Design of an energy analyzer for low energy 1⁺charged ion beams at RISP Project

Abstract

A: Accurate measurement of the energy spread with a compact device has been accomplished by developing a new prototype of a retarding field energy analyzer (RFEA). The device is capable of handling all kinds of low energy mono-charged ion beams at RISP Project. Numerical simulations have been performed in order to study and evaluate dependency of RFEA energy resolution to beam emittance, beam energy, beam energy spread, space charge effects, and most significantly the optics system.Simulation results have shown that the use of developed optics system with particular voltage applied on the focusing cylinder and suitable positioning of the retarding grid may lead to high efficiency energy resolutions not exceeding 0.31 eV for beam energy going up to 20 keV. Small errors on the measured energy spread are obtained despite the presence of degradations stemming from various energy resolution dependencies. Typical mono-charged ion beams delivered from ion trap devices, ISOL beam-line and stable ion sources have been studied. The error on the optimum measured energy spread for beams delivered from ion trap devices is 5 ∼ 10% owing to beam emittances. For a larger beam size, delivered from an ISOL beam-line, a larger error occurs on the measured energy spread at around 23.5%. The energy spread of ion beams delivered from stable ion sources with good optical quality relative to the ISOL sources can be measured with an error around 21.7%. This prototype enables accurate measurement of the average beam energy with an error around 1.5 eV per 20 keV beam energy. K: Accelerator modelling and simulations (multi-particle dynamics; single-particle dynamics); Beam Optics 1Corresponding author.

Design of an energy analyzer for highly charged Ions HCI beams

“…The minimization of the shift error on the energy spread measurement, previously mentioned, has been undertaken in this design in using conical form for the second aperture [27]. Numerical simulations have shown an emittance reduction of ∼ 7 times using this aperture system with an opening of 1.4 mm for the two apertures [23].…”

“…This modification led to reach a significant improvement of the energy resolution of less than 1 eV [17,22]. This modification concerns the new generation of RFEA retarding grid [17,19] including those being developed for mono-charged beam of RISP [23]. The latter has an improved optics system carefully designed to provide the highest measurement accuracy and to match the RISP requirement for mono-charged beam [23].…”

“…Its improved design enable to accurately measure the energy spread and the average beam energy for various kind of single charged ion beams. Detailed simulation results and basic design are presented on this reference [23]. The grounded box of such prototype encloses a stack of electrically isolated electrodes, grids and an ion collector, figure 4.…”

“…Using the same optimum design presented in reference [23], with a retarding grid positioned at 4 mm relatively to the focusing cylinder position and with a size of: wire radius a = 1 mm and grid mesh a = 400 µm; the energy spread and average energy measurements efficiency of HCI beam extracted from EBIS charger breeder will be evaluated.…”