Physics at CERN's Antiproton Decelerator

2013

The Antiproton Decelerator of CERN began operation in 1999 to serve experiments for studies of CPT invariance by precision laser and microwave spectroscopy of antihydrogen ($\bar{\rm H}$) and antiprotonic helium ($\bar{p}{\rm He}^+$). The first 12 years of operation saw cold $\bar{\rm H}$ synthesized by overlapping clouds of positrons ($e^+$) and antiprotons ($\bar{p}$) confined in magnetic Penning traps. Cold $\bar{\rm H}$ was also produced in collisions between Rydberg positronium atoms and $\bar{p}$. Ground-state $\bar{\rm H}$ was later trapped for up to $\sim 1000$ s in a magnetic bottle trap, and microwave transitions excited between its hyperfine levels. In the $\bar{p}{\rm He}^+$ ato…