Particle Accelerator for Uncharged Particles?

[LarryS]

Particle accelerators use the electromagnetic field to accelerate charged particles.

Would it be possible to build a particle accelerator for uncharged particles? Say we are given a narrow beam of neutrons. How could we accelerate them so that the accelerated particles were still in a well-defined narrow beam?

Thanks in advance.

 

[Fervent Freyja]

They have been around for a while now.

http://nucla.physics.ucla.edu/sites/default/files/kmahn_ucla_accnu_v1.pdf

 

[e.bar.goum]

They have been around for a while now.

http://nucla.physics.ucla.edu/sites/default/files/kmahn_ucla_accnu_v1.pdf

While these are indeed beams of neutrinos (though with huge size and $\Delta E$ compared to beams of charged particles), they aren't well-defined, narrow, accelerated beams, which is what the OP was asking. These are beams that are produced by reactions of accelerated charged particles. Once you produce neutrinos via pion decay, the energy you have is the energy you get. You can't manipulate them.

The story is similar in neutron beams. Given, say, a thermal flux of neutrons from a reactor, you can use collimators and monochromators to restrict the size and energy of the neutrons by essentially filtering out unwanted energies, but you cannot accelerate them. You can also produce high energy neutrons in nuclear reactions, but like the neutrino case, it's the reaction and velocity of the accelerated charged particles that determines the velocity of the neutrons.

Of course, neutrons have a magnetic moment, so you can manipulate them through their magnetic moment. But in most cases this effect is negligible. The exception is ultracold neutrons, which are very very slow, so the effect is non-negligable. They are slow enough (neV) that you can trap them. This trapping process involves de-accelerating the neutrons. Naturally, the same method can also be used to accelerate them, but only to a small extent (until they were no longer ultracold). The limiting factor is magnet strength.

 

[mfb]

Secondary beams are the only option for high energies. Shoot accelerated charged particles on a target. That releases neutrons and produces neutral kaons, it also produces charged pions which then release neutrinos in their decay. The relative production rates depend on the collision partners and the energy.

 

[ZapperZ]

Particle accelerators use the electromagnetic field to accelerate charged particles.

Would it be possible to build a particle accelerator for uncharged particles? Say we are given a narrow beam of neutrons. How could we accelerate them so that the accelerated particles were still in a well-defined narrow beam?

The answer is "NO". There are no mechanisms to accelerate neutral particles. If there are, we would have used it by now.

Are neutral particles produced from accelerators? Sure! Neutrinos and spallation neutron sources all produce neutral particles in accelerators. But once born, they are not accelerated. The accelerators are merely devices to produce these neutral particles, not to accelerate them.

Zz.

 

[LarryS]

The answer is "NO". There are no mechanisms to accelerate neutral particles. If there are, we would have used it by now.

Are neutral particles produced from accelerators? Sure! Neutrinos and spallation neutron sources all produce neutral particles in accelerators. But once born, they are not accelerated. The accelerators are merely devices to produce these neutral particles, not to accelerate them.

Zz.

Makes sense. I know I'm mixing classical mechanics with QM, but my original intention is posing the question was to try to find an example of F=ma in which the "F" was not at its heart electromagnetic.

 

[ZapperZ]

Makes sense. I know I'm mixing classical mechanics with QM, but my original intention is posing the question was to try to find an example of F=ma in which the "F" was not at its heart electromagnetic.

Then what type of "heart" are you looking for?

Again, if you are asking for our current technology, the answer is obvious in the sense that if this is feasible, we would have done it. And trust me, there are MANY applications that can use a focused neutron beam. We would have done it already.

BTW, this has nothing to do with "QM". The overwhelming majority of the physics involved in particle accelerators is classical E&M.

Zz.

 

[mfb]

Makes sense. I know I'm mixing classical mechanics with QM, but my original intention is posing the question was to try to find an example of F=ma in which the "F" was not at its heart electromagnetic.

Gravity?

 

[e.bar.goum]

Gravity?

I can make a rather nice beam of neutrally charged rocks if you like!

ETA: relevant: http://www.smbc-comics.com/?id=3554

 

[mfb]

Well you won't reach high speeds in our solar system, but that is not necessary to demonstrate F=ma.

 

[LarryS]

Gravity?

Is gravity still considered a force? I thought the GR view was that it was a field of acceleration, not a field of force.

 

[mfb]

Newtonian physics is a perfecly valid model for everyday objects. It is not exact, but neither is the Lorentz force as an electromagnetic example of a force (because it does not consider quantum mechanics).

 

[Khashishi]

We have hydrogen neutral beams. But these are basically proton beams that are fired through a gas to neutralize them, and a bending magnet removes the unneutralized ions.