A flexible test facility for liquid xenon detector development

TL;DR

The paper presents a versatile, immersion-cooled test facility for liquid xenon time projection chambers designed to bridge the gap between sensor-scale R&D and full-scale detectors. It details a two-stand architecture (Large and Small Systems) that uses a shared Xe supply and a Novec 7000 immersion bath to achieve exceptional temperature stability and flexible chamber geometries, enabling long-term operation for chambers up to tens of kilograms of Xe. The facility supports a broad program including large-area light/charge sensor arrays, xenon purification methods, material compatibility studies, high-voltage phenomena, and calibration systems, with robust slow controls, Python-based monitoring, and DAQ capabilities. This infrastructure accelerates development of next-generation LXe detectors by providing integrated environments for sensor development, HV research, and end-to-end subsystem testing in a remotely operable, low-background context.

Abstract

As liquid xenon time projection chambers scale to ever-larger sizes, so too do the engineering challenges they pose. We describe a large, flexible, multipurpose test facility capable of supporting the development of a number of key aspects of liquid xenon detector systems. Example applications of this facility include characterization of large-area light and charge sensor arrays, tests of xenon purification techniques and materials compatibility, and investigations into high-voltage phenomena. This facility uses an automated and remotely monitored cryo-cooling system based on immersion of the test chamber in a liquid bath rather than conductive coupling, leading to advantages in temperature and pressure stability, as well as increasing required response times in the case of cooling-power loss. Design advantages, operational procedures, and performance of the facility are described, as well as five examples of liquid xenon test chambers that use the facility.

Figures (9)

• Figure 1: Left: photo of the lab showing the two LXe test stands, the xenon storage cylinder, and the Novec 7000 supply. Right: the cryo chiller outside the lab.
• Figure 2: Piping & instrumentation diagram for the Large System. Red lines represent high-pressure tubing while purple lines represent tubing maintained at vacuum. The Small System shares the xenon supply and the cryo chiller; otherwise the diagram for the Small System is the same.
• Figure 3: Cooling and warming temperatures and timescales for an experiment in the Large System cryostat. The temperatures during the multi-day experiment are redacted from the x-axis. A visible feature in a thermocouple at the bottom of the test chamber is associated with the time when LXe starts condensing into the chamber.
• Figure 4: Stability of the test chamber temperature measured by a thermocouple mounted on its top flange. The blue line shows a rolling average computed with a window length of five on-off cooling cycles.
• Figure 5: Xenon temperature increase due to natural warming of a test chamber while installed in the Large System. The linear fit is used to estimate an 84.6 W heat leak based on an estimate of the heat capacity of dominant masses in the cryostat. The Novec 7000 mass is 230 kg, the chamber is 38 kg, the copper heat exchanger is 16 kg, and the LXe mass is 9 kg, for a total of capacity of 326 kJ/K.