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

为了利用无人驾驶飞机研究平流层大气痕量气体的分布和变化，有必要研制一种小而轻的空气采样系统。为此，我们开发并测试了一种使用氖气焦耳-汤姆逊（JT）冷却器的新型低温空气采样器。研究结果总结如下：1。实验确定了氖JT冷却器的制冷量。结果表明，在氖气压力为130 kgf/cm^2时，氖JT冷却器的制冷速率约为23焦耳/秒，在50 kgf/cm^2时，制冷速率接近于零。也证实氖气在引入50 ~ 150秒后液化。将低压氮气引入到装有JT冷却器的新型低温空气采样系统中，测量了氮气的采样率。100 hPa氮压下取样速率为0.7 ~ 1.0个正常凋落物/min， 5 hPa氮压下取样速率为0.3 ~ 0.7个正常凋落物/min。这些结果表明，要实现一个实用的采样系统，必须提高采样率。为了检验低温取样系统取样后的空气成分，将一种已测定甲烷浓度的空基标准气体引入取样系统，进行低温取样。结果表明，在测量精度范围内，样品的甲烷浓度与标准气体的甲烷浓度完全一致。采用断管刀、冷焊和N-S连接技术成功开发了高导阀系统。由于阀门系统仅由直管组成，因此即使使用相对较薄的管也容易获得高电导。

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.