A Model of Pellet Ablation with a Multi-Species Ablatant

C.T. Chang, K. Thomsen, S. Piret

    Research output: Book/ReportReportResearch

    206 Downloads (Pure)

    Abstract

    The single species neutral - shielding model for the ablation of a hydrogenic pellet is extended by considering the ablatant as a mixture of four species: molecular and atomic hydrogen, protons and electrons. Compared with the singlespecies - ablatant model, results of the analysis showed that the ablatant state differs considerably. The attenuation of the incoming electron energy and energy flux, however, are very much similar, irrespective of the ablatant composition. The scaling law of the pellet ablation rate with respect to the plasma state of Te, ne and the pellet radius, rp remains the same; the ablation
    rate is reduced approximately by 15%. at some combinations of Te, ne and rp, a weak shock can appear when the ablated flow downstream becomes sonic. A sufficient but not necessary condition for its occurence is that the ablacant approaches either a state of complete dissociation, or complete ionization. To study the possible existence of an effective energy absorbing spherical region around the pellet, a comparison between the local ablated electron collisional mean free path and the electron Larmor radius in the cloud is made. A critical field, Bc is then defined and evalued at the ionization radius, ri. For plasma 
    state of fusion interest and pellet radius beyond 0.15 mm, Bc is well above 10 Tesla.
    Original languageEnglish
    Place of PublicationRoskilde
    PublisherRisø National Laboratory
    Number of pages50
    ISBN (Print)87-550-1466-6
    Publication statusPublished - 1988
    SeriesRisø-M
    Number2748
    ISSN0418-6435

    Keywords

    • Risø-M-2748

    Cite this

    Chang, C. T., Thomsen, K., & Piret, S. (1988). A Model of Pellet Ablation with a Multi-Species Ablatant. Risø National Laboratory. Risø-M, No. 2748