Electrooptical Measurements of Ultrashort 45 MeV Electron Beam Bunches

TL;DR

This paper demonstrates a noninvasive electro-optical method to measure the ultrashort duration of 45 MeV electron beam bunches, revealing linear charge dependence and ionization effects, with potential for femtosecond beam diagnostics.

Contribution

It introduces an electro-optical technique for measuring ultrashort electron bunches, including ionization effects, with implications for high-energy particle beam diagnostics.

Findings

EO modulation amplitude increases linearly with charge

EO signal decay time is long and opposite in polarity to the field signal

Detection system limits the risetime measurement to ~70ps

Abstract

We have measured the temporal duration of 45 MeV picosecond electron beam bunches using a noninvasive electro-optical (EO) technique. The amplitude of the EO modulation was found to increase linearly with electron beam charge and decrease inversely with distance from the electron beam. The risetime of the temporal signal was limited by our detection system to ~70ps. The EO signal due to ionization caused by the electrons traversing the EO crystal was also observed. It has a distinctively long decay time constant and signal polarity opposite to that due to the field induced by the electron beam. The electro-optical technique may be ideal for the measurement of bunch length of femtosecond, relativistic, high energy, charged, particle beams.