Gas analysis system for continuous, accurate  and simultaneous measurement of concentrations and
fluxes of multiple atmospheric trace gases

 

The Dual Quantum Cascade Laser Trace Gas Detector MODEL QCL-76-D, is based on the extensive experience at Aerodyne Research, Inc. of providing high precision trace species measurement instruments to researchers in the atmospheric measurements community. 

 APPLICATIONS:

• Infrared absorption measurement of multiple trace gases such as: CH₄, N₂O, CH₂O, CO₂, NO, NO₂, C₂H₆, NH₃, O₃, SO₂, H₂O₂, and HNO₃.

• Atmospheric research requiring a high fidelity instrument flexible and rugged enough to operate in field experiments.

• Measurement of sources of radiatively important trace species (RITS); aerosol precursors; acid gas deposition rates; air pollution characterization.

• Remote sensing of emissions over swamps or bogs not readily accessible from conventional ground based platforms.

• Remote monitoring of gas phase pollutants over highways, landfills, and hazardous waste disposal sites.

• Fence-line monitoring around industrial sites.

• Airborne and/or van-mounted measurements for wide area surveys.

ADVANTAGES:

• Compact instrument package with all optics and electronics mounted in standard 19” rack.

• Thermoelectrically cooled QC lasers operate at near-room temperature without cryogenic cooling.

• Two QC lasers allow simultaneous multiple trace species detection in single sample cell.

• High sensitivity, fast time response measurements

  • 76-meter pathlength, 0.5 liter volume multiple pass absorption cell for atmospheric sampling at a pressure of 30-60 Torr.

  • Combined with 500 liter/minute vacuum pump provides a time response (1/e) of less than 0.1 second.   

•  Choice of TE cooled detectors or liquid nitrogen (LN2) cooled detectors.

  • Thermoelectric detectors—eliminate the need for liquid nitrogen entirely. 

    • New long-wavelength TE detectors now make a fully non-cryogenic system possible at long wavelengths.  Excellent detection of ammonia at 10.4 micron has been demonstration (0.2 ppbv NH₃ in 1 sec in a fully non-cryogenic system)  

  • LN2 detectors—can extend the precision especially at longer wavelengths for methane and ammonia detection.  

• New electronics design has common elements with the compact QCL system:

  • Lightweight power supplies

  • Integrated electronic chassis

  • New high precision control elements 

• Excellent mode stability and reproducibility. 

  • Allows “turn-key” operation.  

• Data acquisition rate: 1 Hz to 20 Hz.

• An automatic background subtraction routine, calibration cycles, and permeation tube additions are fully automated.

• Option of continuous wave (cw) room temperature QC lasers for extremely narrow laser linewidth, improved selectivity and greater laser power.

PHYSICAL DIMENSIONS:

width 24", depth 28", height 26"
weight   160 lbs
electrical power 350 Watts, 120/240 V, 50/60 Hz (not including vacuum pump)

Optical layout of QC-76-D:  Dual QCL instrument with LN2-cooled detectors.

Important molecular species which can be monitored with QC lasers. 

For each species the optimal wavelength (cm^-1), the detection precision (ppb in 1 sec) and the detection limit (2 sigma in 100 sec) are given.  Values in black are actual values obtained at ARI with an optical path length of 76 meters.  Values in red are projections.