Acoustic microscopy and nonlinear effects in pressurized superfluid helium. Technical report

Technical Report · Tue Aug 31 04:00:00 EDT 1993

OSTI ID:5704553

Moulthrop, A A; Muha, M S; Kozlowski, G C; Silva, C P; Hadimioglu, B

The operation of an acoustic microscope having a resolution of 15 nm has been demonstrated. It uses as a coupling medium superfluid 4He colder than 0.9 K and pressurized to greater than 20 bar. The microscope is now being used to image objects that show little or no contrast on a scanning electron microscope. In addition, the acoustic microscope is being used to study the properties of sound propagation in the coupling fluid. At low acoustic intensities, the coupling fluid has very low acoustic attenuation at the microscope's operating frequency (15.3 GHz), but near the focal point the acoustic intensity can be high enough that the helium behaves with extreme nonlinearity. In fact, this medium is capable of entering new regimes of nonlinear interaction. Plots of the received signal versus input power display a nearly complete pump depletion at certain input power levels and a reconversion to the pump frequency at higher power levels. Such behavior has never before been observed. The authors present arguments that the process underlying this nonlinear behavior is harmonic generation. Cryogenic microscopy, Harmonic generation, Nonlinear acoustics.

• Research Organization: Aerospace Corp., El Segundo, CA (United States). Engineering and Technology Group
• OSTI ID: 5704553
• Report Number(s): AD-A-270598/6/XAB; TR--0091(6925-02)-1; CNN: F04701-88-C-0089
• Country of Publication: United States
• Language: English

Related Subjects

661210 -- Cryogenics-- (1992-)
665420* -- Superfluidity-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ACOUSTIC MICROSCOPY
CRYOGENICS
ELEMENTS
FLUIDS
FREQUENCY MIXING
GASES
HARMONIC GENERATION
HARMONICS
HELIUM
MICROSCOPY
NONLINEAR PROBLEMS
NONMETALS
OSCILLATIONS
RARE GASES
SOUND WAVES
SUPERFLUIDITY
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
WAVE PROPAGATION