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NuMI/MINOS Questions & Answers


What is the MINOS experiment? What is NuMI?
The Main Injector Neutrino Oscillation Search, or MINOS experiment, located half a mile underground in the historic Soudan iron mine in northeastern Minnesota, will probe the secrets of subatomic particles called neutrinos . The neutrinos will be produced by a particle accelerator at Fermi National Accelerator Laboratory" near Chicago. Beginning in February 2005, neutrinos in the NuMI (Neutrinos at the Main Injector) beam will be directed 450 miles straight through the earth, from Fermilab to Soudan--no tunnel needed.

MINOS detectorIn Minnesota, a 6,000-ton steel detector will search for neutrinos that have changed from one kind to another during the split-second trip. More than a trillion man-made neutrinos will pass through the MINOS detector each year. Because neutrinos interact so rarely, only about 1,500 of them each year will collide with atoms inside the detector. The rest will pass through with no effect. The 200-plus MINOS experimenters will use the change from one type of neutrino to another as the key to unlocking neutrinos' secrets: Where do they come from, what are their masses and how do they change from one kind to another? How are neutrinos related to the mysterious dark matter that makes up almost a quarter of our universe?

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What are neutrinos?
Invisible but all around us, neutrinos are among the most fascinating of the known particles in the universe. They interact so little with other particles that trillions of neutrinos from space pass through our bodies each second without leaving a trace. Neutrinos come in three kinds, or "flavors," as scientists call them. Neutrinos have no electric charge. They do have mass, but the heaviest neutrino is at least a million times lighter than the lightest charged particle. Current detailed studies of neutrinos, including the MINOS experiment, will tell scientists whether neutrinos conform to the patterns of ordinary matter or whether they are leading toward the discovery of new phenomena.

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Are neutrinos harmful?
Although scientists have much to learn about neutrinos, they know that neutrinos cannot harm the health or safety of people, animals or other living things. Neutrinos cannot harm the water, the air or the earth they pass through. The reason they are harmless is that they interact so rarely with other particles of matter. They pass through matter, including the earth, with no effect, as if it were not there. Scientists know that neutrinos are not harmful because of the many neutrino experiments and observations of naturally-occurring neutrinos that have been carried out all over the world since the discovery of neutrinos in 1956. The safety of neutrinos was one of many topics addressed in the 1997 Environmental Assessment prepared for this project.

Because their names are similar, it is easy to confuse NEUTRINOS and NEUTRONS. The NuMI beam is made of NEUTRINOS. Unlike neutrons, which do interact with other particles of matter and can have harmful effects, NEUTRINOS do not cause harm to people or to the environment. The NuMI beam will NOT contain neutrons.

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Do neutrinos exist in nature?
Yes. Trillions of neutrinos produced naturally in the sun and in the atmosphere are streaming around us and through us at every moment, day and night. Neutrinos travel through space, passing through planets, including Earth, as though they weren't there. They exist naturally in three types, or "flavors," and can change from one flavor to another.

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What was the approval process for the NuMI neutrino beam and the MINOS experiment?
Project Approval
Planning for a long-distance experiment to study neutrinos began over a decade ago. In 1995, the High Energy Physics Advisory Panel of the Department of Energy selected Fermilab's proposal to produce a neutrino beam directed to the Soudan Iron Mine. Fermilab produced conceptual design reports for review by the Department of Energy, which approved the project in 1997. The approval by DOE of further engineering and technical design reports led to the start of construction for NuMI/MINOS in 1999. Since 1999, the Department of Energy has conducted regular reviews of the project every few months.

Environmental Assessment
Before the NuMI project could be approved for construction, the Department of Energy, which owns Fermilab, conducted a detailed and comprehensive Environmental Assessment, as required by federal law. The Environmental Assessment examined the potential impacts of the NuMI Project, during both construction and operation, on public health; on the health and safety of the workers on the project; on threatened and endangered species; on soil, air and water; and on historical structures. The Department of Energy studied impacts in Illinois, Wisconsin and Minnesota and consulted the appropriate regulatory agencies in all three states, as well as the responsible federal agencies. Based on the Environmental Assessment, the Department of Energy concluded that the NuMI /MINOS project would not affect the environment and that, therefore, an Environmental Impact Statement would not be required.

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Does the neutrino beam require easements for the property it passes beneath?
No easements are required for the neutrino beam, because it uses no structures, requires no alteration or construction beyond the Fermilab site, and has no effect on the earth as it passes through.

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What is the Main Injector?
The Main Injector is a particle accelerator at Fermilab. It is a circular accelerator, two miles in circumference. It will produce the neutrinos that travel from Fermilab, near Chicago, to a particle detector in the historic Soudan Iron Mine in northeastern Minnesota.

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What is a neutrino beam?
A beam is a group of particles moving in the same direction at the same time. The beam of a flashlight, for example, is made of particles called photons streaming from the bulb at the speed of light. A mirror inside the flashlight sends the photons in the direction the flashlight is pointed. A neutrino beam is more complicated than a flashlight, but the basic idea is the same. The beam consists of neutrinos, all from the same source, moving in the same direction at the same time. Like the flashlight beam, the neutrino beam spreads out as it travels. It starts out about six feet wide, the diameter of the beam pipe, but grows to several miles wide by the time it reaches the detector at Soudan, in Minnesota. Like the flashlight beam, the neutrino beam becomes fainter as the neutrinos spread out over a wider area. There are differences between a flashlight beam and a neutrino beam. A flashlight beam can pass easily through air, glass or water, but not through rock or soil. A neutrino beam, on the other hand, can readily travel through any substance on earth.

To make a neutrino beam, physicists start with a beam of protons from Fermilab's Main Injector accelerator. Magnets direct the protons onto a graphite target. When the protons strike this target, they take the form of new particles, which in turn produce neutrinos. The neutrino beam is aimed downward at a 3.3 angle toward the Soudan Underground Laboratory, 450 miles away. Although the beam starts out at 150 feet below the ground at Fermilab, it will pass as much as six miles below the surface as it travels toward Soudan. The neutrinos travel at the speed of light and make the trip from Illinois to Minnesota in just two and a half thousandths of a second.

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Why are Fermilab scientists sending a beam of neutrinos such a long distance from the laboratory?
To answer their questions about neutrinos, physicists need to study their behavior after they travel over a long distance. This is because neutrinos travel at the speed of light and studying a process that takes even a fraction of a second is not possible in one place. Scientists of the MINOS experiment need a controlled source of neutrinos traveling to a particle detector located far from the neutrino source. The Soudan Iron Mine is the right distance from Fermilab, and it contains an already-operating underground physics laboratory.

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What is Fermilab?
Fermi National Accelerator Laboratory is a Department of Energy National Laboratory situated in Batavia, Illinois, about 40 miles west of Chicago. Fermilab operates the world's highest-energy particle accelerator, the Tevatron, on its 6,800-acre campus. About 2,500 physicists from universities and laboratories around the world do physics experiments using Fermilab's accelerators to discover what the universe is made of and how it works. Fermilab was founded in 1967. Discoveries at Fermilab have resulted in remarkable new insights into the nature of the world around us. Fermilab is operated by Universities Research Association, Inc. a consortium of 90 research universities, for the United States Department of Energy, which owns the laboratory.

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How many hours a day will the NuMI beam run? How long will the MINOS experiment operate?
The NuMI beam will operate every day, 24 hours a day, for 10 millionths of a second every two seconds. The total beam time adds up to about 150 seconds, or two-and-a-half minutes, per year. Plans call for the MINOS experiment to operate for about five years, although future improvements might extend its life.

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What happens if the accelerator malfunctions? Could the NuMI beam go astray or be "turned up" too high?
If something breaks or malfunctions at a particle accelerator like the Main Injector, the accelerator simply turns off, like a light bulb going dark when the switch is flipped. An accelerator cannot "melt down" or blow up, because it has no stored energy. It simply stops. The NuMI beam is constructed so that it can only go in one direction, from Fermilab to Soudan, Minnesota. It can be turned on and off, but it cannot be redirected. Likewise, the number of neutrinos in the beam (its intensity) is determined by the way the beam is constructed and cannot be increased without modifying the beamline, at least a year-long operation.

While it is true that one can work (or even live) in the center of a neutrino beam without any effects, the same is not true of the proton beam that Fermilab uses to produce the neutrinos. Particle accelerators at Fermilab and around the world are designed, built and operated to keep people and the environment safely shielded from any harmful effects of particle beams. The proton beam that produces the neutrinos for NuMI is confined to the Fermilab site, where it is monitored 24 hours a day. In the event of a malfunction, it shuts down automatically before it can have an effect on the environment on the Fermilab site. The beam is produced in the same way, with the same standards of personnel and environmental safety, that have kept Fermilab operating safely for 35 years.

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Who is involved in the MINOS experiment?
The NuMI project, with the MINOS experiment, includes over 200 scientists, engineers, technical specialists and students from 32 institutions in 6 countries, including Brazil, France, Greece, Russia, the United Kingdom and the United States. The institutions include universities and national laboratories. The project is hosted by Fermilab, under contract to the United States Department of Energy and by the Soudan Underground Laboratory, operated by the University of Minnesota in cooperation with the Minnesota Department of Natural Resources.

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Are neutrinos studied elsewhere in the world?
Yes, there are many neutrino experiments going on in the world, from undersea experiments in the Mediterranean to underground experiments in Canada to under-ice experiments in the Antarctic. Other long-baseline experiments similar to MINOS include the K2K experiment in Japan and the CERN-to-Gran Sasso experiments in Europe.

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What are the practical benefits of the MINOS experiment?
MINOS, like most particle physics experiments, is basic research. It is not directly aimed at the invention of any new products or the application of a new technology; its sole purpose is to advance human understanding of the physics of the neutrino. Scientific research generally falls into one of two categories: basic research or applied research. Some projects may have elements of both, but usually one or the other predominates. Applied research uses the knowledge gained in basic research to develop new technologies. Basic research is aimed at simply understanding the laws of nature, to learn how the world works. We know that this new knowledge will have profound effects on technology, on the economy, and on our well-being, but we cannot predict exactly what they will be or when they will occur.

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Why haven't I heard about NuMI/MINOS before?
Since the project's beginning in 1999, Fermilab has issued press releases and news stories about NuMI / MINOS. Now that the experiment is about to begin operating, Fermilab is renewing its efforts to inform the public, the press and public officials.

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If I have more questions, where can I get the answers?
Fermilab welcomes the opportunity to address questions and concerns about NuMI/MINOS. Or call the Fermilab Office of Office of Communication at 630-840-3351 during regular business hours.

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last modified 1/18/2005   email Fermilab