F. Ullmann

Compact electron beam ion sources/traps: Review and prospects "invited… a…

The Dresden electron beam ion trap (EBIT)/electron beam ion source (EBIS) family are very compact and economically working table-top ion sources. We report on the development of three generations of such ion sources, the so-called Dresden EBIT, Dresden EBIS, and Dresden EBIS-A, respectively. The ion sources are classified by different currents of extractable ions at different charge states and by the x-ray spectra emitted by the ions inside the electron beam. We present examples of x-ray measurements and measured ion currents extracted from the ion sources at certain individual operating conditions. Ion charge states of up to Xe(48+) but also bare nuclei of lighter elements up to nickel have been extracted. The application potential of the ion sources is demonstrated via proof-of-concept applications employing an EBIT in a focused ion beam (FIB) column or using an EBIT for the production of nanostructures by single ion hits. Additionally we give first information about the next generation of the Dresden EBIS series. The so-called Dresden EBIS-SC is a compact and cryogen-free superconducting high-B-field EBIS for high-current operation.

Production of bare argon, manganese, iron and nickel nuclei in the Dresden EBIT

Abstract The production of highly charged argon, manganese, iron and nickel ions in a room-temperature electron beam ion trap (EBIT), the Dresden EBIT, has been investigated by means of energy dispersive X-ray spectroscopy of the direct excitation (DE) and radiative recombination (RR) processes. To derive the charge state distributions of the ions in the trap, direct excitation and radiative recombination cross-sections were calculated at electron energies of 8 and 14.4 keV. Based on these theoretical cross-sections and the measured X-ray spectra, the ion densities and the absolute number of ions, which are trapped in the electron beam, are determined for argon, manganese, iron and nickel. Emphasis has been paid to the highly charged ions, including the helium-like and hydrogen-like ions and bare nuclei. In the case of iron we also determined the contributions from lower ionization stages from DE transition lines. It is shown, that in the Dresden EBIT elements at least up to nickel can be fully ionized. Beside energy dispersive spectroscopy it is shown for iron by wavelength dispersive X-ray spectroscopy that with a comparably high gas pressure in the order of 10−8 mbar carbon-, boron-, beryllium-, lithium- and helium-like iron ions can be produced.

Highly charged metal ions produced from volatile organometallic compounds in a room temperature electron beam ion trap

A MIVOC system as it has been applied to several electron cyclotron resonance ion sources has been used to load a room temperature electron beam ion trap with a selection of different metals. X-ray measurements have demonstrated the ability of this method to produce highly charged ions for a large number of elements in a simple way and at low costs, which is favored by the low consumption rate of the used substances and operation of the ion trap at room temperature. The analysis of x-ray spectra measured with a Si(Li) semiconductor detector which is based on atomic structure calculations indicate the production of Mn23+, Fe25+, Ge30+, and Sn44+ ions.

Dresden EBIT: Results and perspectives

The Dresden electron-beam ion trap (EBIT) is a long-term stable room-temperature EBIT working without any cryogenic techniques. Spectroscopic investigations have shown that in the Dresden EBIT bare nuclei at least up to nickel can be produced as well as helium-like ions from elements such as krypton or germanium and neon-like ions from elements such as xenon or iridium. The output of quantum radiation from highly charged ions trapped in the Dresden EBIT is high enough that wavelength-dispersive spectroscopic investigations are possible. Up to now, two devices (Dresden EBIT I and Dresden EBIT II) have been built up. Results derived on Dresden EBIT II demonstrate that it is possible to produce the described apparatus in any number. Thus, it opens up a way also for small laboratories to employ highly charged ions in their investigations.

Highly charged ions produced in a warm electron beam ion trap

A compact electron beam ion trap (WEBIT) working at room temperature without any cryogenic components is described and experimentally investigated. The trap design is based on permanent magnet technology. For the formation of the electron beam a Pierce electron gun equipped with a cathode of high emissivity is used. The ion trap is created by a compressed electron beam passing through a drift tube system consisting of three sections with corresponding electrical trap potentials. X-ray spectra measured with a Si(Li) semiconductor detector indicate the production of Kr34+, Xe44+, Ce48+, Ir64+, and Hg66+ ions.

The Dresden EBIT: An ion source for materials research and technological applications of low-energy highly charged ions

Abstract We report on a room temperature electron beam ion trap (DEBIT: Dresden EBIT). The construction of the DEBIT allows it to produce dense electron beams with current densities of at least 500 A cm −2 and an ionization factor of 5×10 21 cm −2 for electron beam energies up to 15 keV. Ions like Fe26+, Kr34+, Xe49+ and Hg70+ have been detected by X-ray spectrometry. The developed device has a high potential for investigations in nanomechanics, potential sputtering, information technology, ion beam lithography, etc., as it was demonstrated by different authors in studies utilizing a cryogenic EBIT or ECR ion sources. To enable adequate investigations a first compact ion extraction system for the DEBIT is described.

Properties of the electron beam in a room-temperature electron beam ion source investigated by position sensitive x-ray detection

The evolution of the charge state distribution inside an electron beam ion source or trap (EBIS/T) is determined by interactions of the electron beam with the ions in the trap region. Hence, detailed information about the electron beam is required for evaluations of spectroscopic and ion extraction measurements performed at EBIS/T facilities. This article presents the results of investigations on the electron beam properties of an ion source of the Dresden EBIS type. For the first time theoretical predictions of the shape of the beam were tested for a noncryogenic EBIS working with low magnetic flux densities provided by permanent magnets. Position and width of the electron beam were measured at different electron energies showing an oscillation in the beam structure. At an energy of E(e)=16 keV and an emission current of I(e)=30 mA the beam is compressed to a radius of r(e)=57 mum (80% current). This refers to an average current density of j(e)=232 A/cm(2).

Observation of 3d metal ion charge state distributions in the Dresden EBIT

Ion charge states of 3d metal ions in the electron beam of the Dresden electron beam ion trap (EBIT), a room-temperature EBIT, are determined by x-ray spectroscopy. It is shown that ions of highest charge states as bare nuclei and hydrogen- and helium-like ions can be produced with ion densities of about 105 cm−3 up to 108 cm−3 in the trap. The Dresden EBIT operates at a typical working gas pressure region of 10−8 mbar down to 10−10 mbar. Thus the influence of the realized working gas pressure on the derived ion charge state distribution is investigated by model calculations.

A novel room temperature electron beam ion trap for atomic physics and materials research

Abstract Highly charged ions are used in basic investigations to study problems in atomic and plasma physics. Further on, the application of highly charged ions in materials research and other fields as nanomechanics and information techniques grew significantly in the last years. In the present paper, we report on results derived with a warm electron beam ion trap (WEBIT) that works without any cryogenic equipment. A special source construction allows to generate dense electron beams at room temperature with a current density of up to 240 A cm−2 and an acting ionization factor of (2⋯5)×10 21 cm −2 . Ions like Ar17+, Xe44+ and Ir65+ were detected by X-ray spectroscopy. A charge capacity of about 8×107 elementary charges of the trap is estimated.

Dresden electron beam ion trap: Status report and next developments

The Dresden EBIT is a room-temperature EBIT producing highly charged ions for x-ray spectroscopy as well as for materials modifications and other applications. In the past we have demonstrated the production of ions such as Ar18+, Fe26+, Kr35+, Xe46+, and Ir67+. Here we give a report on the further development of this ion source to increase the electric trap capacity involving the production of a greater amount of highly charged ions.