Why do particle tracks curve?

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Why do the particles (tracks) in a Bubble Chamber curve (as spirals)?

http://www.particlephysics.ac.uk/news/picture-of-the-week/picture-archive/tracks-in-a-hydrogen-bubble-chamber/000329_med.jpg

Why don't these particles just go off in a straight line? Any when they curve, why do they form spirals? Are they spiraling "in" or spiraling "out"?

I understand that the particles in the chamber are affected by a strong magnetic field which causes the direction of their curve, but I'm not sure why they form spirals instead of just curving it the wall of the chamber or something.

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Seems to me that they follow the lines of the magnetic field applied to the chamber..

Quote:

The entire chamber is subject to a constant magnetic field, which causes charged particles to travel in helical paths whose radius is determined by their charge-to-mass ratios and their velocities.

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@Francis,

Francis wrote:

Seems to me that they follow the lines of the magnetic field applied to the chamber..

Quote:
The entire chamber is subject to a constant magnetic field, which causes charged particles to travel in helical paths whose radius is determined by their charge-to-mass ratios and their velocities.

So, are they forming spirals because the particles are slowing down?

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@rosborne979,

No doubt someone knows the vector maths but in general "electric current" is to magnetic field as a line is to a "circle". (Flemings left hand rule...CURRENT/FIELD/MOTION....3D vectors... etc)

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@rosborne979,

They certainly are as they are retained by the magnetic field..

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@Francis,

Francis wrote:

They certainly are as they are retained by the magnetic field..

So the particles are spiraling "into" the spiral as they slow down.

What happens to the particles when they reach the center of the spiral? Do they just hover there or do they evaporate or something?

1 Reply

@rosborne979,

Think about it, Ros: what is the smallest particle that is stable alone?

All the others combine or are absorbed by the matter around when they lose their initial energy..

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@rosborne979,

Quote:

Why don't these particles just go off in a straight line?

Why doesn't the moon or all the planets, go off in a straight line.

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@rosborne979,

If the motion though the magnetic field generates a force normal to the direction of motion, you should start to curve. If the particle starts to slow, but the generated force stays the same, you would get tighter and tighter spirals. I have no idea if that is actually what is happening since I'm not sure what the formula for the generated normal force is.

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Why do particle tracks curve?

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