Leah McCabe - Kapiolani Community College
The ProtoDUNE experimental program is designed to test and validate the technologies and design that will be applied to the construction of the Deep Underground Neutrino Experiment (DUNE) Far Detector at the Sanford Underground Research Facility, a leading-edge, international experiment for neutrino science and proton decay studies.
The ProtoDUNE-SP cryostat will be the largest ever built, with internal dimensions of 855x790x790 cm3. The technical goal of ProtoDUNE-SP is to validate performance of all critical systems. One of the most critical systems is argon cryogenic and recirculation system that is responsible for maintaining the Liquid Ar temperature and purity. Purity of the argon ensures visibility of particle tracks in the detector and thus identifying neutrino interactions.
The challenge in the purification of the kton scale liquid argon volume in ProtoDUNE directly depends on the uniform mixing and therefore temperature of the argon. In the previous detectors such as the 35 ton LAr TPC at Fermilab, levels as low as 20 mK affected the mixing and efficiency of LAr purification.
We have been designing the temperature gradient monitor that will measure temperature in LAr with precision better than 10 mK. By measuring the temperature with such high precision, we should be able to test the argon purity. However, commercial temperature sensors come with accuracy of around 100 mK, and obtaining the temperature profile over a large height with 10 mK precision is a challenge. One way to obtain such precision is to cross-calibrate the sensors in-situ by constructing a movable system in which sensors can take each other’s places by sliding the system up and down. We have constructed such a temperature sensor array to test whether we can obtain a desired precision of 10 mK.
A set of 4 temperature sensors have been mounted on an aluminum bar and deployed in the large, 3 meters high cryostat. The array has been mounted on a spool that can be moved up and down with 10 cm steps, providing the data to cross-calibrate the sensors. Measurements have been taken in liquid argon.
Sensor cross-calibration results will be presented along with the temperature profile in the cryostat. The obtained results show that cross-calibration has been observed at 10-15 mK level. Future research includes additional measurements with improved stability of the current source used to measure the temperature, limiting small random fluctuations of the current and therefore temperature.
References: The CAPTAIN Collaboration, et al. (2013, September 01). The CAPTAIN Detector and Physics Program. Retrieved from arXiv:1309.1740.
Abi, B., et al. (2017, June 23). The Single-Phase ProtoDUNE Technical Design Report. Retrieved from arXiv:1706.07081.
Adamowski, M. et al. (2015). Development of Cryogenic Installations for large liquid argon neutrino detectors. IOP Conference Series: Materials Science and Engineering, 101, 012029. doi:10.1088/1758-899x/101/1/012029.Not Submitted
Funder Acknowledgement(s): This research has been supported by the Office of Science, in the Department of Energy.
Faculty Advisor: Radovan Milincic, firstname.lastname@example.org
Role: I am involved with the building of the testing chamber, the data collection, and analysis.