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First Experiment in 70 Tesla magnet

The first experiments in a 70 Tesla monolithic coil were performed at the LNCMI in Toulouse. The experiment studied the dynamic alignment of carbon nanotubes in a magnetic field. Magnetic field is generated with a distributed reinforcement monolithic coil energized with the mobile 1MJ capacitor bank usually used at the ESRF or at the ILL. This coil is a prototype; a version adapted to the 14MJ capacitor bank will be in use in December 2009 (see also Coils).

Figure: (left) Magnetic field profile, (right) Spectra of nanotubes at the maximum field.

The goal is to observe the alignment of carbon nanotubes with optical methods. One particular difficulty is to turn the light beamer over 90° since the experiment requires a light beam perpendicular to the magnetic field. Thus we need a sample holder which is small enough to hold optical fibres, lenses and prisms in 7 mm. Two shots have to be performed with 2 different light polarisations. One parallel to the magnetic field and the other one perpendicular to the magnetic field. The source is a Ti:Sapphire laser providing a wavelength of 985 nm for this experiment. After bringing the 2 measurements into relation we can follow the alignment of carbon nanotubes versus time and magnetic field. In the Figure, we show the two corresponding spectra at maximum field. This work was performed at room temperature in a helium cryostat. This means that experiments in 70 Tesla down to 1.5 Kelvin are accessible without problems.

Contact : Nicolas Ubrig, Jérôme Béard