PALMS-NG: A Unique Dual S-Shaped Time-of-Flight Mass Spectrometer for Atmospheric Measurements
JUSTIN JACQUOT, Xiaoli Shen, Maya Abou-Ghanem, Karl Froyd, Michael Lawler, Gregory Schill, Kyra Slovacek, David Thomson, Daniel Murphy, Daniel Cziczo,
Purdue University Abstract Number: 723
Working Group: Instrumentation and Methods
AbstractThe newly developed Particle Analysis by Laser Mass Spectrometry – Next Generation instrument (PALMS-NG) has now performed real-time single particle measurements onboard three research aircraft. It is designed to primarily operate on stratospheric airplanes (NASA ER-2 and WB-57F) with limited payload capacity and large variability in pressure (sea level to 50 mbar) and temperature (-70 to +50 °C). In 2023, PALMS-NG has been adapted to fly onboard the NASA DC-8 aircraft for tropospheric aerosol measurements.
PALMS-NG represents an evolution of the existing laboratory and aircraft PALMS instruments. New features have been implemented, which include a new aerodynamic inlet, revised optics, a pair of unique s-shaped time-of-flight mass spectrometers (sTOF-MSs) for bipolar ion detection and full control of the instrument from the ground when in flight. Two continuous wave (CW) 405 nm lasers are used for particle detection and geometric and aerodynamic size estimation. One of the CW lasers triggers a 193 nm UV light pulse from an excimer laser that ablates and ionizes the particle. The new design of the aerodynamic inlet combined with new optics allow PALMS-NG to measure particles from 0.1 to 4 µm. The novel sTOF-MS geometry makes it possible to fit two mass spectrometers in a volume that previously allowed only a single reflectron, thus enabling acquisition of bipolar spectra for each detected particle. In addition, the longer ion path length and electrostatic sectors that ions traverse before reaching the detector result in a higher ion transmission efficiency (~100%) and higher mass resolution (~1000). Despite the modernized and upgraded hardware of PALMS-NG, all data acquired remain fully comparable with the 30-year data record obtained from the original PALMS instrument.