al. 2015

Appl. Phys. B

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“…Electron temperature in the argon plasma is 3000 K and in the hydrogen plasma it is 2300 K. In some of the experiments for hydrogen operation the cascaded arc source was modified [6] in which argon (10% of the flow) is supplied in the cathode region to prevent quick erosion of the cathode tips. Also the central bore diameter in the 2 plates on the cathode side is reduced to 2 mm; hydrogen gas is added half way along the arc channel via a radial inlet port.…”

Section: Plasma In Expansion Regionmentioning

confidence: 99%

“…A magnetised linear plasma device using cascaded arc produced plasma has been set up [6] at the FOM Institute for Plasma Physics 'Rijnhuizen', the Netherlands (FOM) for conducting the plasma surface interaction experiments. Though plasma parameters with an axial magnetic field were measured [7] in the cascaded arc facility at the University of Technology, Eindhoven, the Netherlands, the magnetic field used in the FOM facility is substantially higher, reaching up to 1.6 T. Moreover, additional current is drawn through the magnetised plasma beam.…”

Section: Introductionmentioning

confidence: 99%

High Density Cascaded Arc Produced Plasma Expanding in a Low Pressure Region

Dahiya¹,

Kumari²,

Veremiyenko³

et al. 2004

Contrib. Plasma Phys.

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Experimental measurements made in thermal expanding argon, nitrogen and hydrogen plasmas with particular reference to molecular kinetics, surface nitriding and intense flux in magnetic field are discussed. The plasma is generated in a cascaded arc source. In the presence of molecular species (H2 / N2) dissociative recombination reactions involving rovibrationally excited molecules contribute to a rapid decay of the plasma species, especially for hydrogen system. A combination of nitrogen and hydrogen plasma gives an efficient plasma nitriding process, which has been applied for case hardening of machinery components. In another setup a strong axial magnetic field (0.4 -1.6 T) contains and substantially prolongs the plasma beam in the chamber. In the presence of the magnetic field, an additional current drawn through the plasma beam using a biased substrate and a ring creates dense low temperature plasma giving a new unexplored plasma regime. The plasma kinetics are modified in this regime from the recombining to the ionising mode. When the additional current in the argon plasma beam exceeds 30 A, its light emission is predominantly in the blue region. With the additional current and magnetic field, the emission intensity of H β and other lines arising from higher energy levels in the hydrogen Balmer series is enhanced.

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“…The axial magnetic field confines the expanding plasma jet to a narrow beam. In this way the plasma beam is transported to a target with minimal losses as can be seen in the already existing Pilot experiment [5] shown in Fig. 1.…”

Section: Introductionmentioning

confidence: 96%

Pre-Design of the Superconducting Magnet System for Magnum-psi

Eck

Koppers

Smeets

et al. 2006

IEEE Trans. Appl. Supercond.

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Abstract-The FOM-Institute for Plasma Physics Rijnhuizen is preparing the construction of Magnum-psi, a magnetized (3 T), steady-state, large area (80 cm 2 ) high-flux (up to 10 24 H + ions m 2 s 1 ) plasma generator. The aim of the linear plasma device Magnum-psi is to provide a controlled, highly accessible laboratory experiment in which the interaction of a magnetized plasma with different surfaces can be studied in detail. Plasma parameters can be varied over a wide range, in particular covering the high-density, low-temperature conditions expected for the detached divertor plasma of ITER. A vital part of the Magnum-psi experiment is the superconducting magnet system, which generates a magnetic field of 3 T while good diagnostic access to the experiment is guaranteed.In this contribution, we will explain the requirements on the magnet system, which is now in the pre-design phase. The present design consists of 3 cylindrical NbTi coils which generate a plateau shaped field of 3 T in a 1.3 meter room temperature bore. The discrete coils are supported by a 2.4 meter long single cylinder in a shared cryostat with 16 room temperature view-ports of 200 mm diameter. The field will most probably be passively shielded by an iron wall surrounding the experimental area.As background, some elements of the pre-design of the Magnum-psi experiment; i.e. vacuum system, plasma source and diagnostics are presented.

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Magnum-psi, a new linear plasma generator for plasma-surface interaction studies in ITER relevant conditions

Cited by 33 publications

References 3 publications

Determination of the number densities of CH(X2Π) and CH(A2Δ) radicals in a DC cascaded arc discharge plasma

Determination of the number densities of CH(X2Π) and CH(A2Δ) radicals in a DC cascaded arc discharge plasma

High Density Cascaded Arc Produced Plasma Expanding in a Low Pressure Region

Pre-Design of the Superconducting Magnet System for Magnum-psi

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