Фермилаб: Исследования высоких энергий и нейтринной физики в США

High energy particle physics laboratory in Illinois, US

Fermi National Accelerator Laboratory (Fermilab), located in Batavia, Illinois, near Chicago, is a United States Department of Energy national laboratory specializing in high energy particle physics. Fermilab's Main Injector, two miles (3.3 km) in circumference, is the laboratory's most powerful particle accelerator. The accelerator complex that feeds the Main Injector is under upgrade, and construction of the first building for the new PIP II linear accelerator began in 2020. Until 2011, Fermilab was the home of the 6.28 km (3.90 mi) circumference Tevatron accelerator. The ring shaped tunnels of the Tevatron and the Main Injector are visible from the air and by satellite. Fermilab aims to become a world center in neutrino physics. It is the host of the multi billion dollar Deep Underground Neutrino Experiment (DUNE) now under construction. The project has suffered delays and, in 2022, the journals Science and Scientific American each published articles describing the project as "troubled". Ongoing neutrino experiments are ICARUS (Imaging Cosmic and Rare Underground Signals) and NOνA (NuMI Off Axis νe Appearance). Completed neutrino experiments include MINOS (Main Injector Neutrino Oscillation Search), MINOS+, MiniBooNE and SciBooNE (SciBar Booster Neutrino Experiment) and MicroBooNE (Micro Booster Neutrino Experiment). Since 2007, Fermilab has been operated by the Fermi Research Alliance (FRA), a joint venture of the University of Chicago, and the Universities Research Association (URA); although in 2023, the Department of Energy (DOE) opened bidding for a new contractor due to concerns about the FRA performance. Fermilab is a part of the Illinois Technology and Research Corridor. On site experiments outside of the neutrino program include the SeaQuest fixed target experiment and Muon g 2. Fermilab continues to participate in the work at the Large Hadron Collider (LHC); it serves as a Tier 1 site in the Worldwide LHC Computing Grid. Fermilab also pursues research in quantum information science. It founded the Fermilab Quantum Institute in 2019. Since 2020, it also is home to the SQMS (Superconducting Quantum Materials and Systems) Center. Asteroid 11998 Fermilab is named in honor of the laboratory.

Prior to the startup in 2008 of the Large Hadron Collider (LHC) near Geneva, Switzerland, the Tevatron was the most powerful particle accelerator in the world, accelerating protons and antiprotons to energies of 980 GeV, and producing proton antiproton collisions with energies of up to 1.96 TeV, the first accelerator to reach one "tera electron volt" energy. At 3.9 mile (6 km), it was the world's fourth largest particle accelerator in circumference. One of its most important achievements was the 1995 discovery of the top quark, announced by research teams using the Tevatron's CDF and DØ detectors. It was shut down in 2011.

Since 2013, the first stage in the acceleration process (pre accelerator injector) in the Fermilab chain of accelerators takes place in two ion sources which ionize hydrogen gas. The gas is introduced into a container lined with molybdenum electrodes, each a matchbox sized, oval shaped cathode and a surrounding anode, separated by 1 mm and held in place by glass ceramic insulators. A magnetron generates a plasma to form the ions near the metal surface. The ions are accelerated by the source to 35 keV and matched by low energy beam transport (LEBT) into the radio frequency quadrupole (RFQ) which applies a 750 keV electrostatic field giving the ions their second acceleration. At the exit of RFQ, the beam is matched by medium energy beam transport (MEBT) into the entrance of the linear accelerator (linac). The next stage of acceleration is linear particle accelerator (linac). This stage consists of two segments. The first segment has five drift tube cavities, operating at 201 MHz. The second stage has seven side coupled cavities, operating at 805 MHz. At the end of linac, the particles are accelerated to 400 MeV, or about 70% of the speed of light. Immediately before entering the next accelerator, the H− ions pass through a carbon foil, becoming H+ ions (protons). The resulting protons then enter the booster ring, a circumference circular accelerator whose magnets bend beams of protons around a circular path. The protons travel around the Booster about 20,000 times in 33 milliseconds, adding energy with each revolution until they leave the Booster accelerated to 8 GeV. The final acceleration is applied by the Main Injector [circumference ], which is the smaller of the two rings in the last picture below (foreground). Completed in 1999, it has become Fermilab's "particle switchyard" in that it can route protons to any of the experiments installed along the beam lines after accelerating them to 120 GeV. Until 2011, the Main Injector provided protons to the antiproton ring [circumference ] and the Tevatron for further acceleration but now provides the last push before the particles reach the beam line experiments.

Fermilab dismantled the CDF (Collider Detector at Fermilab) experiment to make the space available for IARC (Illinois Accelerator Research Center). Fermilab physicists continue to play a key role in the world wide collider program. The LHC Physics Center (LPC) at Fermilab is a regional center of the Compact Muon Solenoid Collaboration (the experiment is housed at CERN). The LPC offers a vibrant community of CMS scientists from the US and plays a major role in the CMS detector commissioning, and in the design and development of the detector upgrade. Fermilab is the host laboratory for USCMS, which includes researchers from 50 U. S. universities including 715 students. Fermilab hosts the largest CMS Tier 1 computing center, handling approximately 40% of global CMS Tier 1 computing requests. On February 9, 2022, Fermilab's Patricia McBride (physicist) was elected spokesperson of the CMS collaboration. During this time frame, the laboratory also established a new program in research in cutting edge information science, including the development of quantum teleportation technology for the quantum internet and increasing the lifetime of superconducting resonators for use in quantum computers.

In 1967, Wilson brought five American bison to the site, a bull and four cows, and an additional 21 were provided by the Illinois Department of Conservation. Some fearful locals believed at first that the bison were introduced in order to serve as an alarm if and when radiation at the laboratory reached dangerous levels, but they were assured by Fermilab that this claim had no merit. Today, the Fermilab bison herd is a popular attraction that draws many visitors and the grounds are also a sanctuary for other local wildlife populations. A Christmas Bird Count has occurred at the lab every year since 1976. Working with the Forest Preserve District of DuPage County, Fermilab has introduced barn owls to selected structures around the grounds.

During running, particle beams produce tritium, an isotope of hydrogen consisting of a proton and two neutrons that is weakly radioactive with a half life of 12.3 years. This can bind with oxygen to form tritiated water. Tritium levels measured on site are low compared to federal health and environmental standards. Fermilab monitors tritium leaving the site in surface and sewer water, and provides a useful FAQ sheet for those who want to learn more. At an informational meeting for potential bidders for the management contract, held on March 1, 2023, the presentation slides indicated that although the rate of tritium leaving site is below the required standards, there is sufficient tritium contamination on site to represent a "challenge". In particular, tritium produced in the NuMI beamline that send neutrinos to experiments in Minnesota has been pumped into the industrial water cooling system that is used for equipment across the Fermilab campus. As a result, it is concluded that now "tritium contamination is largely throughout the research complex."