Research Projects

We propose to study the charge breeding and successive electron impact ionization cross-section in highly charged heavy ions as a function of electron energy in the range 1–5MeV. We also proposed to measure the radiation lifetime of metastable states in such highly charged ions. Highly charged heavy ions can be generated through direct ionization by the incident of highly energetic electrons of constantly varying energies (of a few MeV). To study the metastable radiative lifetime of the lighter ions, we may use the Electron Cyclotron Ion Source to produce such ions. The relative contribution of direct ionization to the cross-section highly depends on the energy of the incident electrons and the nature of the target ions. The precise measurement of the lifetime of metastable states strongly depends on the purity of charge states, ion temperature, and outside influences such as collision with background gases. These challenges can be overcome by trapping the target ions in a small amount of space using Penning traps. The Penning trap provides three-dimensional confinement to charged particles. The ions in the Penning trap are confined in the radial plane by a strong homogeneous axial magnetic field and weak stable electric fields in the axial direction. In essence, the Penning trap acts as an electrostatic tweezer to prepare a well-defined target ion of a specific charge state and to cool them effectively, a prerequisite for studying successive ionization and radiation lifetime. Electron impact ionization cross-sections have been studied at low electron energies (keV range) but not in the range of MeV energies. We aim to study the electron impact ionization cross-section of heavily charged ions in the 1 to 5MeV energy range of electrons. The study will explore the effect of relativistic and quantum electrodynamics on sequential ionization cross-sections and charge breeding times. Experimentally, the metastable transitions in the highly charged systems have first been studied within Electron Beam Ion Trap by emission spectroscopy and later by laser excitation and fluorescence experiments, but the mixture of charge states and the proximity of the hot electron gun filament can complicate the lifetime measurement, in some cases limiting precision. In the proposed experimental setup, these problems are taken care of. The ions are produced externally and trapped at the centre of the Penning trap. An analyzing magnet is used to select specific ions of one particular charge state. To reduce the charge exchange and emission due to collision, the background pressure is minimized through cryo-pumping. Also, to enhance the signal-to-noise ratio of the ion signal, the whole trap electrodes, non-destructive detectors (Axial and cyclotron resonators), and associated pre-amplifier and electronics are cool down to 4-5K using a He-compressed pulsed tube cryocooler.