Particle Accelerators
Cesar da Silva
Krista Smith
Feb 10, 2022
Optical lenses allow us to access the world of small things.
Practical limit of the visible light is defined by the size of the light wavelength (>250 nm), about 400 times smaller than the hair diameter.
de Broglie’s wavy-like nature of particles
The momentum p of the particle depends on the potential of the electrical field introduced between the anode and cathode.
Electronic microscopes : ~ 1KV
Tanden Van de Graaff in Brookhaven National Lab: 15 MV
The particle needs to have charge to be accelerated by electromagnetic fields.
Proton beams are obtained by stripping electrons from hydrogen atoms.
Heavy ion beams are obtained the same way.
Laser stripping
MeV particle accelerators are very common with uses in
Americium-241 emitting alpha particles in a cloud chamber
Static electrical acceleration is limited in few MeV.
But if the particle cross several accelerator stages higher energies can be achieved.
Linear particle accelerators (LINACS) uses Radio Frequency potentials in different cavities (RF cavities).
Particles comes in bunches and each cavity polarity is synchronized in order to always accelerate the bunch.
Retinobastoma removal in 1957 with a 6 MeV electron beam from a LINAC.
2 miles Sandford Linear Accelerator (SLAC)
in California can reach electrons with energy of 50 GeV
LANL has its own LINAC : LANSC
800 MeV protons
Tours available ….
CYCLOTRONS
Clever idea from Ernest Lawrence : A magnet field makes the particle spiral and cross the same accelerating RF gap several times.
First cyclotron was made in Berkeley. Now we have the Lawrence Berkeley National Lab.
PSI at Switzerland can get 590 MeV protons.
These protons are so fast that they get close to the speed of the light causing relativistic space contractions (Lorentz effects)
SYNCHROTONS
Reach even higher energies and compensate for relativistic effects in the particle trajectory.
A big circular accelerator composed of
The beam is kept inside a small diameter pipe which is easier to maintain the vacuum.
First synchroton operated at LBNL (Bevatron) in 1954 accelerating protons at 6.3 GeV. Anti-protons were discovered in Bevatron a year later.
Cyclotrons were the size of a table. Synchrotrons sizes now can cross country boundaries.
The energies they can reach depend on how big is the ring and how many RF cavities and magnets you can build !
Bevatron – circa 1954
proton + proton collision
Synchrotron particle accelerators can accelerate two particles in opposite directions and collide them reaching much higher energy.
Relativistic Heavy Ion Collider (RHIC) : 200 GeV Au+Au
Large Hadron Collider (LHC) : 14 TeV proton+proton
Deep Inelastic Scattering (DIS)
High-energy electrons have their de Broglie size so small that they can ”see” inside protons. The quark and gluon composition of the proton was explored mostly this way.
The future electron-Ion collider in BNL (EIC) will probe protons and nucleus with resolution up to 1/500 times the size of a proton.
Muons and even neutrino beams have also been used for DIS.
High-energy collisions excite the vacuum and pull out different particles from the different quantum fields on it.
That’s how particles like top quarks and Higgs, which are many times more massive than the proton, are produced.
A beautiful video on particle accelerators :
https://www.youtube.com/watch?v=V_hirIK9eFs
List of accelerator particles:
https://en.wikipedia.org/wiki/List_of_accelerators_in_particle_physics