Filter, Wien

Figure Bl.6.3 Electron energy analysers that use magnetic fields (a) the trochoidal analyser employing an electromagnet, (b) the Wien filter and (c) the sector magnet analyser. Trajectories for electrons of different energies are shown.

Figure Bl.23.5. Schematic illustration of tlie TOE-SARS spectrometer system. A = ion gun, B = Wien filter, C = Einzel lens, D = pulsing plates, E = pulsing aperture, E = deflector plates, G = sample, PI = electron multiplier detector with energy prefilter grid and I = electrostatic deflector.

There are otlier teclmiques for mass separation such as tire quadmpole mass filter and Wien filter. Anotlier mass spectrometry teclmique is based on ion chromatography, which is also capable of measuring tire shapes of clusters [30, 31]. In tills metliod, cluster ions of a given mass are injected into a drift tube witli well-defined entrance and exit slits and filled witli an inert gas. The clusters drift tlirough tills tube under a weak electric potential. Since the... 

Because of its lower beam energy, a LEIS ion source is much more compact than an accelerator for MeV ions, but it has the same purpose - to provide a beam of ions with well defined energy and mass. In LEIS, the latter demand is fulfilled by a Wien filter that selects ions of one specific mass, as does the deflection magnet in RBS. In... 

Bassi et al. [70] have described IMR-MS for online gas analysis with a sensitivity of 100ppb-l ppm. A mass-selected ion source allows the use of three different primary ion beams (Xe+, Kr+ and CF3I+), covering the recombination energy range from 10.23 to 14.67 eV. For fast measurements, the change from one primary ion to another can be achieved by a Wien filter. IMR-MS allows quantitative analysis. 

A filter that combines both a magnetic and electric field is the so-called Wien filter (or velocity filter). In this case, charged ions pass through a region characterized by uniform magnetic and electric fields at right angles to each other and to the direction of incident ions only those particles for which the module of the Lorentz... 

For this experiment Bainbridge used the high-precision mass spectrograph he had developed by combining a Wien filter with a 180° magnetic analyzer.13... 

For example, experiments might be conducted with ions from one or more of these groups to distinguish between linear and nonlinear collision processes (34). This author and his co-workers recently described an apparatus that combines a LMI source and a Wien filter to produce a focused beam of particles which are selected by mass and type (28). When completed, this versatile probe will be used to investigate secondary emission from liquid organic matrices. 

Hitachi announced the development of the third commercial microprobe instrument, the ion microprobe analyzer IMA-2 in 1969 [30]. This instrument placed a scintillator close to the sample for secondary electron imaging. A Wien filter, for primary beam mass selection [31], and an electron spray, for charge compensation on insulating samples [32], were added later. 

The retardation and deflection techniques represent the simplest methods of analysis using electrostatic fields. More sophisticated methods of electrostatic analysis are, of course, available and both cylindrical and hemispherical electrostatic analysers have been used to measure translational energies of ions formed by decomposition within ion sources [633, 667, 789, 790]. A Wien filter has been similarly employed [163]. 

Fig. 11.5. Sketch of the MAJESTIX setup. The vacuum system is divided into a preparation chamber and a particle-beam chamber, separated by a gate valve. The preparation chamber is also used as load lock. The main components in the particle-beam chamber are the ion gun system, comprising a Wien filter and deceleration...

When the Wien filter is switched off, the two pairs of counters in the Mott analyser allow the simultaneous measurement of the two transverse polarisation components Sn and (7(n xP). When the Wien filter is switched on the two polarisation components perpendicular to the magnetic field B are rotated through 90° (P P", see figs. 2.15 and 2.16), so that... 

By varying the extraction voltages on the skimmer, einzel lens and Wien filter, the ion currents due to the various species were detected and the Ha ion due to Reaction (44) was identified. Thereby, the existence of was inferred by Schnitzer and Anbar. 

SIMS requires an ultra-high vacuum environment, similar to AES and XPS. The ultra-high vacuum environment ensures that trajectories of ions remain undisturbed during SIMS surface analysis. The SIMS vacuum chamber and pumping system is not much different from that for AES and XPS. Figure 8.5 illustrates common SIMS structure in a vacuum chamber in which there are two main components a primary ion system and a mass analyzer system. The primary ion system includes a primary ion source, a Wien filter and ion beam deflector. The mass analysis system includes a secondary ion extractor filter, mass analyzer and ion detector. 

A further less commonly employed but very classical method for mass-selection is the Wien-filter which combines an electrostatic and a magnetic field for mass-selective cluster deflection. This device is applied in particular with the purpose to obtain large cluster currents for cluster-surface interaction and deposition experiments at moderate resolution [75, 76]. Another approach for size-selection in combination with a sputter source ]47] or a laser vaporization source [61,77,78] has been chosen recently. In both cases, a magnetic dipole field has achieved the size-selection. Subsequent deceleration of the size-selected clusters to less than 1 eV per atom enables soft-landing under UHV conditions [47]. Monodispersed chromium cluster beam densities range from 0.1 to 5nA mm, depending on the cluster size ]47]. 

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