Power flow in a multi-terawatt radiation source

Much of the research emphasis in the development of z-pinches as intense X-ray sources has been directed toward increasing the power flow into the load. Near the load, linear current densities in excess of 500 kA/cm are not uncommon. To achieve these very high power flow density levels, it is necessary to construct low-inductance (a few nanohenries), sub-ohm impedance, vacuum transmission lines. These transmission lines depend upon the current´s self-magnetic fields to prevent significant electron flow across the millimeter gaps separating the highly stressed electrodes. Because of the intense radiation generated by the plasma source and its time varying nature, power flow from the source can be diverted from the load and reduce the radiation output. This limitation in the power delivered to the plasma is recognized as a major impediment to increasing radiation output. A variety of geometrical and radiation environment considerations make it difficult to develop monitors which can accurately determine the current loss by direct measurement. This paper describes some of the techniques used on the Phoenix radiation effects simulator to measure and improve its output, along with results from these efforts. In particular, a discussion of vacuum power flow including the main features of a new insulator stack design is presented, along with a description of some of the unique features of the Phoenix gas valve design, the results of simulator prepulse measurements, and the implication of prepulse on simulator performance.