Occasionally, I like to mention some of the search terms that bring new visitors to the Sciencebase website. One of those phrases that intrigued me somewhat is this:
creating large plasma bubble between electrodes
Now, I can half imagine it’s someone looking for information about a physical phenomenon, perhaps for a school assignment or maybe a research project. So, what were they looking for?
Plasma is often referred to as the fourth state of matter – after solid, liquid, and gas. It is most similar to a gas, but rather than being made up of neutral atoms or molecules, it is fully ionised. This means that every atom in the gas has been stripped of its electrons. A plasma therefore comprises ions, charged particles, and free electrons (negatively charged particles) rather than atoms or molecules.
We think of it as being the fourth state of matter, but there is an argument for calling it the first state of matter given that plasma is the most common state of matter across the universe, such as the core of stars, nebulae in space, the aurora borealis. That said, we do not tend to encounter it in everyday lives except in specific small-scale circumstance because plasmas form only at extremely high temperatures or in very strong electric fields.
One of those small-scale situations involves the formation of a plasma between electrodes. More specifically, a plasma bubble can form in the electric field between two electrodes as the field strips away electrons away from the atoms of a gas. The size of the plasma bubble depends on a number of factors, including the voltage applied, the distance between the electrodes, and the type of gas that is being ionised by the electric field. Scientists experimenting with plasma bubbles can adjust these parameters, to create plasma bubbles of different sizes and shapes.