How does the Large Hadron Collider create ions?

This week, the LHC starts colliding lead ions after almost a full year of proton-proton collisions. But how are lead ions at the LHC created?

During normal run, protons originate from a hydrogen bottle. A strong electric field is applied to the gas to separate electrons and protons. The protons then continue to be accelerated. However, lead is naturally in a solid state and has 82 electrons which cannot be easily removed. We need a different system to strip electrons from lead atoms. The LHC uses a specific isotope of lead - 208Pb (it has 82 protons and 126 neutrons). Natural lead contains multiple isotopes, mainly 204Pb, 206Pb, 207Pb and 208Pb. To avoid a contaminated sample, the ion source for the LHC is a piece of pure solid 208Pb.

Lead is put into an oven, heated to 800°C and vaporised. During stable beam conditions, approximately 2 milligrams of lead are consumed per hour of operation. The lead vapour is ionised (process that separates the electrons from the nucleus) to become a plasma. The ions are then extracted from the plasma and accelerated. The process of creating lead ions is carried out by Linac 3. Then, ions continue into the Low Energy Ion Ring, the Proton Synchrotron, the Super Proton Synchrotron and the Large Hadron Collider. Each step increases the energy of the ions until they reach a collision energy of over 1 TeV per nucleus.

What are physicists hoping to achieve by colliding lead ions?

When our universe was very young (10⁻¹² - 10⁻⁶ seconds after the Big Bang, also called the quark epoch), it was very dense and very hot - a state called the quark-gluon plasma. The particles present were quarks, leptons and their antiparticles. By colliding ions, we can recreate this quark-gluon plasma and study this period when the fundamental forces such as gravitation, electromagnetism, strong and weak interactions as we know them now emerged.