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We investigated the expansion features of laser- produced Al plasma in the presence of 0.8 T magnetic field. Fast-gated photography was used to record 2-D snapshots of plasma at various moments during its expansion. The slowing down and stopping of the plasmas were observed at all laser irradiance levels used (3-10 GW·cm �2 ), however, increasing con- vexity of the plasma periphery was noticed at higher irradiance levels. C ONTROLLING the parameters of laser-produced plasmas (LPPs) is very important for most of its applications. A magnetic field is capable of providing such control by influencing the dynamic, ionization, and optical properties of a LPP (1), (2). The presence of magnetic field during the expansion of the plume may lead to plasma confinement, ion acceleration, enhanced emission intensity, instabilities, focusing and so on (3), (4). In this paper, we report the dynamics of expanding laser-plasma under a transverse B field studied using fast gated photography. We investigated the changes in the morphology of laser- produced plumes under different irradiation conditions expanding in vacuum into a 0.8 T magnetic field. For plasma-B field interaction experiments, a magnetic trap was fabricated using Nd-based rare-earth magnets. Magnetic circuits closed by magnetic steel provided an approximately uniform field, as well as field strength, in the gap nearly twice as high as the case with an isolated pair of magnetized plates. With this configuration, we obtained a magnetic field ∼0.8 T, measured using a Gauss meter. An Al target was positioned at equi-center between the pole edges of the two magnets. For producing plasmas, the Al target was irradiated using pulses from a Q-switched Nd:YAG laser with 6-ns full width half maximum at 1064 nm and focused using a f/40 plano convex lens to a spot size of ∼1 mm. The laser pulse energy at the target surface was varied using a combination of half wave plate and cube polarizer. All experiments were done in a vacuum chamber with a base pressure ∼10 −5 torr. An intensified CCD (ICCD) camera was used to capture time resolved images of the expanding plasma in the presence and absence of the B field.

The six papers in this special issue were originally presented at the 38th IEEE International Conference on Plasma Science (ICOPS), held in Chicago, IL, from June 26 to June 30, 2011.

We report a large jetlike collimated emission feature from colliding laser-produced plasmas (LPPs). The plasmas are produced by focusing two parallel laser beams on a planar copper target. Time-resolved spectrally integrated emission features in the visible region are recorded using an intensified charge-coupled device camera. Both laser plasmas expanded perpendicular to the target and collided side-on. The jetlike emission has a spatial extension of more than 3 cm and exists in a prolonged time compared with single LPPs.

The dynamics and confinement of laser generated Carbon plumes expanding across a transverse magnetic field have been investigated. 1.06-/spl mu/m, 8-ns pulses from an Nd:YAG laser were used to create a plasma that was allowed to expand across a 0.64-T magnetic field. Fast photography employing an intensified charged-coupled device was used for two-dimensional imaging of the plume. Photographic studies showed the collapse of the ablation plume after the bubble lifetime, and formation of two lobes near the target surface at later times.