A5026684504- Diamond and Carbon-based Materials Research
- Vacuum and Plasma Arcs
- Semiconductor materials and devices
- Metal and Thin Film Mechanics
- Particle Detector Development and Performance
- Spacecraft Design and Technology
- Ion-surface interactions and analysis
- Particle Accelerators and Free-Electron Lasers
- Electrostatic Discharge in Electronics
- Superconducting Materials and Applications
- Electrohydrodynamics and Fluid Dynamics
- Carbon Nanotubes in Composites
- Force Microscopy Techniques and Applications
- Remote Sensing and LiDAR Applications
- Photovoltaic System Optimization Techniques
- Nanotechnology research and applications
- Anodic Oxide Films and Nanostructures
- Satellite Communication Systems
- Electromagnetic Effects on Materials
- Hygrothermal properties of building materials
- Smart Agriculture and AI
- Advancements in Semiconductor Devices and Circuit Design
- Wood Treatment and Properties
- Fusion materials and technologies
- Combustion and Detonation Processes
Helsinki Institute of Physics
2015-2023
University of Helsinki
2015-2023
University of Tartu
2014-2023
Helsinki Art Museum
2019
Tartu Observatory
2014
The Compact Linear Collider (CLIC) is a multi-TeV high-luminosity linear e+e- collider under development. For an optimal exploitation of its physics potential, CLIC foreseen to be built and operated in staged approach with three centre-of-mass energy stages ranging from few hundred GeV up 3 TeV. first stage will focus on precision Standard Model physics, particular Higgs top-quark measurements. Subsequent measurements rare processes, as well searches for new processes states, e.g. states...
The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^-$ collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of project, its current status, and future developments. It presents physics potential reports on design, technology, implementation aspects accelerator detector. foreseen to be built operated stages, centre-of-mass energies 380 GeV, 1.5 TeV 3 TeV, respectively. uses two-beam acceleration...
When an electron emitting tip is subjected to very high electric fields, plasma forms even under ultra vacuum conditions.This phenomenon, known as arc, causes catastrophic surface modifications and constitutes a major limiting factor not only for modern sources, but also many large-scale applications such particle accelerators, fusion reactors etc.Although arcs have been studied thoroughly, the physical mechanisms that lead from intense emission ignition are still unclear.In this article, we...
This paper presents the mission analysis, requirements, system design, level test results, as well mass and power budgets of a 1-unit CubeSat ESTCube-1 built to perform first in-orbit demonstration electric solar wind sail (E-sail) technology.The E-sail is propellantless propulsion concept that uses thin charged electrostatic tethers for turning momentum flux natural plasma stream, such wind, into spacecraft propulsion.ESTCube-1 will deploy charge 10 m long tether measure changes in...
The Copernicus Sentinel-2 mission operated by the European Space Agency (ESA) provides comprehensive and continuous multi-spectral observations of all Earth’s land surface since mid-2015. Clouds cloud shadows significantly decrease usability optical satellite data, especially in agricultural applications; therefore, an accurate reliable mask is mandatory for effective EO data exploitation. During last few years, image segmentation techniques have developed rapidly with exploitation neural...
We propose a method to directly couple molecular dynamics, the finite element method, and particle-in-cell techniques simulate metal surface response high electric fields. use this evolution of field-emitting tip under thermal runaway by fully including three-dimensional space-charge effects. also present comparison process between two geometries different widths. The results show with statistical significance that in case sufficiently narrow field emitters, occurs cycles where intensive...
Due to the miniaturization of microelectromechanical systems, nanoelectromechanical systems and molecular devices, problem vacuum insulation becomes more prominent. The nanoscale thermal effects caused by electron emission electric current Joule heat under high fields lead gasification migration material in device. In this work, a coupled dynamics–electrodynamics method is used simulate evaporation nanotips field. Moreover, Cu with different initial geometries macroscopic are modelled....
This work describes the final design and implementation of electrical power system for ESTCube-1, a 1-unit CubeSat tasked with testing electrostatic tether concept associated technologies electric solar wind sail in polar low Earth orbit.The mission required an efficient reliable to be designed that could efficiently handle highly variable requirements protect satellite from damage caused by malfunctions its individual subsystems, while using only commercial-off-the-shelf components.The was...
We propose a method for efficiently coupling the finite element with atomistic simulations, while using molecular dynamics or kinetic Monte Carlo techniques. Our can dynamically build an optimized unstructured mesh that follows geometry defined by data. On this mesh, different multiphysics problems be solved to obtain distributions of physical quantities interest, which fed back system. The simulation flow is maximize computational efficiency maintaining good accuracy. This achieved...
The characteristics of field electron and ion emission change when the space charge formed by emitted is sufficient to suppress extracting electric field. This phenomenon well described for planar emitting diodes one dimensional (1D) theory. Here we generalize any 3D geometry deriving scaling laws describing suppression in weak regime. We propose a novel corrected equivalent diode model, which describes effects terms 1D theory, utilizing correction factor that adjusts diode's...
Abstract We performed multiscale-multiphysics simulations for W, Mo and Cu nanotips under high electric field to investigate their structural evolution thermal runaway process. The critical values the prebreakdown condition are predicted be 311 MV m −1 , 570 675 Cu, W respectively ( R 0 = 1 nm, H 100 nm). boiling point of metal is found a good predictor strength initiation runaway. For made refractory metals such as Mo, process determined by rapid growth small protrusions subsequent...
The shape memory effect and pseudoelasticity in Cu nanowires represent a possible pair of mechanisms that prevents high aspect ratio nanosized field electron emitters from being stable at room temperature permits their growth under electric field. By utilizing hybrid electrodynamics–molecular dynamics simulations, we show global 1 GV m−1 or more significantly increases the stability critical spontaneous reorientation 〈100〉 emitters. We also studied tips stabilizing an external applied is...
During the course of a space mission unexpected events can occur regardless rigorous testing. In order to ensure ability spacecraft recover and adapt new situations, it may be necessary update firmware for resolving software issues, work around hardware problems, or introduce features. The importance remote updates as well method calculate an indicative value flexibility in missions is summarized by R. Nilchiani [1].
High electric fields in particle accelerators cause vacuum breakdowns the accelerating structures. The are thought to be initiated by modification of material surface geometry under high fields. These modifications shape protrusions enhance field locally due increased curvature. Using molecular dynamics, we simulate behaviour Cu containing a near-surface Fe precipitate field. We find that presence can nucleation dislocations material, leading appearance atomic steps on surface. Steps...
We propose a novel tool to perform electrodynamics-molecular dynamics and electrodynamics-kinetic Monte Carlo simulations. The generates finite elements in- outside the atomistic domain, uses them solve system of linear differential equations offers interface output results into shows high tolerance against crystallographic orientation in material robustness dynamic processes there.
Abstract Swift heavy ion (SHI)-induced shape modification of metal nanoparticles (NPs) embedded in an insulating matrix has been reported many experimental studies. The shaping process was studied theoretically by modeling transport the heat generated electron excitations during a SHI impact on NP. These models have assumed that interface between and does not alter flow. However, difference Fermi level bottom conduction band insulator may result significant energy barrier obstructs free flow...
Vacuum arcing (also known as breakdown), is a major limiting factor in various applications such particle accelerators, fusion reactors etc. Although it well-established that vacuum arcs appear after intense Field electron Emission (FE), the physical mechanism leads from FE to ignition of plasma not yet understood. A common hypothesis excessive heating cathode, which causes its deformation, and eventually material evaporation formation. However, this process has never been observed...
Onset of vacuum arcing near a metal surface is often associated with nanoscale asperities, which may dynamically appear due to different processes ongoing in the and subsurface layers presence high electric fields.Thermally activated processes, as well plastic deformation caused by tensile stress an applied field, are usually not accessible atomistic simulations because long time needed for these occur.On other hand, finite element methods, able describe process deformations materials at...
The suppression of field electron emission by space charge (SC) is described for planar diodes the one dimensional (1D) theory. Here we generalize in 3D deriving scaling behavior weak SC regime. We propose a corrected equivalent diode model, which describes effects any geometry terms 1D theory, utilizing correction factor that adjusts characteristics suppression. validate our theory comparing it to both numerical calculations and existing experimental data, either can be used obtain factor.
Vacuum arcs have been studied intensively for more than a century. Yet, the physical mechanisms involved in their ignition remain unclear, mainly due to extreme nature and high complexity of processes involved. In order investigate such complex phenomena, multi-scale multi-physics simulations that concurrently capture various are necessary. This work gives an overview recent advancements vacuum arc phenomena. Such include molecular dynamics model movement atoms under heating electromagnetic...