The Deep Underground Neutrino Experiment is an international collaboration to advance our understanding of the behavior of Neutrinos. The effort includes world renown laboratories and organizations such as CERN, FERMI Labs, etc. with support from thousands of scientist and technologist. The experiment intends to characterize the statistical behavior of the three different versions of neutrinos, which are sub-atomic particles which weakly interact but are constantly bombarding the earth from the sun and other sources.
The DUNE experiment will create neutrinos at CERN, directing them at a near field and far field detector. A difference between the signals from the two detectors is used to understand how neutrinos evolve over a period of time. However, neutrinos move at a high velocity and therefore the far detector must be physically located far away. And the neutrino beams widens out as it moves away from the source, therefore the far detector must grow in size the further it is from the source. While the neutrinos are created at FERMI labs in Illinois, the far detector is located at the bottom of a disused gold mine in South Dakota approximately 800 miles away. The two detectors under construction in South Dakota are each the volume of 5 Olympic swimming pools.
Science and specifically large, logistically complex experiments like DUNE are built upon iterations of trials and scaled prototypes. The Physical Sciences Laboratory has a long history and much experience in the creation of other time-projection chamber (TPC) systems, such as DAYA Bay, Lux Zepplin, and the protoDUNE demonstrator. PSL has contributed key expertise in construction, mechanical design, electronics and circuit board design to bring the DUNE concept to a fully realized system. Additionally, PSL has accumulated years of experience while refining the design of the detectors, conducting qualification tests and manufacturing prototypes up to 1:1 scale.
APA Design and Testing
The DUNE Far Detector is actually a pair of large systems, one each for measuring the horizontal and vertical drift of the neutrino beam. PSL worked through several design iterations to develop the final version of the Vertical Drift detector elements, called the Anode Plane Assembly (APA). The APAs are the smallest unit of assembly and the Far Detector is uses 150 APAs to create the final system. The APAs transform a relatively simple physics concept, the creation of an uniform electric field by opposing anode and cathode, into a highly sensitive measurement device that can sense individual electrons that signal when a neutrino passes through the detector. Developing a scientific device that can be produced in mass, built a locations around the globe, and then withstand the bumpy travel to South Dakota requires a significant amount of planning and attention to detail.
What makes the APA so sensitive, both to electrons and to bumps on the road, is the 15 miles of thin copper wire that are wrapped around each APA frame and create a mesh of 3 distinct layers. The layers of wire are either electrified to create the electric field or monitored to catch drifting electrons. PSL created the mechanical design elements of the APA, such as the frame or the lifting hardware, but also tested and selected the special copper wire being used. A particular wire test to characterize tension and ageing was started in 2016 and been ongoing to present day
APA Circuit Board Design and Production
APA Winder
Each APA requires 15 miles of thin copper wire to create the field and sensing layers. The early prototypes were wound by hand at PSL by some incredibly dedicated technicians, but not even the competent PSL staff could wind 150 APAs to the exacting standards for DUNE in a reasonable amount of time. Instead PSL developed a robotic winding machine that could accurately place and tension each individual wire, though it still requires a crew of proficient technicians to attach all of the circuit boards and create the solder connections. The APA winder slowly shuttles a bobbin of wire from one end of the APA to the other while maintaining accurate location and wire tension. Approximately 50 of these winders have been built and are operating at collaborative institutions to create the 150 APAs needed for the Far Detector.
Quality Assurance
Quality and cleanliness is of utmost importance for the DUNE system. All parts must work as intended when they’re finally submerged in sub-freezing temperatures of liquid Argon. Parts will pass through physical inspection for form and fit. Assemblies are checked for completeness and functionality. Active components, such as the APA circuit boards produced at PSL, are functionally tested by thermo cycling and running through electrical testing. PSL staff have diverse backgrounds and expertise in Quality Assurance and production methodologies used in industries such as electronics, control circuitry, aerospace, defense, heavy equipment, and of course medical/physics research. Therefore PSL uses a wide range of quality control and inspection tools; gages and jigs, CMM inspection tools, load and tension testing, custom electrical test stands, and specialized Keyence vision-based system for inspecting circuit boards.
Integration Hardware
The DUNE system is built from many passive components that are necessary to lift, hold, stabilize or position the APAs in exactly the correct location. This passive hardware is engineered and manufactured to the standards expected of a world-class physics experiment. PSL has developed the production plan and pipeline to deliver parts that are reliable.
Additional Media
Read more about the project through the articles below, featuring additional information from the University of Wisconsin and Fermilab, along with a downloadable project datasheet.
PSL & DUNE Collaboration Members More DUNE Information
Watch the video by Fermilab below to learn more!