T. M. Biewer
A5086190614- Magnetic confinement fusion research
- Plasma Diagnostics and Applications
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Nuclear Physics and Applications
- Solar and Space Plasma Dynamics
- Atomic and Molecular Physics
- Particle Accelerators and Free-Electron Lasers
- Nuclear reactor physics and engineering
- Atomic and Subatomic Physics Research
- Spacecraft and Cryogenic Technologies
- Electron and X-Ray Spectroscopy Techniques
- Advancements in Photolithography Techniques
- Nuclear Materials and Properties
- Muon and positron interactions and applications
- Dust and Plasma Wave Phenomena
- Non-Destructive Testing Techniques
- Radiation Effects in Electronics
- Gas Dynamics and Kinetic Theory
- Analytical Chemistry and Sensors
- Advanced Sensor Technologies Research
Oak Ridge National Laboratory
2016-2025
Culham Science Centre
2008-2024
Culham Centre for Fusion Energy
2006-2024
University of Tennessee at Knoxville
2016-2021
Royal Military Academy
2020
University of Illinois Urbana-Champaign
2018
Princeton Plasma Physics Laboratory
2003-2009
Princeton University
2003-2009
Massachusetts Institute of Technology
2005-2009
Fusion Academy
2006-2007
Type-I edge-localized modes (ELMs) have been mitigated at the JET tokamak using a static external $n=1$ perturbation field generated by four error correction coils located far from plasma. During application of ELM frequency increased factor 4 and amplitude ${\mathrm{D}}_{\ensuremath{\alpha}}$ signal decreased. The energy loss per normalized to total stored energy, $\ensuremath{\Delta}W/W$, dropped values below 2%. Transport analyses shows no or only moderate (up 20%) degradation confinement...
Abstract The JET 2019–2020 scientific and technological programme exploited the results of years concerted engineering work, including ITER-like wall (ILW: Be W divertor) installed in 2010, improved diagnostic capabilities now fully available, a major neutral beam injection upgrade providing record power 2019–2020, tested technical procedural preparation for safe operation with tritium. Research along three complementary axes yielded wealth new results. Firstly, plasma delivered scenarios...
Abstract In 2021 JET exploited its unique capabilities to operate with T and D–T fuel an ITER-like Be/W wall (JET-ILW). This second major campaign (DTE2), after DTE1 in 1997, represented the culmination of a series enhancements—new fusion diagnostics, new injection capabilities, refurbishment plant, increased auxiliary heating, in-vessel calibration 14 MeV neutron yield monitors—as well as significant advances plasma theory modelling community. DTE2 was complemented by sequence isotope...
The 2014–2016 JET results are reviewed in the light of their significance for optimising ITER research plan active and non-active operation. More than 60 h plasma operation with first wall materials successfully took place since its installation 2011. New multi-machine scaling type I-ELM divertor energy flux density to is supported by principle modelling. relevant disruption experiments modelling reported a set three mitigation valves mimicking setup. Insights L–H power threshold Deuterium...
A comparison of the L–H power threshold (Pthr) in JET with all carbon, JET-C, and beryllium/tungsten wall (the ITER-like choice), JET-ILW, has been carried out experiments slow input ramps matched plasma shapes, divertor configuration IP/BT pairs. The low density dependence threshold, namely an increase below a minimum ne,min, which was first observed MkII-GB C subsequently not current MkII-HD geometry, is again JET-ILW. At densities above Pthr reduced by ∼30%, ∼40% when radiation from bulk...
Abstract For the past several years, JET scientific programme (Pamela et al 2007 Fusion Eng. Des . 82 590) has been engaged in a multi-campaign effort, including experiments D, H and T, leading up to 2020 first with 50%/50% D–T mixtures since 1997 ever plasmas ITER mix of plasma-facing component materials. this purpose, concerted physics technology was launched view prepare campaign (DTE2). This paper addresses key elements developed by directly contributing preparation. intense preparation...
The availability of future fusion devices, such as a nuclear science facility or demonstration power station, greatly depends on long operating lifetimes plasma facing components in their divertors. ORNL is designing the Material Plasma Exposure eXperiment (MPEX), superconducting magnet, steady-state device to address material interactions reactors. MPEX will utilize new highintensity source concept based RF technology. This allow experiment cover entire expected conditions divertor reactor....
Linear plasma generators are cost effective facilities to simulate divertor conditions of present and future fusion reactors. They used address important R&D gaps in the science material interactions towards viable facing components for Next generation have be able access expected on targets ITER devices. The steady-state linear device MPEX will this regime with electron temperatures 1–10 eV densities . resulting heat fluxes about 10 MW is designed deliver those a novel Radio Frequency...
Reduction of core-resonant m=1 magnetic fluctuations and improved confinement in the Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch have been routinely achieved through control surface poloidal electric field, but it is now known that has limited part by edge-resonant m=0 fluctuations. Now, refined field control, plus toroidal possible to reduce simultaneously This allowed high-energy runaway electrons, possibly indicative flux-surface...
High-pressure noble gas jet injection is a mitigation technique which potentially satisfies the requirements of fast response time and reliability, without degrading subsequent discharges. Previously reported experiments on DIII-D showed good success at reducing deleterious disruption effects. In this paper, results recent Alcator C-Mod are reported. Jointly, these have greatly improved understanding dynamics processes involved in mitigating both machines, sequence events following observed...
AbstractA new era of fusion research has started with ITER being constructed and DEMO for power demonstration on the horizon. However, nuclear science needs to be developed before can designed. One most crucial complex outstanding issues solved is plasma surface interaction (PSI) in hostile environment a reactor. Not only are materials exposed unprecedented steady-state transient fluxes, but they also neutron fluxes. Both ion fluxes will change micro-structure facing significantly even...
Plasma-facing materials in the divertor of a magnetic fusion reactor have to tolerate steady state plasma heat fluxes range 10 MW/m2 for ∼107 s, addition neutron fluences, which can damage plasma-facing high displacements per atom (dpa) ∼50 dpa. Materials solutions needed components are yet be developed and tested. The material exposure experiment (MPEX) is newly proposed linear device designed deliver necessary flux target testing, including capability expose priori neutron-damaged samples...
New developments in Faraday rotation polarimetry have provided the first measurements of current density profile and core magnetic fluctuations a high-temperature reversed field pinch. This has been achieved by fast-polarimeter system with time response up to 1 μs phase resolution <1 mrad. Recent experiments on Madison Symmetric Torus directly measured radial plasma interior amplitude 33 G, ∼1%. A broad spectrum is observed 100 kHz. Relaxation at sawtooth crash occurs timescale μs....
New profile measurements have allowed the electron thermal diffusivity to be estimated from power balance in Madison Symmetric Torus where magnetic islands overlap and field lines are stochastic. The show that (1) energy transport is conductive not convective, (2) measured diffusivities good agreement with numerical simulations of stochastic transport, (3) greatly reduced near reversal surface diffusion small.
Improved confinement has been achieved in the MST through control of poloidal electric field, but it is now known that improvement limited by bursts an edge-resonant instability. Through refined field control, plus toroidal we have suppressed these bursts. This led to a total beta 15% and reversed-field-pinch-record estimated energy time 10 ms, tenfold increase over standard value which for first substantially exceeds scaling characterized most reversed-field-pinch plasmas.
H-mode operation plays a crucial role in National Spherical Torus Experiment (NSTX) research, allowing higher beta limits due to reduced plasma pressure peaking, and long pulse high bootstrap current fraction. Here, new results are presented the areas of edge localized modes (ELMs), pedestal physics power threshold studies. ELMs several types as reported by aspect ratio tokamaks have been observed: (1) large, Type I ELMs, (2) intermediate-sized III (3) tiny ELMs. Many performance discharges...
Energy confinement comparable with tokamak quality is achieved in the Madison Symmetric Torus (MST) reversed field pinch (RFP) at a high beta and low toroidal magnetic field. Magnetic fluctuations normally present RFP are reduced via parallel current drive outer region of plasma. In response, electron temperature nearly triples doubles. The time increases ten-fold (to ∼10 ms), which L- H-mode scaling values for same plasma current, density, heating power, size shape. Runaway evidenced by...
The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order advance spherical torus (ST) concept. In do this, NSTX utilizes up 7.5 MW neutral beam injection, 6 harmonic fast waves (HHFWs), it operates with plasma currents 1.5 MA elongations 2.6 a field 0.45 T. New facility, diagnostic modelling capabilities developed over past two years have enabled research team make significant progress...
The operational domain for active control of type-I edge localized modes (ELMs) with an n = 1 external magnetic perturbation field induced by the ex-vessel error correction coils on JET has been developed towards more ITER-relevant regimes high plasma triangularity, up to 0.45, normalized beta, 3.0, current 2.0 MA and q95 varied between 3.0 4.8. results ELM mitigation in triangularity plasmas show that frequency ELMs increased a factor 4 during application fields, while energy loss per ELM,...
Dedicated experiments on TF ripple effects the performance of tokamak plasmas have been carried out at JET. The was found to a profound effect plasma rotation. central Mach number, M , defined as ratio rotation velocity and thermal velocity, drop function amplitude (δ) from an average value = 0.40–0.55 for operations standard JET δ 0.08% 0.25–0.40 0.5% 0.1–0.3 1%. should be considered when estimating in ITER. With co-current injection neutral beam (NBI), were rotate direction. However,...
Recent JET experiments have been devoted to the study of (3He)–D plasmas involving radio frequency (RF) heating. This paper starts by discussing RF heating efficiency theoretically expected in such plasmas, covering both relevant aspects wave and particle dynamics. Then it gives a concise summary main conclusions drawn from recent that were either focusing on studying physics or adopting as tool plasma behavior. Depending minority concentration chosen, different physical phenomena are...
The mission of the National Spherical Torus Experiment (NSTX) is demonstration physics basis required to extrapolate next steps for spherical torus (ST), such as a plasma facing component test facility (NHTX) or an ST based (ST-CTF), and support ITER. Key issues are transport, steady state high β operation. To better understand electron new high- k scattering diagnostic was used extensively investigate gyro-scale fluctuations with varying temperature gradient scale length. Results from n = 3...
Proto-MPEX is a linear plasma device being used to study novel RF source concept for the planned Material Plasma Exposure eXperiment (MPEX), which will address plasma-materials interaction (PMI) nuclear fusion reactors. Plasmas are produced using large diameter helicon operating at frequency of 13.56 MHz power levels up 120 kW. In recent experiments has deuterium plasmas with densities ~6 × 1019 m–3 measured location 2 m downstream from antenna and 0.4 target. Previous production on have...
The first-ever successful operation of a tokamak with large area (40% the total plasma surface area) liquid lithium wall has been achieved in Lithium Tokamak eXperiment (LTX). These results were obtained new, electron beam-based evaporation system, which can deposit coating on limiting LTX five-minute period. Preliminary analyses diamagnetic and other data for discharges operated indicate that confinement times increased by 10× compared to helium-dispersed solid coatings. Ohmic energy fresh...