Exploring the Production of Antimatter & Particle Accelerators: FAQs Answered

[medwatt]

Hello,
I am not a physicist but occasionally read some particle physics books because I find it fascinating but I am somehow unsure about some aspects.
1. I read somewhere that antiproton is used to treat cancer. If I may ask, how are they produced and stored because I know that antimatter doesn't last long at all.

The W and Z bosons have masses 80-90GeV which makes them about 100 times more massive than the proton.

2. Generally speaking, if I know the mass in eV of a particle (like the W boson) and I have a suitable particle accelerator, does that mean I can produce it ?

3. In producing the W boson, for example, which is a particle associated with the weak force where a neutron decays into a proton, what the particles that should be collided together to ensure the production of a W boson or doesn't it matter whether it is a neutron or a proton ?

I hope you notice that my questions are more concerned with how practically things are done. I hope someone can answer the questions above and provide me with an explanation on working principles of a particle accelerator, choice of particles based on what product is to be produced, energy consumption and why do the particles disappear immediately when produced when energy is not borrowed from space ?

I hope some of what was written doesn't sound foolish.

Thanks

 

[K^2]

Antiprotons are usually produced by smashing protons into some heavy nuclei with enough energy. Naturally, you can't store them, except in a particle accelerator loop, so they have to be produced at the same location you plan to use them.

In general, anything can be made by smashing sufficiently fast particle into each other. Choice of particles you start out with matters if efficiency is important, so there might be some specific tricks there, but I'm not particularly familiar with most of them. The only ones I have had to deal with is meson electroproduction. So if you want pions for your experiment, for example, you'd typically slam an electron beam into some nuclei.

 

[Bill_K]

The Tevatron at FNAL was a proton-antiproton collider. In a nutshell,

Antiproton Source: To produce antiprotons, physicists steered proton beams onto a nickel target. The collisions produced a wide range of secondary particles, including many antiprotons. The aniprotons entered a beamline where beam operators captured and focused them before injecting them into a storage ring, where they were accumulated and cooled. Cooling the antiproton beam reduced its size and made it very bright. After accumulating a sufficient number of antiprotons, beam operators sent them to the Recycler for additional cooling and accumulation before they injected them into the Tevatron.

This article has a more detailed description.

 

[medwatt]

Thanks . . . article was very helpful.

 

[mfb]

It does matter which particles you collide, but you have to keep the accelerator design and physics goals in mind:

- Electron/positron collisions are very clean - some collisions will produce the particle you want to study, and nearly nothing else. In addition, you have a very precise control over the collision energy. The downside is the limited energy - a linear accelerator has to be very long and a circular accelerator has significant problems with synchrotron radiation (reducing the energy), as electrons and positrons are very light.
- Proton/antiproton collisions always produce a lot of background - particles you don't want to study, together with the interesting particles. In addition, the colliding partons (components of the protons+antiprotons) have a random energy - bad for the precision, but on the other hand you can "test" the whole energy range at once. On the positive side, you get more energy and more collisions.
- Proton/proton collisions are very similar to proton/antiproton collisions, but you get even more collisions. High-energetic reactions between quarks and antiquarks are rare, but at high energy (-> LHC) this does not matter.

In general, every type of accelerator can produce every type of particle if the energy is sufficient, but the processes and rates vary.

 

[medwatt]

If I may ask one last question which might sound trivial. 1 electron volt is about 10^-19 J. Why then does it require gigantic accelerators to get particles to energies of 100GeV is about 10^-11 J which is pretty negligible relatively. Is it because they're is no other way to increase the energy of a particle other than increasing its speed ?

 

[Bill_K]

Fully loaded, the LHC circulates about 2800 bunches, initially each bunch contains 10¹¹ particles. The total energy stored in each beam at maximum power is about 350 MJ. The energy stored in the magnets is even greater, 11 GJ.

 

[mfb]

s it because they're is no other way to increase the energy of a particle other than increasing its speed ?

Right. And there is only one reasonable way to accelerate them: Put them in strong electric fields. This is limited to ~30MV/m*, adding 30 MeV of energy per meter. If you want to reach 7 TeV (as in the LHC design), this would require ~230km for each beam - not practical. So you use a circular accelerator, where protons can fly through the same acceleration elements over and over again. But then you need strong magnets to keep them on track, which requires a large accelerator as well ("just" 27km however).

*plasma wakefield acceleration might change this in the future

 

[medwatt]

One last question ... given that some particles decay so quickly ... let's say we have a kaon and and anti kaon beam ... how is it ensured that the particles in the beam do not decay during the period of acceleration ?

 

[mfb]

Acceleration always happens with stable particles - electrons, protons and their antiparticles.
There are kaon beams, but those are produced by hitting a fixed target with a beam of electrons or protons, and used as soon as possible after their production to minimize losses.

There are concepts of a muon accelerator and collider - and muon decays are a serious issue there, the acceleration would have to happen within ~ a millisecond.