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MAGNETIC DIFFUSION IN A SHOCK-PRODUCED PLASMA
MASSACHUSETTS INST OF TECH CAMBRIDGE RESEARCH LAB OF ELECTRONICS
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The problem is treated of a plasma, produced by a shock wave, moving along a cylindrical shock tube and encountering an inhomogeneous, axially symmetric magnetic field. The output of a search coil is related to the magnetic Reynolds number of the flow, and the magnitude of the magnetic Reynolds number for which the magnetic field can begin to strongly affect the plasma flow is found. The behavior at the limits of very lowAND VERY HIGH MAGNETIC Reynolds numbers is calculated for the condition that the imposed magnetic field does not affect the plasma flow. The calculated behavior is then compared at the limits with measurements made with the use of a solid copper slug. It was found that a magnetic Reynolds number, Rm, greater than 60 is necessary to exclude a large fraction of the magnetic field from the interior of the conductor. Magnetic diffusion effects are not measurable until an Rm of 5 is reached, and the exclusion of more than 90 of flux from the search coil does not occur until Rm greatly exceeds 100. Measurements made with plasmas indicate that an appreciable fraction of the magnetic field is excluded from the plasma at high shock velocities, which gives the conditions necessary for studying the effects of magnetic forces on the plasma flow. Comparison with the copper slug measurements AD-258 204 shows that a Rm of 20 was reached and allows the conductivity of the plasma to be calculated and compared with its theoretical values. Author
APPROVED FOR PUBLIC RELEASE