Principles of Complex Interferometry and its application in Measurements of Spontaneous Magnetic Fields in Laser-Produced Plasma

Generation of spontaneous magnetic fields (SMF) is one of the most interesting phenomena accompanying the interaction of intense laser radiation with matter. SMF above 1 MG may significantly change plasma transport coefficients and thereby affect the plasma density and temperature distributions, absorption of laser radiation and, ultimately, the value of ablation pressure [1]. In context of the inertial confinement fusion (ICF), in particular in those related to the fast ignition concept, the knowledge about mechanisms of SMF generation in compressed plasma and their influence on emission of the fast electrons is necessary [2]. Additionally, knowledge about SMF is useful in astrophysical research to model objects and phenomena in the universe [3].

The various methods of registering and investigating the SMF have been developed, however the most reliable and efficient is the method based on the magnetooptic Faraday effect. The main advantage of this method is that it provides information about magnetic fields distribution in the entire area of investigated plasma. Nevertheless it is difficult to implement and requires simultaneous measurements of an angle of polarization plane rotation of a probe wave and plasma electron density. In classical polaro-interferometry these values are provided independently by polarimetric and interferometric measurements. A particularly useful approach to measure SMF is complex interferometry[4], which involves obtaining information about SMF directly from a phase–amplitude analysis of an image called a complex interferogram [5].

Since its first effective implementation in studies of SMF distributions at Prague Asterix Laser System (PALS) in Czech Rapublic [6], complex interferometry has been used for SMF measurements in many experiments related to ICF or astrophysics research. Multi-frame variant of complex interferometry allows to obtain spatial-temporal distributions of current density and estimate average electron velocity [7]. Particular interesting application of complex interferometry were studies on process of magnetized plasma formation using specially constructed targets [8][9].

During the lecture, the theoretical foundations of polaro-interferometric measurements and complex-interferometry will be discussed. Particular attention will be devoted to explaining the methodology of the amplitude–phase analysis of complex interferograms and the results of experiments in which complex interferometry has been used will be presented.

References

[1] T. Pisarczyk et al., Laser Res. 11, 1 (1990)
[2] H. Shiraga et al., Nucl. Fusion 54, 054005 (2014)
[3] J. J. Santos et al., New J. Phys., 17, 083051 (2015)
[4] M. Kálal, Czech. J. Phys., 41, 743 (1991)
[5] A. Zaraś-Szydłowska et al. AIP Advances 10, 115201 (2020)
[6] T. Pisarczyk et al., Phys. Plasmas, 22, 102706 (2015)
[7] T. Pisarczyk et al., PPCF, 62 115020 (2020)
[8] T. Pisarczyk, S.Y. Gus’kov, A. Zaras-Szydłowska et al:, Sci Rep 8, 17895 (2018)
[9] T. Pisarczyk et al., PPCF, 64 115012 (2022)