The Beam Energy Scan phase II (BES-II), performed in the Relativistic Heavy Ion Collider (RHIC) from 2019 to 2021, explored the phase transition between quark-gluon plasma and hadronic gas. BES-II exceeded the goal of a fourfold increase in the average luminosity over that achieved during Beam Energy Scan phase I (BES-I), at five gold beam energies: 9.8, 7.3, 5.75, 4.59, and 3.85 GeV/nucleon. This was accomplished by addressing several beam dynamics effects, including intrabeam scattering, beam-beam, space charge, beam instability, and field errors induced by superconducting magnet persistent currents. Some of these effects are especially detrimental at low energies. BES-II achievements are presented, and the measures taken to improve RHIC performance are described. These measures span the whole RHIC complex, including ion beam sources, injectors, beam lifetime improvements in RHIC, and operation with the world's first bunched beam Low Energy RHIC electron Cooler (LEReC).

RHIC provided Au+Au collisions at beam energies of 5.75 and 4.59 GeV/nucleon for the physics program in 2020 as part of the Beam Energy Scan II experiment. The machine configuration and operational experience at these energies are presented in this report with emphasis on their unique features which include but are not limited to the addition of a second RF system to enable large longitudinal acceptance and to reduce the intrabeam scattering rate at 5.75 GeV/nucleon, the exploration of the tune space for better performance, the use of lower frequency cavities for alleviating space charge effects, and the world-first operation of cooling on colliding beams with an RF-accelerated bunched electron beam.

RHIC will provide Au-Au collisions at beam energies of 5.75, 4.59 GeV/nucleon for physics program in 2020, and at beam energy of 3.85 GeV/nucleon for physics program in 2021 as part of the BeamEnergy Scan II (BES-II). The oper- ational experience gained in the first year (2019) of BES-II operation will be applied toward operations in the coming years. This article will present some technical details and the outlook of the BES-II operations in the coming years.

The FY18 RHIC physics program calls for Ru-Ru and Zr-Zr collisions at 100GeV using isobaric Ruthenium and Zirconium ions, each having 96 nucleons. In the injector chain, these two ions must come from Tandem and EBIS source, respectively. To reduce systematic errors in the detector, the luminosity for the two species is matched as closely as possible, and the species are switched frequently. Several bunch merges are needed in the Booster and AGS to reach the desired bunch intensity for RHIC. The setup and performance of injector chain with these ions are reviewed.