  Typical front-ends of modern light-ion high-intensity accelerators typically
consist of an ion source, a Low Energy Beam Transport (LEBT), a Radiofrequency
Quadrupole (RFQ) and a Medium Energy Beam Transport (MEBT), which is followed
by the main linac accelerating structures. Over the years, many LEBTs have been
designed, constructed and operated very successfully. In this paper, we present
the guiding principles and compromises that lead to the design choices of the
PXIE LEBT, including the rationale for a beam line that allows un-neutralized
transport over a significant portion of the LEBT whether the beam is pulsed or
DC.
