P. C. Efthimion
A5001129997- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- Superconducting Materials and Applications
- Gyrotron and Vacuum Electronics Research
- Particle Accelerators and Free-Electron Lasers
- Nuclear Physics and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Atomic and Subatomic Physics Research
- High-pressure geophysics and materials
- Ion-surface interactions and analysis
- Pulsed Power Technology Applications
- Metal and Thin Film Mechanics
- Advanced X-ray Imaging Techniques
- Nuclear reactor physics and engineering
- Solar and Space Plasma Dynamics
- Mass Spectrometry Techniques and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Electrostatic Discharge in Electronics
- Dust and Plasma Wave Phenomena
Princeton University
2010-2024
Princeton Plasma Physics Laboratory
2015-2024
Lawrence Livermore National Laboratory
2018-2021
Colorado State University
2021
University of Michigan–Ann Arbor
2016-2019
University of Science and Technology of China
2019
University of Rochester
2019
Energetics (United States)
2019
Beijing Normal University
2019
Los Alamos National Laboratory
1991-2016
Order-of-magnitude improvements in the level and duration of current driven by lower-hybrid waves have been achieved PLT tokamak. Steady currents up to 165 kA maintained for 3.5 sec 420 0.3 800-MHz rf power alone. The principal carrier appears be a high-energy (\ensuremath{\sim} 100-keV) electron tail, concentrated central 20- 40-cm core 80-cm-diam discharge column.
Neutral-beam heating of plasmas in the Tokamak Fusion Test Reactor at low preinjection densities [${n}_{e}$(0)\ensuremath{\simeq}${10}^{19}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$] were characterized by ${T}_{e}$(0)=6.5 keV, ${T}_{i}$(0)=20 ${n}_{e}$(0)=7\ifmmode\times\else\texttimes\fi{}${10}^{19}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$, ${\ensuremath{\tau}}_{E}$=170 msec, ${\ensuremath{\beta}}_{\mathrm{theta}}$=2, and a d(d,n${)}^{3}$He neutron emission rate ${10}^{16}$...
Dielectronic satellite spectra of Fe XXV near 1.8500 \AA{} have been observed from PLT (Princeton Large Torus) tokamak plasma discharges for electron temperatures in the range 1.5 to 3 keV and an density 2\ifmmode\times\else\texttimes\fi{}${10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. The temperature was independently determined cyclotron radiation emitted by plasma. quality allows a detailed comparison with theoretical predictions, which is importance view diagnostic applications.
Peak fusion power production of 6.2\ifmmode\pm\else\textpm\fi{}0.4 MW has been achieved in TFTR plasmas heated by deuterium and tritium neutral beams at a total 29.5 MW. These have an inferred central alpha particle density 1.2\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$ without the appearance either disruptive magnetohydrodynamics events or detectable changes Alfv\'en wave activity. The measured loss rate energetic particles agreed with...
Longitudinal compression of a velocity-tailored, intense neutralized ${\mathrm{K}}^{+}$ beam at 300 keV, 25 mA has been demonstrated. The takes place in 1--2 m drift section filled with plasma to provide space-charge neutralization. An induction cell produces head-to-tail velocity ramp that longitudinally compresses the beam, enhancing peak current by factor 50 and producing pulse duration about 3 ns. This measurement confirmed independently two different diagnostic systems.
The collective free-electron laser interaction has been studied at millimeter wavelengths using a newly designed experimental apparatus which features an electron beam of low emittance. Measurements in superradiant amplifier configuration indicate the production 35 MW \ensuremath{\sim}4 mm with efficiency 2.5%. parametric dependence power thresholds and wavelength on pump guide magnetic fields are shown to be agreement theory.
Experimental results from high-power neutral-beam-injection experiments on the Princeton Large Torus tokamak are reported. At highest beam powers (2.4 MW) and lowest plasma densities [${n}_{e}(0)=5\ifmmode\times\else\texttimes\fi{}{10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}3}$], ion temperatures of 6.5 keV achieved. The collisionality ${{\ensuremath{\nu}}_{i}}^{*}$ drops below 0.1 over much radial profile. Electron heating $\frac{\ensuremath{\Delta}{T}_{e}}{{T}_{e}}\ensuremath{\approx}50%$ has...
The time-scales for sawtooth repetition and heat pulse propagation are much longer (tens of milliseconds) in the large tokamak TFTR than previous, smaller tokamaks. This extended time-scale, coupled with more detailed diagnostics, has led us to revisit analysis as a method determine electron diffusivity χe plasma. A combination analytic computer solutions diffusion equation is used clarify previous work develop new methods determining χe. Direct comparison predicted pulses soft-X-ray ECE...
The development of noninductive current drive is great importance in establishing the tokamak as a long-pulse or steady-state fusion reactor. Lower hybrid waves, carrying 200 kW power at 800 MHz, have been launched into Princeton Large Torus to initiate and discharge level excess 100 kA.
Alpha-particle-driven toroidal Alfvén eigenmodes (TAEs) have been observed for the first time in deuterium-tritium (D-T) plasmas on tokamak fusion test reactor (TFTR). These modes are 100–200 ms following end of neutral beam injection with reduced central magnetic shear and elevated safety factor [q0>1]. Mode activity is localized to region discharge r/a<0.5 fluctuation level B̃⊥/B∥∼10−5 mode numbers range n=2–4, consistent theoretical calculations α-TAE stability TFTR.Received 11 November...
The relaxation of core transport barriers in TFTR enhanced reversed shear plasmas has been studied by varying the radial electric field using different applied torques from neutral beam injection. Transport rates and fluctuations remain low over a wide range shear, but increase when local $\mathbf{E}\ifmmode\times\else\texttimes\fi{}\mathbf{B}$ shearing are driven below threshold comparable to fastest linear growth dominant instabilities. Shafranov-shift-induced stabilization alone is not...
The roles of turbulence stabilization by sheared E×B flow and Shafranov shift gradients are examined for Tokamak Fusion Test Reactor [D. J. Grove D. M. Meade, Nucl. 25, 1167 (1985)] enhanced reverse-shear (ERS) plasmas. Both effects in combination provide the basis a positive-feedback model that predicts reinforced suppression with increasing pressure gradient. Local fluctuation behavior at onset ERS confinement is consistent this framework. power required transitions into regime lower when...
After many years of fusion research, the conditions needed for a D–T reactor have been approached on Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. For first time unique phenomena present in plasma are now being studied laboratory plasma. The magnetic experiments to study plasmas using nearly equal concentrations deuterium and tritium carried out TFTR. At maximum power 10.7 MW, 39.5 MW neutral-beam heating, supershot discharge 6.7 high-βp following current rampdown....
Fusion neutron emission of 1.5 × 1014 neutrons · s−1 and 2 1013 neutrons/pulse has been observed for PLT deuterium discharges with up to 2.5 MW neutral-beam injection. The time evolution magnitude are consistent theoretical calculations the fusion reactions caused by energetic injected ions which confined slow down classically. factor-of-two accuracy in absolute calibration is major uncertainty comparison theory. Neutron sawtooth oscillations (⪅ 3%) can also be explained
The Tokamak Fusion Test Reactor (TFTR) (R. J. Hawryluk, to be published in Rev. Mod. Phys.) experiments on high-temperature plasmas, that culminated the study of deuterium–tritium D–T plasmas containing significant populations energetic alpha particles, spanned over two decades from conception completion. During design TFTR, key physics issues were magnetohydrodynamic (MHD) equilibrium and stability, plasma energy transport, impurity effects, reactivity. Energetic particle was given less...
The Tomamak Fusion Test reactor has performed initial high-power experiments with the plasma fueled nominally equal densities of deuterium and tritium. Compared to pure plasmas, energy stored in electron ions increased by \ensuremath{\sim}20%. These increases indicate improvements confinement associated use tritium possibly heating electrons \ensuremath{\alpha} particles created D-T fusion reactions.
The bremsstrahlung emission from the PLT tokamak during lower-hybrid current drive has been measured as a function of angle between magnetic field and direction. is peaked strongly in forward direction, indicating strong anisotropy electron velocity distribution. data demonstrate existence nearly flat tail distribution, which extends out to approximately 500 keV interpreted plateau created by Landau damping waves.
Strong minority proton heating is produced in the Princeton Large Torus through ioncyclotron resonance damping of fast waves at moderate rf power levels. In addition to demonstrating good confinement, energy distribution consistent with Fokker-Planck theory which provides prescription for extrapolation this regime higher levels and other species.
Lower-hybrid current drive requires the generation of a high-energy electron tail anisotropic in velocity. Measurements bremsstrahlung emission produced by this are compared with calculated from reasonable model distributions. The physical basis and sensitivity modelling process described, plasma properties current-driven discharges which can be derived discussed.
A new free-electron laser experiment has been designed at NRL to operate millimeter wavelengths using a collective beam-wave interaction. Critical features of the include an apertured diode which provides low-emittance electron beam, wiggler magnet with adiabatic entrance and exit, operational domain centered around wiggler-guide field gyroresonance. With configured as superradiant amplifier, effects gyroresonance on beam dynamics interaction have studied. Measurements indicate peak power...
Experimental techniques to provide active neutralization for space-charge-dominated beams as well prevent uncontrolled ion beam by stray electrons have been demonstrated. Neutralization is provided a localized plasma injected from cathode arc source. Unwanted secondary produced at the wall halo particle impact are suppressed using radial mesh liner that positively biased inside drift tube. Measurements of current transmission, spot size function axial position, energy, and source conditions...
A new method for obtaining a transient ("pulse") electron heat diffusivity (Xe p) in the radial region 0.38 < r/a 0.56 TFTR [Plasm_l Phys.Controlled Nuc.Fus, Research 1, 51 (1986)] L-mode discharges is presented.Small temperature perturbations were caused by single bursts of • injected impurities which radiated and cooled plasma edge.An iron injection case laser ablation was found to be more definitive than supporting helium gas puff case.In this "cold pulse" method, we cortcentrate on...
Recent operation of the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Research 1, 51 (1986)] has produced plasma equilibria with values Λ≡βp eq+li/2 as large 7, εβp dia≡2μ0ε〈p⊥〉/〈〈Bp〉〉2 1.6, and Troyon normalized diamagnetic beta 26, 209 (1984); Lett. 110A, 29 (1985)], βNdia≡108〈βt⊥〉aB0/Ip 4.7. When dia≳1.25, a separatrix entered vacuum chamber, producing naturally diverted discharge that was sustained for many energy confinement times, τE. The largest stored were...
Measurements of the spatial structure transport coefficients ${\mathrm{He}}^{2+}$ on Tokamak Fusion Test Reactor is reported. profiles were measured using charge-exchange spectroscopy after a helium puff into corotating L-mode plasmas. Modeling shows that diffusivity about 10 ${\mathrm{m}}^{2}$/s near plasma edge and drops to below 1 inside q=1 surface. The convective velocity ranges from 1--3 m/s 20--40 edge. order ion momentum thermal greater than electron diffusivity.
Local particle and heat transport coefficients have been measured in a temperature scan of neutral-beam--heated plasmas with n, ${\mathit{I}}_{\mathit{p}}$, ${\mathit{B}}_{\mathit{c}\mathit{p}\mathit{h}\mathit{i}}$ held constant. The electron is ascertained from flux analysis small density perturbation, the obtained equilibrium power balance. vary as ${\mathit{T}}_{\mathit{e}}^{\mathrm{\ensuremath{\alpha}}}$, where \ensuremath{\alpha}=1.5--2.5. observed dependence predicted by numerical...