SRF2023 - List of Keywords (feedback)

Paper	Title	Other Keywords	Page
MOPMB050	Thermal Feedback in Coaxial SRF Cavities	cavity, niobium, SRF, ECR	224
	M.W. McMullin, P. Kolb, R.E. Laxdal, Z.Y. Yao TRIUMF, Vancouver, Canada T. Junginger UVIC, Victoria, Canada
	Funding: Natural Sciences and Engineering Research Council of Canada The phenomenon of Q-slope in SRF cavities is caused by a combination of thermal feedback and field-dependent surface resistance. There is currently no commonly accepted model of field-dependent surface resistance, and studies of Q-slope generally treat thermal feedback as a correction to whichever surface resistance model is being used. In the present study, we treat thermal feedback as a distinct physical effect whose effect on Q-slope is calculated using a novel finite-element code. We performed direct measurements of liquid helium pool boiling from niobium surfaces to obtain input parameters for the finite-element code. This code was used to analyze data from TRIUMF’s coaxial test cavity program, which has provided a rich dataset of Q-curves at temperatures between 1.7 K and 4.4 K at five different frequencies. Preliminary results show that thermal feedback makes only a small contribution to Q-slope at temperatures near 4.2 K, but has stronger effects as the bath temperature is lowered.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB050
About •	Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 09 August 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTB025	Preparation of the Assembly of the 650 MHz Low Beta Cryomodules for the PIP-II Linear Accelerator	cryomodule, cavity, alignment, vacuum	442
	J. Drant, N. Bazin, S. Berry, A. Raut CEA-DRF-IRFU, France R. Cubizolles, A. Moreau CEA-IRFU, Gif-sur-Yvette, France
	The Proton Improvement Plan II (PIP-II) that will be installed at Fermilab is the first U.S. accelerator project that will have significant contributions from international partners. CEA¿s scope covers the supply of the 650 MHz low-beta cryomodule sections with the cavities provided by LASA-INFN (Italy) and VECC-DAE (India) as well as the power couplers supplied by Fermilab. This scope includes the assembly of the 650 MHz low-beta cryomodules. Assembly studies have been conducted based on CEA experience acquired on previous projects as well as on the feedback of Fermilab on the assembly of the HB650 prototype cryomodule. This paper presents the organization of assembly phases from the cavity string in the clean room and the assembly of the cryostat to the preparation of the cryomodule before its shipment to Fermilab.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB025
About •	Received ※ 16 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 07 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB110	Prevention of Dual-Mode Excitation in 9-Cell Cavities for LCLSII-HE	cavity, resonance, controls, SRF	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

Other Keywords

Page

MOPMB050

Thermal Feedback in Coaxial SRF Cavities

cavity, niobium, SRF, ECR

224

M.W. McMullin, P. Kolb, R.E. Laxdal, Z.Y. Yao
TRIUMF, Vancouver, Canada
T. Junginger
UVIC, Victoria, Canada

Funding: Natural Sciences and Engineering Research Council of Canada
The phenomenon of Q-slope in SRF cavities is caused by a combination of thermal feedback and field-dependent surface resistance. There is currently no commonly accepted model of field-dependent surface resistance, and studies of Q-slope generally treat thermal feedback as a correction to whichever surface resistance model is being used. In the present study, we treat thermal feedback as a distinct physical effect whose effect on Q-slope is calculated using a novel finite-element code. We performed direct measurements of liquid helium pool boiling from niobium surfaces to obtain input parameters for the finite-element code. This code was used to analyze data from TRIUMF’s coaxial test cavity program, which has provided a rich dataset of Q-curves at temperatures between 1.7 K and 4.4 K at five different frequencies. Preliminary results show that thermal feedback makes only a small contribution to Q-slope at temperatures near 4.2 K, but has stronger effects as the bath temperature is lowered.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB050

About •

Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 09 August 2023

Cite •

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

TUPTB025

Preparation of the Assembly of the 650 MHz Low Beta Cryomodules for the PIP-II Linear Accelerator

cryomodule, cavity, alignment, vacuum

442

J. Drant, N. Bazin, S. Berry, A. Raut
CEA-DRF-IRFU, France
R. Cubizolles, A. Moreau
CEA-IRFU, Gif-sur-Yvette, France

The Proton Improvement Plan II (PIP-II) that will be installed at Fermilab is the first U.S. accelerator project that will have significant contributions from international partners. CEA¿s scope covers the supply of the 650 MHz low-beta cryomodule sections with the cavities provided by LASA-INFN (Italy) and VECC-DAE (India) as well as the power couplers supplied by Fermilab. This scope includes the assembly of the 650 MHz low-beta cryomodules. Assembly studies have been conducted based on CEA experience acquired on previous projects as well as on the feedback of Fermilab on the assembly of the HB650 prototype cryomodule. This paper presents the organization of assembly phases from the cavity string in the clean room and the assembly of the cryostat to the preparation of the cryomodule before its shipment to Fermilab.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB025

About •

Received ※ 16 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 07 July 2023

Cite •

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

WEPWB110

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

cavity, resonance, controls, SRF

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)