Shanghai EBIT Research Articles

Observation of indirect ionization of W7+ in EBIT plasma

SynopsisIn this work, visible and EUV spectra of W7+ have been measured using the high-temperature super-conducting electron-beam ion trap at the Shanghai EBIT laboratory under extremely low-energy conditions. The relevant atomic structure has been calculated by using the flexible atomic code package and the GRASP2K code. A hypothesis for the charge-state evolution of W7+ is proposed based on our results. The occurrence of W7+ ions results from indirect ionization caused by stepwise excitation between some metastable states of lower-charge-state W ions, at the nominal electron beam energy of 59 eV.

A high precision flat crystal spectrometer compatible for ultra-high vacuum light source.

We report on a flat crystal spectrometer (FCS) featuring a differently pumped rotary feedthrough and double detectors connected to a crystal chamber by extendable bellows built at the Shanghai EBIT Laboratory. It was designed to overcome defects such as oil contamination, little distance from the detector to the crystal and others of an early FCS equipped at the same laboratory, but still keeps a large detectable angle range of detectors and brings new features and functions such as the Bond method measurement and double-crystal measurement which are based on the two-detector and large bellow design. This new FCS could cover an energy range of measurable photons from 570 eV to 10 keV and reach a vacuum better than 6 × 10-10 Torr and thus is compatible for coupling directly to ultra-high vacuum light sources. Off-line tests of the FCS were undertaken where Kα x-rays from solid titanium were measured and analyzed. Measurements of transitions in He-like argon ions were performed when the spectrometer was directly connected to Shanghai EBIT, and the width of the x-ray source was monitored simultaneously using an x-ray slit imaging system. An observed spectral line broadening was 0.869 eV corresponding to a resolving power of 3600, including Doppler broadening of the x-ray source. Taking account of the measured source width, we made simulations using the SHADOW 3 code and got a nominal resolving power of 6500 for the spectrometer. This high nominal resolving power is due to a longer distance from the crystal to the detector, comparing with that in the early FCS.

Photorecombination studies of highly charged tungsten ions at Shanghai EBIT

In this paper, we report studies on photorecombination (PR) processes for highly charged W ions. The experiment was performed at Shanghai electron beam ion trap by employing a fast electron beam-energy scanning technique. The KLL dielectronic recombination (DR) resonance strengths for He- up to O-like W ions were determined. The strong interference effect between DR and radiative recombination (RR) was observed and the Fano factor, which measures the interference degree, was determined for the main resonances of ground state He-, Be-, B-, C-, N-, and O-like W ions. In addition, we show experimentally that an autoionizing state can have both Fano and Lorentzian behavior naturally, depending on the processes involved. A fully relativistic configuration interaction method implemented in the flexible atomic code was employed to calculate DR, RR processes and also the inference effect.

Observation of an extremely-long-lived metastable level in a Ti-like system via an L -shell dielectronic recombination measurement in highly charged 3dn ions of tungsten

In this paper we report the L-shell dielectronic recombination measurement in highly charged $3{d}^{n}$ ions of tungsten by employing a fast electron beam-energy scanning technique at Shanghai EBIT. The studies of the LMM DR resonance strengths of Ar-like up to Mn-like tungsten were implemented through the experiment as well as a fully relativistic configuration interaction method in the flexible atomic code. In the analysis of DR spectrum, an isolated resonant peak was discovered coming from the DR processes via an extremely-long-lived metastable level in a Ti-like system. This work indicated the population of this Ti-like metastable level in the present EBIT plasma condition was as large as 45%.

Study on KLL dielectronic recombination for highly charged tungsten ions at Shanghai EBIT

SynopsisThis work reported both experimental and theoretical study on KLL dielectronic recombination for He-like up to O-like tungsten ions, including resonance levels, resonance strengths and interference effect.

The status of the micro-calorimeter at Shanghai EBIT

We present an overview of recent work on the micro-calorimeter at the Shanghai EBIT laboratory. The micro-calorimeter was established under a collaboration between the Shanghai EBIT laboratory and the Smithsonian Astrophysical Observatory. The first micro-calorimeter spectra of Ar XVII/XVIII from the Shanghai EBIT have recently been obtained. In our case, amplitude drift correction had to be made in order to get decent spectral resolution. The resolution at 3keV is about 20eV. The reason why the resolution is not as good as during offline tests (13eV) is thought to be due vibrations from the Shanghai EBIT, to which it is directly connected via a stainless steel tube.

The status of the permanent magnetic electron beam ion trap for low energy electron collision spectroscopy in Shanghai

A permanent magnet electron beam ion trap designed for studying low energy electron-ion collision spectroscopy has been designed and constructed at the Shanghai EBIT laboratory and is described in this report.

Electron beam density study using a portable slit imaging system at the Shanghai Electron Beam Ion Trap

In this work, a portable slit imaging system is developed to study both the electron beam diameter and the profile of the newly developed Shanghai Electron Beam Ion Trap (Shanghai EBIT). Images are detected by a charge coupled device (CCD) sensitive to both X rays and longer wavelength photons (up to visible). Large scale ray tracings were conducted for correcting the image broadening effects caused by the finite slit width and the finite width of the CCD pixels. A numerical de-convolution method was developed to analyse and reconstruct the electron beam density distribution in the EBIT. As an example of the measured beam diameter and current density, the FWHM (full width at half maximum) diameter of the electron beam at 81 keV and 120 mA is found to be 76.2 μm and the density 2.00 × 103 A·cm−2, under a magnetic field of 3 T, including all corrections.

The status of the micro-calorimeter at the Shanghai EBIT

This paper contains a brief introduction to the main parameters of a micro-calorimeter designed to operate at the Shanghai electron beam ion trap. This is followed by short descriptions of some aspects of the calorimeter.

Development of a low energy e− gun for studies of e−–molecule interactions using a recoil-ion and electron momentum spectrometer

To study the interaction between low-energy electrons and molecules, a recoil-ion and electron momentum spectrometer (RIMS) has been developed at Shanghai EBIT laboratory. As the low-energy electron source, the ELG-2 electron gun (Kimball Physics) coupled with an ultrafast pulse generator has been tested. The energy of the electron beam ranges from a few eV to 2 keV, and the pulse width of the beam is about 1 ns.

A collision platform at Shanghai EBIT

A collision research platform for studying the interaction of HCIs with atoms and molecules is close to its completion at Shanghai EBIT.

Progress of the spectroscopy research platform at the Shanghai electron beam ion trap

In this report we will focus on spectrometer development, spectroscopic studies and a few other recent developments at the Shanghai Electron Beam Ion Trap, EBIT laboratory. Currently the Shanghai EBIT has three spectrometers covering totally the wavelength region of 1 to 10000 Å. Two of these instruments are home made. A flat crystal spectrometer covers the wavelength range of around 1 - 20 Å while a flat field instrument covers the range of around 20 - 400 Å. The 3rd instrument is a commercial McPherson 225 normal incidence spectrometer. All spectrometers employ CCD cameras for photon detection. The Shanghai EBIT is also equipped with high purity Germanium detectors for, amongst other things, dielectronic recombination studies and time evolution studies of ion distributions. To back up these experimental studies computer codes have been developed for calculation of charge state balances etc. Parallel to the experimental program we have also developed experience at running a number of atomic structure codes (MCHF, MCDF, FAC) for various systems, e.g. the M3 decay of the 3d94s 3D3 for Ni-like ions.

High resolution flat crystal spectrometer for the Shanghai EBIT

We report on a high resolution flat crystal spectrometer designed for the Shanghai EBIT. Its energy range is from 0.5 to 10 keV. Three crystals can be installed in the vacuum chamber simultaneously, and its effective Bragg angle can be covered from 15 degrees to 75 degrees . A vacuum version charge-coupled device detector is used for detection of photons. An energy resolution under 1 eV was reached in measurements of the 4.5 keV Kalpha(1) line by using an x-ray generator with a titanium anode. The spectrometer was also tested to operate well on the Shanghai EBIT by observing the lines of tungsten at around 3.2 keV.

Progress and research at the Shanghai EBIT

In this report, a brief description of the current progress at the Shanghai EBIT project is presented. This is followed by a short discussion of the measurement of various parameters (electron beam diameter and ion density) under a number of operational conditions. A brief introduction to di-electronic recombination measurements for highly ionized xenon is given. Next, we present a preliminary measurement of the time dependence of xenon X-ray emission lines. Finally, a comparison of calculated and experimental charge-state distributions is given. This shows the influence of multi-electron capture and different distributions of the ion cloud on the charge state distribution.PACS Nos.: 41.85.–p; 34.80.Kw; 34.80Lx

Progress at the Shanghai EBIT

In this report, a brief description of the progress of the Shanghai EBIT project is presented. This is followed by short discussions on the X ray spectra at several electron beam energies and the ion densities in the EBIT at a specific running condition.

Status of the Shanghai EBIT

In this report, a brief description concerning the status of Shanghai EBIT project is presented. This is followed by short discussions on the different characteristics of the two electron gun designs and the superconducting Helmholtz coils for the Shanghai EBIT.

Physics Based on Electron Beam Ion Traps*

A brief description of the operational principles of an Electron Beam Ion Trap is given with specific reference to the currently under development/construction Shanghai EBIT. This is followed by an introduction to some of the frontier physics problems of highly charged ions that can be studied with such devices. Also a discussion of the use of EBITs as a powerful tool in hot-plasma diagnostics is presented.