Electron beam charge diagnostics for laser plasma accelerators

R Donahue,W Byrne,K Nakamura,A Smith,A J Gonsalves,C Lin,W P Leemans,D Rodgers

doi:10.1103/physrevstab.14.062801

Abstract

A comprehensive study of charge diagnostics is conducted to verify their validity for measuring electron beams produced by laser plasma accelerators (LPAs). First, a scintillating screen (Lanex) was extensively studied using subnanosecond electron beams from the Advanced Light Source booster synchrotron, at the Lawrence Berkeley National Laboratory. The Lanex was cross calibrated with an integrating current transformer (ICT) for up to the electron energy of 1.5 GeV, and the linear response of the screen was confirmed for charge density and intensity up to $160\text{ }\text{ }\mathrm{pC}/{\mathrm{mm}}^{2}$ and $0.4\text{ }\text{ }\mathrm{pC}/(\mathrm{ps}\text{ }\text{ }{\mathrm{mm}}^{2})$, respectively. After the radio-frequency accelerator based cross calibration, a series of measurements was conducted using electron beams from an LPA. Cross calibrations were carried out using an activation-based measurement that is immune to electromagnetic pulse noise, ICT, and Lanex. The diagnostics agreed within $\ifmmode\pm\else\textpm\fi{}8%$, showing that they all can provide accurate charge measurements for LPAs.

Highlights

Laser plasma accelerators (LPAs) [1] have shown remarkable progress over the past decade, driven in part by advances in laser technology
Despite all of the favorable features of the integrating current transformer (ICT) for LPA, its use for LPA produced e-beams has been questioned in recent studies. It was reported in Ref. [26] that the ICT overestimated the e-beam charge by more than an order of magnitude compared to the measurement based on the radiofrequency accelerators (RFAs)-calibrated scintillating screen, and the source of discrepancy was attributed to the electromagnetic pulse (EMP) from the laser-plasma interaction
We have experimentally studied the sensitivity of Lanex Fast scintillating screen (Kodak, Rochester, NY, United States) using e-beams provided by a booster synchrotron at the Advanced Light Source (ALS), Lawrence Berkeley National Laboratory (LBNL)

Summary

INTRODUCTION

Laser plasma accelerators (LPAs) [1] have shown remarkable progress over the past decade, driven in part by advances in laser technology. The range of applicable charge density was extensively studied with 40 MeV e-beams from an RFA [31] using an ICT and Faraday cup measurements for reference. [26] that the ICT overestimated the e-beam charge by more than an order of magnitude compared to the measurement based on the RFA-calibrated scintillating screen, and the source of discrepancy was attributed to the electromagnetic pulse (EMP) from the laser-plasma interaction. Another cross calibration using LPA produced e-beams was done in Ref.

Experimental setup

Results

CHARGE DIAGNOSTICS CROSS CALIBRATIONS WITH LASER PLASMA

Lanex-activation cross calibration

Lanex-ICT cross calibration

Findings

SUMMARY AND CONCLUSIONS