Development of the Millimeter-wave Camera with High Time Resolution for Observation of the Vortex Beam

Recently, it has been shown that a charged particle with spiral motion creates a radiation field with vortex property [1]. Since an electron in the magnetic field confinement fusion plasma has a spiral motion (electron cyclotron motion), the electron cyclotron emission (ECE) should have a vortex property. In order to demonstrate the vortex property, we will investigate the ECE from the gyro phase control electron. In this research, radiation pattern measurement of less than millisecond is required, so we are developing millimeter wave camera with high temporal resolution.

The designed camera consists of an array of horn antennas followed by waveguides and microstrip lines for directing the millimeter wave power to an array of high time resolution detectors. Optimization of the coupling from the waveguide to the microstrip line and the detector is performed using the 3D finite difference time domain method (FDTD method). The details of the optimization of the camera design and resultant experimental characteristic of this camera will be discussed.

[1] M. Katoh, et al., Phys. Rev. Lett. 118, 094801 (2017).