Generation of Quasistatic Magnetic Fields in the Relativistic Laser-Plasma Interactions

Susumu KATO, Tatsufumi NAKAMURA1), Kunioki MIMA2), Yasuhiko SENTOKU3), Hideo NAGATOMO2), Yoshiro OWADANO

National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, 305-8568, Japan
1) National Institute of Radiological Sciences, Inage, Chiba, Chiba, 263-8555, Japan
2) Institute of Laser Engineering (ILE), Osaka University, Suita, Osaka, 565-0871, Japan
3) Physics department, University of Nevada, Reno, Reno, NV 89557, USA

Laser plasma interaction in the relativistic regime is crucial for inertial fusion energy with the fast ignitor scheme [1] and for multi-MeV proton and electron generation. Especially, the energy transport are greatly affected by quasi static magnetic fields [2]. The magnetic fields are generated by various mechanisms, which are the radiation pressure associated with the laser pulse itself, the current of fast electrons generated during the interaction, Weibel instability and so on [3,4]. At the oblique incidence, the magnetic field is localized on the plasma surface, which depth is less than a laser wavelength and which amplitude is about one third of the laser field [5].

The magnetic field generation at the oblique incidence is investigated by a two dimensional particle-in-cell simulation. There are the magnetic fields of three types in the irradiation of both s polarized and p polarized laser. First type is a surface magnetic field which arises very quickly, of which raising time is almost the same of the laser raising time [6]. Second type is gradually growth magnetic field of which growth direction is the laser incidence one. The magnetic field is growth in a inside plasma by the Weibel instability [4], which occurs between the fast electrons generated by the J × B heating and their return currents. Final type magnetic field penetrates from surface into the inside plasma. The growth direction is perpendicular to the surface. The magnetic field appears in the end of the simulation time.

References

[1]M. Tabak et al., Phys. Plasmas 1, 1626 (1994); R. Kodama et al., Nature 412, 798 (2001).
[2]Y. Sentoku et al., Phys. Rev. E 65, 46408 (2002).
[3]S. C. Wilks et al., Phys. Rev. Lett. 69, 1383 (1992).
[4]Y. Sentoku et al., Phys. Plasmas 7, 689 (2000).
[5]F. Brunel, Phys. Fluids 31, 2714 (1988).
[6]T. Nakamura et al., Proceedings of the Third International Conference on Inertial Fusion Sciences and Applications (IFSA2003) (to be published).

A part of this study was financially supported by the Budget for Nuclear Research of the Ministry of Education, Culture, Sports, Science and Technology, based on the screening and counseling by the Atomic Energy Commission.