SRF2011 - List of Authors (Kugeler, O.)

Paper

Title

Page

RF and SRF Layout of BERLinPro

53

W. Anders, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, A. Neumann
HZB, Berlin, Germany

Funding: Work funded by the Bundesministerium für Bildung und Forschung and Land Berlin
The ERL project BERLinPro is funded and now in the design phase. The planned SRF layout is described including the RF transmitters, the cryogenic installations and the configuration of the SRF modules.

Poster MOPO008 [1.552 MB]

MOPO067

CW Measurements of Cornell LLRF System at HoBiCaT

262

A. Neumann, W. Anders, R. Görgen, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA
J. Dobbins, R.P.K. Kaplan, M. Liepe, C.R. Strohman
CLASSE, Ithaca, New York, USA

Funding: Work funded by the Bundesministerium für Bildung und Forschung and Land Berlin.
In Energy Recovery Linacs, such as the Cornell ERL or BERLinPro, the main linac cavities are operated in CW at low beam-loading. The choice of the external Q is given by two competing factors: The achievable field stability and the maximum provided RF power. To determine the optimum external Q, LLRF measurements with the Cornell system were performed at HoBiCaT to study the field stability at given microphonics detuning of a TESLA cavity for different gain settings and external Q values. Stable operation at external Q up to 2·10⁸ was demonstrated with field's phase stability of 0.02 degrees.

THPO006

Study of Trapped Magnetic Flux in Superconducting Niobium Samples

702

S. Aull, J. Knobloch, O. Kugeler
HZB, Berlin, Germany

Trapped magnetic flux is known to be one cause of residual losses in an SRF cavity. An ambient magnetic field is trapped in the material when lattice defects inhibit the expulsion of the field during the transition into the Meissner phase. We measured the fraction of trapped magnetic flux in niobium samples with different treatment histories, such as BCP and tempering. The differences between single crystal and polycrystalline material as well as the influence of local temperature gradients and different cooling rates were investigated. In addition, the progression of the release of a trapped field during warm up was studied. It was found that different fractions of an applied field were trapped due to heat treatment. Differences between single crystal and polycrystalline material were also observed. Additionally, single crystal samples showed a logarithmic dependency on the cooling rate. It was demonstrated that a local temperature gradient produces an additional magnetic field which has impact on the flux trapping.

Poster THPO006 [1.436 MB]

THPO011

Improving the Intrinsic Quality Factor of SRF Cavities by Thermal Cycling

724

O. Kugeler, W. Anders, J. Knobloch, A. Neumann
HZB, Berlin, Germany

We investigated the influence of the cooling gradients near Tc on the obtained Q0 values of a TESLA cavity. Measurements were performed in the HoBiCaT test stand by briefly warming the cavity above Tc via He depletion inside the cryovessel and subsequent cooling. The temperature was measured at different points at the cavity and the cryo-tank. It turned out that there is a correlation between obtained Q0 and the time lag between the first transition of a thermo-sensor through Tc and the last transition of a sensor though Tc which is interpreted as a local gradient. We have observed no correlation to the cooling speed, i.e. different temperature gradients in time. The findings could help explain the large fluctuations in measured Q values in different test-stands, and even open up pathways to devising a cooling scheme to obtain higher Q values “for free”.

FRIOA07

SRF Photoinjector Tests at HoBiCat

962

A. Neumann, W. Anders, R. Barday, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, A.N. Matveenko, T. Quast, J. Rudolph, S.G. Schubert, J. Völker
HZB, Berlin, Germany
P. Kneisel
JLAB, Newport News, Virginia, USA
G. Lorenz
FHI, Berlin, Germany
R. Nietubyc
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock, Poland
J.K. Sekutowicz
DESY, Hamburg, Germany
J. Smedley
BNL, Upton, Long Island, New York, USA
I. Will
MBI, Berlin, Germany

Funding: Work funded by the Bundesministerium für Bildung und Forschung and Land Berlin.
In collaboration with Jefferson Laboratory, DESY and the A. Soltan Institute HZB developed a fully superconducting RF photo-injector as a first step towards a high average current electron source for the BERLinPro ERL. This setup consists of a 1.6 cell superconducting gun cavity with a lead cathode plasma-arc deposited on the half cell backwall and a superconducting solenoid. The system, including a warm diagnostic beam-line section, was recently installed in the HoBiCaT test facility to study beam dynamics within the ERL parameter range. This paper will give an overview of the horizontal cavity tests, dark current studies and beam measurements.

Paper	Title	Page
MOPO008	RF and SRF Layout of BERLinPro	53
	W. Anders, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, A. Neumann HZB, Berlin, Germany
	Funding: Work funded by the Bundesministerium für Bildung und Forschung and Land Berlin The ERL project BERLinPro is funded and now in the design phase. The planned SRF layout is described including the RF transmitters, the cryogenic installations and the configuration of the SRF modules.
	Poster MOPO008 [1.552 MB]

MOPO067	CW Measurements of Cornell LLRF System at HoBiCaT	262
	A. Neumann, W. Anders, R. Görgen, J. Knobloch, O. Kugeler HZB, Berlin, Germany S.A. Belomestnykh BNL, Upton, Long Island, New York, USA J. Dobbins, R.P.K. Kaplan, M. Liepe, C.R. Strohman CLASSE, Ithaca, New York, USA
	Funding: Work funded by the Bundesministerium für Bildung und Forschung and Land Berlin. In Energy Recovery Linacs, such as the Cornell ERL or BERLinPro, the main linac cavities are operated in CW at low beam-loading. The choice of the external Q is given by two competing factors: The achievable field stability and the maximum provided RF power. To determine the optimum external Q, LLRF measurements with the Cornell system were performed at HoBiCaT to study the field stability at given microphonics detuning of a TESLA cavity for different gain settings and external Q values. Stable operation at external Q up to 2·10⁸ was demonstrated with field's phase stability of 0.02 degrees.

THPO006	Study of Trapped Magnetic Flux in Superconducting Niobium Samples	702
	S. Aull, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	Trapped magnetic flux is known to be one cause of residual losses in an SRF cavity. An ambient magnetic field is trapped in the material when lattice defects inhibit the expulsion of the field during the transition into the Meissner phase. We measured the fraction of trapped magnetic flux in niobium samples with different treatment histories, such as BCP and tempering. The differences between single crystal and polycrystalline material as well as the influence of local temperature gradients and different cooling rates were investigated. In addition, the progression of the release of a trapped field during warm up was studied. It was found that different fractions of an applied field were trapped due to heat treatment. Differences between single crystal and polycrystalline material were also observed. Additionally, single crystal samples showed a logarithmic dependency on the cooling rate. It was demonstrated that a local temperature gradient produces an additional magnetic field which has impact on the flux trapping.
	Poster THPO006 [1.436 MB]

THPO011	Improving the Intrinsic Quality Factor of SRF Cavities by Thermal Cycling	724
	O. Kugeler, W. Anders, J. Knobloch, A. Neumann HZB, Berlin, Germany
	We investigated the influence of the cooling gradients near Tc on the obtained Q0 values of a TESLA cavity. Measurements were performed in the HoBiCaT test stand by briefly warming the cavity above Tc via He depletion inside the cryovessel and subsequent cooling. The temperature was measured at different points at the cavity and the cryo-tank. It turned out that there is a correlation between obtained Q0 and the time lag between the first transition of a thermo-sensor through Tc and the last transition of a sensor though Tc which is interpreted as a local gradient. We have observed no correlation to the cooling speed, i.e. different temperature gradients in time. The findings could help explain the large fluctuations in measured Q values in different test-stands, and even open up pathways to devising a cooling scheme to obtain higher Q values “for free”.

FRIOA07	SRF Photoinjector Tests at HoBiCat	962
	A. Neumann, W. Anders, R. Barday, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, A.N. Matveenko, T. Quast, J. Rudolph, S.G. Schubert, J. Völker HZB, Berlin, Germany P. Kneisel JLAB, Newport News, Virginia, USA G. Lorenz FHI, Berlin, Germany R. Nietubyc The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock, Poland J.K. Sekutowicz DESY, Hamburg, Germany J. Smedley BNL, Upton, Long Island, New York, USA I. Will MBI, Berlin, Germany
	Funding: Work funded by the Bundesministerium für Bildung und Forschung and Land Berlin. In collaboration with Jefferson Laboratory, DESY and the A. Soltan Institute HZB developed a fully superconducting RF photo-injector as a first step towards a high average current electron source for the BERLinPro ERL. This setup consists of a 1.6 cell superconducting gun cavity with a lead cathode plasma-arc deposited on the half cell backwall and a superconducting solenoid. The system, including a warm diagnostic beam-line section, was recently installed in the HoBiCaT test facility to study beam dynamics within the ERL parameter range. This paper will give an overview of the horizontal cavity tests, dark current studies and beam measurements.