Comparison Of Velocimetry and Reflectometry To Investigate Time of Arrival Diagnostic (TOAD) Probe Function

As a diagnostic, time of arrival may be viewed as any method to record shockwave or detonation front arrival with temporal accuracy. Common methods include electrical foils, piezoelectric pins, and shorting pins; all of which are electrically based. The Time of Arrival Diagnostic (TOAD) developed at the Los Alamos National Laboratory (LANL) is a fiber optic analog to piezoelectric pins. It has become a commonly fielded shock physics diagnostic at LANL. It is simple, low cost, and has inherent safety near high explosives. Occasionally, TOAD data is observed to have more than one inflection, which may obscure the shock arrival. A series of controlled experiments were conducted to better understand the shock loading process at the TOAD probe. The experiments consisted of a stationary aluminum target with imbedded TOAD probes that were impacted with tantalum flyer plate. These experiments were performed at the powder gun facility at the Special Technologies Laboratory (Mission Support and Test Services) in Santa Barbara, CA. By diverting a portion of the TOAD signal to a Photon Doppler Velocimetry system, a comparison between the two optical diagnostics was conducted. The results of these experiments will be discussed in this talk.