A WLS Reﬂector, made of copper-tetratex foil, surrounds the LAr instrumenta6on and the HPGe detector strings: Eur.Phys.J.C 82 (2022) 5, 442 CIEMAT Leibniz Inst. for Polymer Research South Dakota Mines Univ. of North Carolina at Chapel Hill Comenius Univ. Los Alamos Natl. Lab. Tech. Univ. Dresden Univ. of Padova and INFN Czech Tech. Univ. Prague and IEAP Max Planck Inst. for Nucl. Phy. Tech. Univ. Munich Univ. of Regina Daresbury Lab. Max Planck Inst. for Physics Tennessee Tech. Univ. Univ. of South Carolina Duke Univ. and TUNL Natl. Res. Center Kurchatov Inst. Univ. of California and LBNL Univ. of South Dakota Gran Sasso Science Inst. Natl. Res. Nucl. Univ. MEPhI Univ. College London Univ. of Tennessee Indiana Univ. Bloomington North Carolina State Univ. Univ. of L'Aquila and INFN Univ. of Texas at Austin Inst. Nucl. Res. Rus. Acad. Sci. Oak Ridge Natl. Lab. Univ. of Cagliari and INFN Univ. of Tuebingen Jagiellonian Univ. Polytech. Univ. of Milan Univ. of California San Diego Univ. of Warwick Joint Inst. for Nucl. Res. Princeton Univ. Univ. of Houston Univ. of Washington and CENPA Joint Res. Centre Geel Queen's Univ. Univ. of Liverpool Univ. of Zurich Lab. Naz. Gran Sasso Roma Tre Univ. and INFN Univ. of Milan and INFN Williams College Lancaster Univ. Simon Fraser Univ. Univ. of Milano Bicocca and INFN Leibniz Inst. for Crystal Growth SNOLAB Univ. of New Mexico 40K 4- 1.15 Gyr 0+ Qβ = 1.5 MeV Stable 89% 40Ca EC 11% 1461 keV 11% 0+ 40Ar Stable zoom 42Ar 0+ 32.9 yr Qβ = 599 keV 2- 42K 12.355 h Qβ = 3.5 MeV 0+ 2+ 0+ 82% 18% 0.34% 42Ca 313 keV 1525 keV Stable 2. LAr Scin+lla+on o 1 μm TetraPhenyl Butadiene (TPB) surface coating by evaporation; o 58 SiPM channels: 58 x 9 Ketek PMT33100T 3x3 mm2 SiPMs. 1. LAr Instrumenta+on Setup The LAr scintillation light emission is superposition of two excimer states (Ar! ∗), which both decay producing 128 nm Vacuum-Ultra-Violet (VUV) light 5. Performance in LEGEND-200 LEGEND-200 experiment for neutrinoless double beta decay search, using HPGe detectors immersed in LAr cryostat To op6mize the LAr instrumenta6on performance the LAr was puriﬁed from N2, O2 and H2O. PoS PANIC2021 (2022) 102 q The LAr quality is monitored con6nuously by the LEGEND LAr Monitoring Apparatus (LLAMA). EPJ Web Conf. 253 (2021) 11014 Liquid Argon Instrumenta2on for Background Suppression in LEGEND-200 Experiment 1500 mm Gabriela Araujo1, Laura Baudis1, Nina Burlac2,*, Valerio D’Andrea2, Rosanna Deckert3, Maria Fomina4, Konstan6n Gusev3,4, Patrick Krause3, Alexey Lubashevskiy4, Francesco Paissan2, Laszlo Papp3, Nadya Rumyantseva3,4, Giuseppe Salamanna2, Stefan Schönert3, Mario Schwarz3, Egor Shevchik4, Diego Tagnani2, Daniya Zinatulina4 for the LEGEND collaboraVon 1Universität Zürich, Switzerland 2Rome Tre University and INFN Roma Tre, Italy *currently at Laboratori Nazionali del Gran Sasso (LNGS) of INFN, Italy 3Technische Universität München, Germany 4Joint InsHtute for Nuclear Research, Dubna, Russia q TPB shi]s the VUV light to blue (420 nm); q WLS ﬁbers shi] the blue light into green (490 nm); q The green light is read out by SiPMS (440 nm). 𝜏fast= 30 ns q Event Topology Classiﬁer (ETC) parameter o ra6o of the light emided in the single component to the total light intensity of an event (N = Ns+Nt): ETC = 𝐍𝐬 𝐍 𝜏slow= 8 μs RiseHme 48 ns q The 9 SiPMs are read out in parallel and diﬀerenVally by the front-end electronics. q Overall noise level of 250 μV (peak-to-peak) and RMS = 58 μV (mean value). JINST 18 (2023) 09 q Charge and Vme reconstrucVon performed with two independent methods based on rising edge of the trace and diﬀering in the signal ﬁltering: o HyperCurrent algorithm – a Gaussian ﬁlter is applied to smooth the electronic noise: 95% charge reconstrucVon eﬃciency. o DPLMS ﬁlter-based algorithm Eur.Phys.J.C 83 (2023) 2 – an op6mum ﬁlter is synthe6zed and applied to SiPMs traces: 96% charge reconstrucVon eﬃciency. LAr veto condi1on: q Test staVsVc-based classiﬁer that categorizes events as true (TC) or random co