SRF2019 - List of Authors (Macpherson, A.)

Paper	Title	Page
WETEB7	A Ferroelectric Fast Reactive Tuner for Superconducting Cavities	781
	N.C. Shipman, J. Bastard, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley CERN, Meyrin, Switzerland I. Ben-Zvi BNL, Upton, New York, USA G. Burt, A. Castilla Lancaster University, Lancaster, United Kingdom C.-J. Jing, A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA S. Kazakov Fermilab, Batavia, Illinois, USA E. Nenasheva Ceramics Ltd., St. Petersburg, Russia
	A prototype FerroElectric Fast Reactive Tuner (FE-FRT) for superconducting cavities has been developed, which allows the frequency to be controlled by application of a potential difference across a ferroelectric residing within the tuner. This technique has now become practically feasible due to the recent development of a new extremely low loss ferroelectric material. In a world first, CERN has tested the prototype FE-FRT with a superconducting cavity, and frequency tuning has been successfully demonstrated. This is a significant first step in the development of an entirely new class of tuner. These will allow electronic control of cavity frequencies, by a device operating at room temperature, within timescales that will allow active compensation of microphonics. For many applications this could eliminate the need to use over-coupled fundamental power couplers, thus significantly reducing RF amplifier power.
	Slides WETEB7 [21.570 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-WETEB7
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP078	CERN’s SRF Test Stand for Cavity Performance Measurements	1082
	N. Stapley, J. Bastard, M.R. Coly, A.E. Ivanov, A. Macpherson, N.C. Shipman, K. Turaj CERN, Geneva, Switzerland I. Ben-Zvi BNL, Upton, New York, USA A. Castilla Cockcroft Institute, Lancaster University, Lancaster, United Kingdom K. Hernandez-Chahin Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico M. Wartak, A. Zwozniak IFJ-PAN, Kraków, Poland
	Recent deployment of a digital LLRF system within the cavity testing framework of CERN’s vertical test cryostats has permitted a full revamp of cavity performance validation. With both full continuous and pulse mode operation, steady state a transient RF behaviour can be effectively probed. Due to direct and integrated control and monitoring of environmental test conditions, standard and novel RF measurement procedures have been developed and integrated into the testing infrastructure, along with a coherent data flow of high granularity measurement data. We present an overview of this cavity measurement system and address the underlying architectural structure, data handling and integration of user interfaces. In addition we highlight the benefits of variety of RF cavity measurements that can now be accommodated in our large 2 K cryostats.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP078
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP095	Direct Measurement of Thermoelectric Currents During Cool Down	1139
	A.E. Ivanov, F. Gerigk, A. Macpherson CERN, Geneva, Switzerland
	In recent years there has been much discussion on thermoelectric effects and their role in flux expulsion during cool down of SRF cavities. Magnetic field is often measured to asses both flux expulsion as the cavity undergoes superconducting transition, and thermoelectric currents due to spatial thermal gradients. As a complementary view, in this paper we show direct measurement of the thermoelectric current independent from the expulsion measurement of the magnetic field. In our setup the azimuthally symmetric cavity is vertically installed and the thermal gradient is along the symmetry axis allowing to describe the cool down behavior of the thermoelectric current using simple coupled simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP095
About •	paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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THP105	Thermal Mapping of SRF Cavities by Second Sound Detection With Transition Edge Sensors and Oscillating Superleak Transducers	1182
	G. Vandoni, T. Koettig, A. Macpherson, K. Turaj, L. Vega Cid CERN, Geneva, Switzerland H. Furci EPFL, Lausanne, Switzerland
	The SRF cavity testing facilities at CERN include four vertical cryostat stations in SM18 and a cryostat for small cavities in the Cryolab. A large range of structures are tested, from Nb thin film cavities for HIE-Isolde and LHC, to bulk Nb crab cavities for HiLumi or 704 MHz 5-cell high-gradient cavities. To cope with different shapes and small series tests, thermal mapping diagnostics is deployed by sensing second sound in superfluid helium. A new type of Transition Edge Sensors (TES) has been developed in the last 2 years. These are miniature resistors of thin-film superconducting alloys, micro-produced on insulating wafers. An extensive campaign of optimization of design, fabrication process and composition was accompanied by qualification in a calibration cryostat. Reproducibility, stability, then intensity, distance and angular dependence of the response were assessed and compared to Oscillating Superleak Transducers (OST). The TES were then installed in a vertical cryostat for tests of a prototype crab cavity for HiLumi. TES are now applied to quench localization on high gradient cavities, for which the most recent results will be presented, together with the OST results.
	Poster THP105 [2.186 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP105
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

A Ferroelectric Fast Reactive Tuner for Superconducting Cavities

781

N.C. Shipman, J. Bastard, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley
CERN, Meyrin, Switzerland
I. Ben-Zvi
BNL, Upton, New York, USA
G. Burt, A. Castilla
Lancaster University, Lancaster, United Kingdom
C.-J. Jing, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
S. Kazakov
Fermilab, Batavia, Illinois, USA
E. Nenasheva
Ceramics Ltd., St. Petersburg, Russia

A prototype FerroElectric Fast Reactive Tuner (FE-FRT) for superconducting cavities has been developed, which allows the frequency to be controlled by application of a potential difference across a ferroelectric residing within the tuner. This technique has now become practically feasible due to the recent development of a new extremely low loss ferroelectric material. In a world first, CERN has tested the prototype FE-FRT with a superconducting cavity, and frequency tuning has been successfully demonstrated. This is a significant first step in the development of an entirely new class of tuner. These will allow electronic control of cavity frequencies, by a device operating at room temperature, within timescales that will allow active compensation of microphonics. For many applications this could eliminate the need to use over-coupled fundamental power couplers, thus significantly reducing RF amplifier power.

Slides WETEB7 [21.570 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-WETEB7

About •

paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

THP078

CERN’s SRF Test Stand for Cavity Performance Measurements

1082

N. Stapley, J. Bastard, M.R. Coly, A.E. Ivanov, A. Macpherson, N.C. Shipman, K. Turaj
CERN, Geneva, Switzerland
I. Ben-Zvi
BNL, Upton, New York, USA
A. Castilla
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
K. Hernandez-Chahin
Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
M. Wartak, A. Zwozniak
IFJ-PAN, Kraków, Poland

Recent deployment of a digital LLRF system within the cavity testing framework of CERN’s vertical test cryostats has permitted a full revamp of cavity performance validation. With both full continuous and pulse mode operation, steady state a transient RF behaviour can be effectively probed. Due to direct and integrated control and monitoring of environmental test conditions, standard and novel RF measurement procedures have been developed and integrated into the testing infrastructure, along with a coherent data flow of high granularity measurement data. We present an overview of this cavity measurement system and address the underlying architectural structure, data handling and integration of user interfaces. In addition we highlight the benefits of variety of RF cavity measurements that can now be accommodated in our large 2 K cryostats.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP078

About •

paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

THP095

Direct Measurement of Thermoelectric Currents During Cool Down

1139

A.E. Ivanov, F. Gerigk, A. Macpherson
CERN, Geneva, Switzerland

In recent years there has been much discussion on thermoelectric effects and their role in flux expulsion during cool down of SRF cavities. Magnetic field is often measured to asses both flux expulsion as the cavity undergoes superconducting transition, and thermoelectric currents due to spatial thermal gradients. As a complementary view, in this paper we show direct measurement of the thermoelectric current independent from the expulsion measurement of the magnetic field. In our setup the azimuthally symmetric cavity is vertically installed and the thermal gradient is along the symmetry axis allowing to describe the cool down behavior of the thermoelectric current using simple coupled simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP095

About •

paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

THP105

Thermal Mapping of SRF Cavities by Second Sound Detection With Transition Edge Sensors and Oscillating Superleak Transducers

1182

G. Vandoni, T. Koettig, A. Macpherson, K. Turaj, L. Vega Cid
CERN, Geneva, Switzerland
H. Furci
EPFL, Lausanne, Switzerland

The SRF cavity testing facilities at CERN include four vertical cryostat stations in SM18 and a cryostat for small cavities in the Cryolab. A large range of structures are tested, from Nb thin film cavities for HIE-Isolde and LHC, to bulk Nb crab cavities for HiLumi or 704 MHz 5-cell high-gradient cavities. To cope with different shapes and small series tests, thermal mapping diagnostics is deployed by sensing second sound in superfluid helium. A new type of Transition Edge Sensors (TES) has been developed in the last 2 years. These are miniature resistors of thin-film superconducting alloys, micro-produced on insulating wafers. An extensive campaign of optimization of design, fabrication process and composition was accompanied by qualification in a calibration cryostat. Reproducibility, stability, then intensity, distance and angular dependence of the response were assessed and compared to Oscillating Superleak Transducers (OST). The TES were then installed in a vertical cryostat for tests of a prototype crab cavity for HiLumi. TES are now applied to quench localization on high gradient cavities, for which the most recent results will be presented, together with the OST results.

Poster THP105 [2.186 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP105

About •

paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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