ATLAS Monitored Drift Tube Chambers in E = 11 MeV Neutron Background

TL;DR

This study assesses how 11 MeV neutron background affects the performance of ATLAS muon drift tubes, finding minimal impact on resolution and track reconstruction even at high neutron flux densities.

Contribution

It provides the first detailed measurement of neutron background effects on ATLAS muon drift tubes at 11 MeV, demonstrating their robustness against neutron-induced disturbances.

Findings

Neutron sensitivity of the chamber is 4×10⁻⁴.

Minimal impact on single tube resolution under neutron irradiation.

Little influence on muon track reconstruction accuracy.

Abstract

The influence of fast neutrons on the occupancy and the single tube resolution of ATLAS muon drift detectors was investigated by exposing a chamber built out of 3 layers of 3 short standard drift tubes to neutron flux-densities of up to 16 kHz/cm2 at a neutron energy of E=11 MeV. Pulse shape capable NE213 scintillaton detectors and a calibrated BF3 neutron detector provided monitoring of the neutron flux-density and energy. The sensitivity of the drift chamber to the neutrons was measured to be 4*10-4 by comparing data sets with and without neutron background. For the investigation of tracks of cosmic muons two silicon-strip detectors above and underneath the chamber allow to compare measured drift-radii with reference tracks. Alternatively, the single tube resolution was determined using the triple-sum method. The comparison between data with and without neutron irradiation shows only a marginal effect on the resolution and little influence on the muon track reconstruction.