A 20 kW class Hall Thruster, featuring two coaxial channels and a centrally mounted cathode, has been designed at the University of Pisa and manufactured by Aerospazio Tecnologie s.r.l. The thruster was preliminarily characterized in 2024 within the framework of the ESA TANDEM programme. The following paper outlines the findings from the recent characterization test campaign performed on the TANDEM thruster coupled with the new cathode developed within the CHEOPS-VHP-BB programme. This test was carried out at AEROSPAZIO Tecnologie in 2025 in the LVTF-3 test facility. The TANDEM thruster was operated with three different propellants (Xenon, Krypton, and Argon) at four operating points (from 4.5 to 20 kW) with discharge voltages of 300 and 400 V. An extended diagnostics activity was carried out including thrust measurements, plume diagnostics and temperature measurements. Thermal assessments were also performed using an infrared thermal camera. This document presents the experimental results collected throughout the testing. The experimental campaign showcased various operating regimes with transitions between them, and how they can affect TANDEM’s performance. The thruster was able to reach total specific impulses of over 2200 s during operation with Xenon and above 2300 s using Krypton. Efficiencies were between 50 and 55

For the future of space exploration and space logistics, and to reduce costs for orbit transportation of future payloads, very-high-power electric propulsion (EP) thrusters are needed. Before flying into space, on earth qualification is essential. Due to the high beam power and high beam current, plume diagnostics, such as, current density and ion energy distribution function measurements, faces challenges. In this work, the design and test of plume diagnostic tools, namely a Faraday boom for full current density mapping and a retarding potential analyzer for ion energy distribution function measurements, for very-high-power EP thrusters is described. The test object is a very-high-power, nested-channel Hall effect thruster ``TANDEM'' with a centrally mounted cathode. Thruster was operated in single-channel and dual-channel mode with a maximum discharge power of 20 kW, and propellants Xe and Kr. The diagnostic tools provided essential and valuable performance data. Still, data showed so-far unknown phenomena. Selected experimental data are presented and discussed. Optional improvements of the diagnostic tools are presented and discussed.

We describe the application of laser-induced fluorescence (LIF) spectroscopy in the context of neutral gas characterization in RIT-type gridded ion engines. The experiments were carried out using a xenon-driven gridded radiofrequency ion source. Two LIF transition schemes (laser excitation at 820.6 nm and 823.2 nm, wavelengths in air) targeting metastable states were used to probe the xenon neutral gas species inside the ion source discharge chamber as well as in the near-field plume region. By adjustment of the ion source operating conditions, a variation of the peak-signal Doppler shift was induced in LIF spectra recorded in the plume region with axial-laser injection. This feature is attributed to the speed of the neutrals effusing through the ion extraction optics which eventually allows for estimation of the neutral gas temperature without direct optical access to the discharge chamber.

The change in ion energy distribution and composition of a reactive ion beam produced by an RF-excited ion beam source and operation with a mixture of CHF3 and O(2 )was investigated and correlated with the etching behavior. To this end, measurements were performed with an energy-selective mass spectrometer to determine ion energy distributions, current density measurements for the measurement of current density distributions of the ion beam, and tactile measurements to determine the etching rates of Si and photoresist. The morphology of the photoresist was measured with a scanning force microscope. In particular, alterations in the etching yield and surface morphology of the photoresist can be observed in response to changes in the applied RF-power. An increase in plasma density leads to an increase in fragmentation processes of the injected reactive gases, resulting in the formation of smaller fragments. These smaller fragments have a chemical impact on the substrate surface, which affects the etching performance. These effects can have significant consequences in the context of long-time reactive ion beam processing for patterning applications.

Semiconductor spin qubits combine excellent quantum performance with the prospect of manufacturing quantum devices using industry-standard metal-oxide-semiconductor (MOS) processes. This applies also to ion-implanted donor spins, which further afford exceptional coherence times and large Hilbert space dimension in their nuclear spin. Here multiple strategies are demonstrated and integrated to manufacture scale-up donor-based quantum computers. 31PF2 molecule implants are used to triple the placement certainty compared to 31P ions, while attaining 99.99% confidence in detecting the implant. Similar confidence is retained by implanting heavier atoms such as 123Sb and 209Bi, which represent high-dimensional qudits for quantum information processing, while Sb2 molecules enable deterministic formation of closely-spaced qudits. The deterministic formation of regular arrays of donor atoms with 300 nm spacing is demonstrated, using step-and-repeat implantation through a nano aperture. These methods cover the full gamut of technological requirements for the construction of donor-based quantum computers in silicon.

The composition and ion energy distributions of the main ion species of an ion beam were recorded and analyzed. The RF-type broad beam ion source was operated with a mixture of CHF3 and O2. A plasma bridge neutralizer operating with Ar was employed for ion beam neutralization. The data were collected with an energy-selective mass spectrometer (ESMS). The mass spectrum showed numerous ion species, beginning with ionized molecules, dissociation products of the process gases and products from reactions with background gas and the plasma discharge vessel, and the extraction system. For a quantification of the ion beam composition, the mass dependent transmission functions for two ESMS were determined. The ion energy distributions show that, in comparison to operation with inert gases, there are additional slower ions present. These ions can be related to dissociation processes outside of the ion beam source. As a result of their typically lower etching yield, these slower ions affect the etching behavior.

Application of single-photon absorption laser-induced fluorescence (LIF) spectroscopy for non-intrusive measurement of neutral xenon and singly charged xenon ion kinetic temperatures in the discharge chamber of a gridded radiofrequency ion source is demonstrated. A LIF spectrum analysis approach including hyperfine structure reconstruction and inverse filtering (Fourier deconvolution) is outlined. Special focus is set on optimization of post-deconvolution filtering as well as retracing of deconvolution result imperfection due to hyperfine structure parameter uncertainty, incorrect natural linewidth, and saturation of the LIF signal. The corresponding contributions to the kinetic temperature estimation error are quantified via simulation of spectral lineshapes. Deconvolution of almost unsaturated LIF spectra recorded in the center of the ion source discharge chamber reveals that the neutral xenon and xenon ion kinetic temperatures range between approximately 500 and 700 K and, respectively, 700 and 1000 K depending on the radiofrequency power supplied to the discharge.

Semiconductor spin qubits combine excellent quantum performance with the prospect of manufacturing quantum devices using industry-standard metal-oxide-semiconductor (MOS) processes. This applies also to ion-implanted donor spins, which further afford exceptional coherence times and large Hilbert space dimension in their nuclear spin. Here we demonstrate and integrate multiple strategies to manufacture scale-up donor-based quantum computers. We use $^{31}$PF$_{2}$ molecule implants to triple the placement certainty compared to $^{31}$P ions, while attaining 99.99$\,$% confidence in detecting the implant. Similar confidence is retained by implanting heavier atoms such as $^{123}$Sb and $^{209}$Bi, which represent high-dimensional qudits for quantum information processing, while Sb$_2$ molecules enable deterministic formation of closely-spaced qudits. We demonstrate the deterministic formation of regular arrays of donor atoms with 300$\,$nm spacing, using step-and-repeat implantation through a nano aperture. These methods cover the full gamut of technological requirements for the construction of donor-based quantum computers in silicon.

Colour centre ensembles in diamond have been the subject of intensive investigation for many applications including single photon sources for quantum communication, quantum computation with optical inputs and outputs, and magnetic field sensing down to the nanoscale. Some of these applications are realised with a single centre or randomly distributed ensembles in chips, but the most demanding application for a large-scale quantum computer will require ordered arrays. By configuring an electronic-grade diamond substrate with a biased surface graphene electrode connected to charge-sensitive electronics, it is possible to demonstrate deterministic single ion implantation for ions stopping between 30 and 130 nm deep from a typical stochastic ion source. An implantation event is signalled by a charge pulse induced by the drift of electron-hole pairs from the ion implantation. The ion implantation site is localised with an AFM nanostencil or a focused ion beam. This allows the construction of ordered arrays of single atoms with associated colour centres that paves the way for the fabrication of deterministic colour center networks in a monolithic device.

The response of a dedicated image charge detector to a single passage of small ion bunches was studied. This detector was designed and built in our labs aiming for a maximized signal-to-noise ratio (SNR) with the motivation to enable single ion detection for deterministic ion implantation, a key technique for solid state based quantum technologies, in the future. It is shown how segmentation of the detector with the appropriate combination of the individual segment signal channels significantly increases the SNR. Additionally, the detector is cryogenically cooled to temperatures down to 163 K, further enhancing the SNR. The detection sensitivity of this detector prototype was measured to be 80 elementary charges for SNR=2, detecting 4 keV Xe+ ion bunches. At this SNR, the false-positive error rate is expected to be 0.1%. Comparing the measured sensitivity with a theoretical estimation yielding 22 elementary charges for SNR=2, the presented results lead the way to further optimizations of the detector components and the signal analysis techniques, necessary to realize single ion detection.

The demonstration of universal quantum logic operations near the fault-tolerance threshold has established ion-implanted near-surface donor atoms as a plausible platform for scalable quantum computing in silicon. The next technological step forward requires a deterministic fabrication method to create large-scale arrays of donors, featuring a few-hundred-nanometer interdonor spacing. Here, we explore the feasibility of this approach by implanting low-energy ions into silicon devices featuring a 60 x 60 mu m2 sensitive area and an ultrathin 3.2-nm gate oxide-capable of hosting large-scale donor arrays. We employ a characterization system consisting of a modified focused-ion-beam machine and ultralow-noise ion-detection electronics to demonstrate a method for evaluating the device response characteristics to shallowly implanted 12-keV 1H+2 ions. Despite the weak internal electric field, near-unity chargecollection efficiency is obtained from the entire sensitive area. This can be explained by the critical role that the thermal gate oxide plays in the ion-detection response, allowing an initial rapid diffusion of ion-induced charge away from the implant site. Next, we adapt our approach to perform deterministic implantation of a few thousand 24-keV 40Ar2+ ions into a predefined microvolume, without any additional collimation. Despite the reduced ionization from the heavier ion species, a fluence-independent detection confidence of >= 99.99% is obtained. Our system thus represents not only a method for mapping the near-surface electrical landscape of electronic devices but also a framework toward mask-free prototyping of large-scale donor arrays in silicon.

Near-Surface Doping In article number 2103235, David N. Jamieson and co-workers report that single-crystal silicon can be configured with arrays of single, near-surface, dopant atoms using on-chip electrodes and low-noise charge-sensitive electronics to register single-ion implants. Suitable for integration with a nanostencil scanner to localize the implants, the system makes use of the signal of electron–hole pairs generated as the ions dissipate their kinetic energy in the crystal. The system can be part of an engineering strategy for high-confidence fabrication of large-scale donor arrays to exploit donor spin ensembles in silicon devices.

IonJet is an engineering model of a low-cost electric propulsion system for small satellites. Whereas the flow control subsystem is based on the MICROJET 2000 system launched 2016 on the BIROS satellite, the thruster subsystem is based on a novel gridded ion thruster where the neutralizer is integrated in the ion thruster allowing for simultaneous ion and electron extraction. This design allows reducing the number of components and consequently costs and system complexity. The whole system was successfully tested under vacuum conditions regarding ignition and stable operation of the propulsion system. In the performance tests, thrusts of 1 mN could be achieved using Xe gas as propellant at a total power consumption of less than 50 W as well as specific impulses larger than 1000 s, including the gas consumption of the neutralizer. In addition, first tests with Kr gas were performed showing that for the same total power the achievable thrust is reduced to 55% – 68% of that for Xe.

The lifetime of electric propulsion (EP) thrusters depends particularly on the erosion characteristics of operation relevant components, for instance, the grid hole erosion of gridded ion thrusters or the channel wall erosion of Hall effect thrusters. Here two tools for in situ erosion measurements are presented, a triangular laser head for surface profiling and a telemicroscope for high-resolution optical imaging. Both can give access to radial and axial erosion parameters. The measurements can be done in situ without the need for breaking the vacuum and dismounting the thruster, which reduces thruster testing time considerably. In situ measurements can also help to ensure reproducibility of thruster performance conditions and can improve statistics of thruster characterization. The present work describes the fundamentals of both techniques in detail, selected experimental setups are presented, their performance is characterized and critically evaluated. The capabilities and limitations related to erosion measurements of EP thrusters are, exemplary, demonstrated for a gridded ion thruster RIT-22 and a Hall effect thruster SPT-100D.

Gallium oxide thin films were grown by ion beam sputter deposition (IBSD) at room temperature on Si substrates with systematically varied process parameters: primary ion energy, primary ion species (O2+ and Ar+), sputtering geometry (ion incidence angle α and polar emission angle β), and O2 background pressure. No substrate heating was applied because the goal of these experiments was to investigate the impact of the energetic film-forming species on thin film properties. The films were characterized with regard to film thickness, growth rate, crystallinity, surface roughness, mass density, elemental composition and its depth profiles, and optical properties. All films were found to be amorphous with a surface roughness of less than 1 nm. The stoichiometry of the films improved with an increase in the energy of film-forming species. The mass density and the optical properties, including the index of refraction, are correlated and show a dependency on the kinetic energy of the film-forming species. The ranges of IBSD parameters, which are most promising for further improvement of the film quality, are discussed.

Methods based on laser-induced fluorescence spectroscopy are widely used for spatially resolved non-intrusive diagnostics of atomic or molecular densities and velocity distributions in plasma applications. With regard to electric space propulsion, one focus is on the investigation of rare gases such as xenon or krypton, which are currently the favored propellants in gridded ion- and Hall-effect thrusters. For gridded ion engines, diagnostics of neutral atoms is of interest since charge-exchange processes between neutrals and ions are the main driver of accelerator grid erosion, which limits the lifetime of a gridded ion thruster. Extending the capabilities of the advanced electric propulsion diagnostics platform which has been developed by the IOM and partners, single- and two-photon absorption laser-induced fluorescence diagnostics have been set-up recently at our institute. Both experimental set-ups, and as a series of first applications, measurements of krypton neutrals in the plume of the radiofrequency ion thruster RIT-10 (ArianeGroup GmbH), and xenon neutrals within the discharge chamber of a gridded radiofrequency ion source developed at IOM, are presented.

Ion current density distributions, mass spectra, and ion energy distribution functions (IEDFs) for the use of Ar and mixtures of Ar/He and Ar/Ne in an RF broad beam ion source have been measured as a function of the extracted ion beam current and the applied RF-power. For the measurements, an array of Faraday probes and an energy-selective mass spectrometer have been used. Regardless of the gases or gas mixtures used, a broadening of the ion current density profile is measured at constant grid voltages with increasing RF-power. The IEDFs of all species are also dependent on the applied RF-power and show a bimodal shape with an increasing energy shift for a higher RF-power. The data show a significant contribution of charge exchange processes after the ions left the ion beam source. Besides ions of the process gas, additional species of ions originating from the erosion processes of the ion beam source, can be found in the mass spectrum. The measurements show that the operating conditions of the ion source have a significant influence on the beam properties and thus can also affect the results of ultraprecise ion beam-assisted processes.

Although ferromagnets are found in all kinds of technological applications, their natural occurrence is rather unusual because only few substances are known to be intrinsically ferromagnetic at room temperature. In the past twenty years, a plethora of new artificial ferromagnetic materials have been found by introducing defects into non-magnetic host materials. In contrast to the intrinsic ferromagnetic materials, they offer an outstanding degree of material engineering freedom, provided one finds a type of defect to functionalize every possible host material to add magnetism to its intrinsic properties. Still, one controversial question remains: Are these materials really technologically relevant ferromagnets? In this study, a universal scheme for the computational discovery of new artificial functional magnetic materials is proposed, which is guided by experimental constraints and based on first principles. The obtained predictions explain very well the experimental data found in the literature. The potential of the method is further demonstrated by the experimental realization of a truly 2D ferromagnetic phase at room temperature, created in nominally non-magnetic TiO2 films by ion irradiation, which follows a characteristic 2D magnetic percolation transition and exhibits a tunable magnetic anisotropy.

For the engineering of nitrogen-vacancy (NV) centers in diamond, vacancies have been introduced locally into a type Ib diamond (100–200 ppm nitrogen content) by implanting argon ions from a sub-500 nm focused beam. At an acceleration potential of 12 kV, different charge states (Ar n+, n={1,4,8,11}) result in kinetic energies of 12–132 keV. NV-centers were formed by a subsequent annealing step. A wide range of fluences from around one ion to several hundred ions was implanted per spot. It was found that, on average, between 0.04 (12 keV) and 0.79 (132 keV) NV-centers are created from the vacancies of a single implanted argon ion, depending on the ion energy, but not on the fluence. The different number of vacancies created at each energy alone cannot account for the difference in NV-center yield. However, the probability of a given vacancy to diffuse to the diamond surface during annealing, where it cannot contribute to NV-center formation, was simulated and can fully explain the NV-yield behavior. With this model, an upper bound of approximately 300 nm for the diffusion length of a single vacancy was found for an annealing temperature of 800 °C.