Measurement of the LCLS-II dark current using the LDMX Trigger Scintillator Prototype

TL;DR

This paper reports on measuring the dark current in the LCLS-II beamline using a prototype scintillator, which is crucial for the LDMX dark matter search requiring precise low-current beam characterization.

Contribution

It presents the first measurement of dark current in the LCLS-II transfer line using a specialized scintillator prototype for the LDMX experiment.

Findings

Dark current levels were quantified in the LCLS-II transfer line.

The scintillator prototype effectively detected low-current beam signals.

Results inform the optimization of low-current beam operation for dark matter searches.

Abstract

The Light Dark Matter eXperiment (LDMX) is a proposed fixed-target missing momentum search for sub-GeV thermal relic dark matter. LDMX aims to probe thermal dark matter targets with 1016 electrons on target. Such an approach requires a high-repetition rate, low-current beam, with an average of one electron on target per event. These requirements are well-suited to the DArk Sector Experiments at LCLS-II (DASEL) facility, which will take advantage of the unused RF buckets between LCLS-II bunches to produce a well-defined low-current beam with a 26.9 ns bunch spacing. This document describes the results of a measurement of dark current in the Sector 30 transfer line (S30XL) of the LCLS-II beam, using a prototype of the LDMX trigger scintillator (TS) subsystem.