SRF2021 - List of Keywords (resonance)

Paper	Title	Other Keywords	Page
MOPTEV009	A Method for In-Situ Q₀ Measurements of High-Quality SRF Resonators	beat-wave, cavity, SRF, experiment	221
	S.V. Kuzikov, P.V. Avrakhov, C.-J. Jing, R.A. Kostin, Y. Zhao Euclid TechLabs, Solon, Ohio, USA C.-J. Jing, C.-J. Jing ANL, Lemont, Illinois, USA C.-J. Jing, R.A. Kostin Euclid Beamlabs, Bolingbrook, USA R.A. Kostin, V.P. Yakovlev Fermilab, Batavia, Illinois, USA T. Powers, R.A. Rimmer JLab, Newport News, Virginia, USA
	Funding: The work was supported in the part by DoE SBIR grant #DE-SC0019687. Accelerator projects such as LCLS-II naturally require low-loss superconducting (SRF) cavities. Due to strong demand for improving intrinsic quality factor (Q₀), importance of accurate cavity characterization increases. We propose a method to measure Q₀ in situ for an SRF resonator installed in its cryogenic module and connected with a RF feed source via a fixed RF coupler. The method exploits measurements of a response for an SRF resonator fed by an amplitude-modulated signal. Such a signal can be synthesized as a beat-wave composed of two frequencies that are close to the resonant frequency. Analyzing the envelope of the reflected signal, one can find the difference in reflection for the chosen frequencies and use them to compute the intrinsic Q. We also develop the methodology to carry out measurements of Q₀ at the nominal cavity operating voltage. We verified our method in experiments with a room temperature copper resonator and with two SRF resonators including Fermilab’s 650 MHz cavity and JLab’s 1500 MHz cavity.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV009
About •	Received ※ 15 June 2021 — Revised ※ 26 August 2021 — Accepted ※ 19 February 2022 — Issue date ※ 06 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPFDV006	Dynamics of One-Side Multipactor on Dielectrics	electron, simulation, multipactoring, space-charge	411
	G.V. Romanov Fermilab, Batavia, Illinois, USA
	Breakdown of dielectric RF windows is an important issue for particle accelerators and high-power RF sources. One of the generally considered reasons for the RF windows failure is the multipactor effect on dielectric surface. The multipactor may be responsible for excessive heating of dielectric and discharge of charges that accumulated in ceramic due to secondary emission. In this study the comprehensive self-consistent PIC simulations with space charge effect were performed in order to better understand the dynamic of one-side multipactor development and floating potential on dielectric induced by the emission. The important correlations between the multipactor parameters at saturation and the secondary emission properties of dielectric and the applied RF field parameters were found and are reported in the paper.
	Poster TUPFDV006 [0.849 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV006
About •	Received ※ 17 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 06 October 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPCAV013	Occurring Dependency between Adjustable Coupling and Q₀ - Finding and Solving a Problem during Vertical Cavity Testing at DESY	cavity, coupling, SRF, vacuum	619
	Y.F. Liu, C. Luo SARI-CAS, Pudong, Shanghai, People’s Republic of China D. Reschke, L. Steder, M. Wiencek DESY, Hamburg, Germany
	In the AMTF (Accelerator Module Test Facility) hall at DESY, various types of cavities have been tested for different accelerators and R&D projects during the last years. For R&D purposes, dedicated inserts with additional auxiliaries like a movable INPUT antenna can be used to perform accurate measurements at different temperatures between 1.4 K and 4 K. Since 2017 more than hundred vertical tests were conducted in these inserts without troubles besides rare expected occurrences of cold leaks or even rarer a loose antenna. However, in the last months, an unexpected dependency between the measured quality factor and the coupling coefficient ß has been observed. In order to understand the source of this measurement uncertainty, several different special checks have been performed. In a logical sequence of measurements with different cryostats, inserts and cavities the problem has been encircled and in the end was identified and solved. In this paper, the observed problem is described in detail as well as the entire path leading to its solution.
	Poster WEPCAV013 [1.078 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPCAV013
About •	Received ※ 18 June 2021 — Revised ※ 18 October 2021 — Accepted ※ 18 October 2021 — Issue date ※ 22 November 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPCAV011	Operational Experience with the Mechanical Tuner Systems in the Superconducting Linac at IUAC	controls, cavity, linac, operation	809
	A. Pandey, R. Ahuja, G.K. Chaudhari, B.B. Chaudhary, R.N. Dutt, S. Ghosh, B. Karmakar, J. Karmakar, R. Kumar, D.S. Mathuria, P. Patra, P.N. Potukuchi, A. Rai, B.K. Sahu, S.K. Saini, A. Sharma, S.K. Sonti, S.K. Suman IUAC, New Delhi, India
	The phase locking of the QWRs by dynamic phase control method in the superconducting linac at IUAC is done in a faster time scale. The slow frequency drifts (few hundreds of ms) are corrected using a niobium bellows tuner attached at the open end of the cavity. Initially, the tuners in the cavities were operated using helium gas. This system had the limitation of non-linearity, hysteresis and slow response due to which the cavities could not be phase locked at higher fields. To address this, piezo based tuning system was implemented in the cavities of the 2nd and 3rd linac modules. But due to space constraints, the same could not be used in the 1st linac module and the buncher modules. For them, the helium gas based system was continued, albeit with suitable modifications. The old flow control valves which operated with DC voltages were replaced with valves operating in pulsed mode and controlled by varying the duty cycle of the input pulses. The above mentioned limitations were overcome by using this PWM based technique and this enabled phase locking at higher gradients. This paper presents our operational experience with all the different tuning systems and their comparison.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPCAV011
About •	Received ※ 21 June 2021 — Revised ※ 11 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 27 October 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOPTEV009

A Method for In-Situ Q₀ Measurements of High-Quality SRF Resonators

beat-wave, cavity, SRF, experiment

221

S.V. Kuzikov, P.V. Avrakhov, C.-J. Jing, R.A. Kostin, Y. Zhao
Euclid TechLabs, Solon, Ohio, USA
C.-J. Jing, C.-J. Jing
ANL, Lemont, Illinois, USA
C.-J. Jing, R.A. Kostin
Euclid Beamlabs, Bolingbrook, USA
R.A. Kostin, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
T. Powers, R.A. Rimmer
JLab, Newport News, Virginia, USA

Funding: The work was supported in the part by DoE SBIR grant #DE-SC0019687.
Accelerator projects such as LCLS-II naturally require low-loss superconducting (SRF) cavities. Due to strong demand for improving intrinsic quality factor (Q₀), importance of accurate cavity characterization increases. We propose a method to measure Q₀ in situ for an SRF resonator installed in its cryogenic module and connected with a RF feed source via a fixed RF coupler. The method exploits measurements of a response for an SRF resonator fed by an amplitude-modulated signal. Such a signal can be synthesized as a beat-wave composed of two frequencies that are close to the resonant frequency. Analyzing the envelope of the reflected signal, one can find the difference in reflection for the chosen frequencies and use them to compute the intrinsic Q. We also develop the methodology to carry out measurements of Q₀ at the nominal cavity operating voltage. We verified our method in experiments with a room temperature copper resonator and with two SRF resonators including Fermilab’s 650 MHz cavity and JLab’s 1500 MHz cavity.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV009

About •

Received ※ 15 June 2021 — Revised ※ 26 August 2021 — Accepted ※ 19 February 2022 — Issue date ※ 06 April 2022

Cite •

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

TUPFDV006

Dynamics of One-Side Multipactor on Dielectrics

electron, simulation, multipactoring, space-charge

411

G.V. Romanov
Fermilab, Batavia, Illinois, USA

Breakdown of dielectric RF windows is an important issue for particle accelerators and high-power RF sources. One of the generally considered reasons for the RF windows failure is the multipactor effect on dielectric surface. The multipactor may be responsible for excessive heating of dielectric and discharge of charges that accumulated in ceramic due to secondary emission. In this study the comprehensive self-consistent PIC simulations with space charge effect were performed in order to better understand the dynamic of one-side multipactor development and floating potential on dielectric induced by the emission. The important correlations between the multipactor parameters at saturation and the secondary emission properties of dielectric and the applied RF field parameters were found and are reported in the paper.

Poster TUPFDV006 [0.849 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV006

About •

Received ※ 17 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 06 October 2021

Cite •

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

WEPCAV013

Occurring Dependency between Adjustable Coupling and Q₀ - Finding and Solving a Problem during Vertical Cavity Testing at DESY

cavity, coupling, SRF, vacuum

619

Y.F. Liu, C. Luo
SARI-CAS, Pudong, Shanghai, People’s Republic of China
D. Reschke, L. Steder, M. Wiencek
DESY, Hamburg, Germany

In the AMTF (Accelerator Module Test Facility) hall at DESY, various types of cavities have been tested for different accelerators and R&D projects during the last years. For R&D purposes, dedicated inserts with additional auxiliaries like a movable INPUT antenna can be used to perform accurate measurements at different temperatures between 1.4 K and 4 K. Since 2017 more than hundred vertical tests were conducted in these inserts without troubles besides rare expected occurrences of cold leaks or even rarer a loose antenna. However, in the last months, an unexpected dependency between the measured quality factor and the coupling coefficient ß has been observed. In order to understand the source of this measurement uncertainty, several different special checks have been performed. In a logical sequence of measurements with different cryostats, inserts and cavities the problem has been encircled and in the end was identified and solved. In this paper, the observed problem is described in detail as well as the entire path leading to its solution.

Poster WEPCAV013 [1.078 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPCAV013

About •

Received ※ 18 June 2021 — Revised ※ 18 October 2021 — Accepted ※ 18 October 2021 — Issue date ※ 22 November 2021

Cite •

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

THPCAV011

Operational Experience with the Mechanical Tuner Systems in the Superconducting Linac at IUAC

controls, cavity, linac, operation

809

A. Pandey, R. Ahuja, G.K. Chaudhari, B.B. Chaudhary, R.N. Dutt, S. Ghosh, B. Karmakar, J. Karmakar, R. Kumar, D.S. Mathuria, P. Patra, P.N. Potukuchi, A. Rai, B.K. Sahu, S.K. Saini, A. Sharma, S.K. Sonti, S.K. Suman
IUAC, New Delhi, India

The phase locking of the QWRs by dynamic phase control method in the superconducting linac at IUAC is done in a faster time scale. The slow frequency drifts (few hundreds of ms) are corrected using a niobium bellows tuner attached at the open end of the cavity. Initially, the tuners in the cavities were operated using helium gas. This system had the limitation of non-linearity, hysteresis and slow response due to which the cavities could not be phase locked at higher fields. To address this, piezo based tuning system was implemented in the cavities of the 2nd and 3rd linac modules. But due to space constraints, the same could not be used in the 1st linac module and the buncher modules. For them, the helium gas based system was continued, albeit with suitable modifications. The old flow control valves which operated with DC voltages were replaced with valves operating in pulsed mode and controlled by varying the duty cycle of the input pulses. The above mentioned limitations were overcome by using this PWM based technique and this enabled phase locking at higher gradients. This paper presents our operational experience with all the different tuning systems and their comparison.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPCAV011

About •

Received ※ 21 June 2021 — Revised ※ 11 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 27 October 2021

Cite •

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