| Paper | Title | Page |
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| WEPMS087 | Conceptual Design of an L-Band Recirculating Superconducting Traveling Wave Accelerating Structure | 2538 |
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Funding: This research is supported by the US Department of Energy We describe a conceptual design for a superconducting traveling wave accelerator for the ILC. The RF feedback system plus phase shifter can redirect the accelerating wave that passed through the STWA section back to the input of the accelerating structure. In this paper, the STWA cell shape optimization, coupler cell design and rat race ring coupler in the feedback loop are presented. The STWA cell shape is similar to the LL cavity with a 60 mm disk diameter. A 9-cell STWA operates at the mode with group velocity as low as 0.0106 c. Both the ratio of peak electric field and magnetic field to the axial electric field are smaller than in the TESLA 9-cell cavity. The STWA structure has more cells per unit length than a TESLA structure but provides an accelerating gradient higher than a TESLA structure, consequently reducing the cost. The designed rat race directional coupler with four ports has ?3 dB direct coupling coefficients, 16.5 MHz bandwidth between ?30 dB isolations and 1.1 MHz bandwidth between ?30 dB reflection coefficients. Effects of the mechanical tolerances are also discussed. |
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| WEPMN066 | Progress Towards Development of a Superconducting Traveling Wave Accelerating Structure | 2182 |
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| In the ILC project the required accelerating gradient is higher than 35 MeV/m. For current technology the maximum acceleration gradient in SC structures is limited mainly by the value of the surface RF magnetic field. In order to increase the gradient, the RF magnetic field is distributed homogeneously over the cavity surface (low-loss structure), and coupling to the beam is improved by introducing aperture ?noses? (re-entrant structure). These features allow gradients in excess of 50 MeV/m to be obtained for a singe-cell cavity. Further improvement of the coupling to the beam may be achieved by using a TW SC structure with small phase advance per cell. Calculations show that an additional gradient increase by up to 40% is possible if a p/2 TW SC structure is employed. However, a TW SC structure requires a SC feedback waveguide to return the few GW of circulating RF power from the structure output back to the structure input. We describe a single-cell test TW SC structure with a feedback waveguide. The test cavity is designed to demonstrate the possibility of achieving a significantly higher gradient than existing SC structures. | ||
| THPMS072 | Superconducting Traveling Wave Ring with High Gradient Accelerating Section | 3148 |
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| Considerable gain of a superconducting linac accelerating gradient provides using of a traveling wave structure instead of a standing wave accelerating section. Preservation of the superconducting structure advantages requires to put the TW accelerating section into a superconducting traveling wave ring (STWR). We discuss two variants of the STWR with one and two feeding couplers. The STWR application allows to increase the superconducting section accelerating gradient up to ~50 MV/m and essentially reduce the price of the section tuning system. |