# Highly Sensitive CH4/C2H2 Dual-Component TDLAS Sensor Based on a Dual-Channel Hexagram Multi-Pass Cell

## TL;DR

This paper introduces a new laser sensor that can detect methane and acetylene with high sensitivity and accuracy.

## Contribution

The novel dual-channel hexagram multi-pass cell design enables real-time detection of both CH4 and C2H2 with improved sensitivity.

## Key findings

- The sensor achieved a methane detection limit of 132.08 ppb and 77.32 ppb with extended averaging.
- Acetylene detection limits were 20.19 ppb and reduced to 3.50 ppb with longer averaging times.
- The design allows for simultaneous and synchronous detection of both gases with linear response.

## Abstract

A tunable diode laser absorption spectroscopy (TDLAS) sensor with a highly sensitive dual-component for methane (CH4) and acetylene (C2H2) detection is reported in this paper for the first time. A multi-pass cell (MPC) design model was established employing a vector-based ray-tracing method. A dual-channel MPC with an interlaced dual hexagonal star pattern was designed to improve gas absorption and realize real-time synchronous detection of CH4 and C2H2. During the simultaneous continuous monitoring of CH4 and C2H2, the sensor exhibited an excellent linear response to concentration variations. The minimum detection limit (MDL) for CH4 reached 132.08 ppb, improving to 77.32 ppb when the average time was increased to 300 s. In the case of C2H2, the MDL was measured at 20.19 ppb and further reduced to 3.50 ppb under the same extended average time.