Speaker
Description
The BASE collaboration at the antiproton decelerator facility of CERN conducts antiproton g-factor and charge-to-mass ratio measurements with precisions on the parts per billion to parts per trillion level respectively. So far, we have measured the antiproton g-factor to 1.5 ppb and the antiproton’s charge-to-mass ratio to 69 ppt respectively [Smorra et al. 2017, Ulmer et.al. 2015]. Limitations in the precision of these measurements stem from particle cooling statistics, systematic shifts imposed by magnetic field inhomogeneities and frequency measurement noise.
The recent shutdown of CERN (LS2), which included the switchover from the AD to ELENA, provided ample time to implement upgrades to fully take advantage of the exciting new capabilities of ELENA, to address precision limitations, and to advance the limits of our recent precision measurements by at least a factor of 10.
The first of these upgrades is a new multi-trap stack, which also includes a whole new dedicated cooling trap. This cooling trap is designed such, that the resistive cooling of the particle's cyclotron mode is being accelerated by a factor of approximately 60, cutting down the preparation time to achieve temperatures that allow single spin-flip resolution for g-factor measurements from several hours to only a few minutes. Along with the existing analysis trap, the cooling trap features an inhomogeneous magnetic field, which enables efficient energy evaluation and tracking via the continuous Stern-Gerlach effect.
This inhomogeneity, however, is detrimental for the operation of the precision trap, which is supposed to have a very homogeneous field. So far, the precision trap was only shielded from this field inhomogeneity by physical distance from the inhomogeneous traps, however, now a newly designed superconducting shielding and shimming system was implemented to cut out influences from both the other traps as well as from imperfections of the superconducting magnet.
This system is estimated to suppress previous dominant systematic shifts of the cyclotron frequency by more than a factor of 100.
Finally, to accommodate the low-energy ELENA beam, a new degrader system was designed and implemented. The degrader's ultra-thin foils in combination with its support structure provide an acceptance of 17 percent while being capable of separating the inside of the experiment from pressures up to room conditions.
This contribution will go into each of these improvements as well as into the development of new detection systems and resistive coolers for the cyclotron mode in both the precision trap and the cooling trap.
