The first Korean 1.5 GHz SRF cavity for ILC R&D.

Results from two vertical tests that were conducted at JLab.

In the end of 2004, the Pohang Accelerator Laboratory, a synchrotron light source facility in Korea, organised an ILC Task Force Team. Ever since, the members have been working in various fields of the ILC project, searching for suitable contributions as a small scale laboratory. The team's main linac group especially made some efforts to study superconducting cavity related technologies in collaboration with with K. Saito's group at KEK. Finally, by applying the knowledge acquired through ILC related research, PAL developed the first Korean 1.5 GHz SRF cavity.

The developed cavity is a prototype of the third harmonic cavity which will be installed in the PAL storage ring to increase the electron beam lifetime, as well as to improve the beam stability. PAL performed all processes, including the physics and engineering design and the fabrication with electron beam welding. Because the PAL SRF facility, which will be equipped with a cryostat for the vertical test (VT) of a single cell cavity as well as some instruments to process the cavity surface, is still under construction, the team tested the product at KEK and with Peter Kneisel at Jefferson Lab.

RF surfaces were conditioned with CBP, CP, annealing and HPR, but without EP, because the required accelerating electric field (E_acc) is not so high (10 MV/m.). Vertical tests have been performed twice at JLab. The first test was done with additional CP, and the second one was done by baking the inside of the cavity (12 hours @120 °C In-situ). E_acc and Q₀ recorded at those two vertical tests were, as can be seen in the figure, 25.2 MV/m and 9.2 x 10⁹ (@ f = 1499.702 MHz, T = 2K), respectively.

We expect the construction of the PAL SRF test facility to be completed by the end of July 2007. At that time, full me asurements will be available for single cell cavities. After a thorough Higher Order Mode HOM[ec1] study within the facility, the 3rd harmonic cavity will be installed in the PAL storage ring.

As for ILC SRF cavity research, PAL has a close relationship with KEK in developing the 9-cell ICHIRO cavity, which was adopted as one of the alternative cavity shapes by the ILC main linac work group. At present, two dumbbells and one single-cell cavity are under fabrication and will be confirmed at KEK. When the capability is confirmed, between the two laboratories, PAL will proceed to fabricate a complete 9-cell cavity, which will be installed in the KEK STF Phase 1.5 after surface preparation and vertical tests at KEK. Through these steps, PAL will surely be able to improve Korean SRF technology, and continue to contribute to the ILC.

-- PAL ILC Task Force Team
(Won Namkung, Jinhyuk Choi, Younguk Sohn, Jung Yun Huang, Jongsuk Oh, Sungju Park)