SRF2015 - List of Keywords (collider)

Paper	Title	Other Keywords	Page
MOPB058	Field Emission From a Thermally Oxidized Nb Sample	site, vacuum, linear-collider, high-voltage	233
	S. Lagotzky, G. Müller Bergische Universität Wuppertal, Wuppertal, Germany
	Funding: This work was funded by BMBF project 05H12PX6. Enhanced field emission (EFE) from particulates and surface defects is one of the main field limitations of superconducting Nb cavities required for XFEL and ILC. The activation field Eact of such emitters and the emitter number density N at a given Eact is strongly influenced by the thickness of the Nb oxide layer. Combination of this effect with surface cleaning techniques, e.g. dry ice cleaning (DIC), potentially shifts the onset of EFE to even higher Eact. Therefore, we have started to investigate a single crystal Nb sample after thermal oxidation (TO) by a heat treatment (HT) in air (T = 360°C, t = 40 min). Field emission maps showed a first emitter at 100 MV/m, and N = 30/cm² at 225 MV/m. SEM analysis of the 10 strongest emitters revealed mainly surface defects and one particulate. Subsequent removal of the oxide by a HT (T = 400°C, t = 1 h) under UHV resulted in an EFE onset at 75 MV/m and increased N to 60/cm² at 225 MV/m. In a second step the TO as well as the measurement was repeated after DIC of the surface. The resulting field maps and the SEM analysis of selected emitters will be reported. A.T. Wu et al., MOPC118, IPAC11.
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MOPB070	Preliminary Conceptual Design of the CEPC SRF System	cavity, HOM, SRF, booster	272
	J.Y. Zhai, J. Gao, T.M. Huang, Z.C. Liu, Z.H. Mi, P. Sha, Y. Sun, H.J. Zheng IHEP, Beijing, People's Republic of China S.A. Belomestnykh BNL, Upton, Long Island, New York, USA S.A. Belomestnykh Stony Brook University, Stony Brook, USA C. Pagani INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	CEPC is a circular electron positron collider operating at 240 GeV center-of-mass energy as a Higgs factory, recently proposed by the Chinese high energy physics community. The CEPC study group, together with the FCC and ILC community, will contribute to the development of future high energy colliders and experiments which will ensure that the elementary particle physics remain a vibrant and exciting field of fundamental investigation for decades to come. Superconducting RF (SRF) system is one of the most important technical systems of CEPC and is a key to achieving its design energy and luminosity. It will dominate, with the associated RF power source and cryogenic system, the overall machine cost, efficiency and performance. The CEPC SRF system will be one of the largest and most powerful SRF accelerator installations in the world. The preliminary conceptual design of the CEPC SRF system is summarized in this paper, including the machine layout, key parameter choices and some critical issues such as HOM damping, emphasizing the new technology requirement and R&D focuses.
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TUPB052	HTS Coatings for Impedance Reduction of Beam-Induced RF Image Currents in the FCC	impedance, radiation, dipole, injection	695
	S. Calatroni CERN, Geneva, Switzerland
	The FCC-hh presently under study at CERN will make use of 16 T superconducting dipoles for achieving 100 TeV p-p center-of-mass collision energy in a 100 km ring collider. A copper coated beam screen, like in the LHC, is envisaged to shield the 1.9 K dipole cold bores from the 28 W/m/beam of synchrotron radiation. Operating temperature should be in the 50 K range, as best compromise temperature in order to minimize the wall-plug power consumption of the cryogenic system. However, preliminary studies indicate that copper at 50 K might not provide low enough beam coupling impedance in the FCC-hh. It has then been proposed to reduce the beam impedance by a thin layer of a High-Temperature Superconductor (HTS), which will thus effectively shield the beam-induced RF image currents. Purpose of this paper is to define the basic requirements for an HTS film in the RF field induced by beam image currents and exposed to a high magnetic field, and to identify the best candidate materials and coating processes.
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FRBA04	SRF for Future Circular Colliders	cavity, radiation, HOM, proton	1474
	R. Calaga, O. Brunner, A.C. Butterworth, E. Jensen CERN, Geneva, Switzerland
	The future circular colliders (FCC) will require superconducting RF systems for the proton-proton, electron-positron and lepton-hadron modes of the collider operation. The SCRF systems will accelerate the protons beams to 50 TeV and the lepton beams from 45.5 to 175 GeV in a staged approach with a possible 60 GeV energy recovery linac for the lepton-hadron to option as an intermediate step. The expected stored beam currents in some modes exceed 1 A with very short bunch lengths. A first conceptual design of the FCC RF system is proposed along with highlights of specfic R&D topics to reach the design performance. Challenges related to RF structure design, intensity limitations due to beam loading, RF powering and higher order modes are addressed. Synergies between the different collider modes and the present LHC are identified.
	Slides FRBA04 [2.699 MB]
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Paper

Title

Other Keywords

Page

MOPB058

Field Emission From a Thermally Oxidized Nb Sample

site, vacuum, linear-collider, high-voltage

233

S. Lagotzky, G. Müller
Bergische Universität Wuppertal, Wuppertal, Germany

Funding: This work was funded by BMBF project 05H12PX6.
Enhanced field emission (EFE) from particulates and surface defects is one of the main field limitations of superconducting Nb cavities required for XFEL and ILC. The activation field Eact of such emitters and the emitter number density N at a given Eact is strongly influenced by the thickness of the Nb oxide layer*. Combination of this effect with surface cleaning techniques, e.g. dry ice cleaning (DIC), potentially shifts the onset of EFE to even higher Eact. Therefore, we have started to investigate a single crystal Nb sample after thermal oxidation (TO) by a heat treatment (HT) in air (T = 360°C, t = 40 min). Field emission maps showed a first emitter at 100 MV/m, and N = 30/cm² at 225 MV/m. SEM analysis of the 10 strongest emitters revealed mainly surface defects and one particulate. Subsequent removal of the oxide by a HT (T = 400°C, t = 1 h) under UHV resulted in an EFE onset at 75 MV/m and increased N to 60/cm² at 225 MV/m. In a second step the TO as well as the measurement was repeated after DIC of the surface. The resulting field maps and the SEM analysis of selected emitters will be reported.
*A.T. Wu et al., MOPC118, IPAC11.

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MOPB070

Preliminary Conceptual Design of the CEPC SRF System

cavity, HOM, SRF, booster

272

J.Y. Zhai, J. Gao, T.M. Huang, Z.C. Liu, Z.H. Mi, P. Sha, Y. Sun, H.J. Zheng
IHEP, Beijing, People's Republic of China
S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh
Stony Brook University, Stony Brook, USA
C. Pagani
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

CEPC is a circular electron positron collider operating at 240 GeV center-of-mass energy as a Higgs factory, recently proposed by the Chinese high energy physics community. The CEPC study group, together with the FCC and ILC community, will contribute to the development of future high energy colliders and experiments which will ensure that the elementary particle physics remain a vibrant and exciting field of fundamental investigation for decades to come. Superconducting RF (SRF) system is one of the most important technical systems of CEPC and is a key to achieving its design energy and luminosity. It will dominate, with the associated RF power source and cryogenic system, the overall machine cost, efficiency and performance. The CEPC SRF system will be one of the largest and most powerful SRF accelerator installations in the world. The preliminary conceptual design of the CEPC SRF system is summarized in this paper, including the machine layout, key parameter choices and some critical issues such as HOM damping, emphasizing the new technology requirement and R&D focuses.

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

TUPB052

HTS Coatings for Impedance Reduction of Beam-Induced RF Image Currents in the FCC

impedance, radiation, dipole, injection

695

S. Calatroni
CERN, Geneva, Switzerland

The FCC-hh presently under study at CERN will make use of 16 T superconducting dipoles for achieving 100 TeV p-p center-of-mass collision energy in a 100 km ring collider. A copper coated beam screen, like in the LHC, is envisaged to shield the 1.9 K dipole cold bores from the 28 W/m/beam of synchrotron radiation. Operating temperature should be in the 50 K range, as best compromise temperature in order to minimize the wall-plug power consumption of the cryogenic system. However, preliminary studies indicate that copper at 50 K might not provide low enough beam coupling impedance in the FCC-hh. It has then been proposed to reduce the beam impedance by a thin layer of a High-Temperature Superconductor (HTS), which will thus effectively shield the beam-induced RF image currents. Purpose of this paper is to define the basic requirements for an HTS film in the RF field induced by beam image currents and exposed to a high magnetic field, and to identify the best candidate materials and coating processes.

Export •

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

FRBA04

SRF for Future Circular Colliders

cavity, radiation, HOM, proton

1474

R. Calaga, O. Brunner, A.C. Butterworth, E. Jensen
CERN, Geneva, Switzerland

The future circular colliders (FCC) will require superconducting RF systems for the proton-proton, electron-positron and lepton-hadron modes of the collider operation. The SCRF systems will accelerate the protons beams to 50 TeV and the lepton beams from 45.5 to 175 GeV in a staged approach with a possible 60 GeV energy recovery linac for the lepton-hadron to option as an intermediate step. The expected stored beam currents in some modes exceed 1 A with very short bunch lengths. A first conceptual design of the FCC RF system is proposed along with highlights of specfic R&D topics to reach the design performance. Challenges related to RF structure design, intensity limitations due to beam loading, RF powering and higher order modes are addressed. Synergies between the different collider modes and the present LHC are identified.

Slides FRBA04 [2.699 MB]

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