ULTRAFINE CONDENSATION NUCLEUS COUNTER FOR STRATOSPHERIC PRESSURES

THE CONCENTRATIONS OF AIRBORNE PARTICLES IN THE UPPER ATMOSPHERE AND STRATOSPHERE ARE MEASURED BY LOW-PRESSURE CONDENSATION NUCLEUS COUNTERS WHEREIN PARTICLES ARE GROWN INSIZE BY CONDENSATION FROM A SUPERSATURATED VAPOR AND COUNTEDOPTICALLY. CURRENT INSTRUMENTS ARE LIMITED BY THE SMALLEST PARTICLE SIZE WHICH THEY CAN DETECT (0.02MUM). LOWER OPERATING PRESSURES AND SMALLER DETECTABLE PARTICLE SIZES ARE NEEDED TO STUDY NEW PARTICLE FORMATION PROCESSES, AND TOCHARACTERIZE EMISSIONS FROM HIGH-ALTITUDE AIRCRAFT. THE OBJECTIVE OF THIS WORK IS TO DESIGN A CONDENSATION NUCLEUS COUNTER CAPABLE OF COUNTING PARTICLES AS SMALL AS 0.003 MUM AT PRESSURES RANGING FROM 10 TO 1000 MBAR. THE HEAT AND MASS TRANSFER PROCESSES IN THE CONDENSATION NUCLEUSCOUNTER WILL BE MODELED NUMERICALLY. CONDENSATIONAL DROPLETGROWTH WITH HEAT DISSIPATION WILL BE MODELED ANALYTICALLY. THE MODEL WILL BE VERIFIED TO THE EXTENT POSSIBLE BY COMPARISON WITH EXISTING MODELS AND DATA FROM A CONDENSATIONNUCLEUS COUNTER WHICH HAS BEEN USED FOR STRATOSPHERIC PARTICLE MEASUREMENTS. MODEL RESULTS WILL BE USED TO DESIGNAN IMPROVED CONDENSATION NUCLEUS COUNTER. PARAMETERS TO BE OPTIMIZED INCLUDE FLOW RATES, WORKING FLUID, CONDENSER AND SATURATOR TEMPERATURES AND CONDENSER LENGTH.