IPAC2021 - Classification: MC7: Accelerator Technology / T16 Pulsed Power Technology

Paper	Title	Page
WEPAB341	Injection and Extraction Kickers for the Advanced Light Source Upgrade Project (ALS-U)	3487
	W.L. Waldron, D.A. Dawson, S. De Santis, T. Oliver, C. Steier LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The Advanced Light Source upgrade project (ALS-U) at Lawrence Berkeley National Laboratory includes the construction of a new accumulator ring and the replacement of the existing storage ring. Both ferrite-loaded kickers and stripline kickers are used in the ALS-U design for injection, extraction, and decohering the beam before storage ring extraction. In the accumulator ring, the rise and fall time requirements are based on the single bunch revolution time of 608 ns which allows the use of ferrite-loaded kickers. The 10 ns spacing between bunch trains in the storage ring requires stripline kickers to meet the rise and fall time requirements. Both types of kickers are driven by solid-state inductive voltage adders using MOSFETs. Modeling and prototyping efforts have characterized the kicker impedance and beam-induced heating, and explored the effects of beam strike on electrodes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB341
About •	paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 24 August 2021
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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, Geneva, 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 23, 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
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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
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WEPAB347	Design, Construction and Testing of a Magnetic Probe for Fast Kicker Magnets	3510
	N. Ayala, A. Ferrero Colomo, T. Kramer CERN, Geneva, Switzerland
	The CERN PS injection kicker has been modified in the framework of the LHC Injector Upgrade (LIU) project to allow injecting proton beams with an energy of 2 GeV. One of the most important items of the system parameter validation is the measurement and analysis of the magnetic field in the magnet aperture. To meet the required measurement precision without compromising the magnet vacuum performance, a dedicated magnetic probe has been designed, constructed and tested. The results are presented in this paper highlighting the mitigations of electrical, mechanical and vacuum complications. The paper concludes with an analysis of the probe performance during the first magnetic field measurements in the laboratory.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB347
About •	paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 02 September 2021
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WEPAB348	Injection and Extraction Systems of the SIS100 Heavy Ion Synchrotron at FAIR	3514
	I.J. Petzenhauser, U. Blell, S. Heberer GSI, Darmstadt, Germany
	The "Facility for Antiproton and Ion Research" (FAIR) is a new international accelerator complex, which is currently built in Darmstadt, Germany. Part of this complex is the SIS100 heavy ion synchrotron with a circumference of ~1086 m. To inject ions into the SIS100, an injection kicker system will we required. For fast extraction of the particle beam from the SIS100, an extraction kicker is used. This extraction kicker will be a bipolar system, this way it works as an emergency kicker at the same time. The fast kicker systems have to produce a current pulse >6 kA. To achieve this, energy storages are charged up to voltages >70 kV and are quickly discharged. The pulse durations vary from 0.5 us to 7 us, depending on the kicker type and the operation mode. Slow extraction of the ion beam will include an electrostatic septum, operating with voltages up to 160 kV. The requirements of these injection/extraction devices will be described in detail and the status of the projects will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB348
About •	paper received ※ 17 May 2021 paper accepted ※ 11 June 2021 issue date ※ 20 August 2021
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WEPAB349	Design of a Circular Waveguide TM₀₁ Mode Launcher with Wire Loop Feed	3517
	A. Chittora BITS Pilani, Sancoale, India
	In Accelerator technology, RF power couplers are important component to couple RF signal to travelling wave structure. Circular waveguide TM₀₁ mode is one of the symmetric modes, that is suitable to use for RF coupling. TM₀₁ mode launcher is used as an RF coupler in Accelerator technology. Design of a compact circular waveguide TM₀₁ mode-launcher is presented in this paper. The design is based on the principle of magnetic field coupling between a wire loop and TM₀₁ mode of circular waveguide. The mode launcher exhibits high efficiency and 3.1% bandwidth at 3.2 GHz frequency with both circular and elliptical loop. Performance of the mode launcher is experimentally verified and simulated S-parameters agree with the measured results. The mode launcher is of compact size and is suitable for efficient excitation of TM₀₁ mode in circular waveguide and travelling wave structures. The launcher is also useful for cold testing of high power microwave antennas and Radars. M. Forno, "Design of a high power TM₀₁ mode launcher optimized for manufacturing by milling." 2016.
	Poster WEPAB349 [1.135 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB349
About •	paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 20 August 2021
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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
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WEPAB353	Design and Commissioning of a Multipole Injection Kicker for the SOLEIL Storage Ring	3525
	R. Ollier, P. Alexandre, R. Ben El Fekih, L.S. Nadolski SOLEIL, Gif-sur-Yvette, France
	In third-generation synchrotron light sources, achieving an orbit distortion below 10% of the stored beam size is very challenging. The standard injection scheme of SOLEIL is made of 2 septa and 4 kicker magnets installed in a 12 m long straight section. Tuning the 4 kickers, to reduce perturbations, revealed to be almost impossible since it requires having 4 identical magnets, electronics, and Ti coated ceramic chambers. To reach the position stability requirement of the stored beam, a single pulsed magnet with no field on the stored beam path can replace the 4 kickers. Such a device, called MIK (Multipole Injection Kicker), was developed by SOLEIL and successfully commissioned in the MAX-IV 3-GeV ring as the key device used in the standard injection scheme for user operation, reducing the beam orbit distortion below 1 micron in peak value in both planes. A copy of the MIK has been installed in a short straight section of the SOLEIL storage ring, in January 2021. We report MIK positioning studies, the constraints of the project, sapphire chamber coating challenges and the first commissioning results. The R&D MIK is a demonstrator for the injection scheme of SOLEIL upgrade as well.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB353
About •	paper received ※ 21 May 2021 paper accepted ※ 23 July 2021 issue date ※ 31 August 2021
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THPAB157	Studying X-Ray Spectra of the SIS18 Electrostatic Septa to Measure Their Electric Field	4065
	B. Gålander, E. Kozlova, D. Ondreka, A. Sokolov, P.J. Spiller, J. Stadlmann GSI, Darmstadt, Germany
	The synchrotron SIS18 at GSI uses resonant extraction for slow beam extraction on the order of seconds. For some time, there has been an unexplained discrepancy of the slow extraction with a lower extraction efficiency than expected at the highest beam energies. Recent machine studies have indicated that the deflection by the electrostatic septum might be less than the nominal 2.5 mrad, leading to increased losses at the magnetic septum. In this paper, we pursue an idea to directly measure the voltage of the electrode gap by utilizing the fact that dark current electrons accelerated in the gap of the electrostatic extraction septum generate Bremsstrahlung X-rays when hitting the anode. The high-energy cut-off of the X-ray spectra then corresponds to the voltage of the electrode gap. Measurements of the X-ray spectra at the extraction septum of SIS18 have been performed using a solid-state CdTe detector. This technique provides an in-situ measurement of the voltage applied to the electrostatic extraction channel and has proven to be a useful diagnostics tool.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB157
About •	paper received ※ 19 May 2021 paper accepted ※ 02 September 2021 issue date ※ 19 August 2021
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THPAB178	The SIS100 Extraction and Emergency Kicker Magnet System	4115
	J.H. Hottenbacher, K. Dunkel, M. Eisengruber, M. Osemann, A. Padvi, C. Piel RI Research Instruments GmbH, Bergisch Gladbach, Germany S. Heberer, I.J. Petzenhauser GSI, Darmstadt, Germany
	The extraction and emergency kicker system for SIS100 is a bipolar kicker system that allows for an in-situ choice between two directions: extraction to the experiments or to the beam dump. For that, both magnet ends are connected to a PFN each which are being charged simultaneously up to 80kV continuously. Due to the static HV operation, different to usually in other pulsed kicker systems, not only displacement current is flowing in the ferrite material. After less than 1s, the ferrite material is nearly field-free and the E-field is concentrated in the surrounding ceramic magnet clamp mechanism. As the field is further concentrated in gaps between ceramic and metallic parts, the HV layout of the magnet is a critical design task. As a magnetic field homogeneity of ±1% is required, special shaping of the coil is required as found during iterative 3D field simulations. The kicker chamber is designed to operate at a pressure level of 3·10^-11 mBar. As one 3 meter-chamber contains 3.5 m² ferrite surface, careful vacuum heat treatment of the ferrite is required to reach this pressure level. The paper will describe design principles for HV and UHV and effects found by 3D modeling.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB178
About •	paper received ※ 18 May 2021 paper accepted ※ 28 July 2021 issue date ※ 26 August 2021
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THPAB340	Sub-Nanosecond Switching of HV SiC MOS Transistors for Impact Ionisation Triggering	4454
	V. Senaj, T. Kramer, A.A. del Barrio Montañés CERN, Geneva 23, Switzerland M. Sack KIT, Karlsruhe, Germany
	Pulse generators with multi kV/kA pulses are necessary for the particle accelerator environment for beam transfer magnets. Traditionally these generators are using thyratrons - until recently the only switches capable of switching such pulses within tens of ns. There is a strong demand to replace thyratrons with semiconductor switches to avoid their future obsolescence. Very promising candidates are components from the family of fast ionization dynistors triggered by impact ionization. Their sub-nanosecond switching time and extreme current densities can provide performances superior to that of thyratrons. Recent investigations showed that impact ionization triggering is feasible also in cheap industrial thyristors. The main issue is the generation of triggering pulses with slew rates in the multi kV/ns region and with the required output current for charging the parasitic capacitance of the thyristor. We present an approach of generating > 1 kV/ns pulses by ultra-boosted gate driving of HV SiC MOS transistors. We found that the MOS lifetime under these extreme triggering conditions can still reach more than 10⁸ pulses, enough for kicker generator applications.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB340
About •	paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 27 August 2021
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THPAB354	Deployment and Commissioning of the CERN PS Injection Kicker System for Operation with 2 GeV Beams in Short Circuit Mode	4489
	T. Kramer, N. Ayala, J.C.C.M. Borburgh, P.A.H. Burkel, E. Carlier, L. Ducimetière, L.M.C. Feliciano, A. Ferrero Colomo, M.A. Fraser, L.A. Govertsen, R. Noulibos, S. Pavis, L. Sermeus CERN, Geneva, Switzerland
	Within the framework of the LHC Injector Upgrade (LIU) project, the feasibility and design of an upgrade of the existing CERN PS proton injection kicker system have been outlined in previous publications already. This paper describes the adjustments of final design choices, testing, and deployment as well as the validation and commissioning of the new 2 GeV injection kicker system. The upgrade pays particular attention to the reduction of pulse reflections unavoidably induced by a magnet in short circuit mode configuration whilst keeping a fast 10⁴ ns rise and fall time. An adapted thyratron triggering system to reduce jitter and enhance thyratron lifetime is outlined. Additionally, improvements to the magnet entry box and the elimination of SF6 gas in the magnet connection box and the associated pulse transmission lines are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB354
About •	paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 10 August 2021
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Paper

Title

Page

Injection and Extraction Kickers for the Advanced Light Source Upgrade Project (ALS-U)

3487

W.L. Waldron, D.A. Dawson, S. De Santis, T. Oliver, C. Steier
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The Advanced Light Source upgrade project (ALS-U) at Lawrence Berkeley National Laboratory includes the construction of a new accumulator ring and the replacement of the existing storage ring. Both ferrite-loaded kickers and stripline kickers are used in the ALS-U design for injection, extraction, and decohering the beam before storage ring extraction. In the accumulator ring, the rise and fall time requirements are based on the single bunch revolution time of 608 ns which allows the use of ferrite-loaded kickers. The 10 ns spacing between bunch trains in the storage ring requires stripline kickers to meet the rise and fall time requirements. Both types of kickers are driven by solid-state inductive voltage adders using MOSFETs. Modeling and prototyping efforts have characterized the kicker impedance and beam-induced heating, and explored the effects of beam strike on electrodes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB341

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paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 24 August 2021

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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.

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

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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, Geneva, 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

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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.

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

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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 23, 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

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

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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.

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

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

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WEPAB347

Design, Construction and Testing of a Magnetic Probe for Fast Kicker Magnets

3510

N. Ayala, A. Ferrero Colomo, T. Kramer
CERN, Geneva, Switzerland

The CERN PS injection kicker has been modified in the framework of the LHC Injector Upgrade (LIU) project to allow injecting proton beams with an energy of 2 GeV. One of the most important items of the system parameter validation is the measurement and analysis of the magnetic field in the magnet aperture. To meet the required measurement precision without compromising the magnet vacuum performance, a dedicated magnetic probe has been designed, constructed and tested. The results are presented in this paper highlighting the mitigations of electrical, mechanical and vacuum complications. The paper concludes with an analysis of the probe performance during the first magnetic field measurements in the laboratory.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB347

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paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 02 September 2021

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WEPAB348

Injection and Extraction Systems of the SIS100 Heavy Ion Synchrotron at FAIR

3514

I.J. Petzenhauser, U. Blell, S. Heberer
GSI, Darmstadt, Germany

The "Facility for Antiproton and Ion Research" (FAIR) is a new international accelerator complex, which is currently built in Darmstadt, Germany. Part of this complex is the SIS100 heavy ion synchrotron with a circumference of ~1086 m. To inject ions into the SIS100, an injection kicker system will we required. For fast extraction of the particle beam from the SIS100, an extraction kicker is used. This extraction kicker will be a bipolar system, this way it works as an emergency kicker at the same time. The fast kicker systems have to produce a current pulse >6 kA. To achieve this, energy storages are charged up to voltages >70 kV and are quickly discharged. The pulse durations vary from 0.5 us to 7 us, depending on the kicker type and the operation mode. Slow extraction of the ion beam will include an electrostatic septum, operating with voltages up to 160 kV. The requirements of these injection/extraction devices will be described in detail and the status of the projects will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB348

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paper received ※ 17 May 2021 paper accepted ※ 11 June 2021 issue date ※ 20 August 2021

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WEPAB349

Design of a Circular Waveguide TM₀₁ Mode Launcher with Wire Loop Feed

3517

A. Chittora
BITS Pilani, Sancoale, India

In Accelerator technology, RF power couplers are important component to couple RF signal to travelling wave structure. Circular waveguide TM₀₁ mode is one of the symmetric modes, that is suitable to use for RF coupling. TM₀₁ mode launcher is used as an RF coupler in Accelerator technology*. Design of a compact circular waveguide TM₀₁ mode-launcher is presented in this paper. The design is based on the principle of magnetic field coupling between a wire loop and TM₀₁ mode of circular waveguide. The mode launcher exhibits high efficiency and 3.1% bandwidth at 3.2 GHz frequency with both circular and elliptical loop. Performance of the mode launcher is experimentally verified and simulated S-parameters agree with the measured results. The mode launcher is of compact size and is suitable for efficient excitation of TM₀₁ mode in circular waveguide and travelling wave structures. The launcher is also useful for cold testing of high power microwave antennas and Radars.
* M. Forno, "Design of a high power TM₀₁ mode launcher optimized for manufacturing by milling." 2016.

Poster WEPAB349 [1.135 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB349

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 20 August 2021

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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.

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

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

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WEPAB353

Design and Commissioning of a Multipole Injection Kicker for the SOLEIL Storage Ring

3525

R. Ollier, P. Alexandre, R. Ben El Fekih, L.S. Nadolski
SOLEIL, Gif-sur-Yvette, France

In third-generation synchrotron light sources, achieving an orbit distortion below 10% of the stored beam size is very challenging. The standard injection scheme of SOLEIL is made of 2 septa and 4 kicker magnets installed in a 12 m long straight section. Tuning the 4 kickers, to reduce perturbations, revealed to be almost impossible since it requires having 4 identical magnets, electronics, and Ti coated ceramic chambers. To reach the position stability requirement of the stored beam, a single pulsed magnet with no field on the stored beam path can replace the 4 kickers. Such a device, called MIK (Multipole Injection Kicker), was developed by SOLEIL and successfully commissioned in the MAX-IV 3-GeV ring as the key device used in the standard injection scheme for user operation, reducing the beam orbit distortion below 1 micron in peak value in both planes. A copy of the MIK has been installed in a short straight section of the SOLEIL storage ring, in January 2021. We report MIK positioning studies, the constraints of the project, sapphire chamber coating challenges and the first commissioning results. The R&D MIK is a demonstrator for the injection scheme of SOLEIL upgrade as well.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB353

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paper received ※ 21 May 2021 paper accepted ※ 23 July 2021 issue date ※ 31 August 2021

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THPAB157

Studying X-Ray Spectra of the SIS18 Electrostatic Septa to Measure Their Electric Field

4065

B. Gålander, E. Kozlova, D. Ondreka, A. Sokolov, P.J. Spiller, J. Stadlmann
GSI, Darmstadt, Germany

The synchrotron SIS18 at GSI uses resonant extraction for slow beam extraction on the order of seconds. For some time, there has been an unexplained discrepancy of the slow extraction with a lower extraction efficiency than expected at the highest beam energies. Recent machine studies have indicated that the deflection by the electrostatic septum might be less than the nominal 2.5 mrad, leading to increased losses at the magnetic septum. In this paper, we pursue an idea to directly measure the voltage of the electrode gap by utilizing the fact that dark current electrons accelerated in the gap of the electrostatic extraction septum generate Bremsstrahlung X-rays when hitting the anode. The high-energy cut-off of the X-ray spectra then corresponds to the voltage of the electrode gap. Measurements of the X-ray spectra at the extraction septum of SIS18 have been performed using a solid-state CdTe detector. This technique provides an in-situ measurement of the voltage applied to the electrostatic extraction channel and has proven to be a useful diagnostics tool.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB157

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paper received ※ 19 May 2021 paper accepted ※ 02 September 2021 issue date ※ 19 August 2021

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THPAB178

The SIS100 Extraction and Emergency Kicker Magnet System

4115

J.H. Hottenbacher, K. Dunkel, M. Eisengruber, M. Osemann, A. Padvi, C. Piel
RI Research Instruments GmbH, Bergisch Gladbach, Germany
S. Heberer, I.J. Petzenhauser
GSI, Darmstadt, Germany

The extraction and emergency kicker system for SIS100 is a bipolar kicker system that allows for an in-situ choice between two directions: extraction to the experiments or to the beam dump. For that, both magnet ends are connected to a PFN each which are being charged simultaneously up to 80kV continuously. Due to the static HV operation, different to usually in other pulsed kicker systems, not only displacement current is flowing in the ferrite material. After less than 1s, the ferrite material is nearly field-free and the E-field is concentrated in the surrounding ceramic magnet clamp mechanism. As the field is further concentrated in gaps between ceramic and metallic parts, the HV layout of the magnet is a critical design task. As a magnetic field homogeneity of ±1% is required, special shaping of the coil is required as found during iterative 3D field simulations. The kicker chamber is designed to operate at a pressure level of 3·10^-11 mBar. As one 3 meter-chamber contains 3.5 m² ferrite surface, careful vacuum heat treatment of the ferrite is required to reach this pressure level. The paper will describe design principles for HV and UHV and effects found by 3D modeling.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB178

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paper received ※ 18 May 2021 paper accepted ※ 28 July 2021 issue date ※ 26 August 2021

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THPAB340

Sub-Nanosecond Switching of HV SiC MOS Transistors for Impact Ionisation Triggering

4454

V. Senaj, T. Kramer, A.A. del Barrio Montañés
CERN, Geneva 23, Switzerland
M. Sack
KIT, Karlsruhe, Germany

Pulse generators with multi kV/kA pulses are necessary for the particle accelerator environment for beam transfer magnets. Traditionally these generators are using thyratrons - until recently the only switches capable of switching such pulses within tens of ns. There is a strong demand to replace thyratrons with semiconductor switches to avoid their future obsolescence. Very promising candidates are components from the family of fast ionization dynistors triggered by impact ionization. Their sub-nanosecond switching time and extreme current densities can provide performances superior to that of thyratrons. Recent investigations showed that impact ionization triggering is feasible also in cheap industrial thyristors. The main issue is the generation of triggering pulses with slew rates in the multi kV/ns region and with the required output current for charging the parasitic capacitance of the thyristor. We present an approach of generating > 1 kV/ns pulses by ultra-boosted gate driving of HV SiC MOS transistors. We found that the MOS lifetime under these extreme triggering conditions can still reach more than 10⁸ pulses, enough for kicker generator applications.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB340

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paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 27 August 2021

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THPAB354

Deployment and Commissioning of the CERN PS Injection Kicker System for Operation with 2 GeV Beams in Short Circuit Mode

4489

T. Kramer, N. Ayala, J.C.C.M. Borburgh, P.A.H. Burkel, E. Carlier, L. Ducimetière, L.M.C. Feliciano, A. Ferrero Colomo, M.A. Fraser, L.A. Govertsen, R. Noulibos, S. Pavis, L. Sermeus
CERN, Geneva, Switzerland

Within the framework of the LHC Injector Upgrade (LIU) project, the feasibility and design of an upgrade of the existing CERN PS proton injection kicker system have been outlined in previous publications already. This paper describes the adjustments of final design choices, testing, and deployment as well as the validation and commissioning of the new 2 GeV injection kicker system. The upgrade pays particular attention to the reduction of pulse reflections unavoidably induced by a magnet in short circuit mode configuration whilst keeping a fast 10⁴ ns rise and fall time. An adapted thyratron triggering system to reduce jitter and enhance thyratron lifetime is outlined. Additionally, improvements to the magnet entry box and the elimination of SF6 gas in the magnet connection box and the associated pulse transmission lines are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB354

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paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 10 August 2021

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