Three-cell traveling wave superconducting test structure

Use of a superconducting traveling wave accelerating (STWA) structure with a small phase advance per cell rather than a standing wave structure may provide a significant increase of the accelerating gradient in the ILC linac. For the same surface electric and magnetic fields the STWA achieves an accelerating gradient 1.2 larger than TESLA-like standing wave cavities. The STWA allows also longer acceleration cavities, reducing the number of gaps between them. However, the STWA structure requires a SC feedback waveguide to return the few hundreds of MW of circulating RF power from the structure output to the structure input. A test single-cell cavity with feedback was designed, manufactured and successfully tested demonstrating the possibility of a proper processing to achieve a high accelerating gradient. These results open way to take the next step of the TW SC cavity development: to build and test a traveling-wave three-cell cavity with a feedback waveguide. The latest results of the single-cell cavity tests are discussed as well as the design of the test 3-cell TW cavity.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 28 Mar - 1 Apr 2011: New York, US

Coupling interaction between the power coupler and the third harmonic superconducting cavity

Fermilab has developed a third harmonic superconducting cavity operating at the frequency of 3.9 GHz to improve the beam performance for the FLASH user facility at DESY. It is interesting to investigate the coupling interaction between the SRF cavity and the power coupler with or without beam loading. The coupling of the power coupler to the cavity needs to be determined to minimize the power consumption and guarantee the best performance for a given beam current. In this paper, we build and analyze an equivalent circuit model containing a series of lumped elements to represent the resonant system. An analytic solution of the required power from the generator as a function of the system parameters has also been given based on a vector diagram

Study of adaptive alignment as beam based alignment in ILC Main Linac in the presence of ground motion

In this work we present simulation results on the effect of ground motion on the main linac performance of the proposed International Linear Collider (ILC), and then use adaptive alignment (AA) technique to correct it. The adaptive alignment technique is investigated for the ILC main linac and its limitations are studied. Then ground motion studies are performed using the simulation program LIAR and the beneficial effects of implementing AA algorithm are further discussed

RF thermal and new cold part design studies on TTF-III input coupler for Project-X

RF power coupler is one of the key components in superconducting (SC) linac. It provides RF power to the SC cavity and interconnects different temperature layers (1.8K, 4.2K, 70K and 300K). TTF-III coupler is one of the most promising candidates for the High Energy (HE) linac of Project X, but it cannot meet the average power requirements because of the relatively high temperature rise on the warm inner conductor, some design modifications will be required. In this paper, we describe our simulation studies on the copper coating thickness on the warm inner conductor with RRR value of 10 and 100. Our purpose is to rebalance the dynamic and static loads, and finally lower the temperature rise along the warm inner conductor. In addition, to get stronger coupling, better power handling and less multipacting probability, one new cold part design was proposed using 60mm coaxial line; the corresponding multipacting simulation studies have also been investigated.Comment: 5 pages, 12 figures. Submitted to Chinese Physics C (Formerly High Energy Physics and Nuclear Physics