Compact system for high-speed velocimetry using heterodyne techniques

• Published in: Review of scientific instruments 2006-08, Vol.77 (8), p.083108-083108-8
• Main Authors: Strand, O. T., Goosman, D. R., Martinez, C., Whitworth, T. L., Kuhlow, W. W.
• Format: Article
• Language: English
• Subjects: DIGITIZERS; FOURIER TRANSFORMATION; GHZ RANGE 01-100; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; LASERS; OPTICAL FIBERS; VELOCIMETERS; VELOCITY
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.2336749

We have built a high-speed velocimeter that has proven to be compact, simple to operate, and fairly inexpensive. This diagnostic is assembled using off-the-shelf components developed for the telecommunications industry. The main components are fiber lasers, high-bandwidth high-sample-rate digitizers, and fiber optic circulators. The laser is a 2 W cw fiber laser operating at 1550 nm . The digitizers have 8 GHz bandwidth and can digitize four channels simultaneously at 20 GS ∕ s . The maximum velocity of this system is ∼ 5000 m ∕ s and is limited by the bandwidth of the electrical components. For most applications, the recorded beat frequency is analyzed using Fourier transform methods, which determine the time response of the final velocity time history. Using the Fourier transform method of analysis allows multiple velocities to be observed simultaneously. We have obtained high-quality data on many experiments such as explosively driven surfaces and gas gun assemblies.