| Paper | Title | Page |
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| TUP027 | Tests of Superconducting Materials in a High-Q RF Cavity | 305 |
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Superconducting rf is of increasing importance in particle accelerators. We have developed a resonant copper cavity with high quality factor and an interchangeable wall for testing superconducting materials.* A compact TE 01 mode launcher excites the azimuthally symmetric cavity mode, which allows a gap at the detachable wall and is free of surface electric fields that could cause field emission, multipactor, and rf breakdown. The shape of the cavity is tailored to focus magnetic field on the test wall, formed by a material sample. Working at X-band allows us to test small samples in a small available dewar, as well as taking advantage of available high power. We present results of cryogenic experiments conducted with this cavity. Low power tests allow characterization of the cavity parameters and their variation with temperature; high power tests allow determination of field limits for the superconducting samples. We describe our signal processing and analysis. Our experiments begin with reactor-grade niobium, followed by MgB2.
*C. Nantista et al., “Test Bed for Superconducting Materials,” presented at the 2005 Particle Accelerator Conference, Knoxville, Tennessee, May 16-20, 2005; SLAC-PUB-11246. |
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| TUP032 | Comparison of SNS Superconducting Cavity Calibration Methods | 315 |
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| Three different methods have been used to calibrate the SNS superconducting cavity RF field amplitude. Two are beam based and the other strictly RF based. One beam based method uses time-of-flight signature matching (phase scan method), and the other uses the beam-cavity interaction itself (drifting beam method). Both of these methods can be used to precisely calibrate the pickup probe of a SC cavity and determine the synchronous phase. The initial comparisons of the beam based techniques at SNS did not achieve the desired precision of 1% due to the influence of calibration errors, noise and coherent interfaces in the system. To date the beam-based SC cavity pickup probe calibrations agree within approximately 4%, comparable to the conventional RF calibrations. | ||
| THP081 | Study on Fault Scenarios of Coaxial Type HOM Couplers in SRF Cavities | 770 |
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| Coaxial type couplers are adopted in many superconducting radio-frequency (SRF) cavities to suppress higher order modes for beam dynamics and cryogenic loads issues. HERA (Hadron-Electron Ring Accelerator) and TTF (Tesla Test Facility) are equipped with this type coupler and showed successful performances. It is, however, under suspicion that a limitation or a fault could be initiated from this type of coupler at certain combinations between cavity operating conditions and engineering designs of the coupler. Some possible scenarios are summarized and also some observations in the SNS (Spallation Neutron Source) SRF cavities are also reported. | ||
| FR2002 | 2K or Not 2K | 828 |
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| Particle accelerators based on superconducting cavity technology operate mostly in CW mode and require the highest possible Qo and the lowest possible operating temperature, compatibly with the overall efficiency of the cryogenic plant. However, for pulsed accelerators conditions and parameters can exist, by which optimal performance can be reached at intermediate temperatures, without the need of operating below the helium λ point. In the design of future facilities, this fact may lead to decreased facility costs and to simplified operation. The parameter space and the applicability of these criteria will be presented. |