IPAC2021 - List of Authors (Barnes, M.J.)

Paper	Title	Page
WEPAB342	Beam Induced Power Deposition in CERN SPS Injection Kickers	3490
	M.J. Barnes, O. Bjorkqvist CERN, Geneva 23, Switzerland K. Kodama KEK, Ibaraki, Japan
	The SPS injection kicker magnets (MKP) were developed in the 1970’s, before beam power deposition was considered an issue and before any advanced tools for analysing beam coupling impedance were available in their current form. These magnets are very lossy from a beam impedance perspective, and the beam induced power deposition is highly non-uniform. This is expected to be an issue during SPS operation with the higher intensity beams needed in the future for HL-LHC. There is an existing design, with serigraphy, that will mitigate the heating issues, which is presently being implemented on a prototype for test and measurement. Models have been developed to aid in predicting the safe operating regions until the upgraded MKPs are installed in the SPS: these are reported herein. A novel measurement technique is also presented to confirm the non-uniform power deposition in the ferrite yoke. Beam coupling impedance, power deposition, field rise time and field uniformity data are also presented for an upgraded, prototype, MKP.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB342
About •	paper received ※ 16 May 2021 paper accepted ※ 02 July 2021 issue date ※ 25 August 2021
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WEPAB343	Inductive Adder Prototype for FCC-hh Injection Kicker System	3494
	D. Woog, M.J. Barnes, T. Kramer CERN, Meyrin, Switzerland H. De Gersem TEMF, TU Darmstadt, Darmstadt, Germany
	The future circular collider (FCC) requires a highly reliable injection kicker system. Present day kicker systems often rely on thyratron-based pulse generators and a pulse forming network or line: the thyratron is susceptible to self-triggering. Hence, an alternative pulse generator topology, based on fast semiconductor switches, is considered for the FCC. One possibility is an inductive adder (IA). A prototype IA has been designed and built: the main challenges are the fast rise time, high output current, low system impedance and a 2.3 us pulse duration combined with low droop. This paper presents the results of measurements on the prototype IA where the rated output current and output voltage were achieved separately. Suggested improvements to the IA hardware are identified and proposals are presented that could help improve the kicker system performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB343
About •	paper received ※ 16 May 2021 paper accepted ※ 01 July 2021 issue date ※ 17 August 2021
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WEPAB344	Studies for Mitigating Flashover of CERN-LHC Dilution Kicker Magnets	3498
	A.M. Loebner, M.J. Barnes, W. Bartmann, C. Bracco, L. Ducimetière, V. Namora, V. Senaj CERN, Geneva 23, Switzerland
	The LHC beam dump system is used for extracting beam from the LHC and, as such, is a safety critical system whose proper functionality must be assured. Dilution kicker magnets (MKBs) sweep the extracted beam over the cross-sectional area of a dump block as the energy density would otherwise be too high and damage the block. In 2018, a high voltage flashover occurred in a vertical MKB (MKBV) vacuum tank, during a beam dump, which resulted in non-ideal sweep of the beam over the block. The location of the flashover could not be identified during a subsequent inspection of the magnet. Hence, electrical field simulations have been carried out to identify potentially critical regions, to determine the most probable region of the flashover. One potentially critical region is a rectangular beam pipe (RBP) between the end of the tank and the MKBV magnet, whose purpose is to reduce plasma propagation to the adjacent tank in the event of a flashover. Mitigating measures were studied and are reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB344
About •	paper received ※ 16 May 2021 paper accepted ※ 06 July 2021 issue date ※ 22 August 2021
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WEPAB345	Impedance and Thermal Studies of the LHC Injection Kicker Magnet Upgrade	3502
	M.J. Barnes, O. Bjorkqvist, F. Motschmann CERN, Geneva, Switzerland
	The bunch intensities of High Luminosity (HL) LHC are predicted to lead to heating of the ferrite yokes of the LHC injection kicker magnets (MKI), in their current configuration, to their Curie temperature. Hence, the MKIs are being upgraded to meet the requirements of HL-LHC, which is planned to start in the mid-2020s. The upgraded design features an RF damping ferrite loaded structure at the upstream end of each magnet, which will absorb a large portion of the beam induced power deposition of the magnet. The ferrite damper is cooled via a copper sleeve, brazed to the ferrite, and a set of water pipes. The thermal contact conductance (TCC) between ferrite and copper is very important, as are the properties of the ferrite. In this paper, we present measurements of the TCC and ferrite properties. This data is used to predict temperatures during operation of the LHC. In addition, a measurement and prediction is shown for the longitudinal impedance of the magnet. The models developed in this study will be benchmarked during run III of the LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB345
About •	paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 13 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB346	Electromagnetic Modelling of Kicker Magnets to Derive Equivalent Circuits	3506
	M.J. Barnes, O. Bjorkqvist CERN, Geneva 23, Switzerland L. Jensen, O.A. Nielsen Aarhus University, Aarhus, Denmark
	An equivalent circuit model of a kicker magnet system is an invaluable tool for predicting the performance, studying possible modifications and for helping to diagnose faults. The frequency content of pulses associated with a ferrite loaded transmission line kicker magnet generally extend up to a few tens of MHz: hence, it is feasible to accurately model such a kicker magnet using lumped elements. This modelling technique is powerful since it in general has a run time several orders of magnitude shorter than a full wave electromagnetic simulation. In this paper, we determine values, including those of parasitic components, using modern simulation tools, for use in the lumped equivalent circuit models. In addition, the paper describes a method to simulate coupling between beam and the electrical circuit of a kicker magnet at relatively low frequencies: this allows one to use circuit analysis tools to study means of mitigating beam induced resonances.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB346
About •	paper received ※ 16 May 2021 paper accepted ※ 02 July 2021 issue date ※ 14 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB351	Requirements for an Inductive Voltage Adder as Driver for a Kicker Magnet with Short Circuit Termination	3521
	J. Ruf, M.J. Barnes, T. Kramer CERN, Geneva 23, Switzerland M. Sack KIT, Karlsruhe, Germany
	At CERN pulse generators based on Thyratron switches and SF6 gas filled pulse forming lines, used for driving kicker magnets, are to be replaced with semiconductor technology. Preliminary investigations show the inductive voltage adder is suitable as a pulse generator for this application. To increase the magnetic field without raising the system voltage, a short-circuit termination is often applied to a kicker magnet. Because of the electrical length of a transmission line magnet, wave propagation needs to be considered. To allow for the wavefront reflected from the short-circuit termination back to the generator, a novel approach for an inductive adder architecture has been investigated. It is based on a modified generator interface, circulating the current back into the load, until the stored energy is absorbed at the end of the pulse. This approach allows for a smaller magnetic core size compared to a conventional design with a matched load. Moreover, it enables more energy-efficient operation involving smaller storage capacitors. This paper summarizes the conceptual design features and furthermore gives an overview of the parameter space for possible applications at CERN.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB351
About •	paper received ※ 18 May 2021 paper accepted ※ 11 June 2021 issue date ※ 17 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Beam Induced Power Deposition in CERN SPS Injection Kickers

3490

M.J. Barnes, O. Bjorkqvist
CERN, Geneva 23, Switzerland
K. Kodama
KEK, Ibaraki, Japan

The SPS injection kicker magnets (MKP) were developed in the 1970’s, before beam power deposition was considered an issue and before any advanced tools for analysing beam coupling impedance were available in their current form. These magnets are very lossy from a beam impedance perspective, and the beam induced power deposition is highly non-uniform. This is expected to be an issue during SPS operation with the higher intensity beams needed in the future for HL-LHC. There is an existing design, with serigraphy, that will mitigate the heating issues, which is presently being implemented on a prototype for test and measurement. Models have been developed to aid in predicting the safe operating regions until the upgraded MKPs are installed in the SPS: these are reported herein. A novel measurement technique is also presented to confirm the non-uniform power deposition in the ferrite yoke. Beam coupling impedance, power deposition, field rise time and field uniformity data are also presented for an upgraded, prototype, MKP.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB342

About •

paper received ※ 16 May 2021 paper accepted ※ 02 July 2021 issue date ※ 25 August 2021

Export •

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

WEPAB343

Inductive Adder Prototype for FCC-hh Injection Kicker System

3494

D. Woog, M.J. Barnes, T. Kramer
CERN, Meyrin, Switzerland
H. De Gersem
TEMF, TU Darmstadt, Darmstadt, Germany

The future circular collider (FCC) requires a highly reliable injection kicker system. Present day kicker systems often rely on thyratron-based pulse generators and a pulse forming network or line: the thyratron is susceptible to self-triggering. Hence, an alternative pulse generator topology, based on fast semiconductor switches, is considered for the FCC. One possibility is an inductive adder (IA). A prototype IA has been designed and built: the main challenges are the fast rise time, high output current, low system impedance and a 2.3 us pulse duration combined with low droop. This paper presents the results of measurements on the prototype IA where the rated output current and output voltage were achieved separately. Suggested improvements to the IA hardware are identified and proposals are presented that could help improve the kicker system performance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB343

About •

paper received ※ 16 May 2021 paper accepted ※ 01 July 2021 issue date ※ 17 August 2021

Export •

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

WEPAB344

Studies for Mitigating Flashover of CERN-LHC Dilution Kicker Magnets

3498

A.M. Loebner, M.J. Barnes, W. Bartmann, C. Bracco, L. Ducimetière, V. Namora, V. Senaj
CERN, Geneva 23, Switzerland

The LHC beam dump system is used for extracting beam from the LHC and, as such, is a safety critical system whose proper functionality must be assured. Dilution kicker magnets (MKBs) sweep the extracted beam over the cross-sectional area of a dump block as the energy density would otherwise be too high and damage the block. In 2018, a high voltage flashover occurred in a vertical MKB (MKBV) vacuum tank, during a beam dump, which resulted in non-ideal sweep of the beam over the block. The location of the flashover could not be identified during a subsequent inspection of the magnet. Hence, electrical field simulations have been carried out to identify potentially critical regions, to determine the most probable region of the flashover. One potentially critical region is a rectangular beam pipe (RBP) between the end of the tank and the MKBV magnet, whose purpose is to reduce plasma propagation to the adjacent tank in the event of a flashover. Mitigating measures were studied and are reported in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB344

About •

paper received ※ 16 May 2021 paper accepted ※ 06 July 2021 issue date ※ 22 August 2021

Export •

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

WEPAB345

Impedance and Thermal Studies of the LHC Injection Kicker Magnet Upgrade

3502

M.J. Barnes, O. Bjorkqvist, F. Motschmann
CERN, Geneva, Switzerland

The bunch intensities of High Luminosity (HL) LHC are predicted to lead to heating of the ferrite yokes of the LHC injection kicker magnets (MKI), in their current configuration, to their Curie temperature. Hence, the MKIs are being upgraded to meet the requirements of HL-LHC, which is planned to start in the mid-2020s. The upgraded design features an RF damping ferrite loaded structure at the upstream end of each magnet, which will absorb a large portion of the beam induced power deposition of the magnet. The ferrite damper is cooled via a copper sleeve, brazed to the ferrite, and a set of water pipes. The thermal contact conductance (TCC) between ferrite and copper is very important, as are the properties of the ferrite. In this paper, we present measurements of the TCC and ferrite properties. This data is used to predict temperatures during operation of the LHC. In addition, a measurement and prediction is shown for the longitudinal impedance of the magnet. The models developed in this study will be benchmarked during run III of the LHC.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB345

About •

paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 13 August 2021

Export •

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

WEPAB346

Electromagnetic Modelling of Kicker Magnets to Derive Equivalent Circuits

3506

M.J. Barnes, O. Bjorkqvist
CERN, Geneva 23, Switzerland
L. Jensen, O.A. Nielsen
Aarhus University, Aarhus, Denmark

An equivalent circuit model of a kicker magnet system is an invaluable tool for predicting the performance, studying possible modifications and for helping to diagnose faults. The frequency content of pulses associated with a ferrite loaded transmission line kicker magnet generally extend up to a few tens of MHz: hence, it is feasible to accurately model such a kicker magnet using lumped elements. This modelling technique is powerful since it in general has a run time several orders of magnitude shorter than a full wave electromagnetic simulation. In this paper, we determine values, including those of parasitic components, using modern simulation tools, for use in the lumped equivalent circuit models. In addition, the paper describes a method to simulate coupling between beam and the electrical circuit of a kicker magnet at relatively low frequencies: this allows one to use circuit analysis tools to study means of mitigating beam induced resonances.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB346

About •

paper received ※ 16 May 2021 paper accepted ※ 02 July 2021 issue date ※ 14 August 2021

Export •

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

WEPAB351

Requirements for an Inductive Voltage Adder as Driver for a Kicker Magnet with Short Circuit Termination

3521

J. Ruf, M.J. Barnes, T. Kramer
CERN, Geneva 23, Switzerland
M. Sack
KIT, Karlsruhe, Germany

At CERN pulse generators based on Thyratron switches and SF6 gas filled pulse forming lines, used for driving kicker magnets, are to be replaced with semiconductor technology. Preliminary investigations show the inductive voltage adder is suitable as a pulse generator for this application. To increase the magnetic field without raising the system voltage, a short-circuit termination is often applied to a kicker magnet. Because of the electrical length of a transmission line magnet, wave propagation needs to be considered. To allow for the wavefront reflected from the short-circuit termination back to the generator, a novel approach for an inductive adder architecture has been investigated. It is based on a modified generator interface, circulating the current back into the load, until the stored energy is absorbed at the end of the pulse. This approach allows for a smaller magnetic core size compared to a conventional design with a matched load. Moreover, it enables more energy-efficient operation involving smaller storage capacitors. This paper summarizes the conceptual design features and furthermore gives an overview of the parameter space for possible applications at CERN.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB351

About •

paper received ※ 18 May 2021 paper accepted ※ 11 June 2021 issue date ※ 17 August 2021

Export •

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