Einzel lenses

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.

A simple spectrometer that we have used successfully is shown in Figure 2. Electrons from an electron microscope hairpin tungsten filament are focused with an Einzel lens onto the monochromator entrance slit, pass through the monochromator and exit slit, and are focused on the sample s surface by additional electrostatic... 

Figure 13. Modified Velocity Map Imaging spectrometer showing the double einzel lens, L, Li, and 5-eV kinetic energy initially transverse trajectories from an extended source volume with Vjgp = 3000 V, Vext = 0.695 x Vjep, and Vl = Vli = 1000 V. Taken with permission from Ref. [102]. Copyright (c) 2005, American Institute of Physics.

The ion-source of the separator is fed by a capillary transporting the recoils therma— lized in the He-jet chamber. The separator beam is extracted at right angle to the axis of the beam line and then travels in a 120° magnet of index n=1/2. From the focal plane the mass-separated beam is then transported by means of a 6m long Einzel lens to a well-shielded collection chamber. A programmable tape-trans port device carries the activity to the counting station where X-rays, y-rays and particles are detected. 

Fig. 2 Layout of isotope separator in beam line C. The numbers indicate (1) He-jet recoil chamber, (2) beam-stdpper, (3) ion-source, (4) analysing magnet, (3) Einzel lens for transport of mass-separated beam, (6) tape-transport and counting station, (7) power/control rack of tape-transport, (8) power/control of mass-separa tor.

Figure 10 Ion optics (a) Einzel lens/Bessel box similar to optics used in Sciex ELAN 250,500, and 5000 ICP-MS instruments, (b) Multiple lens stack similar to those used in VG instruments, (c) Optics similar to those used in HP 4500. (d) Offset ion lens system developed by Hu and Houk [108,109] and used in Thermo ICP-MS. (e) Ion optics used in Seiko instrument with the quadmpole mounted perpendicular to the sampler-skimmer axis, (f) Single-lens-based ion optics similar to the Perkin-Elmer ELAN 6000 system.

Schnitzer and Anbar s experiments are rather similar to those of Baumann, Heinicke, Kaiser and Bethge Both employed plasma ion sources that employed by Schnitzer and Anbar was a hollow cathode duoplasmatron. Also, both used einzel lenses and momentum/charge analysis. But the different lifetimes of the doubly-charged negative ions studied dictated somewhat different analyses. Baumann, et al. used an electric deflection analysis after the magnetic sector, as already seen, whereas Schnitzer and Anbar employed a Wien velocity filter and einzel lens voltage variation prior to the magnetic sector. 

Extraction and acceleration of the negative ions from the duoplasmatron was accomplished with voltages of 5 to 15 kV. After passing through the einzel lens, the ions encounter a 30 cm Wien velocity filter. The ExB field of this filter allows analysis based only on the ion velocity according to... 

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. 

Pressure studies indicated a second power dependence of the Ha ion current on the pressure in the einzel lens chamber. Since similar effects were observed with Ar, Ne, H2, Kr and Xe, Schnitzer and Anbar conclude that the effect is not one solely involving H2. They concluded from these studies that the collisional effect is relatively insignificant and that the primary effect of the pressure is to enhance the initial production of ions and/or their extraction from the source. 

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