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Scientists repurpose MRI magnet for new discoveries
Scientists repurpose MRI magnet for new discoveries
A limiting factor in modern physics experiments is the precision at which scientists can measure important values, such as the magnetic field within a detector. Scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory and their collaborators have developed a unique facility to calibrate field measurement devices and test their limits inside powerful magnetic fields.
The facility features a solenoid magnet from a former magnetic resonance imaging (MRI) scanner originally housed at a San Francisco hospital. The magnet produces a maximum field of 4 Tesla—over 400 times the strength of a refrigerator magnet. Its large opening, originally intended to hold a patient during an MRI scan, gives scientists ample space to position devices and machinery inside the magnetic field. The field produced by the magnet is also exceptionally uniform and stable, a requirement for calibrating measurement devices to the ultrahigh precision necessary for many particle and nuclear physics experiments.
"We have worked with several researchers, at Argonne and from other institutions, that need a strong magnetic field and large bore to test their research," said Peter Winter, physicist and group leader in Argonne's High Energy Physics division. "Scientists bring their devices and electronics, and we provide our magnet, expertise and infrastructure to help automate the processes and ensure the success of the tests."
The team is seeking new users to continue to broaden the facility's application portfolio.
Calibration station
A primary application of Argonne's solenoid test facility is calibrating and cross-calibrating measurement probes to achieve high precision and to add layers of consistency between similar experiments across the world.
Originally, Argonne scientists acquired the magnet to test and calibrate several probes developed by the University of Massachusetts for measuring the magnetic field in the Muon g minus 2 (Muon g-2) experiment currently taking place at DOE's Fermi National Accelerator Laboratory (Fermilab). The test facility allowed the scientists to achieve precise field measurements down to several parts per billion—like measuring the circumference of the Earth down to about two inches.
Precise measurement of the field in the experiment is crucial because the magnetic field strength is a major player in the ultimate determination of g, a property of the muon whose determination will either confirm present theories of particle physics or point to the existence of undiscovered particles.
"This facility has enabled the magnetic field team on Muon g-2 to meet strict goals on the experiment by reducing uncertainties and improving the robustness of our measurements," said David Kawall, a physicist and professor from the University of Massachusetts. "To the best of my knowledge, there are no peer facilities in the world, and having access to these tools at Argonne has been essential to the success of the magnetic field effort on Muon g-2."
Future g-2 experiments will be conducted in Japan at the Japan Proton Accelerator Complex (J-PARC) of the High Energy Accelerator Research Organization (KEK). The Japanese collaborators, led by Ken-ichi Sasaki, are using the facility to cross-calibrate their magnetic field probes with the ones used at Fermilab.
"By ensuring our probes all read the same values in the same magnetic field, we are adding certainty to the measurements coming from both g-2 experiments," said Sasaki, who is a professor at KEK and subsection leader of the cryogenic section in J-PARC.
Another muon experiment, the Muonium Spectroscopy Experiment Using Microwaves (MuSEUM), will contribute to the Japanese g-2 experiment by precisely measuring the mass ratio of the muon to the electron, a value also included in the g-2 determination.
The experiment at KEK in Japan uses very similar nuclear magnetic resonance (NMR) calibration probes as the g-2 experiment. The development of the probe for MuSEUM has been led by Toya Tanaka, a graduate student at the University of Tokyo who uses the solenoid facility to calibrate the experiment's probes. The collaboration between Japan and U.S. scientists will ensure that both g-2 experiments and the MuSEUM experiment have a consistent field measurement.
more at the link
https://phys.org/news/2020-10-scientists-repurpose-mri-magnet-discoveries.html [phys.org]
