  Production of the huge longitudinal magnetic fields by using an ultraintense
laser pulse irradiating a solenoid target is considered. Through
three-dimensional particle-in-cell simulations, it is shown that the
longitudinal magnetic field up to ten kilotesla can be observed in the
ultraintense laser-solenoid target interactions. The finding is associated with
both fast and return electron currents in the solenoid target. The huge
longitudinal magnetic field is of interest for a number of important
applications, which include controlling the divergence of laser-driven
energetic particles for medical treatment, fast-ignition in inertial fusion,
etc., as an example, the well focused and confined directional electron beams
are realized by using the solenoid target.
