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Particle Accelerators and Detectors

What is the first thing that comes to mind when you think of a particle accelerator? For most people, the primary connotation with the phrase “particle accelerator” is CERN’s Large Hadron Collider (LHC). However, few people know that the principle of particle accelerators was also widely used in TV monitors and old computers. Even though these linear particle accelerators in our everyday lives are much smaller in size and weaker than LHC, they utilise the same physics principles. So how do they work?

Understanding how Particle Accelerators and Detectors work

Particle accelerators are scientific instruments based on the following principle: colliding particles at high energies leads to the creation of new particles. This is a direct consequence of Einstein’s famous mass-energy relation E=mc2, where the energy of the collision particles is converted to the mass-energy of the new particles. In order to achieve such high energies, accelerators use electric fields to accelerate fundamental particles, such as protons and electrons.

One type of particle accelerator is a linear particle accelerator (linac). As the name suggests, this type accelerates particles in a straight line. Figure 1 As Figure 1 shows, the acceleration electrodes are connected to an alternating supply. The voltage frequency is set such that the particles exiting from each electrode are accelerated through the next gap. In order for the particles to take the same time to travel through each electrode and thus be synchronised with the alternating voltage, the electrodes get successively longer. This is because the particles get faster as they progress through the accelerator and thus need to travel a longer distance in each electrode so that they spend the same time in each electrode.

Once the particles reach the target, it is time for the detector to shine! The purpose of the detector is to accurately record the collision data that are later processed and analysed, sometimes leading to major discoveries like the Higgs Boson in 2012. Typically, a detector has many components each tasked with a specific measurement related to a different aspect of the collision. For example, a given sub-detector is usually designated to measure photons and another is tasked with measuring muons (fundamental particles which are heavier than electrons). Adding to the list energy deposition, charge, momentum and curvature measurements, you can easily end up with a six or seven-layer detector.

Ready to make your own radiation measurements and learn how to analyse data? Hop onto the next tutorial to get a list of all the equipment you will need!

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