Optical resonant ultrasound spectroscopy for spherical target characterization
- Los Alamos National Laboratory
A new non-contact resonant ultrasound spectroscopic technique is employed to determine the response characteristics of spherical fusion targets, with particular emphasis on both the displacement sensitivity and frequency response of the technique. The optical experimental method is based on photorefractive optical lock-in detection scheme with narrow bandwidth amplification to measure phase variations in light scattered from optically rough, continuously vibrating surfaces with very high, linear sensitivity and a noise level on the order of 10.6 nanometers RMS. This high sensitivity is needed to determine the vibrational modes of the gas inside an spherical target separately from the elastic modes of the containment shell. These measurements can be used to calculate the pressure and density of the internal gas. This approach is also used to discriminate between nearly-degenerate resonant modes characteristic of the frequency spectrum when the target fabrication is inadequate (non-uniform shell thickness, misalignment of hemispheres) or when the Deuteriumrrritium solid fuel inside the target is not symmetrically distributed at cryogenic temperatures. Asymmetries in the fuel layering and geometric perturbations disturb the target implosion process creating deleterious effects in fusion energy generation. The technique is applied to determine the modal characteristics of a target sphere with known response from 100 KHz to 450 KHz. The results demonstrate the unique capabilities of the optical lock-in detection method to measure very small resonant ultrasonic signals.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1020971
- Report Number(s):
- LA-UR-10-04252; LA-UR-10-4252; TRN: US201116%%649
- Resource Relation:
- Conference: 2nd International symposium on laser ultrasonics ; July 5, 2010 ; Talence, France
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AMPLIFICATION
CONTAINMENT SHELLS
CRYOGENICS
DENSITY
DETECTION
DEUTERIUM
FABRICATION
FUELS
IMPLOSIONS
LASER TARGETS
LASERS
NOISE
SENSITIVITY
SHELLS
SIGNALS
SOLID FUELS
SPECTROSCOPY
SPHERES
SURFACES
TARGETS
TRITIUM
ULTRASONIC WAVES
VARIATIONS
VISIBLE RADIATION