During the first three years since May 2022, FRIB has been operating safely meeting expectations of both scientific and industrial users with high machine availability, while ramping up the beam power to 20 kW for heavy ions including uranium. The paper summarizes the operational experience and challenges, accelerator improvement projects, expansions in user stations, accelerator R&D and workforce growth programs, and preparation for facility upgrades*.

The Facility for Rare Isotopes Beams (FRIB) enables groundbreaking research in nuclear physics, astrophysics, and fundamental interactions, as well as the societal applications of this work. Critical to the science program at FRIB is the Advanced Rare Isotope Separator (ARIS), which separates, identifies, and purifies fragments produced via projectile fragmentation and fission using a variety of beamline elements, including eight superconducting dipole magnets. An accurate magnetic rigidity calibration of these dipole magnets is crucial for obtaining peak fragment yields with optimal transport conditions in minimal time and informing simulations of fragment separator experiments. This work reports on the use of the FRIB linear accelerator to provide a U-238 beam of known energy, with accuracy of 0.1%. Charge states of the beam, formed in a thin foil can then be used to calibrate the ARIS dipole field vs bend radius over a range of rigidities. Due to saturation of the iron in the dipoles, the field vs bend radius curve is not linear and deviates significantly once the central field is above 1.5 T. Details of the procedure and results will be presented.

The Advance Rare Isotope Separator (ARIS) at FRIB provides in-flight purification of rare-isotope beams (RIB) generated by projectile fragmentation or fission on a target. Beams of stable ions from a driver linac impinge on a graphite target thin enough such that products main-tain velocities close to that of the incident beam. The incident primary beam impinges on-target at about 200 MeV/u (for uranium and higher for lighter species). The energy may be lower than the maximum allowed, de-pending on the requirements of the experiment. Using multi-charge state acceleration, the linac has most recently provided up to 20 kW on-target with a long-term goal of reaching 400 kW. Specialized magnets, collimators and other components have been integrated into the separator to withstand harsh conditions and facil-itate maintenance. The optics properties at the beam dump are important since the power density must be kept low enough to avoid failure of the material. We describe the various optics modes that have been developed for safe operations and maximizing the beam power allowed for RIB production.

The production of radioactive beams is crucial to understand structure of atomic nuclei away from stability. The operation of FRIB will ultimately provide access to previously unreachable unstable nuclei. Radioactive beams produced at FRIB can be selected and purified using the Advanced Rare Isotope Separator (ARIS) for further study by users. Ions are identified based on the energy loss, magnetic rigidity, gamma rays, time of flight, total energy in a suite of detectors. The transport of cocktail beams to the end of ARIS can impact the path length and the measured flight time. This can lead to uncertainty in the particle identification and worse timing resolution can occur if not corrected for. Characterizing the ion optics with position-sensitive detectors allows for corrections to the flight path of the ions. This in conjunction with the use of transfer matrices allows for the particle’s trajectory to be reconstructed and thus correct for the variation in the measured time of flight. These corrections are crucial for enhancing charge-state identification, especially in a high-resolution optics mode. The impact of applying a trajectory reconstruction method will be presented.