SRF2013 - List of Authors (Charrier, J.-P.)

Paper

Title

Page

Vertical Electropolishing of SRF Cavities and its Parameters Investigation

514

F. Eozénou, F. Ballester, Y. Boudigou, P. Carbonnier, J.-P. Charrier, Y. Gasser, D. Roudier, C. Servouin
CEA/DSM/IRFU, France
K. Muller
Grenoble-INP Phelma, Grenoble, France

Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP7 program (EuCARD, Contract No. 227579),and the support of the ‘‘Conseil General de l’Essonne’’(ASTRE)
An advanced set-up for vertical electropolishing (VEP) of SRF niobium elliptical cavities is operating at CEA Saclay*. Cavities are VEP’ed with circulating standard HF-H2SO4 electrolyte. Parameters such as voltage, cathode shape, acid flow and temperature were investigated. Low-voltage (<7V), high acid flow (25L/min) and low acid temperature (20°C) are considered as promising parameters. Such recipe was tested on single-cell and 9-cell ILC cavities with nice surface finishing. After 60 μm VEP on a HEP'ed single-cell, the cavity show similar performance at 1.6K compared to previous Horizontal EP: (Eacc > 41MV/m) limited by quench. Another cavity reaches 36MV/m after 300μm removal by VEP in spite of a pitted surface due to initial VEP treatment at higher temperature (> 30°C). The baking effect after HEP/VEP is similar. An asymmetric niobium removal is observed with faster polishing in the upper cell. Nice surface finishing as well as standard Q0 value are obtained at low/medium field on 9Cell but achieved performance is limited by Field Emission.
*F. Eozenou et al., PRST-AB, 15, 083501 (2012)

TUP111

Experimental Investigations of the Quench Phenomena for the Quench Localization by the Second Sound Wave Method

739

J. Plouin, J.-P. Charrier, C. Magne, J. Novo
CEA/DSM/IRFU, France
L. Maurice
CEA/IRFU, Gif-sur-Yvette, France

The quench localization by the second sound method is now widely used in many laboratories. This method avoids the complicated implementation of temperature arrays around the surface cavities. Instead, specific sensors are placed around the cavity and the time of arrival of the second sound wave generated by the quench is measured on each sensor; then the distance from sensors to quench is deducted from the theoretical second sound wave velocity. In principle, the quench position can be localized with a triangulation by a limited number of sensors. However, many measurements have shown that the time of arrival of the wave was not corresponding to the theoretical second sound wave velocity: the “measured” velocity is often 50% higher than the theory. At CEA-Saclay we performed several measurements on single cell cavities to investigate these phenomena. Several hypotheses are studied: large quench spot, heat propagation by another phenomenon than the second sound near to the cavity where the heat power density is very high. These results and the discussions on these hypotheses will be presented.

THIOA02

The Challenge to Assemble 100 Cryomodules for the European E-XFEL

816

C. Madec
CEA, Gif-sur-Yvette, France
S. Berry, J.-P. Charrier, M. Fontaine, Y. Gasser, O. Napoly, C.S. Simon, T.V. Vacher, B. Visentin
CEA/DSM/IRFU, France
P. Charon, C. Cloué, G. Monnereau, J.L. Perrin, D. Roudier, Y. Sauce, T. Trublet
CEA/IRFU, Gif-sur-Yvette, France

As In-Kind contributor to the E-XFEL project, CEA is committed to the integration on the Saclay site of the 100 cryomodules (CM) of the superconducting linac as well as to the procurement of miscellaneous parts including 31 cold beam position monitors (BPM) of the re-entrant type. The assembly infrastructure has been renovated from the previous Saturne Synchrotron Laboratory facility: it includes a 200 m2 clean room complex with 112 m2 under ISO4, 1325 m2 of assembly platforms and 400 m2 of storage area. In parallel, CEA has conducted industrial studies and three cryomodule assembly prototyping both aiming at preparing the industrial file, the quality management system and the commissioning of the assembly plant, tooling and control equipment. In 2012, the contract of the integration has been awarded to ALSYOM. The first pre-series modules have been assembled and are being tested at DESY. This paper will present the challenges of the module integration from the preparation phase to the industrial phase.

Slides THIOA02 [17.641 MB]

Paper	Title	Page
TUP046	Vertical Electropolishing of SRF Cavities and its Parameters Investigation	514
	F. Eozénou, F. Ballester, Y. Boudigou, P. Carbonnier, J.-P. Charrier, Y. Gasser, D. Roudier, C. Servouin CEA/DSM/IRFU, France K. Muller Grenoble-INP Phelma, Grenoble, France
	Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP7 program (EuCARD, Contract No. 227579),and the support of the ‘‘Conseil General de l’Essonne’’(ASTRE) An advanced set-up for vertical electropolishing (VEP) of SRF niobium elliptical cavities is operating at CEA Saclay. Cavities are VEP’ed with circulating standard HF-H2SO4 electrolyte. Parameters such as voltage, cathode shape, acid flow and temperature were investigated. Low-voltage (<7V), high acid flow (25L/min) and low acid temperature (20°C) are considered as promising parameters. Such recipe was tested on single-cell and 9-cell ILC cavities with nice surface finishing. After 60 μm VEP on a HEP'ed single-cell, the cavity show similar performance at 1.6K compared to previous Horizontal EP: (Eacc > 41MV/m) limited by quench. Another cavity reaches 36MV/m after 300μm removal by VEP in spite of a pitted surface due to initial VEP treatment at higher temperature (> 30°C). The baking effect after HEP/VEP is similar. An asymmetric niobium removal is observed with faster polishing in the upper cell. Nice surface finishing as well as standard Q0 value are obtained at low/medium field on 9Cell but achieved performance is limited by Field Emission. F. Eozenou et al., PRST-AB, 15, 083501 (2012)

TUP111	Experimental Investigations of the Quench Phenomena for the Quench Localization by the Second Sound Wave Method	739
	J. Plouin, J.-P. Charrier, C. Magne, J. Novo CEA/DSM/IRFU, France L. Maurice CEA/IRFU, Gif-sur-Yvette, France
	The quench localization by the second sound method is now widely used in many laboratories. This method avoids the complicated implementation of temperature arrays around the surface cavities. Instead, specific sensors are placed around the cavity and the time of arrival of the second sound wave generated by the quench is measured on each sensor; then the distance from sensors to quench is deducted from the theoretical second sound wave velocity. In principle, the quench position can be localized with a triangulation by a limited number of sensors. However, many measurements have shown that the time of arrival of the wave was not corresponding to the theoretical second sound wave velocity: the “measured” velocity is often 50% higher than the theory. At CEA-Saclay we performed several measurements on single cell cavities to investigate these phenomena. Several hypotheses are studied: large quench spot, heat propagation by another phenomenon than the second sound near to the cavity where the heat power density is very high. These results and the discussions on these hypotheses will be presented.

THIOA02	The Challenge to Assemble 100 Cryomodules for the European E-XFEL	816
	C. Madec CEA, Gif-sur-Yvette, France S. Berry, J.-P. Charrier, M. Fontaine, Y. Gasser, O. Napoly, C.S. Simon, T.V. Vacher, B. Visentin CEA/DSM/IRFU, France P. Charon, C. Cloué, G. Monnereau, J.L. Perrin, D. Roudier, Y. Sauce, T. Trublet CEA/IRFU, Gif-sur-Yvette, France
	As In-Kind contributor to the E-XFEL project, CEA is committed to the integration on the Saclay site of the 100 cryomodules (CM) of the superconducting linac as well as to the procurement of miscellaneous parts including 31 cold beam position monitors (BPM) of the re-entrant type. The assembly infrastructure has been renovated from the previous Saturne Synchrotron Laboratory facility: it includes a 200 m2 clean room complex with 112 m2 under ISO4, 1325 m2 of assembly platforms and 400 m2 of storage area. In parallel, CEA has conducted industrial studies and three cryomodule assembly prototyping both aiming at preparing the industrial file, the quality management system and the commissioning of the assembly plant, tooling and control equipment. In 2012, the contract of the integration has been awarded to ALSYOM. The first pre-series modules have been assembled and are being tested at DESY. This paper will present the challenges of the module integration from the preparation phase to the industrial phase.
	Slides THIOA02 [17.641 MB]