An Appreciation of the Scientific Researches of Dr Peter H. Dawson

Upon the death of Peter H. Dawson in 2015, mass spectrometry lost a major figure. Within the area of radiofrequency quadrupole electric fields applied to mass spectrometry, Dawson stands alongside its pioneers Wolfgang Paul, Nobelist and inventor of the technology, and Wilson Brubaker, who identified and overcame the deleterious effects of fringing electric fields on quadrupole mass filter performance. Seventy‐one of Dawson's 97 scientific publications are concerned with quadrupole mass analyzers, ion traps and monopole mass spectrometers. Of especial note are his book and review articles in which he disseminated information on the theoretical fundamentals and practicalities of these systems to a wider audience, thereby having a major impact on the development of this important field of endeavour. The scientific researches of Dr Dawson and his advice and counsel, influenced to a major degree, and to the better, the research careers, teachings and the lives of the authors of this piece. Their combined researches quadrupole devices led to the commercialization of the ion trap as a mass spectrometer by which mass spectral information became available at greatly reduced cost. Thus, the advent of commercial ion trapping instruments permitted a greater use of mass spectrometry in both technically advanced countries and those less well advanced. The greatest impact in health services was mass spectrometric analysis of environmental problems, well and stream water, food free of pesticides, etc., and forensic sciences. Our combined indebtedness to Dr Dawson is manifested by this appreciation of his scientific work, the highlighting of his main contributions, and creation of a substantive reference source to his work that can be used by other scientists. A comprehensive list of Dr Dawson's publications, including abstracts or summaries, has been arranged in chronological order of date of submission

GAIA: Composition, Formation and Evolution of the Galaxy

The GAIA astrometric mission has recently been approved as one of the next two `cornerstones' of ESA's science programme, with a launch date target of not later than mid-2012. GAIA will provide positional and radial velocity measurements with the accuracies needed to produce a stereoscopic and kinematic census of about one billion stars throughout our Galaxy (and into the Local Group), amounting to about 1 per cent of the Galactic stellar population. GAIA's main scientific goal is to clarify the origin and history of our Galaxy, from a quantitative census of the stellar populations. It will advance questions such as when the stars in our Galaxy formed, when and how it was assembled, and its distribution of dark matter. The survey aims for completeness to V=20 mag, with accuracies of about 10 microarcsec at 15 mag. Combined with astrophysical information for each star, provided by on-board multi-colour photometry and (limited) spectroscopy, these data will have the precision necessary to quantify the early formation, and subsequent dynamical, chemical and star formation evolution of our Galaxy. Additional products include detection and orbital classification of tens of thousands of extra-Solar planetary systems, and a comprehensive survey of some 10^5-10^6 minor bodies in our Solar System, through galaxies in the nearby Universe, to some 500,000 distant quasars. It will provide a number of stringent new tests of general relativity and cosmology. The complete satellite system was evaluated as part of a detailed technology study, including a detailed payload design, corresponding accuracy assesments, and results from a prototype data reduction development.Comment: Accepted by A&A: 25 pages, 8 figure

Chip-scale quadrupole mass filters for a Micro-Gas Analyzer

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 181-188).Mass spectrometers are powerful analytical instruments that serve as the gold standard for chemical analysis. This tool has numerous applications ranging from national security, industrial processing, environmental monitoring, space exploration, and healthcare to name a few. These systems are typically large, heavy, power-hungry, and expensive, constraining its usage to a laboratory setting. In recent years, there has been a growing interest in utilizing mass spectrometers outside the lab. Microelectromechanical systems (MEMS) technology holds the promise of making devices smaller, faster, better, and cheaper. The Micro-Gas Analyzer (MGA) project attempts to leverage MEMS capabilities to create a low-cost, high-performance, portable mass spectrometer. Batch-fabrication of various components for the MGA has been demonstrated to date, but the mass filter component still has room for exploration. Chip-scale quadrupole mass filters achieved entirely through wafer-scale processing have been designed, fabricated, and characterized. The device integrates the quadrupole electrodes, ion optics, and housing into a single monolithic block, eliminating the electrode-to-housing misalignments inherent in other quadrupoles. To achieve this integration, unconventional square electrode geometry was utilized. This concept formed the basis of the micro-square electrode quadrupole mass filter (MuSE-QMF). The MuSE-QMF demonstrated mass filtering with a maximum mass range of 650 amu and a minimum peak-width of 0.5 amu at mass 40, corresponding to a resolution of 80.(cont.) More importantly, the design concept can be extended to complex architectures that were previously unachievable. Batch-fabricated quadrupoles in arrays, in tandem, or with integrated pre-filters can have significant impact on the future of portable mass spectrometry. Additionally, the MuSE-QMF makes a case for operation in the second stability region, and motivates new studies on quadrupole ion dynamics.by Kerry Cheung.Ph.D