Magnetic Velocity Gauges: Effects of Misalignment
Embedded velocity gauges are standardly used at LANL on gas gun experiments of a shock to-detonation transition. The experiments are intended to be one-dimensional with a planar shock driven by the projectile from a gas gun propagating along the axis of the HE cylinder. As disussed by Gustavsen et al. [1999], the accuracy of the gauges depends on the alignment of the directions of shock propagation, magnetic field and the active gauge element. A source of inaccuracies is from tilt or misalignment angle at impact between the projectile surface and the HE surface; typically a few milliradians. This leads to the shock propagating at a slight angle to the axis of the HE cylinder and can affect the shock rise time of the velocity gauges, the time offset between the tracker gauges for the trajectory of the lead shock, and the gauge positions in the direction of propagation. It is important to note that tilt is characterized by 2 parameters; the magnitude of the angle relative to the HE axis and the direction in the plane transverse to the HE axis. Here we derive the uncertainties from tilt to leading order in the tilt angle.