RFQD: a decelerating radio frequency quadrupole for the CERN antiproton facility

The RFQD is designed to decelerate antiprotons of momentum 100 MeV/c (kinetic energy 5.33 MeV) down to a kinetic energy variable between ~10 keV and 120 keV. Inside the RFQ body, at ground potential, the rf structure of the four-rod type is mounted on insulating supports. It can be biased between ±60 kV dc to achieve the continuous adjustment of the output energy required by the ASACUSA experiment at the CERN Antiproton Decelerator AD. The different parts of the system are described and the present status reported.