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NASA NTRS2019

Design of Low Inductance Busbar for 500 kVA Three-Level ANPC Converter

The adoption of SiC devices in high power applications enables higher switching speed, which requires lower circuit parasitic inductance to reduce the voltage overshoot. This paper presents the design of a busbar for a 500 kVA three-level active natural clamped converter. The layout of the busbar is discussed in detail based on the analysis of the multiple commutation loops, magnetic cancelling effect, and DC-link capacitor placement. The loop inductance of the designed busbar is verified with simulation, impedance measurements and converter experiment. The results can match with each other and the inductances of small and large loop are 6.5 nH and 17.5 nH respectively, which is significantly lower than the busbars of NPC type converters in other references.

SiC MOSFET↗

DOE OSTI2020

Catalytic Enhancement of Inductively Heated Fe 3 O 4 Nanoparticles by Removal of Surface Ligands

Abstract Heat management in catalysis is limited by each material's heat transfer efficiencies, resulting in energy losses despite current thermal engineering strategies. In contrast, induction heating of magnetic nanoparticles (NPs) generates heat at the surface of the catalyst where the reaction occurs, reducing waste heat via dissipation. However, the synthesis of magnetic NPs with optimal heat generation requires interfacial ligands, such as oleic acid, which act as heat sinks. Surface treatments using tetramethylammonium hydroxide (TMAOH) or pyridine are used to remove these ligands before applications in hydrophilic media. In this study, Fe 3 O 4 NPs are surface treated to study the effect of induction heating on the catalytic oxidation of 1‐octanol. Whereas TMAOH was unsuccessful in removing oleic acid, pyridine treatment resulted in a roughly 2.5‐fold increase in heat generation and product yield. Therefore, efficient surfactant removal has profound implications in induction heating catalysis by increasing the heat transfer and available surface sites.

Moura, Natalia S.↗

DOE OSTI2018

Development of Thermal Kinetic Inductance Detectors Suitable for X-ray Spectroscopy

We report on the development of thermal kinetic inductance detectors (TKIDs) suitable to perform X-ray spectroscopy measurements. The aim is to implement MKIDs sensors working in thermal quasi-equilibrium mode to detect X-ray photons as pure calorimeters. The thermal mode is a variation on the MKID classical way of operation that has generated interest in recent years. TKIDs can offer the MKIDs inherent multiplexibility in the frequency domain, a high spatial resolution comparable with CCDs, and an energy resolution theoretically limited only by thermodynamic fluctuations across the thermal weak links. Microresonators are built in Ti/TiN multilayer technology with the inductive part thermally coupled with a metal absorber on a suspended SiN membrane, to avoid escape of phonons from the film to the substrate. The mid-term goal is to optimize the single-pixel design in terms of superconducting critical temperatures, internal quality factors, kinetic inductance and spectral energy resolution. The final goal is to realize a demonstrator array for a next generation thousand pixels X-ray spectrometer. In this contribution, the status of the project after one year of developments is reported, with detailed reference to the microresonators design and simulations and to the fabrication process.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2018

Fatigue and Fracture Behavior of Induction-Hardened and Superimposed Mechanically Post-treated Steel Surface Layers

This paper focuses on the effect of induction hardening and superimposed stroke peening, as mechanical post-treatment, on the fatigue and fracture behavior of gas engine 50CrMo4 steel crankshafts. Comprehensive analysis in regard to local microstructure, hardness and residual stress profile in depth is performed to examine the local characteristics of the investigated crankshafts and the representative notched round specimens. An evaluation of the equivalent von Mises residual stress condition in depth demonstrates an increase by over 70% of the average compressive residual stress state due to the superimposed stroke peening compared to the induction-hardened condition. Rotating bending fatigue tests reveal that the additional stroke-peening process elevates the high-cycle fatigue strength of the induction-hardened surface layer by 20%, which validates the beneficial effect of the enhanced compressive residual stress state. An extensive fracture surface analysis presents the position of crack initiation for each investigated manufacturing condition indicating that the failure origin preferably starts at the surface for higher load levels. On the contrary, the crack initiation shifts beneath the hardened layer in case of lower load levels leading to subsurface failure origin.

36 MATERIALS SCIENCE↗

DOE OSTI2019

nab-Paclitaxel-based induction chemotherapy followed by cisplatin and radiation therapy for human papillomavirus-unrelated head and neck squamous-cell carcinoma

In patients with locally advanced human papillomavirus (HPV)-unrelated head and neck squamous-cell carcinoma (HNSCC), cisplatin and radiation therapy (CisRT) resulted in a local–regional recurrence (LRR) rate of 35%, progression-free survival (PFS) of 49%, and overall survival (OS) of 60%. We, and others, showed that nab-paclitaxel is an active agent in metastatic and locally advanced HNSCC. The aim of this report was to assess the efficacy of nab-paclitaxel-based induction chemotherapy and CisRT in HPV-unrelated HNSCC. We performed a retrospective single-institution analysis of patients treated with nab-paclitaxel-based chemotherapy and CisRT. Key inclusion criteria included stage III–IV HPV-unrelated HNSCC. Induction chemotherapy included nab-paclitaxel and cisplatin (AP), AP + 5-fluorouracil (APF), or APF + Cetuximab (APF-C). Endpoints included LRR, overall relapse, PFS, and OS. Thirty-eight patients were the subject of this analysis. Patient characteristics included median age 59 years (IQR: 54–64) and smoking history in 36 patients (95%). Primary tumor sites included larynx/hypopharynx (27), p16 negative oropharynx (10), and oral cavity (1). Most patients had bulky disease: 82% T{sub 3–4} (n = 31) and 74% N{sub 2b–3} (n = 28). Median follow-up was 44 months (IQR: 23–59). The three-year LRR rate was 16% (95% confidence interval [CI] 7–34) and the overall relapse rate was 22% (95% CI 11–41). The three-year PFS was 64% (95% CI 46–77) and OS was 72% (95% CI 54–84). Among patients with HPV-unrelated HNSCC, nab-paclitaxel-based induction chemotherapy and CisRT resulted in a lower-than-expected rate of LRR and more favorable PFS and OS compared to historical results with CisRT.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2014

Tolerance induction between two different strains of parental mice prevents graft-versus-host disease in haploidentical hematopoietic stem cell transplantation to F1 mice

Highlights: • Injection of UVB-irradiated iDCs induces alloantigen tolerance. • This alloantigen tolerance may be associated regulatory T cell induction. • Tolerant mice serve as bone marrow donors reduces GVHD to their F1 recipients in allo-HSCT. • Tolerance is maintained in F1 recipients for long time post HSCT. - Abstract: Haploidentical hematopoietic stem cell transplantation (Haplo-HSCT) has been employed worldwide in recent years and led to favorable outcome in a group of patients who do not have human leukocyte antigen (HLA)-matched donors. However, the high incidence of severe graft-versus-host disease (GVHD) is a major problem for Haplo-HSCT. In the current study, we performed a proof of concept mouse study to test whether induction of allogeneic tolerance between two different parental strains was able to attenuate GVHD in Haplo-HSCT to the F1 mice. We induced alloantigen tolerance in C3H mice (H-2k) using ultraviolet B (UVB) irradiated immature dendritic cells (iDCs) derived from the cultures of Balb/c bone marrow cells. Then, we performed Haplo-HSCT using tolerant C3H mice as donors to F1 mice (C3H × Balb/c). The results demonstrated that this approach markedly reduced GVHD-associated death and significantly prolonged the survival of recipient mice in contrast to the groups with donors (C3H mice) that received infusion of non-UVB-irradiated DCs. Further studies showed that there were enhanced Tregs in the tolerant mice and alloantigen-specific T cell response was skewed to more IL-10-producing T cells, suggesting that these regulatory T cells might have contributed to the attenuation of GVHD. This study suggests that it is a feasible approach to preventing GVHD in Haplo-HSCT in children by pre-induction of alloantigen tolerance between the two parents. This concept may also lead to more opportunities in cell-based immunotherapy for GVHD post Haplo-HSCT.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2018

The TORC1–Nem1/Spo7–Pah1/lipin axis regulates microautophagy induction in budding yeast

Highlights: • TORC1 inactivation induces microautophagy in budding yeast. • Loss of Vps27, but not Atg1, Atg7, or Atg8, was required for TORC1 inactivation-induced microautophagy. • The Nem1/Spo7–Pah1 axis was also critical for microautophagy induction. • The TORC1–Nem1/Spo7–Pah1 axis is a master regulator of microautophagy in yeast. Nutrient starvation and inactivation of target of rapamycin complex 1 (TORC1) protein kinase promotes macroautophagy. Macroautophagy is a lipid-consuming process, and Nem1/Spo7 protein phosphatase and Pah1/lipin phosphatidate phosphatase are activated after TORC1 inactivation, supporting macroautophagy induction in the budding yeast Saccharomyces cerevisiae. On the other hand, whether and how microautophagy, which also consumes lipids, is regulated by TORC1 is controversial. Here we show that TORC1 inactivation induces microautophagy in budding yeast. Vps27, but not Atg1, Atg7, or Atg8, was required for TORC1 inactivation-induced microautophagy. Furthermore, the Nem1/Spo7–Pah1 axis was also critical for microautophagy induction. Thus, the TORC1–Nem1/Spo7–Pah1 axis is a master regulator of not only macroautophagy but also microautophagy in budding yeast.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2018

Restoration of hair-inductive activity of cultured human follicular keratinocytes by co-culturing with dermal papilla cells

Highlights: • Monocultured human ORS cells lose hair-inductive activity (trichogenicity). • The trichogenicity of human ORS cells can be restored by co-culturing with human DP cells. • Human DP cells regulate expression of a number of genes in co-cultured ORS cells. Hair follicle outer root sheath (ORS) cells can be expanded in vitro, but often lose receptivity to hair-inducing dermal signals. Recent studies have shown hair-inductive activity (trichogenicity) can be restored in rat ORS cells expanded with a fibroblast feeder by co-culturing with rat vibrissae dermal papilla (DP) cells. In this study, we investigated whether the trichogenicity of human ORS cells can be restored by co-culturing with human DP cells. ORS cells from human scalp hair follicles were cultured independently or with DP cells for 5 days and implanted into nude mice alongside freshly isolated neonatal mouse dermal cells. Although there was no hair induction when monocultured ORS cells were implanted, it was observed in co-cultured ORS cells. We also observed differential regulation of a number of genes in ORS cells co-cultured with DP cells compared to monocultured ORS cells as examined by microarray. Taken together, our data strongly suggest that human DP cells restore the trichogenicity of co-cultured ORS cells by influencing ORS gene expression through paracrine factors.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2026

A Full-Induction Magnetohydrodynamics Solver for Liquid Metal Fusion Blankets in Vertex-CFD

Multiphysics modeling of liquid metal fusion blankets, which produce tritium and convert energy of neutrons created via fusion reactions into heat, is crucial for predicting performance, ensuring structural integrity, and optimizing energy production. While traditional blanket modeling of liquid metal flows during normal steady operating conditions commonly employs the inductionless approximation of the magnetohydrodynamics (MHD) equations, transient scenarios, when the plasma-confining magnetic field varies on millisecond time scales, require a full-induction MHD approach that dynamically evolves the magnetic field via the time-dependent induction equation. This paper presents the formulation, implementation, and initial verification of a full-induction MHD solver integrated within the open-source Vertex-CFD framework, which aims to achieve tight multiphysics coupling, a flexible software design enabling easy extension and addition of physics models, and performance portability across computing platforms. The solver utilizes finite element spatial discretization, implicit Runge–Kutta time integration, and an inexact Newton method to solve the resulting discrete nonlinear system, leveraging Trilinos packages for efficient computation. Verification against selected benchmark problems demonstrates accuracy and robustness of the solver. Furthermore, when the solver is applied to an idealized blanket model in 2.5D and full 3D, results obtained with Vertex-CFD are in good agreement with recently published quasi-2D simulations. These findings establish a computational foundation for future simulations of transient MHD phenomena in liquid metal blankets with Vertex-CFD, and open avenues for future extensions and performance optimizations.

Endeve, Eirik [ORNL] (ORCID:0000000312519507)↗

DOE OSTI2013

MRI Predictive Factors for Tumor Response in Rectal Cancer Following Neoadjuvant Chemoradiation Therapy - Implications for Induction Chemotherapy?

Purpose: Clinical and magnetic resonance imaging (MRI) characteristics at baseline and following chemoradiation therapy (CRT) most strongly associated with histopathologic response were investigated and survival outcomes evaluated in accordance with imaging and pathological response. Methods and Materials: Responders were defined as mrT3c/d-4 downstaged to ypT0-2 on pathology or low at risk mrT2 downstaged to ypT1 or T0. Multivariate logistic regression of baseline and posttreatment MRI: T, N, extramural venous invasion (EMVI), circumferential resection margin, craniocaudal length <5 cm, and MRI tumor height ≤5 cm were used to identify independent predictor(s) for response. An association between induction chemotherapy and EMVI status was analyzed. Survival outcomes for pathologic and MRI responders and nonresponders were analyzed. Results: Two hundred eighty-one patients were eligible; 114 (41%) patients were pathology responders. Baseline MRI negative EMVI (odds ratio 2.94, P=.007), tumor height ≤5 cm (OR 1.96, P=.02), and mrEMVI status change (positive to negative) following CRT (OR 3.09, P<.001) were the only predictors for response. There was a strong association detected between induction chemotherapy and ymrEMVI status change after CRT (OR 9.0, P<.003). ymrT0-2 gave a positive predictive value of 80% and OR of 9.1 for ypT0-2. ymrN stage accuracy of ypN stage was 75%. Three-year disease-free survival for pathology and MRI responders were similar at 80% and 79% and significantly better than poor responders. Conclusions: Tumor height and mrEMVI status are more important than baseline size and stage of the tumor as predictors of response to CRT. Both MRI- and pathologic-defined responders have significantly improved survival. “Good response” to CRT in locally advanced rectal cancer with ypT0-2 carries significantly better 3-year overall survival and disease-free survival. Use of induction chemotherapy for improving mrEMVI status and knowledge of MRI predictive factors could be taken into account in the pursuit of individualized neoadjuvant treatments for patients with rectal cancer.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2017

Cold crucible induction melter test for crystalline ceramic waste form fabrication: A feasibility assessment

The first scaled proof-of-principle cold crucible induction melter (CCIM) test to process a multiphase ceramic waste form from a simulated combined (Cs/Sr, lanthanide and transition metal fission products) commercial used nuclear fuel waste stream was recently conducted in the United States. X-ray diffraction, 2-D X-ray absorption near edge structure (XANES), electron microscopy, inductively coupled plasma-atomic emission spectroscopy (and inductively coupled plasma-mass spectroscopy for Cs), and product consistency tests were used to characterize the fabricated CCIM material. Characterization analyses confirmed that a crystalline ceramic with a desirable phase assemblage was produced from a melt using a CCIM. We identified primary hollandite, pyrochlore/zirconolite, and perovskite phases in addition to minor phases rich in Fe, Al, or Cs. The material produced in the CCIM was chemically homogeneous and displayed a uniform phase assemblage with acceptable aqueous chemical durability.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2013

Silencing of Hsp27 and Hsp72 in glioma cells as a tool for programmed cell death induction upon temozolomide and quercetin treatment

The aim of the present study was to investigate whether silencing of Hsp27 or Hsp72 expression in glioblastoma multiforme T98G and anaplastic astrocytoma MOGGCCM cells increases their sensitivity to programmed cell death induction upon temozolomide and/or quercetin treatment. Transfection with specific siRNA was performed for the Hsp gene silencing. As revealed by microscopic observation and flow cytometry, the inhibition of Hsp expression was correlated with severe apoptosis induction upon the drug treatment studied. No signs of autophagy were detected. This was correlated with a decreased mitochondrial membrane potential, increased level of cytochrome c in the cytoplasm, and activation of caspase 3 and caspase 9. All these results suggest that the apoptotic signal was mediated by an internal pathway. Additionally, in a large percentage of cells treated with temozolomide, with or without quercetin, granules within the ER system were found, which was accompanied by an increased level of caspase 12 expression. This might be correlated with ER stress. Quercetin and temozolomide also changed the shape of nuclei from circular to “croissant like” in both transfected cell lines. Our results indicate that blocking of Hsp27 and Hsp72 expression makes T98G cells and MOGGCCM cells extremely vulnerable to apoptosis induction upon temozolomide and quercetin treatment and that programmed cell death is initiated by an internal signal. - Highlights: • Hsps gene silencing induced severe apoptosis upon temozolomide–quercetin treatment • Apoptosis in transfected glioma cells was initiated by internal signal • Programmed cell death was preceded by ER stress • Temozolomide–quercetin treatment changed nuclei shape in transfected glioma cells.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2021

Injectable platelet rich fibrin facilitates hair follicle regeneration by promoting human dermal papilla cell proliferation, migration, and trichogenic inductivity

Hair follicle regeneration has been successful in mice but failed in human being for years. Dermal papilla cells, a specialized mesenchymal stem cell derived from dermal papilla within hair follicles, is considered the key cells for hair follicle regeneration function as both regeneration initiator and regulator. Injectable platelet rich fibrin (i-PRF), a novel biomaterial rich in a variety of growth factors and three-dimensional scaffolds, has shown promising effects on tissue regeneration. In this study, we aimed to evaluate the application of i-PRF in human hair follicle regeneration by examining the biological effects of i-PRF on human dermal papilla cells (hDPCs). Biomaterial compatibility, cell viability, proliferation, migration, alkaline phosphatase activity and trichogenic inductivity were assessed after exposing hDPCs to different concentrations of i-PRF extracts. In addition, we investigated the ultrastructure of i-PRF with all cell components filtered. The results revealed that i-PRF possessing excellent biocompatibility and could significantly promote hDPCs proliferation, migration, and trichogenic inductivity. Furthermore, the concentration of i-PRF is able to remarkably influence hDPCs behavior in a dose-dependent pattern. Different concentrations exhibited differential effects on hDPCs behavior. In general, lower concentration promotes cell proliferation better than higher concentration, while higher concentration promotes cell function better reversely. Best concentration for hDPCs in vitro expending is 1% concentration. 20% concentration is optimal for hair follicle regeneration. In summary, our findings concluded that i-PRF facilitates hair follicle regeneration by promoting human dermal papilla cell proliferation, migration, and trichogenic inductivity.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2014

Anomalous satellite inductive peaks in alternating current response of defective carbon nanotubes

AC response of defective metallic carbon nanotubes is investigated from first principles. We found that capacitive peaks appear at electron scattering states. Moreover, we show that satellite inductive peaks are seen adjacent to a main capacitive peak, which is in contrast to the conductance spectra having no satellite features. The appearance of satellite inductive peaks seems to depend on the scattering states. Our analysis with a simple resonant scattering model reveals that the origin of the satellite inductive peaks can be understood by just one parameter, i.e., the lifetime of electrons at a defect state.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2014

Response to “Comment on ‘General rotating quantum vortex filaments in the low-temperature Svistunov model of the local induction approximation’” [Phys. Fluids 26, 119101 (2014)]

In R. A. Van Gorder, “General rotating quantum vortex filaments in the low-temperature Svistunov model of the local induction approximation,” Phys. Fluids 26, 065105 (2014) I discussed properties of generalized vortex filaments exhibiting purely rotational motion under the low-temperature Svistunov model of the local induction approximation. Such solutions are stationary in terms of translational motion. In the Comment [N. Hietala, “Comment on ‘General rotating quantum vortex filaments in the low-temperature Svistunov model of the local induction approximation’ [Phys. Fluids 26, 065105 (2014)],” Phys. Fluids 26, 119101 (2014)], the author criticizes my paper for not including translational motion (although it was clearly stated that the filament motion was assumed rotational). As it turns out, if one is interested in studying the geometric structure of solutions (which was the point of my paper), one obtains the needed qualitative results on the structure of such solutions by studying the purely rotational case. Nevertheless, in this Response I shall discuss the vortex filaments that have both rotational and translational motions. I then briefly discuss why one might want to study such generalized rotating filament solutions, in contrast to simple the standard helical or planar examples (which are really special cases). I also discuss how one can study the time evolution of filaments which exhibit more complicated dynamics than pure translation and rotation. Doing this, one can study non-stationary solutions which initially appear purely rotational and gradually display other dynamics as the filaments evolve.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Computational hydrodynamics and optical performance of inductively-coupled plasma adaptive lenses

This study addresses the optical performance of a plasma adaptive lens for aero-optical applications by using both axisymmetric and three-dimensional numerical simulations. Plasma adaptive lenses are based on the effects of free electrons on the phase velocity of incident light, which, in theory, can be used as a phase-conjugation mechanism. A closed cylindrical chamber filled with Argon plasma is used as a model lens into which a beam of light is launched. The plasma is sustained by applying a radio-frequency electric current through a coil that envelops the chamber. Four different operating conditions, ranging from low to high powers and induction frequencies, are employed in the simulations. The numerical simulations reveal complex hydrodynamic phenomena related to buoyant and electromagnetic laminar transport, which generate, respectively, large recirculating cells and wall-normal compression stresses in the form of local stagnation-point flows. In the axisymmetric simulations, the plasma motion is coupled with near-wall axial striations in the electron-density field, some of which propagate in the form of low-frequency traveling disturbances adjacent to vortical quadrupoles that are reminiscent of Taylor-Görtler flow structures in centrifugally unstable flows. Although the refractive-index fields obtained from axisymmetric simulations lead to smooth beam wavefronts, they are found to be unstable to azimuthal disturbances in three of the four three-dimensional cases considered. The azimuthal striations are optically detrimental, since they produce high-order angular aberrations that account for most of the beam wavefront error. A fourth case is computed at high input power and high induction frequency, which displays the best optical properties among all the three-dimensional simulations considered. In particular, the increase in induction frequency prevents local thermalization and leads to an axisymmetric distribution of electrons even after introduction of spatial disturbances. The results highlight the importance of accounting for spatial effects in the numerical computations when optical analyses of plasma lenses are pursued in this range of operating conditions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

Increasing the magnetic-field capability of the magneto-inertial fusion electrical discharge system using an inductively coupled coil

Magnetized high energy density physics (HEDP) is a very active and relatively unexplored field that has applications in inertial confinement fusion, astrophysical plasma science, and basic plasma physics. A self-contained device, the Magneto-Inertial Fusion Electrical Discharge System, MIFEDS [G. Fiksel et al., Rev. Sci. Instrum. 86, 016105 (2015)], was developed at the Laboratory for Laser Energetics to conduct magnetized HEDP experiments on both the OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495–506 (1997)] and OMEGA EP [J. H. Kelly et al., J. Phys. IV France 133, 75 (2006) and L. J. Waxer et al., Opt. Photonics News 16, 30 (2005)] laser systems. Extremely high magnetic fields are a necessity for magnetized HEDP, and the need for stronger magnetic fields continues to drive the redevelopment of the MIFEDS device. It is proposed in this paper that a magnetic coil that is inductively coupled rather than directly connecting to the MIFEDS device can increase the overall strength of the magnetic field for HEDP experiments by increasing the efficiency of energy transfer while decreasing the effective magnetized volume. A brief explanation of the energy delivery of the MIFEDS device illustrates the benefit of inductive coupling and is compared to that of direct connection for varying coil size and geometry. Finally, a prototype was constructed to demonstrate a 7-fold increase in energy delivery using inductive coupling.

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

Power matching to pulsed inductively coupled plasmas

Matching of power delivery to nonlinear loads in plasma processing is a continuing challenge. Plasma reactors used in microelectronics fabrication are increasingly multi-frequency and/or pulsed, producing a non-linear and, in many cases, non-steady state electrical termination that can complicate efficient power coupling to the plasma. This is particularly the case for pulsed inductively coupled plasmas where the impedance of the plasma can significantly change during the start-up-transient and undergo an E–H (capacitive-to-inductive) transition. In this paper, we discuss the results from a computational investigation of the dynamics of power matching to pulsed inductively coupled plasmas (Ar/Cl 2 mixtures of tens of mTorr pressure) using fixed component impedance matching networks and their consequences on plasma properties. In this investigation, we used set-point matching where the components of the matching network provide a best-case impedance match (relative to the characteristic impedance of the power supply) at a chosen time during the pulsed cycle. Matching impedance early during the pulse enables power to feed the E-mode, thereby emphasizing capacitive coupling and large excursions in the plasma potential. This early power coupling enables a more rapid ramp-up in plasma density while being mismatched during the H-mode later in the pulse. The early match also produces more energetic ion bombardment of surfaces. Matching late in the pulse diminishes power dissipated in the E-mode at the cost of also reducing the rate of increase in plasma density.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗