Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: geordief on 07/05/2019 18:38:23
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As I understand it the particle in the accelerator must have an electric charge .
So do we view the situation as a charged particle being accelerated by a static (electro-?) magnetic field or is it an interactive process where the charged particle has its own field and does the interaction between the charged particle the external field cause that field to weaken .
Also ,if the power supply is cut ,does the field disappear and so does it need to be continuously renewed?
Does this "renewal" occur at the speed of electro-magnetic propagation (c) ?
Apologies if my level of ignorance is too great or if my questions don't "hang together"
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I am no authority on how an accelerator works
As I understand it the particle in the accelerator must have an electric charge.
From what I see on a wiki link of linear accelerators, the particles are charged and propelled by alternating electric fields, which means yes, one needs to know where the particle is. It cannot be a continuous beam. The circular ones can't work exactly like that since they need something to maintain the continuous high acceleration needed to bend the path.
Contrast this with something like a solenoid which can apply force to a piece of ferrous but not charged material using a static field. The door locks on my car work this way.
A change in the field like that indeed needs time to propagate. There is no time to send signals from a central control point, so the power and controls would need to be local and preprogrammed.
Also ,if the power supply is cut ,does the field disappear and so does it need to be continuously renewed?
The field is gone with no power. The things eat copious electricity, sometimes at a pace outstripping the power consumption of whole countries.
Hope my answers are not excessively wrong.
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Acceleration of the charged particles occurs by bombarding them with microwave energy, with the frequency and phase set so that the particle is always attracted in the same direction. The charged particle is protected in a "drift tube" during the period that the microwave energy reverses phase. If the power stops, the microwaves stop, and acceleration ceases.
Bending the beam in a circle (like the LHC) is done by superconducting magnets, These are able to maintain their magnetic field even after the power is cut - provided the temperature doesn't get too high so they stop superconducting.
As soon as a power cut occurs (or any other anomaly), the LHC dumps the entire beam into large blocks of graphite. The amount of energy is described as like "the kinetic energy of a jumbo jet landing", and it is dumped in just 45 microseconds.
This much energy released in an uncontrolled manner could destroy the vacuum tube, magnets and control circuitry, so this should be avoided at all costs.
See diagram at: https://en.wikipedia.org/wiki/Particle_accelerator