Author: Dolgashev, V.A.
Paper Title Page
MOPML052 The Path to Compact, Efficient Solid-State Transistor-Driven Accelerators 520
 
  • D.C. Nguyen, C.E. Buechler, G.E. Dale, R.L. Fleming, M.A. Holloway, J.W. Lewellen, D. Patrick
    LANL, Los Alamos, New Mexico, USA
  • V.A. Dolgashev, E.N. Jongewaard, E.A. Nanni, J. Neilson, A.V. Sy, S.G. Tantawi
    SLAC, Menlo Park, California, USA
 
  Funding: Research presented in this work is supported by (LANL) Laboratory Directed Research and Development 20170521ER and by (SLAC) Department of Energy contract DE-AC02-76SF00515.
Small, lightweight, few-MeV electron accelerators that can operate with low-voltage power sources, e.g., solid-state transistors running on 50 VDC, instead of high-voltage klystrons, will provide a new tool to enhance existing applications of accelerators as well as to initiate new ones. Recent advances in gallium nitride (GaN) semiconductor technologies * have resulted in a new class of high-power RF solid-state devices called high-electron mobility transistors (HEMTs). These HEMTs are capable of generating a few hundred watts at S-, C- and X-bands at 10% duty factor. We have characterized a number of GaN HEMTs and verified they have suitable RF characteristics to power accelerator cavities **. We have measured energy gain as a function of RF power in a single low-beta C-band cavity. The HEMT powered RF accelerators will be compact and efficient, and they can operate off the low-voltage DC power buses or batteries. These all-solid-state accelerators are also more robust, less likely to fail, and are easier to maintain and operate. In this poster, we present the design of a low-beta, 5.1-GHz cavity and beam dynamics simulations showing continuous energy gain in a ten-cavity C-band prototype.
* See for example, http://www.wolfspeed.com/downloads/dl/file/id/463/product/174/cghv59350.pdf
** J.W. Lewellen et al., Proceedings of LINAC2016, Paper MO3A03
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML052  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUZGBE4 Toward High-Power High-Gradient Testing of mm-Wave Standing-Wave Accelerating Structures 1224
 
  • E.A. Nanni, V.A. Dolgashev, A.A. Haase, J. Neilson, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  • S. Jawla, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts, USA
  • S. C. Schaub
    MIT, Cambridge, Massachusetts, USA
  • B. Spataro
    INFN/LNF, Frascati (Roma), Italy
 
  Funding: This work is supported in part by Department of Energy contract DE-AC02-76SF00515 (SLAC) and DE-SC0015566 (MIT).
We will preliminary testing results for single-cell accelerating structures intended 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. We fabricated of two structures one in copper and the other in CuAg alloy. Cold RF tests confirm the design RF performance of the structures. 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 with a MW gyrotron oscillator that produces microsecond pulses. One megawatt of RF power from the gyrotron may allow us to reach a peak accelerating gradient of 400 MeV/m.
 
slides icon Slides TUZGBE4 [4.648 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBE4  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMF069 High Shunt Impedance Accelerating Structure with Distributed Microwave Coupling 2531
 
  • S.P. Antipov, R.A. Kostin, S.V. Kuzikov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
 
  Funding: DOE SBIR
Conventional traveling wave or pi-phase advance standing wave structures use coupling of the microwave power through the beam pipe. This feature constrains the cavity shunt impedance (efficiency) to relatively small values. As microwave power flows through the accelerating cells in such structures, the probability of breakdown in high gradient operation is greatly increased. In this paper we present results from an accelerating structure prototype with distributed microwave coupling, an approach invented at SLAC. These structures include one or more parallel waveguides which are loaded by accelerating cavities. In this configuration accelerating cavities are fed independently and completely isolated at the beam pipe. Thus there is no microwave power flow through the accelerating cavity, making this geometry favorable for high gradient operation and maximizing the shunt impedance.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF069  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPAL009 A TM01 Mode Launcher With Quadrupole Field Components Cancellation for High Brightness Applications 3631
 
  • G. Castorina
    INFN-Roma1, Rome, Italy
  • A.D. Cahill, J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • F. Cardelli, G. Franzini, A. Marcelli, B. Spataro
    INFN/LNF, Frascati (Roma), Italy
  • L. Celona, S. Gammino, G. Torrisi
    INFN/LNS, Catania, Italy
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • L. Ficcadenti
    Rome University La Sapienza, Roma, Italy
  • M. Migliorati, A. Mostacci, L. Palumbo
    Sapienza University of Rome, Rome, Italy
  • G. Sorbello
    University of Catania, Catania, Italy
 
  The R&D of high gradient radiofrequency (RF) devices is aimed to develop innovative accelerating structures based on new manufacturing techniques and materials in order to construct devices operating with the highest accelerating gradient. Recent studies have shown a large increase in the maximum sustained RF surface electric fields in copper structures operating at cryogenic temperatures. These novel approaches allow significant performance improvements of RF photoinjectors. Indeed the operation at high surface fields results in considerable increase of electron beam brilliance. This increased brilliance requires high field quality in the RF photoinjector and specifically in its power coupler. In this work we present a novel power coupler for the RF photoinjector. The coupler is a compact X-band TM01 mode launcher with a fourfold symmetry which minimized both the dipole and the quadrupole RF components.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL009  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPMF090 Linac Design Elements for Spaceborne Accelerators 4291
 
  • J.W. Lewellen, C.E. Buechler, G.E. Dale, M.A. Holloway, D.C. Nguyen, D. Patrick
    LANL, Los Alamos, New Mexico, USA
  • V.A. Dolgashev, E.N. Jongewaard, J. Neilson, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  • J-.M. Lauenstein
    NASA Goddard Space Flight Center, Greenbelt, USA
 
  Funding: Los Alamos National Laboratory LDRD and Program Development
Los Alamos National Laboratory, in collaboration with SLAC and Goddard Space Flight Center, have begun developing a high-duty-factor, MeV-range linear accelerator intended for use on satellites, specifically to probe the magnetosphere-ionosphere linkage. The design makes use of low-beta C-band cavities operating at moderate gradients, individually powered by 500-W RF amplifier chips. We present the current state of the design, and technology maturation efforts including RF amplifier performance studies, cavity tuner design and an initial acceleration test using a DC beam source and single RF cavity.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF090  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPML125 Efficiency Analysis of High Average Power Linacs for Environmental and Industrial Applications 4970
 
  • M. Shumail, V.A. Dolgashev
    SLAC, Menlo Park, California, USA
 
  Funding: U.S. Department of Energy, HEP under Research Opportunities in Accelerator Stewardship: LAB 16-1438.
We present comprehensive efficiency equations and useful scaling laws to optimally determine design parameters for high efficiency rf linacs. For the first time we have incorporated the parasitic losses due to the higher order cavity modes into the efficiency analysis of the standing wave (SW) and travelling wave (TW) accelerators. We have also derived the efficiency equations for a new kind of attenuation-independent-impedance travelling wave (ATW) accelerators where the shunt impedance can be optimized independent of the group velocity. We have obtained scaling laws which relate the rf to beam efficiency to the linac length, beam aperture radius , phase advance per cell, and the type of accelerating structure: SW versus TW, disk-loaded (DL) versus nose-cone (NC). We give an example of using these scaling laws to determine a feasible set of parameters for a 10 MeV, 10 MW linac with 97.2% efficiency.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML125  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPML126 Design of High Efficiency High Power CW Linacs for Environmental and Industrial Applications 4974
 
  • M. Shumail, V.A. Dolgashev, C.M. Markusen
    SLAC, Menlo Park, California, USA
 
  Funding: US Department of Energy, Office of High Energy Physics, through Accelerator Stewardship Grant
We have used our accelerator design toolbox equations to design three high efficiency and high power CW accelerators for the environmental and medical applications. These are: 2MeV-1MW, 10MeV-10MW, and 10MeV-1MW linacs. These are all 10 m long, 1.3 GHz, π-mode standing wave structures with design efficiencies of 96.8, 97.4 and 86.5 %, and optimal coupling coefficients of 32.9, 43.5, and 7.45, respectively. We present the detailed design parameters of these linacs. The study of single-bunch beam breakup for these linacs and the simulations results from ABCI are also included. The initial cavities are optimized according to the speed of the electron bunch to maximize the shunt impedance. The plots of peak surface fields on these cavities are also presented. We have also included a detailed thermal analysis of these linacs. Finally, we present the results of ASTRA simulations of the three linacs with magnetic focusing. We have also included the complete design of rf-distributed-coupling manifold for the third linac along with the HFSS® simulation results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML126  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)