Energy Measurements by Means of Transition Radiation in novel Linacs

TL;DR

This paper explores the use of Optical Transition Radiation (OTR) screens for energy measurement in advanced linear accelerators, analyzing sensitivity, resolution, and upgrades needed for effective single-shot and distributed energy diagnostics.

Contribution

It introduces a method to perform energy measurements using OTR angular distribution in novel linacs, including sensitivity analysis and diagnostic upgrades based on preliminary experimental data.

Findings

OTR angular distribution depends on beam energy and divergence.

Preliminary measurements at 100 MeV demonstrate measurement feasibility.

Upgrades are necessary for improved resolution and single-shot energy diagnostics.

Abstract

Advanced linear accelerator design may use Optical Transition Radiation (OTR) screens to measure beam spot size; for instance, such screens are foreseen in plasma based accelerators (EuPRAXIA@SPARC_LAB) or Compton machines (Gamma Beam Source@ELI-NP). Optical Transition Radiation angular distribution strongly depends on beam energy. Since OTR screens are typically placed in several positions along the Linac to monitor the beam envelope, one may perform a distributed energy measurement along the machine. Furthermore, a single shot energy measurement can be useful in plasma accelerators to measure shot to shot energy variations after the plasma interaction. Preliminary measurements of OTR angular distribution of about 100 MeV electrons have been performed at the SPARC_LAB facility. In this paper, we discuss the sensitivity of this measurement to beam divergence and others parameters, as well as the resolution required and the needed upgrades of conventional OTR diagnostics, using as an example the data collected at SPARC_LAB.