Author: Perez, D.
Paper Title Page
MOPAB146 Status of the C-Band Engineering Research Facility (CERF-NM) Test Stand Development at LANL 509
 
  • D. Gorelov
    Private Address, Los Alamos, USA
  • R.L. Fleming, S.K. Lawrence, J.W. Lewellen, D. Perez, M.E. Schneider, E.I. Simakov, T. Tajima
    LANL, Los Alamos, New Mexico, USA
  • M.E. Middendorf
    ANL, Lemont, Illinois, USA
 
  Funding: LDRD-DR Project 20200057DR
C-Band structures research is of increasing interest to the accelerator community. The RF frequency range of 4-6 GHz gives the opportunity to achieve significant increase in the accelerating gradient, and having the wakefields at the manageable levels, while keeping the geometric dimensions of the structure technologically convenient. Strong team of scientists, including theorists researching properties of metals under stressful thermal conditions and high electromagnetic fields, metallurgists working with copper as well as alloys of interest, and accelerator scientists developing new structure designs, is formed at LANL to develop a CERF-NM facility. A 50 MW, 5.712 GHz Canon klystron, was purchased in 2019, and laid the basis for this facility. As of Jan-21, the construction of the Test Stand has been finished and the high gradient processing of the waveguide components has been started. Future plans include high gradient testing of various accelerating structures, including benchmark C-band accelerating cavity, a proton ß=0.5 cavity, and cavities made from different alloys. An upgrade to the facility is planned to allow for testing accelerator cavities at cryogenic temperatures.
 
poster icon Poster MOPAB146 [3.778 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB146  
About • paper received ※ 17 May 2021       paper accepted ※ 26 May 2021       issue date ※ 19 August 2021  
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MOPAB362 Atomistic Modeling of the Coupling Between Electric Fields and Bulk Plastic Deformation in Rf Structures 1125
 
  • S. Bagchi, D. Perez
    LANL, Los Alamos, New Mexico, USA
 
  Funding: LANL-LDRD
A notable bottleneck in achieving high-gradient RF technology is dictated by the onset of RF breakdown. While bulk mechanical properties are known to significantly affect breakdown propensity, the underlying mechanisms coupling RF fields to bulk plastic deformation in experimentally relevant thermo-electrical loading conditions remain to be identified at the atomic scale. Here, we present results of large-scale molecular dynamics simulations (MD) to investigate possible modes of coupling. We consider the activation of Frank-Read (FR) sources, which leads to dislocation multiplication, under the action of bi-axial thermal stresses and surface electric-field. With a charge-equilibration formalism incorporated in a classical MD model, we show that a surface electric field acting on an either preexisting or dislocation-induced surface step, can generate a long-range resolved shear stress field inside the bulk of the sample. We investigate the feedback between step growth following dislocation emission and subsequent activations of FR sources and discuss the regimes of critical length-scales and densities of dislocations, where such a mechanism could promote RF breakdown precursors.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB362  
About • paper received ※ 19 May 2021       paper accepted ※ 10 June 2021       issue date ※ 19 August 2021  
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MOPAB371 A Coupon Tester for Normal Conducting High-Gradient Materials 1147
 
  • J.W. Lewellen, D. Gorelov, D. Perez, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  • M.E. Schneider
    Michigan State University, East Lansing, Michigan, USA
 
  Funding: Los Alamos National Laboratory LDRD Program
A coupon tester is an RF structure used to subject a material sample to very high RF fields, with the fields on the sample, or coupon, being higher than elsewhere in the cavity. To date, most such cavities were originally intended to explore the RF properties of superconducting materials, and can expose the sample to strong magnetic fields, but weak to no electric fields. As part of a program to develop materials and structures for high-gradient (> 100 MV/m), low-breakdown-rate normal-conducting accelerators, we have designed a C-band (5.712 GHz) cavity intended to subject samples to both magnetic and electric fields comparable to those experienced in high-gradient structure designs, using a TM-mode cavity; the electric and magnetic fields along the sample coupon can be directly compared to the fields on the iris of high-gradient structures. This poster will present the design criteria for our coupon tester cavity, nominal operating parameters, and our structure concept. The cavity design will be refined over the next several months, and will be constructed and in service near the start of 2022.
 
poster icon Poster MOPAB371 [0.764 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB371  
About • paper received ※ 17 May 2021       paper accepted ※ 26 May 2021       issue date ※ 30 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)