Ionizing Liquid Argon with High Intensity Lasers at ProtoDUNE
"High-intensity UV laser calibrates ProtoDUNE, paving the way for future analyses in the DUNE experiment detectors. "
The DUNE (Deep Underground Neutrino Experiment) is a major international physics project in which a neutrino beam will be sent from Fermilab in Illinois to a set of massive liquid argon particle detectors located deep underground at the Sanford Underground Research Facility in South Dakota, 1285 kilometers away. It will study, among other things, neutrino oscillations in order to determine neutrino mass hierarchy and look for evidence of neutrino-antineutrino asymmetry.
Two prototypes of liquid argon far detectors are currently being tested at CERN. They record signals from cosmic rays and CERN charged particle beams, but also from other sources that will be used to calibrate the final large detectors underground. One of these is the laser calibration system jointly developed and built by scientists and engineers from LIP and Los Alamos National Laboratory (LANL), USA.
General view of the neutrino platform, with ProtoDUNE-HD in the foreground and ProtoDUNE-VD in the background
The system is based on very intense UV laser pulses that are injected in the detector, via inverted periscopes, ionizing the liquid along straight lines, which allows the scientists to identify and correct the geometric distortions caused by electric field non-uniformity and improve overall precision in incoming particle registration.
Periscope P2 detail of the double rotation system designed and built at LIP
Periscope P3 just installed
The technology of using a UV laser to produce straight tracks in large liquid argon detectors was pioneered by the MicroBooNE experiment. While the DUNE laser calibration was inspired by their design, it had to be adapted to calibrate the DUNE far detector which has a much larger scale than MicroBooNE. This work, made in close collaboration between LIP and LANL, was led by José Maneira, while a large part of the mechanical design was done by Rui Alves. Afterwards, the parts of the mechanical system were manufactured at Coimbra mechanical workshop under the supervision of Luís Lopes. The process of scanning the detector with a laser beam is coordinated by an electronics board (CIB - calibration interface board) developed by Nuno Barros and directed by a GNavigator software written by Francisco Neves. Precision periscope movement was ensured by a motor control and monitoring system designed by Vladimir Solovov.
Recently, a successful test of the laser calibration process was carried out with the system producing a series of laser tracks through the detector volume recorded by the ProtoDUNE data acquisition system. The test demonstrated coordinated work of the CIB board and GNavigator software together with the data acquisition and slow control systems of the detector.
Images of the laser traces obtained with the ProtoDUNE-HD detector. On the left superimposed on cosmic muon traces, on the right after image filtering
This success would be impossible without the presence of the LIP crew on-site. Wallison Campanelli has spent six months at CERN helping with installation, commissioning and operations while the detector was filled with liquid argon and the laser calibration infrastructure put in place. Other DUNE team members, including José Maneira, Vladimir Solovov, Nuno Barros and Rui Alves were present on-site at critical moments to help with hardware installation and tests.
Wallison inside ProtoDUNE's criostat
Vladimir entering the detetor
Inserting the P3 periscope into the flanges, with José, Vladimir and David
Wallison assembling the Laser protection cover
The data collected will now be used to calibrate the ProtoDUNE and prepare the analyses for the future use in the much larger DUNE detectors.