Physical Acoustics

Acousto-Optic Imaging

physical-acoustics-figThis project deals with the physical interaction of diffuse light and focused ultrasound.  Photons that enter the interaction region are phase modulated at the ultrasound frequency.  A photorefractive-crystal-based detector then converts the phase modulation into an intensity modulation.  The flux of acoustically “tagged” photons serves as an indication of the local optical, acoustical and acousto-optic properties of the medium, which is normally tissue.  By physically scanning the ultrasound focal spot, images based on both acoustical and optical contrast can be generated.  Indeed, we have developed a system that uses a commercial diagnostic ultrasound machine to both generate a conventional B-Mode ultrasound images and drive the acousto-optic interaction.  In this way, we can generate automatically co-registered images of both the structural and optical properties of a tissue region.  The project is supported by NSF via the Center for subsurface Sensing and Imaging Systems (CenSSIS), with supplemental support from industry (Analogic Corp.).

  • Faculty: Cleveland, and Roy
  • Students: L. Sui (Ph.D. 2006), P. Lai (PhD), A Draudt (PhD)

 

Laser Nucleation and Collapse Stability for Advanced Cavitation Power Technology

Among the many issues at the forefront of today’s world, none is more critical than the search for a long-lasting, inexpensive and less polluting energy source. As part of a consortium of university and private labs, BU is conducting basic research whose ultimate aim will be to achieve controlled, inertially-confined thermonuclear fusion, which produces heat energy that can ultimately yield electricity. Unlike other attempts at large-scale, controlled thermonuclear fusion, which use high magnetic field or laser-driven implosion, the consortium will utilize high-power acoustics to expand vapor cavities in a high-pressure liquid.  The natural collapse of the vapor cavities is dominated by the inertia of the inrushing liquid, thus providing an intrinsic inertial confinement for the plasma inside the cavity.  The BU effort will focus on controlling cavity clusters by employing a focused array of laser beams to nucleate optimal clusters.  This effort is funded by the Department of Defense.

  • Faculty: Holt
  • Students: A. Kondo (MS), P. Anderson (PhD), J. Sukovich (PhD)

High-speed image sequence of twin laser-nucleated bubble clusters collapsing and emitting shock waves.  Time increases left to right, top to bottom.  The interframe time is 2 microseconds.

High-speed image sequence of twin laser-nucleated bubble clusters collapsing and emitting shock waves. Time increases left to right, top to bottom. The interframe time is 2 microseconds.

 

Mitigation of Cavitation Damage in the ORNL Spallation Neutron Source

ornl-imageThe most powerful pulsed-neutron source in the world is housed at Oak Ridge National Laboratory in Oak Ridge, Tennessee.  A high power pulsed proton beam is directed into a stainless steel container filled with mercury.  The ensuing spallation event results in a short burst of neutrons that are collected and directed to an array of user facilities.  Evidence suggests that cavitation associated with the spallation process might shorten the lifetime of the mercury target containment vessel.  We are engaged in a three-faceted project aimed at (1) developing technology for monitoring the presence of gas bubbles in the mercury, (2) exploring the possible uses of metallic foams for mitigating cavitation damage and, (3) developing a novel high-intensity acoustic source for test and evaluation purposes.  This effort is funded by the Department of Energy.

  • Faculty: Cleveland, Holt, and Roy
  • Students: C. Ormond (MS)
  • Staff: P. Chitnis (Postdoc), N. Manzi (engineer)