Ion energy distribution in an electron beam ion trap inferred from simulations of the trapped ion cloud

Journal Article · 10 January 2022 · Physical Review. E

DOI: https://doi.org/10.1103/physreve.105.015204 · OSTI ID:2204099

Hahn, Michael  ^[1]; Arthanayaka, Thusitha  ^[2]; Beiersdorfer, Peter  ^[3]; Brown, Gregory V.  ^[4]; Savin, Daniel W.  ^[1]

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1. Columbia Univ., New York, NY (United States)
2. Skidmore College, Saratoga Springs, NY (United States)
3. Univ. of California, Berkeley, CA (United States)
4. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

For this work, we have inferred the energy distribution of trapped ions in an electron beam ion trap (EBIT) from simulations of the spatial distribution of Fe¹³⁺ ions and a comparison with measured visible light images of the ion cloud. We simulated the cloud of Fe¹³⁺ 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 $$\langle$$E$$\rangle$$ ≈ 25 I_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 $$\langle$$E$$\rangle$$ that is less than half that of the T from the best-fit Maxwell-Boltzmann distributions ($$\langle$$E$$\rangle$$/q)/T=0.41 ± 0.05.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 2204099
• Report Number(s): LLNL--JRNL-816723; 1026465
• Journal Information: Physical Review. E, Journal Name: Physical Review. E Journal Issue: 1 Vol. 105; ISSN 2470-0045
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English