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View Full Version : A question about cyclotrons

Jens
2012-Aug-16, 12:59 AM
I could probably find this out myself, but it seems a simple question so I hope somebody can help. Particles in a cyclotron are accelerated and as they accelerate, the move outward until eventually the escape the machine. What I'm wondering is, is there a specific distance that each particle travels within a given cyclotron, or does it vary? The reason I'm asking is that I'm writing some PR materials for a beam line that runs through several cyclotrons, and I'm wondering if the total length of the beam line can be stated as a precise figure.

trinitree88
2012-Aug-16, 06:07 PM
I could probably find this out myself, but it seems a simple question so I hope somebody can help. Particles in a cyclotron are accelerated and as they accelerate, the move outward until eventually the escape the machine. What I'm wondering is, is there a specific distance that each particle travels within a given cyclotron, or does it vary? The reason I'm asking is that I'm writing some PR materials for a beam line that runs through several cyclotrons, and I'm wondering if the total length of the beam line can be stated as a precise figure.

Jens. As the particles ride the accelerating wave front, they speed up. They would soon bump into the wall of the vacuum chamber and slow, emitting x-rays or gammas, or doing some pair production, but that would be a very short trip. So first you speed them up, then you increase the intensity of the perpendicular magnetic field (to their path), so that they curl more intensely, moving towards the center of the circle. Then you again speed them up again, moving them outwards radially. This process alternates (or cycles...hence cyclotron) until you have reached the limits of the machines' design characteristics. Now at top speed, they can be held there at fixed magnetic field strength, while dissipating energy as bremstrahlung radiation at constant circular velocity. When ready, you can kick them out of the ring with a pulsed magnetic field (called a kicker magnet), down an alleyway to a target zone. Linacs are similar in design when they contain a recirculating loop.
Because the travel speed or timing of the pulses is known, you can slow up the front ones in a bunch, and simultaneously speed up the back ones, to increase the "bunching" density....that's stochastic cooling....using signals that travel across the ring, as the particles take the longer path around it. From stats for the machine they should be able to tell you how many circuits they make during the ramp up to maximum energy, and hence the number of 2 pi R's....path length. pete