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MOOP01
Welcome and Overview of the Conference  
 
  • Y. Jaski
    ANL, Lemont, Illinois, USA
 
  Stephen Streiffer (Deputy Laboratory Director for Science & Technology and Interim Associate Laboratory Director for the Photon Sciences Directorate) and Yifei Jaski (MEDSI2020 Conference Chair) welcome you to the 11th International Conference on Mechanical Engineering Design of Synchrotron Radiation Equipment and Instrumentation (MEDSI2020).  
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TUPB06 Design of Miniature Waveguides and Diamond Window Assembly for RF Extraction and Vacuum Isolation for the CWA 156
 
  • B.K. Popovic, S.H. Lee, S. Sorsher, K.J. Suthar, E. Trakhtenberg, G.J. Waldschmidt, A. Zholents
    ANL, Lemont, Illinois, USA
  • A.E. Siy
    UW-Madison, Madison, Wisconsin, USA
 
  Funding: This manuscript is based upon work supported by Laboratory Directed Research and Development (LDRD) funding from Argonne National Laboratory
This paper outlines the design of a diamond vacuum window and a millimeter wavelength (mmWave) waveguide assembly that will hold vacuum but still allow the mmWaves to propagate out of the structure for diagnosis and thermal management purposes. Currently under development at Argonne is a corrugated wakefield accelerator (CWA) that will operate at mmWave frequencies, with its fundamental mode of operation at 180 GHz, and relatively high power levels, up to 600 W. The fundamental mode needs to be extracted from the accelerator at approximately every 0.5 m to prevent the unwanted heating of the accelerator structure. Therefore, the structure is intentionally designed so this fundamental mode does not propagate further, instead it is transmitted through the waveguide assembly under vacuum and out via the vacuum window. As a result of the relatively high mmWave power densities, CVD diamond was chosen as the vacuum window material, due to its low electromagnetic losses, mechanical strength, and for its superior thermo-physical properties. Mechanically it is necessary to be able to hold the tight tolerances necessary for windows performance at millimeter wavelengths. Other mechanical difficulties involve assembly of the window due to CVD diamond material and preservation of ultra high vacuum even if the integrity of the CVD diamond window is somehow compromised.
 
poster icon Poster TUPB06 [0.386 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-MEDSI2020-TUPB06  
About • paper received ※ 26 July 2021       paper accepted ※ 05 October 2021       issue date ※ 02 November 2021  
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TUPB07 Vacuum Analysis of a Corrugated Waveguide Wakefield Accelerator 160
 
  • K.J. Suthar, S. Sorsher, E. Trakhtenberg, A. Zholents
    ANL, Lemont, Illinois, USA
 
  Funding: This is based upon work supported by LDRD funding from Argonne National Laboratory, provided by the Director, Office of Science, of the U.S. Department of Energy under contract DE-AC02-06CH11357.
The vacuum level in a 2 mm diameter, 0.5 m-long copper corrugated waveguide tube proposed* for a compact high repetition rate wakefield accelerator has been investigated. The analytical calculations have been found to be in good agreement with a result of computer modeling using a finite element method. A representative experiment has been conducted using a smooth copper tube with the same diameter as the corrugated tube and a 1/3 length of the corrugated tube. The vacuum level calculated for this experiment agrees well with the measurement.
*A. Zholentset et al., inProc. 9th International Particle Accelerator Conference (IPAC’18), Vancouver, BC, Canada, 29 April-04 May 2018, ser. IPAC Conference, pp. 1266’1268.
 
poster icon Poster TUPB07 [0.954 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-MEDSI2020-TUPB07  
About • paper received ※ 22 July 2021       paper accepted ※ 29 October 2021       issue date ※ 05 November 2021  
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TUPB13
Modular Solid-State Power Amplifiers for Particle Accelerator Facilities  
 
  • M. Lau, M. Ehinger, M. Schweizer
    TRUMPF Huettinger, Freiburg, Germany
  • G. Baumann, M. Beyer, R. Heilig, J. Weber
    HBH Microwave GmbH, Stutensee, Germany
 
  The need for individual power levels and control interfaces results in unique power amplifier systems used to accelerate particles via microwaves. Solid-state power amplifiers (SSPA) offer the advantage of a good modularity and scalability to address these needs. However, the design, development, and production of such a complex SSPA system with sufficient reliability is challenging and expensive, due to the customized requirements. We are addressing this issue by offering a high flexibility with our modular design in combination with our in-house developed control software. Based on our experience we are eliminating potential downsides by industrialization and still offering a high grade of flexibility to meet the individual needs. At the best practice example of our circulator tracking, developed for low frequencies around 80MHz, we will demonstrate how customization and industrialization can come along together.  
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TUPB15 Fabrication of the Transition Section of a Corrugated Wakefield Accelerator via Laser Micromachining 175
 
  • P. Bado, M. Dugan, A.A. Said
    Translume, Inc., Ann Arbor, Michigan, USA
  • A.E. Siy
    UW-Madison, Madison, Wisconsin, USA
  • K.J. Suthar, A. Zholents
    ANL, Lemont, Illinois, USA
 
  Funding: This manuscript is based upon work supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357
A cylindrical, corrugated wakefield accelerating (CWA) structure is being designed to facilitate sub-terahertz Cerenkov radiation produced by an electron bunch propagating in a waveguided structure comprising accelerating sections and transition sections*. The accelerating structure consists of several copper-based 50-cm long sections of internally corrugated tubes with 2-mm inner-diameter. These sections are coupled together using transition sections, which are also copper-based. The transition section has a main body diameter ranging from 2mm to 3.2mm and its length is about 14mm. Two sets of four orthogonal waveguides radiate from the central body. Beside their mechanical coupling function, these transition sections provide for periodic monitoring of the centering of the electron bunch, and for removal of unwanted higher-order EM modes. The fabrication of these transition sections is presented. The fabrication process is based on the use of a sacrificial fused silica glass mandrel, whose body corresponds to the inner volume of the copper element. This fused silica mandrel is subsequently electroplated. The micro-fabrication of a prototype of the transition section is underway. Modelling of various fabrication errors was undertaken to understand their effect and to determine tolerances. Source of machining imperfections are reviewed and their impact compared to the modelling results.
*A. Zholents et al., "A conceptual design of a Compact Wakefield Accelerator for a high repetition rate multi user Xray Free-Electron Laser Facility," in Proc. 9th Int.l Particle Accel. Conf., 2018
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-MEDSI2020-TUPB15  
About • paper received ※ 27 July 2021       paper accepted ※ 19 October 2021       issue date ※ 30 October 2021  
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TUPC01 Study of Copper Microstructure Produced by Electroforming for the 180-GHz Frequency Corrugated Waveguide 178
 
  • K.J. Suthar, G. Navrotski, A. Zholents
    ANL, Lemont, Illinois, USA
  • P.R. Carriere
    RadiaBeam, Santa Monica, California, USA
 
  Funding: Work supported by Laboratory Directed Research and Development funding from Argonne National Laboratory, provided by the Director, Office of Science, of the US DOE under contract DE-AC02-06CH11357.
Fabrication of the corrugated structure that generates a field gradient 100 m-1 at 180 GHz is challenging and required an unconventional method of production. The corrugated waveguide with 2 mm inner diameter will be produced by electroplating copper on the aluminum mandrel as proposed in the reference*. A thin seed layer is usually applied to achieve uniform wetting to plate copper on the aluminum mandrel. The copper waveguide is retrieved by removing aluminum and the seed layer. Therefore, uniform copper plating and etching of the seed layer and the Aluminum mandrel is a crucial step to keep the surface free of impurities that are especially necessary for the RF application. Previous studies suggest that electroplated copper has variations in both electrical and mechanical properties compared with those of bulk copper from the batches of production. In this paper, we discuss the copper microstructure produced by the electroforming method and literature study on the variations, which can be attributed to the disparity of the crystallinity of grains structure in plated material.
*A. Zholentset al., "A Conceptual Design of a Compact Wakefield Accelerator for a High Repetition Rate Multi-User X-ray Free-Electron Laser Facility, "in Proc. IPAC 18, 2018, pp. 1266-1268.
 
poster icon Poster TUPC01 [1.717 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-MEDSI2020-TUPC01  
About • paper received ※ 21 July 2021       paper accepted ※ 05 November 2021       issue date ※ 06 November 2021  
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TUPC05
Design and Fabrication of a Waveguide for Conductivity Measurement of Electroplated Copper at 170GHz - 200GHz  
 
  • A.E. Siy, N. Behdad, J.H. Booske
    UW-Madison, Madison, Wisconsin, USA
  • S.H. Lee, S. Sorsher, K.J. Suthar, E. Trakhtenberg, G.J. Waldschmidt, A. Zholents
    ANL, Lemont, Illinois, USA
 
  Funding: This work is supported by LDRD funding from Argonne National Laboratory, provided by the Director, Office of Science, of the U.S. Department of Energy under contract DE-AC02-06CH11357
Beam driven wakefield accelerators offer great potential for the realization of compact, low-cost x-ray free electron laser (XFEL) sources. Achieving high accelerating gradients in these devices requires the use of mm-wave RF structures which present a range of fabrication challenges due to their small size and tight dimensional tolerances. One promising technique for manufacturing these structures involves electroplating a mandrel with copper and subsequently dissolving the mandrel to leave behind the desired metal cavity. Because the resulting copper shell is electroplated, its purity, grain structure, and surface finish will be different from that of conventionally machined copper. Understanding the electrical and thermal performance of the electroformed components requires experimental measurement of the plated copper material properties. In this paper, an experiment for measuring the conductivity of electroplated copper at 170 GHz-200 GHz using a WR-5 waveguide meander is presented and the results are applied to the design of a corrugated waveguide wakefield accelerator.
 
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TUPC16
Precision Electrochemical Fabrication of Corrugated Waveguides  
 
  • D.X. Liu, H.M. Garich, T.D. Hall, M.E. Inman, S.T. Snyder, E.J. Taylor
    Faraday Technology, Inc., Clayton, Ohio, USA
  • X. Lu
    Northern Illinois University, DeKalb, Illinois, USA
  • X. Lu, J.G. Power, D.S. Scott, J. Shao
    ANL, Lemont, Illinois, USA
 
  Funding: The U.S. Department of Energy (DOE) provided financial support for this work under the contract award number: DE-SC0020782.
Advancements in high energy physics require continuous innovations in hardware to support the generation, amplification, transmission, modulation, and detection of radio frequency (RF) electromagnetic waves. Waveguides have garnered increasing interest due to their integral function in the transmission, amplification, and/or manipulation of electromagnetic waves. Waveguides operating in higher than conventional frequency ranges, e.g., 30 to 300 GHz, are of particular interest given the scaling of gradient and shunt impedance with frequency. These higher frequencies necessitate features, such as corrugations, with significantly smaller dimensions. However, traditional manufacturing approaches are inadequate, in terms of manufacturing precision and cost, to meet these requirements - thus, novel fabrication strategies are required. Herein, an economic fabrication approach for electroforming high-purity 26 GHz cylindrical copper waveguides with internal corrugations is presented. A custom, low-additive electrolyte was employed to mitigate impurity inclusion within the copper electroform, ensuring high-purity copper waveguides. Pulse-modulated waveforms employed during copper electrodeposition selectively controlled ionic transport as well as the subsequent deposit morphology and thus facilitate complete copper filling of the corrugations. Scale-up from ~2- to ~6-inch waveguides were demonstrated and confirm the versatility of the pulse-modulated electroforming strategy. A cold test of the ~2-inch copper waveguide using a vector network analyzer (VNA) was conducted. The results of the S-parameter measurements and the bead-pull test indicate reasonable agreement with the design by CST simulation, which validates the novel pulse-modulated electroforming approach.
 
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THCL01
Closing Remarks  
 
  • Y. Jaski
    ANL, Lemont, Illinois, USA
 
  Yifei Jaski (MEDSI2020 Conference Chair) and Brad Mountford (International Organizing Committee Chair) provide closing remarks.  
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