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Reaction mechanism of metastable peak formation on stainless steel cycloid envelope of mass spectrometer exposured to gaseous mixtures
Cycloid mass spectrometers offer powerful advantages for isotope ratio measurements, including double focusing (mass and energy), linear mass dispersion over a large spatial area, and a small footprint. However, the linear cycloid has not been adopted as widely as other mass analyzer designs, in part because of challenges with utilizing common ion detectors such as electron multipliers and Faraday cups. Integration of a linear cycloid with a capacitive transimpedance amplifier detector arrays can overcome these challenges, resulting in a compact powerful mass spectrometer for precision isotope ratio measurements.
The Virtual Slit Cycloidal Mass Spectrometer is a unique instrument for analysis of particles with mass spectrometry. It combines the unique properties of the cycloidal mass analyzer with capacitive transimpedance amplifier array detectors to make a portable instrument potentially capable of high sensitivity measurements on single particles, including high precision isotope ratios.
An ion sensitive emulsion detection system has been considered for use in a cycloidal focusing mass spectrometer to measure the various atomic species which comprise the solar plasma. The responses of Ilford Q2 and Kodak SC7 emulsions were measured with N(+) ions at 6 keV to 10 keV, He(++) ions at 750 eV to 2500 eV, and H(+) ions at 550 eV to 1400 eV. These ions have the approximate range of velocities (about 300-500 km/sec) encountered in the solar wind. The work was carried out on a specially prepared magnetic sector mass analyzer. Characteristic response curves were generated, each one utilizing approximately 50 data points at three or more current densities. In addition to the ion response, measurements of the response of these emulsions to a photon flux simulating the visible portion of the solar spectrum were made. The results obtained will be presented in detail and interpreted in relation to other data available for these emulsions.
A miniature mass spectrometer that incorporates features not typically found in prior mass spectrometers is undergoing development. This mass spectrometer is designed to simultaneously measure the relative concentrations of five gases (H2, He, N2, O2, and Ar) in air, over the relative-concentration range from 10(exp -6) to 1, during a sampling time as short as 1 second. It is intended to serve as a prototype of a product line of easy-to-use, portable, lightweight, highspeed, relatively inexpensive instruments for measuring concentrations of multiple chemical species in such diverse applications as detecting explosive or toxic chemicals in air, monitoring and controlling industrial processes, measuring concentrations of deliberately introduced isotopes in medical and biological investigations, and general environmental monitoring. The heart of this mass spectrometer is an integral combination of a circular cycloidal mass analyzer, multiple fixed ion collectors, and two mass-selective ion sources. By circular cycloidal mass analyzer is meant an analyzer that includes (1) two concentric circular cylindrical electrodes for applying a radial electric field and (2) a magnet arranged to impose a magnetic flux aligned predominantly along the cylindrical axis, so that ions, once accelerated into the annulus between the electrodes, move along circular cycloidal trajectories. As in other mass analyzers, trajectory of each ion is determined by its mass-to-charge ratio, and so ions of different species can be collected simultaneously by collectors (Faraday cups) at different locations intersected by the corresponding trajectories (see figure). Unlike in other mass analyzers, the installation of additional collectors to detect additional species does not necessitate increasing the overall size of the analyzer assembly.
An experimental program was undertaken in which mass accretion rates, as determined by a liquid nitrogen cooled quartz crystal microbalance, were compared with the mass flux rates, as determined by both a cycloidal type and a quadrupole type residual gas analyzer for five simple materials. The data indicate a high degree of correlation between these instruments insofar as the shape of the curves. There are large variations however among the absolute values.
The HERS detector of the Ion Mass Spectrometer on the Giotto spacecraft measured the 3 dimensional distribution of picked-up cometary protons over a distance of 6 million km upstream of the bow shock. The protons are elastically scattered out of their original cycloidal trajectories such that they are nonuniformly distributed over a spherical shell in velocity space. The shell thickness increases as the bow shock is approached. Inside the shock, the cometary protons are difficult to distinguish from the heated solar wind protons.
The High Energy Range Spectrometer (HERS) of the Ion Mass Spectrometer on the Giotto spacecraft measured the 3-dimensional distribution of picked-up cometary protons over a distance of approximately 8 million km upstream of the bow shock of Comet Halley. The protons were observed to be elastically scattered out of their original cycloidal trajectories such that they were nonuniformly distributed over a spherical shell in velocity space. The shell radius (relative to its expected radius) and thickness increased as the bow shock was approached. Downstream of the shock, the cometary protons could not be distinguished from the heated solar wind protons.
The HERS detector of the Ion Mass Spectrometer on the Giotto spacecraft measured the 3-dimensional distribution of picked-up cometary protons over a distance of about 8 million km upstream of the bow shock of comet P/Hally. The protons were observed to be elastically scattered out of their original cycloidal trajectories such that they were nonuniformly distributed over a spherical shell in velocity space. The shell radius (relative to its expected radius) and thickness increased as the bow shock was approached. Down-stream of the shock, the cometary protons could not be distinguished from the heated solar wind protons.