Marcel Baril

Morphology and surface characteristics of particulates from silicon carbide industries

Faced with the lack of a correlation between health effects and exposures to known air contaminants in silicon carbide plants, an attempt was made to better characterize particles from these working environments with the use of electron microscopy with energy dispersive x-ray analysis and selected area electron diffraction, x-ray photoelectron spectroscopy and scanning Auger spectroscopy. The occurrence of SiC fibers was confirmed. SiC particulates were shown to be covered largely by silicon dioxide islets, heterogeneously distributed at the surfaces. These findings are discussed briefly in relation to the hypothesis on the toxicity of fibers and to the Altree-Williams and Sprogis risk function.

Etude des proprietes fondamentales de l'equation de hill pour le dessin de filtre quadrupolaire

Abstract The normalised solution of the Hill equation and the equivalence of initial conditions is presented first. Modulo π decomposition of the independent variable shows the importance of the transfer matrix for one cycle. Trace conservation combined with decomposition of the matrix into the Twiss form and calculation of its nth power give the possibility of studying the stability of the trajectories. Functions α, β and γ being defined. the differential relations which govern them are established. By introducing a variable w, related to the β functions, it is shown that stable solutions can be expressed as the product of an envelope function and a modulation function. The latter is the most significant for application to the quadrupolar filter. The relationship between the Courant and Snyder invariant, representative ellipses and the α, β and γ functions is also derived. Finally it is shown how to go from one residual phase to another and simplifications are obtained by using an even generating function.

Characterization of Airborne Dust from Two Nonferrous Foundries by Physico-chemical Methods and Multivariate Statistical Analyses

Airborne particulate matter was sampled at a copper smelter and at an aluminum casting plant. Size, shape, quantity, and microlocalization of chemical species in the particulates were measured using closed cassettes, cascade impactors, scanning electron microscopy, X-ray diffraction, infrared and atomic absorption spectrophotometries, secondary ion mass spectrometry, and photoelectron spectroscopy. Cluster and principal components analyses were used in interpreting results. Aerosol chemistry varies as a function of size, and composition becomes more complex as the aerosol size drops into the respirable fraction and lower. Surface chemical properties are evidenced where, generally, volatile species are enriched. A few site-specific elements and characteristics were identified. The formation of particulates may often be related to process and practices, yet the actual distribution of species in the air remains an intricate matter.

The Multipassage Magnetic Mass Spectrometer

A new kind of magnetic mass spectrometer is described. It consists of (n) magnetic prisms integrated into a single pole piece and (n−1) mirrors which return the beam from one prism to the other. It is shown that by an appropriate choice of the parameters of the apparatus the resolving power increases linearly with the number of passages in the prism. Experimental results verify the theory. Other properties of this system are also discussed.

Studies of three‐cylinder electrostatic mirrors and lenses

With the aim of using it in mass spectrometry, we have tried to find an axisymmetric electrostatic system with very particular characteristics, viz. reduced spherical and chromatic aberrations. We chose a system made up of three coaxial cylinders of radius ρ. The inner electrode is 0.90 ρ long and is separated from the outer cylinders (which are taken to be of infinite length) by two identical gaps of 0.40 ρ. This system has been studied from both the mirror and the lens point of view. The mirror is studied using two electrostatic parameters. The potentials of the three cylinders are reffered to as V1, V2, and V3. The first parameter used is Rd=100 (V1−V2)/(V1−V3) and the second is V3/V1. For six values of Rd, ranging from 100 to 74, we examine the paraxial characteristics and the coefficients of spherical and chromatic aberration as a function of V3/V1. We only deal with the area where the mirrors are convergent and where the radii of curvature do not exceed 10ρ. For the values of Rd studied, other than ...

Optical properties of a toroidal electrostatic mirror in its plane of symmetry: application to a cylindrical condenser

This paper is concerned with the evaluation of the optical properties of the portion of a beam of charged particles lying in the plane of symmetry of any toroidal condenser used as an electrostatic mirror. It gives a general treatment that permits the calculation of the optical characteristics and the aberrations when a trajectory and its derivatives relative to the entry energy and angle are known. Results are applied to the case of a cylindrical condenser, resulting in an important extension of the knowledge of its properties. No attention is given to space‐charge effects and to the motion off the plane symmetry where the electric field is generally not central anymore.

Ion optics of a high resolution multipassage mass spectrometer with electrostatic ion mirrors

Abstract Ion trajectories in an electrostatic ion mirror are calculated. The interferences of the extended fringing fields of the mirror with finite aperture are studied. The results of the calculations are represented by three transfer matrices, which describe ion trajectories under the effects of a fringing field at the entrances, of an idealized mirror region, and of a fringing field at the exit. The focusing effects and ion-optical properties of mass spectrometers with electrostatic ion mirrors can be evaluated by using these transfer matrices. A high performance multipassage mass spectrometer is designed. The system has one magnet and four electrostatic sector analyzers and two ion mirrors. The double focusing condition and stigmatic focusing condition are achieved in any passage of the system. The mass resolution increases linearly with the number of passages in a magnet.

The toroidal condenser: II. Distribution in the plane of symmetry — the equipotentials — the rα case

Abstract A way of calculating the electrostatic potential in a general tore from a given distribution in the plane of symmetry is exposed. The potential being known in the tore, any equipotential is obtained as an expansion the coefficients of which can be successively determined. The case of an rα potential in the plane of symmetry leads to hypergeometric expansions in spherical coordinates and to simple equations readily amenable to computation for the equipotentials.

Motion of Charged Particles in the Normal Section of a Cylindrical Condenser

The rotation angle φ of a charged particle in a cylindrical condenser, is evaluated by an exact series expansion which was deduced by De Celles in a previous paper. The derivatives of φ relative to θ (the angle between the radius and the tangent to the trajectory) and E (the kinetic energy of the particle) are deduced and evaluated. Our techniques for the numerical evaluation of the preceding values are discussed and results are presented graphically. Maximum error coming from truncation is treated. The knowledge of φ and its derivatives enable one to calculate the optical properties of a charged particle beam centered on a privileged trajectory. A different expansion for φ, useful for small energies and an algorithm for its calculation, is given.

SELECTIVE SAMPLING AND CHEMICAL SPECIATION OF AIRBORNE DUST IN FERROUS FOUNDRIES

Airborne dust was selectively sampled in three ferrous foundries. Granulometric fractions were analyzed by using standard methods of industrial hygiene to determine the concentrations of dust, crystalline silica, and metal fumes. Physicochemical techniques such as secondary ion mass spectrometry (SIMS), electron spectroscopy for chemical analysis (ESCA), and electron microscopy were used to probe the heterogeneity of the dust particles. The trend in airborne dust concentrations seemed to be explainable by the extent of natural or mechanical ventilation in the foundries, although the differences between foundries were generally not statistically significant. Quartz was present in large and medium-size particles and absent in small (< 0.5 µm) particles. Lead was always concentrated in the small particle fraction and was preponderant in the foundry where untreated scrap metal was used. Clustering and multivariate analysis of metallic element relative concentrations were consistent with the model of low-boili...