High Precision High Voltage Divider And Its Application To The Study Of Resonant Energy Of Dielectronic Recombination

Electron beam ion traps (EBIT) are excellent devices for studying highly charged ions. It takes smaller space and lower cost than particle accelerators. Dielectronic recombination of highly charged ions is very important in astrophysics and hot plasmas, because of its large resonant strength. Since the energy spread of electron beam is as small as several tens of eV, both as ion source and photon source, EBITs are the very tools to study dielectronic recombination of highly charged ions, and to disentangle different atomic processes in hot plasmas.The work attempts to build a new approach to precisely measure the electron energy during electron-ion collision process, and its application to the investigation of the resonant energy KLL dilectronic recombination of highly charged xenon ions. To measure the KLL resonant acceleration voltage of highly charged xenon ions, we designed and constructed a high voltage divider with high precision and high stability. And built a corresponding data acquisition system with graphic-user interface. We adopted high precision, low temperature and voltage coefficient thick film resistors, and built a temperature regulation box to reduce the fluctuation of temperature to as low as 0.025°C, so as to minimize the dividing ratio uncertainty caused by temperature fluctuation. Besides, we measured the resistance change of the resistors when different voltage were applied, i.e. the voltage coefficient of resistors with sophisticated digital multi-meters. After analyzing the mechanism of voltage coefficient, we fit the data with a correction curve. And finally we tested the dividing ratio and time delay of the divider, which shows a precision of less than 1 ppm. The output signal from the divider and the photon detector were recorded by a data acquisition system, which was programmed with visual C++. The system realized the functions of data acquisition, realtime display and simple data analyze ect.Besides the acceleration voltage, the space charge of the electron beam, neu- tralization of ion cloud, and geometry effect from drift tubes also affect the electron beam energy. To measure these effects quantitatively, we measured the acceleration voltage of KLL dielectronic recombination of xenon ions with different beam current, and then fit the data with a formula that combine physical and mathematical deduction, to extrapolate the acceleration voltage when the beam current is zero. So we can separate the space charge effect from the beam energy. For the geometry effect, we simulated the equipotential profile of the drift tues with Simion program. Finally summed all these factor together, we got the precise KLL resonant energy. And we compared our experimental result with the calculation based on relativistic configuration interaction (RCI), relativistic many-body perturbation theory (RMBPT), and multi-configuration Dirac-Fock theory (MCDF) theory.