Author

# Robert H. Jackson

Bio: Robert H. Jackson is an academic researcher from United States Naval Research Laboratory. The author has contributed to research in topics: Wiggler & Amplifier. The author has an hindex of 10, co-authored 58 publications receiving 341 citations.

Topics: Wiggler, Amplifier, Free-electron laser, Coaxial, Beam (structure)

##### Papers published on a yearly basis

##### Papers

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11 Apr 1995-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment

TL;DR: In this article, a helical wiggler/axial guide field configuration was employed for the K u -band ubitron at 16.6 GHz for an efficiency of 17.5% and a gain of 29 dB, and an instantaneous bandwidth of 22%.

Abstract: Operation of the Naval Research Laboratory K u -band ubitron has successfully demonstrated a high power/efficiency and broad bandwidth. This device employs a helical wiggler/axial guide field configuration. Performance levels achieved at 16.6 GHz can be summarized as a peak power of 4.2 MW for an efficiency of 17.5% and a gain of 29 dB, and an instantaneous bandwidth of 22%. Substantial beam loss was observed. The specific loss rate was correlated with output power, and reached a level of 50% beam loss at the 4.2 MW level. Nonlinear simulations of the experiment are in good agreement with these observations.

39 citations

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TL;DR: In this paper, a three-dimensional nonlinear formulation of a free-electron laser based upon a coaxial hybrid iron (CHI) wiggler is described, which is in good agreement with the Poisson/Superfish group of codes.

Abstract: A three‐dimensional nonlinear formulation of a free‐electron laser based upon a coaxial hybrid iron (CHI) wiggler is described. The CHI wiggler is created by insertion of a central rod and an outer ring [composed of alternating ferrite and dielectric spacers in which the ferrite (dielectric) spacer on the central rod is opposite to the dielectric (ferrite) spacer on the outer ring] along the axis of a solenoidal. An analytic model of the CHI wiggler is developed which is in good agreement with the Poisson/Superfish group of codes. The free‐electron laser (FEL) formulation is a slow‐time‐scale analysis of the interaction of an annular electron beam with the CHI wiggler in a coaxial waveguide. The electromagnetic field is represented as the superposition of the vacuum transverse electric (TE), transverse magnetic (TM), and transverse electromagnetic (TEM) modes of the waveguide, and a set of nonlinear second‐order differential equations is derived for the amplitudes and phases of these modes. These equation...

38 citations

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01 Mar 1994-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment

TL;DR: In this paper, a hybrid iron (CHI) wiggler was developed for small periods with high field amplitude, high beam current acceptance, and excellent transverse focusing and beam propagation properties.

Abstract: A wiggler design has been developed which is scalable to small periods with high field amplitude, high beam current acceptance, and excellent transverse focusing and beam propagation properties. The coaxial hybrid iron (CHI) wiggler design consists of a coaxial arrangement of alternating ferromagnetic and non-ferromagnetic rings with the central portion of the coax shifted by one half period. The entire arrangement is immersed in a solenoidal field which results in a cylindrically symmetric periodic field. FEL configurations using this wiggler design have the potential for high power, high frequency coherent generation in relatively compact systems. Analytic and simulated characteristics of the CHI wiggler are discussed.

35 citations

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TL;DR: In this article, a model of the self-fields associated with the charge density and current of the electron beam is incorporated into three-dimensional nonlinear formulations of the interaction in free-electron lasers for both planar and helical wiggler configurations.

Abstract: A model of the self‐fields associated with the charge density and current of the electron beam is incorporated into three‐dimensional nonlinear formulations of the interaction in free‐electron lasers for both planar and helical wiggler configurations. The model assumes the existence of a cylindrically symmetric electron beam with a flat‐top density profile and a uniform axial velocity, and the self‐electric and self‐magnetic fields are determined from Poisson’s equation and Ampere’s law. Diamagnetic and paramagnetic effects due the electron beam interaction with the wiggler field are neglected; hence, the model breaks down when the wiggler‐induced transverse displacement is comparable to the beam radius. The nonlinear formulations are based upon the arachne and wigglin codes, which represent slow‐time‐scale formulations for the evolution of the amplitudes and phases of a multimode superposition of vacuum waveguide modes. The electron dynamics in these codes are treated by means of the complete three‐dimen...

35 citations

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01 Jun 1999-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment

TL;DR: In this article, a resonance between the transverse wiggler and cyclotron motions of the beam exists which can enhance the Free-Electron Maser interaction, and the difference in behavior on either side of this resonance is presented.

Abstract: Due to the nature of the Coaxial Hybrid Iron wiggler, a resonance between the transverse wiggler and cyclotron motions of the beam exists which can enhance the Free-Electron Maser interaction. The difference in behavior on either side of this resonance is presented. Amplification with a bandwidth on the order of a few percent was achieved. In spite of beam propagation problems, the gain was about 5 dB for operation below gyroresonance, and 7 dB above it, when wideband grazing intersection operation was achieved. A gain as high as 13.5 dB was obtained for cutting intersection between the beam line and the TE 01 dispersion curve.

23 citations

##### Cited by

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TL;DR: A review of the development of high-power gyrotron oscillators for long-pulse or CW operation and pulsed gyrotrons for many applications can be found in this article.

Abstract: This paper presents a review of the experimental achievements related to the development of high-power gyrotron oscillators for long-pulse or CW operation and pulsed gyrotrons for many applications. In addition, this work gives a short overview on the present development status of frequency step-tunable and multi-frequency gyrotrons, coaxial-cavity multi-megawatt gyrotrons, gyrotrons for technological and spectroscopy applications, relativistic gyrotrons, large orbit gyrotrons (LOGs), quasi-optical gyrotrons, fast- and slow-wave cyclotron autoresonance masers (CARMs), gyroklystrons, gyro-TWT amplifiers, gyrotwystron amplifiers, gyro-BWOs, gyro-harmonic converters, gyro-peniotrons, magnicons, free electron masers (FEMs), and dielectric vacuum windows for such high-power mm-wave sources. Gyrotron oscillators (gyromonotrons) are mainly used as high-power millimeter wave sources for electron cyclotron resonance heating (ECRH), electron cyclotron current drive (ECCD), stability control, and diagnostics of magnetically confined plasmas for clean generation of energy by controlled thermonuclear fusion. The maximum pulse length of commercially available 140 GHz, megawatt-class gyrotrons employing synthetic diamond output windows is 30 min (CPI and European KIT-SPC-THALES collaboration). The world record parameters of the European tube are as follows: 0.92 MW output power at 30-min pulse duration, 97.5% Gaussian mode purity, and 44% efficiency, employing a single-stage depressed collector (SDC) for energy recovery. A maximum output power of 1.5 MW in 4.0-s pulses at 45% efficiency was generated with the QST-TOSHIBA (now CANON) 110-GHz gyrotron. The Japan 170-GHz ITER gyrotron achieved 1 MW, 800 s at 55% efficiency and holds the energy world record of 2.88 GJ (0.8 MW, 60 min) and the efficiency record of 57% for tubes with an output power of more than 0.5 MW. The Russian 170-GHz ITER gyrotron obtained 0.99 (1.2) MW with a pulse duration of 1000 (100) s and 53% efficiency. The prototype tube of the European 2-MW, 170-GHz coaxial-cavity gyrotron achieved in short pulses the record power of 2.2 MW at 48% efficiency and 96% Gaussian mode purity. Gyrotrons with pulsed magnet for various short-pulse applications deliver Pout = 210 kW with τ = 20 μs at frequencies up to 670 GHz (η ≅ 20%), Pout = 5.3 kW at 1 THz (η = 6.1%), and Pout = 0.5 kW at 1.3 THz (η = 0.6%). Gyrotron oscillators have also been successfully used in materials processing. Such technological applications require tubes with the following parameters: f > 24 GHz, Pout = 4–50 kW, CW, η > 30%. The CW powers produced by gyroklystrons and FEMs are 10 kW (94 GHz) and 36 W (15 GHz), respectively. The IR FEL at the Thomas Jefferson National Accelerator Facility in the USA obtained a record average power of 14.2 kW at a wavelength of 1.6 μm. The THz FEL (NOVEL) at the Budker Institute of Nuclear Physics in Russia achieved a maximum average power of 0.5 kW at wavelengths 50–240 μm (6.00–1.25 THz).

279 citations

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Rice University

^{1}TL;DR: In this paper, a waveguide with two or more substantially parallel conductive elements is proposed for terahertz (THz) sensing applications, where it is possible to direct the THz pulse inside of containers or around corners, where line-of-sight optics are not practical.

Abstract: Systems for THz transmission using new types of THz waveguides with low loss, negligible group velocity dispersion and structural simplicity are described herein. The THz system incorporates the use of a waveguide with two or more substantially parallel conductive elements which may enable many new THz sensing applications. It is now possible to direct the THz pulse inside of containers or around corners, where line-of-sight optics are not practical. Moreover, the systems allow use of either radially polarized or linearly polarized THz antennas. The disclosed systems are compatible with existing terahertz generation and detection techniques.

193 citations

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Rice University

^{1}TL;DR: In this paper, a terahertz sensor system was proposed for coupling terahersz (THz) radiation to a coaxial waveguide consisting of an antenna that generates THz radiation having a mode that matches the mode of the waveguide.

Abstract: A system for coupling teraherz (THz) radiation to a coaxial waveguide comprises an antenna that generates THz radiation having a mode that matches the mode of the waveguide. The antenna may comprise a pair of concentric electrodes, at least one of which may be affixed to or formed by one end of the waveguide. The radiation may have wavelengths between approximately 30 μm and 3 mm. The waveguide may comprise an inner core and an outer wall defining an annular region. A terahertz sensor system may comprise a terahertz antenna comprising first and second concentric electrodes, means for generating a field across the trodes and means for triggering the emission of terahertz radiation, a first waveguide having first and second ends, said first end being coupled to said antenna so as to receive at least a portion of said terahertz radiation, and a sensor for detecting said terahertz radiation.

138 citations

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01 Mar 2000-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms

TL;DR: The Forschungszentrum Rossendorf (FZR) is constructing a superconducting Electron Linac with high Brilliance and low Emittance (ELBE) which can deliver a 1 mA cw beam of 40 MeV as discussed by the authors.

Abstract: The Forschungszentrum Rossendorf (FZR) is constructing a superconducting Electron Linac [F. Gabriel, J. Voigtlander, et al., ELBE Design Report 1998, http://www.fz-rossendorf.de/FWQ/report_d.htm; Annual Report 1996, FZR-179 (1997) 3; Annual Report 1997, FZR-215 (1998) 3] with high Brilliance and low Emittance (ELBE) which can deliver a 1 mA cw beam of 40 MeV. ELBE will be equipped with a free-electron laser (FEL) system for the production of infrared (IR) light in the range 5–300 μm and will thus cover the range from the infrared to the THz regime. The electron beam can also be used to generate X-rays, bremsstrahlung, positrons or fast neutrons.

99 citations

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TL;DR: In this paper, various coherent radiation emission processes are discussed including spontaneous emission, coherent spontaneous superradiance, and stimulated super-radiance from a randomly distributed electron beam, where spontaneous emission is considered.

Abstract: Electron beams can generate radiation spanning a wide range of the electromagnetic spectrum. Creating temporal structure in the beam density results in intense radiation emission proportional to the square of the particle number as compared to the linear dependence on particle number from a randomly distributed electron beam. In this article various coherent radiation emission processes are discussed including spontaneous emission, coherent spontaneous superradiance, and stimulated superradiance.

98 citations