Tokamak Chauffage Alfvén Brésilien

The Tokamak Chauffage Alfvén Brésilien (TCABR) is a tokamak situated at the University of São Paulo (USP), Brazil.^[1][2] TCABR is the largest tokamak in the southern hemisphere and one of the magnetic-confinement devices committed to advancing scientific knowledge in fusion power.

Photograph of TCABR in USP's Plasma Physics Laboratory.

History

TCABR was originally designed and constructed in Switzerland, at the École Polytechnique Fédérale de Lausanne (EPFL), and operated there from 1980 until 1992, under the name of Tokamak Chauffage Alfvén (TCA).^[1] The main focus of TCA was to assess and enhance plasma heating with Alfvén waves. In 1994, the machine was transferred to USP, passing through an upgrade and adding Brésilien to its name. The operation of TCABR began in 1999.^[1]

Properties

3D virtual model of the TCABR tokamak.

The TCABR plasma is made of hydrogen and has a circular format.^[1][3] In general, its discharges are ohmically heated and the plasma current in TCABR reaches up to ${\displaystyle I_{P}\leq 100\ {\text{kA}}}$. The minor and major radii of TCABR are respectively ${\displaystyle a=18.0\;{\text{cm}}}$ and ${\displaystyle R=61.5\;{\text{cm}}}$, giving an aspect ratio of ${\displaystyle A=R/a=3.4}$. The TCABR central electron temperature is around ${\displaystyle k_{B}T_{e}\leq 650\ {\text{eV}}}$ (i.e., ${\displaystyle T_{e}\sim 6\times 10^{6}\;{\text{K}}}$) and its mean electron density is ${\displaystyle 0.9\leq {\bar {n}}_{e0}\leq 3}$, in units of ${\displaystyle 10^{19}\;{\text{m}}^{-3}}$.^[1][3] Other parameters of TCABR include the toroidal magnetic field, ${\displaystyle B_{0}\sim 1.1\;{\text{T}},}$ the hydrogen filling pressure, ${\displaystyle P_{H}\simeq 3\times 10^{-4}\;{\text{Pa}}}$, a discharge duration of ${\displaystyle T_{D}\simeq 100\;{\text{ms}}}$, and a steady-phase duration around ${\displaystyle T\leq 60\;{\text{ms}}}$.^[1]

Parameters of TCABR^[1][2][4]

Parameter	Symbol	Value
Plasma format		Circular
Plasma composition	H	Hydrogen
Major radius	${\displaystyle R_{0}}$	${\displaystyle 61.5{\text{ cm}}}$
Minor radius	${\displaystyle a}$	${\displaystyle 18.0{\text{ cm}}}$
Aspect ratio (${\displaystyle R_{0}/a}$)	${\displaystyle A}$	${\displaystyle 3.4}$
Plasma current	${\displaystyle I_{p}}$	${\displaystyle \leq 100\ {\text{kA}}}$
Central (or toroidal) magnetic field	${\displaystyle B_{0}}$	${\displaystyle \sim 1.1\ {\text{T}}}$
Line-averaged electronic density	${\displaystyle {\overline {n}}_{e0}}$	${\displaystyle 0.9\sim 3\times 10^{19}\ {\text{m}}^{-3}}$
Central electronic temperature	${\displaystyle k_{B}T_{e0}}$	${\displaystyle \sim 0.5\ {\text{keV}}}$
Hydrogen filling pressure	${\displaystyle P_{H}}$	${\displaystyle 1\sim 3\times 10^{-2}\ {\text{Pa}}}$
Discharge duration	${\displaystyle T_{D}}$	${\displaystyle \simeq 100\ {\text{ms}}}$
Duration of the steady phase	${\displaystyle T}$	${\displaystyle \leq 60\ {\text{ms}}}$

Research program

The current purpose of the TCABR tokamak includes the study of Alfvén waves,^[1][5][6] but is not restricted to it. Other research areas are (i) the characterization of magnetohydrodynamic (MHD) instabilities,^[1][7] (ii) the study of high-confinement regimes induced by electrical polarization of external electrodes in the plasma edge,^[3][7][8] (iii) the investigation of edge turbulence,^[3][9] and (iv) the study of plasma poloidal and toroidal rotation using optical diagnostics.^[1][10][11] The TCABR team is also associated with a theoretical group focused on investigating instabilities and transport barriers in tokamaks and dynamical systems.^[12][13]

An upgrade in the TCABR is also being conducted.^[14][15][16] A set of 108 RMP coils will be installed to control and study edge localized modes (ELMs). New shaping coils will be added, allowing great flexibility in plasma configurations (e.g. single null, double null, snowflake, and negative triangularity configurations).^[16] The vacuum-vessel inner wall of TCABR will receive graphite tiles to decrease impurity deposition and energy loss in the plasma.