The 1-by-3 Tandem Differential Mobility Analyzer for Measurement of the Irreversibility of the Hygroscopic Growth Factor

A new instrument, namely the 1 × 3 tandem differential mobility analyzer (1 × 3-TDMA), has been developed. Its primary measurement is the irreversibility of the hygroscopic growth factor of aerosol particles. The instrument uses the hysteresis of phase transitions to infer the solid or aqueous state of the particles. A first DMA passes particles of a selected electric mobility at relative humidity RH0. Exiting this DMA, the particles are split into three separate flows. The first flow is exposed to RH 0  → (RH 0 +  δ ) → RH 0 in a deliquescence test before passing through a second DMA that is set to the same electric mobility as the first DMA. The second flow passes directly to a third DMA without change in RH, thereby serving as a reference arm. This DMA is also set to the same electric mobility as the first DMA. The transmission ratio of the 1 × 3-TDMA is defined as the particle concentration passing the deliquescence test divided by that passing through the reference arm. The transmission ratio is unit...