Leaky ion extraction method for dielectronic recombination strength measurements at electron-beam ion traps

Abstract

There are a number of mechanisms via which ions and electrons interact in a plasma, but by far one of the most important is through dielectronic recombination (DR). This is a resonant process through which an ion can capture a free electron and decrease its charge by one unit. Cross sections or strengths for this process are of vital importance in the modeling of hot plasmas and hence any advance in measurement or calculation procedures for obtaining DR data is of great importance. The work presented here examines the underlying basis of a newly developed method based on leaky mode ion extraction from an electron beam ion trap (EBIT), for relatively quickly obtaining DR strengths. The development attains to use the ratio of the leaked ions in adjacent charge states, i.e., the initial and final charge states of a DR process, to obtain the strengths preassuming that this ratio is the same as that of the ions remaining inside the EBIT trap. This work shows this assumption to be false. Hence DR strengths measured using leaked ions may be subject to error. But this work also reveals that the difference between this ratio and the one for trapped ions is insensitive to most of the experimental conditions, which means reliable DR strengths can still be obtained by leaky mode ion extraction if proper corrections are applied. An example is shown in this paper where after correction of some experimental results for DR strengths, obtained using the leaky mode, excellent agreement with corresponding theoretical calculations is obtained.

KLLdielectronic recombination process of He-like to O-like xenon ions

“…In the case of the Li-like iodine ions, which are next to xenon in the periodic table, our calculated result with the Breit interaction [14] is smaller than Watanabe's [11] experimental result by about 20%, while is only smaller than Kavanagh's [12] experimental result by about 7.7%. Recently, the experimental results of Watanabe et al [11] were corrected by Zhang et al [34] The corrected results accord very well with our results. [14] The reason why such large differences appear in the case of the Li-like xenon ions has not been clear until now.…”

Diagnostic measurements of CUEBIT based on the dielectronic resonance process

“…In summary we can claim that the relative change in the overall emitted DR x-ray intensity can be interpreted as the change in the number of He-like ions in the trap as has been previously discussed in e.g. [19].…”

AnisotropicLMNdielectronic resonances from ratios of magnetic-dipole lines

“…One method utilizes extraction of ions at different beam energies and analysis of their abundances [9,11,16]. It is not unusual, however, that the measured ionization distributions differ from the originally produced abundances inside the trap, and thus additional corrections may be required [17]. Another method is based on EBIT beam ramping [7].…”