Determination of confinement efficiency in tokamaks based on current independent flux loops technique Results in Physics 7 (2017) 175–177 Contents lists available at ScienceDirect Results in Physics j[.]
Results in Physics (2017) 175–177 Contents lists available at ScienceDirect Results in Physics journal homepage: www.journals.elsevier.com/results-in-physics Determination of confinement efficiency in tokamaks based on current independent flux loops technique A Salar Elahi ⇑, M Ghoranneviss Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran a r t i c l e i n f o Article history: Received 25 November 2016 Received in revised form 15 December 2016 Accepted 18 December 2016 Available online 24 December 2016 Keywords: Tokamak Confinement efficiency Poloidal flux loops a b s t r a c t In this contribution we presented a current independent approximation of the combination of poloidal beta and internal inductance (confinement efficiency) only based on poloidal flux loops measurement in IR-T1 tokamak The main advantage of this technique is that it based only on the one diagnostic (only flux loops and not need to plasma current measurement) Based on this method, two flux loops were designed, constructed, and installed on outer surface of the IR-T1 tokamak chamber and then the Shafranov parameter was measured from them Also the result of this technique was compared with conventional magnetic probes technique and found in good agreement with each other Ó 2016 The Author Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Introduction Equilibrium of the plasma within the vessel of the tokamak requires a suitably structured magnetic fields configuration These magnetic fields will act as a magnetic tube only as long as especial conditions are satisfied The confinement and equilibrium of the plasma within the discharge chamber of tokamak can be thought of as a problem of controlling the equilibrium position of the plasma column and the position of the plasma column with respect to its equilibrium position [1–20] If the equilibrium position of the plasma column can be made to be at the cross sectional center of the vacuum chamber, then a necessary condition for the plasma to be well confined is that the position of the plasma column from the center of the vacuum chamber be maintained to be less than a suitably small displacement In the low beta tokamaks as IR-T1, radial pressure balance is achieved by the poloidal field, and toroidal force balance is achieved by the Lorentz force But, in the toroidal force balance problem, if the two opposite forces are not equal, then plasma intend to shift inward or outward, which is dangerous for tokamak plasma equilibrium Therefore, plasma equilibrium study is one of the fundamental problems of the magnetically confined plasmas [21–45] There are many available experimental methods and analytical solutions of the steady state Magnetohydrodynamics (MHD) equations, in particular, the Grad-Shafranov equation Determination of the combination of poloidal beta and internal inductance (Shafranov parameter) (which is one of the ⇑ Corresponding author E-mail address: Salari_phy@yahoo.com (A Salar Elahi) tokamak plasma equilibrium parameters, K) is essential for tokamak experiments Very of plasma information can be deduced from this parameter, such as the poloidal beta, plasma equilibrium state, plasma energy, plasma confinement time, plasma toroidal current profile, and Magnetohydrodynamics (MHD) instabilities [46–57] In this paper we presented a current independent measurement of the Shafranov parameter only using poloidal flux loops in the IR-T1 tokamak, which is a small, air core, low beta, and large aspect ratio tokamak with a circular cross section (see Table 1) Details of this technique for the measurement of the Shafranov parameter will be presented in ‘Current independent measurement of the Shafranov parameter’ section Experimental results and comparison with conventional magnetic probes technique also will be presented in ‘Experimental result and comparison with conventional magnetic probes technique’ section Also summary and conclusion will be discussed in last section Current independent measurement of the Shafranov parameter The poloidal flux loops are a simple toroidally loops which measures the poloidal magnetic flux and an array of loops is usually used in control and reconstruction of plasma equilibrium states The magnetic flux passing through such a loop is equal to 2pw, where w represents magnetic poloidal flux In the ohmically heated tokamaks, ohmic coils field is the main fraction of poloidal flux which passing through the flux loop Therefore to obtain net poloidal flux due to plasma, compensation is required for all excessive flux Because of large area of the flux loop, the inductive voltage is also large and then it consists of usually one turn According to http://dx.doi.org/10.1016/j.rinp.2016.12.015 2211-3797/Ó 2016 The Author Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) 176 A Salar Elahi, M Ghoranneviss / Results in Physics (2017) 175–177 Table Parameters of the IR-T1 tokamak Table Parameters of the poloidal flux loops Parameters Value Two flux loops parameters Values Major radius Minor radius Toroidal field Plasma current Discharge time Electron density 45 cm 12.5 cm