A study of beam ion and deuterium–deuterium fusion-born triton transports due to energetic particle-driven magnetohydrodynamic instability in the large helical device deuterium plasmas. (17th August 2021)

• Record Type: Journal Article
• Authors: Ogawa, K.; Isobe, M.; Nuga, H.; Kamio, S.; Fujiwara, Y.; Kobayashi, M.I.; Sangaroon, S.; Takada, E.; Seki, R.; Yamaguchi, H.; Murakami, S.; Jo, J.; Osakabe, M.
• Is Part Of: Nuclear fusion. Volume 61:Number 9(2021)
• Publication Date: 2021-08-17
• Subjects: large helical device -- energetic particle confinement -- magnetohydrodynamic instability -- neutron diagnostics; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/ac0d8a
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: Understanding energetic particle transport due to magnetohydrodynamic instabilities excited by energetic particles is essential to apprehend alpha particle confinement in a fusion burning plasma. In the large helical device (LHD), beam ion and deuterium–deuterium fusion-born triton transport due to resistive interchange mode destabilized by helically-trapped energetic ions (EIC) are studied employing comprehensive neutron diagnostics, such as the neutron flux monitor and a newly developed scintillating fiber detector characterized by high detection efficiency. Beam ion transport due to EIC is studied in deuterium plasmas with full deuterium or hydrogen/deuterium beam injections. The total neutron emission rate ( S n ) measurement indicates that EIC induces about a 6% loss of passing transit beam ions and a 60% loss of helically-trapped ions. The loss rate of helically-trapped ions, which drive EIC, is larger than the loss rate of passing transit beam ions. Furthermore, the drop of S n increasing linearly with the EIC amplitude shows that barely confined beam ions existing near the confinement-loss boundary are lost due to EIC. In full deuterium conditions, a study of deuterium–deuterium fusion-born triton transport due to EIC is performed by time-resolved measurement of total secondary deuterium–tritium neutron emission rate ( S n_DT ). Drop of S n_DT increases substantially with EIC amplitude to the third power and reaches up to 30%. The relation shows that not only tritons confined in confined-loss boundary, but also tritons confined in the inner region of a plasma, are substantially transported.