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Q & A: How to make antimatter

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Q:
How exactly is antimatter made? I know it is made in an accelerator but I donít know the details.
- Ellen (age 15)
Australia
A:
The main idea in making antimatter is just getting enough energy in a collision to allow the particles to be made. If you get electrons going fast enough and throw them at a piece of material called a target, preferably made out of atoms that have a large atomic number, you will have a shower of electrons, positrons (anti-electrons) and photons. The details are as follows:

A high-energy electron, when it comes near a nucleus, will feel the electric field of the charged nucleus, and be deflected in its path. The larger the charge of the nucleus, the more frequently this deflection will happen at large angles. When a fast electron is diverted from its straight-line path, it radiates some of its energy away as photons. High-energy photons, when they come near another nucleus, can spontaneously turn into an electron-positron pair (conserving charge and the "number of electrons", which both add to zero since a positron has positive charge and is an anti-electron). The second nucleus is there to exchange energy and momentum with, otherwise you cannot start with a photon (zero mass) and end up with two objects with mass and conserve energy and momentum.

If the electron and positron thus produced have enough energy, they can undergo scattering with more nuclei, radiate photons which can pair-produce more electrons and positrons, creating a whole "shower" of electrons, positrons, and photons. Positrons then can be separated away with magnets and collected in particle accelerators.

At Fermilab, we make antiprotons all the time. The process is similar, where protons are thrown with high energy into stationary targets. Most of the stuff that gets made are pions, but every now and then you'll get an antiproton. Instead of photons, the mediating force carriers are gluons, which carry the strong nuclear force. Many gluons must be exchanged because you need to create three antiquarks to make up an antiproton, and get lucky enough for them to stick together in an antiproton.

Tom

(republished on 07/20/06)

Follow-Up #1: Creation of antimatter at the CERN LHC

Q:
Could the use of CERN's new Large Hadron Collider (LHC) actually work to initiate the creation of antimatter?
- E. Paul Smith, Age 54.75
Houston, Texas, USA
A:
The answer is yes, but it's not new news.  Antimatter has been created in abundance by high energy cosmic rays and with past and current accelerators like Fermilab. The anti-electron, or positron,  was postulated in1928 by Paul Dirac, and was observed in a cloud chamber by Carl Anderson in 1932.  Owen Chamberlain and Emilio Segre earned a Nobel Prize for the first man-made creation of the antiproton at the Radiation Laboratory at Berkeley in 1959. 
The actual amounts of the antimatter collected are pretty small, however, enough to measure their properties like mass, charge, interactions, etc. 

LeeH

(published on 04/11/08)

Follow-Up #2: Building particle accelerators

Q:
What exactly would you need to make a particle accelerator? How do you construct one?
- Nick (age 23)
Lafette IN, 47904
A:
That's a tough question to answer in a short space.  There are many different types of particle accelerators using a wide variety of techniques.   Each one would be worth a long discussion.
To be brief, you need an initial source of particles:  a hot filament for an electron accelerator, a bottle of hydrogen for a proton accelerator.  After that you need a combination of electric fields to accelerate the particles and magnetic fields to guide them.   The simplest example is a cathode ray tube.  A hot filament provides the electrons and a several thousand volt electric potential accelerates them.   When the electrons hit the phosphor-coated screen a small dot of light shows up.   A much more complicated example is the proton accelerator at Fermilab.  The protons, from a bottle of hydrogen, are first accelerated by a Cockroft-Walton generator, then pass through a linear accelerator using microwave cavities, thence into a 20 Gev synchrotron booster, then finally into a one kilometer diameter main ring accelerator.    Pretty complicated.
There is a nice article at   http://en.wikipedia.org/wiki/Particle_accelerator that you should look at. 

LeeH

(published on 07/18/08)

Follow-Up #3: What is Fermilab?

Q:
WHat exactly is fermilab?
- Joel (age 20)
tucson, AZ, United States
A:
Fermilab is a national research laboratory about 25 miles west of Chicago, Illinois.  It is named after the famous Italian physicist Enrico Fermi who emigrated to the United States in 1938.  Fermi developed the first nuclear chain reaction pile and later was instrumental in developing the atomic bomb at Los Alamos.   Fermilab's  main scientific objective is the study of elementary particle physics and, more recently, some aspects of cosmology such as Dark Energy.   It is the home of the Tevatron, currently the world's highest energy accelerator.  Many fundamental particles have been discovered there such as the Top Quark and the Upsilon particle.  
You can find lots more information at:  http://en.wikipedia.org/wiki/Fermilab  
and  http://www.fnal.gov/pub/about/index.html 

LeeH

(published on 08/30/09)

Follow-Up #4: Practical problems in making anti-matter

Q:
Why is it so difficult to make alot of antimatter, and what is needed to make alot more? A bigger or longer accelerator perhaps?
- Quintin (age 24)
South Africa
A:
The major problem is that it takes a lot of money to make just a small amount of anti-protons.  You need a big costly accelerator and the production rate is small.  The second problem is that you just can't store them in an ordinary bottle, they would just interact with the sides of the bottle and annihilate.    You need what is called a storage ring which is a ring of magnets with a vacuum tube inside. 
Never-the-less, there is such a ring at the CERN accelerator in Geneva, Switzerland where small amounts of anti-protons are stored and used for various experiments.
See:   http://cerncourier.com/cws/article/cern/28112   for a nice news article.
On a larger scale, at Fermilab anti-protons are not only stored but accelerated and made to collide with real protons producing weird and wonderful new particles, for example the Top Quark and, hopefully, the Higgs boson.  
See:  http://en.wikipedia.org/wiki/Tevatron

LeeH

(published on 09/29/09)

Follow-Up #5: antimatter explosion

Q:
If you creat antimatter and yet have matter everywhere wouldn't they touch and creat some type of explosion, implosion, essentially destroying everything? Also, could antimatter be collected from a different source than our own man-made devices?
- Alan (age 18)
Tucson, AZ
A:
When you make antimatter, you have to put in some energy. When the antimatter annihilates it releases the same energy you put in, minus some that leaked out at stages.

It's essentially impossible to collect antimatter from cosmic rays, because you don't know where or when each particle will show up, unlike the antimatter made in labs.

Mike W.

(published on 10/01/09)

Follow-Up #6: antimatter energy

Q:
How much energy is needed to make 1g of antimatter?
- Solomon jappa IT TECH (age 30)
Leesburg,VA, United States
A:
You'd have to make 1 gm of matter with that, so 2gm*c2 would be 18*1020 ergs, or 1.8*1014 Joules. In practice, the process wouldn't be very efficient, so more energy would be needed.

Mike W.

(published on 12/06/09)

Follow-Up #7: fate of antimatter

Q:
Hi, I'm certainly no scientist, but just someone who has always had a keen interest in the subject and find it subject fasinating. My question is this: Of course we know the theory that after the big bang, a exact amount of matter, and anti-matter was released. These collided and annihilated each other, which obviously suggests the question "What happened to all the anit-matter, as there is quite clearly still matter around us?" {This is not my question just to be clear}. My question is this: We know that when matter and anti-matter collide, there is a large release of energy in the form of gamma radiation. The connection that comes to mind instantly is the Sun and it's high amounts of omitted gamma radiation also............... is/could there a connection between the two? Has the remaining amount of anti-matter been stored within each and every sun within the entire universe (including our own sun)? Does the suns power not just come from Hydrogen, but predominately from anti-matter stored internally that's comstantly colliding with equally stored matter? I'd be interested in getting an experts opinion on this. As previously stated, I'm certainly no scientist, so please be kind if the question is deemed ridiculous or stupid. Thanks. Wayne
- Wayne Fielder (age 29)
United Kingdon
A:
Wayne- Seriously, that's a nice question.

When matter and antimatter "annihilate" they really don't leave any particular traces of what was there before, except for the total amount of energy, momentum, and angular momentum.  The latter two quantities average to zero. So what's left from all the antimatter is just that the amount of energy per unit of matter is larger than it would have been if the antimatter had never been there.

The energy released by nuclear fusion in the sun comes from reactions that can be reproduced on earth. These don't require antimatter ingredients. It's true that gamma rays can come from nuclear reactions and also from annihilation events, but that just means that they are generic products of processes with the right energy scale.

Mike W.

(published on 06/05/10)

Follow-Up #8: Annihilation rate of anti-electrons (positrons)

Q:
I have read that the discovery of anti electron was when Carl Anderson was studying cosmic particles in a cloud chamber and observed a particle bent to the left. Why does that anti electron did not annihilate?
- Jamaeca (age 21)
Philippines
A:
Positrons don't  annihilate instantly, it takes some time. For a positron at rest, when it has found an electron partner, they will do a dance for an average of 125 pico-seconds and then decay into two or three gamma rays.  This rate can be calculated using standard quantum electrodynamics methods.
When the positron passes through a cloud chamber it simply doesn't have enough time around any particular electron.  What it does do, however, is to ionize some of the atoms which, in turn, allows the super saturated water vapor to condense along the path.

LeeH

(published on 09/01/12)

Follow-Up #9: Any relationship between anti-matter and black holes?

Q:
Is there a relationship between the creation /collisions of antimatter and the creation of black holes?
- jabeil (age 16)
tracy, CA
A:
Not really, except that they are both manifestations of currently accepted laws of physics.  Anti-matter is described by quantum field theory.  Black holes are described by gravity in general relativity.   These two types of description are distinct.  Perhaps in the future there will be someone able to connect them but for the moment one just has to accept them as they are.

LeeH

(published on 02/01/13)

Follow-Up #10: Antimatter Annihilation

Q:
So I was mildly interested in antimatter, and did a quick Google search and found this. After reading through the questions and answers, it was sufficient to pique my interest to a new height. Maybe this is a stupid question, but I thought that matter could not be created or destroyed, but what I see here is that it can be 'annihilated' which is practically the same thing. Secondly, what does happen when normal matter comes in contact with anti-matter? Is there a massive explosion or whatever as the sci-fi world loves to believe? I hope my questions pertained to the topic.
- Peter (age 15)
Fort Collins, Colorado, USA
A:

When a particle collides with its antiparticle, their rest masses are annihilated and converted to other forms of energy. This does obey physical law because, in a closed system, energy and momentum must be conserved, as well as some other quantities such as electronic charge. In this case, the energy that is in the form of rest mass in the two particles plus their kinetic energies is converted to energy in the form of rest masses and kinetic energies of other subatomic particles or (purely kinetic energies) of photons (light). This is just what happens between two particles.

It is hard to say exactly what would happen if you had a "chunk" of matter and antimatter and threw them together, but it would definitely be extremely energetic and violent, and therefore very difficult to test - even if we already had a large amount of antimatter, which is difficult to create. Furthermore, as the two "chunks" of different matters were pushed together, the forces caused by the reaction would cause a tremendous outward acceleration that would further complicate things. It's difficult for us to say what would happen quantitatively, although there may be some experts who know. If you're interested in antimatter though, you should check out some of the other questions we've had on the subject here.

Samson (mods by mw)


(published on 02/19/13)

Follow-Up #11: Does antimatter have any benefit to mankind and environment?

Q:
Does antimatter have any benefit to the mankind and environment?
- anonymous (age 20)
anonymous
A:

Dear Anonymous,

The first thing that popped into my mind was PET, Positron Emission Tomography.  See http://en.wikipedia.org/wiki/Positron_emission_tomography.  Positrons are the anti-particles of ordinary electrons.   This procedure allows doctors to compose a three-dimensional image of the body for medical diagnostic purposes. I know it is used, I had one myself.  In addition doctors at the CERN laboratory in Switzerland are investigating the use of anti-protons in cancer therapy.  You can Google "antiproton therapy" to find out more about it.  

Antimatter itself doesn't last very long so there are no long term environmental hazards.   It annihilates as soon as it meets up with a suitable ordinary-matter particle.     Finally, I should say that the study of anti-matter particles allows us to better understand the fundamentals of what the universe is made of and how it works.

LeeH


(published on 05/31/13)

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