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TUPB104 |
First Full Cryogenic Test of the SRF Thin Film Test Cavity |
644 |
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- R. Valizadeh, L. Bizel-Bizellot, P. Goudket, L. Gurran, O.B. Malyshev, N. Pattalwar, S.M. Pattalwar
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
- G. Burt, L. Gurran
Lancaster University, Lancaster, United Kingdom
- G. Burt, P. Goudket, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom
- L. Gurran
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
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A test cavity that uses RF chokes, rather than a physical seal, to contain the field is a promising method of SRF sample testing, especially in thin films research where the rate of sample production far outstrips that of full SRF characterisation. Having the sample and cavity physically separate reduces the complexity involved in changing samples - major causes of low throughput rate and high running costs for other test cavities - and also allows direct measurement of the RF power dissipated in the sample via power calorimetry. Choked test cavities operating at 7.8 GHz with three RF chokes have been designed and tested at Daresbury Laboratory. As part of the commissioning of this system, we performed the first full SRF test with a bulk Nb sample and we verified that the system would perform as required for future superconducting thin film sample tests.
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DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-SRF2017-TUPB104
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MOPB040 |
ESS High-beta Cavity Test Preparations at Daresbury Laboratory |
137 |
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- P.A. Smith, L. Bizel-Bizellot, K.D. Dumbell, M. Ellis, P. Goudket, A.J. Moss, E.F. Palade, S.M. Pattalwar, M.D. Pendleton, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
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Science and Technology Facility Council is responsible for supplying, and testing 84 High beta elliptical SRF cavities, as part of the UK In Kind Contribution to the European Spallation Source (ESS). The High-β=0.86, cavities have been designed by CEA- Saclay and are a five cell Niobium cavity operating at 704.42 MHz. They are required to provide an accelerating gradient of 19.9 MV/m at an unloaded Q of 5x109. Preparations are underway to upgrade the cryogenic and RF facilities at Daresbury laboratory prior to the arrival of the first cavities. As part of these arrangements, a niobium coaxial resonator has been manufactured, to validate the test facility. The design considerations, for the coaxial resonator are presented, along with preliminary results. The RF measurement system to perform the cavity conditioning and testing is also presented.
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DOI • |
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※ https://doi.org/10.18429/JACoW-SRF2017-MOPB040
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TUPB060 |
Innovative Cryogenic Test Facility for Testing SRF Cavity Series Production |
520 |
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- L. Bizel-Bizellot, M. Ellis, S.M. Pattalwar, M.D. Pendleton, P.A. Smith, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
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Testing SRF cavities in a vertical cryostat is the first step in qualifying the performance of SRF cavities before being integrated into a cryomodule. The European Spallation Source (ESS) requires 84 high-beta 5 cells, 704 MHz cavities which will be manufactured and qualified for their RF performance in a vertical cryostat at Science and Technology Facility Council (STFC) Daresbury Laboratory (United-kingdom). Taking a conventional approach each vertical test would require a large cryostat demanding more than 7000 litres of liquid helium per test for testing 3 cavities simultaneously. In order to reduce the overall operating cost, we plan to develop an alternative method to divide the liquid helium consumption by 5 by filling liquid helium only in each individual helium vessels enclosing each cavity placed horizontally in the cryostat. Therefore the test is performed in more realistic conditions such as in a cryomodule and reduces the operating time. This also reduces the mass flow-rate to be handled by a factor 10, leading to 2 g/s, thus reducing the size of the associated components such as the 2 K pumps, the safety device, the valves and transfer lines.
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DOI • |
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※ https://doi.org/10.18429/JACoW-SRF2017-TUPB060
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TUPB100 |
Determining BCP Etch Rate and Uniformity in High Luminosity LHC Crab Cavities |
635 |
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- T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
- G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
- R. Calaga, O. Capatina, L.M.A. Ferreira, R. Leuxe
CERN, Geneva, Switzerland
- T.J. Jones, J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
- S.M. Pattalwar
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
- S. Verdú-Andrés, B. P. Xiao
BNL, Upton, Long Island, New York, USA
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The compact SRF Crab Cavities required for HL-LHC have complex geometries making prediction of average and local BCP etch rates a difficult task. This paper describes a series of experiments and simulations used to determine the etch uniformity and rate within these structures. An initial experiment was conducted to determine the correlation between etch rate and flow rate in a Nb tube. These results were then incorporated into Computational Fluid Dynamics simulations of acid flow in the Double Quarter Wave (DQW) cavity to predict etch rates across the surface and allow optimisation of the BCP setup. There were several important findings from the work; one of which is that the flow rate in the relatively large body of the cavity is predominantly driven by natural convection due to the exothermic reaction. During BCP processing of the DQW cavity a significant difference in etching was observed between upper and lower horizontal surfaces which was mitigated by etching in several orientations. Two DQW cavities manufactured by CERN have received a heavy BCP of 200μm followed by 2 light BCPs of 30μm each with subsequent vertical cold tests showing performance exceeding specification.
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DOI • |
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※ https://doi.org/10.18429/JACoW-SRF2017-TUPB100
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TUPB103 |
DC Magnetism of Niobium Thin Films |
640 |
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- S. Wilde, B. Chesca
Loughborough University, Loughborough, Leicestershire, United Kingdom
- A.N. Hannah, O.B. Malyshev, N. Pattalwar, S.M. Pattalwar, B.S. Sian, R. Valizadeh, S. Wilde
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
- B.S. Sian
UMAN, Manchester, United Kingdom
- G.B.G. Stenning
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
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Niobium thin films were deposited onto a-plane sapphire with varying kinetic energy and varying substrate temperature. There were no consistent trends which related the particle energy or substrate temperature to RRR. The sample which displayed the largest RRR of 229 was then compared to both a thin film deposited with similar conditions onto copper substrate and to bulk niobium. DC magnetometry measurements suggest that the mechanism of flux entry into thin film niobium and bulk niobium may vary due to differences in the volumes of both defects and impurities located within the grains. Results also suggest that magnetic flux may penetrate thin films at small fields due to the sample geometry.
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DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-SRF2017-TUPB103
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