Suppression of Multipactor Discharge on a Dielectric With a Beat Wave

An electromagnetic particle-in-cell (PIC) simulation technique is used to analyze multipactor discharge on a dielectric with a beat wave composed of multiple high-power microwaves (HPMs) with similar frequencies. Unlike the single-frequency HPM, the strength of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {n}}$ </tex-math></inline-formula> of the multipactor with a beat wave fluctuates greatly with time, resulting in the root-mean-square value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {n}}$ </tex-math></inline-formula> (strongly related to the average deposition power) being significantly greater than the absolute value of the arithmetic mean of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {n}}$ </tex-math></inline-formula> (the traditional indicator of the multipactor strength), where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {n}}$ </tex-math></inline-formula> is the electric field due to the deposited charges induced by multipactor. In this article, the influence of double-frequency and triple-frequency beat waves on multipactor is studied from the perspective of the root-mean-square value and absolute value of the arithmetic mean of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {n}}$ </tex-math></inline-formula>. The results show that the strong multipactor with a beat wave is unaffected by the spectra of the beat wave and the beat wave cannot inhibit the strong multipactor strength in contrast to a single-frequency HPM with the same average microwave power while the inhibition effect of a beat wave on a moderated multipactor is obvious. Further analysis shows that the suppression effect of a beat wave on a moderated multipactor is greatest when both the frequencies and phases of the beat wave are arranged in an arithmetic progression and the moderated multipactor can also be suppressed substantially when the amplitudes of the beat wave deviate slightly from the condition of equal amplitude.