Morita, Y. Akai, K. Furuya, T. Kabe, A. Mitsunobu, S. Nishiwaki, M. JACoW Geneva, Switzerland 978-3-95450-178-6 10.18429/JACoW-SRF2015-MOPB116 English 443-447 MOPB116 cavity vacuum factory operation SRF Contribution to a conference proceedings 2015 2015-12 http://dx.doi.org/10.18429/JACoW-SRF2015-MOPB116 http://srf2015.vrws.de/papers/mopb116.pdf The Q factors of the eight superconducting accelerating cavities gradually degraded during the long-term operation of the KEKB accelerator. Since we will re-use those SRF cavities for the SuperKEKB, the performance degradation will be a serious problem. Several cavities degraded their performance significantly at high accelerating fields. The Q degradation is still acceptable for the 1.5 MV operations at SuperKEKB. However, further degradation will make the operation difficult. In order to recover the cavity performance, we developed horizontal high pressure water rinsing (HHPR). This method uses a horizontal high pressure water nozzle and inserts it directly into the cavity module. We applied this method to two degraded cavities and their degraded Q factors recovered above 10⁹ at around 2 MV. In this paper we will present the HHPR method, high power test results after the HHPR and the residual gas analysis.