TITLE

Particle-in-cell simulations for virtual cathode oscillator including foil ablation effects

AUTHOR(S)
Singh, Gursharn; Chaturvedi, S.
PUB. DATE
June 2011
SOURCE
Physics of Plasmas;Jun2011, Vol. 18 Issue 6, p063104
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
We have performed two- and three-dimensional, relativistic, electromagnetic, particle-in-cell simulations of an axially extracted virtual cathode oscillator (vircator). The simulations include, for the first time, self-consistent dynamics of the anode foil under the influence of the intense electron beam. This yields the variation of microwave output power as a function of time, including the role of anode ablation and anode-cathode gap closure. These simulations have been done using locally developed particle-in-cell (PIC) codes. The codes have been validated using two vircator designs available from the literature. The simulations reported in the present paper take account of foil ablation due to the intense electron flux, the resulting plasma expansion and shorting of the anode-cathode gap. The variation in anode transparency due to plasma formation is automatically taken into account. We find that damage is generally higher near the axis. Also, at all radial positions, there is little damage in the early stages, followed by a period of rapid erosion, followed in turn by low damage rates. A physical explanation has been given for these trends. As a result of gap closure due to plasma formation from the foil, the output microwave power initially increases, reaches a near-flat-top and then decreases steadily, reaching a minimum around 230 ns. This is consistent with a typical plasma expansion velocity of ∼2 cm/μs reported in the literature. We also find a significant variation in the dominant output frequency, from 6.3 to 7.6 GHz. This variation is small as long as the plasma density is small, up to ∼40 ns. As the AK gap starts filling with plasma, there is a steady increase in this frequency.
ACCESSION #
62010240

 

Related Articles

  • Optimizing nonstationary 38-GHz pulse-train relativistic backward wave oscillator with low guiding magnetic field. Ermakov, A. E.; Zhakov, S. V.; Mesyats, G. A.; Rostov, V. V.; Ul'maskulov, M. R.; Sharypov, K. A.; Shpak, V. G.; Shunailov, S. A.; Yalandin, M. I. // Technical Physics Letters;Sep2008, Vol. 34 Issue 9, p806 

    Characteristics of a compact relativistic backward wave oscillator (BWO) operating in the 8-mm wavelength range have been optimized using the results of experimental investigation and numerical simulations. The coefficient of electron beam power conversion into microwave pulses close to unity is...

  • Study of the formation of a fast electron beam in a coaxial gas diode in the unlimited emission model. Grishkov, A. A.; Artemov, K. P.; Belomytsev, S. Ya.; Ryzhov, V. V.; Turchanovskii, I. Yu.; Shklyaev, V. A. // Plasma Physics Reports;Sep2009, Vol. 35 Issue 9, p779 

    The formation of a fast electron beam in a coaxial gas diode is simulated using the OOPIC Pro particle-in-cell code under the assumption of unlimited cathode emissivity. It is shown that fast electrons are generated near the cathode. The so-called �contracting-capacitor� mechanism of...

  • Wide-aperture high-current electron beam in a discharge with cathode plasma at elevated pressure. Sorokin, A. R. // Technical Physics;Mar2009, Vol. 54 Issue 3, p372 

    This work pursues investigations into the discharge with a cathode plasma in a cavity one wall of which is an insulating plate with a hole D in diameter (the cavity is 0.5 or 1.5 mm wide). This discharge is thoroughly analyzed in comparison with the high-voltage hollow-cathode discharge. Owing...

  • The Current of an Annular Electron Beam with Virtual Cathode in a Drift Tube. Belomyttsev, S.Ya.; Grishkov, A.A.; Korovin, S.D.; Ryzhov, V.V. // Technical Physics Letters;Aug2003, Vol. 29 Issue 8, p666 

    An analysis based on the laws of conservation of energy and the z components of the field and particle momentum shows that a thin magnetized annular electron beam in a homogeneous drift tube behind a virtual cathode under stationary conditions occurs in a “squeezed” state...

  • Properties of ceramic honeycomb cathodes. Friedman, M.; Myers, M. C.; Chan, Y.; Sethian, J. D. // Applied Physics Letters;4/7/2008, Vol. 92 Issue 14, p141501 

    A high current electron beam was emitted from slabs of ceramic honeycomb that were placed 2 mm in front of the primary electron emitters. Inside the ceramic honeycomb pores, the primary electrons are multiplied many folds by a secondary emission process creating plasma from which the electron...

  • Generation of gigawatt level beat waves. Guolin Li; Ting Shu; Jun Zhang; Jianhua Yang; Chengwei Yuan // Applied Physics Letters;6/7/2010, Vol. 96 Issue 23, p234102 

    The initial experimental results of generating gigawatt level beat waves with two microwave sources are presented. The detailed measures for enhancing the power handling capacities of the applied devices are explained. In the experiments, the operation frequencies of the microwave sources are...

  • An X-band phase-locked relativistic backward wave oscillator. Wu, Y.; Li, Z. H.; Xu, Z.; Jin, X.; Ma, Q. S. // Physics of Plasmas;Aug2015, Vol. 22 Issue 8, p1 

    For the purpose of coherent high power microwave combining at high frequency band, an X-band phase-locked relativistic backward wave oscillator is presented and investigated. The phaselocking of the oscillator is accomplished by modulation of the electron beam before it reaches the oscillator....

  • Relativistic performance analysis of a high current density magnetron injection gun. Barnett, L. R.; Luhmann, Jr., N. C.; Chiu, C. C.; Chu, K. R. // Physics of Plasmas;Sep2009, Vol. 16 Issue 9, p093111 

    Electron beam quality is essential to the performance of millimeter-wave gyroamplifiers, particularly the gyrotron traveling-wave tube amplifier, which is extremely sensitive to the electron velocity spread and emission uniformity. As one moves up in power and frequency, the quality of the...

  • Simulation of monoenergetic electron generation via laser wakefield accelerators for 5–25 TW lasers. Tsung, F. S.; Lu, W.; Tzoufras, M.; Mori, W. B.; Joshi, C.; Vieira, J. M.; Silva, L. O.; Fonseca, R. A. // Physics of Plasmas;May2006, Vol. 13 Issue 5, p056708 

    In 2004, using a 3D particle-in-cell (PIC) model [F. S. Tsung et al., Phys. Rev. Lett. 93, 185004 (2004)], it was predicted that a 16.5 TW, 50 fs laser propagating through nearly 0.5 cm of 3×1018 cm-3 preformed plasma channel would generate a monoenergetic bunch of electrons with a central...

Share

Read the Article

Courtesy of THE LIBRARY OF VIRGINIA

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics