Seamless integrating cavity of monolithic fumed silica
Inventors
Moore, Thomas • Retherford, Kurt D. • Phillips-Lander, Charity
Assignees
Southwest Research Institute SwRI
Publication Number
US-11971347-B2
Publication Date
2024-04-30
Expiration Date
2041-04-30
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Abstract
A seamless fumed silica monolithic integrating cavity device tailored to analyzing a flowed sample. The device is configured to facilitate optical measurements taken from a sample flowed through a cavity of the device. The cavity is defined by a fumed silica monolith with the added feature of a fused quartz lining on the surface of the monolith. This provides an intermediate surface that allows for cleaning and reuse of the highly effective diffuse light scattering fumed silica monolith. The lining may be placed under pressure or vacuum to structurally enhance mechanical integrity of the underlying monolith. Thus, continued or reliably repeated use of the device may be appreciated as well as use in more industrial environments that are prone to vibration. Additionally, while well suited for flow-based sample analysis, a valve of the cavity may be utilized for holding a sample in a temporarily static state for measurement.
Core Innovation
The invention provides a seamless fumed silica monolithic integrating cavity device specifically designed for analyzing a flowed sample using optical measurements. The device is characterized by a cavity defined by a fumed silica monolith with a fused quartz lining on its surface, resulting in a seamless construction that eliminates internal gaps or seams. This configuration helps to prevent light loss associated with seams in conventional integrating cavity devices, thus enhancing measurement accuracy.
The disclosed device addresses the problem that while fumed silica offers superior diffuse reflectivity compared to state-of-the-art materials, its powder form is prone to contamination and degradation and is difficult to maintain in a durable monolithic form. The monolithic construction, combined with a durable, transparent fused quartz liner, enables cleaning and repeated reuse without damaging the underlying fumed silica, making the device suitable for use in both laboratory and industrial environments.
The integrated structure, which may be maintained under air-tight or vacuum-sealed conditions, improves both the mechanical integrity and reflectivity of the fumed silica monolith. The cavity is configured to receive fluid samples through an inlet and outlet and may also include a valve to statically hold samples for measurement. The device enables accurate optical analyses, such as absorption, fluorescence, and Raman spectroscopy, on various sample types including gases, liquids, powders, and granular materials.
Claims Coverage
The patent contains one independent claim that defines the main inventive features of the seamless integrating cavity device.
Seamless integrating cavity device with a monolithic reflective and fused quartz liner
The device comprises: - An outer housing accommodating a light pipe for a light source and an inlet for receiving a sample. - A central cavity defined by a liner of fused quartz that receives light from the light pipe and the sample from the inlet. - A diffusely reflective monolithic reflective material (including fumed silica, magnesium fluoride, or barium sulfate) sandwiched between the outer housing and the liner of fused quartz, in air-tight sealing communication with the fused quartz liner. This inventive feature provides a seamless design, preventing light path losses through seams and supporting accurate optical measurements of flowed or static samples.
The inventive features define a seamless integrating cavity device constructed with a monolithic reflective—specifically fumed silica—enclosed by a fused quartz liner in air-tight communication, achieving improved measurement accuracy and allowing for repeated reuse and practical durability.
Stated Advantages
Enables cleaning and reuse of the integrating cavity device without long-term effects to the structure or reflectivity.
Improves mechanical integrity and durability of the fragile fumed silica monolith, making it suitable for industrial environments.
Reduces or eliminates light path losses due to seams, resulting in more accurate optical measurements.
Allows repeated use and analysis of different samples without undue concern over impurities or contamination.
Provides enhanced reflectivity, with over 99.8% reflectivity in the visible range and over 99.5% from 220 nm to 1300 nm.
Supports flow-based and static sample analysis for increased versatility in measurement setups.
Documented Applications
Optical measurement of samples using integrated cavity absorption spectroscopy (iCAS), integrating cavity ring-down spectroscopy (iCRD), integrating cavity enhanced fluorescence spectroscopy (iCEFS), and integrating cavity enhanced Raman spectroscopy (iCERS).
Flow-based or static analysis of gases, liquids, powders, or granular materials for determining chemical properties, purity, reflectiveness, absorption, scattering, and other optical characteristics.
Use in metrology analyses, including radiance, emission spectral energy, and power measurements.
Application in quality control and optical measurement systems as described for sample items such as reflective coatings or light emitting diodes (LEDs).
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