IPAC2018 - List of Authors (Levens, T.E.)

Paper	Title	Page
MOPMF053	Observations, Analysis and Mitigation of Recurrent LHC Beam Dumps Caused by Fast Losses in Arc Half-Cell 16L2	228
	J.M. Jimenez, D. Amorim, S. A. Antipov, G. Arduini, A. Bertarelli, N. Biancacci, B. Bradu, E. Bravin, G. Bregliozzi, K. Brodzinski, R. Bruce, X. Buffat, L.R. Carver, P. Chiggiato, S.D. Claudet, P. Collier, R. Garcia Alia, M. Giovannozzi, L. K. Grob, E.B. Holzer, W. Höfle, G. Iadarola, G. Kotzian, A. Lechner, T.E. Levens, B. Lindstrom, T. Medvedeva, A. Milanese, D. Mirarchi, E. Métral, D. Perini, S. Redaelli, G. Rumolo, B. Salvant, R. Schmidt, M. Valette, D. Valuch, J. Wenninger, D. Wollmann, C. Yin Vallgren, C. Zamantzas, M. Zerlauth CERN, Geneva, Switzerland D. Amorim Université Grenoble Alpes, Grenoble, France A.A. Gorzawski University of Manchester, Manchester, United Kingdom L. Mether EPFL, Lausanne, Switzerland
	Recurrent beam dumps significantly perturbed the operation of the CERN LHC in the summer months of 2017, especially in August. These unexpected beam dumps were triggered by fast beam losses that built up in the cryogenic beam vacuum at the half-cell 16 left of LHC-IP2 and were detected either at that location but mainly in the collimation insertions. This contribution details the experimental observables (beam losses, coherent instabilities, heat load to cryogenic system, vacuum signals), the extent of the understanding of the beam loss and instability mechanisms and the mitigation steps and new settings that allowed recovering the luminosity performance of the LHC for the rest of the Run.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF053
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MOPMF058	Status of the LHC Schottky Monitors	247
	T. Tydecks, D. Alves, T.E. Levens, M. Wendt, J. Wenninger CERN, Geneva, Switzerland
	The Large Hadron Collider (LHC) features four transverse Schottky monitors detecting Schottky noise from the beam. From the Schottky noise signal, beam properties like tune, chromaticity, and bunch by bunch relative emittances, can be extracted. Being a non-destructive and purely parasitic method of measurement, the Schottky system is of great interest for real-time determination of beam chromaticities especially. Studies, including a dedicated machine development shift as well as parasitic measurements, concerning its capability to accurately measure the beam chromaticities are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF058
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TUPAF024	Impedance and Instability Studies in LEIR with Xenon	720
	N. Biancacci, H. Bartosik, M. Gąsior, S. Hirlaender, V. Kain, T.E. Levens, E. Métral CERN, Geneva, Switzerland M. Migliorati Rome University La Sapienza, Roma, Italy
	In 2017, the LEIR accelerator has been operated with Xe³⁹⁺ beam for fixed target experiments in the SPS North Area. The different ion species, with respect to the usually operated Pb⁵⁴⁺, allowed for additional comparative measurements of tune shift versus intensity at injection energy both in coasting and bunched beams. The fast transverse instability observed for high accumulated intensities has been as well characterized and additional observations relevant to impedance have been collected from longitudinal Schottky signal and BTF measurements. The results of these measurements are summarised and compared to the currently developed machine impedance model.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF024
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TUZGBD4	Impact of a Wideband Feedback Prototype System on TMCI in the SPS	1208
	W. Höfle, H. Bartosik, E.R. Bjørsvik, G. Kotzian, T.E. Levens, K.S.B. Li CERN, Geneva, Switzerland J.E. Dusatko, J.D. Fox, C.H. Rivetta SLAC, Menlo Park, California, USA O. Turgut Stanford University, Stanford, California, USA
	The transverse mode coupling instability (TMCI) in the SPS has been identified as one of the potential performance limitations for future high intensity LHC beams that will be required for the High Luminosity (HL)-LHC era and is being addressed by the LHC Injector Upgrade Project (LIU). A potential mitigation can be provided by wideband feedback systems with a frequency reach of about 1 GHz . For this reason, the development of a prototype system has been started in a CERN collaboration within the US-LARP framework in 2008. In this report we present latest experimental results in 2017 where this prototype system was used in single and multi-bunch studies. In particular, a successful mitigation against TMCI at injection could be demonstrated in single bunch studies.
	Slides TUZGBD4 [15.116 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBD4
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WEPAF084	Commissioning the ELENA Beam Diagnostics Systems at CERN	2043
	G. Tranquille, S. Burger, M. Gąsior, P. Grandemange, T.E. Levens, O. Marqversen, L. Søby CERN, Geneva, Switzerland
	The Extra Low ENergy Antiproton ring (ELENA) at CERN entered the commissioning phase in November 2016 using H⁻ ions and antiprotons to setup the machine at the different energy plateaus. The low intensities and energy of the ELENA beam generate very weak signals making beam diagnostics very challenging. With a circulating beam current of less than 1 μA and an energy where the beam annihilates in less than a few microns of matter, special care was taken during the design phase to ensure an optimal performance of these measurement devices once installed on the ring and transfer lines. A year on we present the performance of the various devices that have been deployed to measure the beam parameters from the extraction point of the Antiproton Decelerator (AD), through the ELENA ring and in the experimental lines.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF084
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THPAF058	Experimental Characterisation of a Fast Instability Linked to Losses in the 16L2 Cryogenic Half-Cell in the CERN LHC	3103
	B. Salvant, S. A. Antipov, G. Arduini, N. Biancacci, X. Buffat, L.R. Carver, P. Collier, A.A. Gorzawski, W. Höfle, G. Iadarola, G. Kotzian, A. Lechner, T.E. Levens, D. Mirarchi, E. Métral, G. Rumolo, D. Valuch CERN, Geneva, Switzerland L. Mether EPFL, Lausanne, Switzerland
	The operation during the summer months of the 2017 Run of the CERN LHC was plagued with fast beam losses that repeatedly occurred in the 16th arc half-cell at the left of IP2 as well as in the collimation insertion, leading to unwanted beam dumps. Transverse coherent oscillations were observed during this fast process. We detail here the experimental observations of coherent motion that al-lowed shedding light upon parts of the mechanism and identify the potential mitigations that were successfully implemented in the second half of the Run.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF058
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Paper

Title

Page

Observations, Analysis and Mitigation of Recurrent LHC Beam Dumps Caused by Fast Losses in Arc Half-Cell 16L2

228

J.M. Jimenez, D. Amorim, S. A. Antipov, G. Arduini, A. Bertarelli, N. Biancacci, B. Bradu, E. Bravin, G. Bregliozzi, K. Brodzinski, R. Bruce, X. Buffat, L.R. Carver, P. Chiggiato, S.D. Claudet, P. Collier, R. Garcia Alia, M. Giovannozzi, L. K. Grob, E.B. Holzer, W. Höfle, G. Iadarola, G. Kotzian, A. Lechner, T.E. Levens, B. Lindstrom, T. Medvedeva, A. Milanese, D. Mirarchi, E. Métral, D. Perini, S. Redaelli, G. Rumolo, B. Salvant, R. Schmidt, M. Valette, D. Valuch, J. Wenninger, D. Wollmann, C. Yin Vallgren, C. Zamantzas, M. Zerlauth
CERN, Geneva, Switzerland
D. Amorim
Université Grenoble Alpes, Grenoble, France
A.A. Gorzawski
University of Manchester, Manchester, United Kingdom
L. Mether
EPFL, Lausanne, Switzerland

Recurrent beam dumps significantly perturbed the operation of the CERN LHC in the summer months of 2017, especially in August. These unexpected beam dumps were triggered by fast beam losses that built up in the cryogenic beam vacuum at the half-cell 16 left of LHC-IP2 and were detected either at that location but mainly in the collimation insertions. This contribution details the experimental observables (beam losses, coherent instabilities, heat load to cryogenic system, vacuum signals), the extent of the understanding of the beam loss and instability mechanisms and the mitigation steps and new settings that allowed recovering the luminosity performance of the LHC for the rest of the Run.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF053

Export •

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

MOPMF058

Status of the LHC Schottky Monitors

247

T. Tydecks, D. Alves, T.E. Levens, M. Wendt, J. Wenninger
CERN, Geneva, Switzerland

The Large Hadron Collider (LHC) features four transverse Schottky monitors detecting Schottky noise from the beam. From the Schottky noise signal, beam properties like tune, chromaticity, and bunch by bunch relative emittances, can be extracted. Being a non-destructive and purely parasitic method of measurement, the Schottky system is of great interest for real-time determination of beam chromaticities especially. Studies, including a dedicated machine development shift as well as parasitic measurements, concerning its capability to accurately measure the beam chromaticities are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF058

Export •

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

TUPAF024

Impedance and Instability Studies in LEIR with Xenon

720

N. Biancacci, H. Bartosik, M. Gąsior, S. Hirlaender, V. Kain, T.E. Levens, E. Métral
CERN, Geneva, Switzerland
M. Migliorati
Rome University La Sapienza, Roma, Italy

In 2017, the LEIR accelerator has been operated with Xe³⁹⁺ beam for fixed target experiments in the SPS North Area. The different ion species, with respect to the usually operated Pb⁵⁴⁺, allowed for additional comparative measurements of tune shift versus intensity at injection energy both in coasting and bunched beams. The fast transverse instability observed for high accumulated intensities has been as well characterized and additional observations relevant to impedance have been collected from longitudinal Schottky signal and BTF measurements. The results of these measurements are summarised and compared to the currently developed machine impedance model.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF024

Export •

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

TUZGBD4

Impact of a Wideband Feedback Prototype System on TMCI in the SPS

1208

W. Höfle, H. Bartosik, E.R. Bjørsvik, G. Kotzian, T.E. Levens, K.S.B. Li
CERN, Geneva, Switzerland
J.E. Dusatko, J.D. Fox, C.H. Rivetta
SLAC, Menlo Park, California, USA
O. Turgut
Stanford University, Stanford, California, USA

The transverse mode coupling instability (TMCI) in the SPS has been identified as one of the potential performance limitations for future high intensity LHC beams that will be required for the High Luminosity (HL)-LHC era and is being addressed by the LHC Injector Upgrade Project (LIU). A potential mitigation can be provided by wideband feedback systems with a frequency reach of about 1 GHz . For this reason, the development of a prototype system has been started in a CERN collaboration within the US-LARP framework in 2008. In this report we present latest experimental results in 2017 where this prototype system was used in single and multi-bunch studies. In particular, a successful mitigation against TMCI at injection could be demonstrated in single bunch studies.

Slides TUZGBD4 [15.116 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBD4

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WEPAF084

Commissioning the ELENA Beam Diagnostics Systems at CERN

2043

G. Tranquille, S. Burger, M. Gąsior, P. Grandemange, T.E. Levens, O. Marqversen, L. Søby
CERN, Geneva, Switzerland

The Extra Low ENergy Antiproton ring (ELENA) at CERN entered the commissioning phase in November 2016 using H⁻ ions and antiprotons to setup the machine at the different energy plateaus. The low intensities and energy of the ELENA beam generate very weak signals making beam diagnostics very challenging. With a circulating beam current of less than 1 μA and an energy where the beam annihilates in less than a few microns of matter, special care was taken during the design phase to ensure an optimal performance of these measurement devices once installed on the ring and transfer lines. A year on we present the performance of the various devices that have been deployed to measure the beam parameters from the extraction point of the Antiproton Decelerator (AD), through the ELENA ring and in the experimental lines.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF084

Export •

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

THPAF058

Experimental Characterisation of a Fast Instability Linked to Losses in the 16L2 Cryogenic Half-Cell in the CERN LHC

3103

B. Salvant, S. A. Antipov, G. Arduini, N. Biancacci, X. Buffat, L.R. Carver, P. Collier, A.A. Gorzawski, W. Höfle, G. Iadarola, G. Kotzian, A. Lechner, T.E. Levens, D. Mirarchi, E. Métral, G. Rumolo, D. Valuch
CERN, Geneva, Switzerland
L. Mether
EPFL, Lausanne, Switzerland

The operation during the summer months of the 2017 Run of the CERN LHC was plagued with fast beam losses that repeatedly occurred in the 16th arc half-cell at the left of IP2 as well as in the collimation insertion, leading to unwanted beam dumps. Transverse coherent oscillations were observed during this fast process. We detail here the experimental observations of coherent motion that al-lowed shedding light upon parts of the mechanism and identify the potential mitigations that were successfully implemented in the second half of the Run.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF058

Export •

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