1
|
Beiersdorfer P, Lepson JK, Brown GV, Hell N, Träbert E, Hahn M, Savin DW. High-Resolution Laboratory Measurements and Identification of Fe IX Lines near 171 Å. Atoms 2022; 10:148. [DOI: 10.3390/atoms10040148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
A multitude of weaker Fe IX lines have been predicted in the vicinity of the strong 171 Å line that dominates the spectra of many astrophysical and laboratory sources. Some of these weaker lines have only recently been identified in the laboratory, albeit some only tentatively. Here, we present measurements on the Livermore EBIT-I electron beam ion trap that span the region from 170.0 to 173.6 Å, which surrounds the 171 Å line. The measurements stepped through electron beam energy to determine the charge state of iron associated with each observed feature. Moreover, we have minimized the presence of oxygen in the trap, because oxygen lines obscured possible Fe IX lines in past measurements and prevented their identification. Our measurement confirms formerly tentative identifications and adds several new assignments.
Collapse
|
2
|
Träbert E, Beiersdorfer P, Brown GV, Hell N, Lepson JK, Fairchild AJ, Hahn M, Savin DW. Laboratory Search for Fe IX Solar Diagnostic Lines Using an Electron Beam Ion Trap. Atoms 2022; 10:115. [DOI: 10.3390/atoms10040115] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Fe IX spectrum features two lines in the extreme ultraviolet whose ratio has been rated among the best density diagnostics in the solar spectrum. One line is an E1-allowed intercombination transition at 244.909 Å, the other an E1-forbidden M2 transition at 241.739 Å. Employing a medium and a high resolution spectrometer at the Livermore EBIT-I electron beam ion trap, we have observed the line pair in the laboratory for the first time. Using a CHIANTI model computation, the observed line ratio yields a value of the electron density that is compatible with typical densities in our device.
Collapse
|
3
|
Träbert E. Atomic Lifetime Data and Databases. Atoms 2022; 10:46. [DOI: 10.3390/atoms10020046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Atomic-level lifetimes span a wide range, from attoseconds to years, relating to transition energy, multipole order, atomic core charge, relativistic effects, perturbation of atomic symmetries by external fields, and so on. Some parameters permit the application of simple scaling rules, others are sensitive to the environment. Which results deserve to be tabulated or stored in atomic databases? Which results require high accuracy to give insight into details of the atomic structure? Which data may be useful for the interpretation of plasma experiments or astrophysical observations without any particularly demanding accuracy threshold? Should computation on demand replace pre-fabricated atomic databases?
Collapse
|
4
|
Hahn M, Arthanayaka T, Beiersdorfer P, Brown GV, Savin DW. Ion energy distribution in an electron beam ion trap inferred from simulations of the trapped ion cloud. Phys Rev E 2022; 105:015204. [PMID: 35193188 DOI: 10.1103/physreve.105.015204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Accepted: 12/13/2021] [Indexed: 11/07/2022]
Abstract
We have inferred the energy distribution of trapped ions in an electron beam ion trap (EBIT) from simulations of the spatial distribution of Fe^{13+} ions and a comparison with measured visible light images of the ion cloud. We simulated the cloud of Fe^{13+} ions by computing ion trajectories in the EBIT for different ion energy distributions used to initialize the trajectories. We then performed a least-squares fit to infer the ion energy distribution that best reproduced the measured ion cloud. These best-fit distributions were typically non-Maxwellian. For electron beam energies of 395-475 eV and electron beam currents of 1-9 mA, we find that the average ion energy is in the range of 10-300 eV. We also find that the average ion energy increases with increasing beam current approximately as 〈E〉≈25I_{e}eV, where I_{e} is the electron beam current in mA. We have also compared our results to Maxwell-Boltzmann-distribution ion clouds. We find that our best-fit non-thermal distributions have an 〈E〉 that is less than half that of the T from the best-fit Maxwell-Boltzmann distributions (〈E〉/q)/T=0.41±0.05.
Collapse
Affiliation(s)
- Michael Hahn
- Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, New York 10027, USA
| | | | - Peter Beiersdorfer
- Space Sciences Laboratory, University of California, Berkeley, California 94720, USA
| | - Gregory V Brown
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Daniel W Savin
- Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, New York 10027, USA
| |
Collapse
|
5
|
Arthanayaka TP, Beiersdorfer P, Brown GV, Hahn M, Hell N, Lockard TE, Savin DW. Measurements of the effective electron density in an electron beam ion trap using extreme ultraviolet spectra and optical imaging. Rev Sci Instrum 2018; 89:10E119. [PMID: 30399824 DOI: 10.1063/1.5036758] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 08/08/2018] [Indexed: 06/08/2023]
Abstract
In an electron beam ion trap (EBIT), the ions are not confined to the electron beam, but rather oscillate in and out of the beam. As a result, the ions do not continuously experience the full density of the electron beam. To determine the effective electron density, n e,eff, experienced by the ions, the electron beam size, the nominal electron density n e, and the ion distribution around the beam, i.e., the so-called ion cloud, must be measured. We use imaging techniques in the extreme ultraviolet (EUV) and optical to determine these. The electron beam width is measured using 3d → 3p emission from Fe xii and xiii between 185 and 205 Å. These transitions are fast and the EUV emission occurs only within the electron beam. The measured spatial emission profile and variable electron current yield a nominal electron density range of n e ∼ 1011-1013 cm-3. We determine the size of the ion cloud using optical emission from metastable levels of ions with radiative lifetimes longer than the ion orbital periods. The resulting emission maps out the spatial distribution of the ion cloud. We find a typical electron beam radius of ∼60 μm and an ion cloud radius of ∼300 μm. These yield a spatially averaged effective electron density, n e,eff, experienced by the ions in EBIT spanning ∼ 5 × 109-5 × 1011 cm-3.
Collapse
Affiliation(s)
- T P Arthanayaka
- Columbia Astrophysics Laboratory, New York, New York 10027, USA
| | - P Beiersdorfer
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - G V Brown
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - M Hahn
- Columbia Astrophysics Laboratory, New York, New York 10027, USA
| | - N Hell
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - T E Lockard
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - D W Savin
- Columbia Astrophysics Laboratory, New York, New York 10027, USA
| |
Collapse
|
6
|
Beiersdorfer P, Magee EW, Hell N, Brown GV. Imaging crystal spectrometer for high-resolution x-ray measurements on electron beam ion traps and tokamaks. Rev Sci Instrum 2016; 87:11E339. [PMID: 27910570 DOI: 10.1063/1.4962049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We describe a crystal spectrometer implemented on the Livermore electron beam ion traps that employ two spherically bent quartz crystals and a cryogenically cooled back-illuminated charge-coupled device detector to measure x rays with a nominal resolving power of λ/Δλ ≥ 10 000. Its focusing properties allow us to record x rays either with the plane of dispersion perpendicular or parallel to the electron beam and, thus, to preferentially select one of the two linear x-ray polarization components. Moreover, by choice of dispersion plane and focussing conditions, we use the instrument either to image the distribution of the ions within the 2 cm long trap region, or to concentrate x rays of a given energy to a point on the detector, which optimizes the signal-to-noise ratio. We demonstrate the operation and utility of the new instrument by presenting spectra of Mo34+, which prepares the instrument for use as a core impurity diagnostic on the NSTX-U spherical torus and other magnetic fusion devices that employ molybdenum as plasma facing components.
Collapse
Affiliation(s)
- P Beiersdorfer
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - E W Magee
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - N Hell
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - G V Brown
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| |
Collapse
|
7
|
Clementson J, Lennartsson T, Beiersdorfer P. Extreme Ultraviolet Spectra of Few-Times Ionized Tungsten for Divertor Plasma Diagnostics. Atoms 2015; 3:407-21. [DOI: 10.3390/atoms3030407] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
|
8
|
|
9
|
Widmann K, Beiersdorfer P, Magee EW, Boyle DP, Kaita R, Majeski R. High-resolution grazing-incidence grating spectrometer for temperature measurements of low-Z ions emitting in the 100-300 Å spectral band. Rev Sci Instrum 2014; 85:11D630. [PMID: 25430206 DOI: 10.1063/1.4894388] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We have constructed a high-resolution grazing-incidence spectrometer designed for measuring the ion temperature of low-Z elements, such as Li(+) or Li(2 +), which radiate near 199 Å and 135 Å, respectively. Based on measurements at the Livermore Electron Beam Ion Trap we have shown that the instrumental resolution is better than 48 mÅ at the 200 Å setting and better than 40 mÅ for the 135-Å range. Such a high spectral resolution corresponds to an instrumental limit for line-width based temperature measurements of about 45 eV for the 199 Å Li(+) and 65 eV for the 135 Å Li(2 +) lines. Recently obtained survey spectra from the Lithium Tokamak Experiment at the Princeton Plasma Physics Laboratory show the presence of these lithium emission lines and the expected core ion temperature of approximately 70 eV is sufficiently high to demonstrate the feasibility of utilizing our high-resolution spectrometer as an ion-temperature diagnostic.
Collapse
Affiliation(s)
- K Widmann
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - P Beiersdorfer
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - E W Magee
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - D P Boyle
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - R Kaita
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - R Majeski
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| |
Collapse
|