Multipactor suppression in dielectric-assist accelerating structures via diamond-like carbon coatings

TL;DR

This paper demonstrates that applying diamond-like carbon coatings to dielectric-assist accelerating cavities effectively suppresses multipactor discharges, enabling higher accelerating fields and improved performance in accelerator applications.

Contribution

The study introduces a DLC coating technique to reduce secondary electron emission, significantly enhancing the maximum achievable accelerating field in DAA cavities.

Findings

Multipactor was suppressed using DLC coatings.

Achieved over 10 MV/m in DAA cavities with RF pulses.

Enhanced cavity performance without sacrificing Q-value.

Abstract

Multipactor discharges are widely observed in the accelerator field, and their suppression has been studied to improve accelerator performance. A dielectric-assist accelerating (DAA) cavity is a standing-wave accelerating cavity that attains a Q-value of over 100,000 at room temperature by using the reflection of the dielectric layer; the DAA cavity is expected to be used with a small RF power source and high-duty operation. Thus far, the maximum accelerating field of DAA cavities has been limited to a few MV/m by the multipactor. By applying a diamond-like carbon (DLC) coating to reduce the secondary electron emission coefficient without sacrificing the Q-value of the cavity, we have demonstrated that a $6~[{\rm \mu s}]$ RF pulse can be injected into a DAA cavity with a field of more than 10~[MV/m] while suppressing the multipactor.