IPAC2016 - List of Authors (Auchmann, B.)

Paper	Title	Page
TUPMB038	Degradation of the Insulation of the LHC Main Dipole Cable when Exposed to High Temperatures	1186
	V. Raginel, B. Auchmann, D. Kleiven, R. Schmidt, A.P. Verweij, D. Wollmann CERN, Geneva, Switzerland
	Funding: Research supported by the High Luminosity LHC project The energy stored in the LHC beams is substantial and requires a complex machine protection system to protect the equipment. Despite efficient beam absorbers, several failure modes lead to some limited beam impact on superconducting magnets. Thus it is required to understand the damage mechanisms and limits of superconducting magnets due to instantaneous beam impact. This becomes even more important due to the future upgrade of CERNs injector chain for the LHC that will lead to an increase of the beam brightness. A roadmap to perform damage tests on magnet parts has been presented previously. The polyimide insulation of the superconducting cable is identified as one of the critical elements of the magnet. In this contribution, the experimental setup to measure the insulation degradation of LHC main dipole cables due to exposure to high temperature is described. Compressed stacks of insulated Nb-Ti cables have been exposed to a heat treatment within an Argon atmosphere. After each heat treatment, high-voltage measurements verified the dielectric strength of the insulation. The results of this experiment provide an upper damage limit of superconducting magnets due to beam impact. Experimental Setups to Determine the Damage Limit of Superconducting Magnets for Instantaneous Beam Losses, V. Raginel et al, IPAC'15
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMB038
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TUPMW006	Power Deposition in LHC Magnets Due to Bound-Free Pair Production in the Experimental Insertions	1418
	C. Bahamonde Castro, B. Auchmann, M.I. Besana, K. Brodzinski, R. Bruce, F. Cerutti, J.M. Jowett, A. Lechner, T. Mertens, V. Parma, S. Redaelli, M. Schaumann, N.V. Shetty, E. Skordis, G.E. Steele, R. van Weelderen CERN, Geneva, Switzerland
	The peak luminosity achieved during Pb-Pb collisions in the LHC in 2015 (3x1027cm^-2s⁻¹) well exceeded the design luminosity and is anticipated to increase by another factor 2 after the next Long Shutdown (2019- 2020). A significant fraction of the power dissipated in ultra-peripheral Pb-Pb collisions is carried by ions from bound-free pair production, which are lost in the dispersion suppressors adjacent to the experimental insertions. At higher luminosities, these ions risk to quench superconducting magnets and might limit their operation due to the dynamic heat load that needs to be evacuated by the cryogenic system. In this paper, we estimate the power deposition in superconducting coils and the magnet cold mass and we quantify the achievable reduction by deviating losses to less sensitive locations or by installing collimators at strategic positions. The second option is considered for the dispersion suppressor next to the ALICE insertion, where a selective displacement of losses to a magnet-free region is not possible.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW006
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TUPMW023	Macroparticle-Induced Losses During 6.5 TeV LHC Operation	1481
	G. Papotti, M. Albert, B. Auchmann, E.B. Holzer, M.K. Kalliokoski, A. Lechner CERN, Geneva, Switzerland
	One of the major performance limitations for operating the LHC at high energy was feared to be the so called UFOs (Unidentified Falling Objects, presumably micrometer sized dust particles which lead to fast beam losses when they interact with the beam). Indeed much higher rates were observed in 2015 compared to Run 1, and about 20 fills were prematurely terminated by too high losses caused by such events. Additionally they triggered a few beam induced quenches at high energy, the first in the history of the LHC. In this paper we review the latest update on the analysis of these events, e.g. the conditioning observed during the year and possible correlations with beam and machine parameters. At the same time we also review the optimization of beam loss monitor thresholds in terms of machine protection and availability.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW023
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TUPMW028	Bound-Free Pair Production in LHC Pb-Pb Operation at 6.37 Z TeV per Beam	1497
	J.M. Jowett, B. Auchmann, C. Bahamonde Castro, M.K. Kalliokoski, A. Lechner, T. Mertens, M. Schaumann, C. Xu CERN, Geneva, Switzerland
	In the 2015 Pb-Pb collision run of the LHC, the power of the secondary beams emitted from the interaction point by the bound-free pair production process reached new levels while the propensity of the bending magnets to quench is higher at the new magnetic field levels. This beam power is about 70 times greater than that contained in the luminosity debris and is focussed on a specific location. As long foreseen, orbit bumps were introduced in the dispersion suppressors around the highest luminosity experiments to mitigate the risk by displacing and spreading out these losses. An experiment designed to induce quenches and determine the quench levels and luminosity limit was carried out to assess the need for special collimators to intercept these secondary beams.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW028
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THPOY044	Experimental Setup to Measure the Damage Limits of Superconducting Magnets due to Beam Impact at CERN's HiRadMat Facility	4200
	D. Kleiven Kleiven, David, Geneva, Switzerland B. Auchmann, V. Raginel, R. Schmidt, A.P. Verweij, D. Wollmann CERN, Geneva, Switzerland
	Funding: Research supported by the High Luminosity LHC project The future upgrade of CERN's injector chain for the Large Hadron Collider (LHC) will lead to an increase of the beam brightness in the LHC. Beam absorbers are capturing missteered beams, but some limited beam impact on superconducting magnets can hardly be avoided. Therefore, it is planned to measure the damage limits of superconducting magnet components due to beam impact at CERN's HiRad- Mat facility using the 440 GeV proton beam from the Super Proton Synchrotron. Two experiments are proposed. One at ambient and one at cryogenic temperatures, where several pre-stressed stacks of LHC main dipole Nb-Ti cables and some single strands will be irradiated with varying beam intensities. The electrical integrity and the degradation of critical current will be measured after the removal from the HiRadMat facility. In the cold experiment some sample magnets will be added and the degradation of performance will be monitored online. In this contribution the experimental setup of the first experiment, including the sample container and cable stacks, is presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY044
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Paper

Title

Page

Degradation of the Insulation of the LHC Main Dipole Cable when Exposed to High Temperatures

1186

V. Raginel, B. Auchmann, D. Kleiven, R. Schmidt, A.P. Verweij, D. Wollmann
CERN, Geneva, Switzerland

Funding: Research supported by the High Luminosity LHC project
The energy stored in the LHC beams is substantial and requires a complex machine protection system to protect the equipment. Despite efficient beam absorbers, several failure modes lead to some limited beam impact on superconducting magnets. Thus it is required to understand the damage mechanisms and limits of superconducting magnets due to instantaneous beam impact. This becomes even more important due to the future upgrade of CERNs injector chain for the LHC that will lead to an increase of the beam brightness. A roadmap to perform damage tests on magnet parts has been presented previously*. The polyimide insulation of the superconducting cable is identified as one of the critical elements of the magnet. In this contribution, the experimental setup to measure the insulation degradation of LHC main dipole cables due to exposure to high temperature is described. Compressed stacks of insulated Nb-Ti cables have been exposed to a heat treatment within an Argon atmosphere. After each heat treatment, high-voltage measurements verified the dielectric strength of the insulation. The results of this experiment provide an upper damage limit of superconducting magnets due to beam impact.
* Experimental Setups to Determine the Damage Limit of Superconducting Magnets for Instantaneous Beam Losses, V. Raginel et al, IPAC'15

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMB038

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

TUPMW006

Power Deposition in LHC Magnets Due to Bound-Free Pair Production in the Experimental Insertions

1418

C. Bahamonde Castro, B. Auchmann, M.I. Besana, K. Brodzinski, R. Bruce, F. Cerutti, J.M. Jowett, A. Lechner, T. Mertens, V. Parma, S. Redaelli, M. Schaumann, N.V. Shetty, E. Skordis, G.E. Steele, R. van Weelderen
CERN, Geneva, Switzerland

The peak luminosity achieved during Pb-Pb collisions in the LHC in 2015 (3x1027cm^-2s⁻¹) well exceeded the design luminosity and is anticipated to increase by another factor 2 after the next Long Shutdown (2019- 2020). A significant fraction of the power dissipated in ultra-peripheral Pb-Pb collisions is carried by ions from bound-free pair production, which are lost in the dispersion suppressors adjacent to the experimental insertions. At higher luminosities, these ions risk to quench superconducting magnets and might limit their operation due to the dynamic heat load that needs to be evacuated by the cryogenic system. In this paper, we estimate the power deposition in superconducting coils and the magnet cold mass and we quantify the achievable reduction by deviating losses to less sensitive locations or by installing collimators at strategic positions. The second option is considered for the dispersion suppressor next to the ALICE insertion, where a selective displacement of losses to a magnet-free region is not possible.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW006

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

TUPMW023

Macroparticle-Induced Losses During 6.5 TeV LHC Operation

1481

G. Papotti, M. Albert, B. Auchmann, E.B. Holzer, M.K. Kalliokoski, A. Lechner
CERN, Geneva, Switzerland

One of the major performance limitations for operating the LHC at high energy was feared to be the so called UFOs (Unidentified Falling Objects, presumably micrometer sized dust particles which lead to fast beam losses when they interact with the beam). Indeed much higher rates were observed in 2015 compared to Run 1, and about 20 fills were prematurely terminated by too high losses caused by such events. Additionally they triggered a few beam induced quenches at high energy, the first in the history of the LHC. In this paper we review the latest update on the analysis of these events, e.g. the conditioning observed during the year and possible correlations with beam and machine parameters. At the same time we also review the optimization of beam loss monitor thresholds in terms of machine protection and availability.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW023

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TUPMW028

Bound-Free Pair Production in LHC Pb-Pb Operation at 6.37 Z TeV per Beam

1497

J.M. Jowett, B. Auchmann, C. Bahamonde Castro, M.K. Kalliokoski, A. Lechner, T. Mertens, M. Schaumann, C. Xu
CERN, Geneva, Switzerland

In the 2015 Pb-Pb collision run of the LHC, the power of the secondary beams emitted from the interaction point by the bound-free pair production process reached new levels while the propensity of the bending magnets to quench is higher at the new magnetic field levels. This beam power is about 70 times greater than that contained in the luminosity debris and is focussed on a specific location. As long foreseen, orbit bumps were introduced in the dispersion suppressors around the highest luminosity experiments to mitigate the risk by displacing and spreading out these losses. An experiment designed to induce quenches and determine the quench levels and luminosity limit was carried out to assess the need for special collimators to intercept these secondary beams.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW028

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THPOY044

Experimental Setup to Measure the Damage Limits of Superconducting Magnets due to Beam Impact at CERN's HiRadMat Facility

4200

D. Kleiven
Kleiven, David, Geneva, Switzerland
B. Auchmann, V. Raginel, R. Schmidt, A.P. Verweij, D. Wollmann
CERN, Geneva, Switzerland

Funding: Research supported by the High Luminosity LHC project
The future upgrade of CERN's injector chain for the Large Hadron Collider (LHC) will lead to an increase of the beam brightness in the LHC. Beam absorbers are capturing missteered beams, but some limited beam impact on superconducting magnets can hardly be avoided. Therefore, it is planned to measure the damage limits of superconducting magnet components due to beam impact at CERN's HiRad- Mat facility using the 440 GeV proton beam from the Super Proton Synchrotron. Two experiments are proposed. One at ambient and one at cryogenic temperatures, where several pre-stressed stacks of LHC main dipole Nb-Ti cables and some single strands will be irradiated with varying beam intensities. The electrical integrity and the degradation of critical current will be measured after the removal from the HiRadMat facility. In the cold experiment some sample magnets will be added and the degradation of performance will be monitored online. In this contribution the experimental setup of the first experiment, including the sample container and cable stacks, is presented.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY044

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