Silver Membrane Filters Play a Part in Antimatter Trapping

If you fastidiously watch “Through the Wormhole” like I do, chances are you’ll find this application for silver membrane filters fascinating – they’re being used to assist in the collection of antimatter! Now if your main reference for antimatter is a certain Dan Brown novel, you should know that separating and collecting antimatter is a much, much more difficult process than the entertainment industry would have you believe. In fact, “If you take all the antimatter produced in the history of the world and annihilated it all at once, you wouldn't have enough energy to boil a pot of tea,” according to Harvard physicist Gerald Gabrielse. Professor Gabrielse is a leader in antimatter trapping methodology and a co-author of the paper Pumped Helium System for Cooling Positron and Electron Traps to 1.2 K, which details how our filters are used to trap antimatter.

Antimatter is composed of the exact opposite particles (particles of the same mass but opposite electrical charges) as its traditional counterpart. So whereas a hydrogen atom is made of one electron and one proton, an antihydrogen atom (called H-Bar) is comprised of a positron and an antiproton. When antimatter comes into contact with matter, even air, both particles annihilate and release energy in the form of photons (light particles) and/or radiation. Because of the extreme instability of antimatter, one of the major challenges with studying it is gathering enough of the material in a lab. To store any amount of antimatter requires an extremely powerful vacuum to prevent it from coming into any contact with matter. To this end, scientists are experimenting with all manner of “traps” in order to separate and analyze the antimatter.

It is one of these traps that pure silver membranes have found a role in the antimatter collection process. The paper referenced above explains how in order to collect antihydrogen the scientists must cool the trap apparatus to temperatures close to absolute zero. To cool the apparatus to such an extreme degree the scientists here use liquid helium (which is about -269°C), this is also where the silver filters come into play. In order to remove any impurities that could cause clogging in the apparatus, the liquid helium is twice filtered through silver filters, first through a 5 micron filter and then a 3 micron filter before continuing through the pumping system.

A popular misconception about antimatter is that it has potential as an alternative energy source. On his website Professor Gabrielse points out that “No antimatter energy source will ever be possible since it takes much more energy to make antimatter than can ever be recovered from antimatter annihilation…Our motivation for trapping antimatter is to study is basic properties and to compare them with the properties of ordinary hydrogen atoms.” So while this research isn’t going to solve our energy problems, it could help physicists answer some of the biggest mysteries regarding the makeup of the universe.

That last part would sound better coming from Morgan Freeman…