## Physics Questions People Ask Fermilab

Accelerate a Gram of Matter

Dear: To Whom This May Concern

I know that the Tevatron can accelerate a particle up to one TeV. Can it accelerate a larger mass. If so I have an exparament you might be interested in. This exparament is comparable to what the half built Super Conducting Super Collider was meant for.

Take a look at this equation and see if it means anything to you:

C2 / M = E for instance 186,453 MpS/ 1 Gram = 34.527 GeV.

I think the reason why you need to build such large accelerators is because your accelerating individual subatomic particles. When you should be accel erating larger masses like one or two grams. The result of this experiment would be the following:

1. The matter being accelerated would decay directly into radiant energy the instant it reached the speed of light.
2. The instant it slowed down the radiant energy would just radiate away in the form of microwaves. Or form up into matter.

I'm sure that the 20 ton magnets that the Tevatron is made of have the power to do that. I would greatly appreciate it if you would give me some feed back on this.

Sincerely, Hontas F. Farmer

Dear Hontas,

It is great to think that you are trying to solve the problem of making accelerators more economical.

Actually the Tevatron accelerates protons up to 1 TeV. What the Tevatron can do is accelerate 6 (soon to be 36) bunches of 10^11 protons each. There are about 10^24 protons in a gram or 10 trillion of the Tevatron bunches.

The first thing is to realize how the forces themselves work. The way you accelerate something in particle physics is to apply an electric field to a particle that has an electric charge like a proton.

Second, like charges repel ! If you can find a gram of protons together, I would like to see them. The problem is that the electric charges that allow the electric field to accelerate the particles forward also make the bunch of charged particles repel each other sideways as well as forward and backward. If you start with a small bunch of protons, over time the bunch gets bigger and bigger until the edges of the vacuum pipe is reached. (An aside: You need vacuum (really low pressure == ie no gas at all including air) since the particles hit the gas molecules when you start trying to accelerate them.) When the bunch gets too big and hits the walls, you start losing part of the beam.

If you think there is some other mechanism for accelerating the particles (or your gram of stuff) try throwing a few grams of matter like a baseball and see how fast you can get it to go. 1 TeV is equivalent to 0.9999995 of the speed of light. Even without special relativity, this is really hard to do. Special relativity makes it even harder to reach a certain speed but it is easier to think in terms of the amount of energy given directly to the particle equals the amount of energy it will receive (minus losses or inefficiencies).

There is a place on Long Island NY (Brookhaven National Laboratory) where entire nuclei are accelerated. This is done though by ionizing completely the atoms so only nuclei remain (removing all the electrons). For example they accelerate gold nuclei (79 charges) to high energies. But remember the energy will have some dependence on the original rest mass which in this case is more than 79 times heavier than a proton (79 protons + ~110 neutrons) so the speed is no greater given the same acceleration capability.

Another thing is that matter can never truly reach the speed of light (if you believe special relativity). It can also never give off the energy equivalent of its rest mass. For example, electrons have a rest mass of 0.511 MeV. I can accelerate them to some energy let's say 200 MeV. They will radiate synchrotron energy in the form of photons if they are in a circular accelerator because any charged particle that is accelerated gives off radiation. If they are travelling in a circle even at a constant speed, the direction of the speed vector is changing so they are accelerating. They would therefore lose all the energy that you have initially supplied to them through your acceleration unless you kept adding more at some constant rate (just to keep them at 200 MeV). If you stop, they will lose energy until they are back down to the rest mass (0.511 MeV) but will never lose this unless --.

The only way you can truly convert the rest mass into energy is to annihilate an electron with an antielectron. So first you have to make antielectrons and bring them near electrons. Unfortunately, the amount of energy it takes to make them is vastly greater than how much you get out of the annihilation.

Actually the weight of the magnets has nothing to do with their power to accelerate anything. In fact the magnets do not accelerate the particles. They merely bend them so they can travel in a circle. Actually if you look back at my previous definition, this is technically acceleration, but no energy is given to the particles by the magnets. The acceleration is done by radio frequency cavities whose net result is to give an electric field to them as they pass.

So the answer to your question is you cannot feasibly accelerate large quantities of matter due to the nedd to have the matter electrically charged (of the same sign) and the charges repelling each other so that the beam gets too large to fit in the machine. Experimenters do try to maximize the amount of particles in the beam(s) of course but there are limits.

Since you are obviously quite interested in physics, you should find out if you can take (or audit) an introductory physics class at your local community college. If you are in the Chicago, Fermilab (perhaps Argonne too) offers various seminars, for example I believe there is "Saturday Morning Physics" which explores some of the topics you would be interested in.

You can contact our Education Office
http://www-ed.fnal.gov/
Fermilab MS 226
Box 500
Batavia, IL 60510
(630) 840-3092 fax: (630) 840-8248

Lederman Science Center
Fermilab MS 777
Box 500
Batavia, IL 60510
(630) 840-8258 fax: (630) 840-2500

I would also encourage you to read Scientific American or Physics Today. Most libraries have subscriptions and the articles are excellent - I had a subscription for a number of years - on both physics and other hard science. They are written at a level that is detailed enough to be interesting but not so much that you have to had known the author to even understand the equations.

Good Luck,

Glenn Blanford
Public Affairs
Fermilab

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