The first cooldown of SCL3 cryogenic system

RAON, Rare isotope Accelerator complex for ON-line experiments, is the first superconducting linear accelerators in S. Korea. It will have three linear accelerators (Linac), SCL1, SCL2, and SCL3. Now, construction of the SCL3, the third superconducting Linac was finished in the middle of 2022 and the commissioning of its cryogenic system was done July, 2022. The first cooldown of the Linac with the cryogenic system was started from September, 2022 and their temperature was reached at 2.05 K in January, 2023. The first cooldown was successfully completed and the static and dynamic heat loads of the Linac were measured. This paper shows the results of the first cooldown and the heat load tests.