| Paper | Title | Other Keywords | Page |
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| TUPTS119 | Status of the ESS Medium Beta Cavities at INFN - LASA | cavity, status, controls, HOM | 2211 |
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| INFN-LASA contributes in-kind to the European Spallation Source ERIC with 36 6-cell cavities for the Medium Beta section of the Superconducting Linac. After having developed the electromagnetic and mechanical models, few prototypes have been produced and tested. Based on this experience, we are now supervisioning the cavity production at the industry, the resonators test at DESY and the delivery to CEA at Saclay. In this paper, we report on the status of the overall INFN-LASA contribution including also document handling, interface data exchange and QA/QC. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS119 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| TUPTS120 | Status of the PIP-II Activities at INFN-LASA | cavity, linac, interface, SRF | 2215 |
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| INFN-LASA joined the international effort for the PIP-II project in Fermilab and it is expected to build the 650 MHz superconducting cavities required by the low-beta section of the 800 MeV front-end proton linac, as recently signed by US DOE and Italian MIUR. After developing the electro-magnetic and mechanical design, INFN-Milano started the prototyping phase by producing five single-cells and two complete 5-cells cavities. In a joint effort with Fermilab the road for the optimal surface treatment for such low-beta resonators has started in order to approach the existing state-of-the-art performances of beta 1 cavities. This paper reports the status of PIP-II activities at INFN-LASA summarizing manufacturing experience and preliminary experimental results. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS120 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB011 | PVD Depostion of Nb3Sn Thin Film on Copper Substrate from an Alloy Nb3Sn Target | cavity, site, interface, HOM | 2818 |
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| In this study we report on the PVD deposition of Nb3Sn on Cu substrates with and without a thick Nb interlayer to produce Cu/Nb/Nb3Sn and Cu/Nb3Sn multilayer structures. The Nb3Sn was sputtered directly from an alloy target at room and elevated temperatures. The dependence of the superconducting properties of the total structure on deposition parameters has been determined. The films have been characterized via SEM, XRD, EDX and SQUID magnetometer measurements. Analysis showed that the composition at both room and elevated temperature was within the desired stoichiometry of 24’25 at%. However, superconductivity was only observed for deposition at elevated temperature or post annealing at 650 °C. The critical temperature was determined to be in the range of 16.8 to 17.4 K. In the case of bilayer deposition, copper segregation from the interface all the way to the surface was observed. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB011 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB089 | Theoretical Analysis of Quasiparticle Overheating, Positive Q-Slope, and Vortex Losses in SRF Cavities | cavity, SRF, electron, experiment | 3020 |
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| The surface resistance of an SRF cavity is an important measure of its performance and utility: lower resistance leads directly to lower cryogenic losses and power consumption. This surface resistance comprises two components, namely the ‘‘BCS resistance’’, which depends strongly on the quasiparticle temperature, and a temperature-independent ‘‘residual resistance’’, which is often dominated by losses due to trapped magnetic vortices. Both components are generally dependent on the RF field strength. Here we present a summary of recent theoretical advances in understanding the microscopic mechanisms of the surface resistance, in particular addressing niobium hydride formation and quasiparticle overheating (using the tools of density functional theory) and discussing issues with existing models of the positive Q-slope, a field-dependent decrease in the BCS resistance, and possible paths for improvement of these models. We also discuss trapped flux losses using ideas from collective weak pinning theory. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB089 | ||
| About • | paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB090 | The Design of Parallel-Feed SC RF Accelerator Structure | cavity, SRF, coupling, alignment | 3024 |
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Funding: Research funded by a SLAC Laboratory-Directed Research and Development award, supported by the U.S. Department of Energy, contract number DE-AC02-76SF00515 Development of superconducting RF (SRF) accelerator technology that enables both higher gradient and higher efficiency is crucial for future machines. While much of the recent R&D focus has been on materials and surface science, our aim is to optimize the cavity geometry to maximize performance with current materials. The recent demonstration of a highly efficient parallel-feed normal-conducting RF structure at SLAC has served as a proof-of-concept. Instead of coupled elliptical cells, the structure employs isolated re-entrant cells. To feed RF power to the cavities, each cell is directly coupled to an integrated manifold. The structure is made in two parts, split along the beam axis, which are then joined. Applied to SRF, simulations suggest such a structure could nearly double the achievable gradient, while reducing cryogenic RF loss by more than half. We are experimentally verifying the concept using an X-band SRF design to be tested at SLAC. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB090 | ||
| About • | paper received ※ 24 May 2019 paper accepted ※ 27 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB110 | Recent Results from Nb3Sn-Coated Single-cell Cavities Combined with Sample Studies at Jefferson Lab | cavity, experiment, SRF, superconductivity | 3066 |
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Funding: Partially authored by Jefferson Science Associates under contract no. DEAC0506OR23177. Supported by Office of High Energy Physics under grants DE-SC-0014475 and DE-SC-0018918. The critical temperature (~ 18 K) and superheating field (~ 425 mT) of Nb3Sn are almost twice that of niobium, thereby promising the higher quality factor and accelerating gradient at any given temperature compared to traditional SRF cavities made of niobium. It can enable higher temperature for cavity operation (4 K Vs. 2 K), resulting in significant reduction in both capital and operating cost for the cryoplant. Several single-cell cavities along with witness samples were coated with Nb3Sn to explore, understand and improve the coating process for betterment of cavity performance. RF measurements of coated cavities combined with material characterization of witness samples were employed to update the coating process. Following some modifications to the existing coating process, we were able to produce Nb3Sn cavity with quality factor ≥ 2.1010 for accelerating gradient up to 15 MV/m at 4 K, without any significant Q-slope. In this article, we will discuss recent results from several Nb3Sn coated single-cell cavities combined with material studies of witness samples. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB110 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB111 | Development of Nb3Sn Multicell Cavity Coatings | cavity, HOM, factory, cryomodule | 3070 |
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Funding: Co-Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics. Nb3Sn films have the potential to augment niobium in SRF cavities. Besides single-cell cavity efforts to improve Nb3Sn films, we are working to replicate single-cell results onto the practical 5-cell CEBAF cavities. High quality factors (1011 at 2.0K and 10zEhNZeHn at 4.3 K) have been measured, but the cavities are typically limited by strong low-field Q-slopes and early quenches. Two of the cavities were selected to be assembled into a ’mock-up’ cavity pair unit, the standard step before installation into a cryomodule. Comparison of test results between VTA and pair test offered the first glimpse into post-processing effects on the cavity performance. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB111 | ||
| About • | paper received ※ 16 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| WEPRB114 | Understanding and Pushing the Limits of Nitrogen Doping | cavity, SRF, experiment, ECR | 3078 |
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| This work will describe Fermilab experiments that focus on the optimization of doping parameters to achieve low sensitivity to trapped magnetic flux while maintaining very high Q characteristic of nitrogen doped cavities and same or higher quench fields. Working partially in the context of LCLS-2 higher energy upgrade, new doping recipes are pursued and have been found to vary the mean free path of the resonator which is related to the sensitivity to trapped magnetic flux. Moreover, a correlation has been found between lighter doping and higher quench fields while maintaining sufficiently low surface resistance. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB114 | ||
| About • | paper received ※ 18 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| THPTS008 | Prospects of Additive Manufacturing for Accelerators | cavity, vacuum, detector, GUI | 4118 |
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Funding: Université Paris-SAclay, Labex P2IO and P2I departement Additive manufacturing allows the production of mechanical components often much faster than traditional manufacturing. Several accelerators components built using additive manufacturing have already been qualified for use in accelerator. A workshop was held in Orsay in December 2018 to discuss the prospects of using additive manufacturing for particle accelerators and particle detectors. We report here on the prospects as far as accelerators are concerned. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS008 | ||
| About • | paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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