High-energy Electron Beam Ion Trap Research Articles

Rare-earth neutral metal injection into an electron beam ion trap plasma.

We have designed and implemented a neutral metal vapor injector on the SuperEBIT high-energy electron beam ion trap at the Lawrence Livermore National Laboratory. A horizontally directed vapor of a europium metal is created using a thermal evaporation technique. The metal vapor is then spatially collimated prior to injection into the trap. The source's form and quantity constraints are significantly reduced making plasmas out of metal with vapor pressures ≤10(-7) Torr at ≥1000 °C more obtainable. A long pulsed or constant feed metal vapor injection method adds new flexibility by varying the timing of injection and rate of material being introduced into the trap.

A portable high-resolution soft x-ray and extreme ultraviolet spectrometer designed for the Shanghai EBIT and the Shanghai low energy EBITs.

A portable high resolution soft x-ray and extreme ultraviolet (EUV) spectrometer has been developed for spectroscopic research at the Shanghai Electron Beam Ion Trap (EBIT) laboratory. A unique way of aligning the grazing incidence spectrometer using the zero order of the grating is introduced. This method is realized by extending the range of the movement of the CCD detector to cover the zero order. The alignment can be done in a few minutes, thus leading to a portable spectrometer. The high vacuum needed to be compatible with the EBITs is reached by mounting most of the translation and rotation stages outside the chamber. Only one high vacuum compatible linear guide is mounted inside the chamber. This is to ensure the convenient interchange of the gratings needed to enable wavelength coverage of the whole range of 10 to 500 Å. Spectra recorded with one of our low energy EBITs shows that a resolving power of above 800 can be achieved. In the slitless configuration used in this work, we found the resolving power to be limited by the width of the EBIT plasma. When mounted on the Shanghai EBIT which is a high energy EBIT and has a narrower EBIT plasma width, the estimated resolving power will be around 1400 at 221.15 Å.

Laser ablation system for the injection of neutral materials into an electron beam ion trap

We have designed and implemented a laser ablation system to inject neutral material into the EBIT-I and SuperEBIT high-energy electron beam ion trap at the Lawrence Livermore National Laboratory. A laser-generated vapor created from a solid material target was scrubbed of ions prior to injection into the trap in the form of a collimated beam. We used a Q-switched Nd:YAG laser with a pulse duration of 15.7ns full width at half maximum and intensities at the target controllable from 0.035to0.46GW∕cm2. Compared with other injection methods, this pulsed system adds new flexibility including the ability to vary fill trap in both time and quantity and without changing trap or beam parameters. Moreover, it allows us to inject materials that are not readily injected by the standard metal vapor vacuum arc (MeVVA) method. Performance comparisons between the laser ablation system and MeVVA method are presented.

Measurement of the polarization of theK-shell resonance line emission ofS13+andS14+at relativistic electron beam energies

We have measured the polarization of the heliumlike sulfur resonance line 1s2p {sup 1}P{sub 1} {yields} 1s{sup 2} {sup 1}S{sub 0}, and of the blend of the lithiumlike sulfur resonance lines 1s2s2p {sup 2}P{sub 3/2} {yields} 1s{sup 2}2s {sup 2}S{sub 1/2} and 1s2s2p {sup 2}P{sub 1/2} {yields} 1s{sup 2}2s {sup 2}S{sub 1/2} as a function of electron beam energy from near threshold to 144 keV. These lines were excited with the LLNL high-energy electron beam ion trap and measured using a newly modified two-crystal technique. Our results test polarization predictions in an energy regime where few empirical results have been reported. We also present calculations of the polarization using two different methods, and good agreement is obtained.

Extraction of highly charged ions (up to 90+) from a high-energy electron-beam ion trap

The extraction of high-Z high-charge-state ions up to U90+ from a high-energy electron-beam ion trap, the SuperEBIT at Lawrence Livermore National Laboratory, is reported. The SuperEBIT provides a 240 mA electron beam with up to 200 keV of energy. Depending on the operating conditions (pulsed, continuous) and charge state, the number of ions extracted from the SuperEBIT varies between 102 and 105 ions per second under the tested conditions. The ions produced in SuperEBIT are extracted at potentials ranging from 0.5 to 20 keV (continuously variable) to provide highly charged low-emittance ion beams with energies between a few keV and several MeV. The performance of the SuperEBIT as an ion source is described and aspects for future developments and potential applications are discussed.

Position and size of the electron beam in the high-energy electron beam ion trap

In the last decade, many spectroscopic studies have been performed using the electron beam ion trap. Often these measurements rely on the electron beam as an effective slit, yet until now, no systematic study of the position and size of the electron beam under various operating conditions has been made. Here, we present a thorough study of the electron beam's position and size (and thus the electron density) as affected by various operating parameters, and give optimal parameter ranges for operating the device as a spectroscopic source. It is shown that the diameter is constant as the energy is varied, which is important for accurate cross-section measurements.

X-ray Measurements of Charge Transfer Reactions Involving Cold, Very Highly Charged Ions

The magnetic trapping mode of the Livermore high-energy Electron Beam Ion Trap is exploited to study charge transfer reactions between cold (few eV/amu) highly charged ions and gases. By selectively puffing neutral gases and monitoring the x-ray emission, state-selective measurements of the charge transfer reaction channels are possible. The observed K-shell x-ray spectra show prominent emission from high-n levels decaying to the n = 1 ground level, which is enabled by electron capture into states with low orbital angular momentum. A comparison with modeling calculations, therefore, allows a determination of the range of principal and angular momentum quantum numbers involved in the reaction.

Implementation of a normal incidence spectrometer on an electron beam ion trap

Spectroscopic instrumentation is one of the keys to the exploration of high-temperature plasmas. The electron beam ion trap (EBIT) can serve as a tool for precise studies of highly charged ions in the laboratory and can help in setting spectroscopic standards for plasma studies. Recent efforts have focused on investigating the EUV, vacuum ultraviolet (VUV), and UV regimes. We present here the implementation of a 1 m normal incidence spectrometer for use on the Lawrence Livermore National Laboratory high-energy EBIT (Super-EBIT) for spectral analysis of line emission of highly charged ions. Using two different gratings, our study encompasses a wide range of wavelengths spanning the VUV through the visible. Examples of measurements of optical spectra from krypton and argon are given.

Measurements of nuclear parameters of high-Z isotopes performed on a high-energy electron beam ion trap

Spectral measurements of highly charged ions have been performed on the Livermore high-energy electron beam ion trap (EBIT) for determining various nuclear parameters. A value of μ = 4.1267 μ N was inferred for the nuclear magnetic moment from a measurement of the hyperfine transition of 165Ho 66+ in the visible. Values of δ〈 r 2〉 233,238 = −0.432 fm 2 and δ〈 r 2〉 235,238 = −0.250 fm 2 were determined for the isotopic variation of the nuclear charge radius from the energy shift of L-shell transitions in 233 U q+ and 235 U q+ relative to the x-ray line emission from 238 U q+ ions, with q = 86, 87, 88, 89. The accuracy of these measurements equals or exceeds that of earlier measurements relying on different techniques, because the atomic structure of highly charged ions is greatly simplified compared to that of neutral or few-times charged ions. The measurements can be extended to a variety of isotopes from hydrogen to transuranic elements. The latter was demonstrated in the first production of highly charged 249Cf ions in the trap.

Spectral measurements of few-electron uranium ions produced and trapped in a high-energy electron beam ion trap

Measurements of 2 s 1 2 –2 p 3 2 electric dipole and 2 p 1 2 –2 p 3 2 magnetic dipole and electric quadrupole transitions in U 82+ through U 89+ have been made with a high-resolutioon crystal spectrometer that recorded the line radiation from stationary ions produced and trapped in a high-energy electron beam ion trap. From the measurements we infer −39.21 ± 0.23 eV for the QED contribution to the 2 s 1 2 –2 p 3 2 transition energy of lithiumlike U 89+. A comparison between our measurements and various computations illustrates the need for continued improvements in theoretical approaches for calculating the atomic structure of ions with two or more electrons in the L shell.

Structure and Lamb shift of 2s1/2-2p3/2 levels in lithiumlike U89+ through neonlike U82+

The first Doppler-shift-free crystal-spectrometer measurement of stationary highly stripped uranium ions from a high-energy electron beam ion trap is presented. Thirteen 2${\mathit{s}}_{1/2\mathrm{\ensuremath{-}}}$2${\mathit{p}}_{3/2}$ transitions in eight ionization states bteween Li-like ${\mathrm{U}}^{89+}$ and Ne-like ${\mathrm{U}}^{82+}$ are identified and measured with an accuracy as high as 37 ppm, providing benchmarks for testing relativistic correlation and quantum electrodynamic effects in highly charged multielectron ions. A value of 47.39\ifmmode\pm\else\textpm\fi{}0.35 eV is found for the 2${\mathit{s}}_{1/2}$ Lamb shift in Li-like ${\mathrm{U}}^{89+}$, in excellent agreement with theory.

A high-energy electron beam ion trap for production of high-charge high-Z ions

We have developed a new high-energy electron beam ion trap, the first laboratory source of low-energy, few-electron, high-Z ions. We describe the device and report measurements of its performance, including the electron beam diameter, current density and energy, and measurements of the ionization balance for several high-Z elements in the trap. This device opens up a wide range of possible experiments in atomic physics, plasma physics, and nuclear physics.