Large-Area Scintillator Hodoscope with 50 ps Timing Resolution Onboard BESS

TL;DR

This paper presents the design and testing of a large-area scintillator hodoscope onboard BESS, achieving 50 ps timing resolution per layer and 70 ps overall, suitable for precise cosmic-ray measurements.

Contribution

It introduces a novel large-area hodoscope with high timing resolution using fine-mesh photomultiplier tubes in a magnetic field, validated by beam tests and cosmic-ray data.

Findings

Achieved 50 ps timing resolution per layer.

Confirmed the scaling law of timing resolution with photoelectron count.

Demonstrated effective operation in a 0.2 Tesla magnetic field.

Abstract

We describe the design and performance of a large-area scintillator hodoscope onboard the BESS rigidity spectrometer; an instrument with an acceptance of 0.3 m^{2}sr. The hodoscope is configured such that 10 and 12 counters are respectively situated in upper and lower layers. Each counter is viewed from its ends by 2.5 inch fine-mesh photomultiplier tubes placed in a stray magnetic field of 0.2 Tesla. Various beam-test data are presented. Use of cosmic-ray muons at ground-level confirmed 50 ps timing resolution for each layer, giving an overall time-of-flight resolution of 70 ps rms using a pure Gaussian resolution function. Comparison with previous measurements on a similar scintillator hodoscope indicates good agreement with the scaling law that timing resolution is proportional to 1/$\sqrt{N_{\rm pe}}$, where $N_{\rm pe}$ is the effective number of photoelectrons.