Speaker
Description
Optical emission spectroscopy for measuring electron temperature and density in a Penning ion-source test stand for the production of negative hydrogen ions
Authors
J. Doyle$^{1,2}$, G. Fubiani$^{3}$, C. Xiao$^{1}$, L. Couedel$^{1}$, M. Dehnel$^{1,2,3}$.
Affiliations
- University of Saskatchewan — Department of Physics and Engineering Physics
- Selkirk Ion-source Research Center (SIRC)
- LAPLACE, Université de Toulouse, CNRS, Toulouse, France
Abstract
A Penning ion-source test stand is being developed at the newly commissioned Selkirk Ion-source Research Centre (SIRC) in British Columbia, Canada. Two important species produced by this ion source are alpha particles and negative hydrogen ions, for use in medical cyclotrons [1,2] for radioimmunotherapy and positron emission tomography (PET). In a first experimental campaign, the Collisional-Radiative Model approach [3] will be used to map emission intensity ratios to population densities and temperatures of emitting excited states using optical emission spectroscopy (OES) in helium plasmas. A second experimental campaign will investigate H− ions, which are produced in our Penning experiments through two main mechanisms: dissociative attachment of thermal electrons to vibrationally excited hydrogen molecules, and, in a subset of experiments, surface interactions with cesium [4,5]. The efficiency of negative ion production is strongly limited by electron temperature; a 5 eV change can reduce the dissociative attachment rate by up to 10$^4$ [5]. Electron density and gas pressure are also critical control parameters, since H− ions are destroyed through collisions with positive ions, electrons, and hydrogen atoms. Plasma parameters are difficult to measure directly during standard Penning operation with a Langmuir probe. Instead, OES will be used as a non-invasive diagnostic tool to determine average plasma parameters (electron temperature and density) by comparing the relative intensities of specific spectral lines associated with rotational and vibrational transitions [6], combined with a machine-learning approach. The new test stand being developed at SIRC will include options for direct measurements, such as a Langmuir probe and Faraday cup, as well as a fibre-optic spectrometer to correlate spectral emissions with temperature, arc current, gas flow rate, and magnetic field. This poster will review the details of this theory and its consideration in the test-stand design, as well as the integration of the Langmuir probe and fibre spectrometer.
References
- Schmor, P. "Review of Cyclotrons for the Production of Radioactive Isotopes for Medical and Industrial Applications." Reviews of Accelerator Science and Technology 4, no. 1, 103–116 (2011).
- Dehnel, M. et al. "H-, D- & He++ Source Developments for Medical Isotope Production Cyclotrons." 2024 International Topical Meeting on Nuclear Applications of Accelerators, Jefferson Lab, Norfolk, Virginia, USA, March 17–21, 2024.
- Savard, N. "Development and Characterization of a Penning Ion Source Using Helium." PhD thesis, University of British Columbia, 2022.
- Potkins, D. et al. "Improvements to Siemens Eclipse PET Cyclotron Penning Ion Source." AIP Conference Proceedings 2052, 050016 (2018).
- Sereda, I., Hrechko, Y., Azarenkov, M. and Sereda, K. "Penning Source of Hydrogen Negative Ions Testing at Different Gases Injection and Optional Application of ZrV Cathodes." International Journal of Hydrogen Energy 109, 1321–1324 (2025).
- Yang, Z. et al. "Studies on Hydrogen Plasma in a Penning Ion Source by Optical Emission Spectroscopy." IEEE Transactions on Plasma Science 41, 2941–2945 (2013).
| Email address | jdoyle@selkirk.ca |
|---|---|
| Funding Agency | Mitacs, Canadian Foundation for Innovation, Kootenay Association for Science and Technology |
| Visitor's Visa | no |
| Classification | Plasma and negative ion diagnostics |