| Paper | Title | Page |
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| SUPFDV015 | Preliminary Results from Magnetic Field Scanning System for a Single-Cell Niobium Cavity | 96 |
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| One of the building blocks of modern particle accelerators is superconducting radiofrequency (SRF) cavities. Niobium is the material of choice to build such cavities, which operate at liquid helium temperature (2 - 4 K) and have some of the highest quality factors found in Nature. There are several sources of residual losses, one of them is trapped magnetic flux, which limits the quality factor in SRF cavities. The flux trapping mechanism depends on different niobium surface preparations and cool-down conditions. Suitable diagnostic tools are not yet available to study the effects of such conditions on magnetic flux trapping. A magnetic field scanning system (MFSS) for SRF cavities using Hall probes and Fluxgate magnetometer has been designed, built, and is commissioned to measure the local magnetic field trapped in 1.3 GHz single-cell SRF cavities at 4 K. In this contribution, we will present the preliminary results from MFSS for a single cell niobium cavity. | ||
| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV015 | |
| About • | Received ※ 21 June 2021 — Revised ※ 13 August 2021 — Accepted ※ 08 November 2021 — Issue date ※ 27 April 2022 | |
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| SUPTEV001 | Magnetic Field Penetration Technique to Study High Field Shielding of Multilayered Superconductors | 112 |
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Funding: NSF Grants PHY-1734075 and PHY-1416051, and DOE Awards DE-SC0010081 and DE-SC0019399 The SIS structure which consists of alternative thin layers of superconductors and insulators on a bulk niobium has been proposed to shield niobium cavity surface from high magnetic field and hence increase the accelerating gradient. The study of the behavior of multilayer super-conductors in an external magnetic field is essential to optimize their SRF performance. In this work we report the development of a simple and efficient technique to measure penetration of magnetic field into bulk, thin film and multilayer superconductors. Experimental setup contains a small superconducting solenoid which can produce a parallel surface magnetic field up to 0.5 T and Hall probes to detect penetrated magnetic field across the superconducting sample. This system was calibrated and used to study the effect of niobium sample thickness on the field of full magnetic flux penetration. We determined the optimum thickness of the niobium substrate to fabricate the multilayer structure for the measurements in our setup. This technique was used to measure penetration fields of Nb3Sn thin films and Nb3Sn/Al2O3 multi-layers deposited on Al2O3 wafers. |
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| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV001 | |
| About • | Received ※ 22 June 2021 — Revised ※ 15 August 2021 — Accepted ※ 20 September 2021 — Issue date ※ 28 April 2022 | |
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| SUPTEV016 | Samples for 3rd Harmonic Magnetometry Assessment of NbTiN-Based SIS Structures | 164 |
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Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. NSF Grants PHY-1734075 and PHY-1416051, and DOE Awards DE-SC0010081 and DE-SC0019399. In the quest for alternative superconducting materials to bring accelerator cavity performance beyond the bulk niobium (Nb) intrinsic limits, a promising concept uses superconductor-insulator-superconductor (SIS) thin film structures that allows magnetic flux shielding in accelerator cavities to higher fields [1]. Candidate materials for such structures are NbTiN as the superconductor and AlN as the insulator. We have demonstrated high quality NbTiN and AlN deposited by reactive DC magnetron sputtering (DCMS), both for individual layers and multilayers. Interface quality has been assessed for bilayer stacks with 250 nm NbTiN layers and AlN thicknesses from 30 nm down to1 nm. These SIS structures show continued sharp interfaces with total average roughness under 2 nm. The Hfp enhancement of the films will be examined with a 3rd harmonic magnetometry. The system is being designed and built in a continuing collaboration with CEA Saclay. It can measure 25 to 50 mm samples on a temperature controlled stage. This contribution presents an overview of the design of the 3rd harmonic magnetometer and the material properties assessment of standalone films and multilayer nanostructures. [1] A. Gurevich, Applied Physics Letters, vol. 88, p. 012511, 2006. |
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| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV016 | |
| About • | Received ※ 22 June 2021 — Accepted ※ 10 November 2021 — Issue date ※ 16 May 2022 | |
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| WEPCAV014 | HOM Damper Design for BNL EIC 197 MHz Crab Cavity | 624 |
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Funding: The work is supported by by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. The interaction region (IR) crab cavity system is a special RF system to compensate the loss of luminosity due to a 25 mrad crossing angle at the interaction point (IP) for BNL EIC. There will be six crab cavities, with four 197 MHz crab cavities and two 394 MHz crab cavities, installed on each side of the IP in the proton/ion ring, and one 394 MHz crab cavity on each side of the IP in the electron ring. Both rings share identical 394 MHz crab cavity design to minimize the cost and risk in designing a new RF system, and it will be scaled from 197 MHz crab cavity. In this paper, the HOM damper design for 197 MHz crab cavity is introduced. |
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| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPCAV014 | |
| About • | Received ※ 22 June 2021 — Revised ※ 17 October 2021 — Accepted ※ 17 December 2021 — Issue date ※ 07 April 2022 | |
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| SUPTEV011 | Nb3Sn Coating of Twin Axis Cavity for SRF Applications | 146 |
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| The twin axis cavity with two identical accelerating beams has been proposed for energy recovery linac (ERL) applications. Nb3Sn is a superconducting material with a higher critical temperature and a higher critical field as compared to Nb, which promises a lower operating cost due to higher quality factors. Two niobium twin axis cavities were fabricated at JLab and were proposed to be coated with Nb3Sn. Due to their more complex geometry, the typical coating process used for basic elliptical cavi-ties needs to be improved to coat these cavities. This development advances the current coating system at JLab for coating complex cavities. Two twin axis cavities were coated recently for the first time. This contribution dis-cusses initial results from coating of twin axis cavities, RF testing and witness sample analysis with an overview of the current challenges towards high performance Nb3Sn coated twin axis cavities. | ||
| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV011 | |
| About • | Received ※ 22 June 2021 — Revised ※ 19 December 2021 — Accepted ※ 21 February 2022 — Issue date ※ 01 April 2022 | |
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