Alan A. Hahn

Liquefied ultrapure noble gases are typically the chosen target for neutrino and dark matter experiments. Commonly, the required grade of purity of such cryogenic liquids in terms of O₂ contamination is less than 100 ppt, which makes it necessary for the argon to circulate through adsorption columns filled, typically, with BASF Cu-0226S and Mol Sieve 4A for capturing O₂ and H₂O. Another requirement that emerged during the design of LBNF-DUNE is the purity of the Liquid Argon (LAr) in terms of N₂ concentration, as it was observed that both N₂ and O₂ contaminations can cause the reduction of the LAr scintillation light emission. In particular, a decreasing behavior in the lifetime and the relative amplitude of the slow component is relevant from concentrations of 1 ppm of N₂ and 0.1 ppm of O₂. Recently, exploratory experiments performed in the Liquid Argon Purification Cryostat (PuLArC — ∼90 L of LAr) had been successfully used to purify LAr from N₂ using an innovative solid adsorbent based on a Li-FAU Molecular Sieve. Here, we report experiments of N₂ capturing in LAr carried out at the ICEBERG Cryostat (∼3000 L of LAr) at Fermilab. For the experiments, several controlled injections of N₂ were made into the cryostat, and the impurity concentrations in the LAr (both for N₂ and O₂) were monitored using a calibrated gas analyzer during the purification process. The experimental data confirmed that the Li-FAU is capable of capturing the N₂ from the LAr. A numerical methodology based on the mass and energy balances of the system was applied to better understand the behavior of the adsorption process and to help with the scale-up of the process. A Pore Diffusion Model (PDM) coupled with parameter optimization was proposed to predict the N₂ concentration in the ICEBERG cryostat over time. The model parameters applied in this work were determined based on experimental data acquired in the PuLArC. The model was able to accurately reproduce the data from the ICEBERG, indicating that the mathematical model could be a valuable tool to design and operate the GAr/LAr system of LBNF-DUNE. It was possible to predict from simulations the necessary time to reach the required purity from an initial contamination concentration and also the number of purification cycles until solid saturation.

The luminosity of a collision region may be calculated if one understands the lattice parameters and measures the beam intensities, the transverse and longitudinal emittances, and the individual proton and antiproton beam trajectories (space and time) through the collision region. This paper explores an attempt to make this calculation using beam instrumentation during Run 1b of the Tevatron. The instrumentation used is briefly described. The calculations and their uncertainties are compared to luminosities calculated independently by the Collider Experiments (CDF and D0).

The possibility has arisen that we may have the opportunity to install a Flying Wire system in the collision region just before the roll-in of the Collider Detectors in Run II. This capability would allow us to measure the ratio of beam size at the current Flying Wire Locations (E11 and E17) to the collision region.

This paper presents the experimental status of charmonium spectroscopy and describes the technique of c̄c formation in p̄p annihilations used by the experiment E760 at Fermilab. Results from 1990 data taking are reported.