| Paper | Title | Page |
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| MOPP132 | Progress Towards Development of an L-Band SC Traveling Wave Accelerating Structure with Feedback | 871 |
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| We describe an ongoing experimental program and progress towards development of a conceptual design for a superconducting traveling wave accelerating structure for the ILC. The accelerating gradient can be significantly improved by the use of an RF feedback system redirecting the accelerating wave that passed through the superconducting traveling wave accelerator (STWA) section back to the input of the accelerating structure. The conceptual design of the SC traveling wave accelerator has been considered by P. Avrakhov et al. [PAC07, pp.2538], where shape optimization, coupler cell design and tuning issues in the feedback loop were presented. The proposed TW structure design gives an overall 24% increase in gradient over the 1 m long standing wave structure and potentially can reach 46% if a longer structure is employed. Experimental investigation of the TW SC structure considers tests of a single cavity having the same shape as the regular cell of the full-sized STWA structure, and the same ratio of the RF fields. The details of the individual parts, joint configurations along with some developments on forming and welding of the proposed cavity shapes are discussed. | ||
| TUPP046 | Tunable Ferroelectric Based Technologies for Accelerator Components | 1646 |
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| Low loss ferroelectric materials can be used as key elements in RF tuning and phase shifting components to provide fast, electronic control. These devices are under development for different accelerator applications in X, Ka and L - frequency bands. The exact design of these devices depends on the electrical parameters of the particular ferroelectric material to be used- its dielectric constant, loss tangent and tunability. BST based ferroelectric-oxide compounds have been found to be suitable materials for a fast electrically-controlled tuner for BNL and for high-power fast RF phase shifters to be used for SNS vector modulation applications. We present recent results on the development of BST based ferroelectric compositions synthesized for use in high power technology components. The BST(M) ferroelectrics have been tested using a transverse dc bias field. The tunability factor vs. dc field magnitude has been evaluated and the feasibility of transverse bias tuning for ferroelectric based accelerator components has been demonstrated. | ||
| MOPP029 | The First Measurement of Low-loss 9-cell Cavity in a Cryomodule at STF | 610 |
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| We are constructing Superconducting RF Test Facility (STF) at KEK for the R&D of International Linear Collider (ILC) accelerator. In the beginning of year 2008, we installed one high-gradient Low-Loss (LL) type 9-cell cavity into a cryomodule at STF, where we assembled an input coupler and peripherals with the cavity in a clean room, and the assembled cavity packages were dressed with thermal shields and installed into a cryomodule. At the room-temperature, we performed the processing of capacitive-coupling input-coupler upto the RF power of 250 kW. At the temperature of 4 K, we measured the loaded Q of the cavity and the tuner was tested. At the temperature of 2 K, high-power RF was supplied from a klystron to the cavity and the performance of the cavity packeage was tested. This article presents the results of the first test of the Low-Loss (LL) 9-cell cavity package at 2 K in a cryomodule. | ||
| MOPP093 | Fast L-band Waveguide Phase Shifter | 769 |
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| During the operation of accelerators it is often important to rapidly change the parameters of the RF system, such as cavity resonant frequency, coupling, or electrical length. For this purpose a fast L-band planar phase shifter has been designed, that has advantages compared to the coaxial scheme considered before by the authors (EPAC 06). The phase shifter is based on a new ferroelectric ceramic, whose permittivity changes with application of an external voltage. The switching time depends on only the external HV circuit and can by less than a few microseconds. The conceptual design and electrical parameters of the new phase shifter are presented, as are first results of low power measurements on a 1/3 model. | ||
| WEPP133 | High-gradient Multi-mode Two-beam Accelerating Structure | 2806 |
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A new accelerating structure which is aimed to provide gradient >150 MV/m for next generation of multi-TeV linear colliders is suggested. The structure is based on periodic system of quasi-optical cavities*. Each of these cavities is excited in several equidistantly-spaced eigen modes by the drive beam in such a way that the RF fields reach peak values only during the short time intervals when an accelerating bunch is resident in the cavities, thus exposing the cavity surfaces to strong fields for only a small fraction of time. This feature is expected to raise the breakdown and pulse heating thresholds. The proposed structure embodies most of additional attractive properties: the cavity is an all metallic structure, no transfer or coupling structures are needed between the drive and acceleration channels, the cavity fields are symmetric around the axes of the drive beam and the accelerated beam, the cavity can exhibit high transformer ratio. Calculations of single quasi-optical rectangular cavity with parameters of drive and accelerating beams close to ones adopted for the CLIC project show that high gradient as well as high efficiency are achievable.
*S. V. Kuzikov et al. "Quasi-optical accelerating structure operated with a superposition of synchronized modes," Conf. Digest of Joint 32nd IRMMW Conf., Cardiff, UK, 2007, Vol.2, p.797-798. |