High-Sensitivity TDLAS Sensors Based on Double-Helix United/Split Spot Patterns
Haiyue Sun, Xiaorong Sun, Ying He, Shunda Qiao, Yufei Ma
Abstract
This paper presents a highly sensitive tunable diode laser absorption spectroscopy (TDLAS) sensor based on a double-helix united/split spot pattern. A dense double-helix united spot pattern was designed based on a three-mirror multipass cell (MPC) to obtain high detection sensitivity in a compact structure. The corresponding minimum detection limit (MDL) for methane (CH 4 ) detection was enhanced to be 122.9 ppb. When the integration time was extended to 200 s, the MDL was reduced to 15.4 ppb. An example of a CH 4 measurement application in urban environmental monitoring was presented in this research. A double-helix split spot pattern was designed to realize a real-time simultaneous dual-component TDLAS sensor. In the simultaneous and continuous monitoring of CH 4 and acetylene (C 2 H 2 ), a highly sensitive linear relationship with the concentration was successfully obtained. Corresponding MDLs for the CH 4 /C 2 H 2 detection were calculated to be 354.7 and 111.2 ppb, respectively. When the integration time was set to 100 s, the corresponding MDLs were enhanced to 35.7 and 19.5 ppb, respectively.