The Ps-aerogel system [Ps is positronium (an electron-positron-hydrogen-like atom)] has been evaluated and optimized as a potential tool for planetary exploration missions. Different configurations of use were assessed, and the results provide a quantitative measure of the expected performance. The aerogel density is first optimized to attain maximum production of Ps that reaches the pores of the aerogel. This has been accomplished, and the optimum aerogel density is ≈70 mg/cm3. The aerogel is used as a concentrator for target volatile moieties, which accumulate in its open porosity over an extended period of time. For the detection of the accumulated materials, the use of Ps as a probe for the environment at the pore surface, has been proposed.
This concept is based on two steps: (1) using aerogel to produce Ps and (2) using the propensity of Ps to interact differently with organic and inorganic matter. The active area of such a detector will comprise aerogel with a certain density, specific surface area, and gas permeability optimized for Ps production and gas diffusion and adsorption. The aerogel is a natural absorber of organic molecules, which adhere to its internal surface, where their presence is detected by the Ps probe. Initial estimates indicate that, e.g., trace organic molecules in the Martian atmosphere, can be detected at the ppm level, which rivals current methods having significantly higher complexity, volume, mass, and power consumption (e.g. Raman, IR).
This method carries important benefits in working toward NASA/JPL goals, and has the potential to advance organic detection capabilities. It is intended to work toward feasibility studies. At the same time, it is recognized that a full-scale investigation will profit enormously from an achieved optimization of the aerogel microstructure for Ps production and gas percolation.
The Ps-aerogel system provides an entirely new approach toward sensing of trace volatile components in vacuum or in the atmosphere. Contrary to all other conventional methods, which use “momentary sensing” and analyzing the content, the Ps-aerogel system relies on a continuous passive exposure to the environment. An instrument built on this new technology will be lightweight, small in size, and will not consume power during accumulation. In testing, the adsorption of simple organic materials, such as alcohols, naphthalene, etc, has been detected. Also, with the optimization of the Ps-aerogel system, a number of other applications, ranging from thermal insulation to charge storage systems, have been discovered.
This work was done by Mihail P. Petkov and Steven M. Jones of Caltech for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Physical Sciences category. NPO-46762
This Brief includes a Technical Support Package (TSP).
Aerogel-Positronium Technology for the Detection of Small Quantities of Organic and/or Toxic Materia
(reference NPO-46762) is currently available for download from the TSP library.
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Overview
The document discusses a novel technology developed by NASA's Jet Propulsion Laboratory (JPL) that utilizes aerogel and positronium for the detection of small quantities of organic and toxic materials. This technology leverages positron annihilation lifetime spectroscopy (PALS), a technique sensitive to voids, to measure positron lifetime distributions in aerogels. When positrons interact with electrons, they form positronium (Ps), which can exist in two states: ortho-Ps (o-Ps) and para-Ps (p-Ps). The o-Ps state has a significantly longer lifetime, making it useful for detecting materials within the pores of aerogels.
The research highlights the importance of aerogel's unique properties, such as its high surface area (~100 m²/cm³) and large pore sizes, which facilitate molecular diffusion and absorption of organic compounds. The PALS measurements are conducted in a vacuum to eliminate interference from air molecules, allowing for accurate detection of the o-Ps lifetime, which is influenced by the pore size and the presence of absorbed materials.
Key findings indicate that the production of positronium increases with aerogel density, with optimal densities around 70 mg/cm³ for fast absorption measurements. The study also notes that certain organic materials can suppress the o-Ps signal, providing a means to identify absorbed substances based on changes in the o-Ps lifetime. The document presents qualitative attempts to understand the feasibility of using Ps-aerogel as a detector for organic molecules, with experiments involving known materials like ethanol and urea, as well as contaminated aerogel samples.
Future plans for this research include quantitative measurements with controlled absorption rates, exploring modified detection schemes, and enhancing the aerogel's properties for better performance. The document emphasizes the potential of this technology for in situ detection of trace organics, which could have significant applications in environmental monitoring, safety, and space exploration.
Overall, the research represents a promising advancement in the field of material detection, combining the unique characteristics of aerogels with the sensitivity of positronium interactions to create a powerful tool for identifying small quantities of organic and toxic materials.
