SRF2015 - List of Keywords (network)

Paper	Title	Other Keywords	Page
TUPB089	High-Precision Measurements of the Quality Factor of Superconducting Cavities at the FREIA Laboratory	cavity, coupling, impedance, SRF	810
	V.A. Goryashko, K.J. Gajewski, L. Hermansson, H. Li, H. Nicander, R.J.M.Y. Ruber, R. Santiago Kern, S. Teerikoski Uppsala University, Uppsala, Sweden D.S. Dancila Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
	In this paper we propose a high-precision method of measuring Q0 of SRF cavities. A common way to study the performance of an SRF cavity is to build an oscillator around it that is referred to as a self-exciting loop. In the standard approach, by tuning the loop phase for a maximum field level in the cavity and measuring forward and reflected waves, one finds the cavity coupling. Then, performing a time-decay measurement and finding the total quality factor, one gets Q0. However, this approach suffers from a deficiency originating from a single data-point measurement of the reflection coefficient. In our method by varying the loop phase shift, one obtains amplitudes of the reflection coefficient of the cavity as a function of its phases. The complex reflection coefficient describes a perfect circle in polar coordinates. Fitting the overdetermined set of data to that circle allows more accurate calculation of Q0 via the least-squares procedure. The method has been tested at the FREIA Laboratory on two cavities from IPN Orsay: a single spoke and a prototype ESS double spoke.
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TUPB094	Jefferson Lab Vertical Test Area RF System Improvement	cavity, controls, software, low-level-rf	823
	T. Powers, M.L. Morrone JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 with supplemental funding from the LCLS-II Project U.S. DOE Contract No. DE-AC02-76SF00515. RF systems for testing critically coupled SRF cavities require the ability to track the cavity frequency excursions while making accurate measurements of the radio frequency (RF) signals associated with the cavity. Two types of systems are being used at Jefferson Lab. The first, the traditional approach, is to use a voltage controlled oscillator configured as a phase locked loop such that it will track the cavity frequency. The more recently developed approach is to use a digital low level RF (LLRF) system in self excited loop (SEL) mode to track the cavity frequency. Using a digital LLRF system in SEL mode has the advantage that it is much easier to lock to the cavity’s resonant frequencies and they tend to have a wider capture range. This paper will report on the system designs used to implement the 12 GeV digital LLRF system in the JLAB vertical test area. Additionally, it will report on the system modifications which are being implemented so that the RF infrastructure in the VTA will be ready to support the LCLS II cryomodule production effort, which is scheduled to begin in calendar year 2016.
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TUPB109	Assembly and Cool-Down Tests of STF2 Cryomodule at KEK	cavity, HOM, cryomodule, vacuum	888
	T. Shishido, K. Hara, E. Kako, Y. Kojima, H. Nakai, Y. Yamamoto KEK, Ibaraki, Japan
	As the next step of the quantum beam project, the STF2 project is in progress at KEK. Eight 9-cell SC cavities and one superconducting quardrapole magnet were assembled into the cryomodule called CM1. Four 9-cell SC cavities were assembled into the cryomodule called CM2a. These two cryomodules were connected as one unit, and the examination of completion by a prefectural government was carried out. The target value of beam energy in the STF2 accelerator is 400 MeV with a beam current of 6 mA. The first cool down test for low power level RF measurements was performed in autumn of 2014. In this paper, the assembly procedure of the STF2 cryomodules and the results of the low-power measurement are reported.
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Paper

Title

Other Keywords

Page

TUPB089

High-Precision Measurements of the Quality Factor of Superconducting Cavities at the FREIA Laboratory

cavity, coupling, impedance, SRF

810

V.A. Goryashko, K.J. Gajewski, L. Hermansson, H. Li, H. Nicander, R.J.M.Y. Ruber, R. Santiago Kern, S. Teerikoski
Uppsala University, Uppsala, Sweden
D.S. Dancila
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden

In this paper we propose a high-precision method of measuring Q0 of SRF cavities. A common way to study the performance of an SRF cavity is to build an oscillator around it that is referred to as a self-exciting loop. In the standard approach, by tuning the loop phase for a maximum field level in the cavity and measuring forward and reflected waves, one finds the cavity coupling. Then, performing a time-decay measurement and finding the total quality factor, one gets Q0. However, this approach suffers from a deficiency originating from a single data-point measurement of the reflection coefficient. In our method by varying the loop phase shift, one obtains amplitudes of the reflection coefficient of the cavity as a function of its phases. The complex reflection coefficient describes a perfect circle in polar coordinates. Fitting the overdetermined set of data to that circle allows more accurate calculation of Q0 via the least-squares procedure. The method has been tested at the FREIA Laboratory on two cavities from IPN Orsay: a single spoke and a prototype ESS double spoke.

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TUPB094

Jefferson Lab Vertical Test Area RF System Improvement

cavity, controls, software, low-level-rf

823

T. Powers, M.L. Morrone
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 with supplemental funding from the LCLS-II Project U.S. DOE Contract No. DE-AC02-76SF00515.
RF systems for testing critically coupled SRF cavities require the ability to track the cavity frequency excursions while making accurate measurements of the radio frequency (RF) signals associated with the cavity. Two types of systems are being used at Jefferson Lab. The first, the traditional approach, is to use a voltage controlled oscillator configured as a phase locked loop such that it will track the cavity frequency. The more recently developed approach is to use a digital low level RF (LLRF) system in self excited loop (SEL) mode to track the cavity frequency. Using a digital LLRF system in SEL mode has the advantage that it is much easier to lock to the cavity’s resonant frequencies and they tend to have a wider capture range. This paper will report on the system designs used to implement the 12 GeV digital LLRF system in the JLAB vertical test area. Additionally, it will report on the system modifications which are being implemented so that the RF infrastructure in the VTA will be ready to support the LCLS II cryomodule production effort, which is scheduled to begin in calendar year 2016.

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TUPB109

Assembly and Cool-Down Tests of STF2 Cryomodule at KEK

cavity, HOM, cryomodule, vacuum

888

T. Shishido, K. Hara, E. Kako, Y. Kojima, H. Nakai, Y. Yamamoto
KEK, Ibaraki, Japan

As the next step of the quantum beam project, the STF2 project is in progress at KEK. Eight 9-cell SC cavities and one superconducting quardrapole magnet were assembled into the cryomodule called CM1. Four 9-cell SC cavities were assembled into the cryomodule called CM2a. These two cryomodules were connected as one unit, and the examination of completion by a prefectural government was carried out. The target value of beam energy in the STF2 accelerator is 400 MeV with a beam current of 6 mA. The first cool down test for low power level RF measurements was performed in autumn of 2014. In this paper, the assembly procedure of the STF2 cryomodules and the results of the low-power measurement are reported.

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)