Characterization of FBK NUV-HD-Cryo SiPMs near LHe temperature

TL;DR

This work demonstrates that FBK NUV-HD-Cryo SiPMs function reliably near liquid helium temperatures, achieving a dark count rate around 0.01 Hz/mm^2 and a PDE above 40% when overvoltage exceeds 10 V. Using a photocurrent PDE approach calibrated with 405 nm and 530 nm light, the study maps PDE, gain, AP, and CT at 7 K and 10 K, revealing cryogenic-specific behavior such as potential nonlinearity in gain versus OV and low noise operation at these temperatures. A COMSOL temperature analysis identifies and mitigates a temperature discrepancy caused by cryogenic leakage paths, enabling a 7 K operation that aligns with simulations. Overall, the results indicate that FBK NUV-HD-Cryo SiPMs are strong candidates for photosensing in liquid helium detectors and ALETHEIA TPCs, with manageable AP and CT and robust PDE at practical OV levels.

Abstract

Five FBK ``NUV-HD-Cryo'' SiPMs have been characterized at 7 K and 10 K, with 405 nm and 530 nm LED light, respectively. The dark count rate (DCR) was measured to be $\sim$ 1 Hz for the $\sim$ 100 mm$^2$-size SiPMs, or 0.01 Hz/mm$^2$, which is $\sim$ 7 orders lower than the DCR at room temperature (RT). Given the very low DCR at these cryogenic temperatures, we measured the SiPMs' I-V curves with such a method: illuminated the SiPMs with weak light, which differs from the conventional measurements at RT. Then, we measured the photo-detection efficiency (PDE), after-pulse (AP), and cross-talk (CT) with a bias voltage ranging from overvoltage (OV) 5 to 11 V. At the OV interval (5 to 11 V), the PDE was between 20\% - 45\%, and the AP and CT were both between $\sim$ 5\% and $\sim$ 20\%. With an OV higher than 10 V, the PDE would be $\ge$ 40\%, and the AP and CT are $\sim$ 20\%. Combining all of the measurements, we are confident that the SiPMs can be equipped as the photosensors on liquid helium detectors, including but not limited to the time projection chambers, which we have proposed in hunting for low-mass dark matter directly and beyond.

Figures (18)

• Figure 1: The schematic drawing of the test setup. The LED, the photodiode, and the SiPMs are mounted on the integrating sphere's surfaces, 90 degrees from each other. These parts are all at 10 K temperature. The 70 cm SMA cable conveys signals from cryogenic temperature to RT environment. Depending on the measurements, a preamplifier and a 8 GHz bandwidth, 25 GSa/s sample rate oscilloscope, or a Keithley 6485 electrometer will be connected for data-taking.
• Figure 2: The picture shows the integrating sphere mounted on the cooling plate (inside the G-M cryocooler). The photodiode, the LED, and the SiPMs are also visible in the image.
• Figure 3: The schematic drawing shows the PDE test setup. The inner surface of the integrating sphere is PTFE (not visible in the drawing). The LED simultaneously illuminates the to-be-calibrated SiPMs and the calibrated photodiode. Please refer to the main text for more information.
• Figure 4: The responsivity of the photodiode we used for PDE measurements. The black curve is copied from the photodiode's datasheet. The red curve represents the data points measured at NIM at RT. The two stars were the photodiode's characterized responsivity when they were cooled to 6 K and illuminated with 405 nm and 530 nm light, respectively.
• Figure 5: The typical I-V curve of an FBK NUV-HD-Cryo SiPMs measured at $\sim$ 10 K, with and without illumination. The green dots were measured with weak pulsed light from a 405 nm LED, which a DG535 drove. The blue ones were measured in the dark.