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Die Elektrifizierung unserer Gesellschaft verlangt eine stetige Innovation von elektrischen Bauteilen. Ein vielversprechendes Material ist der transparente Halbleiter ß-Ga2O3. Mit seiner hohen Bandlücke von 4,8 eV bietet das Material gute Voraussetzungen, um im Bereich der Hochleistungselektronik verwendet zu werden. In dieser Arbeit wurden die elektrischen und thermischen Leitungseigenschaften von ß-Ga2O3 untersucht. Dabei werden die Streumechanismen, die den Transport von Elektronen oder Phononen bestimmen, diskutiert. Es wurde eine Abhängigkeit der Ladungsträgerbeweglichkeit von der Schichtdicke der leitfähigen homoepitaktischen ß-Ga2O3 Schichten festgestellt. Während in Volumenproben und dicken Schichten (>150 nm) eine Kombination aus Streuung von Elektronen an Phononen und an ionisierten Störstellen den Transport dominiert, so spielen bei dünnen Schichten Grenzflächeneffekte eine Rolle. Dieser Effekt konnte mit einer modifizierten Variante des Modells nach Bergmann beschrieben werden. Messungen der Wärmeleitfähigkeit haben deren aus der Literatur bekannte Anisotropie bei Raumtemperatur bestätigt. Die Wärmeleitfähigkeit steigt mit sinkender Temperatur, bis bei etwa 30 K ein Maximum von über 1000 W/(mK) erreicht wird. Anhand der mittleren freien Weglängen der Phononen konnte gezeigt werden, dass der Wärmetransport oberhalb von 80 K von Phonon-Phonon Umklappstreuung bestimmt wird. Zwischen 30 K und 80 K zeigt sich der Einfluss von Punktdefektstreuung. Unterhalb von 30 K zeigen sich die Einflüsse der Grenzflächen des Kristalls. Es findet ein Übergang des Phononentransports aus dem diffusiven Transportregime nach Fourier zum ballistischen Phononenstrahlungstransport nach Casimir und Majumdar statt. Eine Betrachtung dieser Materialparameter zeigt, dass ein möglicher Einsatzbereich für ß-Ga2O3 basierte Bauelemente mit flüssigem Stickstoff gekühlte Anwendungen sein könnten. Hier sind sowohl elektrische als auch thermische Parameter gut für hohe Stromdichten geeignet. / The electrification of our society demands continuous innovation in the field of electronic devices. One promising material is the transparent semiconductor ß-Ga2O3. With its high bandgap of 4.8 eV the material shows a great potential to be used in the field of high-power electronics. In this work, the electrical and thermal properties of ß-Ga2O3 have been investigated. The scattering mechanisms that determine the transport of electrons or phonons are discussed. A dependence of the charge carrier mobility on the thickness of the conductive homoepitaxial ß-Ga2O3 layers has been observed. While a combination of electron-phonon scattering (high temperatures) and scattering of electrons on ionized impurities (low temperatures) was shown to dominate the transport in bulk samples and bulk-like layers (>150 nm), in thin layers the influence of boundary scattering plays an increasing role. This effect could be described by a modified version of the Bergmann scattering model for an ideal thin film. Measurements of the thermal conductivity have reproduced the anisotropy previously reported in literature. The thermal conductivity rises with decreasing temperature until it reaches a maximum at approximately 30 K exceeding 1000 W/(mK). The phonon mean free path showed, that the phonon transport is dominated by phonon-phonon Umklapp-scattering above 80 K. Between 30 K and 80 K the influence of point defect scattering was visible. Below 30 K surface effects influence the thermal transport. A transition from diffusive phonon transport in the Fourier model into ballistic phonon-radiative transport described by Casimir and Majumdar takes place. A comparison of these material parameters with those of materials currently used in high-power electronics like SiC and GaN shows, that a possible application for ß-Ga2O3 are devices, that are cooled with liquid nitrogen. In this temperature range the electrical and thermal conductivity of are both well-suited for high current densities.

In order to increase the power density, the discontinuous conducting mode (DCM) and small inductance is adopted for high power bidirectional dc-dc converter. The DCM related current ripple is minimized with multiphase interleaved operation. The turn-off loss caused by the DCM induced high peak current is reduced by snubber capacitor. The energy stored in the capacitor needs to be discharged before device is turned on. A complementary gating signal control scheme is employed to turn on the non-active switch helping discharge the capacitor and diverting the current into the anti-paralleled diode of the active switch. This realizes the zero voltage resonant transition (ZVRT) of main switches. This scheme also eliminates the parasitic ringing in inductor current. This work proposes an inductance and snubber capacitor optimization methodology. The inductor volume index and the inductor valley current are suggested as the optimization method for small volume and the realization of ZVRT. The proposed capacitance optimization method is based on a series of experiments for minimum overall switching loss. According to the suggested design optimization, a high power density hardware prototype is constructed and tested. The experimental results are provided, and the proposed design approach is verified. In this dissertation, a general-purposed power stage model is proposed based on complementary gating signal control scheme and derived with space-state averaging method. The model features a third-order system, from which a second-order model with resistive load on one side can be derived and a first-order model with a voltage source on both sides can be derived. This model sets up a basis for the unified controller design and optimization. The Δ-type model of coupled inductor is introduced and simplified to provide a more clearly physical meaning for design and dynamic analysis. These models have been validated by the Simplis ac analysis simulation. For power flow control, a unified controller concept is proposed based on the derived general-purposed power stage model. The proposed unified controller enables smooth bidirectional current flow. Controller is implemented with digital signal processing (DSP) for experimental verification. The inductor current is selected as feedback signal in resistive load, and the output current is selected as feedback signal in battery load. Load step and power flow step control tests are conducted for resistive load and battery load separately. The results indicate that the selected sensing signal can produce an accurate and fast enough feedback signal. Experimental results show that the transition between charging and discharging is very smooth, and there is no overshoot or undershoot transient. It presents a seamless transition for bidirectional current flow. The smooth transition should be attributed to the use of the complementary gating signal control scheme and the proposed unified controller. System simulations are made, and the results are provided. The test results have a good agreement with system simulation results, and the unified controller performs as expected. / Ph. D.

The demand for high power density keeps driving the development of electromagnetic integration technologies in the field of power electronics. Based on planar homogeneous integrated structures, the mechanism of the electromagnetic integration of passives has been investigated with distributed-parameter models. High order modeling of integrated passives has been developed to investigate the electromagnetic performance. The design algorithm combining electromagnetic design and loss models has been developed to optimize and evaluate the spiral winding structure. High power density of 480 W/in3 has been obtained on the prototype. Due to the structural limitation, the currently applied planar spiral winding structure does not sufficiently utilize the space, and the structure is mechanically vulnerable. The improvement on structures is necessary for further application of integrated passives. The goal of this research is to investigate and evaluate alternative structures for high-power-density integrated passives. The research covers electromagnetic modeling, constructional study, design algorithm, loss modeling, thermal management and implementation technology The symmetric single layer structure and the stacked structure are proposed to overcome the disadvantages of the currently applied planar spiral winding structure. Because of the potential of high power density and low power loss, the stacked structure is selected for further research. The structural characteristics and the processing technologies are addressed. By taking an integrated LLCT module as the study case, the general design algorithm is developed to find out a set of feasible designs. The obtained design maps are used to evaluate the constraints from spatial, materials and processing technologies for the stacked structure. Based on the assumption of one-dimensional magnetic filed on the cross-section and linear current distribution along the longitudinal direction of the stacked structure, the electromagnetic field distribution is analyzed and the loss modeling is made. The experimental method is proposed to measure the loss and to verify the calculation. The power loss in the module leads to thermal issues, which limit the processed power of power electronics modules and thus limit the power density. To further improve the power handling ability of the module, the thermal management is made based on loss estimation. The heat extraction technology is developed to improve the heat removal ability and further improve the power density of integrated passives. The experimental results verify the power density improvement from the proposed stacked structure and the applied heat extraction technology. The power density of 1147 W/in3 (70 W/cm3) is achieved in the implemented LLCT module with the efficiency of 97.8% at output power of 1008W. / Ph. D.

With the development of solar energy, power conversion systems responsible for energy delivering from photovoltaic (PV) modules to ac or dc grid attract wide attentions and have significantly increased installations worldwide. Modular power conversion system has the highest efficiency of maximum power point tacking (MPPT), which can transfer more solar power to electricity. However, this system suffers the drawbacks of low power conversion efficiency and high cost due to a large number of power electronics converters. High-power density can provide potentials to reduce cost through the reduction of components and potting materials. Nowadays, the power electronics converters with the conventional silicon (Si) based power semiconductor devices are developed maturely and have limited improvements regarding in power conversion efficiency and power density. With the availability of wide bandgap devices, the power electronics converters have extended opportunities to achieve higher efficiency and higher power density due to the desirable features of wide bandgap devices, such as low on-state resistance, small junction capacitance and high switching speed. This dissertation focuses on the application of wide bandgap devices to the dc-dc power conversion for the modular PV applications in an effort to improve the power conversion efficiency and power density. Firstly, the structure of gallium-nitride (GaN) device is studied theoretically and characteristics of GaN device are evaluated under testing with both hard-switching and soft-switching conditions. The device performance during steady-state and transitions are explored under different power level conditions and compared with Si based devices. Secondly, an isolated high-efficiency GaN-based dc-dc converter with capability of wide range regulation is proposed for modular PV applications. The circuit configuration of secondary side is a proposed active-boost-rectifier, which merges a Boost circuit and a voltage-doubler rectifier. With implementation of the proposed double-pulse duty cycle modulation method, the active-boost-rectifier can not only serve for synchronous rectification but also achieve the voltage boost function. The proposed converter can achieve zero-voltage-switching (ZVS) of primary side switches and zero-current-switching (ZCS) of secondary side switches regardless of the input voltages or output power levels. Therefore, the proposed converter not only keeps the benefits of highly-efficient series resonant converter (SRC) but also achieves a higher voltage gain than SRC and a wide range regulation ability without adding additional switches while operating under the fixed-frequency condition. GaN devices are utilized in both primary and secondary sides. A 300-W hardware prototype is built to achieve a peak efficiency of 98.9% and a California Energy Commission (CEC) weighted efficiency of 98.7% under nominal input voltage condition. Finally, the proposed converter is designed and optimized at 1-MHz switching frequency to pursue the feature of high-power density. Considering the ac effects under high frequency, the magnetic components and PCB structure are optimized with finite element method (FEM) simulations. Compared with 140-kHz design, the volume of 1-MHz design can reduce more than 70%, while the CEC efficiency only drops 0.8% at nominal input voltage condition. There are also key findings on circuit design techniques to reduce parasitic effects. The parasitic inductances induced from PCB layout of primary side circuit can cause the unbalanced resonant current between positive and negative half cycles if the power loops of two half cycles have asymmetrical parasitic inductances. Moreover, these parasitic inductances reflecting to secondary side should be considered into the design of resonant inductance. The parasitic capacitances of secondary side could affect ZVS transitions and increase the required magnetizing current. Because of large parasitic capacitances, the dead-time period occupies a large percentage of entire switching period in MHz operations, which should be taken into consideration when designing the resonant frequency of resonant network. / Doctor of Philosophy / Solar energy is one of the most promising renewable energies to replace the conventional fossils. Power electronics converters are necessary to transfer power from solar panels to dc or ac grid. Since the output of solar panel is low voltage with a wide range and the grid side is high voltage, this power converter should meet the basic requirements of high step up and wide range regulation. Additionally, high power conversion efficiency is an important design purpose in order to save energy. The existing solutions have limitations of narrow regulating range, low efficiency or complicated circuit structure. Recently, the third-generation power semiconductors attract more and more attentions who can help to reduce the power loss. They are named as wide band gap devices. This dissertation proposed a wide band gap devices based power converter with ability of wide regulating range, high power conversion efficiency and simple circuit structure. Moreover, this proposed converter is further designed for high power density, which reduces more than 70% of volume. In this way, small power converter can merge into the junction box of solar panel, which can reduce cost and be convenient for installations.

For decades, the Silicon-based semiconductors have been the solution for power electronics applications. However, these semiconductors have approached their limits of operation in blocking voltage, working temperature and switching frequency. Due to material superiority, the relatively-new wide-bandgap semiconductors such as Silicon-Carbide (SiC) MOSFETs enable higher voltages, switching frequencies and operating temperatures when compared to Silicon technology, resulting in improved converter specifications. The current study tries to investigate the impact of emerging medium-voltage SiC MOSFETs on industrial motor drive application, where over a quarter of the total electricity in the world is being consumed. Firstly, non-commercial SiC MOSFETs at 3.3 kV and 400 A rating are characterized to enable converter design and simulation based on them. In order to feature the best performance out of the devices under test, an intelligent high-performance gate driver is designed embedding required functionalities and protections. Secondly, total of three converters are targeted for industrial motor drive application at medium-voltage and high-power range. For this purpose the cascaded H-bridge, the modular multilevel converter and the 5-L active neutral point clamped converters are designed at 4.16-, 6.9- and 13.8 kV voltage ratings and 3- and 5 MVA power ratings. Selection of different voltage and power levels is done to elucidate variation of different parameters within the converters versus operating point. Later, comparisons are done between the surveyed topologies designed at different operating points based on Si IGBTs and SiC MOSFETs. The comparison includes different aspects such as efficiency, power density, semiconductor utilization, energy stored in converter structure, fault containment, low-speed operation capability and parts count (for a measure of reliability). Having the comparisons done based on simulation data, an H-bridge cell is implemented using 3.3 kV 400 A SiC MOSFETs to evaluate validity of the conducted simulations. Finally, a novel method is proposed for series-connecting individual SiC MOSFETs to reach higher voltage devices. Considering the fact that currently the SiC MOSFETs are not commercially available at voltages higher above 1.7 kV, this will enable implementation of converters using medium-voltage SiC MOSFETs that are achieved by stacking commercially-available 1.7 kV MOSFETs. The proposed method is specifically developed for SiC MOSFETs with high dv/dt rates, while majority of the existing solutions could only work merely with slow Si-based semiconductors. / Ph. D.

Over the past ten years, there has been increased use of electronic power processing in alternative, sustainable, and distributed energy sources, as well as energy storage systems, transportation systems, and the power grid. Three-phase voltage source converters (VSCs) have become the converter of choice in many ac medium- and high-power applications due to their many advantages, such as high efficiency and fast response. For transportation applications, high power density is the key design target, since increasing power density can reduce fuel consumption and increase the total system efficiency. While power electronics devices have greatly improved the efficiency, overall performance and power density of power converters, using power electronic devices also introduces EMI issues to the system, which means filters are inevitable in those systems, and they make up a significant portion of the total system size and cost. Thus, designing for high power density for both power converters and passive components, especially filters, becomes the key issue for three-phase converters. This dissertation explores two different approaches to reducing the EMI filter size. One approach focuses on the EMI filters itself, including using advanced EMI filter structures to improve filter performance and modifying the EMI filter design method to avoid overdesign. The second approach focuses on reducing the EMI noise generated from the converter using a three-level and/or interleaving topology and changing the modulation and control methods to reduce the noise source and reduce the weight and size of the filters. This dissertation is divided into five chapters. Chapter 1 describes the motivations and objectives of this research. After an examination of the surveyed results from the literature, the challenges in this research area are addressed. Chapter 2 studies system-level EMI modeling and EMI filter design methods for voltage source converters. Filter-design-oriented EMI modeling methods are proposed to predict the EMI noise analytically. Based on these models, filter design procedures are improved to avoid overdesign using in-circuit attenuation (ICA) of the filters. The noise propagation path impedance is taken into consideration as part of a detailed discussion of the interaction between EMI filters, and the key design constraints of inductor implementation are presented. Based on the modeling, design and implementation methods, the impact of the switching frequency on EMI filter weight design is also examined. A two-level dc-fed motor drive system is used as an example, but the modeling and design methods can also be applied to other power converter systems. Chapter 3 presents the impact of the interleaving technique on reducing the system passive weight. Taking into consideration the system propagation path impedance, small-angle interleaving is studied, and an analytical calculation method is proposed to minimize the inductor value for interleaved systems. The design and integration of interphase inductors are also analyzed, and the analysis and design methods are verified on a 2 kW interleaved two-level (2L) motor drive system. Chapter 4 studies noise reduction techniques in multi-level converters. Nearest three space vector (NTSV) modulation, common-mode reduction (CMR) modulation, and common-mode elimination (CME) modulation are studied and compared in terms of EMI performance, neutral point voltage balancing, and semiconductor losses. In order to reduce the impact of dead time on CME modulation, the two solutions of improving CME modulation and compensating dead time are proposed. To verify the validity of the proposed methods for high-power applications, a 100 kW dc-fed motor drive system with EMI filters for both the AC and DC sides is designed, implemented and tested. This topology gains benefits from both interleaving and multilevel topologies, which can reduce the noise and filter size significantly. The trade-offs of system passive component design are discussed, and a detailed implementation method and real system full-power test results are presented to verify the validity of this study in higher-power converter systems. Finally, Chapter 5 summarizes the contributions of this dissertation and discusses some potential improvements for future work. / Ph. D.

The trend towards more and all-electric apparatuses and more electrification will lead to higher electrical demand. Increases in electrical power demand can be provided by either higher currents or higher voltages. Due to "weight" and "voltage" drop, a raise in the current is not preferred; so, "higher voltages" are being considered. Another trend is to reduce the size and weight of apparatuses. Combined, these two trends result in the high voltage, high power density concept. It is expected that by 2030, 80% of all electric power will flow through "power electronics systems". In regards to the high voltage, high power density concept described above, "wide bandgap (WBG) power modules" made from materials such as "SiC and GaN (and, soon, Ga2O3 and diamond)", which can endure "higher voltages" and "currents" rather than "Si-based modules", are considered to be the most promising solution to reducing the size and weight of "power conversion systems". In addition to the trend towards higher "blocking voltage", volume reduction has been targeted for WBG devices. The blocking voltage is the breakdown voltage capability of the device, and volume reduction translates into power density increase. This leads to extremely high electric field stress, E, of extremely nonuniform type within the module, leading to a higher possibility of "partial discharge (PD)" and, in turn, insulation degradation and, eventually, breakdown of the module. Unless the discussed high E issue is satisfactorily addressed and solved, realizing next-generation high power density WBG power modules that can properly operate will not be possible. Contributions and innovations of this Ph.D. work are as follows. i) Novel electric field grading techniques including (a) various geometrical techniques, (b) applying "nonlinear field-dependent conductivity (FDC) materials" to high E regions, and (c) combination of (a) and (b), are developed; ii) A criterion for the electric stress intensity based upon accurate dimensions of a power device package and its "PD measurement" is presented; iii) Guidelines for the electrical insulation design of next-generation high voltage (up to 30 kV), high power density "WBG power modules" as both the "one-minute insulation" and PD tests according to the standard IEC 61287-1 are introduced; iv) Influence of temperature up to 250°C and frequency up to 1 MHz on E distribution and electric field grading methods mentioned in i) is studied; and v) A coupled thermal and electrical (electrothermal) model is developed to obtain thermal distribution within the module precisely. All models and simulations are developed and carried out in COMSOL Multiphysics. / Doctor of Philosophy / In power engineering, power conversion term means converting electric energy from one form to another such as converting between AC and DC, changing the magnitude or frequency of AC or DC voltage or current, or some combination of these. The main components of a power electronic conversion system are power semiconductor devices acted as switches. A power module provides the physical containment and package for several power semiconductor devices. There is a trend towards the manufacturing of electrification apparatuses with higher power density, which means handling higher power per unit volume, leading to less weight and size of apparatuses for a given power. This is the case for power modules as well. Conventional "silicon (Si)-based semiconductor technology" cannot handle the power levels and switching frequencies required by "next-generation" utility applications. In this regard, "wide bandgap (WBG) semiconductor materials", such as "silicon carbide (SiC)"," gallium nitride (GaN)", and, soon, "gallium oxide" and "diamond" are capable of higher switching frequencies and higher voltages, while providing for lower switching losses, better thermal conductivities, and the ability to withstand higher operating temperatures. Regarding the high power density concept mentioned above, the challenge here, now and in the future, is to design compact WBG-based modules. To this end, the extremely nonuniform high electric field stress within the power module caused by the aforementioned trend and emerging WBG semiconductor switches should be graded and mitigated to prevent partial discharges that can eventually lead to breakdown of the module. In this Ph.D. work, new electric field grading methods including various geometrical techniques combined with applying nonlinear field-dependent conductivity (FDC) materials to high field regions are introduced and developed through simulation results obtained from the models developed in this thesis.

With the development of information technology, the market for power management of telecom and computing equipment keeps increasing. Distributed power systems are widely adopted in the telecom and computing applications for the reason of high performance and high reliability. Recently industry brought out aggressively high efficiency requirements for a wide load range for power management in telecom and computing equipment. High efficiency over a wide load range is now a requirement. On the other hand, power density is still a big challenge for front-end AC/DC converters. For DPS systems, front-end AC/DC converters are under the pressure of continuous increasing power density requirement. Although increasing switching frequency can dramatically reduce the passive component size, its effectiveness is limited by the converter efficiency and thermal management. Technologies to further increase the power density without compromising the efficiency need to be studied. The industry today is also at the beginning of transferring their design from analog control to full digital control strategy. Although issues are still exist, reducing components count, reducing the development cycle time, increasing the reliability, enhancing the circuit noise immunity and reducing the cost, all of these benefits indicate a great potential of the digital control. This thesis is focusing on how to improve the efficiency and power density by taking the advantages of the digital control. A novel Ï /2 phase shift two Channel interleaving PFC is developed to shrink the EMI filter size while maintain a good efficiency. A sophisticated power management strategy that associates with phase shedding and adaptive phase angle control is also discussed to increase the efficient for the entire load range without compromising the EMI filter size. The method of current sampling is proposed for Ï /2 phase shift two Channel interleaving PFC and multi-channel adaptive phase angle shift PFC is proposed to accurately extract the average total current information. A noise free current sampling strategy is also proposed that adjusting the sampling edge according to duty cycle information. An isolated ZVS dual boost converter is proposed to be the DC/DC stage of the front-end converter. This PWM converter has similar performance as the LLC resonant converter. It has hold up time extension capability without compromising the normal operation efficiency. It can achieve ZVS for all the switches. The current limit and SR implementation is much easier than LLC. State plane method, which potentially can be extent to other complex topologies, is used to fully study this circuit. All the operation modes are understood through the state plane method. The best operation mode is discovered for the front end applications. Light load efficiency is improved by the proposed pulse skipping method to guarantee the ZVS operation meanwhile reduce the switching frequency. Current limit operation is also proposed to restrict a best operation mode by fully taking the advantage of digital control that precisely control the circuit under the over current condition. High efficiency high power density is achieved by new topology, innovative interleaving, and the sophisticated digital control method. / Master of Science

La pulvérisation cathodique magnétron est un procédé plasma très répandu dans l'industrie pour le dépôt de couches minces. Néanmoins, les exigences des nouvelles applications nécessitent de mieux comprendre, contrôler et maîtriser les processus fondamentaux gouvernant le transport de la matière pour optimiser le procédé. Ce travail de thèse porte sur l'étude du transport des atomes pulvérisés de tungstène (W) en décharge magnétron continu (DC direct current) et pulsée haute puissance (HiPIMS_high power impulse magnétron sputtering). La fluorescence induite par diode laser (TD-LIF) a été mise au point afin de mesurer les fonctions de distribution en vitesse des atomes W pulvérisés. Les mesures ont été calibrées par absorption laser et validées en corrélant avec les vitesses de dépôt. En procédé DC, l'étude de l’influence des paramètres de la décharge (puissance, tension, mélange gazeux Ar/He, distance par rapport à la cible, etc.) a mis en évidence l'évolution spatiale des régimes de transport balistique (atomes énergétiques), diffusif (atomes thermalisés), et mixte (balistique+diffusif). Pour l'étude du procédé HiPIMS, le plasma pulsé a nécessité de développer la TD-LIF résolue en temps (TR-TDLIF). Le degré de liberté supplémentaire qu'offre la dimension temporelle du plasma HiPIMS a permis de mieux comprendre le transport mixte qui représente le cas le plus compliqué. En effet, cela a permis de mesurer la cinétique du transport des atomes pulvérisés en ayant la possibilité de séparer les temps caractéristiques des différents processus / Magnetron sputter deposition is an established and widely used method for the growth of thin films. Nevertheless, the high level of expectations regarding new applications require a better understanding, controlling, mastering of basic processes governing atoms transport in the view of process optimization. This work consist in the study of transport of sputtered W atoms in direct current and high power impulse magnetron discharges (DC and HiPIMS). A tunable diode laser induced fluorescence technique (TD-LIF) has been developed, in order to measure W sputtered atom velocity distribution function. Measurements were calibrated using laser absorption and were corroborated by deposition rate. In DC, the study of the influence of discharge parameters (power, voltage, Ar/He gas mixture, and distance from target, etc.) highlighted spatial evolution of different regimes of transport: ballistic (energetic atoms), diffusive (thermalized atoms), and mixed (ballistic + diffusive). In HiPIMS, pulsed plasma required to develop a time resolved TD-LIF technique (TR-TDLIF). The additional degree of freedom, given by time dimension allowed for a better understanding of mixed transport which represents the most complicated situation. This technique allowed to measure the kinetic of sputtered W atoms while at the same time providing the possibility to separate characteristic time scales of different processes