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| Title | Prediction of Severe Electron Loading of High-gradient Accelerating Structures based on Field Emission Measurements of Nb and Cu Samples | |||||
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| Abstract | Enhanced field emission (EFE) limits the performance of both superconducting and normal conducting high-gradient accelerating structures. Systematic field emission scanning microscopy and correlated SEM/EDX measurements of relevant Nb and Cu samples have revealed particulates and surface irregularities with field enhancement factors b = 10 - 90 as origin of EFE. Based on sufficient emitter statistics, an exponential increase of the emitter number density N with increasing surface field (E) was found. This allows a prediction of the EFE loading of future ILC and CLIC accelerating structures by scaling of N to relevant E and using a weighted integration over the high-field cavity surface. Accordingly, an electropolished (Ra < 300 nm) and dry-ice cleaned (DIC) TESLA-shape 9-cell 1.3 GHz Nb cavity * will still suffer from EFE at Eacc = 35 MV/m (N = 0.3 /cm² at Epeak = 70 MV/m). Moreover, a diamond-turned, chemically etched and DIC 11.2 GHz Cu structure ** will breakdown at Eacc = 100 MV/m (N = 20 /cm² at Epeak = 243 MV/m). Possible improvements, i.e. by emitter processing will be discussed. | |||||
| Footnotes & References | * ILC Technical Design Report (2013) ** A. Grudiev and W. Wuensch, Proceedings of LINAC2010, Tsukuba, Japan, pp. 211 - 213 |
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| Funding | The work is funded by BMBF project 05H12PX6. | |||||
| Paper | download WEPME004.PDF [0.807 MB / 3 pages] | |||||
| Export | download ※ BibTeX ※ LaTeX ※ Text/Word ※ RIS ※ EndNote | |||||
| Conference | IPAC2014, Dresden, Germany | |||||
| Series | International Particle Accelerator Conference (5th) | |||||
| Proceedings | Link to full IPAC2014 Proccedings | |||||
| Session | Poster Session, Messi Area | |||||
| Date | 18-Jun-14 16:00–18:00 | |||||
| Main Classification | 07 Accelerator Technology Main Systems | |||||
| Sub Classification | T08 RF Power Sources | |||||
| Keywords | electron, cavity, vacuum, high-voltage, factory | |||||
| Publisher | JACoW Publishing, Geneva, Switzerland | |||||
| Editors | Christine Petit-Jean-Genaz (CERN, Geneva, Switzerland); Gianluigi Arduini (CERN, Geneva, Switzerland); Peter Michel (HZDR, Dresden, Germany); Volker RW Schaa (GSI, Darmstadt, Germany) | |||||
| ISBN | 978-3-95450-132-8 | |||||
| Published | July 2014 | |||||
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