A ROBUST GAS MONITOR FOR REMOTE ENVIRONMENTS

INFRARED (IR) ABSORPTION SPECTROSCOPY IS A STANDARD LABORATORY TECHNIQUE FOR ANALYZING GAS SAMPLES, BUT GOOD IR ABSORPTION INSTRUMENTS ARE EXPENSIVE, COMPLICATED, AND DELICATE, SHARPLY LIMITING THEIR USEFULNESS FOR REMOTE AND UNATTENDED ATMOSPHERIC MONITORING. THIS PROJECT WILL DEVELOP A RUGGED, SELF-CALIBRATING IR ABSORPTION SENSOR THAT HAS MANY OF THE DESIRED CHARACTERISTICS. WITH NO MOVING PARTS, THIS DEVICE CAN MEASURE CONCENTRATIONS OF MANY GASES BY MEASURING SPECTRA APPROACHING THE QUALITY OF LABORATORY IR ABSORPTION INSTRUMENTS, AT A COST COMPARABLE TO SIMPLE CATALYTIC SENSORS. IN ITS ORDINARY OPERATING MODE, THIS MULTISPECTRAL SENSOR OPERATES AT HIGH PULSE RATES AND PROVIDES ACCURATE CHEMICAL INFORMATION ON A FEW MILLISECOND TIME-SCALE FOR IMMEDIATE USE IN AN ACTIVE FEEDBACK CONTROL SYSTEM. A UNIQUE FEATURE OF THIS DEVICE S THAT IT IS SELF-REFERENCING; THIS SHOULD PROVIDE EXCELLENT STABILITY AND ALLOW FOR LONG COUNTING TIMES WITH PHASE-LOCKED DETECTION AND A CONSEQUENT IMPROVEMENT IN SENSITIVITY. THE PHASE I PROJECT WILL EVALUATE THE SENSITIVITY OF A MULTISPECTRAL SENSOR USING PHASE-LOCKED DETECTION AND SELF-REFERENCING FOR STABILITY. IN ADDITION, THE PHASE I PROJECT WILL EXPLORE PHOTOACOUSTIC DETECTION AND EXTENDED SAMPLING WITH UNCLAD OPTICAL FIBERS IN ORDER TO EXTEND THE DETECTION LIMITS. THESE TESTS WILL ESTABLISH THE BASIC DESIGN AND PERFORMANCE CHARACTERISTICS OF A PROTOTYPE INSTRUMENT TO BE BUILT AND DEMONSTRATED PHASE II.