Energy Efficiency Analysis of the Discharge Circuit of Caltech Spheromak Experiment

2010

Physics of Plasmas

Collimated magnetized plasma structures are commonly observed on galactic, stellar, and laboratory scales. The Caltech plasma gun produces magnetically driven plasma jets bearing a striking resemblance to astrophysical jets and solar coronal loops by imposing boundary conditions analogous to those plasmas. This paper presents experimental observations of gun-produced plasma jets that support a previously proposed magnetohydrodynamic ͑MHD͒ pumping model ͓P. M. Bellan, Phys. Plasmas 10, 1999 ͑2003͔͒ as a universal collimation mechanism. For any initially flared, magnetized plasma tube with a finite axial current, the model predicts ͑i͒ magnetic pumping of plasma particles from a constricted region into a bulged region and ͑ii͒ tube collimation if the flow slows down at the bulged region leading to accumulation of mass and thus concentrating the azimuthal magnetic flux frozen in the mass flow ͑i.e., increasing the pinch force͒. Time-and space-resolved spectroscopic measurements of gun-produced plasmas have confirmed the highly dynamic nature of the process leading to a collimated state, namely, ͑i͒ suprathermal Alfvénic flow ͑30-50 km/s͒, ͑ii͒ large density amplification from ϳ10 17 to ϳ10 22 m −3 in an Alfvénic time scale ͑5-10 s͒, and ͑iii͒ flow slowing down and mass accumulation at the flow front, the place where the tube collimation occurs according to high-speed camera imaging. These observations are consistent with the predictions of the MHD pumping model, and offer valuable insight into the formation mechanism of laboratory, solar, and astrophysical plasma structures.

Section: Methodsmentioning

confidence: 99%

Plasma tubes becoming collimated as a result of magnetohydrodynamic pumping

Yun

2010

Physics of Plasmas

“…All shots had the same vacuum magnetic field and the same 4.0 kV capacitor charge. Because the capacitor acts as a current source [23], plasma currents are the same to within 10%, even for different species.…”

Section: Prl 109 075001 (2012) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Magnetically Driven Flows in Arched Plasma Structures

Stenson

2012

Phys. Rev. Lett.

Laboratory experiments demonstrate high-speed plasma flows from both footpoints of arched magnetic flux tubes, resulting in bulk plasma transport into the flux tube and persistent axial collimation even as the flux tube lengthens and kinks. The measured flows are in agreement with the predictions of hoop force and collimation models involving fundamental MHD forces. These forces are expected to drive plasma acceleration in other open flux configurations with arched geometries, such as those found on the solar surface.

“…Details of the plasma gun and its sequence of operation can be found elsewhere. 2,16,17 In the present experiment, the peak discharge voltage was set to 5 kV and peak current was 110 kA. Nitrogen was used as the working gas.…”

Section: B Caltech Coaxial Magnetized Plasma Gun Experimentsmentioning

confidence: 99%

Development of a polarization resolved spectroscopic diagnostic for measurements of the vector magnetic field in the Caltech coaxial magnetized plasma jet experiment

Shikama

Review of Scientific Instruments

2013

Characterization of nanosecond pulse driven dielectric barrier discharge plasma actuators for aerodynamic flow control J. Appl. Phys. 113, 103302 (2013) Electrode-plasma-driven radiation cutoff in long-pulse, high-power microwave devices Phys. Plasmas 20, 034501 (2013) Measuring time of flight of fusion products in an inertial electrostatic confinement fusion device for spatial profiling of fusion reactions Rev. Sci. Instrum. 84, 033501 (2013) A gas-jet transport and catcher technique for on-line production of radioactive ion beams using an electron cyclotron resonance ion-source Rev. Sci. Instrum. 84, 033301 (2013) Time-lag properties of corona streamer discharges between impulse sphere and dc needle electrodes under atmospheric air conditions Rev. Sci. Instrum. 84, 024702 (2013) Additional information on Rev. Sci. Instrum. In the Caltech coaxial magnetized plasma jet experiment, fundamental studies are carried out relevant to spheromak formation, astrophysical jet formation/propagation, solar coronal physics, and the general behavior of twisted magnetic flux tubes that intercept a boundary. In order to measure the spatial profile of the magnetic field vector for understanding the underlying physics governing the dynamical behavior, a non-perturbing visible emission spectroscopic method is implemented to observe the Zeeman splitting in emission spectra. We have designed and constructed a polarization-resolving optical system that can simultaneously detect the left-and right-circularly polarized emission. The system is applied to singly ionized nitrogen spectral lines. The magnetic field strength is measured with a precision of about ±13 mT. The radial profiles of the azimuthal and axial vector magnetic field components are resolved by using an inversion method.