IPAC2022 - Classification: MC7: Accelerator Technology / T06: Room Temperature RF

Paper	Title	Page
TUPOST013	Concept and Development of 65 kW Solid-State RF Amplifiers for Sirius	868
	M. Hoffmann Wallner, A.P.B. Lima LNLS, Campinas, Brazil R.H.A. Farias CNPEM, Campinas, SP, Brazil
	Sirius is a 4th generation synchrotron light source currently operating with 100 mA stored beam and one room temperature RF cavity driven by two 65 kW solid-state amplifiers (SSAs). After installation of the cryogenic plant, two superconducting (SC) RF cavities are planned to replace the room temperature cavity. Each SC cavity is going to be driven by a 250 kW RF signal at 500 MHz, resulting from the combination of four 65 kW RF SSAs. Due to the recent development of 900 W solid-state power amplifier modules, a new topology is proposed for the four amplifiers that still need to be constructed. For the amplifier’s combining stage, a cavity combiner with 80 input ports was simulated. For the dividing stage, 8-way and 10-way power splitters were designed. The general scheme of the amplifier is presented, as well as simulation and measurement results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST013
About •	Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 03 July 2022
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TUPOTK003	High Power RF Conditioning of the ESS RFQ	1189
	O. Piquet, A.C. Chauveau, P. Hamel CEA-IRFU, Gif-sur-Yvette, France M. Baudrier, M.J. Desmons CEA-DRF-IRFU, France B. Jones, D. Noll, A.G. Sosa, E. Trachanas, R. Zeng ESS, Lund, Sweden
	The 352.21 MHz Radio Frequency Quadrupole (RFQ) for the European Spallation Source ERIC (ESS) has been delivered by the end of 2019 by CEA/IRFU. The RFQ is designed to accelerate a 70 mA proton beam from 75 keV up to 3.62 MeV. It consists of a 4-vane resonant cavity with a total length of 4.6 m. Two coaxial power loop couplers feed the RFQ with the 1.4 MW of RF power required for beam operation. This paper first presents the main systems required for the RFQ conditioning. Then it summarizes the main steps and results of this high power RF conditioning completed at ESS from June 9 to July 29, 2021 in order to achieve the nominal field for a pulse length of 3.2ms at the repetition rate of 14Hz.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK003
About •	Received ※ 08 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 09 July 2022
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TUPOTK030	X-Rays Energy Measurements During the RFQ Conditioning at the European Spallation Source	1275
	E. Laface, C.G. Maiano, R. Zeng ESS, Lund, Sweden O. Piquet CEA-DRF-IRFU, France
	The Radio Frequency Quadrupole (RFQ) was conditioned at the European Spallation Source during spring 2021. We used part of the conditioning time to estimate the accelerating potential within the RFQ analyzing the x-rays bremsstrahlung radiation emitted by the electrons released and accelerated in the RFQ. The results of these measurements are in good agreement with the theoretical prediction.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK030
About •	Received ※ 16 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 27 June 2022
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TUPOMS028	3HC - Third Harmonic Normal Conducting Active Cavity Collaboration Between HZB, DESY and ALBA	1471
	F. Pérez, J.R. Ocampo, A. Salom, P. Solans ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain W. Anders, V. Dürr, T. Loewner, A.N. Matveenko, M. Ries, L. Shi, Y. Tamashevich, A.V. Tsakanian HZB, Berlin, Germany M. Ebert, R. Onken DESY, Hamburg, Germany P. Hülsmann GSI, Darmstadt, Germany W.F.O. Müller TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Co-funded by the European Regional Development Fund (ERDF) A collaboration agreement between the HZB, DESY and ALBA institutions was signed on 2021 in order to test the 3rd harmonic normal conducting, HOM damped, active cavity designed and prototyped by ALBA. The test will involve low power characterization of the fundamental mode, bead pull measurements to fully determine the HOM characteristics, a full high power conditioning to validate the power capability of the cavity, and finally, the installation of the cavity in the BESSY II storage ring in order to test the cavity in real conditions with beam. In this paper the low power, bead pull and conditioning results will be presented. The cavity has been installed at BESSY II on May 2022 to be tested after the summer shutdown. Prototype fabrication of an active normal conducting third harmonic cavity for the ALBA Storage Ring. J.Ocampo et al. , IPAC 2022 proceedings.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS028
About •	Received ※ 06 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 02 July 2022
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TUPOMS038	RFQ NEWGAIN: RF and Thermomechanical Design	1510
	P. Hamel, N. Sellami CEA-IRFU, Gif-sur-Yvette, France M.J. Desmons, O. Piquet, B. Prevet CEA-DRF-IRFU, France
	Funding: Agence Nationale de la Recherche (ANR) A new injector called NEWGAIN will be added to the SPIRAL2 Linear Accelerator (LINAC), in parallel with the existing one. It will be mainly composed of an ion source and a Radio Frequency Quadrupole (RFQ) connected to the superconductive LINAC of SPIRAL2. The new RFQ will accelerate at 88.05 MHz particles with charge-over-mass ratio (Q/A) between 1/3 and 1/7, from 10 keV/u up to 590 keV/u. It consists of a 4-vane resonant cavity with a total length of 7 m. It is a CW machine that has to show stable operation, provide the request availability, have the minimum losses in order to provide the highest current to the superconductive LINAC and show the best quality/cost ratio. This paper will present the preliminary RF design and the thermomechanical study for this RFQ.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS038
About •	Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 27 June 2022
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TUPOMS040	Characterization of Higher-Order-Modes (HOM) in THOMX Storage Ring RF Cavity	1513
	M. El Khaldi, J-N. Cayla, H. Monard Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France M. Diop, F. Ribeiro SOLEIL, Gif-sur-Yvette, France
	The RF system of the ThomX storage ring consists in a 500 MHz single cell copper cavity of the ELETTRA type, powered with a 50 kW CW solid state amplifier, and the associated Low-Level RF feedback and control loops. The low operating energy of 50-100 MeV makes the impedances of the cavity higher order modes (HOMs) particularly critical for the beam stability. Their parasitic effects on the beam can be cured by HOM frequency shifting techniques, based on a fine temperature tuning and a dedicated adjustable plunger. A cavity temperature stability of ± 0.1 °C within a range from 30 up to 70 °C is achieved by a precise control of its water-cooling temperature. On the other hand, the tuning of the cavity fundamental mode is achieved by changing its axial length by means of a mechanical tuner. In order to insure a fine control of the HOM frequencies, a good knowledge of their characteristics is mandatory. The main parameters of the fundamental and of the HOMs up to 2.2 GHz versus temperature have been measured at low power using a vector network analyzer (VNA).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS040
About •	Received ※ 03 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 21 June 2022
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TUPOMS041	High Power RF-Cavity Development for the HBS-Driver LINAC	1516
	M. Basten, K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, M. Vossberg, S. Yaramyshev GSI, Darmstadt, Germany K. Aulenbacher, W.A. Barth, M. Basten, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu HIM, Mainz, Germany K. Aulenbacher, W.A. Barth, F.D. Dziuba, S. Lauber, J. List KPH, Mainz, Germany T. Gutberlet JCNS, Jülich, Germany H. Podlech IAP, Frankfurt am Main, Germany H. Podlech HFHF, Frankfurt am Main, Germany
	Neutron research in Europe is mainly based on various nuclear reactors that will be successively decommissioned over the next years. This means that despite the commissioning of the European Spallation Source ESS, many neutron research centres, especially in the medium flux regime, will disappear. In response to this situation, the Jülich Centre for Neutron Science (JCNS) has begun the development of a scalable, compact, accelerator-based High Brilliance neutron Source (HBS). A total of three different neutron target stations are planned, which can be operated with a 100 mA proton beam of up to 70 MeV and a duty cycle of up to 6%. The driver Linac consists of an Electron Cyclotron Resonance (ECR) ion source followed by a LEBT section, a 2.5 MeV double Radio-Frequency Quadrupole (RFQ) and 35 normal conducting (NC) Crossbar H-Mode (CH) cavities. The development of the cavities is carried out by the Institute for Applied Physics (IAP) at the Goethe University Frankfurt am Main. Due to the high beam current, all cavities as well as the associated tuners and couplers have to be optimised for operation under high thermal load to ensure safe operation. In collaboration with the GSI Centre for Heavy Ion Research as the ideal test facility for high power tests, two cavities and the associated hardware are being designed and will be tested. The design and latest status of both cavities will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS041
About •	Received ※ 18 May 2022 — Revised ※ 15 June 2022 — Accepted ※ 28 June 2022 — Issue date ※ 06 July 2022
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TUPOMS042	Cavity R&D for HBS Accelerator	1520
	N.F. Petry, K. Kümpel, S. Lamprecht, O. Meusel, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany
	The demand for neutrons of various types for research is growing day by day worldwide. To meet the growing demand the Jülich High Brilliance Neutron Source (HBS) is in development. It is based on a high power linear proton accelerator with an end energy of 70 MeV and a proton beam current of 100 mA. After the injector and the MEBT is the main part of the accelerator, which consists of about 36 CH-type cavities. The design of the CH-type cavities will be optimized in terms of required power, required cooling and reliability and the recent results will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS042
About •	Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 15 June 2022
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TUPOMS043	High Power Tests of a New 4-Rod RFQ with Focus on its Mechanical Vibrations	1523
	S.R. Wagner, D. Koser, K. Kümpel, H. Podlech IAP, Frankfurt am Main, Germany K.B. Bahrke-Rein TU Darmstadt, Darmstadt, Germany M. Basten GSI, Darmstadt, Germany M. Basten HIM, Mainz, Germany H. Podlech HFHF, Frankfurt am Main, Germany
	Because of strong mechanical vibrations of the electrodes and its sensitivity to changes of thermal load, the operational stability of the existing 4-rod RFQ at the High Charge State Injector (HLI) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, could not be ensured for all planned operating states. To resolve this issue and ensure stable injection into the HLI, a new RFQ-prototype, optimized in terms of vibration suppression and cooling efficiency, was designed at the Institute of Applied Physics (IAP) of Goethe University Frankfurt. To test the performance of this prototype and demonstrate the operational stability in terms of mechanical vibration as well as thermal load, high power tests with more than 25’kW/m were performed at GSI. After initial conditioning, detailed vibrational measurements during high power RF operation using a laser Doppler vibrometer were performed, which were then compared to previously conducted simulations using ANSYS. Ultimately, the ability for stable operation up to high power levels with an efficient vibration suppression and moderate heating have clearly been demonstrated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS043
About •	Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 18 June 2022
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TUPOMS044	Dielectric Loaded THz Waveguide Experimentally Optimized by Dispersion Measurements	1526
SUSPMF027	use link to see paper's listing under its alternate paper code
	M.J. Kellermeier, R.W. Aßmann, K. Flöttmann, F. Lemery DESY, Hamburg, Germany R.W. Aßmann LNF-INFN, Frascati, Italy W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Emerging high power THz sources pave the road for THz- driven acceleration of ultra-short bunches, and enable their manipulation for diagnostic purposes. Due to the small feature sizes of THz-guiding devices new methods are necessary for their electromagnetic characterization. A new technique has recently been developed which characterizes THz waveguides with respect to their dispersion relations and attenuation. Here, the method is applied to circular waveguides, partially filled with polymer capillaries of different thicknesses, to find a suitable size for THz driven streaking at 287 GHz. Further, rough 3d-printed metallic waveguides are measured to study the effect of roughness on attenuation and phase constant. In general, additive manufacturing techniques show promise for advanced integrated designs of THz driven structures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS044
About •	Received ※ 05 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 28 June 2022
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TUPOMS045	Design Validation of High Current Injector Facility at IUAC DELHI	1530
	R.V. Hariwal, R. Ahuja, P. Barua, R.K. Gurjar, S. Kedia, A. Kothari, A. Kumar, M. Kumar, P. Kumar, R. Kumar, R. Kumar, S. Kumar, S. Kumar, P.S. Lakshmy, K. Mal, A.J. Malyadri, Y.M. Mathur, R. Mehta, DK. Munda, U.G. Naik, C. Pal, U.K. Rao, G.O. Rodrigues, C.P. Safvan, A. Sarkar, V.V.V. Satyanarayana, K. Singh, P. Singh, S.K. Sonti, S.K. Suman, T. Varughese, S.R. Venkataramanan, J. Zacharias IUAC, New Delhi, India
	High Current Injector (HCI) is an upcoming heavy ion accelerator facility at Inter-University Accelerator Centre (IUAC), New Delhi, INDIA and it will serve as an alternate injector to the existing Superconducting Linear Accelerator. HCI is designed to achieve the maximum energy gain of 1.8 MeV/u for the ions, including the Noble gasses and metallic ions, having A/q less than equal to 6. It consists of an 18 GHz High Temperature Superconducting Electron Cyclotron Resonance Ion Source, Multi-harmonic Buncher, Radio Frequency Quadrupole (RFQ), Spiral Buncher and six interdigital H-mode Drift Tube Linac (IH-DTL) cavities operating at 97 MHz resonant frequency. The RFQ accelerates the ions from 8 keV/u to 180 keV/u energy and the six DTL cavities are used to achieve the maximum energy gain of 1.8 MeV/u. Recently, the bunched beam of N⁵⁺ was successfully accelerated through RFQ and six IH-DTL cavities and we achieved the designed energy, which is an important milestone of this project. These results validate the design parameters of all RF cavities, accelerating to achieve the designed energy goal of 1.8 MeV/u. Here, present status and future plans of the project shall be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS045
About •	Received ※ 12 June 2022 — Revised ※ 17 June 2022 — Accepted ※ 30 June 2022 — Issue date ※ 05 July 2022
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TUPOMS046	Fabrication and Low-Power Test of Disk-and-Washer Cavity for Muon Acceleration	1534
	Y. Takeuchi, J. Tojo Kyushu University, Fukuoka, Japan E. Cicek, H. Ego, K. Futatsukawa, N. Kawamura, T. Mibe, M. Otani, N. Saito, T. Yamazaki, M. Yoshida KEK, Ibaraki, Japan Y. Iwashita Kyoto University, Research Reactor Institute, Osaka, Japan R. Kitamura, T. Morishita JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y. Kondo JAEA, Ibaraki-ken, Japan Y. Nakazawa Ibaraki University, Hitachi, Ibaraki, Japan Y. Sue, K. Sumi, M. Yotsuzuka Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan H.Y. Yasuda University of Tokyo, Tokyo, Japan
	The muon g-2/EDM experiment is under preparation at Japan Proton Accelerator Research Complex (J-PARC), and the muon linear accelerator for the experiment is being developed. A Disk-and-Washer (DAW) cavity will be used for the medium-velocity part of the accelerator, and muons will be accelerated from v/c=ß=0.3 to 0.7 with the operating frequency of 1.296 GHz. Machining, brazing, and low-power measurements of a prototype cell reflecting the design of the first tank of DAW were performed to identify fabrication problems. Several problems were identified, such as displacement of washers during brazing, and some measures will be taken in the actual tank fabrication. In this paper, the results of the prototype cell fabrication will be reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS046
About •	Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 23 June 2022
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TUPOMS051	Prototype Fabrication of an Active Normal Conducting Third Harmonic Cavity for the ALBA Storage Ring	1542
	J.R. Ocampo, J.M. Álvarez, B. Bravo, F. Pérez, A. Salom, P. Solans ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	Funding: Co-funded by the European Regional Development Fund (ERDF) ALBA has designed a normal conducting active 1.5 GHz HOM damped cavity for the active third harmonic RF system for the ALBA Storage Ring (SR), which also will serve for the upgraded ALBA II. The third harmonic cavity at ALBA will be used to increase the bunch length in order to improve the beam lifetime and increase the beam stability thresholds. A prototype has been constructed by the company AVS in collaboration with VITZRO. This paper presents the design of the cavity, the constructed prototype, the Acceptance Tests measurements, and the future plans.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS051
About •	Received ※ 07 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 30 June 2022 — Issue date ※ 01 July 2022
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TUPOMS054	Data Augmentation for Breakdown Prediction in CLIC RF Cavities	1553
	H.S. Bovbjerg, M. Shen, Z.H. Tan Aalborg University, Aalborg, Denmark A. Apollonio, H.S. Bovbjerg, T. Cartier-Michaud, W.L. Millar, C. Obermair, D. Wollmann CERN, Meyrin, Switzerland C. Obermair TUG, Graz, Austria
	One of the primary limitations on the achievable accelerating gradient in normal-conducting accelerator cavities is the occurrence of vacuum arcs, also known as RF breakdowns. A recent study on experimental data from the CLIC XBOX2 test stand at CERN proposes the use of supervised machine learning methods for predicting RF breakdowns. As RF breakdowns occur relatively infrequently during operation, the majority of the data was instead comprised of non-breakdown pulses. This phenomenon is known in the field of machine learning as class imbalance and is problematic for the training of the models. This paper proposes the use of data augmentation methods to generate synthetic data to counteract this problem. Different data augmentation methods like random transformations and pattern mixing are applied to the experimental data from the XBOX2 test stand, and their efficiency is compared.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS054
About •	Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 15 June 2022
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TUPOMS057	Design Study of HOM Couplers for the C-Band Accelerating Structure	1561
	D. Kim, E.I. Simakov LANL, Los Alamos, New Mexico, USA S. Biedron UNM-ECE, Albuquerque, USA Z. Li SLAC, Menlo Park, California, USA
	Funding: High Energy Physics (HEP) at the U.S. Department of Energy (DOE) A cold copper distributed coupling accelerator, with a high accelerating gradient at cryogenic temperatures (~77 K), is proposed as a baseline structure for the next generation of linear colliders. This novel technology improves accelerator performance and allows more degrees of freedom for optimization of individual cavities. It has been suggested that C-band accelerating structures at 5.712 GHz may allow to maintain high efficiency, achieve high accelerating gradient, and be suitable beam dynamics with wakefield damping and detuning of the cavities. The optimization of the cavity shape was performed and we computed quality factor, shunt impedance, and beam kick factor for each of the proposed cavity geometries using CST microwave studio. Next, we proposed a configuration for higher order mode (HOM) suppression that includes waveguide slots running parallel to the axis of the accelerator. This presentation will report details of the parametric study of performance of the HOM suppression waveguide, and the dependence of HOM Q-factors and kick-factors on the cavity’s and HOM waveguide’s geometries.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS057
About •	Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 09 July 2022
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TUPOMS058	C-Band High Gradient Testing of the Benchmark a/λ=0.105 Cavity	1564
	E.I. Simakov, V. Gorelov, T. Tajima, M.R.A. Zuboraj LANL, Los Alamos, New Mexico, USA S. Biedron Element Aero, Chicago, USA S. Biedron UNM-ECE, Albuquerque, USA M.E. Middendorf ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: Los Alamos National Laboratory LDRD Program This poster will report the results of high gradient testing of the benchmark C-band RF cavity. Modern applications such as X-ray sources require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. At LANL we commissioned a test stand (CERF-NM) powered by a 50 MW, 5.712 GHz Canon klystron. The test stand is capable of conditioning accelerating cavities for operation at surface electric fields in excess of 300 MV/m. CERF-NM is the first high gradient C-band test facility in the United States. An important milestone for this test stand is to demonstrate conditioning and high gradient testing of the most basic high gradient RF cavity with a geometry that has been extensively studied at other frequencies, such as X-band. The cavity is the three-cell structure with the highest gradient in the central cell and two coupling cells, and the ratio of the radius of the coupling iris to the wavelength a/\lamda=0.105. This presentation will report achieved gradients, breakdown probabilities, and other characteristics measured during the high power operation of this cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS058
About •	Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 17 June 2022
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TUPOMS060	High Gradient Conditioning and Performance of C-Band ß=0.5 Proton Normal- Conducting Copper and Copper-Silver Radio-Frequency Accelerating Cavities	1567
	M.R.A. Zuboraj, R.L. Fleming, V. Gorelov, J.W. Lewellen, M.E. Middendorf, E.I. Simakov LANL, Los Alamos, New Mexico, USA S.V. Baryshev, M.E. Schneider Michigan State University, East Lansing, Michigan, USA V.A. Dolgashev, E.A. Nanni, E.J.C. Snively, S.G. Tantawi SLAC, Menlo Park, California, USA E. Jevarjian MSU, East Lansing, Michigan, USA
	Funding: LANL-LDRD This work presents the results of high gradient testing of the two C-band (5.712 GHz) normal conducting ß=0.5 accelerating cavities. The first cavity was made of copper and second was made of copper-silver alloy with 0.08% silver concentration. The tests were conducted at the C-Band Engineering Research Facility of New Mexico (CERF-NM) located at Los Alamos National Laboratory Both cavities achieved gradients in excess of 200 MV/m and surface electric fields in excess of 300 MV/m. The breakdown rates were mapped as functions of the gradient and peak surface fields. The gradients and peak surface fields observed in the copper-silver cavity were about 20% higher than those in the pure copper cavity with the same breakdown rate. It was concluded that the dominant breakdown mechanism in these cavities was not the pulse heating but the breakdown due to very high surface electric fields.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS060
About •	Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 19 June 2022
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TUPOMS061	RF System Design for Elettra 2.0	1570
	C. Pasotti, M. Bocciai, L. Bortolossi, M. Rinaldi Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	The Elettra 2.0 low emittance light source project aims to a substantial increase of the brilliance and coherence fraction of the source improving, at the same time, the storage ring stability and reliability. The Radio Frequency (RF) system plays a pivotal role in the beam quality, stability and reliability for the user operation. This paper will cover the design and the implemented strategy to meet these features for the Elettra 2.0 RF system. Starting point of the new RF design is the final choice of the RF frequency, 500 MHz, and the available room, 1260 mm, to install the accelerating cavities. Thanks to the 500 MHz frequency choice, some components of the new RF system for Elettra 2.0 are already installed and set into operation in the current Elettra storage ring. Their features and performance’s optimization can therefore start well in advance with respect to the foreseen operation the new Elettra 2.0 storage ring.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS061
About •	Received ※ 06 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 04 July 2022
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FROXSP1	20-Year Collaboration on Synchrotron RF Between CERN and J-PARC	3130
	C. Ohmori J-PARC, KEK & JAEA, Ibaraki-ken, Japan M. Brucoli, M. Brugger, H. Damerau, S. Danzeca, M.M. Paoluzzi, C. Rossi CERN, Meyrin, Switzerland K. Hasegawa, Y. Morita, Y. Sugiyama, M. Yoshii KEK, Tokai, Ibaraki, Japan H. Okita, M.J. Shirakata, F. Tamura JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	KEK/J-PARC and CERN started the collaboration on the RF systems of Low Energy Ion Ring to use magnetic alloy loaded cavities in 2002 for heavy ion collision program at LHC. It was an exchange of our expertise on the wideband cavities and high-power solid-state amplifiers. This paper summarizes the 20-year collaboration which includes many synchrotrons of both facilities: J-PARC Rapid Cycling Synchrotron and Main Ring, CERN Proton Synchrotron, PS Booster, Antiproton Decelerator, Extra Low Energy Antiproton ring and MedAustron. By the improvements of cavity core using the magnetic annealing, field gradient of cavity and compactness were improved to fit the requirements for LHC Injector Upgrade (LIU)program. Radiation-hard and compact high-power solid-state amplifiers were also developed for LIU and future accelerator improvements.
	Slides FROXSP1 [8.210 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-FROXSP1
About •	Received ※ 07 June 2022 — Revised ※ 17 June 2022 — Accepted ※ 19 June 2022 — Issue date ※ 25 June 2022
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FROXSP2	Demonstration of Gradient Above 300 MV/m in Short Pulse Regime Using an X-Band Single-Cell Structure	3134
	J.H. Shao, D.S. Doran, G. Ha, C.-J. Jing, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA H.B. Chen, X. Lin, M.M. Peng, J. Shi, H. Zha TUB, Beijing, People’s Republic of China C. Jing Euclid Beamlabs, Bolingbrook, USA
	High gradient acceleration is one of the critical technologies required by future linear colliders, free-electron lasers, and compact linac-based applications. Among decade long effort to break state-of-the-art gradient limitation of ~100 MV/m in normal conducting structures, using RF pulses shorter than 20 ns is a promising approach based on theoretic analysis and experimental observation. In this study, we demonstrated high gradient above 300 MV/m using an X-band 11.7 GHz single-cell travelling-wave structure with 6 ns FWHM RF pulses generated by a power extractor. In comparison, a scaled 11.424 GHz structure only reached below 150 MV/m driven by 30-100 ns RF pulses from a klystron with pulse compression. The experimental results and the suggested new mechanism of beam acceleration in the Breakdown Insensitive Acceleration Regime (BIAR) are presented in this manuscript.
	Slides FROXSP2 [8.998 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-FROXSP2
About •	Received ※ 11 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 20 June 2022
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Paper

Title

Page

Concept and Development of 65 kW Solid-State RF Amplifiers for Sirius

868

M. Hoffmann Wallner, A.P.B. Lima
LNLS, Campinas, Brazil
R.H.A. Farias
CNPEM, Campinas, SP, Brazil

Sirius is a 4th generation synchrotron light source currently operating with 100 mA stored beam and one room temperature RF cavity driven by two 65 kW solid-state amplifiers (SSAs). After installation of the cryogenic plant, two superconducting (SC) RF cavities are planned to replace the room temperature cavity. Each SC cavity is going to be driven by a 250 kW RF signal at 500 MHz, resulting from the combination of four 65 kW RF SSAs. Due to the recent development of 900 W solid-state power amplifier modules, a new topology is proposed for the four amplifiers that still need to be constructed. For the amplifier’s combining stage, a cavity combiner with 80 input ports was simulated. For the dividing stage, 8-way and 10-way power splitters were designed. The general scheme of the amplifier is presented, as well as simulation and measurement results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST013

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Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 03 July 2022

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TUPOTK003

High Power RF Conditioning of the ESS RFQ

1189

O. Piquet, A.C. Chauveau, P. Hamel
CEA-IRFU, Gif-sur-Yvette, France
M. Baudrier, M.J. Desmons
CEA-DRF-IRFU, France
B. Jones, D. Noll, A.G. Sosa, E. Trachanas, R. Zeng
ESS, Lund, Sweden

The 352.21 MHz Radio Frequency Quadrupole (RFQ) for the European Spallation Source ERIC (ESS) has been delivered by the end of 2019 by CEA/IRFU. The RFQ is designed to accelerate a 70 mA proton beam from 75 keV up to 3.62 MeV. It consists of a 4-vane resonant cavity with a total length of 4.6 m. Two coaxial power loop couplers feed the RFQ with the 1.4 MW of RF power required for beam operation. This paper first presents the main systems required for the RFQ conditioning. Then it summarizes the main steps and results of this high power RF conditioning completed at ESS from June 9 to July 29, 2021 in order to achieve the nominal field for a pulse length of 3.2ms at the repetition rate of 14Hz.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK003

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Received ※ 08 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 09 July 2022

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TUPOTK030

X-Rays Energy Measurements During the RFQ Conditioning at the European Spallation Source

1275

E. Laface, C.G. Maiano, R. Zeng
ESS, Lund, Sweden
O. Piquet
CEA-DRF-IRFU, France

The Radio Frequency Quadrupole (RFQ) was conditioned at the European Spallation Source during spring 2021. We used part of the conditioning time to estimate the accelerating potential within the RFQ analyzing the x-rays bremsstrahlung radiation emitted by the electrons released and accelerated in the RFQ. The results of these measurements are in good agreement with the theoretical prediction.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK030

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Received ※ 16 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 27 June 2022

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TUPOMS028

3HC - Third Harmonic Normal Conducting Active Cavity Collaboration Between HZB, DESY and ALBA

1471

F. Pérez, J.R. Ocampo, A. Salom, P. Solans
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
W. Anders, V. Dürr, T. Loewner, A.N. Matveenko, M. Ries, L. Shi, Y. Tamashevich, A.V. Tsakanian
HZB, Berlin, Germany
M. Ebert, R. Onken
DESY, Hamburg, Germany
P. Hülsmann
GSI, Darmstadt, Germany
W.F.O. Müller
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Co-funded by the European Regional Development Fund (ERDF)
A collaboration agreement between the HZB, DESY and ALBA institutions was signed on 2021 in order to test the 3rd harmonic normal conducting, HOM damped, active cavity designed and prototyped by ALBA*. The test will involve low power characterization of the fundamental mode, bead pull measurements to fully determine the HOM characteristics, a full high power conditioning to validate the power capability of the cavity, and finally, the installation of the cavity in the BESSY II storage ring in order to test the cavity in real conditions with beam. In this paper the low power, bead pull and conditioning results will be presented. The cavity has been installed at BESSY II on May 2022 to be tested after the summer shutdown.
* Prototype fabrication of an active normal conducting third harmonic cavity for the ALBA Storage Ring. J.Ocampo et al. , IPAC 2022 proceedings.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS028

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Received ※ 06 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 02 July 2022

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TUPOMS038

RFQ NEWGAIN: RF and Thermomechanical Design

1510

P. Hamel, N. Sellami
CEA-IRFU, Gif-sur-Yvette, France
M.J. Desmons, O. Piquet, B. Prevet
CEA-DRF-IRFU, France

Funding: Agence Nationale de la Recherche (ANR)
A new injector called NEWGAIN will be added to the SPIRAL2 Linear Accelerator (LINAC), in parallel with the existing one. It will be mainly composed of an ion source and a Radio Frequency Quadrupole (RFQ) connected to the superconductive LINAC of SPIRAL2. The new RFQ will accelerate at 88.05 MHz particles with charge-over-mass ratio (Q/A) between 1/3 and 1/7, from 10 keV/u up to 590 keV/u. It consists of a 4-vane resonant cavity with a total length of 7 m. It is a CW machine that has to show stable operation, provide the request availability, have the minimum losses in order to provide the highest current to the superconductive LINAC and show the best quality/cost ratio. This paper will present the preliminary RF design and the thermomechanical study for this RFQ.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS038

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Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 27 June 2022

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TUPOMS040

Characterization of Higher-Order-Modes (HOM) in THOMX Storage Ring RF Cavity

1513

M. El Khaldi, J-N. Cayla, H. Monard
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
M. Diop, F. Ribeiro
SOLEIL, Gif-sur-Yvette, France

The RF system of the ThomX storage ring consists in a 500 MHz single cell copper cavity of the ELETTRA type, powered with a 50 kW CW solid state amplifier, and the associated Low-Level RF feedback and control loops. The low operating energy of 50-100 MeV makes the impedances of the cavity higher order modes (HOMs) particularly critical for the beam stability. Their parasitic effects on the beam can be cured by HOM frequency shifting techniques, based on a fine temperature tuning and a dedicated adjustable plunger. A cavity temperature stability of ± 0.1 °C within a range from 30 up to 70 °C is achieved by a precise control of its water-cooling temperature. On the other hand, the tuning of the cavity fundamental mode is achieved by changing its axial length by means of a mechanical tuner. In order to insure a fine control of the HOM frequencies, a good knowledge of their characteristics is mandatory. The main parameters of the fundamental and of the HOMs up to 2.2 GHz versus temperature have been measured at low power using a vector network analyzer (VNA).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS040

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Received ※ 03 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 21 June 2022

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TUPOMS041

High Power RF-Cavity Development for the HBS-Driver LINAC

1516

M. Basten, K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, M. Vossberg, S. Yaramyshev
GSI, Darmstadt, Germany
K. Aulenbacher, W.A. Barth, M. Basten, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu
HIM, Mainz, Germany
K. Aulenbacher, W.A. Barth, F.D. Dziuba, S. Lauber, J. List
KPH, Mainz, Germany
T. Gutberlet
JCNS, Jülich, Germany
H. Podlech
IAP, Frankfurt am Main, Germany
H. Podlech
HFHF, Frankfurt am Main, Germany

Neutron research in Europe is mainly based on various nuclear reactors that will be successively decommissioned over the next years. This means that despite the commissioning of the European Spallation Source ESS, many neutron research centres, especially in the medium flux regime, will disappear. In response to this situation, the Jülich Centre for Neutron Science (JCNS) has begun the development of a scalable, compact, accelerator-based High Brilliance neutron Source (HBS). A total of three different neutron target stations are planned, which can be operated with a 100 mA proton beam of up to 70 MeV and a duty cycle of up to 6%. The driver Linac consists of an Electron Cyclotron Resonance (ECR) ion source followed by a LEBT section, a 2.5 MeV double Radio-Frequency Quadrupole (RFQ) and 35 normal conducting (NC) Crossbar H-Mode (CH) cavities. The development of the cavities is carried out by the Institute for Applied Physics (IAP) at the Goethe University Frankfurt am Main. Due to the high beam current, all cavities as well as the associated tuners and couplers have to be optimised for operation under high thermal load to ensure safe operation. In collaboration with the GSI Centre for Heavy Ion Research as the ideal test facility for high power tests, two cavities and the associated hardware are being designed and will be tested. The design and latest status of both cavities will be presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS041

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Received ※ 18 May 2022 — Revised ※ 15 June 2022 — Accepted ※ 28 June 2022 — Issue date ※ 06 July 2022

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TUPOMS042

Cavity R&D for HBS Accelerator

1520

N.F. Petry, K. Kümpel, S. Lamprecht, O. Meusel, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany

The demand for neutrons of various types for research is growing day by day worldwide. To meet the growing demand the Jülich High Brilliance Neutron Source (HBS) is in development. It is based on a high power linear proton accelerator with an end energy of 70 MeV and a proton beam current of 100 mA. After the injector and the MEBT is the main part of the accelerator, which consists of about 36 CH-type cavities. The design of the CH-type cavities will be optimized in terms of required power, required cooling and reliability and the recent results will be presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS042

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Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 15 June 2022

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TUPOMS043

High Power Tests of a New 4-Rod RFQ with Focus on its Mechanical Vibrations

1523

S.R. Wagner, D. Koser, K. Kümpel, H. Podlech
IAP, Frankfurt am Main, Germany
K.B. Bahrke-Rein
TU Darmstadt, Darmstadt, Germany
M. Basten
GSI, Darmstadt, Germany
M. Basten
HIM, Mainz, Germany
H. Podlech
HFHF, Frankfurt am Main, Germany

Because of strong mechanical vibrations of the electrodes and its sensitivity to changes of thermal load, the operational stability of the existing 4-rod RFQ at the High Charge State Injector (HLI) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, could not be ensured for all planned operating states. To resolve this issue and ensure stable injection into the HLI, a new RFQ-prototype, optimized in terms of vibration suppression and cooling efficiency, was designed at the Institute of Applied Physics (IAP) of Goethe University Frankfurt. To test the performance of this prototype and demonstrate the operational stability in terms of mechanical vibration as well as thermal load, high power tests with more than 25’kW/m were performed at GSI. After initial conditioning, detailed vibrational measurements during high power RF operation using a laser Doppler vibrometer were performed, which were then compared to previously conducted simulations using ANSYS. Ultimately, the ability for stable operation up to high power levels with an efficient vibration suppression and moderate heating have clearly been demonstrated.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS043

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Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 18 June 2022

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TUPOMS044

Dielectric Loaded THz Waveguide Experimentally Optimized by Dispersion Measurements

1526

SUSPMF027

use link to see paper's listing under its alternate paper code

M.J. Kellermeier, R.W. Aßmann, K. Flöttmann, F. Lemery
DESY, Hamburg, Germany
R.W. Aßmann
LNF-INFN, Frascati, Italy
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Emerging high power THz sources pave the road for THz- driven acceleration of ultra-short bunches, and enable their manipulation for diagnostic purposes. Due to the small feature sizes of THz-guiding devices new methods are necessary for their electromagnetic characterization. A new technique has recently been developed which characterizes THz waveguides with respect to their dispersion relations and attenuation. Here, the method is applied to circular waveguides, partially filled with polymer capillaries of different thicknesses, to find a suitable size for THz driven streaking at 287 GHz. Further, rough 3d-printed metallic waveguides are measured to study the effect of roughness on attenuation and phase constant. In general, additive manufacturing techniques show promise for advanced integrated designs of THz driven structures.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS044

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Received ※ 05 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 28 June 2022

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TUPOMS045

Design Validation of High Current Injector Facility at IUAC DELHI

1530

R.V. Hariwal, R. Ahuja, P. Barua, R.K. Gurjar, S. Kedia, A. Kothari, A. Kumar, M. Kumar, P. Kumar, R. Kumar, R. Kumar, S. Kumar, S. Kumar, P.S. Lakshmy, K. Mal, A.J. Malyadri, Y.M. Mathur, R. Mehta, DK. Munda, U.G. Naik, C. Pal, U.K. Rao, G.O. Rodrigues, C.P. Safvan, A. Sarkar, V.V.V. Satyanarayana, K. Singh, P. Singh, S.K. Sonti, S.K. Suman, T. Varughese, S.R. Venkataramanan, J. Zacharias
IUAC, New Delhi, India

High Current Injector (HCI) is an upcoming heavy ion accelerator facility at Inter-University Accelerator Centre (IUAC), New Delhi, INDIA and it will serve as an alternate injector to the existing Superconducting Linear Accelerator. HCI is designed to achieve the maximum energy gain of 1.8 MeV/u for the ions, including the Noble gasses and metallic ions, having A/q less than equal to 6. It consists of an 18 GHz High Temperature Superconducting Electron Cyclotron Resonance Ion Source, Multi-harmonic Buncher, Radio Frequency Quadrupole (RFQ), Spiral Buncher and six interdigital H-mode Drift Tube Linac (IH-DTL) cavities operating at 97 MHz resonant frequency. The RFQ accelerates the ions from 8 keV/u to 180 keV/u energy and the six DTL cavities are used to achieve the maximum energy gain of 1.8 MeV/u. Recently, the bunched beam of N⁵⁺ was successfully accelerated through RFQ and six IH-DTL cavities and we achieved the designed energy, which is an important milestone of this project. These results validate the design parameters of all RF cavities, accelerating to achieve the designed energy goal of 1.8 MeV/u. Here, present status and future plans of the project shall be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS045

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Received ※ 12 June 2022 — Revised ※ 17 June 2022 — Accepted ※ 30 June 2022 — Issue date ※ 05 July 2022

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TUPOMS046

Fabrication and Low-Power Test of Disk-and-Washer Cavity for Muon Acceleration

1534

Y. Takeuchi, J. Tojo
Kyushu University, Fukuoka, Japan
E. Cicek, H. Ego, K. Futatsukawa, N. Kawamura, T. Mibe, M. Otani, N. Saito, T. Yamazaki, M. Yoshida
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto University, Research Reactor Institute, Osaka, Japan
R. Kitamura, T. Morishita
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y. Kondo
JAEA, Ibaraki-ken, Japan
Y. Nakazawa
Ibaraki University, Hitachi, Ibaraki, Japan
Y. Sue, K. Sumi, M. Yotsuzuka
Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
H.Y. Yasuda
University of Tokyo, Tokyo, Japan

The muon g-2/EDM experiment is under preparation at Japan Proton Accelerator Research Complex (J-PARC), and the muon linear accelerator for the experiment is being developed. A Disk-and-Washer (DAW) cavity will be used for the medium-velocity part of the accelerator, and muons will be accelerated from v/c=ß=0.3 to 0.7 with the operating frequency of 1.296 GHz. Machining, brazing, and low-power measurements of a prototype cell reflecting the design of the first tank of DAW were performed to identify fabrication problems. Several problems were identified, such as displacement of washers during brazing, and some measures will be taken in the actual tank fabrication. In this paper, the results of the prototype cell fabrication will be reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS046

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Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 23 June 2022

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TUPOMS051

Prototype Fabrication of an Active Normal Conducting Third Harmonic Cavity for the ALBA Storage Ring

1542

J.R. Ocampo, J.M. Álvarez, B. Bravo, F. Pérez, A. Salom, P. Solans
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

Funding: Co-funded by the European Regional Development Fund (ERDF)
ALBA has designed a normal conducting active 1.5 GHz HOM damped cavity for the active third harmonic RF system for the ALBA Storage Ring (SR), which also will serve for the upgraded ALBA II. The third harmonic cavity at ALBA will be used to increase the bunch length in order to improve the beam lifetime and increase the beam stability thresholds. A prototype has been constructed by the company AVS in collaboration with VITZRO. This paper presents the design of the cavity, the constructed prototype, the Acceptance Tests measurements, and the future plans.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS051

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Received ※ 07 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 30 June 2022 — Issue date ※ 01 July 2022

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TUPOMS054

Data Augmentation for Breakdown Prediction in CLIC RF Cavities

1553

H.S. Bovbjerg, M. Shen, Z.H. Tan
Aalborg University, Aalborg, Denmark
A. Apollonio, H.S. Bovbjerg, T. Cartier-Michaud, W.L. Millar, C. Obermair, D. Wollmann
CERN, Meyrin, Switzerland
C. Obermair
TUG, Graz, Austria

One of the primary limitations on the achievable accelerating gradient in normal-conducting accelerator cavities is the occurrence of vacuum arcs, also known as RF breakdowns. A recent study on experimental data from the CLIC XBOX2 test stand at CERN proposes the use of supervised machine learning methods for predicting RF breakdowns. As RF breakdowns occur relatively infrequently during operation, the majority of the data was instead comprised of non-breakdown pulses. This phenomenon is known in the field of machine learning as class imbalance and is problematic for the training of the models. This paper proposes the use of data augmentation methods to generate synthetic data to counteract this problem. Different data augmentation methods like random transformations and pattern mixing are applied to the experimental data from the XBOX2 test stand, and their efficiency is compared.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS054

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Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 15 June 2022

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TUPOMS057

Design Study of HOM Couplers for the C-Band Accelerating Structure

1561

D. Kim, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
S. Biedron
UNM-ECE, Albuquerque, USA
Z. Li
SLAC, Menlo Park, California, USA

Funding: High Energy Physics (HEP) at the U.S. Department of Energy (DOE)
A cold copper distributed coupling accelerator, with a high accelerating gradient at cryogenic temperatures (~77 K), is proposed as a baseline structure for the next generation of linear colliders. This novel technology improves accelerator performance and allows more degrees of freedom for optimization of individual cavities. It has been suggested that C-band accelerating structures at 5.712 GHz may allow to maintain high efficiency, achieve high accelerating gradient, and be suitable beam dynamics with wakefield damping and detuning of the cavities. The optimization of the cavity shape was performed and we computed quality factor, shunt impedance, and beam kick factor for each of the proposed cavity geometries using CST microwave studio. Next, we proposed a configuration for higher order mode (HOM) suppression that includes waveguide slots running parallel to the axis of the accelerator. This presentation will report details of the parametric study of performance of the HOM suppression waveguide, and the dependence of HOM Q-factors and kick-factors on the cavity’s and HOM waveguide’s geometries.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS057

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Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 09 July 2022

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TUPOMS058

C-Band High Gradient Testing of the Benchmark a/λ=0.105 Cavity

1564

E.I. Simakov, V. Gorelov, T. Tajima, M.R.A. Zuboraj
LANL, Los Alamos, New Mexico, USA
S. Biedron
Element Aero, Chicago, USA
S. Biedron
UNM-ECE, Albuquerque, USA
M.E. Middendorf
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: Los Alamos National Laboratory LDRD Program
This poster will report the results of high gradient testing of the benchmark C-band RF cavity. Modern applications such as X-ray sources require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. At LANL we commissioned a test stand (CERF-NM) powered by a 50 MW, 5.712 GHz Canon klystron. The test stand is capable of conditioning accelerating cavities for operation at surface electric fields in excess of 300 MV/m. CERF-NM is the first high gradient C-band test facility in the United States. An important milestone for this test stand is to demonstrate conditioning and high gradient testing of the most basic high gradient RF cavity with a geometry that has been extensively studied at other frequencies, such as X-band. The cavity is the three-cell structure with the highest gradient in the central cell and two coupling cells, and the ratio of the radius of the coupling iris to the wavelength a/\lamda=0.105. This presentation will report achieved gradients, breakdown probabilities, and other characteristics measured during the high power operation of this cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS058

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Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 17 June 2022

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TUPOMS060

High Gradient Conditioning and Performance of C-Band ß=0.5 Proton Normal- Conducting Copper and Copper-Silver Radio-Frequency Accelerating Cavities

1567

M.R.A. Zuboraj, R.L. Fleming, V. Gorelov, J.W. Lewellen, M.E. Middendorf, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
S.V. Baryshev, M.E. Schneider
Michigan State University, East Lansing, Michigan, USA
V.A. Dolgashev, E.A. Nanni, E.J.C. Snively, S.G. Tantawi
SLAC, Menlo Park, California, USA
E. Jevarjian
MSU, East Lansing, Michigan, USA

Funding: LANL-LDRD
This work presents the results of high gradient testing of the two C-band (5.712 GHz) normal conducting ß=0.5 accelerating cavities. The first cavity was made of copper and second was made of copper-silver alloy with 0.08% silver concentration. The tests were conducted at the C-Band Engineering Research Facility of New Mexico (CERF-NM) located at Los Alamos National Laboratory Both cavities achieved gradients in excess of 200 MV/m and surface electric fields in excess of 300 MV/m. The breakdown rates were mapped as functions of the gradient and peak surface fields. The gradients and peak surface fields observed in the copper-silver cavity were about 20% higher than those in the pure copper cavity with the same breakdown rate. It was concluded that the dominant breakdown mechanism in these cavities was not the pulse heating but the breakdown due to very high surface electric fields.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS060

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Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 19 June 2022

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TUPOMS061

RF System Design for Elettra 2.0

1570

C. Pasotti, M. Bocciai, L. Bortolossi, M. Rinaldi
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

The Elettra 2.0 low emittance light source project aims to a substantial increase of the brilliance and coherence fraction of the source improving, at the same time, the storage ring stability and reliability. The Radio Frequency (RF) system plays a pivotal role in the beam quality, stability and reliability for the user operation. This paper will cover the design and the implemented strategy to meet these features for the Elettra 2.0 RF system. Starting point of the new RF design is the final choice of the RF frequency, 500 MHz, and the available room, 1260 mm, to install the accelerating cavities. Thanks to the 500 MHz frequency choice, some components of the new RF system for Elettra 2.0 are already installed and set into operation in the current Elettra storage ring. Their features and performance’s optimization can therefore start well in advance with respect to the foreseen operation the new Elettra 2.0 storage ring.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS061

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Received ※ 06 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 04 July 2022

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FROXSP1

20-Year Collaboration on Synchrotron RF Between CERN and J-PARC

3130

C. Ohmori
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
M. Brucoli, M. Brugger, H. Damerau, S. Danzeca, M.M. Paoluzzi, C. Rossi
CERN, Meyrin, Switzerland
K. Hasegawa, Y. Morita, Y. Sugiyama, M. Yoshii
KEK, Tokai, Ibaraki, Japan
H. Okita, M.J. Shirakata, F. Tamura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

KEK/J-PARC and CERN started the collaboration on the RF systems of Low Energy Ion Ring to use magnetic alloy loaded cavities in 2002 for heavy ion collision program at LHC. It was an exchange of our expertise on the wideband cavities and high-power solid-state amplifiers. This paper summarizes the 20-year collaboration which includes many synchrotrons of both facilities: J-PARC Rapid Cycling Synchrotron and Main Ring, CERN Proton Synchrotron, PS Booster, Antiproton Decelerator, Extra Low Energy Antiproton ring and MedAustron. By the improvements of cavity core using the magnetic annealing, field gradient of cavity and compactness were improved to fit the requirements for LHC Injector Upgrade (LIU)program. Radiation-hard and compact high-power solid-state amplifiers were also developed for LIU and future accelerator improvements.

Slides FROXSP1 [8.210 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-FROXSP1

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Received ※ 07 June 2022 — Revised ※ 17 June 2022 — Accepted ※ 19 June 2022 — Issue date ※ 25 June 2022

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FROXSP2

Demonstration of Gradient Above 300 MV/m in Short Pulse Regime Using an X-Band Single-Cell Structure

3134

J.H. Shao, D.S. Doran, G. Ha, C.-J. Jing, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
H.B. Chen, X. Lin, M.M. Peng, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China
C. Jing
Euclid Beamlabs, Bolingbrook, USA

High gradient acceleration is one of the critical technologies required by future linear colliders, free-electron lasers, and compact linac-based applications. Among decade long effort to break state-of-the-art gradient limitation of ~100 MV/m in normal conducting structures, using RF pulses shorter than 20 ns is a promising approach based on theoretic analysis and experimental observation. In this study, we demonstrated high gradient above 300 MV/m using an X-band 11.7 GHz single-cell travelling-wave structure with 6 ns FWHM RF pulses generated by a power extractor. In comparison, a scaled 11.424 GHz structure only reached below 150 MV/m driven by 30-100 ns RF pulses from a klystron with pulse compression. The experimental results and the suggested new mechanism of beam acceleration in the Breakdown Insensitive Acceleration Regime (BIAR) are presented in this manuscript.

Slides FROXSP2 [8.998 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-FROXSP2

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Received ※ 11 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 20 June 2022

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