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Ghazaryan S, Kaloyan M, Gekelman W, Lucky Z, Vincena S, Tripathi SKP, Pribyl P, Niemann C. Thomson scattering on the large plasma device. Rev Sci Instrum 2022; 93:083514. [PMID: 36050046 DOI: 10.1063/5.0099172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 07/18/2022] [Indexed: 06/15/2023]
Abstract
We have developed a non-collective Thomson scattering diagnostic for measurements of electron density and temperature on the Large Plasma Device. A triple grating spectrometer with a tunable notch filter is used to discriminate the faint scattering signal from the stray light. In this paper, we describe the diagnostic and its calibration via Raman scattering and present the first measurements performed with the fully commissioned system. Depending on the discharge conditions, the measured densities and temperatures range from 4.0 × 1012 to 2.8 × 1013 cm-3 and from 1.2 to 6.8 eV, respectively. The variation of the measurement error with plasma parameters and discharges averaged is also discussed.
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Affiliation(s)
- S Ghazaryan
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - M Kaloyan
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - W Gekelman
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - Z Lucky
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - S Vincena
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - S K P Tripathi
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - P Pribyl
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - C Niemann
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
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2
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Gekelman W, Tang SW, DeHaas T, Vincena S, Pribyl P, Sydora R. Spiky electric and magnetic field structures in flux rope experiments. Proc Natl Acad Sci U S A 2019; 116:18239-18244. [PMID: 29925603 PMCID: PMC6744923 DOI: 10.1073/pnas.1721343115] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Magnetic flux ropes are structures that are common in the corona of the sun and presumably all stars. They can be thought of as the building blocks of solar structures. They have been observed in Earth's magnetotail and near Mars and Venus. When multiple flux ropes are present magnetic field line reconnection, which converts magnetic energy to other forms, can occur when they collide. The structure of multiple magnetic ropes, the interactions between multiple ropes, and their topological properties such as helicity and writhing have been studied theoretically and in laboratory experiments. Here, we report on spiky potential and magnetic fields associated with the ropes. We show that the potential structures are chaotic for a range of their temporal half-widths and the probability density function (PDF) of their widths resembles the statistical distribution of crumpled paper. The spatial structure of the magnetic spikes is revealed using a correlation counting method. Computer simulation suggests that the potential structures are the nonlinear end result of an instability involving relative drift between ions and electrons.
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Affiliation(s)
- W Gekelman
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095;
| | - S W Tang
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095
| | - T DeHaas
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095
| | - S Vincena
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095
| | - P Pribyl
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095
| | - R Sydora
- Department of Physics, University of Alberta, Edmonton, AB, Canada T6G 2R3
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3
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Gekelman W, Pribyl P, Vincena S, Tang SW, Papadopoulos K. Ferrite based antennae for launching Alfvén waves. Rev Sci Instrum 2019; 90:083505. [PMID: 31472640 DOI: 10.1063/1.5103171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 08/01/2019] [Indexed: 06/10/2023]
Abstract
Whistler and Alfvén waves are known to scatter mirror-trapped electrons and protons into the loss cone of the earth's dipole magnetic field. An array of satellites with properly phased antennas can be used to artificially reduce the flux of energetic particles from regions where their flux has been naturally or artificially pumped. In any space based system, the power required to drive antennas is at a premium. We present here experimental evidence that the efficiency of an antenna can be greatly enhanced with the use of ferrite cores with high relative magnetic permeability μ. Ferrite-based antennas were constructed to launch Alfvén waves in a magnetized plasma. The wave magnetic field of shear Alfvén waves launched with a ferrite core was by the magnetization factor μ larger than that of a similar antenna without a ferrite. Combining multiple ferrite antennas allowed control of the injected perpendicular wavelength. This novel technique can be used to efficiently launch low frequency waves with amplitude above the threshold required for nonlinear triggering.
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Affiliation(s)
- W Gekelman
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - P Pribyl
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - S Vincena
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - S W Tang
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - K Papadopoulos
- Departments of Physics and Astronomy, University of Maryland, College Park, Maryland 20742, USA
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4
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Martin MJ, Gekelman W, Van Compernolle B, Pribyl P, Carter T. Experimental Observation of Convective Cell Formation due to a Fast Wave Antenna in the Large Plasma Device. Phys Rev Lett 2017; 119:205002. [PMID: 29219335 DOI: 10.1103/physrevlett.119.205002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Indexed: 06/07/2023]
Abstract
An experiment in a linear device, the Large Plasma Device, is used to study sheaths caused by an actively powered radio frequency (rf) antenna. The rf antenna used in the experiment consists of a single current strap recessed inside a copper box enclosure without a Faraday screen. A large increase in the plasma potential was observed along magnetic field lines that connect to the antenna limiter. The electric field from the spatial variation of the rectified plasma potential generated E[over →]×B[over →]_{0} flows, often referred to as convective cells. The presence of the flows generated by these potentials is confirmed by Mach probes. The observed convective cell flows are seen to cause the plasma in front of the antenna to flow away and cause a density modification near the antenna edge. These can cause hot spots and damage to the antenna and can result in a decrease in the ion cyclotron range of frequencies antenna coupling.
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Affiliation(s)
- M J Martin
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - W Gekelman
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - B Van Compernolle
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - P Pribyl
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - T Carter
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
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5
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Van Compernolle B, An X, Bortnik J, Thorne RM, Pribyl P, Gekelman W. Erratum: Excitation of Chirping Whistler Waves in a Laboratory Plasma [Phys. Rev. Lett. 114, 245002 (2015)]. Phys Rev Lett 2016; 117:059901. [PMID: 27517795 DOI: 10.1103/physrevlett.117.059901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Indexed: 06/06/2023]
Abstract
This corrects the article DOI: 10.1103/PhysRevLett.114.245002.
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6
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Wang Y, Pribyl P, Gekelman W. A megawatt solid-state modulator for high repetition rate pulse generation. Rev Sci Instrum 2016; 87:023509. [PMID: 26931851 DOI: 10.1063/1.4941678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2015] [Accepted: 01/24/2016] [Indexed: 06/05/2023]
Abstract
A novel solid-state modulator capable of generating rapid consecutive power pulses is constructed to facilitate experiments on plasma interaction with high power microwave pulses. The modulator is designed to output a 100 kHz tone burst, which consists of up to 10 pulses, each with 1 μs duration and 1 MW peak power. The pulses are formed by discharging a total of 480 μF capacitors through 24 synchronized MOSFETs and 6 step-up transformers. The highly modular design, as a replacement of an old single-pulse version used in earlier experiments which employs a pulse forming network, brings great flexibility and wide potential to its application. A systematic cost-effectiveness analysis is also presented.
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Affiliation(s)
- Y Wang
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - P Pribyl
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - W Gekelman
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
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7
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Gekelman W, Pribyl P, Lucky Z, Drandell M, Leneman D, Maggs J, Vincena S, Van Compernolle B, Tripathi SKP, Morales G, Carter TA, Wang Y, DeHaas T. The upgraded Large Plasma Device, a machine for studying frontier basic plasma physics. Rev Sci Instrum 2016; 87:025105. [PMID: 26931889 DOI: 10.1063/1.4941079] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 01/10/2016] [Indexed: 06/05/2023]
Abstract
In 1991 a manuscript describing an instrument for studying magnetized plasmas was published in this journal. The Large Plasma Device (LAPD) was upgraded in 2001 and has become a national user facility for the study of basic plasma physics. The upgrade as well as diagnostics introduced since then has significantly changed the capabilities of the device. All references to the machine still quote the original RSI paper, which at this time is not appropriate. In this work, the properties of the updated LAPD are presented. The strategy of the machine construction, the available diagnostics, the parameters available for experiments, as well as illustrations of several experiments are presented here.
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Affiliation(s)
- W Gekelman
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - P Pribyl
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - Z Lucky
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - M Drandell
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - D Leneman
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - J Maggs
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - S Vincena
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - B Van Compernolle
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - S K P Tripathi
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - G Morales
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - T A Carter
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - Y Wang
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
| | - T DeHaas
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA
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Abstract
The plasma potential, V(p), is a key quantity in experimental plasma physics. Its spatial gradients directly yield the electrostatic field present. Emissive probes operating under space-charge limited emission conditions float close to V(p) even under time-varying conditions. Throughout their long history in plasma physics, they have mostly been constructed with resistively heated tungsten wire filaments. In high density plasmas (>10(12) cm(-3)), hexaboride emitters are required because tungsten filaments cannot be heated to sufficient emission without component failure. A resistively heated emissive probe with a cerium hexaboride, CeB6, emitter has been developed to work in plasma densities up to 10(13) cm(-3). To show functionality, three spatial profiles of V(p) are compared using the emissive probe, a cold floating probe, and a swept probe inside a plasma containing regions with and without current. The swept probe and emissive probe agree well across the profile while the floating cold probe fails in the current carrying region.
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Affiliation(s)
- M J Martin
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - J Bonde
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - W Gekelman
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - P Pribyl
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
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9
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Tripathi SKP, Van Compernolle B, Gekelman W, Pribyl P, Heidbrink W. Excitation of shear Alfvén waves by a spiraling ion beam in a large magnetoplasma. Phys Rev E Stat Nonlin Soft Matter Phys 2015; 91:013109. [PMID: 25679725 DOI: 10.1103/physreve.91.013109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Indexed: 06/04/2023]
Abstract
Generation of shear Alfvén waves by the Doppler-shifted ion-cyclotron-resonance (DICR) of a spiraling H(+) ion beam with magnetic fluctuations in a dual-species magnetized plasma with He(+) and H(+) ions has been investigated on the Large Plasma Device. The ambient plasma density and electron temperature were significantly enhanced by the beam. The Alfvén waves were left-handed polarized and traveled in the direction opposite to the ion beam. This is the first experimental demonstration of the DICR excitation of traveling shear Alfvén waves in a laboratory magnetoplasma.
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Affiliation(s)
- S K P Tripathi
- Physics and Astronomy, University of California at Los Angeles, Los Angeles, California 90095
| | - B Van Compernolle
- Physics and Astronomy, University of California at Los Angeles, Los Angeles, California 90095
| | - W Gekelman
- Physics and Astronomy, University of California at Los Angeles, Los Angeles, California 90095
| | - P Pribyl
- Physics and Astronomy, University of California at Los Angeles, Los Angeles, California 90095
| | - W Heidbrink
- Physics and Astronomy, University of California at Irvine, Irvine, California 92697
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10
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Van Compernolle B, Bortnik J, Pribyl P, Gekelman W, Nakamoto M, Tao X, Thorne RM. Direct detection of resonant electron pitch angle scattering by whistler waves in a laboratory plasma. Phys Rev Lett 2014; 112:145006. [PMID: 24765981 DOI: 10.1103/physrevlett.112.145006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Indexed: 06/03/2023]
Abstract
Resonant interactions between energetic electrons and whistler mode waves are an essential ingredient in the space environment, and in particular in controlling the dynamic variability of Earth's natural radiation belts, which is a topic of extreme interest at the moment. Although the theory describing resonant wave-particle interaction has been present for several decades, it has not been hitherto tested in a controlled laboratory setting. In the present Letter we report on the first laboratory experiment to directly detect resonant pitch angle scattering of energetic (∼keV) electrons due to whistler mode waves. We show that the whistler mode wave deflects energetic electrons at precisely the predicted resonant energy, and that varying both the maximum beam energy, and the wave frequency, alters the energetic electron beam very close to the resonant energy.
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Affiliation(s)
- B Van Compernolle
- Department of Physics, University of California, Los Angeles, California 90095, USA
| | - J Bortnik
- Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California 90095, USA
| | - P Pribyl
- Department of Physics, University of California, Los Angeles, California 90095, USA
| | - W Gekelman
- Department of Physics, University of California, Los Angeles, California 90095, USA
| | - M Nakamoto
- Department of Physics, University of California, Los Angeles, California 90095, USA
| | - X Tao
- Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California 90095, USA
| | - R M Thorne
- Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California 90095, USA
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11
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Wang Y, Gekelman W, Pribyl P. Hard x-ray tomographic studies of the destruction of an energetic electron ring. Rev Sci Instrum 2013; 84:053503. [PMID: 23742547 DOI: 10.1063/1.4804354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A tomography system was designed and built at the Large Plasma Device to measure the spatial distribution of hard x-ray (100 KeV-3 MeV) emissivity. The x-rays were generated when a hot electron ring was significantly disrupted by a shear Alfvén wave. The plasma is pulsed at 1 Hz (1 shot/s). A lead shielded scintillator detector with an acceptance angle defined by a lead pinhole is mounted on a rotary gimbal and used to detect the x-rays. The system measures one chord per plasma shot using only one detector. A data plane usually consists of several hundred chords. A novel Dot by Dot Reconstruction (DDR) method is introduced to calculate the emissivity profile from the line integrated data. In the experiments, there are often physical obstructions, which make measurements at certain angles impossible. The DDR method works well even in this situation. The method was tested with simulated data, and was found to be more effective than previously published methods for the specific geometry of this experiment. The reconstructed x-ray emissivity from experimental data by this method is shown.
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Affiliation(s)
- Y Wang
- Department of Physics and Astronomy, University of California-Los Angeles, Los Angeles, California 90095, USA
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12
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Tripathi SKP, Pribyl P, Gekelman W. Development of a radio-frequency ion beam source for fast-ion studies on the large plasma device. Rev Sci Instrum 2011; 82:093501. [PMID: 21974581 DOI: 10.1063/1.3631628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A helium ion beam source (23 kV/2.0 A) has been constructed for studying fast-ion physics in the cylindrical magnetized plasma of the large plasma device (LAPD). An inductive RF source produces a 10(19) m(-3) density plasma in a ceramic dome. A multi-aperture, rectangular (8 cm × 8 cm) three-grid system extracts the ion beam from the RF plasma. The ion beam is injected at a variety of pitch angles with Alfvénic speeds in the LAPD. The beam current is intense enough to excite magnetic perturbations in the ambient plasma. Measurements of the ion beam profile were made to achieve an optimum beam performance and a reliable source operation was demonstrated on the LAPD.
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Affiliation(s)
- S K P Tripathi
- Physics and Astronomy, University of California at Los Angeles, Los Angeles, California 90095, USA
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13
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Abstract
A new 18x18 cm(2) active area lanthanum hexaboride (LaB(6)) plasma source for use in a dc discharge has been developed at UCLA. The cathode consists of four tiled LaB(6) pieces indirectly heated to electron emission (1750 degrees C) by a graphite heater. A molybdenum mesh anode 33 cm in front of the LaB(6) accelerates the electrons, ionizing a fill gas to create a 20x20 cm(2) nearly square plasma. The source is run in pulsed operation with the anode biased up to +400 V dc with respect to the cathode for up to 100 ms at a 1 Hz repetition rate. Both the cathode and anode "float" electrically with respect to the chamber walls. The source is placed in a toroidal chamber 2 m wide and 3 m tall with a major radius of 5 m. Toroidal and vertical magnetic fields confine the current-free plasma which follows the field in a helix. The plasma starts on the bottom of the machine and spirals around it up to four times (120 m) and can be configured to terminate either on the top wall or on the neutral gas itself. The source typically operates with a discharge current up to 250 A in helium making plasmas with T(e)<30 eV, T(i)<16 eV, and n(e)<3x10(13) cm(-3) in a background field of 100 G<B(o)<320 G, giving a magnetized plasma with 0.1<beta<1.
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Affiliation(s)
- C M Cooper
- University of California, Los Angeles, California 90095, USA
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14
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Everson ET, Pribyl P, Constantin CG, Zylstra A, Schaeffer D, Kugland NL, Niemann C. Design, construction, and calibration of a three-axis, high-frequency magnetic probe (B-dot probe) as a diagnostic for exploding plasmas. Rev Sci Instrum 2009; 80:113505. [PMID: 19947729 DOI: 10.1063/1.3246785] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A three-axis, 2.5 mm overall diameter differential magnetic probe (also known as B-dot probe) is discussed in detail from its design and construction to its calibration and use as diagnostic of fast transient effects in exploding plasmas. A design and construction method is presented as a means to reduce stray pickup, eliminate electrostatic pickup, reduce physical size, and increase magnetic signals while maintaining a high bandwidth. The probe's frequency response is measured in detail from 10 kHz to 50 MHz using the presented calibration method and compared to theory. The effect of the probe's self-induction as a first order correction in frequency, O(omega), on experimental signals and magnetic field calculations is discussed. The probe's viability as a diagnostic is demonstrated by measuring the magnetic field compression and diamagnetism of a sub-Alfvenic (approximately 500 km/s, M(A) approximately 0.36) flow created from the explosion of a high-density energetic laser plasma through a cooler, low-density, magnetized ambient plasma.
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Affiliation(s)
- E T Everson
- Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095, USA.
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15
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Gekelman W, Barnes M, Vincena S, Pribyl P. Correlation analysis of waves above a capacitive plasma applicator. Phys Rev Lett 2009; 103:045003. [PMID: 19659363 DOI: 10.1103/physrevlett.103.045003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Indexed: 05/28/2023]
Abstract
Capacitively coupled plasma glow discharges have been extensively used for materials processing in numerous industrial applications. Considerable research has been performed on plasma sheaths and standing waves over a capacitive applicator, which typically holds the processed substrate (e.g., a semiconductor wafer). In this work, we demonstrate for the first time the existence of normal modes in electric potential analogous to the vibrational modes in circular membranes and plates. These modes are exhibited through cross spectral analysis of the plasma potential measured with an emissive probe at 208 spatial positions and sampled at 1 GHz. These modes exist at several frequencies and are described by a series of Bessel functions. The data further suggests a nonlinear interaction between modes of different frequencies.
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Affiliation(s)
- W Gekelman
- Department of Physics and Astronomy, University of California, Los Angeles, California, USA
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16
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Cepák V, Pribyl P, Kvíderová J, Lukavský J. Comparative study of zooid and non-zooid forming strains of Scenedesmus obliquus. Physiology and cytomorphology. Folia Microbiol (Praha) 2006; 51:349-56. [PMID: 17007441 DOI: 10.1007/bf02931829] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two zooid forming strains and four non-zooid strains of the green chlorococcal alga Scenedesmus obliquus were compared in terms of growth, morphological and physiological characteristics. Large differences were observed among the strains grown under various growth conditions (light and temperature). The assumption that the zooid forming strains may be similar was not confirmed. Since they considerably differed in daughter cells morphology, photosynthesis, growth rate in batch culture or commitment to cellular division. Molecular-genetic comparison of 18S RNA/DNA might distinguish zooid forming strains from non-zooid ones.
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Affiliation(s)
- V Cepák
- Center of Phycology, Institute of Botany, Academy of Sciences of the Czech Republic, Trebon, Czechia.
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17
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Cepák V, Pribyl P, Vítová M. The effect of light color on the nucleocytoplasmic and chloroplast cycle of the green chlorococcal alga Scenedesmus obliquus. Folia Microbiol (Praha) 2006; 51:342-8. [PMID: 17007440 DOI: 10.1007/bf02931828] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The color of light (white, red, blue, and green) had a significant effect on the growth and reproductive processes (both in the nucleocytoplasmic and chloroplast compartment of the cells) in synchronous cultures of Scenedesmus obliquus. This effect decreased in the order red > white > blue > green. In the same order, the light phase of the cell cycle (time when first autospores started to be released) was prolonged. The length of dark phase (time when 100 % of daughters were allowed to release from mothers) was not influenced and was the same for all colors. Critical cell size for cell division in green light was shifted to a smaller size (compared with cells grown in other lights) and so was the size of released daughters. The nuclear cycle was slowed in blue and even in green light, contrary to cells grown in red and white light. At the beginning of the cell cycle, one-nucleus daughters possess approximately 10 nucleoids; during the cell cycle their number doubled in all variants before the division of nuclei. Both events were delayed in cultures grown more slowly most markedly in green light. Smaller daughters in the green variant possessed a lower number of nucleoids. Motile cells released in continuous green or blue lights but not in red one were rarely observed.
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Affiliation(s)
- V Cepák
- Center of Phycology, Institute of Botany, Academy of Sciences of the Czech Republic, Trebon, Czechia.
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Carter TA, Brugman B, Pribyl P, Lybarger W. Laboratory observation of a nonlinear interaction between shear Alfvén waves. Phys Rev Lett 2006; 96:155001. [PMID: 16712166 DOI: 10.1103/physrevlett.96.155001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Indexed: 05/09/2023]
Abstract
An experimental investigation of nonlinear interactions between shear Alfvén waves in a laboratory plasma is presented. Two Alfvén waves, generated by a resonant cavity, are observed to beat together, driving a pseudomode at the beat frequency. The pseudomode then scatters the Alfvén waves, generating a series of sidebands. The observed interaction is very strong, with the normalized amplitude of the driven pseudomode comparable to the normalized magnetic field amplitude (deltaB/B) of the interacting Alfvén waves.
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Affiliation(s)
- T A Carter
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547, USA.
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Pribyl P, Cepák V, Zachleder V. Cytoskeletal alterations in interphase cells of the green alga Spirogyra decimina in response to heavy metals exposure: I. The effect of cadmium. Protoplasma 2005; 226:231-40. [PMID: 16333580 DOI: 10.1007/s00709-005-0123-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2004] [Accepted: 05/09/2005] [Indexed: 05/05/2023]
Abstract
The aim of the study was to elucidate the effect of cadmium ions on the arrangement of the actin and tubulin cytoskeleton, as well as the relationships between cytoskeletal changes and growth processes in the green filamentous alga Spirogyra decimina. Batch cultures of algae were carried out under defined conditions in the presence of various cadmium concentrations. In control cells, the cytoskeleton appeared to be a transversely oriented pattern of both microtubules and actin filaments of various thickness in the cell cortex; colocalization of cortical microtubules and actin filaments was apparent. Microtubules were very sensitive to the presence of cadmium ions. Depending on the cadmium concentration and the time of exposure, microtubules disintegrated into short rod-shaped fragments or they completely disappeared. A steep increase in cell width and a decrease in growth rate accompanied (and probably ensued) a very rapid disintegration of microtubules. Actin filaments were more stable because they were disturbed several hours later than microtubules at any cadmium concentration used. When cadmium ions were washed out, the actin cytoskeleton was rebuilt even in cells in which actin filaments were completely disintegrated at higher cadmium concentrations (40 or 100 microM). The much more sensitive microtubules were regenerated after treatment with lower cadmium concentrations (10 or 15 microM) only.
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Affiliation(s)
- P Pribyl
- Centre of Phycology, Institute of Botany, Academy of Sciences of the Czech Republic, Dukelská 135, 379 82 Trebon, Czech Republic
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Fiksel G, Prager SC, Pribyl P, Taylor RJ, Tynan GR. Measurement of magnetic fluctuation induced energy transport in a tokamak. Phys Rev Lett 1995; 75:3866-3869. [PMID: 10059751 DOI: 10.1103/physrevlett.75.3866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Taylor RJ, Brown ML, Fried BD, Grote H, Liberati JR, Morales GJ, Pribyl P, Darrow D, Ono M. H-mode behavior induced by cross-field currents in a tokamak. Phys Rev Lett 1989; 63:2365-2368. [PMID: 10040870 DOI: 10.1103/physrevlett.63.2365] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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