Design and characterisation of an antiproton deceleration beamline for the PUMA experiment

Abstract

We report on the design and characterization of an antiproton deceleration beamline, based on a pulsed drift tube, for the PUMA experiment at the Antimatter Factory at CERN. The design has been tailored to high-voltage (100 kV) and ultra-high vacuum (below $10^{-10}$ mbar) conditions. A first operation achieved decelerating antiprotons from an initial energy of 100 keV down to ($3898\pm 3$) eV, marking the initial stage in trapping antiprotons for the PUMA experiment. Employing a high-voltage ramping scheme, the pressure remains below $2\cdot 10^{-10}$ mbar upstream of the pulsed drift tube for 75% of the cycle time. The beamline reached a transmission of ($55\pm 3$)% for antiprotons decelerated to 4 keV. The beam is focused on a position sensitive detector to a spot with horizontal and vertical standard deviations of $\ddot{I}{ƒ}_{\mathrm{horiz}}$ = ($3.0\pm 0.1$) mm and $\ddot{I}{ƒ}_{\mathrm{vert}}$ = ($3.8\pm 0.2$) mm, respectively. This spot size is within the acceptance of the PUMA Penning trap.