Beam neutralization

There are several methods in use for producing these clusters. Particle bombardment or laser vaporization of a graphite surface leads to direct formation of ions that can be detected by mass spectrometry. These are normally of relatively small size (n<30). By laser vaporization of graphite into a molecular beam neutral... 

To overcome this problem, we have modified a commercial ion gun to generate a diffuse fast-atom beam [116, 117]. The ion beam neutralizer shown in Figure 7 consists of a multi-hole metal plate through which the primary ions pass. The ions are neutralized by the ion/surface interactions that occur as the beam passes through the metal aperatures and by charge-exchange reactions that occur within the gun assembly. A repeller grid is used to remove the residual ions from the neutralized beam. 

Figure 7. Schematic diagram of commercial ion gun modified with an ion beam neutralizer. Reproduced with permission from Ref. 116. Copyright 1983, Elsevier Science Publishing Co.

The portal frame was reasonably comprehensively instrumented. Back-to-back rosette strain gauges were bonded to the beam neutral axis at midspan and a further 24 uniaxial strain gauges were bonded to the frame at the locations shown in Figure 1(a). Nine dial gauges, and four LVDTs... 

The final step in an electrostatic thrust device is neutralization of the ion beam by injection of electrons. This neutralization must take place within the beam itself—it is not sufficient merely to eject an equal current of electrons at some other part of the device to maintain overall neutrality of the vehicle. Without beam neutralization, theory shows that the ions, due to mutual repulsion, will quickly diverge, and even return to the neighborhood of the emitter. In laboratory facilities, this ion beam turnaround has been observed only occasionally... 

Currents induced in the plasma generated by the beam neutralize the axial component of the ion current. Azimuthal plasma currents on the other hand, are observed only in heavier gases - air, N2, and He, but not in H2 or D2. In hydrogen the diamagnetic signals shown in Fig. 7 agree with measurements on the circulation ion density by Faraday cups indicating almost no azimuthal neutralization. In... 

However with a technique similar to beam neutralization in proton beam-foil spectroscopy energetic muonium in vacuum was observed 5. 

D. Gardner, W. Sainty, Ion current measurement and ion beam neutralization using a novel Faraday Cup operable during deposition, in Proceedings of the 50th Annual Technical Conference, Society of Vacuum Coaters, 2007, p. 534. 

Beam neutralization The addition of electrons to an ion beam so that there is no net charge in a volume of the beam, even though individual species in the beam still have an electrical charge. 

Neutralization (electrical) The removal of an electrical charge by the addition of charges of the opposite sign. Example Surface charge neutralization. See also Beam neutralization. 

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