IPAC2015 - List of Authors (Chiggiato, P.)

Paper	Title	Page
MOPJE071	New Electron Cloud Detectors for the CERN Proton Synchrotron	476
	C. Yin Vallgren, P. Chiggiato, S.S. Gilardoni, H. Neupert, M. Taborelli CERN, Geneva, Switzerland
	Electron cloud (EC) has already been observed during normal operation of the PS using classical shielded button pick-up detectors in drift sections. In the context of the LHC Injector Upgrade (LIU project), similar measurements are also needed for the combined function magnets of the machine, where the access to the vacuum chamber is strongly limited by the presence of the yoke. Two new electron cloud detectors have been studied, developed, and installed during the Long Shutdown (LS1) in one of such magnets. The first is based on current measurement by using a shielded button-type pick-up with a special geometry to reach the bottom surface of the vacuum pipe embedded in the magnet. The second one relies on a newly developed measurement method based on detection of the photons, which are emitted by cathodoluminescence from the electron cloud impinging on the vacuum chamber walls. Part of the emitted photons is collected through a quartz window by a Micro-Channel Plate Photomultiplier Tube (MCP-PMT). First results obtained during machine development runs show the feasibility of the photon detection scheme. The results are discussed and compared with pick-up measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE071
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WEPHA003	Measurement of NEG Coating Performance Variation in the LHC after the First Long Shutdown	3100
	V. Bencini, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan, C. Yin Vallgren CERN, Geneva, Switzerland
	During the Long Shutdown 1 (LS1) of the Large Hadron Collider, 90% of the Non-Evaporable Getter (NEG) coated beam pipes in the Long Straight Sections (LSS) were vented to undertake the planned upgrade and consolidation programmes. After each intervention, an additional bake-out and NEG activation were performed to reach the vacuum requirements. An analysis of the coating performance variation after the additional activation cycle has been carried out by using ultimate pressure and pressure build-up measurements. In addition, laboratory measurements have been carried out to mimic the LHC coated beam pipe behaviour. The experimental data have been compared with calculation obtained by Molflow+.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA003
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WEPHA004	Present Quality Assurance for the LHC Beam Vacuum System and its Future Improvement	3103
	J. Sestak, V. Baglin, G. Bregliozzi, P. Chiggiato CERN, Geneva, Switzerland
	During the Long Shutdown 1 (LS1), the LHC beam vacuum system was upgraded to minimize dynamic vacuum effects like stimulated desorption and beam-induced electron multipacting. A quality assurance plan was mandatory due to the demanding vacuum performance and the limited access to the equipment during the following operation period. Laboratory assessment tests and underground interventions were performed following well-defined and approved procedures. All vacuum related activities were documented and written reports stored in dedicated databases. Quality controls were performed to find mechanical, cabling and equipment functionality non-conformities. Possible issues were identified, classified and tracked in a non-conformity database for future corrective actions. This contribution give an overview of the quality assurance policy followed during the LS1 and the non-conformities reported after quality control. Possible future improvements are also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA004
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WEPHA005	Characterization of the RF Fingers Contact Force for the LHC Warm Vacuum Bellow Modules	3106
	C. Blanch Gutiérrez, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan CERN, Geneva, Switzerland
	Along the 27 Km of LHC beam pipe, various types of vacuum bellow modules are needed to compensate the mechanical misalignments of the vacuum chambers during installation and to absorb their thermal expansion during the bake-out. In order to reduce the beam impedance during operation with beams these modules are equipped with RF bridges to carry the image current. They are usually made out of a copper tube insert at one side and Cu-Be RF fingers at the other end of the module. A spring is used to keep the contact between the RF fingers and the tube insert. The geometry and the choice of this spring become critical to ensure a good electrical contact. In this paper, a description of the test bench used to measure the contact force together with the procedure applied and the measurements performed are given. A summary of the maximum radial and axial offsets between the RF fingers and the insert tube while keeping a good electrical contact is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA005
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WEPHA006	Recommissioning of the COLDEX Experiment at CERN	3109
	R. Salemme, V. Baglin, F. Bellorini, G. Bregliozzi, K. Brodzinski, P. Chiggiato, P. Costa Pinto, P. Gomes, A. Gutierrez, V. Inglese, B. Jenninger, R. Kersevan, E. Michel, M. Pezzetti, B. Rio, A. Sapountzis CERN, Geneva, Switzerland
	COLDEX (Cold bore Experiment), installed in the Super Proton Synchrotron (SPS) at CERN, is a test vacuum sector used in 2001-2004 to validate the Large Hadron Collider (LHC) cryogenic vacuum system with LHC type proton beams. Its cryostat houses a 2.2 m long copper perforated beam screen surrounded by a stainless steel cold bore, both individually temperature controlled down to 5 and 3 K, respectively. In the framework of the development for the High Luminosity upgrade of the LHC (HL-LHC), COLDEX has been re-commissioned in 2014. The objective of this re-commissioning is the validation of the performance of amorphous carbon coatings at cryogenic temperature with LHC type beams. The existing COLDEX beam screen has been dismounted and carbon coated, while a complete overhaul of the vacuum, cryogenic and control systems has been carried out. This contribution describes the phases of re-commissioning and reviews the current experimental set-up. An overview of the possible measurements with COLDEX, in view of its HL-LHC experimental program, is also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA006
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WEPHA007	Amorphous Carbon Coatings at Cryogenic Temperatures with LHC Type Beams: First Results with the COLDEX Experiment	3112
	R. Salemme, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan CERN, Geneva, Switzerland
	Extrapolations of electron cloud data from the Large Hadron Collider (LHC) Run 1 to the High Luminosity upgrade (HL-LHC) beam parameters predict an intolerable increase of heat load on the beam screens of the inner triplets. Amorphous carbon (a-C) coating of the beam screen surface is proposed to reduce electron cloud production, thereby minimising its dissipated power. To validate this solution, the COLDEX experiment has been re-commissioned. Such equipment mimics the performance of the LHC cold bore and beam screen cryogenic vacuum system in presence of LHC beams in the Super Proton Synchrotron (SPS). The main objective of the study is the performance evaluation of a-C coatings while operating the beam screen in the 10 to 60 K temperature range and cold bore below 3 K. This paper reviews the status of COLDEX and the results obtained during its first experimental runs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA007
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WEPHA011	Photodesorption and Electron Yield Measurements of Thin Film Coatings for Future Accelerators	3123
	R. Kersevan, M. Ady, P. Chiggiato CERN, Geneva, Switzerland T. Honda, Y. Tanimoto KEK, Tsukuba, Japan
	The performance of future accelerators could be limited by electron cloud phenomena and high photodesorption yields. For such a reason, the study of secondary electron and photodesorption yields of vacuum materials is essential. The eradication or mitigation of both secondary electron and molecule desorption could strongly reduce the beam scrubbing time and increase the availability of nominal beams for experiments. Surface modifications with the desired characteristics can be achieved by thin-film coatings, in particular made of amorphous carbon and non-evaporable getters (NEG). In the framework of a new collaboration, several vacuum chambers have been produced, and different coatings on each of them have been applied. The samples were then irradiated at KEK’s Photon Factory with SR light of 4 keV critical energy during several days, allowing the measurement of the photodesorption yield as a function of the photon dose. This paper presents the experiment and briefly summarizes the preliminary photodesorption and photoelectron yield data of different coatings. The results can be used for future machine design with similar conditions, such as the FCC-hh.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA011
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Paper

Title

Page

New Electron Cloud Detectors for the CERN Proton Synchrotron

476

C. Yin Vallgren, P. Chiggiato, S.S. Gilardoni, H. Neupert, M. Taborelli
CERN, Geneva, Switzerland

Electron cloud (EC) has already been observed during normal operation of the PS using classical shielded button pick-up detectors in drift sections. In the context of the LHC Injector Upgrade (LIU project), similar measurements are also needed for the combined function magnets of the machine, where the access to the vacuum chamber is strongly limited by the presence of the yoke. Two new electron cloud detectors have been studied, developed, and installed during the Long Shutdown (LS1) in one of such magnets. The first is based on current measurement by using a shielded button-type pick-up with a special geometry to reach the bottom surface of the vacuum pipe embedded in the magnet. The second one relies on a newly developed measurement method based on detection of the photons, which are emitted by cathodoluminescence from the electron cloud impinging on the vacuum chamber walls. Part of the emitted photons is collected through a quartz window by a Micro-Channel Plate Photomultiplier Tube (MCP-PMT). First results obtained during machine development runs show the feasibility of the photon detection scheme. The results are discussed and compared with pick-up measurements.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE071

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA003

Measurement of NEG Coating Performance Variation in the LHC after the First Long Shutdown

3100

V. Bencini, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan, C. Yin Vallgren
CERN, Geneva, Switzerland

During the Long Shutdown 1 (LS1) of the Large Hadron Collider, 90% of the Non-Evaporable Getter (NEG) coated beam pipes in the Long Straight Sections (LSS) were vented to undertake the planned upgrade and consolidation programmes. After each intervention, an additional bake-out and NEG activation were performed to reach the vacuum requirements. An analysis of the coating performance variation after the additional activation cycle has been carried out by using ultimate pressure and pressure build-up measurements. In addition, laboratory measurements have been carried out to mimic the LHC coated beam pipe behaviour. The experimental data have been compared with calculation obtained by Molflow+.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA003

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA004

Present Quality Assurance for the LHC Beam Vacuum System and its Future Improvement

3103

J. Sestak, V. Baglin, G. Bregliozzi, P. Chiggiato
CERN, Geneva, Switzerland

During the Long Shutdown 1 (LS1), the LHC beam vacuum system was upgraded to minimize dynamic vacuum effects like stimulated desorption and beam-induced electron multipacting. A quality assurance plan was mandatory due to the demanding vacuum performance and the limited access to the equipment during the following operation period. Laboratory assessment tests and underground interventions were performed following well-defined and approved procedures. All vacuum related activities were documented and written reports stored in dedicated databases. Quality controls were performed to find mechanical, cabling and equipment functionality non-conformities. Possible issues were identified, classified and tracked in a non-conformity database for future corrective actions. This contribution give an overview of the quality assurance policy followed during the LS1 and the non-conformities reported after quality control. Possible future improvements are also discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA004

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA005

Characterization of the RF Fingers Contact Force for the LHC Warm Vacuum Bellow Modules

3106

C. Blanch Gutiérrez, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan
CERN, Geneva, Switzerland

Along the 27 Km of LHC beam pipe, various types of vacuum bellow modules are needed to compensate the mechanical misalignments of the vacuum chambers during installation and to absorb their thermal expansion during the bake-out. In order to reduce the beam impedance during operation with beams these modules are equipped with RF bridges to carry the image current. They are usually made out of a copper tube insert at one side and Cu-Be RF fingers at the other end of the module. A spring is used to keep the contact between the RF fingers and the tube insert. The geometry and the choice of this spring become critical to ensure a good electrical contact. In this paper, a description of the test bench used to measure the contact force together with the procedure applied and the measurements performed are given. A summary of the maximum radial and axial offsets between the RF fingers and the insert tube while keeping a good electrical contact is presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA005

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA006

Recommissioning of the COLDEX Experiment at CERN

3109

R. Salemme, V. Baglin, F. Bellorini, G. Bregliozzi, K. Brodzinski, P. Chiggiato, P. Costa Pinto, P. Gomes, A. Gutierrez, V. Inglese, B. Jenninger, R. Kersevan, E. Michel, M. Pezzetti, B. Rio, A. Sapountzis
CERN, Geneva, Switzerland

COLDEX (Cold bore Experiment), installed in the Super Proton Synchrotron (SPS) at CERN, is a test vacuum sector used in 2001-2004 to validate the Large Hadron Collider (LHC) cryogenic vacuum system with LHC type proton beams. Its cryostat houses a 2.2 m long copper perforated beam screen surrounded by a stainless steel cold bore, both individually temperature controlled down to 5 and 3 K, respectively. In the framework of the development for the High Luminosity upgrade of the LHC (HL-LHC), COLDEX has been re-commissioned in 2014. The objective of this re-commissioning is the validation of the performance of amorphous carbon coatings at cryogenic temperature with LHC type beams. The existing COLDEX beam screen has been dismounted and carbon coated, while a complete overhaul of the vacuum, cryogenic and control systems has been carried out. This contribution describes the phases of re-commissioning and reviews the current experimental set-up. An overview of the possible measurements with COLDEX, in view of its HL-LHC experimental program, is also presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA006

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA007

Amorphous Carbon Coatings at Cryogenic Temperatures with LHC Type Beams: First Results with the COLDEX Experiment

3112

R. Salemme, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan
CERN, Geneva, Switzerland

Extrapolations of electron cloud data from the Large Hadron Collider (LHC) Run 1 to the High Luminosity upgrade (HL-LHC) beam parameters predict an intolerable increase of heat load on the beam screens of the inner triplets. Amorphous carbon (a-C) coating of the beam screen surface is proposed to reduce electron cloud production, thereby minimising its dissipated power. To validate this solution, the COLDEX experiment has been re-commissioned. Such equipment mimics the performance of the LHC cold bore and beam screen cryogenic vacuum system in presence of LHC beams in the Super Proton Synchrotron (SPS). The main objective of the study is the performance evaluation of a-C coatings while operating the beam screen in the 10 to 60 K temperature range and cold bore below 3 K. This paper reviews the status of COLDEX and the results obtained during its first experimental runs.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA007

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPHA011

Photodesorption and Electron Yield Measurements of Thin Film Coatings for Future Accelerators

3123

R. Kersevan, M. Ady, P. Chiggiato
CERN, Geneva, Switzerland
T. Honda, Y. Tanimoto
KEK, Tsukuba, Japan

The performance of future accelerators could be limited by electron cloud phenomena and high photodesorption yields. For such a reason, the study of secondary electron and photodesorption yields of vacuum materials is essential. The eradication or mitigation of both secondary electron and molecule desorption could strongly reduce the beam scrubbing time and increase the availability of nominal beams for experiments. Surface modifications with the desired characteristics can be achieved by thin-film coatings, in particular made of amorphous carbon and non-evaporable getters (NEG). In the framework of a new collaboration, several vacuum chambers have been produced, and different coatings on each of them have been applied. The samples were then irradiated at KEK’s Photon Factory with SR light of 4 keV critical energy during several days, allowing the measurement of the photodesorption yield as a function of the photon dose. This paper presents the experiment and briefly summarizes the preliminary photodesorption and photoelectron yield data of different coatings. The results can be used for future machine design with similar conditions, such as the FCC-hh.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA011

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)