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The XPM research group (Experimental Magnetized Plasma Physics) is one of the experimental groups at the PIIM Institute.

Experimental research in basic plasma physics of turbulent plasmas is conducted on a toroidal device with rotational transform.

Machine à plasma MISTOR
Machine à plasma MISTOR

The MISTOR plasma device produces a magnetized plasma torus including a central toroidal conductor producing a poloidal magnetic field. The plasma is created by thermionic discharge or by microwave discharge operated at a frequency close to the electron cyclotron frequency.

This original design makes it possible to study the stabilization of turbulence by the magnetic shear. A very long confinement time is obtained, 10 times longer compared to classical SMT’s. A very stable plasma and very dense plasma is obtained when a low radial electric field is established. Recent investigations have exhibited a Bohm diffusion. This device performs a plasma confinement efficiency 50 times better than the confinement of energy in tokamaks, taking into account the low magnetization in this device.

- As in tokamaks, a magnetic divertor configuration allows to obtain a central confined plasma surrounded by a Scrape-Off-Layer.

Research Program :

- Characterization of low-frequency instabilities induced by the ExB drift of ions and electrons and related anomalous transport. The most unstable frequency is driven by a Rayleigh-Taylor mechanism when the ExB drift velocity of the ions is reduced by the collisions between ions and neutrals. This basic instability is the classical "Simon-Hoh" instability (1963).

- Turbulence studies in a magnetized toroidal plasma with magnetic shear. The Simon-Hoh instability has been found to be the dominant instability at low magnetic field.

- GAM’s (Geodesic Acoustic Modes) are intrinsic low-frequency modes in this device. The toroidal ion acoustic resonance is modified by the poloidal rotation of the plasma induced by the radial electric field. This unique system has not been studied previously in a laboratory plasma device. Chaotic regimes are recorded and the dynamical control of complex spatiotemporal regimes is obtained.

- The electron trapping inside the banana orbits (similar to banana orbits in tokamaks) has been detected and the related toroidal current has been measured. This situation is very similar to the Ring Current observed in the ionosphere.

- Thiéry PIERRE, Senior Scientist CNRS, Directeur de Recherches

Recent Papers (2008 - -)

- Toroidal magnetized plasma device with sheared magnetic field lines using an internal ring conductor, Th. Pierre, Rev. Sci. Instrum. 84, 013504, 2013
- Ion velocity distribution function investigated inside an unstable magnetized plasma exhibiting a rotating nonlinear structure, C. Rebont, N. Claire, F. Doveil and T h. Pierre, Phys. Rev. Lett , 106, 225006, 2011
- Direct observation of a cross-field current-carrying plasma rotating around an unstable magnetized plasma column, S. Jaeger and Th. Pierre, Physics of Plasmas 92, 2009
- High frequency harmonic generation in a toroidal magnetized laboratory plasma and detection of plasma turbulence, A.Ajendouz, Th. Pierre, M. Boussouis, and K. Quotb, Europhysics Letters 81, 15001, 2008