Two surface multipactor discharge with two-frequency rf fields and space-charge effects

Iqbal, Asif; Verboncoeur, John P.; Zhang, Peng

doi:10.1063/5.0070889

Cited by 12 publications

(24 citation statements)

References 58 publications

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“…The physics based understanding of the multipactor under multicarrier operation is still limited. In this regard, a series of recent publications [59,60,87,131] on two-frequency rf field induced two surface multipactor are noteworthy, which have shed light on some important new physics that can be useful in developing a more comprehensive understanding of multipactor under multicarrier operation.…”

Section: Novel Multipactor Prediction Methods For Multicarrier Rf Ope...mentioning

confidence: 99%

“…In Figure 3a, an electron is emitted from plate A and then accelerated by the RF electric field. Assuming one-dimensional (1D) motion in the y-direction, the flight trajectory of a multipactor electron is governed by the force law [2,25,84],…”

Section: Two-surface Multipactormentioning

confidence: 99%

“…; that maximises the denominator in Equation ( 6) regardless of the value of v 0 [2,84]. The maximum voltage allowed to sustain a multipactor will occur with the maximum negative value of the angle θ, determined by the condition that the initial emission velocity v 0 just allows the electron to escape from its birth electrode against the initially retarding field [2,84].…”

Section: à �mentioning

confidence: 99%

“…In their pioneering article in 1998 [6], Kishek and Lau presented the single surface multipactor susceptibility curves (shown in Figure 6a) as an efficient way to indicate the range of rf voltage (and power) over which an rf window may be susceptible to multipactor. The susceptibility curve can be obtained from simulation schemes such as single macroparticle [6,43,84] or multiparticle [60,87] Monte Carlo (MC) simulations as well as PIC simulations [61,88] and can be explained by a simple analytic theory proposed by Kishek and Lau [6]. If the design parameters lie within the multipactor boundaries of the susceptibility curve (representing a positive charge growth rate), then multipactor is possible and the design needs to be modified to mitigate multipactor.…”

Section: Single Surface Multipactormentioning

confidence: 99%

“…It has been found that specific configurations of the twofrequency rf operation can reduce multipactor strength in both single-surface [60] and two-surface [131,132] geometries compared to single frequency rf operation. In the single surface geometry, the modulation of the rf envelop due to the second carrier mode results in a lower instantaneous normal electric field (shown in the red circled region of the broken black curve in Figure 11a) for a longer duration during an rf period, which corresponds to a lower multipactor strength compared to Figure 6b [60].…”

Section: Recent Advances In Waveform Engineeringmentioning

confidence: 99%

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Recent advances in multipactor physics and mitigation

et al. 2023

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Recent progress made in the prediction, characterisation, and mitigation of multipactor discharge is reviewed for single‐ and two‐surface geometries. First, an overview of basic concepts including secondary electron emission, electron kinetics under the force law, multipactor susceptibility, and saturation mechanisms is provided, followed by a discussion on multipactor mitigation strategies. These strategies are categorised into two broad areas – mitigation by engineered devices and engineered radio frequency (rf) fields. Each approach is useful in different applications. Recent advances in multipactor physics and engineering during the past decade, such as novel multipactor prediction methods, understanding space charge effects, schemes for controlling multipacting particle trajectories, frequency domain analysis, high frequency effects, and impact on rf signal quality are presented. In addition to vacuum electron multipaction, multipactor‐induced ionization breakdown is also reviewed, and the recent advances are summarised.

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Section: Novel Multipactor Prediction Methods For Multicarrier Rf Ope...mentioning

confidence: 99%

Section: Two-surface Multipactormentioning

confidence: 99%

Section: à �mentioning

confidence: 99%

Section: Single Surface Multipactormentioning

confidence: 99%

Section: Recent Advances In Waveform Engineeringmentioning

confidence: 99%

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Recent advances in multipactor physics and mitigation

et al. 2023

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Two surface multipactor discharge with two-frequency rf fields and space-charge effects

2022

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This paper presents two-surface multipactor discharge with two-frequency rf fields using Monte Carlo simulations and Computer Simulation Technology (CST) Particle Studio. The effects of the relative strength and phase of the second carrier mode on multipactor susceptibility and time dependent physics are studied. Compared to single-frequency rf operation, shrinkage of multipactor susceptibility regions is observed for different configurations of two-frequency rf operation. The presence of a second carrier mode in the rf field results in mixed multipactor modes in which electrons take a fixed time period to complete a round trip between the two surfaces, while the time for electrons to traverse the gap in each direction is found to be different. CST simulation reveals that the space-charge effect reduces the electron growth rate and causes shrinkage of multipactor susceptibility bands.

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Multipactor suppression via asymmetric grooves in S-band waveguide

et al. 2022

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To investigate multipactor, we designed a testbed for S-band frequencies with geometries akin to the standard WR-284 waveguide geometry. Narrowing the waveguide height from WR-284 dimensions to 5.5 mm for a suitable frequency-gap product left the waveguide cutoff frequency unaffected and the RF signal propagating in the dominant TE10 mode. A coaxial magnetron provides the test input power at 2.85 GHz with a peak power output of 4 MW and a 3.5 μs pulse width, and an RF solid-state source using gallium nitride high-electron-mobility transistors delivers a pulse width of 100 μs with a test input power of 2 kW for comparison of threshold power. Local (electron multiplier tube) and global (phase/power) diagnostic methods are implemented to detect multipactor within the test setup. At power levels tested (MW) and a 5.5 mm gap, low multipactor orders (N = 1) are observed. Prior numerical studies demonstrated that structures with grooves in the waveguide broadside wall reduced multipactor susceptibility. Such grooves run along the direction of propagation to avoid continuous impedance mismatching. The efficacy of this mitigation technique was experimentally evaluated. Differences over a smooth broadside wall are noticeable, however limited.

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Two surface multipactor discharge with two-frequency rf fields and space-charge effects

Cited by 12 publications

References 58 publications

Recent advances in multipactor physics and mitigation

Recent advances in multipactor physics and mitigation

Two surface multipactor discharge with two-frequency rf fields and space-charge effects

Multipactor suppression via asymmetric grooves in S-band waveguide

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