Innovation and Partnerships Office

Eigenfrequency Thermometry (EFT) 2016-124

APPLICATIONS OF TECHNOLOGY:

  • Detection of localized hot spots and temperature change monitoring in cryogenic systems and in chemical and nuclear reactors
  • Integrated thermal monitoring in manufacturing plants
  • Monitoring moving parts in machinery
  • Medical monitoring
  • Thermal monitoring and management for micro- and nano-scaled objects

ADVANTAGES:

  • Sensitive and noninvasive monitoring of temperature variation
  • Eliminates delayed response
  • Ability to detect local hot spots within an object

ABSTRACT:

Berkeley Lab researcher Maxim Marchevsky has developed a technology for detecting and monitoring temperature changes of a solid body by means of monitoring of its natural resonances (eigenfrequencies). By enabling a solid body to act as a bulk thermometer, sensitive and noninvasive temperature monitoring can be achieved for objects constrained by environment, dimensions, etc. from measurement with temperature sensing instruments. Measurement error and delayed response associated with conventional solid-state sensor thermometers can be readily eliminated.

In the Berkeley Lab technology, a short (typically 0.1 – 5 µs) mechanical pulse is applied to a body under test by a piezoelectric or electromagnetic (EMAT) transducer, pulsed laser beam using photo-acoustic mechanism, or other means. A receiver records the vibrational response, enabling analysis to identify temperature variations.

Natural resonances of any mechanical system correspond to its various vibrational degrees of freedom (compression, twist, tilt, etc.) that are uniquely defined by the body geometry, mass and stiffness (Young’s modulus). The Berkeley Lab technology relies upon a high (~100-500) mechanical quality factor of typical solids, allowing the small temperature-related phase shift to accumulate over many (200-1,000) oscillation periods following the initial pulsed excitation. This approach improves measurement sensitivity by the same (200-1,000) factor, thus making temperature-related Young’s modulus variations of the order of 0.1-1 ppm readily detectable. Processing of the vibrational response signal minimizes or fully eliminate effects of ambient electromagnetic and mechanical noise to the thermal measurement.

FOR MORE INFORMATION:
Marchevsky, M., and Gourlay, S. “Acoustic thermometry for detecting quenches in superconducting coils and conductor stacks,” Applied Physics Letters 110, 012601, 2017.

DEVELOPMENT STAGE: Proven principle

STATUS: Patent pending. Available for licensing or collaborative research.

SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:   

Epitaxial Germanium Temperature Sensor, IB-1561A

Thermal Profiling of Nanoscale Circuitry, IB-2363

Nanotubes as Robust Thermal Conductors, IB-2335