Description
The measurement of photon emission time spectra of liquid argon (LAr) has several challenges. Pulse shapes recorded from LAr scintillation events are often distorted by wavelength shifters, which are commonly employed since most light detectors are not sensitive to the LAr peak emission wavelength of 128 nm (in the vacuum ultraviolet, VUV region). Additionally, light detectors such as PMTs (photomultiplier tubes) and SiPMs (silicon photomultipliers) suffer from afterpulses, occurring after a detected photon and distorting the spectrum further.
The LEGEND Liquid Argon Monitoring Apparatus (LLAMA) mitigates both effects. By using VUV-sensitive SiPMs, no wavelength shifter is used in the setup. Furthermore, a low-intensity triggered scintillation-light source allows measurement in single-photon mode, thus eliminating any influence of afterpulses. The LLAMA measures the optical properties in-situ in the LEGEND-200 cryostat, shortly after the filling process has started.
High-statistics photon time emission spectra from the purified LAr are part of the presented work, together with models describing the spectral features.
The work has been supported in part by the German Federal Ministry for Education and Research (BMBF) Verbundforschung.
| Collaboration | LEGEND |
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