A Noncryogenic Tunable Diode Laser Monitor for On-Road Vehicle EmissionsEPA Contract Number: 68D99030
Title: A Noncryogenic Tunable Diode Laser Monitor for On-Road Vehicle Emissions
Investigators: Nelson, David D.
Small Business: Aerodyne Research Inc.
EPA Contact: Richards, April
Project Period: September 1, 1999 through March 1, 2000
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (1999) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , SBIR - Monitoring , Small Business Innovation Research (SBIR)
Description:Remote sensing of on-road vehicle pollutant emissions has proved to be a powerful technique for learning about real-world automotive and truck emissions. Aerodyne Research has demonstrated a laser spectrometer that remotely senses vehicle emissions by using continuous wave lead salt diode lasers, which are operated at cryogenic temperatures by using a liquid nitrogen dewar. This use of cryogenic lasers significantly increases the construction cost of the instrument as well as its operating cost. An instrument that was free of cryogenic fluids could be significantly more compact and could be deployed more easily and less expensively.
The purpose of this proposal is to demonstrate the feasibility of a portable, compact, noncryogenic, and inexpensive version of the current cryogenic remote sensing instrument based on a novel electro-optical design that will operate the lead salt diode lasers in a pulsed tuning mode at temperatures near room temperature. Aerodyne Research proposes to accomplish this by using the same lead salt diode lasers in a pulsed current mode rather than with continuous operation. These lasers will operate single mode for periods of time approaching a microsecond when held at temperatures much closer to room temperature (200-250 K). Fast infrared detectors and fast data acquisition electronics (100 MHz) will be used to acquire an entire spectrum during a microsecond current pulse and average many such pulses to improve sensitivity. The resulting instrument could approach the sensitivity of the existing instrument at a fraction of the cost.
During Phase I, Aerodyne Research plans to prove that this novel approach to remote sensing is practical and will investigate several crucial technical questions, including: (1) What are typical laser linewidths and timing rates when operated in a pulsed mode? (2) What output powers can be achieved? (3) What is the maximum allowable operating temperature? and (4) What is the maximum allowable repetition rate for pulsing the lasers? The answers to these questions will allow for design and construction of a prototype instrument during Phase II.
Infrared tunable diode laser methodology will be widely implemented in state and federal emissions monitoring programs when the current research type instrument is redesigned into a less expensive, more easily operated commercial version.