SRF2023 - List of Authors (Owen, P.D.)

Paper	Title	Page
WEPWB110	Prevention of Dual-Mode Excitation in 9-Cell Cavities for LCLSII-HE	852
	P.D. Owen JLab, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Dual-Mode Excitation, also referred to as mode-mixing, is a superposition of two pi modes in an SRF cavity. In 9-cell TESLA cavities used for the LCLSII-HE project, the two modes that are commonly excited are the pi mode (1300.2 MHz), and the 7/9 pi mode (1297.8 MHz). During vertical cavity qualification testing, it is regularly observed that emitted power at the frequency of the 7/9 pi mode grows, despite the RF system only driving the pi mode. When this happens, the RF power measurement system is unable to differentiate between the superimposed modes which invalidates any data taken. A new RF control solution prevents the 7/9 pi mode from being excited. A second RF control system is connected to drive the 7/9 pi mode. The loop phase for driving this mode is determined, then shifted by 180 degrees, thus providing a negative feedback to the undesired mode. Because this off-resonance power can be very small, it does not interfere with the high-power measurements of the fundamental pi mode. At Jefferson Lab, we are now able to test a cavity for the LCLSII-HE project with no complications from mode-mixing, which allows for CW processing of high-gradient multipacting.
	Poster WEPWB110 [1.818 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB110
About •	Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Prevention of Dual-Mode Excitation in 9-Cell Cavities for LCLSII-HE

852

P.D. Owen
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Dual-Mode Excitation, also referred to as mode-mixing, is a superposition of two pi modes in an SRF cavity. In 9-cell TESLA cavities used for the LCLSII-HE project, the two modes that are commonly excited are the pi mode (1300.2 MHz), and the 7/9 pi mode (1297.8 MHz). During vertical cavity qualification testing, it is regularly observed that emitted power at the frequency of the 7/9 pi mode grows, despite the RF system only driving the pi mode. When this happens, the RF power measurement system is unable to differentiate between the superimposed modes which invalidates any data taken. A new RF control solution prevents the 7/9 pi mode from being excited. A second RF control system is connected to drive the 7/9 pi mode. The loop phase for driving this mode is determined, then shifted by 180 degrees, thus providing a negative feedback to the undesired mode. Because this off-resonance power can be very small, it does not interfere with the high-power measurements of the fundamental pi mode. At Jefferson Lab, we are now able to test a cavity for the LCLSII-HE project with no complications from mode-mixing, which allows for CW processing of high-gradient multipacting.

Poster WEPWB110 [1.818 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB110

About •

Received ※ 19 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023

Cite •

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