Late time magnetic field in laser produced plasmas

Abstract

Summary form only given. Magnetic fields have long been known to be generated in laser produced plasmas during the laser pulse. Measurements have shown that megagauss magnetic fields are generated in the focal region of the laser. It is generally believed that these large magnetic fields dissipate through collisional or collisionless processes. However, there are measurements of magnetic fields at large distances from the target. The question then is to determine if these magnetic fields are transported in the expanding plasma. Previous measurements of magnetic fields far from the target involve the plasma expanding into a surrounding gas. Here we present the results of magnetic field measurement in plasma whose pressure is significantly greater than the ambient pressure. The laser target was a high density polyethylene. Magnetic probes were placed at several distances from the target. The probes at the farthest distance, 70 cm, were differentially wrapped and measured three orthogonal projections of the field. Faraday cups were used to measure the time of flight of the ions. A Langmuir probe was used to determine electron temperature.