Masashi Yamanaka

Fabrication and Evaluation of Superconducting Single-Cell Cavities Manufactured Using Various Materials and Methods

Six cavities of the same type (TESLA-like shape) made from six different niobium sources or types were produced at KEK using various materials and fabrication methods. Throughout these sequential in-house fabrications, comparisons of the properties of the various materials for use in superconducting radio-frequency cavities were conducted. The advantages and disadvantages of these properties, together with different fabrication methods, were examined. The cavities were fabricated primarily using existing facilities within KEK to control the fabrication quality. Vertical tests to evaluate single-cell cavity performances were conducted at the Superconducting RF Test Facility in KEK. The technical details of each fabrication method and the obtained high-gradient test results are described and discussed.

Ingot Nb based SRF technology for the International Linear Collider

The International Linear Collider (ILC) is anticipated to be built as the next energy-frontier electron-positron colliding accelerator with a global effort in particle physics. Niobium based Superconducting Radio-Frequency (SRF) technology is required to provide beam-accelerating structure with elliptical cavity strings to linearly accelerate the electron and positron beams up to 250 GeV and to realize a center-of-mass energy of 500 GeV in collisions. The accelerator design and R&D efforts progressed, and the ILC Technical Design Report (ILC-TDR) was published in 2013. Niobium will take a critical role to generate electric field gradient with a frequency of 1.3 GHz, for accelerating the beam with the best efficiency, in energy balance, using RF superconductivity. This paper discusses a technical approach to provide Nb material (ingot) and thin disks for producing the elliptical cavity structure, with direct slicing from Nb ingot having sufficiently optimized purity and residual resistance ration (RRR) nec...