BaPSF Current Projects

Investigators and Institution	Research Topic
William Heidbrink, Roger McWilliams, Hans Boehmer, Z. Yang Department of Physics, University of California, Irvine. "Study of Ion Transport in Turbulent Plasmas".	A moderate energy ( 1 keV.) Lithium ion beam is mounted in the LAPD. The beam spirals along the background magnetic field in an argon or helium plasma. The beam profile will be measured with probes as it moves through localized turbulent layers. The layers are generated with antennas. The beam divergence and energy spread will be studied.
Craig Kletzing, Fred Skiff, Scott Bounds, Derek Thuecks, J. Martin Heiner. Department of Physics, University of Iowa "Laboratory Investigation of Auroral Alfvén Electron Acceleration".	This is a study of shear Alfven waves with short perpendicular wavelengths as well as investigations of field-aligned acceleration of electrons due to the electric field of the waves. A series of antennas, which are phased arrays, has been developed at the University of Iowa and put on the LAPD. The propagation of waves launched by these antennas is studied and their dispersion mapped. Velocity analyzers will be used to measure the parallel electron distribution function. Electron distribution functions are inferred from whistler wave dispersion relations. The results will be compared with spacecraft measurements made in the Earth's auroral region.
Mark Gilmore, Univ. of New Mexico, Tony Peebles, Neal Crocker, and T.L. Rhodes, UCLA Department of Physics, and School of Engineering. "Search for Long-Range Correlations in Magnetized Plasma Turbulence"	At least three different types of models (self-organized criticality (SOC)-based models, analytical standard turbulence-based models, and gyrokinetic numerical models) have predicted the existence of long-range (temporal and spatial) correlations in magnetically confined plasma turbulence. These long-range correlations are thought to significantly affect the cross-field transport of particles and heat. Radially-extended structures such as avalanches (SOC), streamers (gyrokinetic, analytical standard turbulence), and heat pulses (gyrokinetic), as well as long-time tails in auto- and cross-correlation functions and self-similar temporal scalings have been predicted. The goal of our research is to investigate long-range correlations in the LAPD that may indicate the existence of such structures in the plasma. In addition, we will investigate the possibility of an SOC state, and the effects of sheared flows on long-range correlations. Arrays of probes together with complex dynamical analysis techniques (e.g. Structure Functions and R/S statistics) will be utilized.
Troy Carter, Dept of Physics UCLA	"Study of Plasma Turbulence produced by counter-propagating Alfvén waves" In theories of weak turbulence based on the incompressible MHD model, interactions between counter-propagating shear Alfven wavepackets are responsible for the cascade of energy in wavenumber space. This research will be an experimental investigation of these interactions, studying collisions between antenna launched Alfvén wave in the LAPD. The frequency and wavenumber spectrum of the resulting nonlinear perturbations will be studied, paying particular attention to the rate of energy transfer in wavenumber space and to the importance of non-ideal effects such as compressibility, perpendicular dispersion and wave particle interactions.
Vladimir Manasson, A. Avaikan, A. Brailovski, L. Giubbolini, I. Gordion, M. Felman, V. Khodos, V. Lininov. "Microwave Tomography" Waveband Corp, (Division of Sierra Nevada Corp) Irvine, CA.	A steerable microwave antenna and source at 60 GHz has been developed, along with detectors. This will enable the LAPD to do planar microwave tomography to rapidly determine plasma density profiles. The instrument can be swept over a series of chords throughout the plasma or held at fixed chords for a sequence of plasma discharges and then moved in angle. The detector is now in use at UCLA's Basic Plasma Science Facility.
George Tynan "Transverse Shear Flow and Drift Alfvén waves" University of California, San Diego	Effect of shear flow on Drift Alfvén waves which are spontaneously generated in field aligned density striations. The effect will be studied as a function of plasma beta around the point beta=me/Mion. The study will also include the effect of shear flow on cross field electron heat transport. A fast framing camera (105 frames/s) is used to photograph plasma edge structures in real time.
Paul Kintner, Cornell University Li-Jen Chen, Univ. of New Hampshire "Search for electron solitary structures"	Electron solitary structures (ESS) have been observed by satellites in many very different regions of space. They are negatively charged structures which are several Debye lengths in diameter and travel at a substantial fraction of the electron thermal speed. To see them in a laboratory plasma, arrays of probes of order 10 microns in diameter willl be grown at the UCLA MEMs center in collaboration with Prof. Jack Judy and Franklin Chaing. Probes with 2 GHz amplifiers to enable identification of the fast moving structures have already been built and others with 12 Ghz bandwidth are under construction. Miniature velocity analyzers are also being fabricated The work will be done in collaboration with Walter Gekelman and Pat Pribyl.
W. Horton, J.C. Perez, R.D. Bengtson, University of Texas, Austin "Vorticity Probes and the Characterization of Vorticies in the Kelvin Helmholtz Instability in LAPD"	A 5 channel probe constructed to measure vorticity in the EXB flow of a plasma has been tested. The probe made measurements of vorticity in turbulence induced by biasing the plasma column with respect to the chamber wall. Measurements will be compared with theoretical calculations for the Kevin Helmholtz instability. Work is in collaboration with Troy Carter and Stephen Vincena.
James Chen "Laboratory Investigation of the Dynamics of Magnetic Flux Ropes" Naval Research Laboratory, Washington DC.	A 10 cm diameter oxide coated cathode and anode has been placed below a plasma column. Eventually their separation will be variable as well as their orientation to the background magnetic field. The small cathode and anode will be located inside of small, high current solenoids, which will be pulsed while the cathode is emitting, to create a magnetic arch and a flux rope. The field lines inside the arch is helical. Fast photography shows the development of rising arches, which pinch. Magnetic probes will be used to determine the proper conditions for the flux rope to rise as a Coronal Mass Ejection does. The event is pulsed at 1 Hz. and the The data will be compared with simulations done at NRL. Collaborators will be W. Gekelman and Pat Pribyl and S. Tripathi
Jean Perez, Stanislav Boldyrev University of Wisconsin, Madison	This study addresses the structure of turbulence by attempting to measure the angle between velocity and magnetic field fluctuations. The turbulence will be generated using high power Alfvén waves. The structure scale size and alignment angle will be measured for various probe separations. The experiment results will be compared to theories of turbulent cascade in the solar wind and interstellar medium. The UCLA support group will consist of T. Carter, S. Vincena and W. Gekelman.
Chris Niemann, Carmen Constantin Department of Electrical Engineering, Dept of Physics UCLA "Production of Collisionless Shocks using a High Power Laser and target in the LAPD"	A high power (up to 50J) Nd-Yag laser (repetition rate 10 minutes) is focused on a target in the LAPD plasma. Calculations show the laser energy sufficient to drive collisionless shocks with Alfvén Mach numbers in excess of two down the machine axis of the LAPD. The interaction is studies with the use of multiple magnetic and Mach probes, fast (3 ns) photography and schleirn and shadowgraphy techniques. Work done in collaboration with W. Gekelman, P. Pribyl, S. Vincena, and A. Collette

CURRENT PROJECTS: INTERNATIONAL COLLABORATION

The BaPSF welcomes international collaborations. The travel and housing expenses of the international users must be funded by grants for these purposes, but the use of the facility is free of charge.

Investigators
and Institution

Research Topic

Julio Herrera Velazquez :ICN-UNAM, Mayo Villagran Muniz: (CCADET-UNAM)

"Laser Based Plasma Flows and Jets at the UCLA BaPSF"

ICN-UNAM:Instituto de Ciencias Nuclearees-Universidad Nacional Autonoma de Mexico, CCADET-UNAM: Centro de Ciencias Aplicadas y Desarrollo Technologico, Universidad Nacional Autonoma de Mexico

A laser target experiment is used to generate a high-density localized plasma with the LAPD plasma column. One magnet set on the LAPD was reversed so that the dense expanding plasma will propagate into, or originate inside of a cusp magnetic field. The experimental results will be compared with numerical simulations of astrophysical jets. Collaborators at UCLA are W. Gekelman, G. Morales, J. Maggs, and S. Vincena.

CURRENT PROJECTS: UCLA LOCAL GROUP

The "local group" is the team that constructed the LAPD device and runs it as a user facility. The group consists of: Walter Gekelman, James Maggs, George Morales, Steve Vincena, David Leneman, Shreekrishna Tripathi and Patrick Pribyl.

Title of Topic	Research Topic
"The collision of dense laser produced plasmas in a background magnetoplasma". W. Gekelman, S. Vincena, A. Collette	Twin 150 MW (1.5 Joule), Yag laser, with excellent shot-to-shot reproducibility strike two targets embedded in a background plasma. The targets are arranged so that two dense cross-field plasma jets collide between them. The targets are moved every few shots so a fresh surface is always available. Studies of waves, turbulence just after and long after the collision (Alfvén, whistler, ion acoustic, shocks) are investigated. The interaction gives rise to fully three-dimensional currents in which magnetic field line reconnection sites are identified. Data consists of fast camera photography with ion filters, 3D magnetic field data from probes, flow data and LIF.
Bart Von Compernolle, W. Gekelman, P. Pribyl, George Morales "Interaction of High Power Micowaves at Plasma Resonances"	High power microwaves (100-200kW, 9 GHz, 0.5-2.5 msec) are launched across the background magnetic field and focused at a location where they match either the local plasma or upper hybrid frequency. Intense Alfvén waves are generated by Cherenkov emission of fast electrons. The interaction and its dependence on background field, microwave polarization and microwave power is studied. Measurements include those of the electric and magnetic fields of the waves, fast electrons, and plasma flows
J. Maggs, G. Morales, T. Carter, D. Pace and M. Shi “"Study of heat transport associated with electron temperature gradients"”	This project is a comprehensive study of the transport phenomena resulting from electron temperature gradients created by heating the plasma with a small (about 3 mm diameter) electron beam. The project blends experiments, analytical methods, and computer simulations. Collective instabilities driven by electron temperature gradients can give rise to strongly nonlinear processes that significantly alter the properties of the ambient plasma environment. As a consequence, plasma flows develop that result in density changes and complex spatio-temporal structures. These secondary phenomena generate transport rates whose magnitude and parameter scaling deviate substantially from the classical predictions based on Coulomb interactions between individual charges
D. Leneman, S. Vincena,W. Gekelman, J. Maggs "Study of Large Amplitude Alfvén waves"	A variety of antennas are utilized to produced large amplitude waves with dBwave/B0>> sqrt(b). Here b is the ratio of the magnetic to particle pressure. Density perturbations and ion motion associated with the waves are studied using probes and laser-induced fluorescence. The results are compared to satellite data in connection with auroral processes.
S. Vincena, W. Gekelman, A. Collette, and C. Cooper “"Laser-produced current streamer merging and magnetic reconnection"”	When a solid target is immersed in a large magnetized plasma and struck with a high-power laser, a dense, energetic blob of plasma is created. When the incoming laser is perpendicular to the background magnetic field, the laser-produced plasma (lpp) also propagates cross-field. As it does so, it continually sheds high energy (>60eV, with background Te=6eV) electrons, essentially creating a moving line current in the plasma. When the laser is split and made to create two electron streamers propagating towards each other, the two parallel currents are forced to merge and lead to magnetic field reconnection.
S. Vincena, J. Maggs, W. Gekelman, Eric Lawrence, P. Pribyl "Plasma Rotation and Flows"”	An oxide coated cathode and annular anode are used to create a internal plasma which has an EXB induced flow at its edge. "Slot" exciters will also be pulsed on in the background plasma to create local intense currents, density modifications and local flows. Flows are also generated by inserting a conducting rod along the device axis and biasing it with respect to the chamber wall. The interaction of the flow and plasma waves such as Alfvén or whistler waves will be studied. Nonlinear effects are expected when the Mach number of the flow with respect to ion sound exceeds one.

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