Paper | Title | Other Keywords | Page |
---|---|---|---|
SUPTEV006 | Commissioning of a Calibration Device for Second Sound Quench Detection | cavity, MMI, SRF, superconductivity | 124 |
|
|||
An important part of research and development in the field of superconducting radio frequency technology is the quench detection since these breakdowns of superconductivity often limit the cavity performance. Although the second sound based quench detection is widely used, only few studies dealing with its systematic uncertainties exist. Hence, the vertical test stands at the cavity test facility of DESY were extended by calibration device prototypes in order to estimate the accuracy of this method. For the first time at DESY, artificial signals have been generated and reconstructed by heating power film resistors. These second sound signals are determined using noise canceling algorithms and the existing reconstruction software. To evaluate the reconstructed positions, the absolute distance between reconstructed and true coordinates is calculated. Thus, a first uncertainty map of the cavity surface is created to quantify the reconstruction results of actual cavity quenches including systematic effects of the quench positioning like the varying sensor coverage around the cavity. | |||
DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV006 | ||
About • | Received ※ 20 June 2021 — Revised ※ 09 July 2021 — Accepted ※ 20 November 2021 — Issue date ※ 30 April 2022 | ||
Cite • | reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml) | ||
MOPCAV002 | Shape Evolution of C75 Large-Grain Niobium Half-Cells During Cavity Fabrication | cavity, laser, FEM, cryomodule | 255 |
|
|||
Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. The largely anisotropic deformation of large-grain Nb discs during deep drawing into half-cells poses a challenge for achieving a desired shape accuracy. Two 5-cell cavities for the C75 CEBAF cryomodule rework program have been fabricated at Jefferson Lab from large-grain Nb discs directly sliced from an ingot. The shape of the inner surface of eight half-cells has been inspected using a FARO Edge laser scanner during the fabrication process and compared to the reference shape. On average, approximately 63% of the half-cell inner surface was found to be within 0.1 mm of the reference shape and ~90% to be within 0.2 mm, after the final equator machining. Several 5-cell C75 cavities have also been fabricated at Research Instruments, Germany, and measurements of the shape accuracy using a Zeiss 3D coordinate measuring machine gave similar results. One half-cell was measured both at Research Instruments and Jefferson Lab for comparison. |
|||
DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPCAV002 | ||
About • | Received ※ 21 June 2021 — Accepted ※ 21 August 2021 — Issue date ※ 11 February 2022 | ||
Cite • | reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml) | ||
TUPTEV004 | In Situ Plasma Processing of Superconducting Cavities at Jefferson Lab | cavity, cryomodule, plasma, HOM | 485 |
|
|||
Funding: Funding provided by SC Nuclear Physics Program through DOE SC Lab funding announcement Lab-20-2310 Jefferson Lab began a plasma processing program starting in the spring of 2019. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the secondary emission coefficient. Unlike helium processing which relies on ion bombardment of the field emitters, plasma processing uses free oxygen produced in the plasma to break down the hydrocarbons on the surface of the cavity. The residuals of the hydrocarbons in the form of water, carbon monoxide and carbon dioxide are removed from the cryomodule as part of the process gas flow. The initial focus of the effort is processing C100 cavities by injecting RF power into the HOM coupler ports. We will then start investigating processing of C50 cavities by introducing RF into the fundamental power coupler. The plan is to start processing cryomodules in the CEBAF tunnel in the mid-term future, with a goal of improving the operational gradients and the energy margin of the linacs. This work will describe the systems and methods used at JLAB for processing cavities using an argon oxygen gas mixture. Before and after plasma processing results will also be presented. |
|||
DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPTEV004 | ||
About • | Received ※ 21 June 2021 — Accepted ※ 05 October 2021 — Issue date ※ 02 May 2022 | ||
Cite • | reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml) | ||