Integrating cavity of monolithic fumed silica
Inventors
Moore, Thomas • Retherford, Kurt D. • Phillips-Lander, Charity
Assignees
Southwest Research Institute SwRI
Publication Number
US-11761883-B2
Publication Date
2023-09-19
Expiration Date
2041-04-30
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Abstract
A fumed silica monolithic integrating cavity device. The device is configured to facilitate optical measurements taken from a sample positioned within 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. Furthermore, 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.
Core Innovation
The invention concerns an integrating cavity device constructed from a monolithic fumed silica, which is used to define an internal cavity where a sample can be positioned for optical measurement. The device incorporates a substantially transparent fused quartz lining on the surface of the fumed silica monolith. This transparent liner allows for the cleaning and reuse of the integrating cavity, addressing the major issue of contaminant buildup that limits the usability of fumed silica as an optical reflective material.
A key problem addressed by the invention is the rapid degradation and contamination of integrating cavities that use fumed silica as a diffuse reflector, due to the high surface area and absorbent properties of the material. Fumed silica attracts contaminants such as dust, moisture, and pollen, and cleaning with solvents is impractical, making repeated reliable use challenging. The invention overcomes this by providing an air-tight, cleanable fused quartz liner, which maintains the reflective performance of the monolith and increases its mechanical durability.
Additionally, the transparent liner may be used to create a vacuum or pressurized seal around the monolithic fumed silica, further enhancing the structural integrity of the device. This enables the integrating cavity to be used safely and repeatedly even in industrial environments subject to vibration or contamination, while retaining high reflectivity and facilitating the accurate optical measurement of sample items placed within the cavity.
Claims Coverage
There are three independent claims that define the main inventive features of the invention.
Integrating cavity device with monolithic fumed silica and fused quartz liner
An integrating cavity device comprising: - An outer housing to attain light from an external source; - A diffusely reflective monolithic fumed silica accommodated by the outer housing with a surface defining a cavity for receiving the light; - A substantially transparent liner of fused quartz on the surface of the fumed silica defining the cavity, the liner being in air-tight sealing communication with the fumed silica.
Measurement system with integrating cavity device and optical components
A measurement system for ascertaining optical characteristics of a sample item, comprising: - An integrating cavity device with a cavity defined by a light scattering monolith (comprised of fumed silica, barium sulfate, or magnesium fluoride), having a substantially transparent liner of fused quartz thereover for accommodating the sample; - A light source to supply light to the cavity for scattering; - A spectral detector to acquire scattered light readings from the cavity for sample analysis.
Method for acquiring optical characteristics using fumed silica integrating cavity device
A method comprising the following steps: 1. Projecting a light toward an integrating cavity device from an external source; 2. Routing the light into a cavity of the device defined by a fumed silica monolith; 3. Utilizing the fumed silica monolith to diffusely scatter the light across a transparent liner positioned over the monolith and accommodating the sample item; 4. Acquiring the scattered light from the cavity; 5. Analyzing the acquired light to ascertain the optical characteristics of the sample item.
The inventive features cover a device architecture of a monolithic fumed silica integrating cavity with a fused quartz liner, a measurement system using such a device with relevant optical components, and a method of acquiring optical characteristics using these elements.
Stated Advantages
The integrating cavity device may be cleaned using common solvents and cleansers without long-term effects on performance due to the transparent liner.
The device can be utilized repeatedly over time, enabling reliable repeated use and measurements of multiple samples.
Mechanical reinforcement provided by the air-tight liner, especially when under vacuum, increases the durability and environmental isolation of the fumed silica monolith.
The integrating cavity is suitable for use in harsher environments or during transport without undue concern over damage.
The use of monolithic fumed silica enables very high diffuse reflectivity, exceeding 99.8% in the visible spectral range and extending high reflectivity to wider spectral regions.
Documented Applications
Optical measurement of sample items using integrating cavity absorption spectroscopy (iCAS), integrating cavity ring-down spectroscopy (iCRD), integrating cavity enhanced fluorescence spectroscopy (iCEFS), and integrating cavity enhanced Raman spectroscopy (iCERS), as well as optical photometry and metrology.
Optical characterization of samples such as bulk powder amino acids for evaluation of characteristics, purity, or identity.
Performing radiance, emission spectral energy, and power measurements within the integrating cavity device.
Use of the integrating cavity device in industrial environments prone to vibration and contamination, and transport by land, sea, air, or rocket.
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