SHIVA X-ray Source Experiments

Abstract

The SHIVA X-ray source development program at the Air Force Weapons Laboratory is exploring plasma implosion concepts as potential sources of an energetic X-ray source. The SHIVA load is a type of electromagnetically driven plasma implosion characterized by use of a high density (n = 10¹⁸/cc) plasma liner, by very short implosion times on the order of a microsecond, and by final velocity exceeding 15–20 cm/μ sec. The load parameters are chosen to optimize energy coupling to kinetic energy during the implosion. Instability growth during the implosion is countered by both the very short implosion time and by a variety of techniques such as the use of axially converging electrodes. Thermalization of directed implosion kinetic energy when the plasma stagnates on itself in the center is the prime heating mechanism employed to generate the hot plasma needed for a radiation source. Experiments conducted using a 1.1 MJ, 3 mΩ capacitor bank operating at 100 KV to drive a SHIVA load initially 7 cm in diamenter and 2 cm high have given results in excellent agreement with two dimensional magnetohydrodynamic computer calculations. Results showed final velocity well in excess of 15 cm/μ sec, 200–300 KJ of kinetic energy coupled to the imploding cylinder, thermalization time of less than 100 ns and radiation pulses of 150 KJ characterized by temperature of 30–50 eV. Comparison of electrical power delivered to the load to radiation power observed disclose a factor of 2 power multiplication. Work is proceeding to increase capacitor bank stored energy to 1.9 MJ and to increase charge voltage to 120 KV to allow more energetic future experiments to be performed.