Particle Accelerators. Atkinson. A particle accelerator is designed 'to speed up and increase the energy of a beam of particles by generating electric fields that accelerate the particles, and magnetic fields that steer and focus them.'. Linear Accelerators.
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A particle accelerator is designed 'to speed up and increase the energy of a beam of particles by generating electric fields that accelerate the particles, and magnetic fields that steer and focus them.'
In linear accelerators, particles are accelerated in a straight line, often with a target at one to create a collision
The size of linear accelerators varies greatly
A cathode ray tube is small enough to fit inside of a television and computers
Stanford’s linear accelerator is two miles long
In 1929, Ernest Lawrence developed the first circular accelerator, only 4 inches in diameter, and contained two D-shaped magnets. First circular particle accelerator
Electron “ramps up”to full energy over manyturns!
Accelerating cavities(many of them !!!)
e - this way
Photonsare unaffectedby a magnet
e+ this way
Using magnets, the negative electrons can be bent one wayand the positrons bent the other way, thus “separating” them fromeach other !
Once separated, the positrons can be “focused” and accelerated !
E ~ 5 [MeV]per beam
Because electrons and positrons have the samemass, but opposite charge,they can both be accelerated in the same circularaccelerator !!
Around the collisionpoint, we build adetector to detect theparticles coming out.Using these detectors, we measure:
1. Momentum2. Type of particle3. Charge+ many other quantities
E ~ 5 [MeV]per beam
There are several concentric layers to this detector. Each layer serves a specific function:
1. Tracking – map out the flight path of the particle2. Calorimeter – measure the energy of photons3. Particle identification: detectors capable of distinguishing pions from protons from kaons, etc (I won’t cover this)…
As charged particle passes through gas, it ionizes the gas.This creates “free” electrons which are attracted toward the 1500 V wireGenerates a voltage pulse !You know thatthis wire “saw”a charged particle !
~1 mm sep.
Box filled with gas,perhaps Argon.
A charged particle, likea proton, or p+
Wires at+1500 V
Measure charge by the direction the particle curvesMeasure momentum by how much it curves. If it curves alot low momentumIf it only curves a little high momentum
Image courtesy of CERN
The Large HadronCollider