Upgrades of the RFX-mod reversed field pinch and expected scenario improvements

Abstract

RFXmod is a Reversed Field Pinch device that allowed performing experiments in regimes with a plasma current up to 2 MA, thanks to its MHD active control system. Experiments have shown that improved plasma performances are obtained when in the resonant part of the m = 1 spectrum one dominant tearing mode is much higher than the other secondary ones (quasi single helicity states). Tearing modes play a crucial role in determining energy and particle transport. Based on the present understanding of the interplay between passive conductive boundaries and tearing modes in an RFP, an upgrade of RFXmod machine assembly has been designed, dubbed RFXmod2, and it is now being implemented. The highly resistive Inconel vessel will be removed, graphite tiles will be attached to the copper stabilizing shell and the stainless steel support structure will be modified in order to be vacuum tight. In RFXmod2, the shellplasma proximity decreases from b/a = 1.11 to b/a = 1.04 and copper, instead of Inconel, will be the continuous conducting structure nearest to the plasma. MHD nonlinear simulations show that secondary tearing modes amplitude and the edge bulging due to their phase locking will decrease; moreover the plasma current threshold for tearing modes wall locking will also significantly increase.

A Data-Assimilation Based Method for Equilibrium Reconstruction of Magnetic Fusion Plasma and its Application to Reversed Field Pinch

“…where B ϕ0 , n 0 , T 0 are given as B ϕ0 = 0.1 T, n 0 = 10 19 m −3 and T 0 = 10 6 K, respectively. In the present numerical experiment, the artificial data m 1 , m 2 , • • • , m 6 are obtained by giving the value of p true as [4,3,3,5,4,3] t . We apply the reconstruction algorithm with starting from some different initial guesses.…”

“…The objective of this paper is to propose a new method for reconstructing the equilibrium state of magnetic fusion plasma and to propose a method for applying it to reversed field pinch (RFP). Some research programs for the RFP configuration are in progress because of its potential of a compact fusion reactor [4]- [8]. Rigorous (accurate) modeling and mathematical formula- VOLUME 4, 2016 tion of the equilibrium for fusion plasma are difficult problems.…”

Effective Area Measurements of Magnetic Pick-Up Coil Sensors for RFX-mod2

“…The RFX-mod2 experiment is a major upgrade of the reversed field pinch (RFP) magnetic confinement experiment RFX-mod with the aim of improving the control of magnetic confinement, plasma density, and plasma wall interaction in both RFP and Tokamak configuration [1,2], with plasma pulse duration up to 5 s. The upgrade consists in the removal of the highly resistive vacuum vessel, so that the copper passive stabilizing shell (PSS) will be the conducting structure nearest to the plasma. In particular, the PSS will be deeply modified in order to operate in vacuum conditions sustaining the new first wall and the wide system of in-vessel diagnostics.…”

Diagnostic data integration using deep neural networks for real-time plasma analysis

“…In this context the RFX consortium hosts RFXmod, that is one of the most controllable experiments currently active in fusion research [2] [3]. A further update to this experiment (RFX-mod2) is ongoing, aiming at improving the responsiveness of the machine, together with the renewal of the sensory system [4]. The research application described in the present work fits in this environment with a specific design proposal that shows how DNN could be integrated in the overall chain of data acquisition and control (CODAS).…”