Development of a cryogenic air sampling system for unmanned aircraft observation.

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In order to clarify distributions and variations of atmospheric trace gases in the stratosphere using an unmanned aircraft, it is necessary to develop a small and light weight air sampling system. For this purpose, we developed and tested a new cryogenic air sampler using neon Joule-Thomson (JT) cooler. The results are summarized as follows :1. An refrigeration capacity of neon JT cooler was experimentally determined. The results showed that the neon JT cooler produced refrigeration of about 23 Joule/second at neon gas pressure of 130 kgf/cm^2 and of nearly zero at 50 kgf/cm^2. It was also confirmed that the neon gas was liquefied after 50 to 150 seconds of the neon gas introduction.2. Low pressure nitrogen was introduced into a new cryogenic air sampling system in which the JT cooler was equipped, and sampling rate of nitrogen were measured. the sampling rate was between 0.7 and 1.0 normal litter/minutes at nitrogen pressure of 100 hPa and between 0.3 and 0.7 normal litter/minutes at 5 hPa. these results indicate that it is necessary to increase the sampling rate to realize a practical sampling system.3. To examine the composition of air after sampled by the cryogenic sampling system, an air-base standard gas, of which methan concentration was already determined, were introduced into the sampling system and sampled cryogenically. As a result, the methan concentration of the sample was confirmed to be identical to that of the standard gas within the measurement precision.4. A high conductance valve system was successfully developed using a pipe breaking cutter, cold weld and N-S joint techniques. Because the valve system was composed only by straight tubes, high conductance was easily attained even if relatively thin tube was used.