Synthesis of cold and trappable fully stripped highly charged ions via antiproton-induced nuclear fragmentation in traps

The study of radioisotopes as well as of highly charged ions is a very active and dynamic field. In both cases, the most sensitive probes involve species trapped in Penning or Paul traps after a series of production and separation steps that limit the types and lifetimes of species that can be investigated. We propose a novel production scheme that forms fully (or almost fully) stripped radionuclei in the form of highly charged ions (HCIs) directly in the trapping environment. The method extends the range of species, among them radioisotopes such as ${}^{21}\mathrm{F}, {}^{100}\mathrm{Sn}$, or ${}^{229}\mathrm{Th}$, that can be readily produced and investigated and is complementary to existing techniques.

Figure 1

Periodic table with the electron affinity of each element in eV. The elements highlighted in yellow can be produced as an elemental anion current from a Cs sputter source [15].

Figure 2

Production rates for nuclear fragments produced in the process of annihilation of captured antiprotons by ${}^{197}\mathrm{Au}$.

Figure 3

Charge-weighted energy distribution (in keV/$Q$) for different species produced from ${10}^6{\overline{p}}^{197}\mathrm{Au}$ assuming full electron stripping in the process. Same events as in Fig. 2.

Figure 4

Charge-weighted energy distribution (in keV/$Q$) of several isotopes of Au ($Z=79$), Pt ($Z=78$), and Ir ($Z=77$) produced from ${10}^6{\overline{p}}^{197}\mathrm{Au}$. The bands represent the region of partial stripping of electrons with an upper limit based on Xe, with remaining $Z-54$ bound electrons.

Figure 5

Production rates for trappable stripped fragments with energies below 10 keV/e produced from elements such as ${}^{235}\mathrm{U}, {}^{197}\mathrm{Au}$, and ${}^{19}\mathrm{F}$. The technique favors evaporation of surface neutrons over protons. The boxes on top of the lifetime chart indicates the region of isotopes accessible via antiprotons.

Figure 6

Formation rate of protonium predicted from the interaction of trapped antiprotons with a beam of ${\text{H}}^{-}$ ions. The rate is calculated assuming the anion beam and the antiproton interacting on the total area of $S=0.785{\mathrm{cm}}^2$. The legend labels indicate the collision energy $E$ in the center-of-mass frame with the corresponding interaction cross section $\sigma$.