Yamamoto, Y. Dohmae, T. Egi, M. Hara, K. Honma, T. Kako, E. Kojima, Y. Konomi, T. Kubo, T. Matsumoto, T. Miura, T. Nakai, H. Nakanishi, K. Park, G.-T. Saeki, T. Shimizu, H. Shishido, T. Takenaka, T. Umemori, K. JACoW Geneva, Switzerland 978-3-95450-191-5 10.18429/JACoW-SRF2017-THYA02 English 722-728 THYA02 ion cavity cryomodule operation accelerating-gradient Contribution to a conference proceedings 2018 2018-01 https://doi.org/10.18429/JACoW-SRF2017-THYA02 http://jacow.org/srf2017/papers/thya02.pdf In the Superconducting RF Test Facility (STF) in KEK, the cooldown test for the STF-2 cryomdoule with 12 cavities has been done totally three times since 2014. In 2016, the 3rd cooldown test for the STF-2 cryomodule including the capture cryomodule with 2 cavities was successfully carried out. The main achievement is the vector-sum operation with 8 cavities at average accelerating gradient of 31 MV/m as the ILC specification (2 of 8 cavities achieved 36 MV/m with piezo compensation), and the others are the measurement for Lorenz Force Detuning (LFD) and unloaded Q value, and Low Level RF (LLRF) study, etc. In this paper, the result for the STF-2 cryomodule in three cooldown tests will be presented in detail.