Particle Generation and Monitoring, Aerosol Contamination

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Applied Physics, Inc.

Applied Physics, Inc. supports

MSP Corporation Products

Aerosol Generation and Monitoring System

The MSP Corporation, M1500, Aerosol Particle Generation and Monitoring system provides highly accurate, sizing classification system for generation of 10nm to 1,000nm, monodisperse particle aerosols.

APPLICATIONS

  • Laser Particle Counter size calibration
  • Particle behavior studies
  • Laser Particle Counter count calibration
  • Fine particle control research

Major Technologies included with Model 1500 AGM

  • Aerosol Generator with dryer and non-radioactive electrical ionizer
  • Differential mobility analyzer
  • Condensation particle counter
The MSP Model 1500 Aerosol Generation and Monitoring System consists of three main sections: the polydisperse aerosol generator (PAG), the differential mobility analyzer (DMA), and the condensation particle counter (CPC). The DMA and the CPC are separately controlled by a single-board computer, and access is available for the user to take all or part of the aerosol from the outlet of the DMA for any application that requires a highly monodisperse aerosol of known size and concentration.

Technical Description

The polydisperse aerosol generator has a single jet "Collison-type" atomizer for generating fine droplets of about 2um mean diameter. The user places an aqueous solution or suspension in the atomizer reservoir, and as the droplets exit the atomizer, the uniformly sized particles are dried in a Nafion® Membrane Dryer used to evaporate the water; thus forming the final aerosol particles. A typical solution to put in the atomizer is 1% NaCl for generation of NaCl solid particles. One might also use Si, SiO2, Al2O3, TiO2, Si3N4, Ti and W particles. The atomizer is driven by clean, dry, laboratory compressed air connected to the back panel of the Model 1500. Excess polydisperse aerosol, not wanted in the DMA, is exhausted through a filter. The flow rate of the desired aerosol is monitored by the pressure drop across a calibrated laminar flow element. A small impactor removes large agglomerate particles or droplets. Finally, the aerosol particles are neutralized before entering the DMA to best achieve a nearly Boltzmann distribution of charge. This neutralizer uses NO RADIOACTIVE SOURCE, accomplishing the neutralization with bipolar ions generated electrically; thus the Model 1500 can be used anywhere in the world.

The DMA can isolate particles from 10 nm (when operated at 10-L/min sheath flow rate) to as large as 1000 nm (when operated at 3-L/min sheath flow rate). The DMA works in the flow recirculating mode, where the sheath air flow is in a closed loop with a steady flow that is accurately controlled by a feedback control system. A heat exchanger maintains the closed-loop sheath air temperature at near room air temperature. The absolute pressure and temperature of the sheath air flow are also measured and used by the computer control system to improve the accuracy of the particle electrical mobility and diameter calculations.

M1500, particle generator and monitor

Dual Reservoir CPC

The CPC is of the thermal diffusion type, with a saturator maintained at 35°C and a condenser kept at 10°C. The CPC has two fluid reservoirs; the first for holding the working fluid, 1 &em; butanol, and the second reservoir to collect the unwanted condensate fluid. The condensate fluid may contain water when sampling takes place in humid environments. This dual reservoir design leads to a longer life for the working fluid and significantly increases particle count stability over long periods of aerosol analysis.

The Model 1500 Aerosol Generation and Monitoring System is calibrated at MSP Corporation to provide NIST traceable particle size accuracy. Size accuracy of the Model 1500 is provided using the NIST Standard Reference Material, SRM 1691, a 269nm size standard used around the world and produced by the National Institute of Standard and Technology (NIST; Gaithersburg, MD, USA).

condensation particle counter