Project Title:
Optical-Fiber Velocimeter for Flows in Hypersonic and Supersonic Flight
03.05-7637
910802
Optical-Fiber Velocimeter for Flows in Hypersonic and Supersonic Flight
Candela Laser Corporation
530 Boston Post Road
Wayland
MA
01778
Rafael A.
Sierra
508-358-7637
LaRC
NAS1-19520
034
03.05-7637
910802
Abstract:
Optical-Fiber Velocimeter for Flows in Hypersonic and Supersonic Flight
A new airborne instrument for velocimetry of the external and internal flows of re-entry,
hypersonic, and supersonic vehicles will be developed. This technique may also prove
useful for temperature measurement. Based on the time-of-flight approach, the instrument
uses laser-generated N2 ions as tracers and delayed laser-induced fluorescence for
imaging. Two recent advances make this innovation possible: the identification of
an efficient photo-ionization of N2 and the development of a new burst-mode, Q-switched,
frequency-doubled, Ti:Sapphire laser. The new laser can deliver two high-energy,
tunable laser pulses using a single flashlamp pulse. The first pulse is used to write
a tracer line by tuning it to the ionizing transition of N2. The second pulse is
used, after a preset delay, to induce fluorescence that is detected by a solid-state
digital camera. The all-solid-state system is robust and may be made into a low-volume,
low-power, minimally intrusive, highly accurate, and reliable device.
This instrument will also be useful for wind tunnels and combustion diagnostics.
In addition, the UV laser will find use as a resonance ionization source for mass
spectrometric analysis of ultra trace elements in biological samples in medical research.
Other applications of the laser include spectroscopy and materials research.
optical velocimeter, tunable Ti:Sapphire laser, photo-ionization, Q-switched laser