First demonstration of coherent Cherenkov radiation matched to circular plane wave

Norihiro Sei,Toshiharu Takahashi

doi:10.1038/s41598-017-17822-z

Abstract

We observed coherent Cherenkov radiation matched to a circular plane wave (CCR-MCP) for the first time using a hollow conical dielectric made of a high-density polyethylene. The refractive index and the absorption coefficient of the dielectric were evaluated to be 1.537 ± 0.004 and 0.006 ± 0.028 by measuring the pulse formed by the interference between the CCR-MCP and the coherent diffraction radiation. These values were consistent with the values shown in a reference for the high-density polyethylene. In accordance with the theory of the Cherenkov radiation, the spectrum of the CCR-MCP shifted towards higher wavenumbers compared to that of the coherent diffraction radiation. The intensity of the CCR-MCP beam was proportional to the height of the hollow conical dielectric and was 3 times the intensity of the coherent diffraction radiation. The CCR-MCP technique can produce broadband terahertz-wave sources with unprecedented power at compact accelerator facilities.

Highlights

In the CCR-MCP experiments, a hollow conical dielectric was inserted at a position of 0.4 m in front of an aluminum-foil mirror, which was used in ordinary CTR experiments at the KURRI-LINAC17–20
The hollow conical dielectric was made of a high-density polyethylene (HDPE) with the inner diameter of 10 mm
We observed the CCR-MCP for the first time using the KURRI-LINAC in Kyoto University

Summary

Introduction

This value was in good agreement with the refractive index of the HDPE provided in ref.[21] the width of the satellite pulse did not depend on Lh, the height of the satellite pulse increased as the Lh increased. The intensity of the CCR-MCP can be evaluated by calculating the difference from the relative intensity of the background radiation. According to the theory of the CCR-MCP, the intensity is related to Lh by the following equation[14]: P

Methods

Results

Conclusion