An electron beam ion trap and source for re-acceleration of rare-isotope ion beams at TRIUMF.

Electron beam driven ionization can produce highly charged ions (HCIs) in a few well-defined charge states. Ideal conditions for this are maximally focused electron beams and an extremely clean vacuum environment. A cryogenic electron beam ion trap fulfills these prerequisites and delivers very pure HCI beams. The Canadian rare isotope facility with electron beam ion source-electron beam ion sources developed at the Max-Planck-Institut für Kernphysik (MPIK) reaches already for a 5 keV electron beam and a current of 1 A with a density in excess of 5000 A/cm2 by means of a 6 T axial magnetic field. Within the trap, the beam quickly generates a dense HCI population, tightly confined by a space-charge potential of the order of 1 keV times the ionic charge state. Emitting HCI bunches of ≈107 ions at up to 100 Hz repetition rate, the device will charge-breed rare-isotope beams with the mass-over-charge ratio required for re-acceleration at the Advanced Rare IsotopE Laboratory (ARIEL) facility at TRIUMF. We present here its design and results from commissioning runs at MPIK, including X-ray diagnostics of the electron beam and charge-breeding process, as well as ion injection and HCI-extraction measurements.

Electron and recoil ion momentum imaging with a magneto-optically trapped target.

A reaction microscope (ReMi) has been combined with a magneto-optical trap (MOT) for the kinematically complete investigation of atomic break-up processes. With the novel MOTReMi apparatus, the momentum vectors of the fragments of laser-cooled and state-prepared lithium atoms are measured in coincidence and over the full solid angle. The first successful implementation of a MOTReMi could be realized due to an optimized design of the present setup, a nonstandard operation of the MOT, and by employing a switching cycle with alternating measuring and trapping periods. The very low target temperature in the MOT (∼2 mK) allows for an excellent momentum resolution. Optical preparation of the target atoms in the excited Li 2(2)P3/2 state was demonstrated providing an atomic polarization of close to 100%. While first experimental results were reported earlier, in this work, we focus on the technical description of the setup and its performance in commissioning experiments involving target ionization in 266 nm laser pulses and in collisions with projectile ions.

Polarization and interference effects in ionization of Li by ion impact.

We present initial-state selective fully differential cross sections for ionization of lithium by 24 MeV O8+ impact. The data for ionization from the 2s and 2p states look qualitatively different from each other and from 1s ionization of He. For ionization from the 2p state, to which in our study the m(L)=-1 substate predominantly contributes, we observe orientational dichroism and for 2s ionization pronounced interference which we trace back to the nodal structure of the initial-state wave function.

Ion-lithium collision dynamics studied with a laser-cooled in-ring target.

We present a novel experimental tool allowing for kinematically complete studies of break-up processes of laser-cooled atoms. This apparatus, the 'MOTReMi,' is a combination of a magneto-optical trap (MOT) and a reaction microscope (ReMi). Operated in an ion-storage ring, the new setup enables us to study the dynamics in swift ion-atom collisions on an unprecedented level of precision and detail. In the inaugural experiment on collisions with 1.5 MeV/amu O(8+)-Li the pure ionization of the valence electron as well as the ionization-excitation of the lithium target was investigated.