The CUSP trap consists of the unique combination of a superconducting anti-Helmholz coil and a stack of ring electrodes. The CUSP trap provides the minimum B field configuration but still maintaining axial symmetry. Due to this symmetry, the CUSP trap realizes stable handlings of both antiprotons and positrons such as trapping, cooling, and mixing.


The so-called nested well configuration to trap simulatiously an positron and an antiproton cloud is adopted as shown in the figure below. The confinement well for positron plasma is nested in the well for antiproton cloud.

Formed antihydrogen atoms in LFS (low field seeking) states are preferentially focused along the axis whereas those in the HFS (high field seeking) states are defocused, resulting in the formation of an intesity enhanced spin-polarized antihydrogen beam. This is a novel feature of the CUSP trap. By using this antihydrogen beam, we adopt the famous Rabi-technique for the microwave spectroscopy.