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| MOPMW030 | High Powered Tests of Dielectric Loaded High Pressure RF Cavities for Use in Muon Cooling Channels | cavity, radio-frequency, plasma, experiment | 460 |
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Funding: This work is supported by the Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359. Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. Alumina of purities ranging from 96 to 99.8% was tested in a high pressure RF test cell at the MuCool Test Area at Fermilab. The results of breakdown studies with pure nitrogen gas, and oxygen-doped nitrogen gas indicate the peak surface electric field on the alumina ranges between 10 and 15 MV/m. How these results affect the design of a prototype cooling channel cavity will be discussed. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW030 | ||
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| MOPMW031 | Beam Test of a Dielectric Loaded High Pressure RF Cavity for Use in Muon Cooling Channels | cavity, ion, electron, plasma | 463 |
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Funding: This work is supported by the Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359. Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. A 99.5% alumina ring was inserted in a high pressure RF test cell and subjected to an intense proton beam at the MuCool Test Area at Fermilab. The results of the performance of this dielectric loaded high pressure RF cavity will be presented. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW031 | ||
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| MOPMW043 | Overview of High Power Vacuum Dry RF Load Designs | vacuum, linac, klystron, interface | 504 |
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Funding: Work supported by US Department of Energy under contract DE-AC02-76SF00515 A specific feature of RF linacs based on the pulsed traveling wave (TW) mode of operation is that only a portion of the RF energy is used for the beam acceleration. The residual RF energy has to be terminated into an RF load. Higher accelerating gradients require higher RF sources and RF loads, which can stably terminate the residual RF power. This overview will outline vacuumed RF loads only. A common method to terminate multi-MW RF power is to use circulated water (or other liquid) as an absorbing medium. A solid dielectric interface (a high quality ceramic) is required to separate vacuum and liquid RF absorber mediums. Using such RF load approaches in TW linacs is troubling because there is a fragile ceramic window barrier and a failure could become catastrophic for linac vacuum and RF systems. Traditional loads comprising of a ceramic disk have limited peak and average power handling capability and are therefore not suitable for high gradient TW linacs. This overview will focus on 'vacuum dry' or 'all-metal' loads that do not employ any dielectric interface between vacuum and absorber. The first prototype is an original design of RF loads for the Stanford Two-Mile Accelerator. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW043 | ||
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| TUPMB016 | Continuous-Wave Electron Linear Accelerators for Industrial Applications | linac, electron, klystron, resonance | 1142 |
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| Based on SINP MSU experience in developing continuous wave (CW) normal conducting (NC) electron linacs, we propose an optimal design for such accelerators with beam energy of up to 10 MeV and average beam power of up to several hundred kW. As an example of such design, we discuss the 1 MeV industrial CW linac with maximum beam power of 25 kW, which was recently commissioned at SINP MSU. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMB016 | ||
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| TUPOY025 | ProBE - Proton Boosting Extension for Imaging and Therapy | proton, cavity, linac, quadrupole | 1963 |
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| Conventional proton cyclotrons are practically limited by relativistic effects to energies around 250 MeV, sufficient to conduct proton therapy of adults but not for full-body proton tomography. We present an adaptation of the cyclinac scheme for proton imaging, in which a c.250 MeV cyclotron used for treatment feeds a linac that delivers a lower imaging current at up to 350 MeV. Our ProBE cavity design envisages a gradient sufficient to obtain 100 MeV acceleration in 3 metres after focusing is included, suitable for inclusion in the layouts of existing proton therapy centres such as the UK centre under construction at Christie Hospital. In this paper, we present the results of design studies on the linac optics and RF cavity parameters. We detail particle transmission studies and tracking simulation studies. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOY025 | ||
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| TUPOY027 | Beam Dynamics Studies into Grating-based Dielectric Laser-driven Accelerators | electron, laser, emittance, simulation | 1970 |
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Funding: Work supported by the EU under grant agreement 289191 and the STFC under the Cockcroft Institute core grant ST/G008248/1. Dielectric laser-driven accelerators (DLAs) based on gratings confine an electromagnetic field induced by a drive laser into a narrow vacuum channel where electrons travel and are accelerated. This can provide an alternative acceleration technology compared to conventional rf cavity accelerators. Due to the achievable high acceleration gradient of up to several GV/m this could pave the way for future ultra-short and low costμaccelerators. This contribution presents detailed beam dynamics simulations for multi-period double grating structures. Using the computer code VSim and realistic beam distributions, the achievable acceleration gradient and final beam quality in terms of emittance and energy spread are discussed. The results are then used for an overall optimization of the accelerating structure. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOY027 | ||
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| WEPMB007 | Error Estimation in Cavity Performance Test for the European XFEL at DESY | cavity, cryomodule, HOM, operation | 2128 |
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| The cavity performance tests, that is, vertical test (V.T.) and cryomodule test (C.T.), in the cavity/cryomodule mass production for XFEL have been done since 2012 at DESY, and is still on-going at present. At the comparatively initial stage of the mass production, the error estimation in the cavity performance tests was done for understanding how precisely those measurements are done at AMTF (Accelerator Module Test Facility). There are two parameters for the error estimation in V.T. One is the cable calibration parameter, and the other is the external Q-value, which is related to the power emitted from cavity. The measurement precision in the external Q-value depends on the measurement of coupling coefficient (β) strongly. Therefore, it is essential not to miss the β measurement for the precise measurement in V.T. On the other hand, as for C.T., the change of parameter (Kt), which is related to the evaluation of accelerating gradient, was used. As the result of the data analysis for Kt, the error was estimated to be 6%, and is related to the cavity performance degradation from V.T. to C.T. In this paper, the detailed data analysis and error estimation will be presented. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB007 | ||
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| WEPMB012 | Production and Investigation of Superconducting 9-Cell Cavity Made of Large Grain Nb in KEK | cavity, SRF, electron, niobium | 2141 |
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| For CW operation of superconducting cavity, reduction of heat load at cavity surface is one of important topics, since generated heat load is much higher than that of pulse wave. Using Large Grain (LG) Nb for superconducting cavity has possibility to reach higher Q0 than using Fine Grain Nb, which reduces heat load to 2K Helium. KEK Cavity Fabrication Facility(CFF) group had successfully produced superconducting 1-cell cavity made of LG Nb in 2013, and reached high Q0 at the vertical test (maximum field of 45 MV/m). Then, KEK CFF group started producing first superconducting 9-cell LG cavity in 2015, which will be completed in the end of December 2015. Whole processes of producing this cavity from sliced Nb are done in KEK. In this report, process flow and strategies of producing 9-cell cavity and results of vertical test will be presented in detail. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB012 | ||
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| WEPMB017 | High Gradient Cavity Performance in STF-2 Cryomodule for the ILC at KEK | cavity, cryomodule, radiation, HOM | 2158 |
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| The high power test for STF-2 cryomodule has completed successfully in 2015. Before cooldown of cryomodule, at first, the input coupler conditioning at room temperature is done with detuned cavities. After cooldown, the cavity conditioning, which is the main part in the performance test, is done by monitoring the radiation level measured at three locations around the cryomodule, and the heating and RF output at two HOM (Higher Order Mode) couplers. Consequently, it became clear the average accelerating gradient is 30 MV/m for STF-2 cryomodule (39 MV/m at max. and 15 MV/m at min.), and the second cavity string with four cavities had the significant performance degradation by heavy field emission due to the additional clean room work in the STF tunnel. As the following next steps, there are the LFD (Lorenz Force Detuning) measurement, LFD compensation by piezo, and long run for check of stable operation at high gradient. In the long run around 32 MV/m, each cavity without degradation showed the stable operation with the successful LFD compensation by piezo and RF feedback system. In this paper, the detailed test result will be presented. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB017 | ||
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| WEPMB023 | Hydroforming SRF Three-cell Cavity from Seamless Niobium Tube | cavity, niobium, SRF, superconductivity | 2170 |
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| We are developing the manufacturing method for superconducting radio frequency (SRF) cavities by using a hydroforming instead of using conventional electron beam welding. We expect higher reliability and reduced cost with hydroforming. For successful hydroforming, high-purity seamless niobium tubes with good formability as well as advancing the hydroforming technique are necessary. Using a seamless niobium tube from ATI Wah Chang, we were able to successfully hydroform a 1.3 GHz three-cell TESLA-like cavity and obtained an Eacc of 32 MV/m. A barrel polishing process was omitted after the hydroforming. The vertical test was carried out with very rough inside surface. We got amazing and interesting result. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB023 | ||
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| WEPMB035 | SRF Cavities for RAON | cavity, SRF, TRIUMF, factory | 2200 |
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| SRF cavities of superconducting linear accelerators in RAON are developed and tested at 2K/4K. 1st Quarter Wave Resonator (QWR) and Half Wave Resonator (HWR) are fabricated by a domestic vender and tested in the TRIUMF's facility. The measured Q factors are above the required values at the operating gradients. And the predicted multipacting phenomena are observed in the test and easily conditioned. The Q factors decreased after a slow cooldown and enhanced at 4K tests by a low temperature baking. Based on these tests, modified bare cavities are newly developed, jacketed and will be tested with tuners and power couplers. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB035 | ||
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| WEPMB056 | CVD Deposition of Nb Based Materials for SRF Cavities | niobium, SRF, lattice, superconductivity | 2241 |
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| Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. Advancements in technology have taken bulk niobium close to its theoretical operational limits, pushing the research to explore novel materials, such as niobium based alloys. Nitrides of niobium offer such an alternative, exhibiting a higher Tc compared to bulk niobium. Replacing then the niobium with a material with better thermal conductivity, such as copper, coated with thin films of nitrides in a multilayer S-I-S would lead to improved performance at reduced cost. Physical vapour deposition (PVD) is currently used to produce these coatings, but it suffers from lack of conformity. This issue can be resolved by using chemical vapour deposition (CVD), which is able to produce high quality coatings over surfaces with a high aspect ratio. This project explores the use of CVD techniques to deposit NbN thin films starting from their chlorinated precursors. The samples obtained are characterized via SEM, FIB, XRD, and EDX. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB056 | ||
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| WEPMR024 | RF Measurements on High Performance Nb3Sn Cavities | cavity, niobium, SRF, radio-frequency | 2320 |
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| A single-cell 1.3 GHz ILC-shape thin-film Nb3Sn-on-Nb cavity recently achieved accelerating gradients of >16 MV/m with a record Q0 of approx. 2·1010 at 4.2 K, exceeding the power efficiency seen in the current most efficient niobium cavities. A concurrent study of the coating process has resulted in a coating procedure that is capable of replicating this performance in other single-cell cavities. In this paper we demonstrate the RF performance and behaviour of these next generation SRF cavities, with an emphasis on both the impact from both external magnetic fields and the cavity cool down procedure on cavity performance. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR024 | ||
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| WEPMY027 | Feasibility Study of Plasma Wakefield Acceleration at the CLARA Front End Facility | plasma, experiment, wakefield, simulation | 2617 |
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Funding: Cockcroft Institute Core Grant and STFC Plasma wakefield acceleration has been proposed at the CLARA Front End (FE) facility at Daresbury Laboratory. The initial phase of the experiment will acceleration of the tail of a single electron bunch, and the follow-up experiment will study preserving a high quality beam based on a two-bunch acceleration scenario. In this paper, a concept for the initial experiment is outlined and detailed simulation results are presented. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY027 | ||
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| THPMY042 | Laser Applications at Accelerators | laser, network, electron, ion | 3751 |
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Funding: This project has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289191. The LA3NET consortium has developed advanced laser applications for particle accelerators within an international research and training network. It brought together research centers, universities, and industry partners to carry out collaborative research into all the above areas and jointly train the next generation of researchers. This contribution presents selected research highlights from the LA3NET network. It shows how enhanced ionization schemes can provide better ion beams for radioactive beam facilities, and how RF photo injectors can produce high brightness electron beams. It also presents results from studies into ultra-compact, fiber optics-based electron accelerators and new radiation sources based on laser accelerated beams. Finally, it summarizes how electro-optical techniques, laser velocimeters, and laser emittance meters can all help characterize beams with better time and spatial resolution in non-invasive ways. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY042 | ||
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| THPOR041 | High Gradient Properties of a CLIC Prototype Accelerating Structure made by Tsinghua University | operation, timing, vacuum, experiment | 3874 |
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| A CLIC prototype structure, T24_THU_#1, was recently high-gradient tested at KEK X-band test stand, Nextef. The copper parts of this 24-cell TW structure were delivered from CERN, were bonded and brazed, bench-tested and tuned in Tsinghua University. The aim of this test was not only to verify the cavity high-gradient properties under 100 MV/m but also to study the breakdown phenomenon in high gradient. High power test results were presented and breakdown rate under 100 MV/m was compared to previously-tested CLIC prototype structures. The assembly capability of Tsinghua University for X-band high gradient structures was validated by the good high gradient performance of T24_THU_#1. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR041 | ||
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| THPOR044 | mm-Wave Standing-Wave Accelerating Structures for High-Gradient Tests | cavity, plasma, experiment, RF-structure | 3884 |
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| We present the design and parameters of single-cell accelerating structures for high-gradient testing at 110 GHz. The purpose of this work is to study the basic physics of ultrahigh vacuum RF breakdown in high-gradient RF accelerators. The accelerating structures consist of pi-mode standing-wave cavities fed with TM01 circular waveguide mode. The geometry and field shape of these accelerating structures is as close as practical to single-cell standing-wave X-band accelerating structures, more than 40 of which were tested at SLAC. This wealth of X-band data will serve as a baseline for these 110 GHz tests. The structures will be powered from a pulsed MW gyrotron oscillator. One MW of RF power from the gyrotron may allow us to reach a peak accelerating gradient of 400 MeV/m. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR044 | ||
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