## Physics Questions People Ask Fermilab

The Impact of the Accelerator on the Environment

Question:
How many studies have been done to figure out what escapes from the accelerators into the environment and how much of it escapes? I heard from a tour guide that there was no environmental impact, but I don't believe it. How can something dealing with so much energy and traveling so fast not have some of that energy escape into the environment? Have you done research on things like insect life, water life and plant growth in the areas near the accelerator? Why is there the water ring over the accelerator in the first place?
-Jolene

Dear Jolene,

Thank you for your inquiry. Fermilab carefully monitors its accelerators and particle beams. Before I explain to you how we do this, let me comment on your statement about "something dealing with so much energy." When we say that the Fermilab accelerators create the most powerful particle beams in the world, we speak about energy levels at a microscopic scale. Our beams wouldn't knock over a bowling pin if we put one inside the accelerators. And our beam wouldn't create enough energy to heat your house either. Yet at the atomic level, our beams are more powerful than the ultraviolet light we get from the sun, and even more powerful than the x-rays used in hospitals. After all, our instruments explore what is happening INSIDE a proton, one of the buildings blocks of matter. However, nature produces even more powerful beams of particles than we can do. Cosmic rays, which originate in space, constantly bombard earth's atmosphere and shower us with particles of various energies, including some more powerful than the ones circulating our accelerators.

To study matter and its properties, Fermilab's accelerators operate with large numbers of protons and antiprotons - yet all the particles in the beam weighs far less than a gram at any given time. To make sure that the particle beams don't affect their surroundings, all accelerators are equipped with beam absorbers and shields to keep beams from leaving the accelerator beam pipe. On top of that, the most powerful accelerators are build underground in tunnels lined with concrete. The shields work the same way as the shields that hospitals use to control the emissions from their x-ray machines. Because our beams create light more powerful than x-rays, our shields are thicker.

The proper design of beam absorbers and shields is an important activity at Fermilab. We carefully carry out the work prior to any operation of accelerators, and our plans are carefully reviewed by the appropriate agencies. While numerical calculations are used to design absorbers and shields, we use sophisticated particle detectors and instruments to measure and to check the effectiveness of our absorbers and shields. Extensive measurements are made to verify that the levels of protection are well understood.

Once an accelerator is in operation, we have numerous sets of instruments that continuously monitor the area outside the accelerator tunnels, checking that all of our safety objectives are achieved. Also, water and other environmental materials on site are regularly sampled for problems that might have been produced by our accelerators. Throughout our measurements we have never found any results indicative of any risk to the environment. Because of our desire to be absolutely certain that this remains so and that no harmful radiation escapes into the environment, our sampling and monitoring activities are continuing.

Finally to your question about the water ring. To steer particles around a circular ring, you need a lot of magnets. They don't speed up the particles but rather bend the beam path just enough to keep the particles on a circular track. All this equipment is operated electrically and creates heat that we need to get out of the tunnel. Similar to the engine of a car, this is done by water. (Our cooling water, however, has no antifreeze or other additives.) The cooling water takes up the heat from the equipment and is then pumped into the circular canal that you've referred to. The water ring is actually not on top of the accelerator. The top of the accelerator is marked by an earthen berm, and the water ring is about 80 feet to the inside of this berm.

If you want to know more details about these or other topics, please don't hesitate to call me at 630-840-5681. I'm more than happy to answer any additional questions you may have.

Sincerely yours,

Kurt Riesselmann

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