Conveners
Flux expulsion efficiency: Part 1
- Julia Koeszegi (HZB)
- Kensei Umemori (KEK)
- David Longuevergne (IPNO)
Flux expulsion efficiency: Part 2
- David Longuevergne (IPNO)
- Kensei Umemori (KEK)
- Julia Koeszegi (HZB)
Flux expulsion efficiency: Part 3
- David Longuevergne (IPNO)
- Kensei Umemori (KEK)
- Julia Koeszegi (HZB)
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Sam Posen (Fermilab)08/11/2018, 11:25
This presentation will give an overview of magnetic flux expulsion. This will include a general description of the phenomenon and how it is fits into the larger picture of Q0 degradation due to trapped flux. A historical overview will be presented, focusing particularly on recent developments in the understanding of flux expulsion. The importance of this parameter to achieve high Q0 will be...
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Rongli Geng (Jefferson Lab), Shichun Huang (IMP)08/11/2018, 11:50
Presently, three different techniques are used for deducing the trapped flux of SRF cavities quantitatively based on measurements of flux expulsion at the phase transition moment during the cavity cool-down process. It is still an open question as to whether these techniques give results that are consistent to each other. In this talk, we introduce two formulae that allow direct cross checking...
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Julia-Marie Köszegi (HZB)08/11/2018, 12:05
This presentation will discuss techniques used for magnetic field measurement in SRF cavities as well as samples. Advances, challenges and future prospects will be given.
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08/11/2018, 12:20
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Martina Martinello (Fermilab - IIT)08/11/2018, 14:00
The efficiency of flux expulsion during the cavity superconducting transition is affected significantly by the properties of the material used to fabricate the cavity itself. Significant variability is indeed observed when comparing cavities fabricated with material coming from different vendors. Here we present results from a recent study in which the microscopic properties of different...
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Dr Kensei Umemori (KEK)08/11/2018, 14:10
We started EBSD measurements, which can be observed while changing temperature of Nb samples in a chamber. We expect measurements on grain orientation, stress and dislocation can give us important information to understand pinning center and flux expulsion
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Sam Posen (Fermilab)08/11/2018, 14:20
In this presentation, a brief update will be presented on a study in which flux expulsion is measured in two large grain cavities, one of which was heavily deformed during the manufacturing process, and one of which went through the standard fabrication steps. The most recent measurements were performed after high temperature furnace treatment at 800 C
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08/11/2018, 14:30
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Anton Evgeniev Ivanov (CERN)08/11/2018, 14:40
Initial investigations on magnetic flux expulsion in the CERN vertical test cryostats are discussed, with measurements taken on a bulk Nb 704 MHz 5-cell elliptical cavity. Cool down procedure is assessed in terms of both magnetic field flux expulsion and thermal currents, and the implication to RF performance is discussed.
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In addition, mapping of magnetic field inside the cryostat is... -
Kensei Umemori (KEK)08/11/2018, 14:50
In each VT for QWR at RIKEN, we measure the vertical magnetic field at the upper part of the cavity. We report the obtained data, mainly at a moment the cavity shifts from NC to SC, and from SC to NC.
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08/11/2018, 15:00
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Sam Posen (Fermilab)08/11/2018, 15:10
In this presentation, I will give an overview of the substantial influence of magnetic flux expulsion on the performance of production cavities for LCLS-II, focusing particularly on their performance in cryomodule tests. Strong correlations are observed between Q0 and the temperature at which vacuum furnace treatment occurred.
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Ari Palczewski (Thomas Jefferson National Accelerator Facility)08/11/2018, 15:20
The SLAC National Accelerator Laboratory is currently constructing a major upgrade to its accelerator, the Linac Coherent Light Source II (LCLS-II). Several Department of Energy national laboratories, including the Thomas Jefferson National Accelerator Facility (JLab) and Fermi National Accelerator Laboratory (FNAL), are participating in this project.The 1.3-GHz cryomodules for this project...
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Detlef Reschke (DESY), Joern Schaffran (Deutsches Elektronen-Synchrotron (DE)), Marc Wenskat (Deutsches Elektronen-Synchrotron DESY)08/11/2018, 15:30
The present status of the measurements and analysis wrt. the residual static magnetic field in the vertical test cryostats and the used test inserts at DESY are presented. First commissiong tests to determine the flux expulsion of 120C electropolished cavities have been done. The more than 1200 vertical tests done on the European XFEL series cavity production gave no indication about a cavity...
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08/11/2018, 15:40
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Felix Kramer (HZB)08/11/2018, 16:10
The absolute calibration of the AMR sensors used in our flux expulsion experiment will be presented. Furthermore the latest results obtained with the 3D magnetic field mapping system, investigating the flux expulsion efficiency of a 1.3 GHz TESLA-type single cell cavity will be discussed.
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David Longuevergne (IPNO)08/11/2018, 16:20
Measurements of magnetic sensitivity to trapped flux on several type of cavity geometries have been performed at IPNO showing a clear geometrical effect. Magnetic sensitivity is dependent on the cavity geometry and on the residual magnetic field orientation. A presentation of experimental data will be done. These will be as well compared to the theoretical magnetic sensitivities calculated...
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08/11/2018, 16:30
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Prof. Damian Hampshire (Durham University)08/11/2018, 16:40
This talk will provide a short review of the different pinning mechanisms that operate in useful superconductors. We will consider both high kappa superconducting materials used for high field magnets and low kappa materials used for SRF. We will visualise the different pinning processes that operate and discuss the theoretical descriptions for such processes. Finally we will identify the...
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08/11/2018, 17:05