Simulation of the Neutral Inventory in the Pilot‐PSI Beam

Wieggers, R. C.; Groen, P. W. C.; Blank, H. J. de; Goedheer, W. J.

doi:10.1002/ctpp.201210030

Cited by 9 publications

(10 citation statements)

References 14 publications

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“…All experiments described herein were conducted at a bias of -20 V with respect to ground to provide incident ion energies of approximately 20 eV. A differential pumping system ensures that the neutral density near the target , which is consistent with simulations [30].…”

Section: Experimental Measurements Of Lithium Erosion 31 Experimentamentioning

confidence: 68%

Erosion of lithium coatings on TZM molybdenum and graphite during high-flux plasma bombardment

Abrams¹,

Jaworski²,

Kaita³

et al. 2014

Fusion Engineering and Design

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The rate at which Li films will erode under plasma bombardment in the NSTX-U divertor is currently unknown. It is important to characterize this erosion rate so that the coatings can be replenished before they are completely depleted. An empirical formula for the Li erosion rate as a function of deuterium ion flux, incident ion energy, and Li temperature was developed based on existing theoretical and experimental work. These predictions were tested on the Magnum-PSI linear plasma device capable of ion fluxes > 10 24 m -2 s -1 , ion energies of 20 eV and Li temperatures > 800 °C. Li-coated graphite and TZM molybdenum samples were exposed to a series of plasma pulses during which neutral Li radiation was measured with a fast camera. The total Li erosion rate was inferred from measurements of Li-I emission. The measured erosion rates are significantly lower than the predictions of the empirical formula. Strong evidence of fast Li diffusion into graphite substrates was also observed.

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Section: Experimental Measurements Of Lithium Erosion 31 Experimentamentioning

confidence: 68%

Erosion of lithium coatings on TZM molybdenum and graphite during high-flux plasma bombardment

Abrams¹,

Jaworski²,

Kaita³

et al. 2014

Fusion Engineering and Design

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“…The first step is the ion conversion with a hydrogen molecule in vibrational excited state, gaining H2 + . This is followed by dissociative recombination (reaction 19) and proton transfer with N2 producing N2H + (reaction 66). Such species is then consumed via reactions 30 and 31, producing NH and N2 .…”

Section: Comparison Between the Full And The Reduced Global Modelsmentioning

confidence: 99%

Studying the influence of nitrogen seeding in a detached-like hydrogen plasma by means of numerical simulations

Perillo

Chandra

Akkermans

et al. 2018

Plasma Phys. Control. Fusion

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The leading candidate for impurity seeding in ITER is currently nitrogen. To date, there are only a few studies on the plasma chemistry driven by N 2 /H 2 seeding and its effect on the molecular-activated recombination of incoming atomic hydrogen ions in a detached-like scenario. Numerical simulations are needed to provide insights into such mechanisms. The numerous amount of plasma chemical reactions that may occur in such an environment cannot be entirely included in a 2 or 3-dimensional code such as Eirene. A complete global plasma model, implemented with more than 100 plasma chemical equations and 20 species, has been set up on the basis of Plasimo code. This study shows two main nitrogen-included recombination reaction paths resulted to be dominant, i.e. the ion conversion of NH followed by dissociative recombination and a proton transfer between H 2 + and N 2 , producing N 2 H +. These two processes are referred to as N-MAR (nitrogen-molecular activated recombination) and have subsequently been implemented into Eunomia, a spatially-resolved Monte Carlo code, designed to simulate the neutrals inventory in linear plasma machines such as Pilot-PSI and Magnum-PSI. To study the effect of N 2 on the overall recombination, three cases of study have been set up: from a defined puffing location with a constant total seeding rate of H 2 + N 2 , three N 2 ratios have been simulated, i.e. 0, 5 and 10%. The parameter monitored is the density of atomic hydrogen, being the final hydrogenic product of any recombination mechanism in the scenario considered. The difference in H density between the 0% case and the 10% case is about a factor 3. The importance of NH as electron donor is highlighted and N-MARs confirmed as reaction routes enhancing the conversion of ions to neutrals, making the heat loads to the divertor plate more tolerable. This work is a further step towards the full understanding of the role of N 2-H 2 molecules in a detached divertor plasma.

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“…The ion flux on the targets can be estimated by applying the Bohm criterion [13] and ranges from 2 Â 10 24 ions m À2 s À1 in the center of the target to 5 Â 10 23 ions m À2 s À1 at the edges. For our experimental conditions, the deuterium in the plasma predominantly consists of atomic ions [14,15]. The kinetic energy of the ions arriving at the surface can be estimated by considering a drifting Maxwellian velocity distribution for the ions in the plasma and an acceleration over the plasma sheath towards the surface.…”

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confidence: 99%