Study of the collisional effects and increasing perpendicular magnetic field on the expansion of a laser produced plasma.

Laser produced plasmas have been used to study shock, astrophysical, and fusion phenomena. In our study, we have utilized the highly uniform superconducting magnets of the Magnetic Dusty Plasma Experiment (MDPX) to better understand the cross-field motion of a moderately dense, 10¹⁸ #/cm³, across a broad range of magnetic field strengths. MDPX allowed us to measure the behavior of plasmas generated by a Nd:YAG laser focused onto a cylindrical carbon fiber target in magnetic fields up to 3.25 Tesla. The background pressures were also varied from 100 mTorr to 300 mTorr to observe the effects of collisionality on the plasma structure. We were able to capture the structure of the laser produced plasma using an intensified charge couple device (ICCD) with time resolution of 3 ns. The images obtained were taken perpendicular and parallel to the plasma expansion and the magnetic field. We measured the plasma expansion out to a time of 1000 ns and found that with increasing field the critical radius of the plasma expansion decreased as the magnetic field got stronger. We also observed a bifurcation in the plasma expansion as the plasma expanded over time.