Speakers
Description
The next generation of liquid argon time projection chambers, such as those in the Deep Underground Neutrino Experiment (DUNE), requires highly pure liquid argon for optimal detector performance. Even trace amounts of electronegative contaminants, especially oxygen, capture drifting electrons and reduce signal amplitude. This contamination compromises spatial resolution. Achieving and maintaining ultra-high purity during filling and steady-state operation of large cryostats is therefore a critical engineering challenge. In this work, we present a physics-based adsorption model to describe and predict O2 removal in large liquid argon cryostats. The model is based on pore diffusion. It incorporates both external film resistance to mass transfer and intraparticle diffusion within the porous adsorbent. The governing equations include a macroscopic mass balance for the intra- and extraparticle bulk phases. This is coupled with an adsorption model within spherical particles. To close the model, the Langmuir isotherm was adopted to describe the equilibrium between the liquid and solid phases.
This model accurately captures oxygen-adsorbent interactions at cryogenic conditions. Model parameters were determined by regressing experimental data from the PuLArC facility at IFGW -- UNICAMP (Brazil). This study used a Cu-BASF adsorbent designed for oxygen removal. Transient concentration measurements within the cryostat during purification cycles were fitted using nonlinear optimization. This estimated effective diffusivity and adsorption parameters. With these estimates, the calibrated model closely matches observed purification dynamics. The model was extended to simulate large-scale systems, including the ProtoDUNE cryostat at CERN (Switzerland). The focus was on purification during the filling stage. These simulations predict reductions in oxygen concentration and the time to achieve detector-grade purity. They can accurately predict the process behavior based on experimental data. This predictive capability enables scaling from laboratory and pilot-scale experiments to kiloton-scale detectors. It provides a framework to optimize purification strategies, size filtration units, and reduce commissioning time. This approach supports efforts to ensure long electron lifetimes and stable detector operation in next-generation neutrino experiments. It directly links experimentally calibrated adsorption physics to full-scale system performance. This ensures that large detectors operate reliably in neutrino physics.