High-gradient behavior of a dipole-mode rf structure
| Autor: | Graeme Burt, Amos Dexter, Alberto Degiovanni, R. Peacock, J. Giner Navarro, E. Rodriguez Castro, Benjamin Woolley, Walter Wuensch, A. Grudiev, Igor Syratchev, N. Catalan Lasheras, Gerard McMonagle, W. L. Millar |
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| Rok vydání: | 2020 |
| Předmět: |
Physics
Nuclear and High Energy Physics Physics and Astronomy (miscellaneous) Compact Linear Collider Field (physics) 010308 nuclear & particles physics Crab cavity Surfaces and Interfaces Accelerators and Storage Rings 01 natural sciences Power law Magnetic field Dipole Electric field 0103 physical sciences Poynting vector lcsh:QC770-798 lcsh:Nuclear and particle physics. Atomic energy. Radioactivity Atomic physics 010306 general physics |
| Zdroj: | Physical Review Accelerators and Beams, Vol 23, Iss 12, p 122002 (2020) |
| ISSN: | 2469-9888 |
| DOI: | 10.1103/physrevaccelbeams.23.122002 |
| Popis: | A normal-conducting, X-band traveling wave structure operating in the dipole mode has been systematically high-gradient tested to gain insight into the maximum possible gradients in these types of structure. Measured structure conditioning, breakdown behavior, and achieved surface fields are reported as well as a postmortem analysis of the breakdown position and a scanning electron microscope analysis of the high-field surfaces. The results of these measurements are then compared to high-gradient results from monopole-mode cavities. Scaled to a breakdown rate of ${10}^{\ensuremath{-}6}$, the cavities were found to operate at a peak electric field of $154\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ and a peak modified Poynting vector ${S}_{c}$ of $5.48\text{ }\text{ }\mathrm{MW}/{\mathrm{mm}}^{2}$. The study provides important input for the further development of dipole-mode cavities for use in the Compact Linear Collider as a crab cavity and dipole-mode cavities for use in x-ray free-electron lasers as well as for studies of the fundamental processes in vacuum arcs. Of particular relevance are the unique field patterns in dipole cavities compared to monopole cavities, where the electric and magnetic fields peak in orthogonal planes, which allow the separation of the role of electric and magnetic fields in breakdown via postmortem damage observation. The azimuthal variation of breakdown crater density is measured and is fitted to sinusoidal functions. The best fit is a power law fit of exponent 6. This is significant, as it shows how breakdown probability varies over a surface area with a varying electric field after conditioning to a given peak field. |
| Databáze: | OpenAIRE |
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