| Paper | Title | Page |
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| MOPMB026 | Development of Transformative Cavity Processing - Superiority of Electropolishing on High Gradient Performance over Buffered Chemical Polishing at Low Frequency (322 MHz) | 145 |
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Funding: The work is supported by DOE Awards DE-SC0022994. A DOE grant R&D titled ¿Development of Transformative Preparation Technology to Push up High Q/G Performance of FRIB Spare HWR Cryomodule Cavities¿ is ongoing at FRIB. This R&D is for 2 years since September 2022. This project proposes four objectives: 1) Superiority on high gradient performance of electropolishing (EP) over buffered chemical polishing at low frequency (322 MHz), 2) High Qo performance by the local magnetic shield, 3) Development of HFQS-free BCP and, 4) Wet N-doping method. This paper will report the result of first object, and a local magnetic shield design and simulation to reduce the residual magnetic field < 0.1 mG in the vertical test Dewar, for the object 2. |
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| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB026 | |
| About • | Received ※ 14 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 08 July 2023 | |
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| TUPTB016 | Summary of the FRIB Electropolishing Facility Design and Commissioning, Cavity Processing, and Cavity Test Results | 419 |
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Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the FRIB, which is a DOE Office of Science User Facility, under Award Number DE-SC0000661. Recently, a new Electropolishing (EP) facility was con-structed and commissioned at the Facility for Rare Isotope Beam (FRIB) with the purpose of supporting advanced surface processing techniques for SRF R&D activities. The FRIB production cavities opted for a Buffered Chemical Polish (BCP) method due to its cost effectiveness and was supported by successful outcomes in other facilities with low beta cavities in a similar frequency range. All 324 cavities used in FRIB Linac were processed in-house at MSU using BCP and exhibited satisfactory performance during testing. As part of the FRIB energy upgrade R&D, 5-cell 644 MHz elliptical resonators will be employed, desiring the use of EP and advanced techniques such as nitrogen doping and medium-T baking. The EP facility is designed to accommodate all types of cavities used in FRIB and possesses the capability for performing EP at low temperatures. Here we report the details of design and commissioning of the EP facility, highlights of encountered issues and subsequent improvements, and preliminary results from vertical tests conducted on the cavities. |
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| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB016 | |
| About • | Received ※ 15 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 14 July 2023 | |
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| TUPTB069 | Design and Tests of a Cathode Stalk for the LCLS-II-HE Low Emittance Injector SRF Gun | 589 |
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| A SRF gun can operate CW with a high gradient and ultra-low vacuum for high-quantum efficiency, low MTE photocathodes, useful features for delivery of high-brightness, high-repetition-rate beams. For these reasons, an SRF gun based photoinjector was chosen for a proposed Low Emittance Injector addition to the LCLS-II-HE facility, which will operate CW with bunch rates up to 1 MHz. For this injector, a prototype 185.7 MHz QWR gun is being developed in a collaborative effort among FRIB, HZDR, ANL and SLAC, with the goal of achieving a photocathode gradient of at least 30 MV/m. The photocathode is held by a coaxial fixture (cathode stalk) for thermal isolation from the cavity body. The system must allow for precise alignment of the photocathode, particle-free photocathode exchange, cryogenic (55-70 K) or warm (273-300 K) photocathode operating temperatures, and DC biasing to inhibit multipacting. A prototype cathode stalk has been built and bench tests are underway to validate the design. Measurements include RF power dissipation, DC bias hold-off, multipacting suppression and heat transfer effectiveness. This paper describes the cathode stalk design and the test results. | ||
| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB069 | |
| About • | Received ※ 03 July 2023 — Revised ※ 27 July 2023 — Accepted ※ 19 August 2023 — Issue date ※ 20 August 2023 | |
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