Recently, a research team at Osaka University has successfully demonstrated
the generation of megatesla (MT)-order magnetic fields via three-dimensional
particle simulations on laser-matter interaction. The strength of MT
magnetic fields is 1–10 billion times stronger 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 black holes. This result should
facilitate an ambitious experiment to achieve MT-order magnetic fields in
the laboratory, which is now in progress.
Since the 19th century, scientists have strived to achieve the highest
magnetic fields in the laboratory. To date, the highest magnetic field
observed in the laboratory is in the kilotesla (kT)-order. In 2020,
Masakatsu Murakami at Osaka University proposed a novel scheme called
microtube implosions (MTI) to generate ultrahigh magnetic fields on the
MT-order. Irradiating a micron-sized hollow cylinder with ultraintense and
ultrashort laser pulses generates 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 central
axis, bends the trajectories of ions and electrons in opposite directions
because of the Lorentz force. Near the target axis, those bent trajectories
of ions and electrons collectively form a strong spin current that generates
MT-order magnetic fields.
In this study, one of the team members, Didar Shokov, has extensively
conducted three-dimensional simulations using the supercomputer OCTOPUS at
Osaka University's Cybermedia Center. As a result, a distinct scaling law
has been found relating the performance of the generation of the magnetic
fields by MTI and such external parameters as applied laser intensity, laser
energy, and target size.
"Our simulation showed that ultrahigh megatesla magnetic fields, which were
thought to be impossible to realize on earth, can be achieved using today's
laser technology. The scaling law and detailed temporal behavior of the
magnetic fields in the target are expected to facilitate laboratory
experiments using the Peta-watt laser system 'LFEX' at Osaka University's
Institute of Laser Engineering, which are now in progress," Murakami says.
Reference:
D. Shokov et al, Laser scaling for generation of megatesla magnetic fields
by microtube implosions, High Power Laser Science and Engineering (2021).
DOI: 10.1017/hpl.2021.46
Tags:
Physics