Abélia Ellingsen

• Sjobak, Kyrre Ness; Rød-Lindberg, E; Ellingsen, Abélia; Drobniak, Pierre; Rieker, Vilde Flognfeldt & Reaz, F [Show all 8 contributors for this article] (2026). SHARP: A compact focusing system for medical applications using a diverging plasma lens. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 3266(1), p. 012014–012014. doi: 10.1088/1742-6596/3266/1/012014. Full text in Research Archive Show summary

  Abstract Cancer therapy for deep-seated tumors requires precise irradiation of a small target deep within the patient while minimizing radiation exposure to surrounding tissues. This can be accomplished with a round beam sharply converging towards a single spot, requiring a large beam size in both planes at the exit of the focusing system. Achieving this over a short distance using only quadrupole lenses is challenging; but by using a linear active plasma lens (APL) in defocusing mode, the beam can be quickly and non-destructively enlarged before focusing using quadrupoles. The position of the irradiation spot can also be scanned in three dimensions by changing magnet settings. The SHARP project will develop and test this concept. Such a system can be used with very high energy electrons (hundreds of MeV), creating a Bragg-peak-like spot using novel accelerator technology. This could lead to more compact radiotherapy facilities, not requiring a bulky infrastructure typically associated with proton radiotherapy machines. If successful, SHARP will enable precision conformal radiotherapy, spatial fractionation, and potentially be useful for FLASH radiotherapy.

• Getz, Michael Norderhaug; Ellingsen, Abélia; Dahl-Hansen, Runar Plunnecke; Escobedo-Cousin, Enrique & Vereshchagina, Elizaveta (2026). Dielectric breakdown and reliability of thin film insulators for high-voltage microelectromechanical systems applications. Thin Solid Films. ISSN 0040-6090. 836. doi: 10.1016/j.tsf.2026.140876. Full text in Research Archive Show summary

  The growing demand for miniaturized and digitally integrated systems has accelerated the adoption of microelectromechanical systems (MEMS) across high-voltage applications, including electroseparation, microplasmas, and electrospraying. As these applications often operate in the kV range, dielectric reliability becomes a critical design consideration. This study presents a controlled, side-by-side comparison of breakdown behaviour, leakage current, and process compatibility of thermal SiO2, plasma-enhanced chemical vapour deposition SiO2, Low-pressure chemical vapour deposition SiNx, and atomic layer deposition (ALD)-Al2O3 using capacitive test structures with comparable film thicknesses. Thermal SiO2 exhibited the highest dielectric strength, reaching high fields of up to 24 MV/cm for a 54 nm dry oxide, although its ≥1000 °C processing temperature limits post-metallization compatibility. Among low-temperature options, ALD-Al2O3 demonstrated the most promising performance, with the best-performing process variation achieving a median breakdown field of 14.8 MV/cm and a median leakage current of 11 nA/cm² at 8 MV/cm for a 61 nm film deposited at 220 °C and annealed at 450 °C. These values exceed those reported for comparable thicknesses, highlighting the sensitivity of dielectric performance to both deposition and annealing conditions. The findings provide practical guidance for selecting dielectric materials that ensure substrate insulation reliability in high-voltage MEMS applications, balancing electrical performance with fabrication constraints.

• Ellingsen, Abélia; Milenko, Karolina Barbara; Escobedo-Cousin, Enrique; Hoang, Chi Huong Do; Zonetti, Simone & Liberale, Alessandro [Show all 7 contributors for this article] (2025). Integration of MEMS-based plasma emission sources in a low volume flow cell. In Walczak, Rafał & Śniadek, Patrycja (Ed.), EUROSENSORS XXXVII: Proceedings of the 37th European Conference on Solid-State Transducers Eurosensors 2025, Wroclaw, Poland - Sept. 7th - 10th 2025. AMA Service GmbH. ISSN 9783910600072. p. 297–298. doi: 10.5162/eurosensors2025/mp47. Full text in Research Archive Show summary

  This paper discusses the integration and testing of micro-electro-mechanical systems (MEMS)-based microplasma devices with low-volume flow cells at the PCB level for emission spectroscopy of volatile organic compounds (VOCs). We introduced a novel bonding process that ensures a tight gas seal, stable pressure control down to 150 mbar, and the exchange of top fluidic glass substrates to assess their influence on the emission spectrum. The bonding process facilitates the assembly of pre-packaged MEMS components for reconfigurable and repeatable gas exposure experiments.

• Milenko, Karolina Barbara; Vereshchagina, Elizaveta & Ellingsen, Abélia (2025). Flexible surface-enhanced Raman spectroscopy sensor for wearable devices. In Walczak, Rafał & Śniadek, Patrycja (Ed.), EUROSENSORS XXXVII: Proceedings of the 37th European Conference on Solid-State Transducers Eurosensors 2025, Wroclaw, Poland - Sept. 7th - 10th 2025. AMA Service GmbH. ISSN 9783910600072. p. 158–159. doi: 10.5162/eurosensors2025/t6.3.1. Full text in Research Archive Show summary

  We report the fabrication and characterization of a flexible, nanostructured surface-enhanced Raman spectroscopy sensor designed for integration in wearable optical devices. This sensor utilizes the bio-compatible material FlexDym®, which offers excellent flexibility and advantages in manufacturing. The nanostructures are embossed through a temperature and pressure-assisted molding process using a silicon master. The fabricated SERS structures exhibit significant enhancement in Raman signal detec-tion. This work advances state-of-the-art in flexible SERS and wearables.

• Vereshchagina, Elizaveta; Escobedo-Cousin, Enrique; Milenko, Karolina Barbara; Zonetti, Simone; Ellingsen, Abélia & Hoang, Chi Huong Do [Show all 9 contributors for this article] (2025). MEMS-based microplasma sources for gas analysis. In Walczak, Rafał & Śniadek, Patrycja (Ed.), EUROSENSORS XXXVII: Proceedings of the 37th European Conference on Solid-State Transducers Eurosensors 2025, Wroclaw, Poland - Sept. 7th - 10th 2025. AMA Service GmbH. ISSN 9783910600072. p. 106–107. doi: 10.5162/eurosensors2025/t4.1.2. Full text in Research Archive Show summary

  This paper presents the development of miniaturized microplasma sources for gas analysis based on micro-electromechanical systems (MEMS) technology. We discuss critical device design aspects, from FEM modeling and device concept to fabrication and experimental validation. A functional demonstrator was fabricated, and successful plasma ignition was achieved under controlled conditions. The results suggest that the developed microplasma sources hold strong potential as compact, integrable compo-nents for gas analysis systems in various industrial applications.

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• Ellingsen, Abélia; Adli, Erik; Drobniak, Pierre; Lindstrøm, Carl A.; Rød-Lindbergh, Elisabeth & Rieker, Vilde Flognfeldt [Show all 14 contributors for this article] (2026). SHARP: A Compact Focusing System for Emerging Particle Therapies using an Active Plasma Lens. doi: https:/indico.desy.de/event/51069/contributions/205605/. Full text in Research Archive Show summary

  Background: Improved control of the beam envelope in particle radiotherapy could enhance the precision of dose delivery. A novel approach is to incorporate an active plasma lens (APL) into the beamline. This compact device is used for strong and radially symmetric defocusing, giving rapid and controlled beam expansion. Such an expanded beam is of interest in itself, as it is generated by beam optics rather than through scattering, enabling large high intensity fields that may be relevant for FLASH applications. Beam expansion can also be followed by downstream refocusing to produce a sharp waist at the target. This may reduce entrance dose to healthy tissue while enhancing dose deposition at depth. Such beam geometries from a compact system could benefit precision conformal radiotherapy and spatial fractionation. The SHARP project is in the process of demonstrating these ideas experimentally with 200 MeV very high-energy electrons (VHEE), supported by simulations of beam optics and dose distributions. Materials and Methods: Experiments are being conducted at the CLEAR facility at CERN. The system combines a defocusing APL with quadrupole magnets for final focusing onto the target. Beam enlargement, without focusing, is evaluated on a downstream profile monitoring screen. The refocused beam is subsequently characterized with screens downstream of the quadrupoles. Radiation transport simulations in Geant4 are used to model dose deposition at the target and outside the focal region. Simulations with ImpactX are used for designing beam optics and assessing the influence of e.g. energy spread. Results: Beam enlargement from the APL is experimentally observed to be linear and symmetric in both transverse planes. Simulations show that quadrupoles can modify these beams into large, quasi-parallel fields for broad irradiation of higher intensity than passive scattering, which could be useful to investigate further for certain FLASH applications. For small deep targets, simulations show that increasing the APL current coupled with refocusing quadrupoles reduces focal beam size while increasing divergence, producing a sharp Bragg-like peak. Larger opening angles upstream and downstream of the target have also been confirmed experimentally. Conclusions: SHARP investigates a compact hybrid APL-quadrupole system to achieve precise focal spots and controlled dose distributions. The technique could serve as a versatile research platform for SFRT and FLASH applications. The project’s first experimental results represent a promising step towards improved dose delivery by demonstrating both controlled beam enlargement and refocusing. Ongoing work to refine the concept includes simulations and experiments of scattering in water phantoms, nonlinear APL defocusing for generating enlarged flat fields, spot scanning, and extension of the concept to protons.

• Ellingsen, Abélia (2025). The Oslo Plasma Lens Experiment. doi: https:/indico.cern.ch/event/1618125/#44-plasma-lens-developments-at. Full text in Research Archive

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