Abstract: An assessment by the National Academy of Sciences (NAS) of the scientific merit for a future Electron Ion Collider (EIC) in the US concluded that such a facility would be unique in the world and enable indispensable research on current and compelling scientific questions. This assessment confirmed the recommendations of the 2015 Nuclear Science Advisory Committee (NSAC) for an EIC with highly polarized beams of electrons and ions, sufficient luminosity and sufficient, variable center-of-mass energy.

Proposals were requested for a cost-effective design that uses existing accelerator infrastructure to reduce the cost and risk of the project. One of the two proposals submitted for consideration originated from the Thomas Jefferson National Accelerator Facility (JLab), named JLEIC. An alternative approach for the JLEIC ion complex was proposed as part of the effort to produce a cost-effective, lower risk design. The primary goal was not to replace the baseline design, but rather to investigate alternative options for the different components of the ion complex that could lower the overall cost, reduce the footprint, mitigate the risk, and identify possible staging or future upgrades.

The alternative design studies for the JLEIC ion complex included: (1) a more compact ion linac, (2) two-stage ion boosters instead of one for injection to the collider ring, with a more compact non-figure-8 Pre-Booster ring as the first stage, and (3) a dual-function electron storage-ring / ion booster as a second stage Large Booster for ions. The results of these investigations will be presented and discussed.  Finally and most importantly, some aspects of the proposed alternative design components, such as the more compact linac, the two-booster system and the use of room-temperature instead of superferric magnets, were adopted into the final JLEIC baseline design.