 |
| View of the LHC tunnel sector 3-4 Maximilien Brice (CERN), CERN Document Server, Attribution-Share Alike 3.0 Unported |
Within the 8.5 km-diameter Large Hadron Collider (LHC), sub-atomic particles are accelerated to close to the speed of light by electric fields in radiofrequency (RF) cavities. The particles naturally want to travel in straight lines (Newton's first law), but powerful magnets steer the beam, keeping it moving in a circular path while also focusing it. The RF cavities give the particles a "kick" each time they circulate around the loop, accelerating them and increasing their velocity. Eventually, the particles collide, and scientists study the results of the collisions.
Beam steering was also used in the cathode-ray tube (CRT) of your old TV. A beam of electrons, known as cathode rays, was generated by an electron gun at the back of the tube. Coils on the neck of the tube created a magnetic field that steered the beam, causing it to trace out a picture on a phosphor screen. (Only a single spot is visible at any one time, with persistence of vision giving the appearance of a continuous picture.) The same principle of the force exerted by a magnetic field on moving electric charges (the electron beam, in this case) is also used in electric motors, where the force acts on current-carrying conductors to produce rotation.
No comments:
Post a Comment