Plasma is the fourth fundamental state of matter. It is a gas with so much energy the electrons orbiting the atoms have too much energy to remain in orbit, giving us ions and free electrons. Plasma can be artificially generated by heating (a lightning bolt is made of plasma), electromagnetic fields (see fluorescent light bulbs) or radiation.
Plasma at ALPHA
At ALPHA, we manipulate the ingredients to make antihydrogen as plasmas. We use several so-called non-neutral plasmas made up of either positrons, electrons or antiprotons (or mixtures of these). Each of these particle plasmas are prepared separately: the positrons and electrons have no ions to orbit, and the antiprotons have not (yet) got positrons orbiting them.
As charged plasmas, they are easy to manipulate in the vacuum of the experiment. We can confine them with magnetic and electric fields (see Penning Trap). Their charged nature also helps with diagnostic measurements (see Faraday Cup and MCP).
On February 19, 2020, ALPHA published the first investigation of the fine structure of Antihydrogen.
In 2018 the ALPHA Experiment was expanded with the addition of ALPHA-g. Look at timelapse videos to see the massive changes, from installation to beamline!
The ALPHA collaboration has for the first time observed single-photon excitation of antihydrogen atoms from the ground (1S) state to the 2P state using 121nm pulsed laser light - the so-called lyman-alpha line of the Lyman series.