SRF2023 - List of Authors (Yao, Z.Y.)

Paper	Title	Page
MOPMB023	Magnetic Flux Expulsion in TRIUMF’s Multi-Mode Coaxial Cavities	135
SUSPB011	use link to see paper's listing under its alternate paper code
	R.R. Gregory, T. Junginger, M.W. McMullin UVIC, Victoria, Canada T. Junginger, P. Kolb, R.E. Laxdal, M.W. McMullin, Z.Y. Yao TRIUMF, Vancouver, Canada
	The external magnetic flux sensitivity of SRF cavities is an important characteristic of SRF accelerator design. Previous studies have shown that n-doped elliptical cavities are very sensitive to external fields, resulting in stringent requirements for residual field and cavity cool-down speed. Few such studies have been done on HWRs and QWRs. The impact of applied field direction and cool-down speed of flux expulsion for these cavities is poorly understood. This study explores the effect of these cool-down characteristics on TRIUMF¿s QWR using COMSOL ® simulations and experimental results. This study seeks to maximize the flux expulsion that occurs when a cavity is cooled down through its superconducting temperature. Flux expulsion is affected by the cool-down speed, temperature gradient, and orientation of the cavity relative to an applied magnetic field. It was found that for a vertically applied magnetic field the cool-down speed and temperature gradient did not have a significant effect on flux expulsion. Contrarily, a horizontal magnetic field can be nearly completely expelled by a fast, high temperature gradient cool-down.
	Poster MOPMB023 [2.191 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB023
About •	Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 30 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB038	Temperature Mapping for Coaxial Cavities at TRIUMF	183
	P. Kolb, T. Junginger, J.J. Keir, R.E. Laxdal, B. Matheson, Z.Y. Yao TRIUMF, Vancouver, Canada H. Al Hassini, T. Junginger UVIC, Victoria, Canada L. Fearn UW/Physics, Waterloo, Ontario, Canada
	Temperature mapping (T-map) on superconducting radio-frequency (SRF) cavities has been shown as a useful tool to identify defects and other abnormal sources of losses. So far T-map systems have only been realized for elliptical cavities that have an easily accessible outer surface. TEM mode cavities such as quarterwave and halfwave resonators (QWR, HWR) dissipate most of their power on the inner conductor of the coaxial structure. The limited access and constrained space are a challenge for the design of a temperature mapping system. This paper describes the mechanical and electrical design including the data acquisition of a T-map system for the TRIUMF multi-mode coaxial cavities, and first results are shown.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB038
About •	Received ※ 20 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 30 June 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB050	Thermal Feedback in Coaxial SRF Cavities	224
SUSPB020	use link to see paper's listing under its alternate paper code
	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)

MOPMB092	Performance of Contaminated Superconducting Linac after Vacuum Excursion	332
	Z.Y. Yao, R.E. Laxdal TRIUMF, Vancouver, Canada
	ISAC-II superconducting heavy ion linac is the high energy section of TRIUMF ISAC facility to accelerate rare isotopes with A/q <= 6 from 1.5 MeV/u to above the Cou-lomb barrier for experiments. There was a vacuum excur-sion caused by an operational error and the failure of the fast protection system in summer 2022. The beamline downstream to the SC linac was vented with atmosphere air from the experimental hall resulting in pollution of the linac. This paper reports the RF performance of the con-taminated linac. The typical cavity performance changes, the average magnitude of degradation, the impact range in the SC linac, the observations in the recovery processes and the analyses on the most distinct cavity are discussed. The cavity refurbishment in the recent winter shutdown with the observations and outcomes is also reported. The ISAC-II event provided a unique data set for the SRF community.
	Poster MOPMB092 [6.186 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB092
About •	Received ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 02 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

MOPMB023

Magnetic Flux Expulsion in TRIUMF’s Multi-Mode Coaxial Cavities

135

SUSPB011

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

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

The external magnetic flux sensitivity of SRF cavities is an important characteristic of SRF accelerator design. Previous studies have shown that n-doped elliptical cavities are very sensitive to external fields, resulting in stringent requirements for residual field and cavity cool-down speed. Few such studies have been done on HWRs and QWRs. The impact of applied field direction and cool-down speed of flux expulsion for these cavities is poorly understood. This study explores the effect of these cool-down characteristics on TRIUMF¿s QWR using COMSOL ® simulations and experimental results. This study seeks to maximize the flux expulsion that occurs when a cavity is cooled down through its superconducting temperature. Flux expulsion is affected by the cool-down speed, temperature gradient, and orientation of the cavity relative to an applied magnetic field. It was found that for a vertically applied magnetic field the cool-down speed and temperature gradient did not have a significant effect on flux expulsion. Contrarily, a horizontal magnetic field can be nearly completely expelled by a fast, high temperature gradient cool-down.

Poster MOPMB023 [2.191 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB023

About •

Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 30 July 2023

Cite •

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

MOPMB038

Temperature Mapping for Coaxial Cavities at TRIUMF

183

P. Kolb, T. Junginger, J.J. Keir, R.E. Laxdal, B. Matheson, Z.Y. Yao
TRIUMF, Vancouver, Canada
H. Al Hassini, T. Junginger
UVIC, Victoria, Canada
L. Fearn
UW/Physics, Waterloo, Ontario, Canada

Temperature mapping (T-map) on superconducting radio-frequency (SRF) cavities has been shown as a useful tool to identify defects and other abnormal sources of losses. So far T-map systems have only been realized for elliptical cavities that have an easily accessible outer surface. TEM mode cavities such as quarterwave and halfwave resonators (QWR, HWR) dissipate most of their power on the inner conductor of the coaxial structure. The limited access and constrained space are a challenge for the design of a temperature mapping system. This paper describes the mechanical and electrical design including the data acquisition of a T-map system for the TRIUMF multi-mode coaxial cavities, and first results are shown.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB038

About •

Received ※ 20 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 30 June 2023

Cite •

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

MOPMB050

Thermal Feedback in Coaxial SRF Cavities

224

SUSPB020

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

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)

MOPMB092

Performance of Contaminated Superconducting Linac after Vacuum Excursion

332

Z.Y. Yao, R.E. Laxdal
TRIUMF, Vancouver, Canada

ISAC-II superconducting heavy ion linac is the high energy section of TRIUMF ISAC facility to accelerate rare isotopes with A/q <= 6 from 1.5 MeV/u to above the Cou-lomb barrier for experiments. There was a vacuum excur-sion caused by an operational error and the failure of the fast protection system in summer 2022. The beamline downstream to the SC linac was vented with atmosphere air from the experimental hall resulting in pollution of the linac. This paper reports the RF performance of the con-taminated linac. The typical cavity performance changes, the average magnitude of degradation, the impact range in the SC linac, the observations in the recovery processes and the analyses on the most distinct cavity are discussed. The cavity refurbishment in the recent winter shutdown with the observations and outcomes is also reported. The ISAC-II event provided a unique data set for the SRF community.

Poster MOPMB092 [6.186 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB092

About •

Received ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 02 July 2023

Cite •

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