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

为了利用无人机了解大气中痕量气体在平流层中的分布和变化，有必要开发一种小而轻的空气采样系统。为此，我们研制并测试了一种使用霓虹焦耳-汤姆逊(JT)制冷器的新型低温空气采样器。主要研究结果如下：1.对霓虹灯JT制冷机的制冷量进行了实验测定。结果表明，在Ne气压为130kgf/cm2时，Ne JT制冷器的制冷量约为23焦耳/秒，而在50kgF/cm2时，制冷量几乎为零。此外，还证实了在Ne气体引入50~150秒后，Ne气体发生了液化。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。在氮气压力为100百帕时，采样速率为0.7~1.0标准凋落物/分钟；在5百帕时，采样速率为0.3~0.7标准凋落物/分钟。这些结果表明，要实现实用的采样系统，有必要提高采样率。为了检测经低温采样系统采样后的空气成分，将已确定甲烷浓度的气基标准气体引入采样系统进行低温采样。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浓度一致。采用断管切割器、冷焊和N-S接头技术，研制成功了一种高电导阀门系统。由于阀门系统只由直管组成，即使使用较薄的管也很容易获得高电导。

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.