May 18, 2024

Towards Megatesla Magnetic Fields by Microtube Implosions

In this research study, among the employee, Didar Shokov, has actually thoroughly performed three-dimensional simulations using the supercomputer “OCTOPUS” at Osaka Universitys Cybermedia Center. As an outcome, an unique scaling law has been discovered relating the efficiency of the generation of the electromagnetic fields by MTI and such external specifications as applied laser strength, laser energy, and target size.
” Our simulation showed that ultrahigh megatesla magnetic fields, which were believed to be difficult to recognize on earth, can be achieved utilizing todays laser innovation. The scaling law and detailed temporal habits of the electromagnetic fields in the target are anticipated to help with laboratory experiments using the Peta-watt laser system LFEX at Osaka Universitys Institute of Laser Engineering, which are now in development,” Murakami says.
Reference: “Laser scaling for generation of megatesla magnetic fields by microtube implosions” by D. Shokov, M. Murakami and J. J. Honrubia, 14 October 2021, High Power Laser Science and Engineering.DOI: 10.1017/ hpl.2021.46.
Notes.

Illustration of a microtube implosion. Due to the laser-produced hot electrons with megaelectron volt energies, cold ions in the inner wall surface area implode toward the main axis. By pre-seeding uniform electromagnetic fields of the kilotesla order, the Lorentz force causes a Larmor gyromotion of the imploding ions and electrons. Due to the resultant cumulative movement of relativistic charged particles around the main axis, strong spin currents of around peta-ampere/cm ^ 2 are produced with a couple of 10s of nm size, creating megatesla-order magnetic fields. Credit: Masakatsu Murakami
High-precision 3D supercomputer simulations reveal the 3D structure of theoretically forecasted micron-scale megatesla electromagnetic fields, enhancing engineering design of laser conditions and micron-size target structures for future laser experiments.
Viewpoint views of the normalized ion density ni/ni0 and the z-component of the electromagnetic field Bz, respectively, observed at t ~ 200 fs, which is obtained by a 3D EPOCH simulation. A cubic aluminum target with a size of 14 µm × 14 µm × 14 µm is set at the center, which has a round cavity with a radius of R0 = 5 µm and an axis overlapping the z-axis. The seed electromagnetic field B0 = 6 kT parallel to the z-axis is uniformly set over the entire domain. The 4 faces of the target parallel to the z-axis are typically irradiated by consistent laser pulses all at once, which are defined by? L = 0.8 µm, IL =3 × 10 ^ 21 Wcm ^ -2 and tL =50fs. Credit: © 2021 Masakatsu Murakami et al., High Power Laser Science and Engineering
Recently, a research study group at Osaka University has effectively demonstrated the generation of megatesla (MT)- order electromagnetic fields by means of three-dimensional particle simulations on laser-matter interaction. The strength of MT electromagnetic fields is 1-10 billion times more powerful than geomagnetism (0.3-0.5 G), and these fields are expected to be observed only in the close vicinity of celestial bodies such as neutron stars or great voids. This result ought to help with an ambitious experiment to accomplish MT-order electromagnetic fields in the lab, which is now in progress.
Because the 19th century, researchers have actually strived to achieve the highest electromagnetic fields in the lab. To date, the highest magnetic field observed in the lab remains in the kilotesla (kT)- order. In 2020, Masakatsu Murakami at Osaka University proposed an unique plan called microtube implosions (MTI) [1, 2] to produce ultrahigh electromagnetic fields on the MT-order. Irradiating a micron-sized hollow cylinder with ultraintense and ultrashort laser pulses creates hot electrons with velocities close to the speed of light. Those hot electrons launch a cylindrically symmetric implosion of the inner wall ions towards the central axis. An applied pre-seeded magnetic field of the kilotesla-order, parallel to the main axis, bends the trajectories of ions and electrons in opposite instructions since of the Lorentz force. Near the target axis, those bent trajectories of electrons and ions jointly form a strong spin present that produces MT-order electromagnetic fields.

By pre-seeding consistent magnetic fields of the kilotesla order, the Lorentz force induces a Larmor gyromotion of the imploding electrons and ions. Due to the resultant cumulative movement of relativistic charged particles around the central axis, strong spin currents of around peta-ampere/cm ^ 2 are produced with a few 10s of nm size, creating megatesla-order magnetic fields. The strength of MT magnetic fields is 1-10 billion times more powerful than geomagnetism (0.3-0.5 G), and these fields are expected to be observed only in the close area of celestial bodies such as neutron stars or black holes. A used pre-seeded magnetic field of the kilotesla-order, parallel to the central axis, bends the trajectories of ions and electrons in opposite instructions since of the Lorentz force. Near the target axis, those bent trajectories of electrons and ions collectively form a strong spin current that creates MT-order magnetic fields.

” Generation of megatesla magnetic fields by intense-laser-driven microtube implosions” by M. Murakami, J. J. Honrubia, K. Weichman, A. V. Arefiev and S. V. Bulanov, 6 October 2020, Scientific Reports.DOI: 10.1038/ s41598-020-73581-4.
YouTube Murakamis laboratory: https://www.youtube.com/watch?v=eL4w1uGRk4U.