Temperature Dependence of the Time Resolution in a SiPM-Readout Plastic Scintillator for Cosmic-Ray Applications

TL;DR

This work investigates how temperature affects the time resolution of a SiPM‑readout plastic scintillator TOF detector intended for cosmic‑ray applications. Using a BC418 bar read out by four Onsemi MICROFC‑30050‑SMT SiPMs, the study combines controlled cooling and source‑position tests with a differential preamplifier and CFD timing to quantify $V_{bd}$ and timing performance over $-20$ to $20$ °C. The main findings show a linear $V_{bd}(T)$ with a coefficient around $22.0$ mV/°C and a minimum per‑detector time resolution near $V_{ov}=3$ V of about $157.9 \,\pm\, 1.3$ ps, with the overall timing remaining stable (∼161 ps) across temperatures and positions. These results demonstrate the feasibility of compact, SiPM‑based timing layers for future balloon‑ and satellite‑borne cosmic‑ray experiments, where reliable picosecond timing must be maintained under thermal variations.

Abstract

Balloon- and space-borne cosmic-ray experiments employ plastic scintillators read out by silicon photomultipliers (SiPMs) to achieve picosecond-level time resolutions for triggering and particle identification. The performance of these systems can be affected by temperature variations encountered in flight. In this work, a time-of-flight (TOF) prototype consisting of a BC418 plastic scintillator bar coupled to Onsemi MICROFC-30050 SiPMs was constructed and tested under a controlled thermal environment between -20 and 20$^{\circ}$C. Electrons from a $^{90}\text{Sr}$ source were used as a beam, and a dedicated differential preamplifier and coincidence triggering were implemented to study the detector response. A minimum time resolution of 160ps was achieved at an overvoltage of 3V, remaining stable across the tested temperature range and uniform along the scintillator bar.

Figures (8)

• Figure 1: (a) Diagram of the different experimental setups used in this work. (b) Photograph of the cooling system used in Setup 1. See text for details.
• Figure 2: Diagram of the differential preamplification used in this work.
• Figure 3: The left plot shows measured current vs reverse-bias voltage at each temperature for Onsemi MICROFC-30050-SMT SiPMs. The right plot illustrates the linear relationship between breakdown voltage and temperature for the same SiPM.
• Figure 4: On the left, representative waveforms of every SiPM signal with the linear fit to the leading edge and threshold levels at 10%, 20%, 50%, and 90% are shown. On the right, the measured rise time distributions are shown with their corresponding Gaussian fits.
• Figure 5: Time difference distribution between two SiPMs measured with Setup 2, and using a CFD at 20%.