Single-Shot Ionization-Based Transverse Profile Monitor for Pulsed Electron Beams

TL;DR

This paper demonstrates a novel single-shot, non-destructive transverse profile monitor for pulsed electron beams using ionization of a low-density gas, enabling detailed diagnostics and ionization studies.

Contribution

The study introduces an experimental setup combining ionization-based detection with electrostatic magnification for real-time electron beam profiling.

Findings

Successful imaging of 7 MeV electron bunches with up to 100 pC charge

Identification of single- and double-ionization events via detector current

Analysis of ionization distribution dependence on gas density and bunch charge

Abstract

We present an experimental demonstration of a single-shot, non-destructive electron beam diagnostic based on the ionization of a low-density pulsed gas jet. In our study, 7~MeV electron bunches from a radio frequency (RF) photoinjector, carrying up to 100 pC of charge, traversed a localized distribution of nitrogen gas (N$_2$). The interaction of the electron bunches with the N$_2$ gas generated a correlated signature in the ionized particle distribution, which was spatially magnified using a series of electrostatic lenses and recorded with a micro-channel-plate detector. Various modalities, including point-to-point imaging and velocity mapping, are investigated. A temporal trace of the detector current enabled the identification of single- and double-ionization events. The characteristics of the ionization distribution, dependence on gas density, total bunch charge, and other parameters, are described. Approaches to scaling to higher electron bunch density and energy are suggested. Additionally, the instrument proves useful for comprehensive studies of the ionization process itself.