Xu Qingjin stayed at KEK from 5 June to 2 September to build large-grain niobium single-cells and learn about surface treatments.

In the International Linear Collider (ILC), superconducting cavities made of niobium will be used. Niobium is a superconductor - a material that loses its electrical resistance when cooled down to almost absolute zero. Clean and extremely smooth cavity surfaces are essential for achieving a high accelerating gradient. Manufacturing cavities from large-grain or single-crystal niobium may cut down expenses by eliminating some of the treatments that are necessary for fine grain cavities. Therefore the quality of the niobium becomes one of the most important points of cavity manufacturing. CBMM from Brazil, W.C.Heraeus from Germany, and Ningxia from China are the world leaders in niobium production. (See ILC NewsLine 13 July 2006)

In China, the ILC-IHEP group was founded in December 2005 and is led by Jie Gao, who is the only GDE member in China and an ILC regional leader in damping ring studies. About thirty members have been working on beam dynamics, damping rings and superconducting cavities. In the ILC-IHEP group, only young students and researchers are working on superconducting cavities. "We need more participation from all generations," Gao said.

Ge Ming Qi started working with Kenji Saito fom KEK on ILC-related superconducting cavity R&D in the beginning of 2006, with IHEP's Xu Qing Jin following him in June. In August, the IHEP-KEK collaboration on large-grain niobium started. ILC-IHEP provides niobium, and KEK offers field testing of the material.

Xu Qingjin is a post-doctoral researcher in an ILC group at IHEP. He visited KEK to learn more about the technology for setting up superconducting technology for the ILC at IHEP. With the help of Saito, he learned about cavity manufacturing that used Chinese large-grain niobium with a special surface treatment technique. He also conducted a comparative study of Brazilian niobium from CBMM and Chinese niobium from Ningxia.

Qingjin acquired his PhD on superconducting systems for the BEPCII detector magnet five months ago in China. "Cavities are very interesting for me because there are a lot of unknown parts, which is why I shifted my research focus from magnets to cavities," he said. "However, due to technical limits, the ILC-IHEP group cannot expect the same speed as the KEK group," Gao said. IHEP does not have an efficient centrifugal barrel polishing facility yet, but one has been ordered from a Chinese company. Electropolishing facilities are also not available at IHEP. IHEP's cavity will be sent to KEK for these necessary treatments. The IHEP-KEK collaboration will continue on the superconducting RF cavity study of large-grain niobium, high power couplers,and cryomodules.

From 5 to 7 December 2006, China will hold the "Perfum Montain Meeting on ILC." This meeting will strengthen China's strategic involvement in ILC collaborations. As co-chairman of the local committee, Gao is also preparing for the ILC GDE meeting from 4 to 7 February 2007 in Beijing, China. China hopes that this will be a strong push for Chinese participation.

-- Nobuko Kobayashi