Spheromak formation and operation with background filling gas and a solid flux conserver in CTX

Barnes, Cris W.; Jarboe, T.R.; Henins, I.; Sherwood, A.R.; Knox, S.O.; Gribble, R.F.; Hoida, H.W.; Klingner, P.L.; Lilliequist, Carl G.; Linford, R.K.; Platts, D.; Spencer, Ross L.; Tuszewski, M.

doi:10.1088/0029-5515/24/3/002

Cited by 38 publications

(61 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Assuming T e T i would double this value to give a total volume average ͗b͘ 8%. This is the highest value reported for a driven spheromak and comparable to the highest values reported for a decaying spheromak [20] (transient values of b e,local ഠ 20% have been reported prior to pressure driven instability [21]). …”

supporting

confidence: 70%

Suppression of MHD Fluctuations Leading to Improved Confinement in a Gun-Driven Spheromak

et al. 2002

View full text Add to dashboard Cite

Magnetic fluctuations have been reduced to approximately 1% during discharges on the Sustained Spheromak Physics Experiment by shaping the spatial distribution of the bias magnetic flux in the device. In the resulting quiescent regime, the safety factor profile is nearly flat in the plasma and the dominant ideal and resistive MHD modes are greatly reduced. During this period, the temperature profile is peaked at the magnetic axis and maps onto magnetic flux contours. Energy confinement time is improved over previous reports in a driven spheromak.

show abstract

supporting

confidence: 70%

Suppression of MHD Fluctuations Leading to Improved Confinement in a Gun-Driven Spheromak

et al. 2002

View full text Add to dashboard Cite

show abstract

“…28,29 FMP has a 4.5 m long, 0.75 m radius cylindrical vacuum chamber and the same coaxial plasma gun as the previous Compact Toroid eXperiment ͑CTX͒ at Los Alamos about two decades ago. 30 An electrolytic capacitor bank stores up to 300 kJ of energy and applies a maximum 900 V between the electrodes. The externally applied axial magnetic field strength is about 100 G for all the experimental data presented ͑except for ones with magnetic field explicitly specified͒.…”

Section: Methodsmentioning

confidence: 99%

Dust trajectories and diagnostic applications beyond strongly coupled dusty plasmas

2007

View full text Add to dashboard Cite

Plasma interaction with dust is of growing interest for a number of reasons. On the one hand, dusty plasma research has become one of the most vibrant branches of plasma science. On the other hand, substantially less is known about dust dynamics outside the laboratory strongly coupled dusty-plasma regime, which typically corresponds to 1015m−3 electron density with ions at room temperature. Dust dynamics is also important to magnetic fusion because of concerns about safety and potential dust contamination of the fusion core. Dust trajectories are measured under two plasma conditions, both of which have larger densities and hotter ions than in typical dusty plasmas. Plasma-flow drag force, dominating over other forces in flowing plasmas, can explain the dust motion. In addition, quantitative understanding of dust trajectories is the basis for diagnostic applications using dust. Observation of hypervelocity dust in laboratory enables dust as diagnostic tool (hypervelocity dust injection) in magnetic fusion. In colder plasmas (∼10eV or less), dust with known physical and chemical properties can be used as microparticle tracers to measure both the magnitude and directions of flows in plasmas with good spatial resolution as the microparticle tracer velocimetry.

show abstract

“…In the case with conditioning, the edge poloidal field decay time has increased a factor of 2. The average electron temperature is proportional to the B-field energy decay time [12] and for the discharge with helium shot conditioning and gettering the calculated T e ≥ 50 eV compared to ~25 eV for discharges without conditioning.…”

Section: Impurity Control and Wall Conditioningmentioning

confidence: 99%

Particle control in the sustained spheromak physics experiment

Wood

Hill

Hooper

et al. 2001

Journal of Nuclear Materials

View full text Add to dashboard Cite

In this paper we report on density and impurity measurements in the Sustained Spheromak Physics Experiment (SSPX) which has recently started operation. The SSPX spheromak plasma is sustained by coaxial helicity injection for a duration of 2msec with peak toroidal currents of up to 0.5MA. The plasma-facing components consist of tungsten-coated copper to minimize sputtering. The surfaces are conditioned by a combination of baking at 150 o C, glow discharge cleaning, Titanium gettering, and pulse-discharge cleaning with helium plasmas. In this way we can achieve density control so that the plasma density (~ 1-4×10 20 m -3 ) matches the gas input. Low-density operation is presently limited by breakdown requirements, but we hope that new gas valves with supersonic nozzles will allow for a further reduction in density. We find that the conditioning reduces the impurity radiation to the point where it is no longer important to the energy balance, and long-lived spheromak plasmas are obtained (decay times of 1.5msec). 2 IntroductionIn this paper we discuss power and particle control for the SSPX (Sustained Spheromak Physics Experiment) spheromak device. SSPX began operation in 1999 after it was constructed as part of a renewed US program in alternate confinement concepts.In spheromaks, a very low aspect ratio (A~1.1) toroidal confinement geometry is produced by currents in the plasma itself (the plasma dynamo), rather than by external coils which necessarily thread the vacuum vessel. Elimination of the linked coils could lead to smaller, cheaper power plants. Furthermore, DC or AC potentials applied to external electrodes can sustain the spheromak plasma. At present, it is unknown if the spheromak configuration can provide sufficient energy confinement to allow the plasma to be heated to thermonuclear temperatures (10keV). Recent analysis of previous experimental data [1,2] suggested that adequate core energy confinement could be obtained in these devices and that performance might scale favorably to power reactors. The SSPX device was built to explore this question.The spheromak plasma in SSPX is confined within an R=1.0m, h=0.5m, 1.2cm thick copper flux conserver which serves to maintain the plasma shape via image currents flowing in it. A cross section of the device appears in Fig. 1; magnetic flux surfaces for an ideal MHD equilibrium computed with the CORSICA code are included. The confined plasma (R=0.31m, a>0.25m is isolated from the flux conserver by a thin (less than 1cm wide at the midplane) scrape-off layer (SOL) plasma whose field lines encircle the plasma and connect to the electrode region at the top of the device. In the spheromak the magnetic field lines vary from almost completely poloidal (in the plane of the paper here) near the walls to completely toroidal at the magnetic axis at R=0.31m.The cross section of the shell was designed to minimize the volume of corner regions 3 having open field lines, so it is everywhere conformal to the magnetic flux surfaces except for a 5cm high toroidally unifo...

show abstract

Spheromak formation and operation with background filling gas and a solid flux conserver in CTX

Cited by 38 publications

References 31 publications

Suppression of MHD Fluctuations Leading to Improved Confinement in a Gun-Driven Spheromak

Suppression of MHD Fluctuations Leading to Improved Confinement in a Gun-Driven Spheromak

Dust trajectories and diagnostic applications beyond strongly coupled dusty plasmas

Particle control in the sustained spheromak physics experiment

Contact Info

Product

Resources

About