3-D em PIC simulation study on low-frequency oscillation in a fusion gyrotron

Ming-Chieh Lin, David N. Smithe

Research output: Chapter in Book/Report/Conference proceedingConference contributionResearchpeer-review

Abstract

In a previous study, it was found that not only magnetic compression profile but initial thermal velocities of electrons play an important role in causing a low frequency oscillation (LFO) in the operation of a magnetron injection gun (MIG) employed in an MIT fusion gyrotron. An unphysical particle boundary condition, i.e., large initial thermal velocities of electrons, had to be assumed to produce the LFO in the 3-D electromagnetic (EM) particle-in-cell (PIC) simulation. In this work, we have included the gyrotron cavity along with the MIG as well as a large vacuum envelope representing the vacuum chamber similar to that employed in the MIT experiments. In the EM PIC simulation, it is found that the momentum of electrons is suppressed by the space charge due to the vacuum envelope. For the first time, without unphysical approximations, the LFO could be reproduced in the time domain EM PIC simulations. The initial velocity spread at the cathode temperature is assumed in this simulation in contrast to an unphysical larger velocity spread formerly used.

Original languageEnglish
Title of host publication2019 International Vacuum Electronics Conference, IVEC 2019
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781538675342
DOIs
StatePublished - 2019 Apr 1
Event2019 International Vacuum Electronics Conference, IVEC 2019 - Busan, Korea, Republic of
Duration: 2019 Apr 282019 May 1

Publication series

Name2019 International Vacuum Electronics Conference, IVEC 2019

Conference

Conference2019 International Vacuum Electronics Conference, IVEC 2019
CountryKorea, Republic of
CityBusan
Period19/04/2819/05/1

Fingerprint

Fusion reactions
fusion
low frequencies
oscillations
Vacuum
electromagnetism
cells
Electrons
envelopes
simulation
magnetic compression
injection
vacuum
electrons
vacuum chambers
Electric space charge
space charge
Momentum
Cathodes
cathodes

Keywords

  • Low-frequency oscillations
  • conformal finite-difference time-domain particle-in-cell
  • gyrotron
  • magnetic mirror
  • magnetron injection gun

Cite this

Lin, M-C., & Smithe, D. N. (2019). 3-D em PIC simulation study on low-frequency oscillation in a fusion gyrotron. In 2019 International Vacuum Electronics Conference, IVEC 2019 [8744759] (2019 International Vacuum Electronics Conference, IVEC 2019). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/IVEC.2019.8744759
Lin, Ming-Chieh ; Smithe, David N. / 3-D em PIC simulation study on low-frequency oscillation in a fusion gyrotron. 2019 International Vacuum Electronics Conference, IVEC 2019. Institute of Electrical and Electronics Engineers Inc., 2019. (2019 International Vacuum Electronics Conference, IVEC 2019).
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Lin, M-C & Smithe, DN 2019, 3-D em PIC simulation study on low-frequency oscillation in a fusion gyrotron. in 2019 International Vacuum Electronics Conference, IVEC 2019., 8744759, 2019 International Vacuum Electronics Conference, IVEC 2019, Institute of Electrical and Electronics Engineers Inc., 2019 International Vacuum Electronics Conference, IVEC 2019, Busan, Korea, Republic of, 19/04/28. https://doi.org/10.1109/IVEC.2019.8744759

3-D em PIC simulation study on low-frequency oscillation in a fusion gyrotron. / Lin, Ming-Chieh; Smithe, David N.

2019 International Vacuum Electronics Conference, IVEC 2019. Institute of Electrical and Electronics Engineers Inc., 2019. 8744759 (2019 International Vacuum Electronics Conference, IVEC 2019).

Research output: Chapter in Book/Report/Conference proceedingConference contributionResearchpeer-review

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N2 - In a previous study, it was found that not only magnetic compression profile but initial thermal velocities of electrons play an important role in causing a low frequency oscillation (LFO) in the operation of a magnetron injection gun (MIG) employed in an MIT fusion gyrotron. An unphysical particle boundary condition, i.e., large initial thermal velocities of electrons, had to be assumed to produce the LFO in the 3-D electromagnetic (EM) particle-in-cell (PIC) simulation. In this work, we have included the gyrotron cavity along with the MIG as well as a large vacuum envelope representing the vacuum chamber similar to that employed in the MIT experiments. In the EM PIC simulation, it is found that the momentum of electrons is suppressed by the space charge due to the vacuum envelope. For the first time, without unphysical approximations, the LFO could be reproduced in the time domain EM PIC simulations. The initial velocity spread at the cathode temperature is assumed in this simulation in contrast to an unphysical larger velocity spread formerly used.

AB - In a previous study, it was found that not only magnetic compression profile but initial thermal velocities of electrons play an important role in causing a low frequency oscillation (LFO) in the operation of a magnetron injection gun (MIG) employed in an MIT fusion gyrotron. An unphysical particle boundary condition, i.e., large initial thermal velocities of electrons, had to be assumed to produce the LFO in the 3-D electromagnetic (EM) particle-in-cell (PIC) simulation. In this work, we have included the gyrotron cavity along with the MIG as well as a large vacuum envelope representing the vacuum chamber similar to that employed in the MIT experiments. In the EM PIC simulation, it is found that the momentum of electrons is suppressed by the space charge due to the vacuum envelope. For the first time, without unphysical approximations, the LFO could be reproduced in the time domain EM PIC simulations. The initial velocity spread at the cathode temperature is assumed in this simulation in contrast to an unphysical larger velocity spread formerly used.

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Lin M-C, Smithe DN. 3-D em PIC simulation study on low-frequency oscillation in a fusion gyrotron. In 2019 International Vacuum Electronics Conference, IVEC 2019. Institute of Electrical and Electronics Engineers Inc. 2019. 8744759. (2019 International Vacuum Electronics Conference, IVEC 2019). https://doi.org/10.1109/IVEC.2019.8744759