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Tuesday, July 28, 2020 | History

3 edition of Model of an ablating solid hydrogen pellet in a plasma found in the catalog.

Model of an ablating solid hydrogen pellet in a plasma

Paul B. Parks

Model of an ablating solid hydrogen pellet in a plasma

by Paul B. Parks

  • 180 Want to read
  • 36 Currently reading

Published by Garland Pub. in New York .
Written in English

    Subjects:
  • Thermonuclear fuels -- Ablation.,
  • Fusion reactors -- Refueling.,
  • Hydrogen -- Isotopes.,
  • Tokamaks.,
  • Solid hydrogen.

  • Edition Notes

    StatementPaul B. Parks.
    SeriesOutstanding dissertations on energy
    Classifications
    LC ClassificationsTK9360 .P37
    The Physical Object
    Pagination156 p. :
    Number of Pages156
    ID Numbers
    Open LibraryOL4751835M
    ISBN 100824039890
    LC Control Number78074999

    τ(E,ρ) describing the loss of fast atoms in the plasma on their path from the cloud to CNPA [2]. Consider a monoenergetic flux Γ1 0(,)x E x= [cm-2s-1] of fast protons H+ of energy E entering the cold dense cloud surrounding an ablating solid pellet; x is . Radial acceleration of solid hydrogen pellets in hot tokamak plasmas T. Szepesi1, S. Kálvin1, G. Kocsis1, P.T. Lang2 and ASDEX Upgrade Team2 1 KFKI – Research Institute for Particle and Nuclear Physics, EURATOM Association, P.O. H Budapest, HUNGARY 2 Max-Planck-Institut für Plasmaphysik, EURATOM Association, Boltzmannstr. 2,

      Plasma response in auxiliary-heated discharges 6. Summary and discussions Injection of pellets associated with neutral-beam in- References jection Abstract: The ablation of a refuelling pellet of solid hydrogen isotopes is governed by the plasma state, especially the density and energy distribution of the electrons. We describe the design and operation of the solid hydrogen pellet injection system used in plasma refueling experiments on the ISX tokamak. The gun‐type injector operates on the principle of gas dynamic acceleration of cold pellets confined laterally in a tube. The device is cooled by flowing liquid helium refrigerant, and pellets are formed in situ.

      A two-dimensional hydrodynamic simulation code CAP has been developed in order to investigate the dynamics of hydrogenic pellet ablation in magnetized plasmas throughout their temporal evolution. One of the properties of the code is that it treats the solid-to-gas phase change at the pellet surface without imposing artificial boundary conditions there, as done in .   A recently proposed model for scaling pellet ablation rates in hot plasmas, utilizing transonic flow equations may be of limited applicability because of basic assumptions used in the model. (AIP) Comments on ’’Effect of transonic flow in the ablation cloud on the lifetime of a solid hydrogen pellet in a plasma’’: The Physics of Fluids.


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Model of an ablating solid hydrogen pellet in a plasma by Paul B. Parks Download PDF EPUB FB2

An analytical model for the ablation dynamics of a solid hydrogen pellet in a plasma was formulated. Molecules were vaporized off the surface of the pellet as a result of the elevated pellet surface by: 7.

A new model for calculating the ablation rate of a solid pellet injected into a neutral-beam-heated toroidal plasma is discussed. It is an extension of the neutral cloud shielding model. Abstract: A revised neutral molecule ablation model is derived to describe the evaporation of a solid hydrogen pellet in a tokamak plasma.

The approach taken is based on the theory of Parks, Turnbull, and Foster who postulate that a cloud of molecular hydrogen surrounding the pellet shields the surface from incoming energetic electrons and, in so doing, regulates the.

The scaling laws derived from the model indicate that the pellet lifetime varies as: where τ p is the lifetime of the pellet and T e, n e, and r p0 are the electron temperature, density of the plasma, and initial pellet radius, respectively.

A good agreement is found between this model and the ORMAK pellet injection by:   A model is formulated to describe the distortion of the magnetic field near an ablating solid hydrogen pellet in a plasma. The resistive, collision-dominated ablation cloud expands across the magnetic by: These scaling laws are based on an ablation model which visualizes the ablating pellet to be surrounded by a neutral hydrogen ablation cloud in the plasma.

Other authors have pointed out that in a thermonuclear plasma the ablation cloud may be highly ionized and may exclude the magnetic field in the torus from the ablation cloud with a possible decrease in energy flux to.

In order to exclude the effect of expansion geometry on the pellet ablation rate itself, we consider the ablation of a pellet in a constant area duct (see Fig. We imagine a cylindrical pellet of solid hydrogen to be inserted at the closed end of a rrictionless tube and subjected to the impact of a stream of plasma electrons.

A revised neutral molecule ablation model is derived to describe the evaporation of a solid hydrogen pellet in a tokamak plasma. A three-dimensional observation of the solid hydrogen pellet ablation has been performed by using a fast stereo imaging camera to investigate the pellet ablation dynamics.

The initial velocity component of the injected pellet is maintained during ablation in a hot plasma, and the pellet penetrates to the core plasma. On the other. ablating solid hydrogen pellet and collected by silicon photodiodes and a fast-frame camera system, under the assumptions that such emissions are loosely related to the ablation rate and that pellet radial acceleration in the plasma is negligible.

The ablation rate of the pellet, originally derived by Parks and Turnbull [36] and modified for hydrogen pellets by Kuteev [37] is given as (in atoms/s) where n e is the background plasma. A model is formulated to describe the distortion of the magnetic field near an ablating solid hydrogen pellet in a plasma.

The resistive, collision-dominated ablation cloud. Abstract. An ablation model for a hydrogen pellet accelerating in a thermonuclear facility fuel-injector bore is developed. The model is based on the Lagrange internal-ballistic problem complemented by the Stefan conditions on the ablating surface of the pellet Calculations demonstrate that, during pellet motion in the bore under the action of the gas, the pellet.

Request PDF | Effects of atomic processes on fuel pellet ablation in a thermonuclear plasma | The neutral-ablation model describing ablation of solid hydrogen fuel. thickness of an ablating solid-state pellet of 21density 10 cm−3 is on the order of 10−1/Z3/2 cm, and so for Z ˜ 1, the surface layer is much thinner than the radius of a typical pellet which is R p ∼ –1cm.

This layer forms a cold cloud of neutral atoms surrounding the pellet which throttles the heat flux reaching the pellet surface. The hydrogen pellet is surrounded by localized high density plasma, the so-called ablation cloud, immediately after plunging into the background plasma.

The ablation cloud emits intense radiation which helps us obtain clues for revealing plasma states in the pellet ablation cloud. Emission lines of neutral hydrogen obviously exhibit the.

Magnetic-field distortion near an ablating hydrogen pellet P.B. Parks-Analysis of low Z a impurity pellet ablation for fusion diagnostic studies P.B. Parks, J.S. Leffler and R.K. Fisher-Model of ablation flow near light-atom pellets with surface boundary conditions P.B. Parks, G.A. Gerdin, L.L.

Vahala et al.-Recent citations. various states of pellet are treated without assumptions. The model of “CAP” is constructed as follows. When a pellet consisting of solid hydrogen is heated by an energy flux, it changes to liquid and gas during phase transition and subsequently to plasma during atomic process.

In the present work, it is assumed that the ablation cloud. The line-of-sight of the observation device shown by the solid line and the trajectory of the ablating pellet meet at X cross, where X cross corresponds to a location where the line-of-sight and the magnetic field lines of interest are almost perpendicular.

It is necessary to target this location because the ablation clouds are roughly elongated following the direction of. Model of ablation flow near light-atom pellets with surface boundary conditions P.B.

Parks, G.A. Gerdin, L.L. Vahala et al.-A model for the ablation rate of a solid hydrogen pellet in a plasma P.B. Parks, R.J. Turnbull and C.A. Foster-Geometrical, kinetic and atomic physics effects in a two dimensional time dependent fluid simulation of.

A kinetic model is developed to determine the power deposition from energetic electrons into the neutral gas shield of an ablating high-Z high-Z, the velocity distribution of the hot electrons is nearly isotropic, and we use this feature to develop solutions to the kinetic contrast to pre-existing models, we consider the effect of gyro-motion.

The NGS model is derived by applying one dimensional, spherically symmetric and quasi-steady gas dynamics to the fluid ablating from a pellet in a thermonuclear plasma. And the model supposes the ablation cloud to consist of only one species, such as ground-state deuterium molecules.

Though the model is very simplified, it has been providing.The injection of frozen pellets composed of the isotopes of hydrogen has become the leading candidate for refueling fusion power reactors based on the tokamak concept.

This lofty position has been reached partly as a result of efforts to find an attractive solution to the perplexing problem of depositing atoms of fuel deep within the magnetically confined, hot plasma, and .