SRF2013 - List of Authors (Sievers, S.T.)

Paper	Title	Page
MOP082	Development and Test of a New Cryostat Module for the Injector of the S-DALINAC*	334
	T. Kürzeder, J. Conrad, F. Hug, N. Pietralla, A. Richter, S.T. Sievers TU Darmstadt, Darmstadt, Germany R.G. Eichhorn Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: *This work is supported by the DFG through the Collaborative Research Center SFB 634. The present injector of the superconducting Darmstadt electron linear accelerator S-DALINAC provides an electron beam of up to 10 MeV kinetic energy and up to 60 μA current in continuous wave operation. A new cryostat module has been constructed to replace the actual one in order to provide higher beam energies of up to 14 MeV and currents of up to 250 μA for nuclear resonance fluorescence experiments at the Darmstadt High Intensity Photon Setup (DHIPS). As before two 20-cell superconducting microwave cavities will be operated at an acceleration frequency of 3 GHz in a liquid helium bath at 2 K. For the injector upgrade two new elliptical 20-cell niobium cavities were also manufactured and in addition a third spare one. The rf power is transferred to the cavities by an also newly developed waveguide-transition line and input couplers. We report on the construction of the cryostat module and its components and present the results of a first cooling-down procedure.

TUP106	Second-Sound Measurements on a 3 GHz SRF Cavity at Low Acceleration Fields*	728
	S.T. Sievers, U. Bonnes, C. Burandt, F. Hug, T. Kürzeder, N. Pietralla, A. Richter TU Darmstadt, Darmstadt, Germany
	Funding: *This work is supported by the DFG through the Collaborative Research Center SFB 634. The superconducting Darmstadt electron linear accelerator S-DALINAC uses 20-cell niobium cavities that are operated at a microwave frequency of 3 GHz in liquid helium at a temperature of 2 K. This operation temperature is well below TC = 9.25 K of niobium and guarantees superconducting condition in routine operation. Occasional surface impurities, in particular after venting the beamline following maintenance work, can lead to local quenches which destroy superconductivity of the cavity. In such events it is desirable to have a method for locating and eliminating these surface impurities. In order to locate quench sites in the superconducting cavities during operation in liquid helium a set-up of oscillating superleak transducers (OSTs) was tested in a vertical bath cryostat on a cavity known to quench at very small accelerating fields. Despite the low rf power of approximately 4 W needed to quench the cavity, we were able to identify the quench sites with the OST set-up. Subsequent optical inspection clearly showed surface damages at the determined positions. We will report on our set-up and the procedure.

Paper

Title

Page

Development and Test of a New Cryostat Module for the Injector of the S-DALINAC*

334

T. Kürzeder, J. Conrad, F. Hug, N. Pietralla, A. Richter, S.T. Sievers
TU Darmstadt, Darmstadt, Germany
R.G. Eichhorn
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: *This work is supported by the DFG through the Collaborative Research Center SFB 634.
The present injector of the superconducting Darmstadt electron linear accelerator S-DALINAC provides an electron beam of up to 10 MeV kinetic energy and up to 60 μA current in continuous wave operation. A new cryostat module has been constructed to replace the actual one in order to provide higher beam energies of up to 14 MeV and currents of up to 250 μA for nuclear resonance fluorescence experiments at the Darmstadt High Intensity Photon Setup (DHIPS). As before two 20-cell superconducting microwave cavities will be operated at an acceleration frequency of 3 GHz in a liquid helium bath at 2 K. For the injector upgrade two new elliptical 20-cell niobium cavities were also manufactured and in addition a third spare one. The rf power is transferred to the cavities by an also newly developed waveguide-transition line and input couplers. We report on the construction of the cryostat module and its components and present the results of a first cooling-down procedure.

TUP106

Second-Sound Measurements on a 3 GHz SRF Cavity at Low Acceleration Fields*

728

S.T. Sievers, U. Bonnes, C. Burandt, F. Hug, T. Kürzeder, N. Pietralla, A. Richter
TU Darmstadt, Darmstadt, Germany

Funding: *This work is supported by the DFG through the Collaborative Research Center SFB 634.
The superconducting Darmstadt electron linear accelerator S-DALINAC uses 20-cell niobium cavities that are operated at a microwave frequency of 3 GHz in liquid helium at a temperature of 2 K. This operation temperature is well below TC = 9.25 K of niobium and guarantees superconducting condition in routine operation. Occasional surface impurities, in particular after venting the beamline following maintenance work, can lead to local quenches which destroy superconductivity of the cavity. In such events it is desirable to have a method for locating and eliminating these surface impurities. In order to locate quench sites in the superconducting cavities during operation in liquid helium a set-up of oscillating superleak transducers (OSTs) was tested in a vertical bath cryostat on a cavity known to quench at very small accelerating fields. Despite the low rf power of approximately 4 W needed to quench the cavity, we were able to identify the quench sites with the OST set-up. Subsequent optical inspection clearly showed surface damages at the determined positions. We will report on our set-up and the procedure.