On 11-12 July, the Facility for Rare Isotope Beams achieved a major project milestone by accelerating its first beams in three of forty-six superconducting cryomodules. This demonstrates for the first time that the major systems (front end, liquid helium plant, superconducting cryomodules) which were commissioned individually, work well together and can successfully accelerate beams of atomic particles.
Beams of argon and krypton were accelerated to the beam energy of 2 million electron-volts per nucleon (MeV/nucleon) required at project completion for the first three cryomodules.
The heart of FRIB is a high-power superconducting linear accelerator that will accelerate ion beams up to half the speed of light to strike a target, creating rare isotopes. The linear accelerator is made of cryomodules, which contain superconducting radio frequency (SRF) cavities that accelerate the beam while operating at temperatures a few degrees above absolute zero. Much like a heavy truck, heavy ion beams speed up slowly and the first three cryomodules accelerate the beam to 1 percent of 200 MeV/nucleon, the remaining 43 cryomodules will provide the other 99 percent of beam energy.
As FRIB prepares for operation in 2021, several stages of commissioning (integrated testing of individual devices and beam commissioning of devices working together) are planned to demonstrate readiness of the different segments of the accelerator. Integrated testing examines the functionality of the system.
The Department of Energy Office of Science has established Key Performance Parameters (KPP) for project success, and this second stage of FRIB linear accelerator commissioning required acceleration of both argon and krypton beams up to 1.5 MeV/nucleon. While this commissioning period was scheduled for two weeks, about 35 physicists and engineers worked together and accelerated an argon beam to 2.01 MeV/nucleon in one day of commissioning. The next day, the krypton beam was accelerated to the same energy. The demonstrated beam energy is 30 percent higher than required by the KPPs and provides technical margin, which is important to ensure overall mission success in one-of-a-kind accelerators.
Each commissioning sequence is preceded by an extensive, several-day Accelerator Readiness Review (ARR) by experts external to FRIB and MSU to ensure technical readiness, team readiness, and safety system readiness. FRIB passed its first Accelerator Readiness Review (ARR01) in July 2017. Successful completion of ARR01 paved the way for ARR02 in May 2018, and the go-ahead to accelerate beam through the first three cryomodules. Following this successful demonstration of the KPPs, FRIB will spend an additional week characterizing the accelerator with beam, and then stop beam operation and continue technical installation activities for the remainder of the year.
FRIB’s next beam-commissioning milestone (ARR03) planned for spring 2019 will include the first 15 cryomodules and the first of two 180-degree bending sections of the accelerator.
MSU is establishing FRIB as a new scientific user facility for the Office of Nuclear Physics in the U.S. Department of Energy Office of Science. Under construction on campus and operated by MSU, FRIB will enable scientists to make discoveries about the properties of rare isotopes in order to better understand the physics of nuclei, nuclear astrophysics, fundamental interactions, and applications for society, including in medicine, homeland security and industry.