Pushing the intensity envelope at the ATLAS linac

The ATLAS linac at Argonne National Laboratory has recently been upgraded for higher beam intensity and transport efficiency. Following the installation of the new RFQ, we have performed a high-intensity run using a 40Ar⁸⁺ beam. A beam current of 7 pμA was successfully injected and accelerated in the RFQ and the first superconducting section of the linac to an energy of 1.5 MeV/u. Since then, a new superconducting module was installed in the Booster section of the linac replacing three old cryomodules of split-ring resonators. The split-rings are known to cause excessive beam steering leading to beam loss which limits the maximum current in ATLAS. We are planning a second run to try to push the beam current higher and farther into the linac. The ultimate goal is to accelerate 10 pμA to the Booster exit at 5 MeV/u. Among the limitations encountered in the first run are the large beam emittance at the ECR source and the beam loss in the LEBT. The results of these attempts will be presented and discussed.