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Package
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Trak Charged Particle Toolkit
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Input files
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IInput.DST, ILens.MIN, ILens.EIN, ILens.TIN, ILensZero.TIN
Download ImmersionLensArray.zip
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Description
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The example models transport of a space-charge dominated ion beam in a miniature array of electrostatically biased rings (a sequence of electrostatic immersion lenses). The top section of the upper figure shows a scaled view. The rings, with inner radius 4.0 mm and thickness 6.0 mm, are biased to +-10 kV (the voltage is adjustable in Trak). The gap between rings is 4.0 mm. The entrance and exit rings are at ground potential. The 20 mA parallel input beam of He++ ions has radius 3.0 mm and an angular divergence in x and y of 1.2 deg. The example represents a 200 mm section of a transport system. Techniques include the application of GenDist to create an entrance beam distribution and the creation of a periodic structure by copying and pasting a standard cell definition with a text editor and adding displacements.
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Results
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The lower section of the upper figure shows ion trajectories with inclusion of applied field, emittance and space-charge effects. Note that the radial scale is highly expanded. The beam is almost matched to the focal forces. All particles are transported to the exit with little change in radius and no change in emittance. The maximum electric field level is about 5 MV/m, well below vacuum breakdown levels. The lower figure shows that the system can be used as a beam dump with no applied voltage. Particle losses are spread over the system length. Only 5.6% of the current reaches the output. In this case, the maximum beam-generated potential can be identified as about 180 V.
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