Aerosol Properties & Processes: Instruments

PALMS Instrumentation

The PALMS instrument is a laser ionization mass spectrometer which makes in-situ measurements of the chemical composition of individual aerosol particles. Aerosols are brought into a vacuum system and individual particles are detected by light scattered as they cross the beam of a continuous laser. The scattered light signal gives a rough indication of the size of the particle and a provides a trigger for an excimer laser (193nm), which is pulsed so its beam hits the particle to desorb and ionize molecules and atoms. These ions are analyzed with a time of flight mass spectrometer to provide a complete mass spectrum from each particle. The instrument is capable of measuring particles from 0.2 to 3 microns in diameter. Analysis is complete less then 1 millisecond after the aerosols enter the inlet. Furthermore, artifacts are minimized because particles never touch a surface. The instrument can acquire either positive or negative ion spectra.

There are two versions of the instrument. A laboratory version has made measurements at Idaho Hill, Colorado, Cape Grim, Tasmania, and Atlanta, Georgia. A flight version has flown in the nose of the NASA WB-57F high-altitude research aircraft, which is operated by NASA Johnson Space Center based at Ellington Field in Houston, Texas.

PALMS probe
Probe on the nose of the WB-57 aircraft is the inlet for the PALMS instrument.
PALMS schematic
Schematic of the PALMS instrument.
periodic table
The periodic table of elements observed in aerosol particles by the PALMS instrument at altitudes above 5 km.