The NEXT-100 Detector

The NEXT collaboration is dedicated to the study of double beta decays of $_{}^{136}$ Xe using a high-pressure gas electroluminescent time projection chamber. This advanced technology combines exceptional energy resolution ( $\le 1\%$ FWHM at the $Q_{\beta \beta }$ value of the neutrinoless double beta decay) and powerful topological event discrimination. Building on the achievements of the NEXT-White detector, the NEXT-100 detector started taking data at the Laboratorio Subterráneo de Canfranc (LSC) in May of 2024. Designed to operate with xenon gas at 13.5 bar, NEXT-100 consists of a time projection chamber where the energy and the spatial pattern of the ionising particles in the detector are precisely retrieved using two sensor planes (one with photo-multiplier tubes and the other with silicon photo-multipliers). The detector has been operating at stable conditions using argon and xenon gases at $\sim$ 4 bar and drift fields of $74\text{V}{\text{cm}}^{-1}$ and $118\text{V}{\text{cm}}^{-1}$ , respectively. Alpha decays from the $_{}^{222}$ Rn chain have been used to test and monitor the stability of the detector, showing a constant electron lifetime in the drift volume. In this paper, in addition to reporting the results of the commissioning run, we provide a detailed description of the NEXT-100 detector, describe its assembly, and present the current estimation of the radiopurity budget.