Micro-bunching for generating tunable narrow-band THz radiation at the FAST photoinjector

TL;DR

This paper explores a method to generate tunable narrow-band THz radiation using micro-bunched electron beams created by a slit-mask in a magnetic chicane at Fermilab's FAST injector, combining theory, simulation, and observation techniques.

Contribution

It introduces a simple scheme for producing tunable narrow-band THz radiation via micro-bunching in a conventional photo-injector, supported by theoretical analysis and simulation results.

Findings

Micro-bunching effectively produces narrow-band THz radiation.

Simulation results confirm the bunching and radiation characteristics.

A simple method to observe micro-bunching on a transverse screen is proposed.

Abstract

This paper presents expected THz radiation spectra emitted by micro-bunched electron beams produced using a slit-mask placed within a magnetic chicane in the FAST (Fermilab Accelerator Science and Technology) electron injector at Fermilab. Our purpose is to generate tunable narrow-band THz radiation with a simple scheme in a conventional photo-injector. Using the slit-mask in the chicane, we create a longitudinally micro-bunched beam after the chicane by transversely slicing an energy chirped electron bunch at a location with horizontal dispersion. In this paper, we discuss the theory related to the micro-bunched beam structure, the beam optics, the simulation results of the micro-bunched beam and the bunching factors. Energy radiated at THz frequencies from two sources: coherent transition radiation and from a wiggler is calculated and compared. We also discuss the results of a simple method to observe the micro-bunching on a transverse screen monitor using a skew quadrupole placed in the chicane.