SRF2011 - List of Authors (Junginger, T.)

Paper

Title

Page

Review of RF‐Sample‐Test Equipment and Results

579

T. Junginger, W. Weingarten
CERN, Geneva, Switzerland
T. Junginger
MPI-K, Heidelberg, Germany
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Work supported by the German Doctoral Students program of the Federal Ministry of Education and Research (BMBF)
The surface resistance of superconducting samples can be derived from the heat dissipation under RF exposure. This requires challenging and sometimes opposing design constraints. The samples shall be small and easily exchangeable. The RF magnetic field on the sample surface shall be large and homogeneous. It must not be limited by the host cavity. A calorimetric technique enables precise measurements and has therefore recently gained much interest. One of the devices exploiting this technique at multiple frequencies is the Quadrupole Resonator. Its measurement capabilities and limitations are discussed and compared with similar devices. Results on bulk niobium and niobium film on copper samples are presented. It is shown how different contributions to the surface resistance depend on temperature, applied RF magnetic field and frequency. Furthermore measurements of the maximum RF magnetic field as a function of temperature and frequency in pulsed and CW operation are presented.

Slides WEIOA04 [1.857 MB]

THIOA06

Mechanical Design Considerations for β=1 Cavities

650

O. Capatina, G. Arnau-Izquierdo, S. Atieh, I. Aviles Santillana, S. Calatroni, A. D'Elia, R. Garoby, T. Junginger, D. Maciocha, E. Montesinos, V. Parma, T. Renaglia, T. Tardy, N. Valverde Alonso, W. Weingarten
CERN, Geneva, Switzerland
S. Chel, G. Devanz, J. Plouin
CEA/DSM/IRFU, France

The Superconducting Proton Linac (SPL) is an R&D effort coordinated by CERN in partnership with other international laboratories, aimed at developing key technologies for the construction of a multi-megawatt proton linac based on state-of-the-art RF superconducting technology, which would serve as a driver for new physics facilities such as neutrinos and Radioactive Ion Beam (RIB). Amongst the main objectives of this R&D effort, is the development of 704 MHz bulk niobium β=1 elliptical cavities, operating at 2 K with a maximum accelerating field of 25 MV/m, and the testing of a string of cavities integrated in a machine-type cryomodule. The R&D program concerning the elliptical β=1 cavities fabricated from niobium sheets explores new mechanical design and new fabrication methods. The paper presents several opportunities for design optimization that were identified. A comparison between stainless steel helium vessel and titanium helium vessel including Nb to Ti transitions is addressed. Different mechanical design aspects, including cryogenic considerations, and fabrication aspects were analyzed and the results are discussed.

Slides THIOA06 [5.292 MB]

THPO026

Second Sound Measurement for SPL Cavity Diagnostics

767

K.C. Liao, C. Balle, J. Bremer, T. Junginger, W. Vollenberg, W. Weingarten
CERN, Geneva, Switzerland
H. Vennekate
University of Göttingen, Georg-August University of Göttingen, Göttingen, Germany

Second sound is a temperature wave which travels at a speed of ≈ 20m/s in superfluid helium. The second sound detector used is a so-called oscillating superleak transducer (OST), initially provided by Cornell-CLASSE, and thereafter manufactured at CERN. It contains a flexible porous membrane for transmitting and blocking the movement of the superfluid and normal fluid components of the second sound wave. From the measured speed of this wave and by determining the travel time between the quench event and several OSTs, an alternative method is offered to localise the quench site by triangulation. Several surface mount devices (SMDs) – thick film chip resistors – are used to simulate the quench spot in a cavity. Given the heat pulse and the location of the installed OSTs, the temperature dependence of the second sound velocity is determined under different experimental conditions and compared with previous results and theoretical expectations. The second sound triangulation will eventually be used to determine quench locations on the Superconducting Proton Linac (SPL) test cavities (704MHz) at CERN.

Poster THPO026 [2.544 MB]

Paper	Title	Page
WEIOA04	Review of RF‐Sample‐Test Equipment and Results	579
	T. Junginger, W. Weingarten CERN, Geneva, Switzerland T. Junginger MPI-K, Heidelberg, Germany C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: Work supported by the German Doctoral Students program of the Federal Ministry of Education and Research (BMBF) The surface resistance of superconducting samples can be derived from the heat dissipation under RF exposure. This requires challenging and sometimes opposing design constraints. The samples shall be small and easily exchangeable. The RF magnetic field on the sample surface shall be large and homogeneous. It must not be limited by the host cavity. A calorimetric technique enables precise measurements and has therefore recently gained much interest. One of the devices exploiting this technique at multiple frequencies is the Quadrupole Resonator. Its measurement capabilities and limitations are discussed and compared with similar devices. Results on bulk niobium and niobium film on copper samples are presented. It is shown how different contributions to the surface resistance depend on temperature, applied RF magnetic field and frequency. Furthermore measurements of the maximum RF magnetic field as a function of temperature and frequency in pulsed and CW operation are presented.
	Slides WEIOA04 [1.857 MB]

THIOA06	Mechanical Design Considerations for β=1 Cavities	650
	O. Capatina, G. Arnau-Izquierdo, S. Atieh, I. Aviles Santillana, S. Calatroni, A. D'Elia, R. Garoby, T. Junginger, D. Maciocha, E. Montesinos, V. Parma, T. Renaglia, T. Tardy, N. Valverde Alonso, W. Weingarten CERN, Geneva, Switzerland S. Chel, G. Devanz, J. Plouin CEA/DSM/IRFU, France
	The Superconducting Proton Linac (SPL) is an R&D effort coordinated by CERN in partnership with other international laboratories, aimed at developing key technologies for the construction of a multi-megawatt proton linac based on state-of-the-art RF superconducting technology, which would serve as a driver for new physics facilities such as neutrinos and Radioactive Ion Beam (RIB). Amongst the main objectives of this R&D effort, is the development of 704 MHz bulk niobium β=1 elliptical cavities, operating at 2 K with a maximum accelerating field of 25 MV/m, and the testing of a string of cavities integrated in a machine-type cryomodule. The R&D program concerning the elliptical β=1 cavities fabricated from niobium sheets explores new mechanical design and new fabrication methods. The paper presents several opportunities for design optimization that were identified. A comparison between stainless steel helium vessel and titanium helium vessel including Nb to Ti transitions is addressed. Different mechanical design aspects, including cryogenic considerations, and fabrication aspects were analyzed and the results are discussed.
	Slides THIOA06 [5.292 MB]

THPO026	Second Sound Measurement for SPL Cavity Diagnostics	767
	K.C. Liao, C. Balle, J. Bremer, T. Junginger, W. Vollenberg, W. Weingarten CERN, Geneva, Switzerland H. Vennekate University of Göttingen, Georg-August University of Göttingen, Göttingen, Germany
	Second sound is a temperature wave which travels at a speed of ≈ 20m/s in superfluid helium. The second sound detector used is a so-called oscillating superleak transducer (OST), initially provided by Cornell-CLASSE, and thereafter manufactured at CERN. It contains a flexible porous membrane for transmitting and blocking the movement of the superfluid and normal fluid components of the second sound wave. From the measured speed of this wave and by determining the travel time between the quench event and several OSTs, an alternative method is offered to localise the quench site by triangulation. Several surface mount devices (SMDs) – thick film chip resistors – are used to simulate the quench spot in a cavity. Given the heat pulse and the location of the installed OSTs, the temperature dependence of the second sound velocity is determined under different experimental conditions and compared with previous results and theoretical expectations. The second sound triangulation will eventually be used to determine quench locations on the Superconducting Proton Linac (SPL) test cavities (704MHz) at CERN.
	Poster THPO026 [2.544 MB]