Scheduled System Maintenance:
On Monday, April 27th, IEEE Xplore will undergo scheduled maintenance from 1:00 PM - 3:00 PM ET (17:00 - 19:00 UTC). No interruption in service is anticipated.
By Topic

Plasma Science, IEEE Transactions on

Issue 3 • Date June 1996

Filter Results

Displaying Results 1 - 25 of 77
  • A tribute to George Bekefi (1925-1995)

    Publication Year: 1996
    Save to Project icon | Request Permissions | PDF file iconPDF (192 KB)  
    Freely Available from IEEE
  • A model of injection-locked relativistic klystron oscillator

    Publication Year: 1996 , Page(s): 935 - 937
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    By the use of a simple model, we explicitly incorporate the coupling between the driver cavity and the booster cavity in a relativistic klystron amplifier (RKA). We show that this RKA configuration may turn into an injection-locked oscillator only when the beam current is sufficiently high. Other features revealed by this model include: the downshifted frequency mode (“0” mode) is unstable whereas the upshifted frequency mode (“π” mode) is stable; the growth rate of the “0” mode is relatively mild so that the oscillation can start only in an injection-locked mode; the oscillation does not require the presence of reflected electrons; and the separation of the cavities must be sufficiently short. These, and other features, are found to be in qualitative agreement with the recent experiments on the injection-locked relativistic klystron oscillator (RKO) that were conducted at Phillips Laboratory View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effects of tapering on gyrotron backward-wave oscillators

    Publication Year: 1996 , Page(s): 636 - 647
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1164 KB)  

    Computer modeling has been utilized to guide gyrotron backward-wave oscillator (gyro-BWO) experiments at the University of Michigan over a wide range of tapered interaction regions and tapered magnetic fields. E-GUN code is used to examine beam and diode characteristics, while MAGIC is used to analyze the dynamics of the problem, such as particle kinematics and microwave power production. Several innovative techniques are used to create matching boundary conditions for a backward propagating wave. MAGIC simulations predict optimum performance of the gyro-BWO operating in a TE01 mode within a combination of uniform interaction region and a tapered axial magnetic field which increases 7.5% in the direction of beam propagation. Experiments have been performed to investigate the effects of tapering magnetic fields and tapered interaction region radii on the high-power microwave emission from the gyro-BWO over the frequency range from 4.0 to 6.0 GHz. These experiments were performed on the Michigan Electron Long-Pulse Accelerator (MELBA) with parameters: V=-0.7 to -0.9 MV, Idiode=1-10 kA, Itube=1-4 kA, Te-beam =0.4-1.0 μs. Tapered interaction regions of 37%, 23%, 9.4%, and 6.4% were built and tested to determine their effect on microwave power, pulselength, and inferred energy compared to the uniform interaction region. Magnetic tapering trim coils with a range of -10.6%<ΔB/B0<+15.0% were constructed which allow the orientation of the field taper to be changed without breaking the vacuum. The peak microwave power from individual shots was from 30 to 55 MW. Experiments on magnetic field tapering indicate that positive tapered fields improve microwave power and energy output View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mode selective properties of coaxial gyrotron resonators

    Publication Year: 1996 , Page(s): 596 - 605
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (992 KB)  

    In this paper, the mode-selective properties of coaxial gyrotron resonators are discussed for different cavity configurations. Expressions are derived for the ohmic loading of a coaxial conductor with longitudinal corrugations where the RF field inside the corrugations is fully taken into account, and for the diffractive quality factor in coaxial cavities with tapered inner conductor relative to that of an empty cylindrical cavity. The competing action of a kind of “surface mode” that appears in corrugated structures is investigated by considering its diffractive and ohmic quality factors. Additional mode competition problems that can arise in coaxial cavities with corrugated inner conductor due to second cyclotron harmonic interaction are investigated and solutions to the problem are proposed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Study of high-power Ka-band second-harmonic gyroklystron amplifier

    Publication Year: 1996 , Page(s): 666 - 670
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    The self-consistent nonlinear theory of two-cavity high-harmonic gyroklystron amplifier has been developed. The efficiency and gain of a second-harmonic gyroklystron were calculated numerically. The results obtained were used to choose the optimal parameters of the experimental second-harmonic tube. The experimental study was carried out to test high-harmonic amplifier concept. Two-cavity 35 GHz second harmonic gyroklystron with the TE021 cavity mode has been designed and tested in pulse operation. Output power of about 260 kW with efficiency 18% and 17 dB gain have been produced at 72 kV beam voltage and 20 A beam current. Bandwidth of about 0.1% has been observed. The restriction of the output power, efficiency, and gain was caused by spurious oscillations excited in the second cavity in the TE011 mode at the fundamental cyclotron frequency View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical simulation of nonstationary processes in intense helical electron beams of gyrotrons

    Publication Year: 1996 , Page(s): 992 - 998
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    Experiments with helical electron beams (HEB) of powerful gyrotrons displayed the existence of intense nonstationary processes in HEB. A version of numerical simulation of HEB's is proposed, which is based on the method of large particles. Some results of the analysis are given with account of the electrons reflected from the magnetic mirror and locked in the adiabatic trap. One of the effects detected is intense bombardment of the cathode by the trapped electrons. Besides, formation of quasi-stationary states whose parameters (velocity spread, pitch-factor) differ significantly from those given by the static theory was observed. In the absence of the reflected particles, the solution acquires a stable state. The HEB parameters in this case are almost the same as the static parameters View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Prototype microwave source for a relativistic klystron two-beam accelerator

    Publication Year: 1996 , Page(s): 938 - 946
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (980 KB)  

    A test facility is established at Lawrence Berkeley National Laboratory (LBNL) to study RF power sources for linear colliders based on the relativistic klystron two-beam accelerator (RK-TBA) concept. A 24-m long prototype source, the RTA, will be constructed in this facility to study physics, engineering, and cost issues related to RK-TBAs. The RTA will generate 200-ns 180-MW RF (11.4-GHz) pulses from each of eight output ports. The major components of the RTA include a 2.8-MeV 1.2-kA induction injector, transverse beam modulator, adiabatic compressor, and RF extraction section. The beam energy is increased to 4 MeV and the RF bunch length is shortened from 240° to 110° in the adiabatic compressor. The 8-m long extraction section includes 40 induction accelerator cells to maintain beam energy at an average 4 MeV, eight equally spaced RF output structures, and a ppm quadrupole focusing system. In this paper, we describe the RTA and present results of component testing and computer simulations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Linearized field theory of a dielectric-loaded helix traveling wave tube amplifier

    Publication Year: 1996 , Page(s): 895 - 904
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    A linearized relativistic field theory of a helix traveling wave tube (TWT) is presented for a configuration where either a thin annular beam or a solid beam propagates through a sheath helix enclosed within a loss-free wall in which the gap between the helix and the outer wall is filled with a dielectric. A linear analysis of the interaction is solved subject to the boundary conditions imposed by the beam, helix, and wall. In the case of the annular beam, the electrons are assumed to be strongly magnetized. In contrast, the effect of variations in the axial magnetic field are included in the electron dynamics for the solid beam analysis. Determinantal dispersion equations are obtained for the azimuthally symmetric modes which implicitly includes beam space-charge effects without recourse to a heuristic model of the space-charge field. Numerical solutions of the dispersion equations are discussed and compared with experiments View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Slotted third-harmonic gyro-TWT amplifier experiment

    Publication Year: 1996 , Page(s): 727 - 734
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    The first operation of a slotted third-harmonic gyrotron traveling-wave amplifier is reported. The low-magnetic-field moderate-voltage gyrotron amplifier's 62-keV 2.5-A υ||=1.2 axis-encircling electron beam was supplied by a gyroresonant RF accelerator. The 10-GHz 1.3-kG single-section slotted third-harmonic amplifier is stable and yielded 12.5 dB of small signal gain with a bandwidth of 2.5%. The experiment was performed as a scaled proof-of-principle test of the 95-GHz multisection slotted amplifier under development at CPI (formerly Varian) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhanced frequency agility of high-power relativistic backward wave oscillators

    Publication Year: 1996 , Page(s): 852 - 858
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    This paper describes how finite length effects in high-power backward wave oscillators can be exploited in a controlled manner to achieve enhanced frequency agility. Experiments were performed using a Sinus-6 high-power relativistic repetitively pulsed electron beam accelerator. A uniform slow wave structure was used in these studies and its parameters were fixed. Sections of smooth-walled circular waveguide of varying lengths were inserted both before and after the slow wave structure. Variations in the length of smooth-walled waveguide on the order of a quarter-wavelength of the generated electromagnetic radiation were found to significantly affect both microwave frequency and radiation efficiency in a periodic-like manner. The experimental results were reproduced in TWOQUICK electromagnetic particle-in-cell simulations. A bandwidth of about 500 MHz centered around 9.5 GHz at hundreds of MW power levels has been achieved with constant beam and slow wave structure parameters View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Breakdown of magnetic insulation in semiconductor plasmas

    Publication Year: 1996 , Page(s): 1095 - 1100
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    A theoretical analysis of the current response of strongly magnetized electrically biased photoconductors to short laser pulses, with emphasis on the breakdown of magnetic insulation, is presented. There are two regimes that result in breaking of the magnetic insulation during the “on” time of the pulse: (1) the collisionless regime, applicable to pulses with duration τ0<1/ν, where ν is the collision frequency, in which the magnetic insulation is broken by a polarization-like current induced by the fast rate of increase of the carriers, and (2) the collisional regime, applicable to pulses with τ0>1/ν, where the magnetic insulation is broken at high carrier density due to the nonlinear dependence of the collision frequency on the carrier density. A simple experiment was performed which confirms the physics of the collisional regime. It is shown that the presence of the magnetic field can significantly reduce the response time of photoconductors. Response times shorter than a picosecond can be achieved in the collisionless regime View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Gyro-amplifiers as candidate RF drivers for TeV linear colliders

    Publication Year: 1996 , Page(s): 648 - 665
    Cited by:  Papers (44)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2016 KB)  

    The feasibility of future electron-positron colliders operating at energies >1 TeV will depend on both operating efficiency and cost of the microwave amplifiers that can be developed to drive the collider. To zeroth order, the required number of amplifiers depends inversely on the parameter A=PpTp2, where λ is the wavelength, and Pp and Tp are, respectively, the power and duration of the amplifier output pulses. Thus, one goal of amplifier research is to maximize A while keeping other parameter values within bounds so as not to excessively increase the cost of either the individual amplifier system or the collider structure (e.g., amplifier voltage V≲500 kV, wavelength λ≳1 cm). Operating within these bounds, gyro-amplifiers have demonstrated values of A=11×104 W s/m2, which compares favorably with the best values of A achieved by klystrons. The gyro-amplifier program which led to this accomplishment is reviewed. Some 20 different gyro-amplifier configurations have been examined on our 450 kV gyro-amplifier test facility during the past several years. These tubes fall into five major categories: first-, second-, and third-harmonic gyroklystrons, as well as first- and second-harmonic gyrotwystrons. Peak powers in excess of 30 MW with pulse duration of 0.8 μs have been achieved at 19.76 GHz in the TE02 mode via a two-cavity second-harmonic gyroklystron with a first-harmonic drive cavity. The peak efficiency and gain were 28% and 27 dB, respectively. At present, there is ongoing construction of a new three-cavity second-harmonic coaxial gyroklystron, driven by a 500-kV 720-A beam, which is predicted to have an output power well above 100 MW at 17.136 GHz with an intrinsic efficiency in excess of 40%. With the use of a depressed collector, achievable overall amplifier efficiency, which is of very great importance in the collider application, could be in the range of 50-65% View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Cyclotron resonance maser experiment in a nondispersive waveguide

    Publication Year: 1996 , Page(s): 816 - 824
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (780 KB)  

    A cyclotron-resonance maser (CRM) oscillator experiment in which a spiraling electron beam interacts with a transverse electromagnetic wave in a nondispersive waveguide is presented. The experiment employs a low-energy (<5 keV) low-current (<1 A) electron beam in a two-wire (Lecher type) waveguide. The microwave output frequency is tuned in this experiment by the axial magnetic field in the range 3.5-6.0 GHz. A second harmonic emission is observed at ~7 GHz. CRM theory shows that in a free-space TEM-mode interaction, the gain might be canceled due to the equal and opposite effects of the axial (Weibel) and the azimuthal bunching mechanisms. This balance is violated in the large transverse velocity regime (V≫Vz) in which our experiment operates. The tunability measurements of the CRM oscillator experiment in the nondispersive waveguide are discussed in view of the CRM theory View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • PIC code simulation of pulsed radiation in a tapered closed-cavity gyrotron

    Publication Year: 1996 , Page(s): 606 - 612
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    MAGIC, a two-and-one-half-dimensional particle-in-cell (PIC) code, has been used to investigate mode locking in closed-cavity gyrotrons. A cavity, with equally spaced modal frequencies, composed of a radially tapered section and a straight section of waveguide, is designed, built, and cold-tested. Experimental cold test results agree well with the MAGIC PIC code simulations. Using a sinusoidal current density modulation with an amplitude of 5% of the dc current and frequency of 280 MHz, the simulation results show radiation output in a train of narrow pulses (full width at half maximum ~1 us) at a 280 MHz repetition rate. Though the gyrotron does not appear to be mode locked, uniform pulse trains of 30-50 pulses can be obtained View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Operation and optimization of gated field emission arrays in inductive output amplifiers

    Publication Year: 1996 , Page(s): 970 - 981
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1248 KB)  

    In an inductive output amplifier, an emission-gated electron beam induces high-frequency fields in an output circuit via displacement current, not convection current. Emission-gated electron beams experience strong interactions when traversing a resonant or synchronous electromagnetic field, and this strong interaction is responsible for both the interesting nonlinear physics and the attractive efficiency and compactness of emission-gated amplifiers. Field emission cathodes, due to their extremely low electron transit time and high transconductance, offer the opportunity to extend the advantages of emission gating into C and X band. This paper presents design criteria for the joint optimization of the field emission array (FEA) structure and the RF input and output circuits of inductive output amplifiers. We find that while output circuits yielding net efficiencies of 50% or greater are well within the state of the art, the gain is likely to be moderate (10-20 dB). With today's FEA performance, a desirable operating regime is achievable, yielding a new class of compact, highly efficient, and moderate gain power booster amplifiers View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the design of electron guns for cyclotron resonance masers utilizing trochoidal electron beams (trochotrons)

    Publication Year: 1996 , Page(s): 999 - 1004
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    The properties of crossed-field electron guns which are capable of providing the required trochoidal beams for efficient cyclotron resonance interaction in the trochotron configuration are analyzed. A discussion of the beam parameters that are used to characterize the device performance is included in a general description of the operation of these guns. Two concrete designs are presented and are used to demonstrate the performance capabilities of these devices with respect to the beam self-fields, the externally applied electric and magnetic fields, and the electrode geometry. It is shown that these devices, which typically generate beams with large ratios of perpendicular to parallel (drift) velocity, are capable of producing extremely small drift velocity spreads over a wide range of parameters View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Long-pulse operation of a 0.5 MW TE10.4 gyrotron at 140 GHz

    Publication Year: 1996 , Page(s): 570 - 578
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (924 KB)  

    The operation features of a TE10.4-mode gyrotron oscillator with a quasi-optical mode converter and a single-stage depressed collector at 140 GHz with an output power of 500 kW in long pulses of 0.2 s are presented. Measurements on long-pulse operation of the tube are described in detail, and the significant differences between short- and long-pulse operation concerning efficiency and output power are pointed out. The variation of frequency during a pulse and an irreversible frequency shift during long-pulse operation were measured and are discussed with respect to gyrotron design View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Radial penetration and toroidal spread of laser blow-off aluminum beam in TEXTOR

    Publication Year: 1996 , Page(s): 1120 - 1124
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    The toroidal dispersal of laser blow-off injected aluminum is studied. The spatial distribution of Al I, Al II, and Al III line radiation is measured as a function of time. The measured toroidal distribution of the aluminum ions is compared with the distribution calculated by a one-dimensional transport simulation based on the kinetic theory, and a satisfactory agreement is found showing that the toroidal spread is determined only by Coulomb collisions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical simulation of high-power virtual-cathode reflex triode driven by repetitive short pulse electron gun

    Publication Year: 1996 , Page(s): 1015 - 1022
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    A virtual-cathode reflex triode is investigated by numerical simulations. A trapezoidal in shape voltage pulse with an amplitude of 300 kV is applied to the solid cathode of the device to drive the cathode negative. The electron beam-to-microwave power conversion efficiency ε, calculated for the pulse flat top with a duration τft=1.2 ns is approximately the same (about 1.5-2%) as well as for a long flat top (τft=4 ns). The simulations show a 10-15% increase of ε at τft shortening to 0.6 ns. However, this occurs when the anode mesh transparency is high (80-90%). Considerable enhancement of the efficiency (about four times) for τft=0.6 ns has been calculated if the cathode side surface is brought near to the anode tube (from ≈0.5% at cathode radius Rc=1.6 cm to ≈2% at Rc=3.8 cm). The obtained results would find an application for the design of virtual-cathode reflex triode devices driven by a short pulse and high repetition rate electron gun View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electromagnetic properties of corrugated and smooth waveguides filled with radially inhomogeneous plasma

    Publication Year: 1996 , Page(s): 905 - 917
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1268 KB)  

    Creation and diagnosis of plasma in microwave devices remains one of the primary challenges of plasma microwave electronics. In the present work we deal with (1) diagnostic techniques for characterization of radially nonuniform plasma columns suitable for use in high-power microwave sources and (2) the effects of such plasmas on the electromagnetic properties of finite length, spatially periodic slow wave structures. Experimental studies were performed both for a strong and a weak guiding magnetic field. Using a combination of a microwave resonator (X-band) and a Langmuir probe, both the plasma peak density and its transverse profile were measured in situ (prior to beam propagation). The frequency upshifts of the TM01n modes in an open corrugated cavity were measured as a function of the background plasma density. The dispersion diagrams were reconstructed, for the first time, up to a peak plasma density of 1012 cm-3 . Frequency upshifts and “flattening” of the dispersion curves were observed for both strong and weak guiding magnetic fields. For plasma density above 5×1011 cm-3 the frequency upshifts are less than anticipated by theory View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Single-stage depressed collectors for gyrotrons

    Publication Year: 1996 , Page(s): 579 - 585
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    Two 140 GHz gyrotrons with a single-step depressed collector have been operated. The different position of the isolating collector gap in the stray magnetic field causes the electron motion in the retarding region to be in one case adiabatic and in the other case nonadiabatic. The kind of motion within the retarding field influences strongly the behavior of the gyrotron with a depressed collector. In the case of nonadiabatic motion a significant amount of transverse momentum is given to the electrons reflected at the collector potential. This causes the reflected electrons to be trapped between the magnetic mirror and the collector. The electrons escape from the trap by diffusion across the magnetic field to the body of the tube thus contributing to the body current. Despite the high body current there is no observable influence of the collector voltage on the RF output power. In the case of adiabatic motion the reflected electrons do not gain a sufficient amount of transverse momentum to be trapped by the magnetic mirror. They pass the cavity toward the gun and they are trapped between the negative gun potential and the collector. The interaction with the RF field by electrons traveling through the cavity enhances the diffusion in the velocity space thus enabling the trapped electrons to overcome the potential barrier and escape toward the collector. Therefore the body current stays at low values since in this case the reflected electrons do not contribute to it. However, at higher collector voltages a reduction of RF power occurred and some noise in the electron beam was observed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Theory of gyro-backward wave oscillators with tapered magnetic field and waveguide cross section

    Publication Year: 1996 , Page(s): 620 - 629
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (804 KB)  

    A theory is developed which describes gyro-backward wave oscillators (gyro-BWO's) with arbitrarily relativistic electron beams and tapered external magnetic field and waveguide wall radius. For the case of linear tapering the optimal parameters are found that correspond to highly efficient operation. The frequency tunability as the function of magnetic field and voltage deviations has been analyzed. It is shown how to use the results given in terms of normalized parameters for designing concrete gyro-BWO's. For one concrete design the effect of electron velocity spread on the efficiency has been studied View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time delay in laser-guided discharge at low air pressure

    Publication Year: 1996 , Page(s): 1137 - 1146
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1624 KB)  

    Under the air pressure of 1-103 Pa, discharge traces between needle electrode and plane electrode are found to be controlled successfully by using laser beam irradiation. In the controlling process, metal plasma issued by laser irradiation onto the plane electrode and electron avalanche initiated by the metal plasma seem to play an important role in guiding discharge traces with a certain designated shape. Based on the results of guiding discharge traces, feasibility of a new electric discharge machining with laser beam guidance is studied. Behavior of the guiding property is strongly influenced by several factors such as electrode voltage and ambient air pressure. Since it is found that the time delay between the laser irradiation and the start of the discharge is the key factor to understanding the mechanism of the effective guidance, this time delay has been carefully observed by using a high-speed camera. High-speed photographs taken by the camera are analyzed by comparing them with the discharge current profiles observed at the same time. The results obtained in this study are as follows: (1) there are two different triggering mechanisms, which have significant influence on the threshold of guided and unguided discharges; (2) unguided cases appear above a certain delay time depending on the discharge mechanism; and (3) guided cases are essentially influenced by the number density of the air molecules around the electrodes and the thermal pinch effect caused by those molecules View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design of a 3-MW 140-GHz gyrotron with a coaxial cavity

    Publication Year: 1996 , Page(s): 586 - 595
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1024 KB)  

    A design for a 3-MW 140-GHz gyrotron based on the use of a coaxial cavity is given. The cavity mode is TE21,13, chosen so that the ohmic heating on both the inner and outer conductors would be low enough for CW operation. The mode selection process, nonlinear, multimode and time-dependent modeling of the beam wave interaction, and gun design are discussed in detail. An inverted magnetron injection gun (MIG) is used to accommodate the inner conductor. The radiation is coupled out via a quasi-optical mode converter, consisting of an irregular cylindrical waveguide section followed by a step-cut launching aperture and a single near-parabolic mirror. The design of these components is also described View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient electrostatic-accelerator free-electron masers for atmospheric power beaming

    Publication Year: 1996 , Page(s): 1050 - 1057
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    The electrostatic-accelerator free-electron laser (EA-FEL) operating at mm wavelength is considered as a source for energy transfer through the atmosphere to a high altitude platform. The high average power and high efficiency attainable from appropriately designed EA-FEL make it a suitable candidate as an efficient source of mm-waves for power beaming from a ground station. Various aspects of the FEL as a high power oscillator (operating voltage, e-beam current, gain and efficiency) are reviewed; design tradeoffs are described. The study includes consideration of typical requirements of power beaming to a high altitude platform such as atmospheric absorption versus frequency and transmitting and receiving antenna requirements. A conceptual design of a compact, moderate voltage (0.5-3 MeV), high current (1-10 Amp) EA-FEM operating in the mm-wavelength band is presented as an efficient power source for space beaming. The FEM design parameters are presented based on analytical and numerical models. Expected performance parameters of an FEL (gain, energy conversion efficiency, average power) are discussed as related to the proposed application View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Steven J. Gitomer, Ph.D.
Senior Scientist, US Civilian Research & Development Foundation
Guest Scientist, Los Alamos National Laboratory
1428 Miracerros Loop South
Santa Fe, NM  87505  87505  USA
tps-editor@ieee.org
Phone:505-988-5751
Fax:505-988-5751 (call first)