Ideas for overseas contributions to CMSO Piero Martin Consorzio RFX Associazione Euratom-ENEA sulla fusione And Physics Dept., Univ. of Padova, Italy CMSO General Meeting Madison, WI – Aug. 6-8, 2004 With contributions from RFX, MST, EXTRAP T2R and TPE-RX groups

The new RFX device Main new components: saddle coils, covering the whole plasma boundary, each independently powered and feedback controlled 2.a smoother and thinner shell 3.the first wall with higher power handling capabilities 4.an in-vessel system of magnetic and electrostatic probes 5.the toroidal field power supply R /a = 2.0 / 0.46 (m) - I up to 2 MA

Overview of the magnetic boundary - 4 coils in the poloidal direction: 90° spaced – 48 coils in the toroidal direction: 7.5° spaced shell vessel Active saddle coils

Saddle coil performance each independently powered 24 kAt: 400 A x 60 turns Wide spectrum of Fourier components can be produced: m=1,2 n 24 DC < f < 100 Hz Significant amplitude available. For example: edge br for (1,8) mode: 20 Hz 1.3 Hz

Magnetic probe 97 Electrostatic (Langmuir) probes 139 Magnetic pick up probes 8 Calorimetric probes Langmuir probe Integrated System of the Internal Sensors (ISIS)

RFX and CMSO activities Active feedback control of magnetic turbulence in a laboratory plasma device with FULL COVERAGE of the plasma surface. Active feedback control of magnetic turbulence in a laboratory plasma device with FULL COVERAGE of the plasma surface. Selective depression/excitation of selected MHD instabilities Selective depression/excitation of selected MHD instabilities Dynamo studies Dynamo studies Resistive Wall Modes control Resistive Wall Modes control Magnetic turbulence control Magnetic turbulence control ………… ………… … together with strong plasma diagnostic capabilities! … together with strong plasma diagnostic capabilities!

The Single Helicity (SH) dynamo a theoretically predicted state with a unique m = 1 saturated resistive kink (a pure helix wound on a torus), a theoretically predicted state with a unique m = 1 saturated resistive kink (a pure helix wound on a torus), Stationary LAMINAR dynamo mechanism with good helical flux surfaces Stationary LAMINAR dynamo mechanism with good helical flux surfaces Escande, Martin et al., PRL 85 (2000)

Dynamo electric field in QSH Dynamo in QSH becomes more concentrated in one mode than in standard MH plasmas! Dynamo in QSH becomes more concentrated in one mode than in standard MH plasmas! Piovesan, Craig, Marrelli, Martin, submitted to PRL

QSH coherent structure

Remember we can apply with the saddle coils up to ~20 mT on a single m=1 mode Numerical studies on active control: successful drive and sustainment of m=1 n=7 SH state starting from MH conditions Low dissipation conditionsLow dissipation conditions Thin shellThin shell Simoultaneous active control of RWMs !Simoultaneous active control of RWMs ! Paccagnella, MHD workshop 2002

Preliminary experiments in the EXTRAP T2R RFP RFX equipment tested in the EU EXTRAP T2R device at KTH in Stockholm RFX equipment tested in the EU EXTRAP T2R device at KTH in Stockholm QSH spectra excited in a high aspect ratio device! QSH spectra excited in a high aspect ratio device! More experiments underway More experiments underway

Test particle transport studies: magnetic stochasticity vs. order SHQSHMH

Numerical simulation predicts better confinement in SH With the ORBIT code a set of test particles is deposited in the plasma core in MH/QSH/SH and followed in their outward motion. With the ORBIT code a set of test particles is deposited in the plasma core in MH/QSH/SH and followed in their outward motion. Particle loss time estimated; confinement SH > QSH > MH Particle loss time estimated; confinement SH > QSH > MH Poloidal angle Predebon et al, submitted to PRL

Upgraded soft x-ray tomography for MST Two more fans added: total 4 Two more fans added: total 4 Franz et al., RSI 2004

Imaging of individual small islands in the plasma core SXR image Numerical reconstruction of magnetic field lines Franz et al., PR:L 2004