In our ordinary detonics experiments, the timing measurements are generally done with passive optical fiber sensors. Each sensor end is fitted with a metallic cap which contains a specially machined air chamber known as the "ionization chamber." When a projected metallic plate shocks the sensor, the air located in the ionization chamber receives a strong shock, which ionizes both the trapped air and the fiber silica core. The emitted light travels down the fiber to the slit of an electronic streak camera or an optic/electric converter coupled with a digitizer. One of our main objectives is to measure the shock breakout time very accurately. Such a measurement is practically impossible to make on a sensor of this type due to low shock pressure level and the difficulty of making contact between the sensor and the target especially in complex devices. This is why we have developed a new probe called "active fiber." This probe is located close to the surface (less than 3 mm) and is composed of two fibers; the first is used to illuminate the target with a laser source and the second collects the back-reflected light which is then analyzed with a photo-detector. It is a "no contact" measurement for shock breakout chronometry. At target impact, a light signal is produced according to the capped passive optical fiber principle. When the dynamic pressure level is low (150 kbar) we obtain a better chronometric accuracy.

Date Published: 1 August 2003
PDF: 6 pages
Proc. SPIE 4948, 25th International Congress on High-Speed Photography and Photonics, (1 August 2003); doi: 10.1117/12.516946

Published in SPIE Proceedings Vol. 4948:
25th International Congress on High-Speed Photography and Photonics
Claude Cavailler; Graham P. Haddleton; Manfred Hugenschmidt, Editor(s)