Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a common method for gas analysis that is fast, highly selective, reliable and accurate. The analytical method works by exciting certain gas species in the sample chamber with the tunable laser source, which induces characteristic vibrations and rotations at specific wavelengths. The spectral output is a distinct chemical fingerprint in which the concentration of the active gas molecules can be quantified. Most of these analyzers are either large benchtop instruments or smaller systems with reduced sensitivity.
There exists a need for a sensitive, miniature spectrometer that can detect multiple gases in small, inaccessible spaces, or under challenging conditions for either direct reading or continuous monitoring applications.
LLNL researchers have developed a TDLAS-based, standalone, real-time gas analyzer in a small form-factor for continuous or single-point monitoring. The system can analyze multiple gases with ultra-high sensitivity (ppm detection levels) in harsh conditions when utilizing wavelength-modulation spectroscopy (WMS).
The key physical component of the system is the multi-pass gas minicell. The novel approach is the mirror configuration within the cell that is low signal loss, allowing for higher sensitivity compared to traditional mirror design of gas cells (e.g., white, Herriott). The other components of the monitoring system include:
- commercially available tunable semiconductor laser (e.g., edge emitting lasers, vertical cavity surface emitting lasers to provide various absorption lines of one gas or capture multiple gas species at once)
- commercially available photodetector(s) to receive the signal
- fiber-coupling to laser and detector components
- integration onto printed circuit board (PCB) and controlled by Field Programmable Gate Array (FPGA)
This integrated, standalone system allows for remote detection of a variety of gases down to ppm (and potentially to ppb) in harsh conditions and enabling multiplexing of different sources for the analysis of gas mixtures.
- Robust and rugged system amenable to harsh environment (resistant to extreme vibration, humidity, temperature, EMI)
- PCB integration with FPGA control and wireless-compatible, allowing operation of the system without computer connection
- Complete packaged system for real-time monitoring/persistent remote surveillance
- Small footprint for handheld analyzers or field deployment applications
- Low operating cost and maintenance
- Long service time
- Low power consumption (few mW)
- Miniaturized gas cell supports multiplexed and multipoint detection of gas mixtures
- Ultra-high sensitivity
- Embedded, portable, or UAV remote detection and monitoring of gases, including isotopic compositions
- Environmental and pollution monitoring (e.g. air quality, hazardous or polluting gas production from industrial processes such as semiconductor fabrication, VOCs)
- Evapotranspiration and drought monitoring for agronomic applications (e.g., crop surveillance)
- Early detection of problems such as component deterioration, corrosion, failures or leaks of closed systems
- Forensic analysis in either chemical global threats (e.g. nerve agents) or homeland security (e.g. by-products of explosives or radiological exposure)
- Agronomic/rural developments (e.g. crop surveillance) and ecosystems by monitoring greenhouse gases
Current stage of technology development: TRL 4
LLNL has patent(s) on this invention.
US Patent No. 9234794 Fiber optic coupled multipass gas minicell, design assembly thereof published 1/12/2016
US Patent No. 10184883 Detecting isotopologues of carbon dioxide in the atmosphere in concomitance of water or methane published 1/22/2019
US Patent Application No. 2022/0342225 SAMPLE CELL FOR OPTICAL ANALYSIS published 10/27/2022