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Sains Malaysiana 46(9)(2017): 1385–1392 http://dx.doi.org/10.17576/jsm-2017-4609-05
Formation and Sustainability of H-mode Regime in Tokamak Plasma via Source Perturbations Based on Two-Field Bifurcation Concept (Pembentukan dan Kelestarian Rejim H-mod
pada Plasma Tokamak melalui Pengusikan Sumber Berdasarkan Konsep Dua-Bidang Dwicabang) B. CHATTHONG1*
& T. ONJUN2 1Department of Physics, Faculty of
Science, Prince of Songkla University, Hat Yai, Songkla,
90110, Thailand 2School of Manufacturing Systems
and Mechanical Engineering, Sirindhorn International Institute of
Technology, Thammasat University, Pathum Thani, Thailand Diserahkan:
31 Ogos 2016/Diterima: 10 November 2016 ABSTRACT A set
of coupled particle and thermal transport equations is used to study
a formation and sustainability of an edge transport barrier (ETB)
in tokamak plasmas based on two-field bifurcation. The two transport
equations are numerically solved for spatio-temporal profiles of
plasma pressure and density. The plasma core transport includes
both neoclassical and turbulent effects, where the latter can be
suppressed by flow shear mechanism. The flow shear, approximated
from the force balance equation, is proportional to the product
of pressure and density gradients, resulting in non-linearity behaviors
in this calculation. The main thermal and particle sources are assumed
to be localized near plasma center and edge, respectively. It is
found that the fluxes versus gradients regime illustrates bifurcation
nature of the plasma. This picture of the plasma implies hysteresis
properties in fluxes versus gradients space. Hence, near marginal
point, the perturbation in thermal or particle sources can trigger
an L-H transition. Due to hysteresis, the triggered H-mode can be
sustained and the central plasma pressure and density can be enhanced. Keywords:
ETB;
fusion; L-H transition; plasma; tokamak ABSTRAK Satu
set gandingan zarah dan persamaan angkutan terma digunakan untuk
mengkaji pembentukan dan kelestarian halangan angkutan pinggiran
(ETB)
dalam plasma tokamak berdasarkan dua medan dwicabang. Dua persamaan
angkutan diselesaikan secara berangka untuk profil ruang-masa tekanan
plasma dan ketumpatan. Teras plasma mengangkut kedua-dua kesan neoklasik
dan turbulens, dengan turbulens boleh disekat melalui mekanisme
aliran ricih. Aliran ricih, penghampiran daripada persamaan keseimbangan
daya, adalah berkadaran dengan produk tekanan dan kecerunan ketumpatan
yang mengakibatkan tingkah-laku yang tak linear dalam pengiraan
ini. Sumber utama terma dan zarah masing-masing adalah diandaikan
setempat berhampiran pusat plasma dan pinggiran. Didapati bahawa
rejim kecerunan menggambarkan dwicabang semula jadi plasma. Gambaran
plasma ini membayangkan sifat histeresis dalam fluks berbanding
ruang kecerunan. Oleh yang demikian, berhampiran titik marginal,
pengusikan di dalam sumber terma atau zarah boleh mencetuskan peralihan
L-H. Oleh sebab histeresis, pencetus H-mod dapat dikekalkan dan
ketumpatan tekanan tengah plasma boleh dipertingkatkan. Kata kunci: ETB;
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