RFQ assembled and tuned in FRIB tunnel

In December 2016, the radio frequency quadrupole (RFQ) was assembled and tuned in FRIB's linear accelerator tunnel, marking a significant technical milestone for the FRIB Project.

The RFQ is a critical system of the FRIB linear accelerator, required to run the beam. The energy of the beam produced by FRIB ion sources is too low for the injection into superconducting radio frequency cavities, so the RFQ increases the beam energy from 12 kiloelectron volt/atomic mass unit (keV/u) to 500 keV/u and prepares the beam for the injection into the superconducting linac. The RFQ is a microwave cavity resonator that uses a high-frequency oscillating electromagnetic field to focus and accelerate a low-energy beam of ions.

The FRIB RFQ is a brazed copper structure with a total length of approximately 16 feet, approximately 3 feet wide. To simplify the manufacturing, the structure was split into five segments. Each segment weighs approximately 3 metric tons, together adding up to 15 tons for the whole RFQ.

A pair of water skids constantly pumps 300 gallons per minute (GPM) of precisely temperature-controlled water through the RFQ to remove excessive heat deposited on the walls of the RFQ. Prior to running the beam through the structure, FRIB staff will conduct an accelerator readiness review (ARR) focusing on safety and machine readiness.

A high-power test is planned for May, to be followed by the first ARR and the beam test in June. The demonstration of the beam acceleration in the RFQ is an important milestone for the project, enabling further beam commissioning of the superconducting linear accelerator.