Optical pins for sub-nanosecond resolution of detonation break out

We report on the design and tests of optical pins that we have shown to resolve the arrival of a detonation front with a resolution of \textless 1ns. We coat the end of single-mode fiber with a 1000 {\AA}ngstr\"{o}m layer of aluminum and butt it against a detonator in various locations. Using an IR interferometer with the reference leg shifted in frequency (the type used for Photon Doppler Velocimetry), the disappearance of the fringes allows a measurement of the arrival of the detonation front to \textless 200 ps. The detonation arrival time measured with the optical pin and IR interferometer agree within the resolution of the measurement. A more field-able and affordable alternative using APDs \underline {A}valanche \underline {p}hoto\underline {d}iodes to measure the disappearance of the light reflected from the aluminum coating yields a resolution of 1ns. We present the design details and performance proof tests. LA-UR-13-21216