Wavelength-Modulation Absorption Spectroscopy for MHz Thermometry & Species Sensing in Optically Dense Fireballs
Abstract
Fireballs generated by counter-weapons-of-massdestruction (counter-WMDs) laden with biocidal additives (i.e., agent-defeat additives) have demonstrated the potential to mitigate these threats. However, the physical and chemical processes governing the behavior and performance of such fireballs are not well understood. As a result, diagnostic techniques capable of characterizing the physical and chemical processes occurring within fireballs are needed. Specifically, diagnostics capable of measuring the concentrations of evolving chemical species produced from combusting agent-defeat additives, as well as, the gas temperature within the fireball are required. A number of challenges must be overcome to meet this need, including optical-transmission losses approaching factors of 105 to 106 and harsh temperature and pressure fields. Further complicating matters is the need to acquire such measurements on timescales from microseconds to seconds. The primary goal of the proposed work is to meet these diagnostic needs by developing and demonstrating a novel laser -absorption-spectroscopy technique for providing spatially and temporally resolved measurements of gas temperature and molecular-species concentrations in optically dense fireballs. This technique will exploit ultra-high-speed wavelength-modulation, optical amplifiers, and fiber optics to acquire spatially resolved measurements at rates = 1 MHz in fireballs with benign agent simulants (i.e., simulated biological weapons) and opticaltransmission-loss factors = 105. Specifically, this technique will be demonstrated by acquiring measurements of temperature, H2O, and at least one stable halidecombustion-product of agentdefeat additives (e.g., HF, HI, HCl) in fireballs created by detonating a variety of novel explosives. To achieve these goals, fundamental research will be conducted by the PI, one PhD-level graduate student, and one undergraduate student in order to: 1) determine the optimal molecular species and wavelengths for two-color thermometry and molecular-species-concentration sensing in fireballs containing agent simulants and agent-defeat additives, 2) develop new models and characterization methods for ultra-high-speed wavelength-modulation spectroscopy and diode-lasermodulation physics with and without optical amplifiers, and 3) determine the optimal optical arrangement and reconstruction algorithms for providing 2D measurements in transient, optically dense gases
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 10, 2017
- Source ID
- HDTRA11710023
Entities
People
- Christopher Goldenstein
Organizations
- Defense Threat Reduction Agency
- University of Virginia