Diagnostics for Kinematics on MTF at NRL

The Material Test Facility (MTF) houses a medium-caliber electromagnetic (EM) railgun that is designed for ease of access. As such, it is ideal for developing diagnostics for measuring the performance of EM launchers. Multiple in situ diagnostics have been fielded on the MTF railgun including field sensors for position location and thermal sensors. Kinematics of the launch package are of particular interest. B-dot loops are the usual method, but many such B-dots are required to obtain a detailed evolution of position and velocity. This requires many channels and consumes data acquisition resources. Naval Research Lab (NRL) has developed several versions of a flux ladder diagnostic, which include many pick-up loops on one data channel. Some versions have multiple flux ladders interleaved to maintain pulse separation in a single channel, but which increase the overall spatial resolution. A typical MTF configuration has 58 positions monitored in just three channels. Careful processing has yielded velocity and even acceleration. NRL is also developing a flux loop diagnostic that has the potential for continuous kinematics with the time resolution of the digital sampling rate. However, flux loops are more sensitive to spurious signal sources. Preliminary flux loop results are presented.