Development of an ITER Pellet Fueling System in Russia

Kuteev, B. V.; Viniar, I.; Sergeev, V. Yu.; Tsendin, L. D.; Kapralov, V. G.; Koblents, P. Yu.; Lovtsius, Andrey A.; Parshin, Michael A.; Reznichenko, P. V.; Skoblikov, S. V.; Umov, A. P.; Skripunov, V. N.

doi:10.13182/fst94-a40229

Cited by 7 publications

(6 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The scaling was obtained for a uniform distribution of the heating power inside the cloud, a monoenergy electron heat flux and a sonic-transonic regime in the molecular hydrogen flow. Our recent analysis of the cloud gas dynamics with Maxwellian electrons [27] has confirmed this scaling. Only the numerical factor is to be reduced by 0.66.…”

Section: (46supporting

confidence: 62%

Hydrogen pellet ablation and acceleration by current in high temperature plasmas

Kuteev

1995

Nucl. Fusion

View full text Add to dashboard Cite

Hydrogen pellet ablation and acceleration by current in high temperature plasmas are analysed. The present state of ablation theory and experiment is discussed and an ablation model is formulated. This model takes into account the energy distribution of the particles (both electrons and ions)participating in the ablation process, electrostatic effects of the cloud charging and changes of the pellet form during ablation. Without charging the pellet form tends to a shape resembling a lentil while it remains almost spherical if charged. A new algorithm for ablation rate calculations that can be used for an arbitrary initial form of the pellet is described. The results of this kinetic two dimensional approach differ from those of the Parks ablation scaling used in the ITER design by not more than 30%. Plasma shielding effects are not significant in the ablation if strong turbulence in the cloud is taken into account. Acceleration analysis is based on the Braginskii corrected electron distribution function. For the lentil mode of ablation, acceleration is higher than those for the charged mode by a factor of 1.76. The ablation models are compared with the experiments on T-10, JET, TFTR, Heliotron-E and Tore Supra. A sensitivity analysis shows that pellet size and electron temperature are the most significant factors for determination of the penetration length. The available database of penetration lengths is not sufficient for distinguishing between the models. Acceleration for the charged mode correlates with experimental data better than that for the lentil mode. The effect of the hot ions is seen on the ablation. Finally, ablation at reactor relevant plasma and pellet parameters is considered. This range of the plasma parameters needs a correction of the ablation scaling as follows: dN/dt approximately ne0.453Te1.72rp1.443Mi-0.283 where ne and Te are the electron density and temperature, respectively, and rp and Mi are the pellet radius and at

show abstract

Section: (46supporting

confidence: 62%

Hydrogen pellet ablation and acceleration by current in high temperature plasmas

Kuteev

1995

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…The main idea is that the effective area intercepting the electron heat flux, i.e., the projected area of the pellet normal to the B field is the main factor that determines the ablation rate. 10,11,14 For a spherical pellet, the projected area is half the surface area of the pellet, hence the factor of 2 reduction. A different result, factor of ϳ0.68 reduction, was found in MacAulays's simulation, 11 although it should be mentioned that the simulation in 1D ͑isotropic heating͒ was not possible.…”

Section: Ablation With Anisotropic Heatingmentioning

confidence: 99%

“…A further approximation, especially for energetic electrons with EϾ300-500 eV, is to neglect the weak energy dependence in the Coulomb logarithm. The solution of the kinetic equation for the distribution function of electrons traveling in the right ϩz ͑left Ϫz) directions that have penetrated a line-integrated density ϩ ( Ϫ ) is given by 10,29,30 f Ϯ ͑ E,, Ϯ ͒ϭ f max ͑ EЈ͒ ͩ When the ablation cloud is fully ionized and has no bulk motion, the heating rate given by Eq. ͑1c͒ and the definition of e in Eq.…”

Section: Appendix: Derivation Of Semianalytic Kinetic Heat Flux Exprementioning

confidence: 99%

“…1͑b͒ we display the 1D geometry used in the construction of the isotropic heating approximation. Both the monoenergetic and spherically symmetric approximations were partially removed by Kuteev,10 who used the actual Maxwellian distribution for the incident electrons, and attempted to account for the heating asymmetry imposed by the magnetic field. Although the ablation flow itself was forced to be spherically symmetric, and everywhere sonic ͑Mach number ϭ1͒, the pellet ablation rate was nevertheless in very good agreement with MacAulay's 2D numerical simulation of pellet ablation, where these geometrical effects were treated.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Two-dimensional simulation of pellet ablation with atomic processes

et al. 2004

View full text Add to dashboard Cite

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 previous ablation models. The simulation includes multispecies atomic processes, mainly molecular dissociation and thermal ionization in the ablation flow beyond the pellet, with a kinetic heat flux model. It was found that ionization causes the formation of a quasistationary shock front in the supersonic region of the ablation flow, followed by a ''second'' sonic surface farther out. Anisotropic heating, due to the directionality of the magnetic field, contributes to a nonuniform ablation ͑recoil͒ pressure distribution over the pellet surface. Since the shear stress can exceed the yield strength of the solid for a sufficiently high heat flux, the solid pellet can be fluidized and flattened into a ''pancake'' shape while the pellet is ablating and losing mass. The effect of pellet deformation can shorten the pellet lifetime almost 3ϫ from that assuming the pellet remains rigid and stationary during ablation.

show abstract

“…This is because the net particle flux is relatively small due to backscatter in the high-Z case. The diffusion equation, equation (14), indicates that the incident electron flux scales as n ∞ v th /Z 1/2 , which is a factor Z 1/2 lower as compared to the case when there is no scattering. This particle flux is used to calculate the sheath potential in the appendix, and we show that the sheath potential required to maintain ambipolarity scales as Z −1/3 .…”

Section: Physics Modelmentioning

confidence: 99%

Heating and ablation of high-Z cryogenic pellets in high temperature plasmas

Fontanilla¹,

Breǐzman²

2019

Nucl. Fusion

View full text Add to dashboard Cite

A kinetic model is developed to determine the power deposition from energetic electrons into the neutral gas shield of an ablating high-Z pellet. For high-Z, the velocity distribution of the hot electrons is nearly isotropic, and we use this feature to develop solutions to the kinetic equation. In contrast to pre-existing models, we consider the effect of gyro-motion as well as elastic scattering of the hot electrons. Two limits are considered: when the gyro-frequency is much greater than the elastic collision frequency, the hot electrons diffuse longitudinally along the field lines as they slow down; but if the gyro-frequency is much less than the elastic collision frequency, the hot electrons diffuse radially. In both limits, it is possible to express the kinetic equation describing the hot electrons independently of the gas density profile, and therefore, the power deposition model is universal in this respect. The emphasis on elastic scattering yields an ablation rate which scales as Z−7/6 which is different than Z−2/3 shown in Sergeev et al (2006 Plasma Phys. Rep. 32 5). It is also shown that the sheath potential required to maintain ambipolarity in the cloud scales as Z−1/3. Fluid simulations yield ablation rates that scale with the four-thirds power of the pellet radius in agreement with [].

show abstract

Development of an ITER Pellet Fueling System in Russia

Cited by 7 publications

References 5 publications

Hydrogen pellet ablation and acceleration by current in high temperature plasmas

Hydrogen pellet ablation and acceleration by current in high temperature plasmas

Two-dimensional simulation of pellet ablation with atomic processes

Heating and ablation of high-Z cryogenic pellets in high temperature plasmas

Contact Info

Product

Resources

About