Proceedings

EPJ D Highlight - Astrophysical plasma study benefits from new soft X-ray transition energies benchmark

An artist’s impression of an X-ray binary, the kind of cosmic event that will benefit from a new benchmark in the study of astrophysical plasmas. Credit: Dana Berry/NASA Goddard Space Flight Center

The new benchmark for X-ray transition energies set for neon, carbon dioxide, and sulfur hexafluoride paves a pathway to high accuracy analysis of astrophysical plasmas.

The analysis of astrophysical plasmas is vital in the quest to learn about some of the Universe’s most powerful and mysterious objects and events such as stellar coronae and winds, cataclysmic variables, X-ray binaries containing neutron stars and black holes, supernova remnants, or outflows in active galactic nuclei. The success of such research will lead to future astrophysical X-ray observatories enabling scientists to access techniques that are currently not available to X-ray astronomy. A key requirement for the accurate interpretation of high-resolution X-ray spectra is accurate knowledge of transition energies.

A new paper published in EPJ D authored by J. Stierhof, of the Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics of Friedrich-Alexander-Universt Erlangen-Nürnberg, Bamberg, Germany, and coauthors utilizes a newly introduced experimental setup at the BESSY II synchrotron facility to provide precise calibration references in the soft X-ray regime of neon, carbon dioxide, and sulfur hexafluoride gases.

“In many research fields involving X-rays or any wavelength of light, insights are obtained by comparing measurements of emission or absorption line wavelengths with known values of transitions in various elements. A shift of the observed wavelength with respect to the known one can occur because of the velocity of the emitter or absorber,” says Stierhof. “Our work demonstrates a setup to measure transition energies of gases simultaneous with known transitions in highly charged ions having only two remaining electrons that are precisely known from theoretical calculations.”

Monochromatic X-rays from a synchrotron beamline pass through an electron beam ion trap (EBIT), where they interact with the low-density plasma produced and trapped inside the EBIT and then enter a gas photoionization cell containing the atoms or molecules under investigation. Fluorescence emission from the ions in the EBIT provides the basis for the absolute calibration of the monochromator energy scale in the experiment.

In the paper, the authors found results for the energy transition in the k-shell of carbon dioxide that agree well with previous findings. The results in the transitions demonstrated by sulfur hexafluoride showed that previous experiments have a shift of around 0.5 eV, more than twice their claimed uncertainty.

The team concludes that the statistical uncertainty in principle allows calibrations in the desired range of 1 to 10 meV, with systematic contributions currently limiting the uncertainty to around 40 to100 meV.

“Our proposed setup provides an absolute calibration for the X-ray beam, but we found that the total uncertainty is dominated by relative changes of the beam,” Stierhof concluded. “Providing an additional setup to measure these relative changes will bring us closer to the resolution limit of 10 meV.”

This was our first experience of publishing with EPJ Web of Conferences. We contacted the publisher in the middle of September, just one month prior to the Conference, but everything went through smoothly. We have had published MNPS Proceedings with different publishers in the past, and would like to tell that the EPJ Web of Conferences team was probably the best, very quick, helpful and interactive. Typically, we were getting responses from EPJ Web of Conferences team within less than an hour and have had help at every production stage.
We are very thankful to Solange Guenot, Web of Conferences Publishing Editor, and Isabelle Houlbert, Web of Conferences Production Editor, for their support. These ladies are top-level professionals, who made a great contribution to the success of this issue. We are fully satisfied with the publication of the Conference Proceedings and are looking forward to further cooperation. The publication was very fast, easy and of high quality. My colleagues and I strongly recommend EPJ Web of Conferences to anyone, who is interested in quick high-quality publication of conference proceedings.

On behalf of the Organizing and Program Committees and Editorial Team of MNPS-2019, Dr. Alexey B. Nadykto, Moscow State Technological University “STANKIN”, Moscow, Russia. EPJ Web of Conferences vol. 224 (2019)

ISSN: 2100-014X (Electronic Edition)

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