Opening Switch Utilizing Shock Wave Induced Conduction in PMMA and PVC

Summary form only given. The feasibility of utilizing shock loaded and unloaded dielectrics as a true closing/opening switch as part of an explosive-driven pulse power system is addressed. While it is known that shock wave compressed PVC and PMMA become conductive, the details of the material's recovery from the conducting back to the insulating state are much less known. To be effective as an opening switch, the recovery time has to be minimized, i.e., for instance, heating of the material must be minimized. The two primary sources of heat in the switch are shock induced heating and switch loss heating. These sources must be balanced for optimal results. Furthermore, it is also important to determine if the observed temporal behavior is due to finite shock unloading or intrinsic material relaxation properties. In the extreme case, bulk breakdown may occur during recovery as voltage increases across the switch. Previous work, performed primarily with a C-4 packed compression rod, has achieved a switch on-state resistance of less than 1 ohm, with an average on-state duration of 80 microseconds. It was also shown that PMMA appears to have a much sharper transition time than PVC, between both insulator to conductor, and conductor to insulator. The results presented here use a timed explosion to more carefully control the intensity and duration of the shock wave. This allows for more control over shock induced heating of the sample. We will present recent experimental data and discuss results as they relate to the development of an opening switch.