SearcharxivSearch

arXiv subjects

Yoichi Sakawa

Publications and source records attributed to Yoichi Sakawa.

2 recordsLinked to original sources

Pulse magnet of 10 T for power laser experiments with x-ray free-electron laser diagnostics

The importance of investigating magnetized plasmas/solids in extreme conditions has grown over the last decades, particularly in the field of high energy density physics (HEDP), such as laboratory astrophysics and inertial confinement fusion. However, up to now, the unique capabilities of an X-ray free-electron laser (XFEL), such as high brilliance and low divergence have never been exploited for this type of research. In this paper, we present the first platform developed at SACLA, Japan, that combines a high-power optical laser for generating matter under extreme conditions of pressure and temperature, an XFEL probe, and an external magnetic field. The high current is produced using a 2 kV, 4.8 kJ pulsed power system giving a maximum current of 10 kA which is synchronized with the optical laser and XFEL in a vacuum environment. It flows through a split-pair coil to generate a high magnetic field (10 T at 6 kA) which has 1 cm access every 45$^{\circ}$ in the equatorial plane and 90$^{\circ}$ in the poloidal one. This platform offers new opportunities to study high-energy-density matter in strong magnetic fields, including shock propagation, instability growth, and turbulent plasma dynamics.

physics.plasm-ph

Whistler wave plasma production in CHS

Rf plasma production in Whistler waves range of frequency f/fci >1 is applied on the compact helical system (CHS) in a steady state operation with low toroidal magnetic field strength, where f and fci are rf and ion cyclotron frequencies, respectively. Maximum rf power and pulse width are is170kW and 10 msec at 9MHz, respectively. The line averaged plasma density as high as 2x10^18 m-3 (He plasma) is produced in the region of toroidal magnetic field strength on magnetic axis B=100G~1.5kG and the electron temperature measured at plasma periphery is about 20eV. The wave magnetic field strength measured at the plasma periphery showed the evidence of the toroidal eigen modes of the Whistler waves. The additional long pulse microwave heating of 2.45GHz (>200msec) is applied and it sustains the plasmas while the microwave itself can not ignite plasmas when B<600G.

physics.plasm-ph