# Terahertz oscilloscope for recording time information of ultrashort electron beams

## TL;DR

This paper introduces a novel Terahertz oscilloscope that uses a circularly polarized THz pulse to accurately measure the temporal profile and timing jitter of ultrashort electron beams, achieving high dynamic range and sub-5 femtosecond timing resolution.

## Contribution

The work presents a new THz-based method for electron beam timing measurement with significantly improved dynamic range and temporal resolution over existing techniques.

## Key findings

- Achieved nearly 50-fold longitudinal compression of electron beams to about 15 fs (rms).
- Demonstrated timing accuracy of 3 fs in electron beam measurements.
- Bridged the gap between optical streaking and RF deflection techniques.

## Abstract

We propose and demonstrate a Terahertz (THz) oscilloscope for recording time information of an ultrashort electron beam. By injecting a laser-driven THz pulse with circular polarization into a dielectric tube, the electron beam is swept helically such that the time information is uniformly encoded into the angular distribution that allows one to characterize both the temporal profile and timing jitter of an electron beam. The dynamic range of the measurement in such a configuration is significantly increased compared to deflection with a linearly polarized THz pulse. With this THz oscilloscope, nearly 50-fold longitudinal compression of a relativistic electron beam to about 15 fs (rms) is directly visualized with its arrival time determined with 3 fs accuracy. This technique bridges the gap between streaking of photoelectrons with optical lasers and deflection of relativistic electron beams with radio-frequency deflectors, and should have wide applications in many ultrashort electron beam based facilities.