Electrostatic focussing

Carswell and Milstead made thin sources of U and Pu by electrostatically focussing a jet of the material to be plated which was dissolved in a volatile solvent. 

Each of the two beamlines are focussed by a single electromagnetic quadrupole doublet, and a beam size of about 1 pm2 is achieved with a beam current of approximately 50 pA. Electrostatic deflectors are mounted to permit beam sweeping on the sample both to produce images and to limit heating effects. 

Auger analysis of small features. The primary electron beam column is similar to that in electron microscopes, and it may contain both electrostatic and magnetic lenses for beam focussing as well as quadrupole deflectors for beam steering and octopole lenses for beam shaping. 

By employing the variation of the work term Awp in eq 31, we are actually focussing in large part on the electrostatic interaction in the ion pair, since the other structural factors drop out by cancellation in the comparative procedure used in eq 28. Thus the contribution to Awp consists largely of a coulombic potential (i.e., -e2/rpA) the m an separation r in the... 

In all physical and chemical processes, and in particular those of relevance to geochemistry, that involve the oxide/aqueous solution interface, it is important to understand the general, non-specific characteristics of that interface before focussing on those specific processes or mechanisms of interest. Due to the structure of mineral surfaces, the mineral oxide/aqueous solution interface will invariably acquire a net charge or electrostatic potential relative to the bulk solution. The electrical state of the interface will depend in part on the chemical reactions that can take place on the mineral surface, and in part on the electrolytic composition of the aqueous environment. 

Once the ions have been focussed through the orifice and into the analyser portion they are further focussed by electrostatic lenses into the first of three axially aligned quadrupole arrays. The first and third arrays can be operated as mass filters while the central quad (Q2 in Figure 1) functions only as an ion guide, incapable of resolving one mass from another. 

Electrons from the heated tungsten filament are accelerated to the annular anode. Depending on the anticathode material a characteristic fluorescence radiation is emitted, passes through a thin Aluminum window and induces photoelectrons on the surface of the analytical sample. These photoelectrons are deflected in the spherical electrostatic analyzer, double focussed to eliminate stray electrons and finally counted by the electron multiplier. The whole system works under a vacuum of 10-s to 10 7 torr or even 10 10 torr, if surface properties have to be studied. This vacuum is generated by a Titanium... 

A few years ago, we began a research program to develop methods of analysis which would involve the use of FAB and a high performance tandem mass spectrometer. The tandem instrument was the first triple sector mass spectrometer to be designed and built by a commercial instrument company (Kratos of Manchester, U.K.). The first mass spectrometer of the combination is a double focussing Kratos MS-50 which is coupled to a low resolution electrostatic analyzer, which serves as the second mass spectrometer U). This FAB MS-MS combination has been used to verify the structures of an unknown cyclic peptide (2), a new amino acid modified by diphtheria toxin (3), and an ornithine-containing lipid (4). A number of methods have also been worked out which rely on this instrumentation. They Include the structural determination of cyclic peptides (5), nucleosides and nucleotides (6), and unsaturated fatty acids (7) and the analysis of mixtures of both anionic (8) and cationic surfactants (9). 

Fig. 1.10. The fully electrostatic high-brightness positron beam developed by the Brandeis group. The positron Soa gun is located near B. The beam is deflected at C using a cylindrical mirror analyser and focussed onto a remoderator in chamber D. The extracted beam is then focussed and remoderated at the lower left of D. The double brightness-enhanced beam is then transported into the target chamber, E. Reprinted from Nucl. Instrum. Methods B143, Charlton, Review of Positron Physics, 11-20, copyright 1998, with permission from Elsevier Science.

Referring again to Figure 2.4, the slow positrons emitted from the boron were accelerated and focussed by the electrostatic lens system... 

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