Phys. Rev. Lett. 108, 235005 (2012)

The plasma that is produced when a high-power laser is directed onto a solid target is of interest to researchers working in fields as diverse as laboratory astrophysics, particle acceleration and fusion energy. However, the extreme nature of these plasmas makes it difficult to study and control them. Now, Ravi Kumar of the Tata Institute of Fundamental Research in Mumbai and co-workers have shown that targets made of carbon nanotubes can overcome some of these problems.

The primary role of the laser in this work is to ionize the atoms in the target, but it also exerts forces on the ions and electrons that make up the plasma, and these interactions can lead to the generation of extremely high electron currents and magnetic fields. Such currents and fields are potentially useful, but the electron current, for example, can only travel a very short distance through the plasma before it breaks up into filaments.

Kumar and co-workers from India, the UK and the US illuminated their nanotube target with a high-power laser at the Tata Institute and found that magnetic fields as high as 120 megagauss were generated. Computer simulations confirmed that the electron currents must travel through the target, which is 1,100 μm thick, without breaking up. This is about 100 times longer than the typical distance travelled by an electron current in a laser-produced plasma.