Open AccessMass spectrometer calibration of Cosmic Dust Analyzer
Author(s) -
Ahrens Thomas J.,
Gupta Satish C.,
Jyoti G.,
Beauchamp J. L.
Publication year - 2003
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002je001912
Subject(s) - microchannel plate detector , ion , mass spectrometry , laser , materials science , reflectron , analytical chemistry (journal) , physics , time of flight , spectrometer , optics , detector , time of flight mass spectrometry , ionization , chemistry , chromatography , quantum mechanics
The time‐of‐flight (TOF) mass spectrometer (MS) of the Cosmic Dust Analyzer (CDA) instrument aboard the Cassini spacecraft is expected to be placed in orbit about Saturn to sample submicrometer‐diameter ring particles and impact ejecta from Saturn's satellites. The CDA measures a mass spectrum of each particle that impacts the chemical analyzer sector of the instrument. Particles impact a Rh target plate at velocities of 1‐100 km/s and produce some 10 −8 to 10 −5 times the particle mass of positive valence, single‐charged ions. These are analyzed via a TOF MS. Initial tests employed a pulsed N 2 laser acting on samples of kamacite, pyrrhotite, serpentine, olivine, and Murchison meteorite induced bursts of ions which were detected with a microchannel plate and a charge sensitive amplifier (CSA). Pulses from the N 2 laser (10 11 W/cm 2 ) are assumed to simulate particle impact. Using aluminum alloy as a test sample, each pulse produces a charge of ∼4.6 pC (mostly Al +1 ), whereas irradiation of a stainless steel target produces a ∼2.8 pC (Fe +1 ) charge. Thus the present system yields ∼10 −5 % of the laser energy in resulting ions. A CSA signal indicates that at the position of the microchannel plate, the ion detector geometry is such that some 5% of the laser‐induced ions are collected in the CDA geometry. Employing a multichannel plate detector in this MS yields for Al‐Mg‐Cu alloy and kamacite targets well‐defined peaks at 24 (Mg +1 ), 27(Al +1 ), and 64 (Cu +1 ) and 56 (Fe +1 ), 58 (Ni +1 ), and 60 (Ni +1 ) dalton, respectively.