Cross-section analysis of the Magnum-PSI plasma beam using a 2D multi-probe system

Costin, C.; Anita, V.; Ghiorghiu, F; Popa, G.; Temmerman, G. De; Berg, M.A. van den; Scholten, J.; Brons, S.

doi:10.1088/0963-0252/24/1/015014

Cited by 10 publications

(36 citation statements)

References 12 publications

(19 reference statements)

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“…5 for different applications: for Hall thrusters (HT) and hollow cathode discharges (HC), for magnetron sputtering devices, and for tokamaks. The magnetic field range between magnetrons and tokamaks, , is covered by magnetically confined linear plasma generators (LPG) 54 , 55 . Such devices are specially designed to investigate plasma-surface interactions which are relevant for edge regions of fusion reactors 56 .…”

Section: Analytical Solution and Resultsmentioning

confidence: 99%

Secondary electron emission under magnetic constraint: from Monte Carlo simulations to analytical solution

Costin

2021

Sci Rep

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The secondary electron emission process is essential for the optimal operation of a wide range of applications, including fusion reactors, high-energy accelerators, or spacecraft. The process can be influenced and controlled by the use of a magnetic field. An analytical solution is proposed to describe the secondary electron emission process in an oblique magnetic field. It was derived from Monte Carlo simulations. The analytical formula captures the influence of the magnetic field magnitude and tilt, electron emission energy, electron reflection on the surface, and electric field intensity on the secondary emission process. The last two parameters increase the effective emission while the others act the opposite. The electric field effect is equivalent to a reduction of the magnetic field tilt. A very good agreement is shown between the analytical and numerical results for a wide range of parameters. The analytical solution is a convenient tool for the theoretical study and design of magnetically assisted applications, providing realistic input for subsequent simulations.

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Section: Analytical Solution and Resultsmentioning

confidence: 99%

Secondary electron emission under magnetic constraint: from Monte Carlo simulations to analytical solution

Costin

2021

Sci Rep

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“…Since ζ is weighted by ε(r), Equation 15 must be inverted to yield ε(r) before Equation 14 can be inverted to yield ζ (φ 0 , r), from which n e can be determined according to Section III B. The Magnum-PSI plasma beam has approximate cylindrical symmetry about its axis 45 . This cylindrical symmetry is often assumed during spectroscopic studies of Magnum-PSI (and also of Pilot-PSI), with an Abel inversion used to obtain the local plasma properties from the observed lineintegrals 20,41,46 .…”

Section: E Abel Inversionmentioning

confidence: 99%

2D measurements of plasma electron density using coherence imaging with a pixelated phase mask

Allcock

Silburn

Sharples

et al. 2021

Review of Scientific Instruments

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In this paper, the pixelated phase mask (PPM) method of interferometry is applied to coherence imaging (CI)—a passive, narrowband spectral imaging technique for diagnosing the edge and divertor regions of fusion plasma experiments. Compared to previous CI designs that use a linear phase mask, the PPM method allows for a higher possible spatial resolution. The PPM method is also observed to give a higher instrument contrast (analogous to a more narrow spectrometer instrument function). A single-delay PPM instrument is introduced as well as a multi-delay system that uses a combination of both pixelated and linear phase masks to encode the coherence of the observed radiation at four different interferometer delays simultaneously. The new methods are demonstrated with measurements of electron density ne, via Stark broadening of the Hγ emission line at 434.0 nm, made on the Magnum-PSI linear plasma experiment. A comparison of the Abel-inverted multi-delay CI measurements with Thomson scattering shows agreement across the 3 × 1019 < ne < 1 × 1021 m−3 range. For the single-delay CI results, agreement is found for ne > 1 × 1020 m−3 only. Accurate and independent interpretation of single-delay CI data at lower ne was not possible due to Doppler broadening and continuum emission.

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“…The discharge current delivered by the arc-source was 125 A. The applied magnetic field was about 0.95 T in the middle of the coils, which corresponds to 0.07 T at the measuring point (target position) [3]. At target position, the magnetic confinement of the plasma can be considered rather weak, since the cyclotron frequency of H + ions is in the same range as their collision frequency, but this doesn't limit the validity of the results.…”

Section: Current Distribution To the Surface Of The Floating Targetmentioning

confidence: 99%

“…-electron density and temperature are measured at 20 cm in front of the target, where the plasma column diameter is narrower than at the target due to the divergence of the magnetic field in this region [3]; thus, the electron saturation current I e sat is underestimated at larger radii and, consequently, the estimated plasma potential is more negative than it should be; this could be the reason why V p = V f at larger radii.…”

Section: Estimation Of the Plasma Potentialmentioning

confidence: 99%

Tailoring the charged particle fluxes across the target surface of Magnum-PSI

Costin

Anita

Popa

et al. 2016

Plasma Sources Sci. Technol.

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Linear plasma generators are plasma devices designed to study fusion-relevant plasma-surface interactions. The first requirement for such devices is to operate with adjustable and well characterized plasma parameters. In the linear plasma device Magnum-PSI, the distribution of the charged particle flux across the target surface can be tailored by the target bias. The process is based on the radial inhomogeneity of the plasma column and it is evidenced by electrical measurements via a 2D multi-probe system installed as target. Typical results are reported for a hydrogen discharge operated at 125 A and confined by a magnetic field strength of 0.95 T in the middle of the coils. The probes were biased in the range of -80 to -30 V, while the floating potential of the target was about -35 V. The results were obtained in steady-state regime of Magnum-PSI, being time-averaged over any type of fluctuations. Depending on the relative value of the target bias voltage with respect to the local floating potential in the plasma column, the entire target surface can be exposed to ion or electron dominated flux, respectively, or it can be divided into two adjacent zones: one exposed to electron flux and the other to ion flux. As a consequence of this effect, a floating conductive surface that interacts with an inhomogeneous plasma is exposed to non-zero local currents despite its overall null current and it is subjected to internal current flows.

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Cross-section analysis of the Magnum-PSI plasma beam using a 2D multi-probe system

Cited by 10 publications

References 12 publications

Secondary electron emission under magnetic constraint: from Monte Carlo simulations to analytical solution

Secondary electron emission under magnetic constraint: from Monte Carlo simulations to analytical solution

2D measurements of plasma electron density using coherence imaging with a pixelated phase mask

Tailoring the charged particle fluxes across the target surface of Magnum-PSI

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