At CERN, the speed of accelerated particles is primarily determined by measuring their kinetic energy, which is achieved through techniques involving bending magnets. The strength of these magnets, when calibrated with known energy and momentum values, allows scientists to ascertain the energy of charged particles. Additionally, in linear accelerators, the timing of magnetic field transitions is crucial for determining particle speed, as particles must synchronize with these transitions to achieve high speeds. The process is complex and relies on precise measurements rather than simple assumptions about magnetic fields.
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chrisakel said:does anybody know how scientists and physicists at places such as CERN determine the speeds of the particles that they accelerate to nearly the speed of light? basically, what is their technique for determing the speed of the particles?
chrisakel said:thanks, but do you have any idea how they measure the kinetic energy, there has to be a very specific method that they use due to the speeds of the particles?...I actually e-mailed a CERN scientist and asked him this very question but unfortunately I received no reply.
chrisakel said:I must be getting confused when you say that you channel the "beam"...what is it a beam of?
ice109 said:couldn't you measure a moving particle's energy using relativistic kinematics, collide it with something big, see how fast it speeds away? or can you not guarantee conservation of energy?
Jeff Reid said:IIRC, for a linear accelrator, simply time the transition of the magnets, and check to see if any electrons made it through the narrow timing window which requires high speed in order to sync up with the transition speed. Either you get a "hit" and an electron is going at a predetermined speed, or you get a "miss". With a D type accelerator, the radius of the path and the strength of the magnetic field can also be used to determine the speed of an electron.
Since the acclerators can't really "react" to a particle, the speed is basically predetermined by the strength and timing of the magnetic fields.
Jeff Reid said:From a wiki artiticle:
"As the particles approach the speed of light the switching rate of the electric fields becomes so high that they operate at microwave frequencies, and so RF cavity resonators are used in higher energy machines instead of simple plates."
http://en.wikipedia.org/wiki/Particle_accelerator
My point is that the speed of accelerated particles is pre-determined by the rate of change and strength of magnetic fields. Accelerators don't "react" to the presence of the particles they accelerate, they are just "pre-programmed" to generate a pre-determined amount of acceleration.
In the case of linear accelerators, distance between fields can increase along the path to limit the rate of transition as a particle increases speed.
I didn't mean to imply that. What I meant was for a given speed of a particle, the strength of the field determines it's path (radius). Getting back to the OP:ZapperZ said:The speed of the particles are NEVER determined by the magnetic field!
It's mostly pre-determined by the accelerator. When acceleration is done, it involves cycling of fields at a high rate, and it's up to the particles to end up in a window of time that syncs up their position, speed, and acceleration with the cycling of the fields.How do ... scientists and physicists determine the speeds of the particles that they accelerate?