Development of ballon-borne laser scattering micro-particle counting System

研制了一种激光型气溶胶探空仪，安装在观测气球上，测量空气中聚苯乙烯乳胶球（PSL）的粒径为0.1 ~ 5 μ m，并使其能够承受从1013 hPa（地面）到10 hPa （30 ~ 35 km高空）的大气压力变化，对其信噪比、激光功率变化和采样流量变化进行了设计和实验研究。因此，选择了外镜型氦氖激光器。它的结构特点是一个增强的激光管在正常大气压下密封，并有一个控制供电电流的系统。这使得激光功率波动相对于上述大气压力变化仅为0.7%。在环境大气压变化的情况下，选择齿轮泵作为气溶胶吸入泵，使其采样流量比保持恒定，并通过泵电机的转速控制使其保持在0.5%。研制了一种真空专用雾化器，实验确定了气溶胶探空仪在正常大气压下至10 hPa的全范围内的响应曲线。利用脉冲高度分析仪（PHA）直方图的峰值通道和标准差通道对响应曲线和信噪比进行评价。利用该喷雾器，确定了两个通道值在大气压力变化下基本保持恒定，且响应曲线满足Mie散射方程。PHA直方图的相对标准偏差值为42%，信噪比为2.5 ~ 3，可检出0.109个mum PSL。

A laser type aerosol sonde was developed to be mounted on an observation balloon to measure the airborne particle size to 0.1 to 5 mum for polystirene latex spheres (PSL) and enable it to endure atmospheric pressure variation from 1013 hPa (at the ground surface) to 10 hPa (at an altiude of 30 to 35 km), design and experimental investigations regarding the signal-to-noise (S/N) ratio, laser power variation, and sampling flow rate variation were carried out. As a results, an external mirror type He-Ne laser was chosen. Its configuration is characterized by a reinforced laser tube being hermetically sealed at normal atmospheric pressure and having a control system for the supply current. This made the laser power fluctuation a mere 0.7% against the above-stated atmospheric pressure variation. A gear pump was specially chosen as an aerosol suction pump to effect a constant sampling flow rate ratio under the ambient atmospheric pressure variation, and the ratio was hold to 0.5% by speed control of the pumpmotor. A special nebulizer for use in a vacuum was developed to experimentally ascertain the response curve of the aerosol sonde over the full range of normal atmospheric pressure dowm to 10 hPa. The response curve together with the S/N ratio was evaluated by both the peak channel and the standard deviation channel of the pulse height analyzer (PHA) histogram. Using this nebulizer, it was ascertained that both channel values were kept nearly constant against the atmospheric pressure variation and that the response curve well satisfied the Mie scattering equation. It was also demonstrated that 0.109 mum PSL particles could be detected with a relative standard deviation value in a PHA histogram of 42% and an S/N ratio of 2.5-3.