The coldest antiprotons ever produced–which reached 9 kelvin–were cooled with a tried-and-true method for neutral atoms. The result is an essential step on the road to studying antihydrogen.
I give an overview of experimental and theoretical results for antiproton and antihydrogen scattering with atoms and molecules (in particular H, He). At low energies ([Formula: see text]1 keV) there are practically no experimental data available. Instead I compare the results from different theoretical calculations, of various degrees of sophistication. At energies up to a few tens of eV, I focus on simple approximations that give reasonably accurate results, as these allow quick estimates of collision rates without embarking on a research project.This article is part of the Theo Murphy meeting issue 'Antiproton physics in the ELENA era'.
ATRAP has made many important improvements since CERN's Antiproton Decelerator (AD) was restarted in 2006. These include substantial increases in the number of positrons (e+) and antiprotons (Pbars) used to make antihydrogen (Hbar) atoms, a new technique for loading electrons (e−) that are used to cool Pbars and e+, implementation of a completely new, larger and more robust apparatus in our second experimental zone and the inclusion of a quadrupole Ioffe trap intended to trap the coldest Hbar atoms produced. Using this new apparatus we have produced large numbers of Hbar atoms within a Penning trap that is located within this quadrupole Ioffe trap using a new technique which shows promise for producing even colder atoms. These observed Hbar atoms resolve a debate about whether positrons and antiprotons can be brought together to form atoms within the divergent magnetic fields of a quadrupole Ioffe trap.