Abstract: A sensor for passively measuring a maximum temperature within a nuclear reactor comprises a substrate, and a plurality of melt wires within a cavity defined within the substrate, at least one melt wire of the plurality of melt wires exhibiting a variable melting temperature along a length of the at least one melt wire. Related sensors and methods of forming the sensors are also disclosed.

Abstract: A sensor for passively measuring a maximum temperature within a nuclear reactor comprises a substrate, and a plurality of melt wires within a cavity defined within the substrate, at least one melt wire of the plurality of melt wires exhibiting a variable melting temperature along a length of the at least one melt wire. Related sensors and methods of forming the sensors are also disclosed.

Abstract: A method of determining a thermal conductivity and a thermal diffusivity of a material comprises exposing a specimen comprising a substrate of a material and a metallic film over the substrate to an amplitude modulated pump laser beam comprising electromagnetic radiation having a first wavelength and a first modulation frequency to form a pump spot on the metallic film. The specimen is exposed to a probe laser beam comprising electromagnetic radiation having a second wavelength to form a probe spot on the metallic film. A phase shift between the pump laser beam and a reflected probe laser beam is measured while scanning the pump spot relative to the probe spot. A modulation frequency of the pump laser beam is changed to a second modulation frequency and the pump spot is scanned relative to the probe spot while detecting the phase shift. A phase profile of the material is measured and a continuum-based model is fit to the phase profile. Related microscopes and related methods are also disclosed.

Abstract: A method of determining a thermal conductivity and a thermal diffusivity of a material comprises exposing a specimen comprising a substrate of a material and a metallic film over the substrate to an amplitude modulated pump laser beam comprising electromagnetic radiation having a first wavelength and a first modulation frequency to form a pump spot on the metallic film. The specimen is exposed to a probe laser beam comprising electromagnetic radiation having a second wavelength to form a probe spot on the metallic film. A phase shift between the pump laser beam and a reflected probe laser beam is measured while scanning the pump spot relative to the probe spot. A modulation frequency of the pump laser beam is changed to a second modulation frequency and the pump spot is scanned relative to the probe spot while detecting the phase shift. A phase profile of the material is measured and a continuum-based model is fit to the phase profile. Related microscopes and related methods are also disclosed.

Abstract: The invention provides an apparatus for measuring the physical properties of a sample by optically monitoring the response of the sample to illumination by ultrashort optical pulses. The apparatus is a common path optical interferometer of a Sagnac type that can measure physical properties at normal incidence, i.e., a single-arm Sagnac interferometer featuring two beam splitters. Measurement is performed in such a manner that a sample is excited by a beam of ultrashort optical pulses, and variations in intensity and phase of another optical beam are detected. This enables a wide range of measurement of physical properties such as thickness, sound velocity, and thermal properties of substances.

Abstract: The invention provides an apparatus for measuring the physical properties of a sample by optically monitoring the response of the sample to illumination by ultrashort optical pulses. The apparatus is a common path optical interferometer of a Sagnac type that can measure physical properties at normal incidence. The interferometer is a two-arm Sagnac interferometer featuring two beam splitters. Measurement is performed in such a manner that a sample is excited by a beam of ultrashort optical pulses, and variations in intensity and phase of another optical beam are detected. This enables a wide range of measurement of physical properties such as thickness, sound velocity, and thermal properties of substances.

Abstract: An apparatus for measuring the physical properties of a sample by optically monitoring the response of the sample to illumination by ultrashort optical pulses utilizes a common path optical interferometer of a Sagnac type that can measure physical properties at normal incidence. The interferometer is a two-arm Sagnac interferometer featuring three beam splitters. A sample is excited by a beam of ultrashort optical pulses, and variations in intensity and phase of another optical beam are detected. This enables a wide range of measurement of physical properties such as thickness, sound velocity, and thermal properties of substances.