RBS Instrumentation: Focusing Elements

Two ion optical components are usually placed between the accelerator and the sample chamber. A magnetic field separates any He-, He, or He+ from the He++ beam. A quadrupole lens shapes the beam and focuses it into the sample chamber. Relatively strong ion bending and focusing components are required for these high energy (rigid) beams. The high energy beam provides an important analytical advantage.

Samples in RBS can be insulating, in contrast to most charged particle analytical methods. Even if such samples charge to a few kilovolts, the rigid beam is barely deflected. Sample charging causes only slight perturbations in RBS spectra because the kilovolt charging effect is a small fraction of the megavolt particle energies.

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