Claude B. Reed1, Jerry A. Nolen1,2, Yoichi Momozaki1, James R. Specht1,2, David B. Chojnowski1, and Felix Marti2
1 Argonne National Laboratory, Argonne, IL, 60439, USA
2 Facility for Rare Isotope Beams, Michigan State Univ., E. Lansing, MI 48824, USA
This paper reports the ESH Issues, and how they were resolved, to enable a water-cooled proton beam-on-liquid lithium stripper film experiment to be safely conducted. The Facility for Rare Ion Beams (FRIB) currently under construction at Michigan State University (MSU) will accelerate all ions, up to uranium, to an energy of 200 MeV/u with beam power up to 400 kW. To increase the charge state of the ions and reduce the number of accelerating modules in the linac, a charge stripper is needed that can strip uranium ions from, for example, the charge state 33+ to 78+. Developing the charge stripper for such an intense uranium beam is a severe technological challenge; the leading design choice for this stripper is a thin, high speed, liquid lithium film of thickness ~10 μm and the uranium beam will deposit about 700 W in the film while passing through and losing about 2% of its kinetic energy. Previous R&D at Argonne National Laboratory (ANL) has demonstrated the stable formation of such a film, but prior to the work reported here, the film has not been tested with beam.
To provide a suitable proton beam for thermal testing of ANL’s liquid lithium stripper film, a water-cooled ion source, originally built for the Low Energy Demonstration Accelerator (LEDA), was borrowed from Los Alamos National Laboratory (LANL) and moved to MSU where it was re-commissioned after a new beam transport system, comprised of two intermediate water cooled collimators, was built and installed. The re-commissioned ion source was then moved to ANL and mated with Argonne’s lithium stripper system, where the proton beam deposited in the lithium film a power density comparable to 30 % of the maximum power density expected at FRIB when accelerating 400 kW of U at 200 MeV/u. Video of the beam-on-film test will also be discussed. Because the protons only penetrate the first 1.5 μm of the lithium film’s 10 μm thickness, the net effect, in that first 1.5 μm of the film, is a power density higher than FRIB by a factor 2. Hence, a stripper based on this liquid lithium technology is now the base-line design choice for FRIB.
This research was supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.