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Abstract Hoist Levitated Dipole Experiment (LDX) Significant Stored Energy in Thermal Plasma Towards Higher Density Dipole Confined Plasmas No Levitation: 80515025 80515026 Flux Decay of “Ring Current” with ECRH Off Only hot trapped electrons Dipole Edge Power Balance Scaling LDX Phase III Target Plasmas The Levitated Dipole Experiment (LDX) investigates plasmas confined in 1.1 MA Floating dipole coil 6 Levitation Coil Total Heating Power 81001006 0.4 Supported 2.5 kW (2.45 GHz source)! the closed field line dipole magnetic geometry where the plasma stability 4 1.0! ! Levitated 2.5 kW (2.45 GHz source)! ‣ Nb3Sn superconductor 12 kW Levitated 15 kW! Steady state central chordal density Original proposal goal for thermal plasma studies is provided by compressibility and where plasma convection leads to 2 0.2 0.8! ) -2 15 kW, He measurement versus neutral 10 13 3 ‣ Inductively charged by 10 MJ 0 cm 5 kW, He ~10 / cm density peaked profiles and may allow for τE > τp. In the past year, we have 13 ‣ 0.6! 20 pressure for different conditions. 15 kW, D2 charging coil Neutral Pressure 0.0 8 continued to investigate the improved energy and particle confinement 15 5 kW, D2 ‣ peak β order unity (Flux (mWb)) 10 0.4! 5 kW, D2, supported Torr 10 6 when the supports are removed from the plasma. ‣ Up to 2 hour levitation using -6 -0.2 Increasing power increases the core Log 10 5 Current plasmas ~ 15 kW Hot Electron Energy Fraction 0.2! active feedback on upper 0 density and there is large mass effect 4 Of most significance, we observe that: 5 15 -0.4 12 3 ‣ peak density ~ 0.8 x 10 / cm levitation coil > Chord average density 14.0 14.5 15.0 15.5 16.0 16.5 0.0! for the optimal fueling. This 2 -3 A large fraction of the stored energy in levitated plasmas is contained 10 Time (s) 0.0! 0.5! 1.0! 1.5! 2.0! 2.5! 3.0! 3.5! Line Integrated Density ( x10 • m observation is consistent with the ‣ edge temp 15-20 eV Diamagnetic Flux (mWb)! Two component plasma created 16 0 5 0SOL density5 10increases 15 with20 P . p25 is varying30 35 in the bulk electron population. 1 m dipole “natural profiles” (nV = rf 0 ‣ core temp 400 eV ? (see Davis UP8.00054) by multi-frequency ECRH < 10 Neutral Pressure ( !Torr ) 0 The observation of signficant fraction of bulk plasma beta is determined from the 90723004-19 4 constant), where the edge • Eliminating plasma losses along field lines allows observations of a 2.45 GHz ECE (V-band) ‣ thermal peak β ~ 10 % ‣ 2.5 kW, 2.45 GHz 3 nature of the diamagnetic flux signals which show an initial energy decay of the parameters are set by power flow along strong particle pinch leading to a density profile with near equal 6.4 GHz Edge density proportional to power 2 bulk plasma followed by the long decay of the fast particles as also seen in the the scrape off layer (SOL). Here the FY2010 - University of Maryland 28 GHz gyrotron ‣ 2.5 kW, 6.4 GHz A.U. number of particles per flux tube. 1 supported shots. Furthermore, the radiometer, which sees primarily harmonic LDX experiment. The vacuum vessel is 5 m in diameter and the ) improved confinement of He is due to the -3 ‣ 10 kW, 10.5 GHz 0 ECE from the fast electrons, does not show the marked increase that the ‣ 10 kW addition power ( + 55 %) The previously observed low frequency fluctuations are consistent 560 kg superconducting dipole coil is 1.2 m in diameter. 3 slower sonic flow to the wall in the SOL. • ‣ 10 kW, 28 GHz (FY2010) Diamagnetic Flux diamagnetic loops demonstrate. Thus the increase in beta during levitation is ‣ peak density ~ 1.5 x 1012 / cm3 with the required turbulent convection to drive the observed particle 2 largely in the bulk warm electrons. Plasma Diagnostic Set Weber Indeed, probe measurements of density ‣ thermal peak β ~ 20 % -3 1 pinch. γ 10 The significant bulk beta is roughly consistent with a pV = constant profile Improved Confinement with Levitation and temperature at the SOL indicate a Edge Density (cm Inductive 0 1 MW 3-28 MHz CW transmitter installation In future experiments, an optimal levitation control system will be 0 5 10 15 starting with the measured edge Te of ~20 eV. This profile would have core Te ~ nearly linear scaling of density with MagneticChargin equilibriumg Time (sec) 400 eV. (a) Side View Sept. 25, 2009 5 implemented, reflectometer and soft x-ray spectrometer diagnostics will power and a nearly constant edge T is approximatelyInput Power independent (kW) of P ‣ 200 kW ICRF heating ‣ flux loops, Bp coils, Hall effect sensors, levitation system trackers Similar shots Supported e rf be added, and a higher frequency (28GHz) electron cyclotron heating 2 m When levitated, a large increase in density and magnetically measured stored temperature, as predicted by the notion ‣ ~1013 / cm3 density Fast electrons and levitated energy is seen with only modest increase of ECE emission,Upper Hybr idwhich is sensitive that the edge power balance determines Edge temperature ≈ constant source will be added to increase the density of LDX plasmas. In Resonances ‣ peak β order unity ‣ Similar gas fueling mostly to the mirror trapped hot electron population.Cyclotron the edge parameters (see Kesner, et al. preparation for installing a 1MW ICRF transmitter, initial ion cyclotron ‣ X-ray PHA, x-ray detector, 60 GHz & 137 GHz radiometers Resonances ‣ Isotropic, thermal plasma 3-5 x line average density UP8.00052). heating experiments will also be performed. Core parameters Ti=Te, 500 eV core much more peaked interferometer, visible cameras, visible diode and array, survey spectrometer ‣ Thus, assuming the edge scales with ‣ (eV) Te profile with levitation Inward Particle Pinch Observed during Levitated Plasmas Columbia University Fluctuations power and the natural profiles, we can 2-3 x the diamagnetic extrapolate the power levels required to The Levitated Dipole Concept ‣ Edge Isat and Vf probes, Mirnov coils, visible diode arrays, interferometer, fast flux Dramatic Peaking of density profileCatcher seen when Levitated reach the LDX Phase III target plasma visible camera, floating probe array Catcher Open Significant stored energy Raised 4 Channel 28 GHz Gyrotron ECRH UpgradeInput Power (kW)forPSFC LDX MIT Columbia University Lowered Field-Lines Reconstruction of the density conditions. Sept. 25, 2009 6 Edge parameters in warm bulk plasma (b) Top View Interferometer 28 GHz Gyrotron ECRH Upgrade for LDX MHD stability from plasma 6 profile for supported P. C. Michael, P. P. Woskov, J. L. Ellsworth, J. Kesner,University of Maryland S71213003 R. F. Ellis, d compressibility when levitated Interferometer (Radian) (diamond) and levitated Columbia University P. C. Michael, P. P. Woskov,28 J. GHz L. Ellsworth, Vacuum WindowJ. Kesner, PSFC MIT V = ‣ swept, Isat, and floating potential probes B γ γ D. T. Garnier, M. E. Mauel, If p V = p V , then interchange does Observed over all 4 (square) discharges under University of Maryland28 GHz ECD. Resonances T. Garnier, 28 M.in LDXE. Mauel,GHz Columbia GyrotronFused University quartz brazed R. in F.standard Ellis, flangeUniversity of Maryland 1 1 2 2 hmm@ .2798 m In development Resonant Thickness > operating conditions similar conditions with 15 kW m =1, 2, 3, … not change pressure profile. (5.596 mm thick window reflectometer for density profile (peak density) corroboration and internal 28 GHz Gyrotron Installation at LDX m = 2 chosen) 28 GHz EC Resonances in LDX 28 GHz Vacuum Window ‣ 2 II. RESULTS Closed of ECRH. ABSTRACT -A 10 kW, CW, 28 GHz gyrotron is being implemented 28 GHz28 GHzGyrotron Power Installation at LDX Fused quartz brazed in standard flange Drift wave stability for interchange invariant Field-Lines on LDXWaveguide to increase the plasma density and to more fully explore the 44 mm diameter (2a) fluctuations ABSTRACT -A 10 kW, CW, 28more fullyGHz explore gyrotron the is being implemented 28 GHz heating Resonant Thickness potential of high beta plasma stability in a dipole magnetic Waveguide hmm> @ 2798 . m profile The shots analyzed are all deuterium plasmas, and the Supported mode has profile on LDX to increase the plasma density and to Outer closed Rupture Safety Factor (5.596 mm thick window ‣ soft x-ray spectral measurements 0 stability in a dipole magnetic configuration. Higher density increases the heating of ions by thermal 2 28 GHz Power m =1, 2, 3, … d ln T 2 flux‣ heatloop with broad profile acrossh plasma m = 2 chosen) 0 5 10 short-time15 “stripey” and correlation plots are all from consistent with particle potential of high beta plasma ses the heating of ions by thermal equilibration and allows for improved wave propagation in planned §· For η = = , density and time (s) Dipole Dipole S.F. 395¨¸ 24 44 mm diameter (2a) periods where all heating sources are on. The phase configuration. Higher density increa propagation in planned ICRF experiments. This represents over a 50% increase over the Innerin closedhigh field region ©¹a d ln n 3 sources and parallel losses. ws for improved wave Outer closed equilibration and allo flux loop flux loop Rupture Safety Factor 6 velocities were all calculated during periods where ev- over a 50% increase over the present 17 kW ECRH from sources at 2.45, 6.4, and 10.5 GHz. The F-Coil F-Coil 2 temperature profiles are also stationary. S71213004 ‣ antenna designed for direct beam to Interferometer (Radian) ICRF experiments. This represents higher frequency will also make possible access to plasma densities of 1st 28 GHz Absorption §·h ery heating source was on as well.
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