Towards the realization of magnetic megatesla


image: Illustration of a microtube implosion. Due to the hot electrons produced by the laser with energies of megaelectron volts, the cold ions from the surface of the inner wall implode towards the central axis. By pre-seeding uniform magnetic fields of the order of kilotesla, the Lorentz force induces a Larmor gyromotion of ions and imploding electrons. Due to the collective motion resulting from the relativistic charged particles around the central axis, strong spin currents of about peta-ampere / cm ^ 2 are produced with a few tens of nm, generating magnetic fields of the megatesla order.
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Credit: Masakatsu Murakami

Recently, a research team from Osaka University successfully demonstrated the generation of megaatesla (MT) order magnetic fields via three-dimensional particle simulations on the laser-matter interaction. The strength of MT magnetic fields is 1 to 10 billion times stronger than that of geomagnetism (0.3 to 0.5 G), and these fields should only be observed in close proximity to celestial bodies such as stars at neutrons or black holes. This result should facilitate an ambitious experiment to achieve magnetic fields of order MT in the laboratory, which is currently underway.

Since 19e century, scientists strove to achieve the highest magnetic fields in the laboratory. To date, the highest magnetic field observed in the laboratory is of the order of kilotesla (kT). In 2020, Osaka University’s Masakatsu Murakami proposed a new scheme called microtube implosions (MTI) [1, 2] to generate ultra-high magnetic fields on the MT command. Irradiation of a micron-sized hollow cylinder with ultra-intense, ultrashort laser pulses generates hot electrons with speeds close to the speed of light. These hot electrons initiate a cylindrically symmetrical implosion of ions from the inner wall towards the central axis. An applied pre-seeded magnetic field of the order of kilotesla, parallel to the central axis, curves the trajectories of ions and electrons in opposite directions due to the Lorentz force. Near the target axis, these curved trajectories of ions and electrons collectively form a strong spin current which generates magnetic fields of order MT.

In this study, one of the team members, Didar Shokov, conducted numerous three-dimensional simulations using the “OCTOPUS” supercomputer at the Cybermedia Center at Osaka University. As a result, a separate scaling law was found regarding the performance of generating magnetic fields by MTI and external parameters such as applied laser intensity, laser energy and target size.

“Our simulation showed that megatesla ultra-high magnetic fields, which were thought to be impossible to achieve on earth, can be achieved using today’s laser technology. The law of scale and the detailed temporal behavior of the magnetic fields in the target should facilitate laboratory experiments using the Peta-watt “LFEX” laser system at the Institute of Laser Engineering at Osaka University, which are currently ongoing, ”said Murakami.

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The article, “Laser scaling for generation of megateslamagnetic fields by microtube implosions” was published in High power laser science and engineering at DOI: https://doi.org/10.1017/hpl.2021.46

Reference:

[1] “Generation of megatesla magnetic fields by intense laser-driven microtube implosions”

Scientific reports 10, (2020) 16653. https://doi.org/10.1038/s41598-020-73581-4

[2] YouTube Murakami Lab: https://www.youtube.com/watch?v=eL4w1uGRk4U

About Osaka University

Osaka University was founded in 1931 as one of the Seven Imperial Universities of Japan and is now one of the leading comprehensive universities in Japan with a broad disciplinary spectrum. This strength is coupled with a desire for singular innovation that extends throughout the scientific process, from fundamental research to the creation of applied technologies with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world, being named the most innovative university in Japan in 2015 (Reuters 2015 Top 100) and one of the most innovative institutions in the world in 2017. (Innovative Universities and Nature Index Innovation 2017). Today, Osaka University is leveraging its role as a designated national academic society selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for the human well-being, the sustainable development of society and social transformation.

Website: https://resou.osaka-u.ac.jp/en


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