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Modification of Laminar Flow Ultrafine Condensation Particle Counters for the Enhanced Detection of 1 nm Condensation Nuclei

机译:改进层流超细凝聚粒子计数器以增强1 nm凝聚核的检测

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摘要

This paper describes simple modifications to thermally diffusive laminar flow ultrafine condensation particle counters (UCPCs) that allow detection of 1 nm condensation nuclei with much higher efficiencies than have been previously reported. These non-destructive modifications were applied to a commercial butanol-based UCPC (TSI 3025A) and to a diethylene glycol-based UCPC (UMN DEG-UCPC). Size and charge dependent detection efficiencies using the modified UCPCs (BNL 3025A and BNL DEG-UCPC) were measured with high resolution mobility classified aerosols composed of NaCl, W, molecular ion standards of tetra-alkyl ammonium bromide, and neutralizer-generated ions. With negatively charged NaCl aerosol, the BNL 3025A and BNL DEG-UCPC achieved detection efficiencies of 37% (90× increase over TSI 3025A) at 1.68 nm mobility diameter (1.39 nm geometric diameter) and 23% (8× increase over UMN DEG-UCPC) at 1.19 nm mobility diameter (0.89 nm geometric diameter), respectively. Operating conditions for both UCPCs were identified that allowed negatively charged NaCl and W particles, but not negative ions of exactly the same mobility size, to be efficiently detected. This serendipitous material dependence, which is not fundamentally understood, suggests that vapor condensation might sometimes allow for the discrimination between air “ions” and charged “particles.” As a detector in a scanning mobility particle spectrometer (SMPS), a UCPC with this strong material dependence would allow for more accurate measurements of sub-2 nm aerosol size distributions due to the reduced interference from neutralizer-generated ions and atmospheric ions, and provide increased sensitivity for the determination of nucleation rates and initial particle growth rates.
机译:本文介绍了对热扩散层流超细冷凝粒子计数器(UCPC)的简单修改,这些计数器允许以比以前报道的更高的效率检测1 nm冷凝核。将这些非破坏性修饰应用于基于丁醇的商业UCPC(TSI 3025A)和基于二甘醇的UCPC(UMN DEG-UCPC)。使用改良的UCPC(BNL 3025A和BNL DEG-UCPC)的尺寸和电荷依赖性检测效率是通过由NaCl,W,四烷基溴化铵的分子离子标准品和中和剂生成的离子组成的高分辨率迁移度分级气溶胶测量的。使用带负电的NaCl气溶胶,BNL 3025A和BNL DEG-UCPC在1.68 nm迁移率直径(1.39 nm几何直径)处实现了37%(比TSI 3025A增加90°)和23%(比UMN DEG-增加8%)的检测效率。 UCPC)的迁移率直径分别为1.19 nm(几何直径为0.89 nm)。确定了两种UCPC的操作条件,这些条件可有效检测带负电的NaCl和W粒子,但不能检测出迁移度完全相同的负离子。这种偶然的物质依赖性,这从根本上尚未得到理解,这表明蒸气凝结有时可能会区分空气“离子”和带电“颗粒”。作为扫描迁移率粒子光谱仪(SMPS)的检测器),由于这种中和剂产生的离子和大气离子的干扰减少,因此具有强材料依赖性的UCPC可以更精确地测量2 nm以下的气溶胶尺寸分布,并提高了确定成核速率和初始颗粒的灵敏度增长率。

著录项

  • 来源
    《Aerosol Science and Technology》 |2012年第3期|p.309-315|共7页
  • 作者单位

    Atmospheric Sciences Division, Brookhaven National Laboratory, Upton, New York, USA Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-18 00:57:40

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