IPAC2017 - List of Authors (Vlachodimitropoulos, V.)

Paper	Title	Page
TUPVA007	Impact of LHC and SPS Injection Kicker Rise Times on Lhc Filling Schemes and Luminosity Reach	2043
	W. Bartmann, M.J. Barnes, J. Boyd, E. Carlier, A. Chmielinska, B. Goddard, G. Kotzian, C. Schwick, L.S. Stoel, D. Valuch, F.M. Velotti, V. Vlachodimitropoulos, C. Wiesner CERN, Geneva, Switzerland
	The 2016 LHC proton filling schemes generally used a spacing between injections of batches of bunches into SPS and LHC corresponding to the design report specification for the SPS and LHC injection kicker rise times, respectively. A reduction of the batch spacing can be directly used to increase luminosity without detrimental effects on beam stability, and with no increase in the number of events per crossing seen by the experiments. Measurements and simulations were performed in SPS and LHC to understand if a shorter injection kicker rise time and associated tighter batch spacing would lead to increased injection oscillations of the first and last bunches of a bunch train and eventually also a systematic growth of the transverse emittance. The results were used to define the minimum possible batch spacing for an acceptable emittance growth in LHC, with gains of reductions of about 10% possible in both machines. The results are discussed, including the potential improvement of the LHC luminosity for different filling schemes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA007
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WEPVA094	Study of an Improved Beam Screen Design for the LHC Injection Kicker Magnet for HL-LHC	3471
	V. Vlachodimitropoulos, M.J. Barnes, L. Ducimetière, L. Vega Cid, W.J.M. Weterings CERN, Geneva, Switzerland
	During Run 1 of the LHC, one of the injection kicker magnets (MKIs) occasionally exhibited an excessively high ferrite temperature, caused by coupling of the high intensity beam to the real impedance of the magnet. Beam-screen upgrades have been very effective in reducing beam coupling impedance during Run 2. However, temperature measurements during LHC operation have shown that one end of the MKIs ferrite yoke is consistently hotter than the other: this effect is due to highly non-uniform beam induced power deposition along the kicker. Electromagnetic and thermal simulations show that part of the ferrite yoke will be above its Curie temperature when the LHC is operated with HL-LHC beam parameters, which could increase the turn-around time between fills of the LHC. An impedance mitigation study is presented in this paper with emphasis on the effect of the beam screen layout upon both total beam induced power deposition and its longitudinal distribution. Results of complex thermal simulations, to benchmark the effectiveness of the proposed schemes, are reported. To validate the proposed modification a test bench measurement was performed and preliminary results are discussed
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA094
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WEPVA096	Thermal Analysis of the LHC Injection Kicker Magnets	3479
	L. Vega Cid, M.J. Barnes, V. Vlachodimitropoulos, W.J.M. Weterings CERN, Geneva, Switzerland A. Abánades ETSII UPM, Madrid, Spain
	Funding: Research supported by the HL-LHC project. The CERN Large Hadron Collider LHC is equipped with two fast pulsed magnet systems (MKIs) that inject particle beams coming from the injector chain. Operation with high intensity beams for many hours can lead to significant beam induced heating of the ferrite yokes of the MKIs. When the ferrite exceeds the Curie temperature of 125°C it loses its magnetic properties, preventing further injection until the ferrite cools down, potentially causing a delay of several hours. Hence important upgrades of the beam-screen were implemented after Run 1 of LHC. However, the High-Luminosity (HL) LHC will be operated with significantly higher intensity beams and hence additional measures are required to limit the ferrite temperature. These magnets operate under ultra-high vacuum conditions: convection is negligible and, as a result of low emissivity of the inside of the vacuum tanks, thermal radiation is limited. A detailed study of the thermal behaviour of these magnets is reported and compared with measurements. In addition several options to improve cooling of the ferrites are presented and analysed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA096
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Impact of LHC and SPS Injection Kicker Rise Times on Lhc Filling Schemes and Luminosity Reach

2043

W. Bartmann, M.J. Barnes, J. Boyd, E. Carlier, A. Chmielinska, B. Goddard, G. Kotzian, C. Schwick, L.S. Stoel, D. Valuch, F.M. Velotti, V. Vlachodimitropoulos, C. Wiesner
CERN, Geneva, Switzerland

The 2016 LHC proton filling schemes generally used a spacing between injections of batches of bunches into SPS and LHC corresponding to the design report specification for the SPS and LHC injection kicker rise times, respectively. A reduction of the batch spacing can be directly used to increase luminosity without detrimental effects on beam stability, and with no increase in the number of events per crossing seen by the experiments. Measurements and simulations were performed in SPS and LHC to understand if a shorter injection kicker rise time and associated tighter batch spacing would lead to increased injection oscillations of the first and last bunches of a bunch train and eventually also a systematic growth of the transverse emittance. The results were used to define the minimum possible batch spacing for an acceptable emittance growth in LHC, with gains of reductions of about 10% possible in both machines. The results are discussed, including the potential improvement of the LHC luminosity for different filling schemes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA007

Export •

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

WEPVA094

Study of an Improved Beam Screen Design for the LHC Injection Kicker Magnet for HL-LHC

3471

V. Vlachodimitropoulos, M.J. Barnes, L. Ducimetière, L. Vega Cid, W.J.M. Weterings
CERN, Geneva, Switzerland

During Run 1 of the LHC, one of the injection kicker magnets (MKIs) occasionally exhibited an excessively high ferrite temperature, caused by coupling of the high intensity beam to the real impedance of the magnet. Beam-screen upgrades have been very effective in reducing beam coupling impedance during Run 2. However, temperature measurements during LHC operation have shown that one end of the MKIs ferrite yoke is consistently hotter than the other: this effect is due to highly non-uniform beam induced power deposition along the kicker. Electromagnetic and thermal simulations show that part of the ferrite yoke will be above its Curie temperature when the LHC is operated with HL-LHC beam parameters, which could increase the turn-around time between fills of the LHC. An impedance mitigation study is presented in this paper with emphasis on the effect of the beam screen layout upon both total beam induced power deposition and its longitudinal distribution. Results of complex thermal simulations, to benchmark the effectiveness of the proposed schemes, are reported. To validate the proposed modification a test bench measurement was performed and preliminary results are discussed

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA094

Export •

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

WEPVA096

Thermal Analysis of the LHC Injection Kicker Magnets

3479

L. Vega Cid, M.J. Barnes, V. Vlachodimitropoulos, W.J.M. Weterings
CERN, Geneva, Switzerland
A. Abánades
ETSII UPM, Madrid, Spain

Funding: Research supported by the HL-LHC project.
The CERN Large Hadron Collider LHC is equipped with two fast pulsed magnet systems (MKIs) that inject particle beams coming from the injector chain. Operation with high intensity beams for many hours can lead to significant beam induced heating of the ferrite yokes of the MKIs. When the ferrite exceeds the Curie temperature of 125°C it loses its magnetic properties, preventing further injection until the ferrite cools down, potentially causing a delay of several hours. Hence important upgrades of the beam-screen were implemented after Run 1 of LHC. However, the High-Luminosity (HL) LHC will be operated with significantly higher intensity beams and hence additional measures are required to limit the ferrite temperature. These magnets operate under ultra-high vacuum conditions: convection is negligible and, as a result of low emissivity of the inside of the vacuum tanks, thermal radiation is limited. A detailed study of the thermal behaviour of these magnets is reported and compared with measurements. In addition several options to improve cooling of the ferrites are presented and analysed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA096

Export •

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