一种自制软X射线颗粒中和器与同类商业化中和器的性能比较

Performance Comparison Between a Custom-Made Soft X-Ray Neutralizer and a Commercial Counterpart

运用扫描电迁移率粒径谱仪对比测试自制软X射线中和器(CM-SXR)与商业化TSI高级气溶胶中和器(TSI-SXR)。研究结果表明,对于20 nm以上颗粒物,在差分电迁移率分析仪(SMPS)筛分负电荷模式下,对不同颗粒物(聚苯乙烯乳胶颗粒、硫酸铵及氯化钠颗粒、室内空气颗粒)的测试均显示,使用自制中和器比使用TSI中和器测量所得的颗粒物数浓度要高,浓度差异最大达40%;而在筛分正电荷模式下,其结果正好相反,最大浓度差达77%。造成上述差异的原因可能是由于软X射线在两种中和器中放置位置不同而导致放射程度不同以及停留时间存在差异,从而最终导致中和器中颗粒物正负电荷分布不同。

Performance comparison between a custom-made soft X-ray neutralizer(CM-SXR) and a commercial counterpart(TSI-SXR, advanced aerosol neutralizer, model 3088, TSI, USA) is made by using a scanning mobility particle sizer(SMPS). The results show that for all the tested particles(i.e., Polystyrene latex particles, ammonium sulfate particles, sodium chloride particles, and room air particles) with a size greater than 20 nm, the particle number concentration measured by CM-SXR is higher than that measured by TSI-SXR when the differential mobility analyzer(DMA) is operated under the negatively-charged particle mode, and the differences can be up to 40%. However, opposite results have been found when the DMA is operated at the positively-charged mode, that is the particle number concentration measured by TSI-SXR is higher than that measured by CM-SXR and the differences are up to 77%. Possible reasons accounting for the above differences are discussed, and it is deduced that the mounting position of the soft X-ray in the two neutralizers, which results in different exposures of the X-ray and the differences of the residence time when the sample passes the two different neutralizers, is likely the main reason leading to different positively-and negatively-charged particle distribution inside the neutralizers.