| Paper | Title | Page |
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| WEPRB001 | The Effect of the SLED Installation on Extracted and Lost Beam at the Australian Synchrotron Linac. | 2794 |
| SUSPFO001 | use link to see paper's listing under its alternate paper code | |
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| A recent upgrade to the high power RF network of the linac at the Australian Synchrotron included a SLED Type 1 Pulse Compressor allowing for the operation of its 100 MeV linac using a single klystron. We explore the effects of the SLED installation on the properties of the beam extracted from the linac with a particular focus on the energy spread and bunch train profile. Additionally, the optical fibre beam loss monitor (oBLM), also recently commissioned, was employed to provide shot-by-shot feedback on loss location and intensity to investigate the change in beam losses. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB001 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB003 | Parametric Pumped Oscillation by Lorentz Force in Superconducting Rf Cavity | 2798 |
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| Mechanical instabilities have been observed in superconducting RF cavities, when multiple cavities are driven by a single klystron and these cavities are regulated by vector-summing the outputs from these cavities. A nonlinear theory has been developed to study the source of this mechanical instability, which is due to the coupling between Lorentz force detuning and mechanical oscillation by parametric pumping. Analytical and numerical analysis of this model show regions of stability, limit cycles and instabilities. These results are in agreement with the observed oscillations by TRIUMF eLinac Acceleration Module. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB003 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB004 | Sawtooth Generation and Regulation with a Single FPGA for TRIUMF’s ARIEL Prebuncher | 2801 |
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| TRIUMF’s ARIEL prebuncher is powered by a sawtooth waveform which is the combination of an 11.79MHz, a 23.57MHz and a 35.36MHz components. The generation, control and regulation of these three components are all incorporated digitally inside a single FPGA. This FPGA can be standalone or inserted inside a VXI module. Commands and controls of these components can be directly through Ethernet, or indirectly through register-base or message-base VXI addresses. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB004 | |
| About • | paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB007 | RF Commissioning of the SPIRAL2 RFQ in CW Mode and Beyond Nominal Field | 2804 |
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| The SPIRAL2 RFQ was recently successfully commissioned at nominal voltage of 114 kV, corresponding to 1.65 Kilpatrick factor. The paper describes limitations of the RFQ main subsystems, cavity conditioning difficulties, as well as changes implemented in the LLRF and automatic procedures to simplify turn on and operation of the whole system. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB007 | |
| About • | paper received ※ 26 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB008 | Design Study of High Gradient Compact S-band TW Accelerating Structure for the ThomX LINAC Upgrade | 2807 |
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| ThomX is a Compton source project in the range of the hard X rays (45/90 keV). The machine is composed of a 50/70 MeV injector Linac and a storage ring where an electron bunch collides with a laser pulse accumulated in a Fabry-Perot resonator. The final goal is to provide an X-rays average flux of 1012-1013 ph/s. A demonstrator was funded and is being built on the Orsay university campus. The S-band injector Linac consists of 2.5 cell photocathode RF gun and a TW accelerating section. During the commissioning phase, a standard LIL S-band accelerating section is able to achieve around 50 MeV corresponding to around 45 keV X-rays energy. Since the maximum targeted X-ray energy is 90 keV, the development of a new S-band accelerating section, intended to replace the LIL structure, will provide an electron beam energy of 70 MeV. This requires essentially the development of more reliable high gradient compact S band accelerating section. Such design is tailored for high gradient operation, low breakdown rates. We present here the RF design of the LINAC upgrade and the performances obtained in terms of beam dynamics. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB008 | |
| About • | paper received ※ 02 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB009 | Validation of the Series Power Couplers of the LIPAc SRF Linac | 2811 |
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| In the framework of the IFMIF/EVEDA project, the cryomodule of the Linear IFMIF Prototype Accelerator (LIPAc) will be assembled then tested at Rokkasho in 2019. Eight Series Power Couplers (PC) operating at 175 MHz were manufactured under a CEA contract, in order to equip this Cryomodule. They were all successfully RF conditioned up to 100 kW CW in TW and SW configurations. All the high RF power tests were performed under CIEMAT responsibility in BTESA Company premises, according to the CEA requirements. In order to fix difficulties encountered during the fab process, manufacturing and quality control have been analyzed in depth. Thanks to the corrective actions implemented, every PC reached the performances targeted for qualification. This paper will give details about this manufacturing phase and provide an overview of the obtained RF test results. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB009 | |
| About • | paper received ※ 09 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB010 | RF Power Test of the Rebuncher for Saraf-Linac | 2815 |
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Funding: SNRC Three normal conducting rebunchers will be installed at the Medium Energy Beam Transport (MEBT) of the SARAF-LINAC phase II [saraf]. The MEBT line is designed to follow a 1.3 MeV/u RFQ, is about 5 m long, and contains three 176 MHz rebunchers providing a field integral of 105 kV. CEA is in charge of the design and fabrication of the Cu plated stainless steel, 3-gap rebuncher. The high power tests and RF conditioning have been successfully performed at the CEA Saclay on the first cavity. A solid state power amplifier, which has been developed by SNRC and has been used for the RF tests. The cavity has shown a good performance according to calculations, regarding the dissipated power, peak temperatures and coupling factor. RF conditioning was started with a duty cycle of 1\% and increased gradually until continuous wave (CW), which is the nominal working mode in SARAF-LINAC. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB010 | |
| About • | paper received ※ 09 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB011 | PVD Depostion of Nb3Sn Thin Film on Copper Substrate from an Alloy Nb3Sn Target | 2818 |
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| In this study we report on the PVD deposition of Nb3Sn on Cu substrates with and without a thick Nb interlayer to produce Cu/Nb/Nb3Sn and Cu/Nb3Sn multilayer structures. The Nb3Sn was sputtered directly from an alloy target at room and elevated temperatures. The dependence of the superconducting properties of the total structure on deposition parameters has been determined. The films have been characterized via SEM, XRD, EDX and SQUID magnetometer measurements. Analysis showed that the composition at both room and elevated temperature was within the desired stoichiometry of 24’25 at%. However, superconductivity was only observed for deposition at elevated temperature or post annealing at 650 °C. The critical temperature was determined to be in the range of 16.8 to 17.4 K. In the case of bilayer deposition, copper segregation from the interface all the way to the surface was observed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB011 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB012 | Overview on SC CH-Cavity Development | 2822 |
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Funding: Work supported by GSI, HIC for FAIR, BMBF Contr. No. 05P18RFRB1 During the last decades an enermous effort has been put into the development of low beta structures for hadron acceleration worldwide. Since hadrons exhibit a very inert velocity gain due to their high mass this change in speed has to be taken into account when utilizing low beta cavities. At the Institute of Applied Physics (IAP), Frankfurt, Germany, five multi-cell CH-cavities (Crossbar H-Mode) have been developed and tested for different kind of applications so far. In addition to the successfully tested original 360 MHz prototype further structures envisaged for beam operation have been fabricated and tested. Overview, status and outlook of this cavity technology is topic of this contribution. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB012 | |
| About • | paper received ※ 08 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB014 | Further RF Measurements on the Superconducting 217 MHz CH Demonstrator Cavity for a CW Linac at GSI | 2826 |
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Funding: Work supported by GSI, HIM, BMBF Contr. No. 05P18UMRB2 Recently, the first section of the superconducting (sc) continuous wave (cw) Linac has been extensively tested with heavy ion beam from the GSI High Charge State Injector (HLI). During this testing phase, the reliable operability of 217 MHz multi gap crossbar-H-mode (CH) cavities has been successfully demonstrated. The sc 217 MHz CH cavity (CH0) of the demonstrator setup accelerated heavy ions up to the design beam energy and even beyond at high beam intensities and full transmission. This worldwide first beam test with a sc CH cavity is a major milestone on the way realizing the entire sc cw Linac project. In this contribution further RF measurements on the cavity are presented providing full characterization of the RF structure. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB014 | |
| About • | paper received ※ 26 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB015 | Cleanroom Installations for SRF Cavities at the Helmholtz-Institut Mainz | 2830 |
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| At the Helmholtz-Institut Mainz (HIM) a cleanroom has been equipped with new tools and installations for the planned treatment of different superconducting RF-cavities. At first TESLA/XFEL type 9-cell cavities for the Mainz Energy-Recovering Superconducting Accelerator (MESA) project or 217 MHz multigap Crossbar H-mode cavities for the HElmholtz LInear ACcelerator (HELIAC) under development by HIM and GSI will be treated. The cleanroom installations, including the greyroom, cover an area of about 155 sqm. In its ISO-class 6 area a large ultrasonic and a conductance rinsing bath has been installed recently. A high pressure rinsing cabinet (HPR) has been implemented between the ISO-class 6 and 4 cleanroom. A RF-cavity can be loaded and unloaded from both sides. HPR treatments are possible for cavities of up to 1.4 m length and about 0.7 m diameter. For drying the ISO-class 4 clean room is equipped with a 160 C vacuum oven. New cleanroom lifters allow the handling of up to 200 kg heavy objects. A rail system in the cleanroom floor is installed to move out the entire cold string of the cleanroom after assembly and leak testing. First operational experiences with this facility will be presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB015 | |
| About • | paper received ※ 29 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB016 | Simulation of Quench Detection Algorithms for Helmholtz Zentrum Berlin SRF Cavities | 2834 |
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| The Helmholtz Zentrum Berlin is carrying out two accelerator projects which make use of high gradient SRF cavities: BERLinPro* and BESSY-VSR**. In both projects, a prompt detection of a quench is crucial to avoid damages in the cryomodules and cavities themselves. In this paper, the response of real time estimation of the cavity parameters*** using the transmitted and forward RF signals is simulated, in order to perform the quench detection. The time response of the estimated half bandwidth is compared with the dissipated power in the cavity walls for the different type of SRF cavities used in both projects, i.e., BERLinPro’s photoinjector, booster and linac, and BESSY-VSR 1.5 GHz and 1.75 GHz cavities. As an intermediate step prior to the implementation in an mTCA.4 system together with the LLRF control and test with a real cavity, the algorithm has been implemented using a National Instruments FPGA board to check the its proper behavior. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB016 | |
| About • | paper received ※ 16 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB017 | Operational Experiences with X-Ray Tomography for SRF Cavity Shape and Surface Control | 2838 |
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| X-ray tomography has established as a non-destructive three-dimensional analysis tool, commercially offered by industrial vendors. Typical applications cover shape control and failure detection (voids, cracks) deep inside of complicated bulk pieces like engine blocks, bearings, turbine blades etc. We evaluated the applicability of the process for superconducting radio frequency cavities, in particular the 1.4-cell 1.3 GHz BERLinPro electron gun cavity and the 1.5 GHz single-cell VSR cavity prototype. The former experienced severe shape modifications during its tuning process and features a complicated internal stiffening construction. Thus it is a demanding challenge to measure its actual internal cavity surface shape after the complete preparation process with a resolution, sufficiently high (better than 0.2 mm) to serve as input for meaningful comparative field simulations. First tests with a vendor’s on-site X-ray source, operating at X-ray energies up to 590 keV revealed an insufficient resolution of the inner surface, attributed to the unfavorable X-ray damping characteristics of niobium. This was overcome with the aid of an accelerator-based source (X-ray spectrum up to 9 MeV), operated by Fraunhofer IIS, Fürth, Germany. Results both show significant, while understood, shape changes and indicate partial inner surface modifications of the gun cavity. Further the data evaluation process, which was needed to provide input for field simulations, raised issues because of the data set size and complexity, which are discussed in the paper. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB017 | |
| About • | paper received ※ 17 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB020 | Compact Ultra High-Gradient Ka-Band Accelerating Structure for Research, Medical and Industrial Applications | 2842 |
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| Technological advancements are strongly required to fulfil demands for new accelerators devices from the compact or portable devices for radiotherapy to mo-bile cargo inspections and security, biology, energy and environmental applications, and ultimately for the next generation of colliders. In the frame of the collab-oration with INFN-LNF, SLAC (USA) we are working closely on design studies, fabrication and high-power operation of Ka-band accelerating structures. In par-ticular, new manufacturing techniques for hard-copper structures are being investigated in order to determine the maximum sustainable gradients above 150 MV/m and extremely low probability of RF breakdown. In this paper, the preliminary RF and mechanical design as well as beam dynamics estimations for a Ka-Band accelerating structure at 35 GHz are presented together with discussions on practical accelerating gradients and maximum average beam current throughput. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB020 | |
| About • | paper received ※ 08 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB021 | Commissioning of S-band Cavity Test Facility at Elettra for Conditioning of High Gradient Structures for the Fermi Linac Upgrade | 2846 |
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| FERMI is the seeded Free Electron Laser (FEL) user facility at Elettra laboratory in Trieste, operating in the VUV to soft X-rays spectral range. In order to extend the FEL spectral range to shorter wavelengths, a feasibility study for increasing the Linac energy from 1.5 GeV to 1.8 GeV is actually going on. A short prototype of a new High Gradient (HG) S-band accelerating structure has been built in collaboration with Paul Scherrer Institute (PSI). The new structures are intended to replace the present Backward Travelling Wave (BTW) sections and tailored to be operated at a gradient of 30 MV/m. For RF conditioning and high power testing of prototype, a Cavity Test Facility (CTF) is commissioned at FERMI. The test facility is equipped with RF pulse compressor system and a dedicated diagnostic for breakdown rate (BDR) measurements and events localization. In this paper we present in detail cavity test facility of FERMI and high power testing of the first prototype. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB021 | |
| About • | paper received ※ 08 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB022 | RF System Upgrade for Elettra 2.0 | 2849 |
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| The Elettra 2.0 low emittance light source project has triggered the review of the installed RF system’s performances and the analyses of the new machine requirement. This study includes the imperative revamp of the RF power sources. The trade off between the best theoretical RF system design and the available room for installation and budget for Elettra 2.0 has been translated into the operational plan reported here. The first planned step is the installation of 100 kW 500 MHz solid state based transmitters. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB022 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB023 | Vertical Test of ESS Medium Beta Cavities | 2852 |
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| The Medium beta (β=0.67) section of the European Spallation Source (ESS) Linac is composed of 36 six-cell elliptical superconducting (SC) cavities. As a part to the in kind contribution of Italy to the ESS project, INFN-LASA is in charge of the development and of the industrial production of the whole set of 36 resonators plus two spares. The production activity is now ongoing at ZANON. To qualify the cavities power tests in vertical cryostat has been committed to DESY. During the qualification tests, where the cavities provided with He tanks are pushed to their electromagnetic limits, recording their main electromagnetics parameters such as quality factor Q0 vs Eacc. In this paper we report about the qualification tests performed on the first part of the quality production. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB023 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB024 | Low Power RF Test of a Quadrupole-free X-Band Mode Launcher for High Brightness Applications | 2856 |
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| In this work we present the low power RF characterization of a novel TM01 X-band mode launcher for the new generation of high brightness RF photo-injectors. The proposed mode launcher exploits a fourfold symmetry which minimizes both the dipole and the quadrupole fields in order to mitigate the emittance growth in the early stages of the acceleration process. Two identical aluminum mode launchers have been assembled and measured in back-to-back configurations for three different central waveguide lengths. From the back-to-back results we infer the performance of each mode launcher. The low power RF test, performed at the Istituto Nazionale di Fisica Nucleare Laboratori Nazionali del Sud (INFN-LNS), validate both the numerical simulations and the quality of fabrication. An oxygen-free high-conductivity copper version of the device is being manufactured for high power and ultra high vacuum tests that are planned to be conducted at SLAC | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB024 | |
| About • | paper received ※ 09 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB025 | High Density Mapping for Superconducting Cavities | 2860 |
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| High density mapping system for superconducting cavities are under development. Testing on the stiffener X-ray mapping system at JLAB showed consistent results in comparison with simultaneously taken GM tube or ion chamber output signals. The system provides better visi-bility as shown by data briefly reported here. In addition to the temperature and the X-ray mapping, a sensitive magnetic field mapping system with high spatial density is also under development. The magnetic field sensor is AF755B, whose operations at cryogenic temperatures are already reported by other group. Our development status using the magnetic field sensor will be reported. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB025 | |
| About • | paper received ※ 19 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB026 | Simulations of Beam Loading Compensation in a Wideband Accelerating Cavity Using a Circuit Simulator Including a LLRF Feedback Control | 2863 |
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| Magnetic alloy cavities are employed in the J-PARC RCS to generate high accelerating voltages. The cavity, which is driven by a vacuum tube amplifier, has a wideband frequency response and the beam loading in the cavity is multiharmonic. Therefore, the tube must generate a multiharmonic output current. An LTspice circuit model is developed to analyze the vacuum tube operation and the compensation of the multiharmonic beam loading. The model includes the cavity, tube amplifier, beam current, and LLRF feedback control. The feedback control consists of the I/Q demodulator including low pass filters, PI control, and I/Q modulator. In this presentation, we present the implementation of the LLRF functions in the LTspice simulations. The preliminary simulation results are also presented. The simulations fairly agree with the beam test results. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB026 | |
| About • | paper received ※ 23 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB027 | Electromagnetic Design and Characterization of an S-band 3-Cell RF Accelerating Cavity | 2867 |
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| An S-Band (2998 MHz) RF cavity to accelerate electrons was developed taking into account the beam space charge, the relativistic change in velocity of the low energy beam particle distribution through the cavity and the emittance growth. The electromagnetic design and geometry optimization were done using the codes Poisson Superfish and CST Studio. In addition, beam dynamics simulations were done using the program Travel to optimize the emittance and take into account the space charge effect. The machining was done in a CNC machining center. Measurements of the cavity resonance frequencies were carried out and compared with the obtained by the simulations with good agreement between them. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB027 | |
| About • | paper received ※ 30 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB028 | Electromagnetic Design of the Low Beta Cavities for the JAEA ADS | 2870 |
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| The Japan Atomic Energy Agency (JAEA) is designing a superconducting CW proton linear accelerator for the ADS project. The superconducting region will use five types of radio frequency cavities. In the region from 2 to 180 MeV the acceleration will be done using Half Wave Resonator (HWR) and Single Spokes (SS) cavities. HWR cavities will accelerate the beam from 2 to 10 MeV with a geometrical beta of 0.08 and the SS ones will do from 10 to 180 MeV using two cavity families with geometrical betas of 0.16 and 0.43. The results of electromagnetic model design are presented and the comparison with similar cavities from other projects are included. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB028 | |
| About • | paper received ※ 19 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB029 | Design of the Elliptical Superconducting Cavities for the JAEA ADS | 2873 |
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| The superconducting CW proton linear accelerator for an Accelerator Driven Subcritical System (ADS) proposed by Japan Atomic Energy Agency (JAEA) employs elliptical cavities for the final acceleration of 180 MeV to 1.5 GeV. Since this energy region implies a change of beta from 0.55 to 1, two cavity models were developed using the geometrical betas of 0.68 and 0.89 to improve the acceleration efficiency. The study of the electromagnetic design was simulated using SUPERFISH (SF) code and python program to do variable scan, the results were benchmarked with CST Microwave Studio program (CST). | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB029 | |
| About • | paper received ※ 18 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB030 | Commissioning of RF System of the 200 MeV Proton Cyclotron | 2877 |
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Funding: (1) National Natural Science Foundation of China under grant No. 11775258, 11575237; (2) International Sci-entific and Technological Cooperation Project of An-hui (grant No. 1704e1002207). The SC200 superconducting accelerator which is designed for proton therapy is currently under con-struction. The RF (Radio Frequency) system has been designed and constructed as a subsystem of the SC200. To verify the stability of the RF system, a high-power feeding test was performed for the cavity. This paper mainly reports on the overview of RF systems and the prelimary high-power commissioning, as well as the problems found and improvements made during the commissioning process. The results show that the RF system has initially achieved the designed goal, and each loop (amplitude, tuning, phase) can work effec-tively. The cavity can operate in a ~50 kW continuous wave state. Next, the formal RF conditioning will be carried out after the complete assembly of cyclotron, so as to confirm the cavity can run smoothly under 80 kW, which is part of the whole commissioning process. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB030 | |
| About • | paper received ※ 22 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB031 | SRF Trip Caused by the Tuner in BEPCII | 2880 |
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Funding: Work support by Natural Science Foundation of China (11575216) The stability and reliability of the Superconducting RF system (SRF) is generally a key issue in a large scale accelerator such as Beijing Electron Positron Collider II (BEPCII). In the past several years, SRF is one of the main factors limiting the availability of BEPCII, and many efforts have been made to fix the SCRF troubles. This paper focuses on the details of the SCRF trip caused by the tuner, which is one of the most persistent troubles and figured out till the summer of 2018. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB031 | |
| About • | paper received ※ 08 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB032 | Superconducting Elliptical Cavities Developed in IMP for the CiADS | 2883 |
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| Multicell superconducting radio frequency (SRF) ellip-tical cavities are proposed for efficient acceleration of proton beam in the Chinese initiative Accelerator Driven Subcritical System (CiADS). Two families of such cavities will be used in the driver SRF Linac, the first family corresponding to βopt=0.62 cavities that will be used to accelerate the H+ beam from 175 MeV to 377 MeV and the second family corresponding to βopt=0.82 cavities that will accelerate the H+ beam from 377 MeV to 500 MeV, with the possibility to upgrade to 1 GeV and higher. The electromagnetic optimization of the cavities with the HOM, wakefield and multipacting analysis will be dis-cussed in this paper. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB032 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB034 | Study on the Design of the X-band Waveguide-damped Structure | 2886 |
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| The design of waveguide-damped structure is optimized to reduce the magnitudes of surface electromagnetic fields and strongly suppress long-range transverse wakefields of the 380 GeV Compact Linear Collider facility currently under study. The optimization is mainly discussed with the elliptical shape of the iris, the wall shape of the damping waveguides, the position of the high-order-mode damping loads and the widths of the waveguide openings of the entire sequence of damping waveguides. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB034 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB037 | Development of EP System at IHEP | 2890 |
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| Electropolishing (EP) is a necessary technology for high quality cavities including both high accelerating gradient and high quality factor cavities, which will be used for several future large projects such as CEPC, Shanghai hard X-ray FEL, ILC, and so on. An EP system was development at IHEP, CAS. In last years, we finished all the engineering design and fabrication including functional circulation loops design, system parameters choices, key equipment choice or design, components test and fabrication. According to the functions of various components, the whole system were divided into three main units: electrolyte mixing, acid solution and mechanical platform, and several key components such as rotation sleeves, DC power supply and so on. Since the system is designed for both R&D and mass production, several characteristics comparing with those in other labs in the world can be realized, including dozens of solution circulations, electrolyte mixing, new and old acid separation, cavity outside water cooling, cathode vertical assembly, and compatible for several types of cavities. We will report them in this paper. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB037 | |
| About • | paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB039 | Tuning of a Tapered Ridge-Loaded Waveguide Coupler for a Drift Tube LINAC of the Compact Pulsed Hadron Source | 2893 |
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| This paper presents the tuning result of a tapered ridge-loaded waveguide coupler for the drift tube linac (DTL) of the compact pulsed hadron source (CPHS) at Tsinghua University. The coupler has been designed, manufactured, and mounted on the DTL cavity for the cold measurement and tuning. The iris diameter of the coupler which is related to the coupling coefficient needs to be determined in the tuning experiment, due to the difference between the designed and measured quality factors. Meanwhile, we found that the relationship between the coupling coefficient and iris diameter from the traditional analytical design method is not applicable when the iris diameter is relatively large. In this paper, the target coupling coeffi-cient is analysed, and the limit of the original analytical design is presented. The measurement method is intro-duced to improve the measurement efficiency and the tuning process of the coupling coefficient to the target value is described. After several iterations, the coupling coefficient is tuned to 1.54 which is close to the desired value of 1.56. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB039 | |
| About • | paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB042 | High Power Test of the First C-band Spherical Pulse Compressor Prototype | 2896 |
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Funding: National Natural Science Foundation of China (No. 11675249) Recently, a new C-band (5712 MHz) compact spherical radio frequency (RF) pulse compressor was designed and tested for Shanghai Soft X-ray Free Electron Laser Facili-ty (SXFEL). This pulse compressor utilizes one high Q0 spherical RF resonant cavity that works with two TE1, 1,3 modes and a dual-mode polarized coupler. The peak power multiply factor is 6.1 and average power gain 3.8 in theory. During the high power test, a peak power mul-tiply factor of 5.74 and average power gain of 3.77 was achieved. This paper presents the RF measurement of the C-band spherical pulse compressor and the high power test results. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB042 | |
| About • | paper received ※ 19 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB043 | Wakefield Suppression in the Main LINAC of the Klystron-Based First Stage of CLIC at 380 GeV | 2899 |
| SUSPFO064 | use link to see paper's listing under its alternate paper code | |
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| An alternative klystron-based scenario for the first stage of Compact Linear Collider (CLIC) at 380 GeV centre-of-mass energy was proposed. To preserve the beam stability and luminosity of CLIC, the beam-induced transverse long-range wakefield in main linac must be suppressed to an acceptable value. The design of klystron-based accelerating structure is based on waveguide damping structure (WDS). The high-order modes (HOMs) propagating into four waveguides are absorbed by HOM damping loads. In this paper, the wakefield suppression in CLIC-K based on GdfidL code simulations are presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB043 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB044 | Microphonics Simulation and Parameters Design of the SRF Cavities for CiADS | 2903 |
| SUSPFO066 | use link to see paper's listing under its alternate paper code | |
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| The CiADS (China initiative Accelerator Driven System) proton Linac is designed to accelerate CW beams of up to 500 MeV and 5mA, which is delivered to the spallation target. Since the beam power will eventually reach 2.5 MW, the beam loss should be restricted, which is sensitive to the SC cavity stability. On CW operating mode, the main perturbation to the cavity is microphonics. This paper will describe a set of tools developed to simulate performance of the cavity and its LLRF control system in order to ensure proper cavity operation under microphonics. The simulation tools describe a relationship between microphonics and the RF parameters. The microphonics effect to the cavity is simulated. The tolerated intensity of microphonics is determined by simulation, in order to satisfy the stability of amplitude and phase with 0.1% and 0.1 degree respectively. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB044 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB045 | Suppression of Secondary Electron Yield Effect in the 650MHz/800kW Klystron for CEPC | 2906 |
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| The circular electron positron collider (CEPC) is in pre-research, it will need more than two hundred 650MHz/800kW klystrons. The secondary electron yield (SEY) effect suppression is very important for the klystron working stable. The simulation uses an incident primary electron source and considers all the phases and power levels of the input microwave. Two methods are simulated for the SEY suppression. The groove cutting on the nose of cavities is much simple while the TiN coating can suppress better. The effect after groove cutting on nose is also simulated and the corresponding compensations are adopted. For simplify the fabrication progress as well as some experience that can be referenced, the groove cutting method is adopted finally for the first klystron prototype, which is expected to be available in the summer of 2019. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB045 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB046 | Development of Flexible Waveguide for High Power High Vacuum Applications in S-band | 2909 |
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| A novel flexible waveguide is developed for S band 2856 MHz, which is a standard WR284 waveguide. The surface of the flexible waveguide is plated with Oxygen-free High Conductivity (OFHC) copper for the purpose of welding with the stainless steel flange in the vacuum furnace, for the flexible waveguide itself is made of brass. The prototype has got a certain amount of deformation which will be much more convenient for the connection between two hard waveguides. It also has a good measurement results of the lower power microwave test, and the 72 hours vacuum leakage test shows a satisfactory vacuum performance, no obvious surface collapse is observed. The high power test will be conducted after our high power test facility is available, which will tell us the maximal power level of the flexible waveguide prototype. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB046 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB047 | High-Power Test of a 12 Cell Accelerating Structure Build in Halves | 2912 |
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| An X-band 12 cell travelling-wave accelerating structure has been developed and high-power tested at Tsinghua University in China. This structure works at 2⁄3 π at the frequency of 11.424 GHz. It is a 12-cell constant-impedance structure build in halves and was silver-brazed as a vacuum tight structure. The high power test was conducted at Tsinghua X-band high power test facility [1] with a 50-MW X-band klystron at a repetition rate to 40 Hz. The final input power was 51.23 MW with a 200 ns pulse width, which means an accelerating gradient of 88.58 MV/m was reached. This paper presents the high power test results including the gradient and breakdown history. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB047 | |
| About • | paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB048 | Design, Fabricate, and Tuning of X-Band Deflecting Structure for CERN | 2915 |
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| A 20-cell x-band deflecting structure for CERN has been finished, and now is under high power conditioning at XBOX of CERN. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB048 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB049 | HOM Analysis of the 4-cell Superconducting Cavity on CTFEL Facility | 2918 |
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| The higher order modes (HOMs) of the 1.3GHz 4-cell cavity on CTFEL facility is analyzed in this paper. The passbands of the HOMs in the 4-cell cavity were simulat-ed, and the most harmful modes were determined. The power of the wakefields was estimated. By microwave test at room temperature, the frequencies of the HOMs were measured, as well as the external Q’s of the HOM cou-plers. Besides, a frequency distribution measurement system was built. The HOM signal excited by beam at 2 K temperature is measured, and some preliminary results are obtained. The measurement techniques and results of the HOM damping performance are presented in this paper. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB049 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB050 | Multipacting Studies of the Coaxial Coupler for BNCT DTL | 2921 |
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Funding: Youth Innovation Promotion Association of CAS (2015011) Program for GuangDong Introducting Innovative and Enterpreneurial Teams (2017ZT07S225) Multipacting is a phenomenon in which electrons grow sharply under certain conditions in a RF structure. It may lead to the breakdown or even damage to the equipment. Therefore, it is very important to calculate the Multipact-ing range in the RF equipment design. Since the phe-nomenon is too complicated to use the formula to fully predict it, numerical simulation is employed. There are many computer codes (such as Track3P, MultiPac, CST PS, etc.) used to simulate the phenomenon, but most of them are not commercial. In this paper, theories used in coaxial line for predicting multipacting are introduced; the CST PS is chosen to simulate the multipacting of coaxial coupler for BNCT DTL; finally, methods of sup-pressing multipacting are discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB050 | |
| About • | paper received ※ 11 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB051 | MA RF Cavity Design and Simulation for CSNS/RCS Upgrade Project | 2925 |
| SUSPFO075 | use link to see paper's listing under its alternate paper code | |
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| The dual harmonic RF system will be adapted for Chi-na Spallation Neutron Source (CSNS) upgrade project. Limited locations in CSNS/RCS are reserved to install additional three 2nd harmonic cavities. The cavity loaded by magnetic alloy (MA) material would be used. Because of the low Q factor of the MA core, the cavity cooling be-comes a very important issue in cavity design. Air-forced, indirect and direct cooling scheme were studied. The fluid thermodynamic of different cooling structure were simu-lated by ANSYS CFX which considered the anisotropy of thermal conductivity of MA core. The limitation of these cooling schemes were discussed in detail based on the simulation results. Indirect cooling experiment was done to assess the cooling efficiency and verify the simulation result. A high power test cavity cooled by water has been designed to estimate the property of the MA core and cooling effectiveness for CSNS/RCS. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB051 | |
| About • | paper received ※ 08 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB052 | Design of Two Types of X-Band High Power Directional Coupler | 2928 |
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| The directional coupler is one of the most widely used components in many microwave systems, which is used to distribute the power of the input microwave signal according to a desired ratio. Directional coupler may be a three-port component or a four-port component with certain specification such as frequencies, bandwidth and structure. To meet the requirements of stable coupling degree and high directivity, we designed two types of directional coupler working at 11.424 GHz with high power handling capacity. One consists of two parallel rectangular waveguides with four holes drilled along the central line of the narrow-wall for coupling the electromagnetic power from the main-waveguide to the sub-waveguide which is called H-plane directional coupler. Simulations show that the coupling degree of H-face directional coupler is 49.9 dB and the directivity is 54.5 dB .The peak electric field is about 29MV/m while operating at 200 MW peak power. The other consists of a circular main-waveguide transmitting TM01 mode and a rectangular sub-waveguide transmitting TE10 mode, called circular-rectangle waveguide directional coupler. These two waveguide are connected by six holes drilled on the side of the circular main-waveguide and along the central line of the wide-wall of the sub-waveguide. The coupling degree of this directional coupler is 50.14 dB and the directivity is 37.93 dB due to the simulation. The bandwidth is about 800MHz. The peak electric field is 404.5V/m while operating at 200 MW peak power. Comparing with the H-plane directional coupler, peak electric field of this directional coupler is lower. Low peak electric field can reduce the risk of RF breakdown and the Multipactor effect, which ensures the stable high power operation of the directional coupler. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB052 | |
| About • | paper received ※ 27 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB054 | Design of the Multiplexing Optical Measurement System for a Pre-bunched THz Free Electron Laser | 2931 |
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Funding: Work supported by the the Fundamental Research Funds for the Central Universities (WK2310000080, WK2310000057), and the National Science Foundation of China (11705203, 11575181) A new and compact a pre-bunched terahertz (THz) free electron laser (FEL) at the National Synchrotron Radiation Laboratory, University of Science and Technology of China is being constructed and aims to generate the tunable radiation frequency ranges from 0.5 THz to 5 THz at 11-18 Mev electron energy. This system is expected to use for imaging, basic researches as well as industrial applications as a result of the significant merits of simple, compact and cost-effective. Due to the THz laser measurement system plays an important part in the pre-bunched THz FEL facility. Therefore, a multiplexing THz laser sensing measurement system model is developed for measuring the output laser power and the optical spectrum of THz radiation with the excellent advantages of robustness, high sensitivity and low-cost in this paper. Corresponding author (email: tiany86@ustc.edu.cn) Corresponding author (email: wufangfa@ustc.edu.cn) |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB054 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB055 | Design of 3 MeV S-band Electron Linac Structure With 2.5 Bunching Cells | 2934 |
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Funding: UST (University of Science and Technology), KAERI (Korea Atomic Energy Research Institute) The Korea Atomic Energy Research Institute (KAERI) has been designing several 3 MeV S-band RF electron linear accelerators (linacs) for non-destructive testing. Until now, the bunching cell of the linac has a full-cell geometry. However, to maximize the acceleration of electrons after emission from the electron gun, the geometry of the first bunching cell is modified from a full-cell to a half cell. To accelerate electron beams more gently, recently, we increased the total number of bunching cells from 1.5 to 2.5. In this paper, we describe design concepts and detailed optimization processes of a 3 MeV linac with the 2.5 bunching cells to optimize RF parameters such as the quality factor, resonance frequency, and uniformity of electric field distribution along the linac. Lastly, we will discuss the application of 3 MeV linac. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB055 | |
| About • | paper received ※ 04 June 2019 paper accepted ※ 16 June 2019 issue date ※ 21 June 2019 | |
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| WEPRB056 | Design Study of 325MHz RF Power Coupler for Superconducting Cavity | 2937 |
| SUSPFO088 | use link to see paper's listing under its alternate paper code | |
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| We present the design study of the RF input power coupler for 325 MHz superconducting cavities. The power coupler, based on a conventional coaxial transmission line, provides RF powers to the cavity up to 12kW in CW mode. The thermal interceptors are considered as 4.5 K and 40 K or 4.5 K and 77 K corresponding to the usage of liquid Helium only or both liquid Helium and Nitrogen for cryogenic temperature to reduce the thermal load. The transition box (T-box), which is assembled with power coupler, is designed and applied for impedance matching and inner conductor cooling. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB056 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB058 | Combined Field Emission and Multipactor Simulation in High Gradient RF Accelerating Structures | 2940 |
| SUSPFO091 | use link to see paper's listing under its alternate paper code | |
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| Field emitted electrons have important consequences in the operation of high-gradient RF accelerating structures both by generating so-called dark currents and initiating RF breakdown. The latter is an important limitation of the performance in such devices. Another kind of vacuum discharge that primarily affects the operation of lower-field RF components, for example those used in space applications, is multipactor. Theoretical simulations using CST Particle Studio, show that field emitted electrons generated in the high field regions of high-gradient accelerating cavities migrate to low field regions under ponderomotive forces potentially triggering multipactor there. This phenomenon is an interplay between high field and low field processes which may have as a consequence that multipactor actually affects to the performance of high-gradient cavities because field emitted electrons might reduce the timescales for the onset of multipactor. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB058 | |
| About • | paper received ※ 27 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB059 | Dark Current Analysis at CERN’s X-band Facility | 2944 |
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| Dark current is particularly relevant during operation in high-gradient linear accelerators. Resulting from the capture of field emitted electrons, dark current produces additional radiation that needs to be accounted for in experiments. In this paper, an analysis of dark current is presented for four accelerating structures that were tested and conditioned in CERN’s X-band test facility for CLIC. The dependence on power, and therefore on accelerating gradient, of the dark current signals is presented. The Fowler-Nordheim equation for field emission seems to be in accordance with the experimental data. Moreover, the analysis shows that the current intensity decreases as a function of time due to conditioning, but discrete jumps in the dark current signals are present, probably caused by breakdown events that change the emitters’ location and intensity. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB059 | |
| About • | paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB060 | HOM Damped Normal Conducting 1.5 GHz Cavity Design Evolution for the 3rd Harmonic System of the ALBA Storage Ring | 2948 |
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| In a collaboration framework with CERN, ALBA has designed a normal conducting active 1.5 GHz cavity which could serve as main RF system for the Damping Ring of CLIC and as an active third harmonic cavity for the ALBA Storage Ring. 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. The main advantage of an active third harmonic cavity is that optimum conditions can be reached for any beam current. This paper presents the evolution of the preliminary design of this cavity and its trans-dampers: high order modes coaxial dampers with waveguide transitions to N, which allows extracting the power of the high order modes induced by the beam outside of the cavity and to dissipate it using standard loads. This approach has two main advantages: no ferrites brazing is needed and they provide a diagnostic to analyze the beam dynamics. The new features of the design, together with electromagnetic simulations, mechanical and thermal stress analysis will be presented in this paper as well as the first stages of the prototype production status. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB060 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB061 | The Integration and RF Conditioning of the ESS Double-Spoke Prototype Cryomodule at FREIA | 2952 |
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| ESS, the European Spallation Source, will adopt a single family of double-spoke cavities for accelerating the proton beam from the normal conducting section to the first family of the elliptical superconducting cavities. They will be the first double-spoke cavities in the world to be commissioned for a high power proton accelerator. The first double-spoke cavity cryomodule for the ESS project is under high power test at Uppsala University. This paper presents the integration, RF conditioning and experience of this prototype cryomodule. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB061 | |
| About • | paper received ※ 26 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB062 | Spatially Resolved Dark Current in High Gradient Traveling Wave Structures | 2956 |
| SUSPFO106 | use link to see paper's listing under its alternate paper code | |
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| High-gradient accelerating structures are known to produce field-emitted current from regions of high surface field, which are captured and accelerated by the fields within the structure. This current is routinely measured in structures under test in the CLIC high-gradient test stands using Faraday cups. This paper presents a novel technique to spatially resolve the longitudinal distribution of field emitted current by analysing downstream Faraday cup signals when the structure is fed with RF pulses much shorter than its filling time. Results from this method applied to X-band cavities operating at 100 MV/m are presented, and are compared to breakdown position distributions. A decay in emitted current as conditioning progressed in regions with a low breakdown rate and large jumps in regions with a large breakdown rate are observed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB062 | |
| About • | paper received ※ 29 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB063 | Connection of 12 GHz High Power RF from the XBOX 1 High Gradient Test Stand to the CLEAR Electron LINAC | 2960 |
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| A new RF system is being established at XBOX1 to drive two §I{100}{MV/m} CLIC structures in the CLEAR electron linac. In the past, these structures had been powered by RF from PET structures excited by a drive beam. This drive beam is no longer available. The upgrade will reroute power from the §I{50}{MW} klystron and pulse compressor which was previously used to power the structure in XBOX1. During the upgrade, the LLRF system will be optimised to improve the modulation of the output signals and down-mixing of the returning signals to obtain accurate phase and amplitude information. The design of the improved LLRF and software, along with phase noise measurements and comparisons with the old system are made in this paper. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB063 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB064 | High Power Conditioning of X-Band Variable Power Splitter and Phase Shifter | 2964 |
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| The three X-band test facilities currently at CERN aim at qualifying CLIC structures prototypes but are also exten- sively used to qualify X-band components operation at high power. In order to upgrade one of the facilities from a single test line to a double test line facility, a high power variable splitter and variable phase shifter have been designed and manufactured at CERN. They have been power tested, first in a dedicated test and also in their final configuration, to en- sure stable power operation before installing them together with an accelerating structure. In this paper, we broadly describe the RF and mechanical design, manufacturing and low power measurements agreement with simulations. We report the high power qualification of both components and their suitability to be used in existing and planned X-band facilities. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB064 | |
| About • | paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB065 | Multi-physics Computation and Deformation Testing of a Shell-type 1.5-GHz Cavity | 2968 |
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Funding: Work supported by the Ministry of Science and Technology, R. O. C. (Taiwan) under grant NSC-100-2628-E-213-001-MY3. A copper prototype of a 1.5-GHz cavity was manufac-tured to simulate a superconducting radio-frequency cavity for technique development. Frequency tuning with longitudinal compression of this prototype and cryogenic cooling with liquid nitrogen were performed to examine the numerical results from finite-element models, mainly the corresponding shifts of the fundamental resonant frequency. An appropriate element option improved the accuracy of the resonant frequency and the distribution of the magnetic field. Effects of geometry distortion of an uneven length on the frequency shift of this shell-type cavity as loaded on longitudinal compression are also examined and discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB065 | |
| About • | paper received ※ 25 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB066 | Utilizing the High Shunt Impedance TM020-Mode Cavity in the Double RF Systems for the Storage Ring of the Thailand New Light Source | 2972 |
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| The utilization of the TM020-mode cavity for the storage ring based light source was pioneered by SPring-8 with its high quality factor and hence its high shunt impedance. KEK-LS has also studied the possibility of using this type of cavity for their storage ring. The TM020-mode cavity has larger transverse dimension compared to the traditional TM010-mode cavity, but with its higher shunt impedance it can be designed to fit in the new low emittance storage ring regardless. The new storage ring based light source project in Thailand aims to optimum the low emittance beam in nano-meters region with the energy of 3 GeV. The TM020-mode cavity was considered as the main cavity and the harmonic cavity for the storage ring. They have been designed to have their pipe aperture fits the storage ring beam ducts. The main cavity has a high shunt impedance of 8.3 Mega Ohms with the 51,000 unloaded quality factor. The harmonic cavity has a high shunt impedance and an unloaded quality factor of 2.45 Mega Ohms and 36,000, respectively. The damping mechanism of the parasitic modes and the tuning mechanism of the operating mode of these cavities were also studied. There will be four main cavities and six harmonic cavities in the new storage ring. Detailed design and study of these cavities will be presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB066 | |
| About • | paper received ※ 29 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB068 | Ka-Band Linearizer Studies for a Compact Light Source | 2976 |
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Funding: This project has received funding from the European Union’s Horizon2020 research and innovation programme under grant agreement No 777431. The CompactLight project is currently developing the design of a next generation hard X-ray FEL facility, based on high-gradient X-band (12 GHz) structures, bright electron photo-injectors, and compact short period undulators. However, to improve the brightness limitations due to the non-linear energy spread of the electron bunches, a K-band (36 GHz) linearizer is being considered to provide a harmonic compensation during the bunch compression. In this paper, we analyze the feasibility of such linearizer. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB068 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB069 | Wakefield Suppression in a Manifold Damped and Detuned Structure for a 380 GeV CLIC Staged Design | 2980 |
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| The first stage of the Compact Linear Collider (CLIC) project aims to collide electrons and positrons at a 380 GeV center of mass energy. In the baseline design the main linacs for this staged approach are required to achieve a gradient of 72 MeV/m, with the surface electromagnetic fields (EM) and the transverse long-range wakefields bound by beam dynamics constraints. The baseline design utilizes heavy damping in a traveling wave (TW) structure. Here we report on an alternate design, which adopts moderate damping along with strong detuning of the individual cell frequencies. In the context of this Damped and Detuned Structure (DDS) design, we study Gaussian and hyperbolic secant dipole distributions, together with interleaving of successive structures, to effect long-range transverse wakefield suppression. Both analytic and modal summation approaches, in the quasi-coupled approximation, produce consistent results. In the optimisation scheme we opt for a dipole frequency bandwidth of 17.7 % (2.92 GHz) | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB069 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB070 | Facile Deposition of Superconducting MgB2 Thin Films on Substrates: A Comparative Investigation of Electrochemical Deposition and Magnetron Sputtering Techniques | 2984 |
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Funding: Authors acknowledge the funding received under the Rutherford International Postdoctoral Fellowship Programme Coating of Copper cavities with a superconducting layer of MgB2 thin film is an attractive alternative to bulk Nb cavities. In this work, we investigate the application of two approaches-electrochemical deposition and magnetron sputtering of MgB2, to fabricate MgB2 films with potential accelerator applications. In the first approach, MgB2 powder dispersed in acetone was used as an electrolytic medium. Application of a DC voltage of 400 V between a graphite anode and a Copper film (serving as cathode), with the electrode distance maintained at ~2cm, resulted in the electrochemical deposition of MgB2 on the Cu surface. In an alternate approach, MgB2 in powder form was used directly for sputtering based deposition. The powder was initially compacted to form a thin layer that served as the magnetron target. Application of a pulsed DC power of 25W for 4 hours yielded MgB2 thin film on Si substrates. Samples were characterized by XPS analysis to ascertain their elemental composition, which confirmed the presence of Mg and B, in addition to traces of C and O as impurities. Surface morphology was determined using SEM characterization technique. Further work to determine the superconducting properties of the samples and fine tune the deposition processes for large scale MgB2 deposition inside actual RF cavities is in progress. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB070 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB072 | Ultra-High Gradient Short RF Pulse Gun | 2987 |
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Funding: DOE SBIR DE-SC0018709 High brightness beams enable novel applications like x-ray free electron lasers and ultrafast electron microscopes. High brightness beams essentially consist of a large number of electrons in a small phase space volume, i.e. a high peak current. When such beams are generated from the cathode, there is a strong space charge force, which elongates the bunch and reduces its brightness. An optimal solution is to raise the accelerating voltage in the gun. However, the maximum gradient is limited by the effects of RF breakdown. The probability of RF breakdown is reduced as the RF pulse length decreases. We present a development of an electron photoinjector operating with short RF pulse, 10 ns scale. We have designed an X-band gun including the RF design, beam quality optimization, and engineering. The gun will be fed by 10 ns, 300 MW RF pulse generated at the Argonne Wakefield Accelerator Facility for two-beam acceleration experiments. We also manufactured an aluminum prototype and measured its microwave properties, most importantly, fill time. The proposed high brightness beam source can be used as the main beam in wakefield accelerators. It will find commercial applications in ultrafast electron diffraction and microscopy systems. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB072 | |
| About • | paper received ※ 21 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB073 | CW Room Temperature Accelerating Structures | 2990 |
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| To this day CW linear electron accelerators were based only on expensive and bulky (embedded in a cryostat) superconducting accelerating structures. CW regime can in principle be realized with normal conducting structures provided the shunt impedance is high. Such structures can be designed using dielectrics (ultra-pure ceramics in C-band and diamond in mm-waves) with ultra-low loss tangent (~10-6). The use of dielectrics allows to concentrate the electromagnetic energy density in the dielectric region and thus minimize fields and ohmic loss on metallic walls. The thermal loss in dielectric can be relatively low given the loss tangent is small. We report here the design of structures with shunt impedance on the order of 104 MOhm/m, which is several orders of magnitude higher than shut impedance in copper structures in GHz and THz range. High shunt impedance makes it possible to accelerate electrons to 1 MeV using kW-level CW RF sources like magnetrons in C-band and gyrotrons in THz range. Such CW accelerators will find applications in sterilization, food irradiation, industrial radiography and cargo inspection. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB073 | |
| About • | paper received ※ 21 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB075 | Optimizing Room Temperature RF Structures for Accelerator Driven System Operations | 2993 |
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Funding: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. Minimizing beam trip rates is one of the key operational goals at the Spallation Neutron Source (SNS). Trip rates are closely monitored, and real-time statistics are kept during beam operations for immediate analysis. Beam trips are automatically binned by the length of the trip along with the cause for each trip. The shortest beam trips occur with the highest frequency and those trip rates are dominated by the room temperature RF structures. There can be many causes for the RF structure malfunctions, but one area that has had a major impact on trip rates is improvement in how RF processing is done on structures after extended maintenance periods. Details about the improvement in RF conditioning will be discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB075 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB076 | Analysis of Higher Order Multipoles of the 952.6 Mhz RF-Dipole Crabbing Cavity for the Jefferson Lab Electron-Ion Collider | 2996 |
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| The crabbing system is a key feature in the Jefferson Lab Electron-Ion Collider (JLEIC) required to increase the luminosity of the colliding bunches. A local crabbing system will be installed with superconducting rf-dipole crabbing cavities operating at 952.6 MHz. The field non-uniformity across the beam aperture in the crabbing cavities produces higher order multipole components, similar to that which are present in magnets. Knowledge of higher order mode multipole field effects is important for accurate beam dynamics study for the crabbing system. In this paper, we quantify the multipole components and analyse their effects on the beam dynamics. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB076 | |
| About • | paper received ※ 20 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB077 | Simulation and Measurements of HOM Filter of the LARP Prototype RF-Dipole Crabbing Cavity Using an RF Test Box | 2999 |
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| The RF-Dipole Crabbing Cavity designed for the LHC High Luminosity Upgrade includes two higher order mode (HOM) couplers. One of the HOM couplers is an rf filter, which is a high pass filter designed to couple to the horizontal dipole modes and accelerating modes up to 2 GHz, while rejecting the fundamental operating mode at 400 MHz. The coupler consists of a high pass filter circuit where the rejection of the operating mode and transmission of HOMs are sensitive to dimensional deviations. An rf test box has been designed to measure the transmission of the rf filter in order to qualify the fabricated HOM coupler and to tune the coupler. This paper presents the measurements of the HOM coupler with the rf test box. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB077 | |
| About • | paper received ※ 20 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB078 | RF Commissioning and Performance in the CBETA ERL | 3003 |
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Funding: This work was supported by the New York State Energy Research and Development Authority, Contract No. DE-SC0012704 with the U.S. Department of Energy and NSF award DMR-0807731. The Cornell-BNL ERL Test Accelerator (CBETA) is a new multi-turn energy recovery linac currently being commissioned at Cornell University. It uses a superconducting main linac to accelerate electrons by 36 MeV and recover their energy. The energy recovery process is sensitive to fluctuations in the accelerating field of all cavities. In this paper, we outline our semi-automated RF commissioning procedure, which starts from automatic coarse tuning of the cavity all the way to adjusting the field control loops. We show some results of using these tools and describe the recent performance of the RF system during our ongoing commissioning phase. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB078 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB080 | Optimization of RF Cavities Using MOGA for ALS-U | 3007 |
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Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 A multi-objective genetic algorithm-based optimiza-tion process has been applied to optimize the RF design of a 500 MHz main cavity and a 1.5 GHz Higher Harmon-ic Cavity (HHC) for the Advanced Light Source upgrade (ALS-U) in Lawrence Berkeley National Laboratory (LBNL). For the main cavity, a significant improvement, compared with the existing ALS cavity, has been achieved in cavity shunt impedance and power loss den-sity simultaneously. The field strengths and distribution of the optimized structure are analysed for further re-search. For the HHC, a cavity with low R/Q has been pre-liminary designed to mitigate the beam instability. This study also serves as an example of how a genetic algo-rithm can be used for optimizing RF cavities. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB080 | |
| About • | paper received ※ 16 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB081 | Design Study on Higher Harmonic Cavity for ALS-U | 3011 |
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Funding: Director of Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 The ALS upgrade (ALS-U) to a diffraction-limited light source [1] depends on the ability to lengthen the stored bunches to limit the emittance growth and increase the beam life time. Higher harmonic cavities (HHCs), also known as Landau cavities, have been proposed to in-crease beam lifetime and Landau damping by lengthen-ing the bunch. We present an optimized 1.5 GHz normal conducting HHC design for the ALS-U with a supercon-ducting-like geometry using multi-objective genetic algorithm (MOGA) for lower R/Q. The optimization goal is to reach the required shunt impedance while maintain-ing a relatively high Q value of the cavities. To minimize the coupled bunch instabilities, higher-order mode (HOM) of the HHC as well as corresponding impedance are explored and characterized. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB081 | |
| About • | paper received ※ 16 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB084 | Mechanical Design and Analysis of the Proposed APEX2 VHF CW Electron Gun | 3014 |
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Funding: Work supported by the Office of Science, U.S. Department of Energy under DOE contract number DEAC02-05CH11231 Normal conducting radio-frequency (RF) guns resonating in the very high frequency (VHF) range (30-300 MHz) and operating in continuous wave (CW) mode have successfully achieved the targeted brightness and reliability necessary for upgrading the performance of current lower repetition rate accelerator-based instruments such as X-ray free electron lasers (FELs), and ultra-fast electron diffraction (UED) and microscopy (UEM). The APEX2 (Advanced Photo-injector Experiment 2) electron gun is a proposed upgrade for the current LCLS-II injector, which was based on the original APEX design. In contrast, APEX2 is designed as a two-cell cavity operating at 162.5 MHz with a launching field at the cathode equal to 34 MV/m, producing a beam energy of 1.5 to 2 MeV, more than double APEX. Operation of the gun in this condition will require upwards of 200 kW of RF power, thus proper thermal management is crucial to achieve target performance. This paper describes the current design, thermal performance and tuning methods. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB084 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB087 | High-gradient SRF Cavity R&D at Cornell University | 3017 |
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| Achieving high accelerating field is a critical R&D topic for superconducting RF cavities for future accelerators including the International Linear collider (ILC). The ILC requires an average accelerating field of 35MV/m with a Q0 of at least 8.9·109 at 2K. In this paper, we report the latest results from high-gradient research at Cornell, which focusses on 75C vacuum baking to improve maximum (quench) fields. We demonstrate that such low temperature bakes can significantly improve quench fields in certain cases by mitigating localized defects. We further report on high-pulsed power results of these cavities before and after baking. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB087 | |
| About • | paper received ※ 23 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB089 | Theoretical Analysis of Quasiparticle Overheating, Positive Q-Slope, and Vortex Losses in SRF Cavities | 3020 |
| SUSPFO131 | use link to see paper's listing under its alternate paper code | |
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| The surface resistance of an SRF cavity is an important measure of its performance and utility: lower resistance leads directly to lower cryogenic losses and power consumption. This surface resistance comprises two components, namely the ‘‘BCS resistance’’, which depends strongly on the quasiparticle temperature, and a temperature-independent ‘‘residual resistance’’, which is often dominated by losses due to trapped magnetic vortices. Both components are generally dependent on the RF field strength. Here we present a summary of recent theoretical advances in understanding the microscopic mechanisms of the surface resistance, in particular addressing niobium hydride formation and quasiparticle overheating (using the tools of density functional theory) and discussing issues with existing models of the positive Q-slope, a field-dependent decrease in the BCS resistance, and possible paths for improvement of these models. We also discuss trapped flux losses using ideas from collective weak pinning theory. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB089 | |
| About • | paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB090 | The Design of Parallel-Feed SC RF Accelerator Structure | 3024 |
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Funding: Research funded by a SLAC Laboratory-Directed Research and Development award, supported by the U.S. Department of Energy, contract number DE-AC02-76SF00515 Development of superconducting RF (SRF) accelerator technology that enables both higher gradient and higher efficiency is crucial for future machines. While much of the recent R&D focus has been on materials and surface science, our aim is to optimize the cavity geometry to maximize performance with current materials. The recent demonstration of a highly efficient parallel-feed normal-conducting RF structure at SLAC has served as a proof-of-concept. Instead of coupled elliptical cells, the structure employs isolated re-entrant cells. To feed RF power to the cavities, each cell is directly coupled to an integrated manifold. The structure is made in two parts, split along the beam axis, which are then joined. Applied to SRF, simulations suggest such a structure could nearly double the achievable gradient, while reducing cryogenic RF loss by more than half. We are experimentally verifying the concept using an X-band SRF design to be tested at SLAC. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB090 | |
| About • | paper received ※ 24 May 2019 paper accepted ※ 27 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB093 | Design of a Proof-of-principle Crabbing Cavity for the Jefferson Lab Electron-ion Collider | 3027 |
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| The Jefferson Lab design for an electron-ion collider (JLEIC) requires crabbing of the electron and ion beams in order to achieve the design luminosity. A number of options for the crabbing cavities have been explored, and the one which has been selected for the proof-of-principle is a 952 MHz, 2-cell rf-dipole (RFD) cavity. This paper summarizes the electromagnetic design of the cavity and its HOM characteristics. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB093 | |
| About • | paper received ※ 22 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB094 | Measurements of the Electrical Axes of the CeC PoP RF Cavities | 3031 |
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| It is common knowledge that every mode in an SRF cavity has a so-called electrical axis, and only in an ideal cavity would this axis align exactly with the geometrical axis of the device. The misalignment of the electrical axis creates an additional undesirable transverse kick to the beam, which has to be corrected to achieve the designed beam parameters. In this paper we present the two methods which have been used in order to determine the electrical axes in the RF cavities of the Coherent electron Cooling (CeC) Proof of Principle (PoP) accelerator. The electron accelerator for the CeC PoP consists of the three main RF components: the 113 MHz SRF gun, the two normal-conducting 500 MHz bunching cavities, and the 704 MHz SRF 5-cell elliptical cavity. We discuss, in detail, the specifics of the measurement for each cavity and provide the corresponding results. In addition, we describe the influence of the field asymmetry in the 500 MHz bunchers on the beam dynamics, which was observed experimentally and confirmed by simulations. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB094 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB095 | Microbunching Plasma-Cascade Instability | 3035 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and NSF Grant No. PHY-141525 We present a new type of longitudinal microbunching instability entitled ’Plasma-Cascade Instability’. This instability could occur in beams propagating along a straight section with external focusing elements. We present a theoretical description of this instability as well as self-consistent 3D simulations. Finally, we present results of experimental observation of Plasma-Cascade Instability at frequencies up to 10 THz using SRF linear accelerator built for Coherent electron Cooling experiment *. * Commissioning of FEL-based Coherent electron Cooling system, V.N. Litvinenko et al., In proc. of 38th Int. Free Electron Laser Conf.(FEL’17), Santa Fe, NM, USA, August 20-25, 2017, p. 132 |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB095 | |
| About • | paper received ※ 18 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB097 | Understanding and Mitigation of Field Emission in CEBAF SRF Linacs | 3039 |
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Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. We will present current understanding of field emission in two 1.1 GeV CW SRF linacs at CEBAF and its mitigation for improved CEBAF energy reach and operation reliability. This contribution will provide a review of CEBAF gradient evolution since 2014, the impact of field emission, the effort in understanding the root cause of field emission in operational SRF cavities including the recently installed C100 cavities. We will evaluate the effect of initial mitigations implemented since 2016, aimed at reducing generation and transportation of new field emitting particulates. Effects of cavity thermal cycling aimed at abating activation of settled field emitting particulates will be evaluated as well. Remaining issues toward predictable control of field emission in operational SRF cavities will be discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB097 | |
| About • | paper received ※ 19 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB098 | Cryogenic RF Performance of Double-Quarter Wave Cavities Equipped with HOM Filters | 3043 |
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Funding: Work supported by US DOE through BSA LLC under contracts No. DE-AC02-98CH10886, No. DE-SC0012704, and the US LHC Accelerator Research Program (LARP) and by the EU HL-LHC Project. Crab cavities are one of the several components included in the luminosity upgrade of the Large Hadron Collider (HL-LHC). The cavities have to provide a nominal deflecting kick of 3.4 MV per cavity while the cryogenic load per cavity stays below 5 W. Cold RF tests confirmed the required performances in bare cavities, with several cavities exceeding the required voltage by more than 50%. However, the first tests of a Double-Quarter Wave (DQW) cavity with one out of three HOM filters did not reach the required voltage. The present paper describes the studies and tests conducted on a DQW cavity with HOM filter to understand the limiting factor. The recipe to meet the performance specification and exceed the voltage requirement by more than 35% is discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB098 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB099 | Status Update of a Harmonic Kicker Development for JLEIC | 3047 |
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Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. An effort to develop the second prototype of the harmonic kicker for the Circulator Cooler Ring (CCR) of the Jefferson Lab Electron-Ion Collider (JLEIC) is under way. After beam dynamics studies and completion of a conceptual RF design of the kicker [1], further progress has been made toward the final mechanical design including the input power coupler (loop) design, tuner ports, multipacting studies. Furthermore, concerning the kicker’s compatibility with beam dynamics, the impact of RF multipole components was investigated and a scheme was developed to cancel out detrimental beam effects. 1. G. Park, et al, The Development of a New Fast Harmonic Kicker for the JLEIC Circulator Cooler Ring, TUPAL068, proceedings of IPAC 2018. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB099 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB102 | Correction of Crosstalk Effect in the LEReC Booster Cavity | 3051 |
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Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. The Linac of Low Energy RHIC electron Cooler (LEReC) is designed to deliver a 1.6 MeV to 2.6 MeV electron beam, with peak-to-peak dp/p less than 7·10-4. The booster cavity is the major accelerating component in LEReC, which is a 0.4 cell cavity operating at 2 K, with a maximum energy gain of 2.2 MeV. It is modified from the Energy Recovery Linac (ERL) photocathode gun, with fundamental power coupler (FPC), pickup coupler (PU) and higher order mode (HOM) coupler close to each other. The direct coupling between FPC and PU induced crosstalk effect in this cavity. This effect is simulated and measured, and is further corrected using low level RF (LLRF) to meet the energy spread requirement. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB102 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB105 | Design of an X-Band Constant Impedance LINAC for Compact Light Project | 3055 |
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| Within the framework of Horizon 2020 project, Compact Light, in order to provide a high performance, high-gradient X-band technology, for the new generation of hard X-ray FEL, a travelling wave (TW) Linac, working on 2pi/3 mode at 11.9952 GHz, fed by two types of asymmetrically couplers, has been designed. The design was performed using CST Microwave Studio frequency domain solver. First, simulations have been conduct in order to obtain the best trade-off between single cell’s parameters, varying iris aperture. Then, the both couplers, with and without pumping port, has been tuned to avoid reflections at the input port. Finally, the entire structure, with 5 cells, was simulated. The main structure parameters will be present and we will also show and discuss the acceleranting gradient obtained vary with linac lenght and input power. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB105 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB106 | Simulation of the Transition Radiation Transport Through an Optic System | 3059 |
| SUSPFO036 | use link to see paper's listing under its alternate paper code | |
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| Optical Transition Radiation (OTR) screens are widely used for beam profile measurements. The radiation is emitted when a charged particle beam crosses the boundary between two media with different optical properties. The main advantages of OTR are the instantaneous emission process allowing fast single shot measurements (i.e. bunch by bunch measurements in a multi bunch machine), and the good linearity with the beam charge (if coherent effects can be neglected). Furthermore, OTR angular distribution strongly depends on beam energy. Since OTR screens are typically placed in several positions along the Linac to monitor beam envelope, one may perform a distributed energy measurement along the machine: this will be useful, for instance, during the commissioning phase of a machine. This paper deals with the studies of an algorithm to optimize the generation and the transport of the transition radiation through an optic system using the simulation tool Zemax. The algorithm, in combination with a particle tracking code (i.e. Elegant), will allow to simulate the radiation generated by a beam and, so, to take into account beam divergence and energy spread or chromatic effects in the optic system. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB106 | |
| About • | paper received ※ 08 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB107 | The New 1-18 MHz Wideband RF System for the CERN PS Booster | 3063 |
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| The LHC Injector Upgrade (LIU) project at CERN prepares the injectors to meet the requirements of the High Luminosity LHC. For protons, it includes the new Linac4, PS Booster (PSB), PS and SPS. Among the major changes concerning the PSB, the extraction energy increase from 1.4 GeV to 2 GeV and the higher beam intensity, made possible by the Linac4 together with the new charge exchange injection system into the PSB (2·1013 protons) strongly affect the RF system requirements. To deal with this more demanding beam operation, a new RF system was designed. It is based on modern magnetic alloy loaded cavities driven by solid-state amplifiers. Its wideband frequency response (1 MHz to 18 MHz) covers all the required frequency schemes. This new RF system has been produced in 2017 and 2018; installation is planned during 2019, the first year of Long Shutdown 2 (LS2) and commissioning foreseen in 2020. Most of the production and testing was outsourced to industry; parts acceptance, cavities assembly and pre-testing was done in-house. A quality assurance plan was established to achieve the required high reliability. This paper describes the procurement, production and testing strategies and methodologies. It also reports the achieved results, system performances and relevant statistics. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB107 | |
| About • | paper received ※ 26 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB110 | Recent Results from Nb3Sn-Coated Single-cell Cavities Combined with Sample Studies at Jefferson Lab | 3066 |
| SUSPFO133 | use link to see paper's listing under its alternate paper code | |
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Funding: Partially authored by Jefferson Science Associates under contract no. DEAC0506OR23177. Supported by Office of High Energy Physics under grants DE-SC-0014475 and DE-SC-0018918. The critical temperature (~ 18 K) and superheating field (~ 425 mT) of Nb3Sn are almost twice that of niobium, thereby promising the higher quality factor and accelerating gradient at any given temperature compared to traditional SRF cavities made of niobium. It can enable higher temperature for cavity operation (4 K Vs. 2 K), resulting in significant reduction in both capital and operating cost for the cryoplant. Several single-cell cavities along with witness samples were coated with Nb3Sn to explore, understand and improve the coating process for betterment of cavity performance. RF measurements of coated cavities combined with material characterization of witness samples were employed to update the coating process. Following some modifications to the existing coating process, we were able to produce Nb3Sn cavity with quality factor ≥ 2.1010 for accelerating gradient up to 15 MV/m at 4 K, without any significant Q-slope. In this article, we will discuss recent results from several Nb3Sn coated single-cell cavities combined with material studies of witness samples. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB110 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB111 | Development of Nb3Sn Multicell Cavity Coatings | 3070 |
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Funding: Co-Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics. Nb3Sn films have the potential to augment niobium in SRF cavities. Besides single-cell cavity efforts to improve Nb3Sn films, we are working to replicate single-cell results onto the practical 5-cell CEBAF cavities. High quality factors (1011 at 2.0K and 10zEhNZeHn at 4.3 K) have been measured, but the cavities are typically limited by strong low-field Q-slopes and early quenches. Two of the cavities were selected to be assembled into a ’mock-up’ cavity pair unit, the standard step before installation into a cryomodule. Comparison of test results between VTA and pair test offered the first glimpse into post-processing effects on the cavity performance. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB111 | |
| About • | paper received ※ 16 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB113 | Toolbox for Optimization of RF Efficiency for Linacs | 3074 |
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| We present a toolbox for optimizing the rf efficiency for linacs and as an example we use it to re-optimize the Compact Linear Collider booster linac. We have implemented a numerical model of a SLED-type pulse compressor that can generate a single or a double pulse. Together with the CERN CLICopti library, an RF structure parameter estimator, we created the toolbox which enables thorough optimizations of linacs in terms of RF efficiency, beam stability, and cost simultaneously, via a simple and concise Octave script. This toolbox was created for the optimization of X-band-based linacs, however it can also be used at lower frequencies, e.g. in the S- and in the C- bands of frequencies. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB113 | |
| About • | paper received ※ 06 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB114 | Understanding and Pushing the Limits of Nitrogen Doping | 3078 |
| SUSPFO030 | use link to see paper's listing under its alternate paper code | |
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| This work will describe Fermilab experiments that focus on the optimization of doping parameters to achieve low sensitivity to trapped magnetic flux while maintaining very high Q characteristic of nitrogen doped cavities and same or higher quench fields. Working partially in the context of LCLS-2 higher energy upgrade, new doping recipes are pursued and have been found to vary the mean free path of the resonator which is related to the sensitivity to trapped magnetic flux. Moreover, a correlation has been found between lighter doping and higher quench fields while maintaining sufficiently low surface resistance. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB114 | |
| About • | paper received ※ 18 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB115 | Development of RF Interlock and Diagnostics Systems in SOLARIS Storage Ring | 3082 |
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| The purpose of this document is to describe and asses the operation of various devices that have been developed, constructed and tested by RF team in NSRC SOLARIS . One of those devices is used as additional safety interlock for the tuning mechanism of main 100MHz active cavities. The other is a stripline feeding network, that in cooperation with BPM receiving network will excite the beam providing the diagnostics group with a new option for tune measurement. Each device shall have its principle of operation explained and construction details revealed. Finally, all devices will be assesed over their operational lifetime in our facility. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB115 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPRB116 | X-ray Pinhole Camera for Emittance Measurements in Solaris Storage Ring | 3084 |
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| X-ray pinhole camera is widely used system for the transverse beam profile measurement and emittance feedback. However this method is predominantly applied to the middle and high energy storage rings. At Solaris storage ring with the nominal energy of 1.5 GeV, the design of the beamline was modified to provide sufficient X-ray photon flux for proper imaging. The successful installation and commissioning of the X-ray pinhole beamline allows now to measure the emittance and helps in proper 3rd harmonic cavities tuning against the coupled bunch mode instabilities. The paper describes the design details, simulations and measurement results obtained during the beamline operation. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB116 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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