Transport of Intense, High-Brightness Ion Beams

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While transporting high perveance beams, three effects primarily govern their trajectories and phase-space behavior, namely, the space charge force, the emittance, and the external focusing fields. A good understanding of these effects is warranted in order to design and build an efficient transport system. In the present collaborative work, an experimental study on the transport of a high perveance (beam energy < 20keV, beam current = 1 - 20 mA) HeィイD1+ィエD1 beam is carried out. An intense HeィイD1+ィエD1 ion source has been developed. An electrostatic quadruple (ESQ) transport system has been designed and built to transport the beams extracted from the source. Various diagnostic tools, such as emittance meters and beam profile monitors, are developed. In beam transport experiments using the ESQ lesnes initial settings of the applied voltage obtained from a beam envelope code. It has been confirmed that the ESQ lens system provides a good focusing property and that a set of focusing parameters has a reasonably large range of acceptance of beam parameters. The present experimental results also indicate that the ESQ system can transport HeィイD1+ィエD1 beams without any beam loss, and without any significant emittance growth over a length of about 70-cm when the normalized beam perveance is less than 0.003. Evidence of non-linear effects has been noted in the emittance diagram. Distortions in these emittance diagram are primarily due to chromatic aberrations when the beam approaches the boundary of the ESQ electrodes and the beams near the center and the peripheral regions experience significantly different focusing fields.