Common Ion Source Research Articles

Foundations of plasmas as ion sources

An overview of low temperature, partially magnetized ion sources is presented. This class of devices is broadly characterized by plasma densities below 1019 m−3, electron temperatures below 100 eV, and magnetic field strength tailored such that electrons are magnetized whereas ions are not. The overarching approach is pedagogical, targeting an audience that does not necessarily have an expertise in low temperature devices. A tutorial is presented on the basic physics of operation of common ion sources including an overview of standard methods for plasma generation and acceleration. Typical diagnostics and common uses of these plasma sources are also reviewed. Special attention is given to applications in plasma propulsion and materials processing. This class of ion sources is then discussed in the context of the current state of the field, key technical and scientific challenges, and future prospects.

Simultaneous multicomponent spectrophotometric monitoring of methyl and propyl parabens using multivariate statistical methods after their preconcentration by robust ionic liquid-based dispersive liquid–liquid microextraction

A powerful and efficient signal-preprocessing technique that combines local and multiscale properties of the wavelet prism with the global filtering capability of orthogonal signal correction (OSC) is applied for pretreatment of spectroscopic data of parabens as model compounds after their preconcentration by robust ionic liquid-based dispersive liquid–liquid microextraction method (IL-DLLME). In the proposed technique, a mixture of a water-immiscible ionic liquid (as extraction solvent) [Hmim][PF6] and disperser solvent is injected into an aqueous sample solution containing one of the IL’s ions, NaPF6, as extraction solvent and common ion source. After preconcentration, the absorbance of the extracted compounds was measured in the wavelength range of 200–700nm. The wavelet orthogonal signal correction with partial least squares (WOSC-PLS) method was then applied for simultaneous determination of each individual compound. Effective parameters, such as amount of IL, volume of the disperser solvent and amount of NaPF6, were inspected by central composite design to identify the most important parameters and their interactions. The effect of pH on the sensitivity and selectivity was studied according to the net analyte signal (NAS) for each component. Under optimum conditions, enrichment factors of the studied compounds were 75 for methyl paraben (MP) and 71 for propyl paraben (PP). Limits of detection for MP and PP were 4.2 and 4.8ngmL−1, respectively. The root mean square errors of prediction for MP and PP were 0.1046 and 0.1275μgmL−1, respectively. The practical applicability of the developed method was examined using hygienic, cosmetic, pharmaceutical and natural water samples.

Modified ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction followed by atomic absorption spectrometry for trace determination of zinc in water and food samples

We report on a new method for the microextraction and determination of zinc (II). The ion is accumulated via ionic-liquid cold-induced aggregation dispersive liquid-liquid microextraction (IL-CIA-DLLME) followed by flame atomic absorption spectrometry (FAAS). The ionic liquid (IL) 1-hexyl-3-methylimidazolium hexafluorophosphate is dispersed into a heated sample solution containing sodium hexafluorophosphate as a common ion source. The solution is then placed in an ice-water bath upon which a cloudy solution forms due to the decrease of the solubility of the IL. Zinc is complexed with 8-hydroxyquinoline and extracted into the IL. The enriched phase is dissolved in a diluting agent and introduced to the FAAS. The method is not influenced by variations in the ionic strength of the sample solution. Factors affecting the performance were evaluated and optimized. At optimum conditions, the limit of detection is 0.18 μg L−1, and the relative standard deviation is 3.0% (at n = 5). The method was validated by recovery experiments and by analyzing a certified reference material and successfully applied to the determination of Zn (II) in water and food samples.

Feasibility of high power refractory metal-foil targets for EURISOL

EURISOL foil-targets have to withstand a primary proton beam of 1 GeV kinetic energy and up to 100 μA beam current. These foil targets will be based on previous high-power target concepts, i.e. the RIST target [J.R.J. Bennett et al., Nucl. Instrum. Meth. Phys. Res. B 126, 117 (1997)] or high power targets used at TRIUMF [P. Bricault et al., Nucl. Instrum. Meth. Phys. Res. B 204, 319 (2003), M. Dombsky et al., Nucl. Instrum. Meth. Phys. Res. B 204, 191 (2003)]. A single target unit is capable of dissipating up to 25 kW, hence, several target units can be merged together by individual transfer lines to one common ion source. The single target units will be irradiated by a proton beam in a time sharing mode to distribute the primary proton beam current to the individual target units. In this feasibility study the necessary properties of high-power foil targets are discussed and the requirements to design a foil target according to the proton beam parameters [CITE] for the future EURISOL facility are given.

Collision physics in ECR and EBIS/T

Today’s most common ion sources for the production of highly charged ions, the electron cyclotron resonance (ECR) source and the electron-beam ion source and trap (EBIS/T) differ very much in their construction, while the basic physical processes are the same in both sources. In both sources highly charged ions are created by electron impact in a stepwise ionization process and trapped in an electrostatic potential well. As a consequence, heating of ions by small angle Coulomb collisions with fast electrons takes place in a similar way for both sources. A controversy of the past on the physical nature of the benefit of gas mixing in ECR now has disappeared, explaining the gas mixing effect as mainly due to ion cooling by ion–ion collisions, which has been observed in EBIT and called “evaporative cooling.” In spite of all these common processes, the resulting charge state spectra look very different for both source types, typically narrow for EBIS and wide for EBIT and ECR. This is a result of radiative recombination and charge exchange, limiting the buildup of higher charge states under steady state conditions in ECR ion sources and in EBIT.

Multiple spacecraft observations of energetic ions during a major geomagnetic storm

Orders of magnitudes increases of MeV ion intensities were measured by the POLAR spacecraft near the dayside magnetopause/magnetosheath boundary layers on May 4, 1998. From 6:00 to 12:30 UT, the Dst index reached negative values of -123 nT to -216 nT, which characterized a major geomagnetic storm period. During this period, the WIND spacecraft was about 213 RE upstream from the Earth, the GEOTAIL was in the post dusk magnetosheath, the INTERBALL-Tail was near the bow shock, and the POLAR traveled in its dayside outbound orbit from the high altitude cusp to the magnetosheath boundary layer. No comparable energetic particle flux was observed by WIND. The energetic ion fluxes measured by POLAR in upstream of the cusp were higher than that measured by both INTERBALL and GEOTAIL. The flux variations at Polar and Interball were similar, indicating a common ion source. Furthermore, INTERBALL responded to the variations later than POLAR, suggesting POLAR was closer to the source. Simultaneous multiple spacecraft observations thus suggest a likely source of substantial particle energization exists in the cusp region.

100 years of ion beams: Willy Wien's canal rays

When Goldstein's report on the "positive light" (or what is known as "Kanalstrahlen", canal rays) in gas discharge tubes first appeared in 1886, Willy Wien had just finished his thesis at the Helmholtz Institute in Berlin. Eleven years later he performed his first experiments on canal rays and found that they consisted of inert, charged and neutral particles. The charged component in canal rays could be de ected using electric and magnetic fields, enabling Wien to roughly determine their mass-to-charge ratio. Improving vacuum conditions and detection efficiency, Thomson finally resolved the lightest constituents of canal rays: the hydrogen ions H+ and H2+. This marked the beginning of mass spectrometry. The first mass spectrographs were parabola-image instruments being used by Thomson to discover isotopes. Until about 1923, canal rays became the most common ion source. Also Aston used canal rays as an ion source for the first double focussing mass spectrometer. - Wien continued his work on canal rays up to the end of his life (he died in 1928). He investigated their interaction with matter, i.e. the mean free path of canal rays in gases with respect to charge exchange and atomic excitation. His particular interest was addressed to the physics of light emission by canal rays, such as the line spectrum and the splitting of these lines in magnetic and electric fields, the Doppler effect and lifetimes.