IPAC2018 - List of Authors (Xu, H.)

Paper	Title	Page
THPAL033	Measurement of the Internal Dark Current in a High Gradient Accelerator Structure at 17 GHz	3705
SUSPL067	use link to see paper's listing under its alternate paper code
	H. Xu, M.A. Shapiro, R.J. Temkin MIT/PSFC, Cambridge, Massachusetts, USA
	Funding: Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Grant No. DE-SC0015566 We report a study of internal dark current generation by multipactor inside a 17 GHz single cell standing wave disk-loaded waveguide accelerator structure. The multipactor takes place on the side wall of the central cell, driven by the local rf electric and magnetic fields. Theory indicates that a resonant multipactor mode with two rf cycles can be excited near 45 MV/m gradient and a single rf cycle multipactor mode near 60 MV/m. The accelerator structure had two thin slits opened on the side wall of the central cell to directly extract and measure the internal dark current. The dark current was measured as a function of the gradient up to a gradient of 70 MV/m. The experimental results agreed well with theory, showing the two predicted multipactor modes. To further study the effect of the central cell side wall surface properties on the structure performance, we prepared and tested a second structure with the central cell side wall coated with a layer of diamond-like carbon. The comparison of the results showed that the coating reduced the internal dark current and thus enhanced the structure performance considerably.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL033
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Paper

Title

Page

THPAL033

Measurement of the Internal Dark Current in a High Gradient Accelerator Structure at 17 GHz

3705

SUSPL067

use link to see paper's listing under its alternate paper code

H. Xu, M.A. Shapiro, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA

Funding: Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Grant No. DE-SC0015566
We report a study of internal dark current generation by multipactor inside a 17 GHz single cell standing wave disk-loaded waveguide accelerator structure. The multipactor takes place on the side wall of the central cell, driven by the local rf electric and magnetic fields. Theory indicates that a resonant multipactor mode with two rf cycles can be excited near 45 MV/m gradient and a single rf cycle multipactor mode near 60 MV/m. The accelerator structure had two thin slits opened on the side wall of the central cell to directly extract and measure the internal dark current. The dark current was measured as a function of the gradient up to a gradient of 70 MV/m. The experimental results agreed well with theory, showing the two predicted multipactor modes. To further study the effect of the central cell side wall surface properties on the structure performance, we prepared and tested a second structure with the central cell side wall coated with a layer of diamond-like carbon. The comparison of the results showed that the coating reduced the internal dark current and thus enhanced the structure performance considerably.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL033

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)