  Radio Frequency Quadrupole (RFQ) accelerators often need to face the
challenges of space charge effects from high beam currents. This study
investigated how to reach RFQ beam dynamics designs with not only high beam
transmission and short structure length but also high beam quality
simultaneously. To avoid beam instabilities induced by emittance transfer, a
so-called el/et (ratio of the longitudinal and transverse emittances) = 1.0
design guideline is being proposed. The application of this design guideline
integrated with the BABBLE/NFSP design method for a high current, high
frequency, high injection energy RFQ accelerator is described.

Accelerator Physics