Probing thermal Weibel instability in optical-field-ionized plasmas using relativistic electron bunches

• Published in: Plasma physics and controlled fusion 2020-02, Vol.62 (2), p.24010
• Main Authors: Zhang, Chaojie, Huang, Chen-Kang, Marsh, Ken A, Joshi, Chan
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; electron probe; kinetic plasma instability; magnetic fields; magnetic fields; optical field ionization; optical field ionization; Weibel instability
• ISSN: 0741-3335; 1361-6587
• DOI: 10.1088/1361-6587/ab61e0

Thermal Weibel instability driven by anisotropic velocity distributions is an important mechanism for self-generating magnetic fields in both laboratory and space plasmas. However, there is a lack of experimental data on thermal Weibel instability due to the difficulty of initializing anisotropic distributions in a controllable manner as well as the challenge of probing the magnetic fields with high spatiotemporal resolution. Here we show that the initial electron velocity distribution of optical-field-ionized plasmas can be easily manipulated by changing laser polarization and such plasmas are unstable to the thermal Weibel instability. The topology of the self-generated magnetic fields depends on the laser polarization. We propose to use ultrashort relativistic electron beams such as those produced by a laser wakefield accelerator as a probe to record the spatiotemporal evolution of the magnetic fields. By taking a series of snapshots of the magnetic fields at different times, the wavevector spectrum and growth rate of the instability can be deduced and compared with kinetic theory.