Conformal Cross-Flow Axis-Encircling Electron Beam for Driving THz Harmonic Gyrotron

Du, Chao‐Hai; Qi, Xian-Rong; Hao, Baoliang; Chang, Tsun-Hsu; Liu, Pu‐Kun

doi:10.1109/led.2015.2460457

Cited by 10 publications

(9 citation statements)

References 18 publications

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“…Firstly, the emitter contains four parameters, including the oblique angle θc, the emission width Δr, the mean radius rc, and the magnetic field strength at the emission surface Bc. The initial values of θc, Δr, rc, and Bc are derived based on ( 7)- (10). rg is set as 0 to estimate the initial parameters.…”

Section: B Design and Optimization Of The Mcgmentioning

confidence: 99%

“…rg is set as 0 to estimate the initial parameters. rc and Bc are calculated based on (10). The initial values of rc and Bc are 5.0 mm and ~30 Gs, respectively.…”

Section: B Design and Optimization Of The Mcgmentioning

confidence: 99%

“…θc is related to the profile of the magnetic field. A small velocity spread is required to keep a conformal relationship between the profile of the magnetic field and the emitter [10]. It should be noted that the profile of the magnetic field at the emitter region is normally not linear, which means the emitter should also be curved.…”

Section: B Design and Optimization Of The Mcgmentioning

confidence: 99%

See 2 more Smart Citations

Development of a Magnetic Cusp Gun for a 1-THz Harmonic Gyrotron

Zhang

et al. 2021

IEEE Trans. Electron Devices

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Section: B Design and Optimization Of The Mcgmentioning

confidence: 99%

“…rg is set as 0 to estimate the initial parameters. rc and Bc are calculated based on (10). The initial values of rc and Bc are 5.0 mm and ~30 Gs, respectively.…”

Section: B Design and Optimization Of The Mcgmentioning

confidence: 99%

Section: B Design and Optimization Of The Mcgmentioning

confidence: 99%

See 1 more Smart Citation

Development of a Magnetic Cusp Gun for a 1-THz Harmonic Gyrotron

Zhang

et al. 2021

IEEE Trans. Electron Devices

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“…The emitter had a conical section. It was claimed that a curved shape would help to reduce the alpha spread 20 . However, for millimeter-wave gyro-devices operating with a lower order mode, the emitter thickness was relatively small (usually around 0.5 mm) and the machining difficulty and tolerance would counteract the benefits of using a curved shape.…”

Section: Theoretical Analysis and Numerical Simulationsmentioning

confidence: 99%

Investigation on the optimal magnetic field of a cusp electron gun for a W-band gyro-TWA

Zhang

Donaldson

et al. 2018

Physics of Plasmas

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High efficiency and broadband operation of a gyrotron traveling wave amplifier (gyro-TWA) requires a highquality electron beam with low-velocity spreads. The beam velocity spreads are mainly due to the differences of the electric and magnetic fields that the electrons withstand the electron gun. This paper investigates the possibility to decouple the design of electron gun geometry and the magnet system while still achieving optimal results, through a case study of designing a cusp electron gun for a W-band gyro-TWA. A global multiple-objective optimization routing was used to optimize the electron gun geometry for different predefined magnetic field profiles individually. Their results were compared and the properties of the required magnetic field profile are summarized.

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“…Equation (2) suggests that increasing the magnetic compression ratio enhances the pitch factor of the electron beam under the adiabatic condition.In this study, we propose a diode-type electron gun to produce a high-quality annular beam. In contrast to the MIGs, electrons are emitted from a concave cathode surface which is usually used to generate the axis-encircling electron beam (cusp gun) 15,16 . Figure 1(a) shows the proposed structure (grey) overlaid with the magnetic field profile (black), beam trajectories (red), and equal-potential lines (blue in the inset) calculated with the beam voltage of 16 kV.…”

mentioning

confidence: 99%

Nonadiabatic Effects on Beam-Quality Parameters for Frequency-Tunable Gyrotrons

Tsai

Chang

Yamaguchi

et al. 2020

IEEE Trans. Electron Devices

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We propose an unconventional electron gun structure in which the emitter is located on a concave cathode surface with a non-uniform electric field. Such a design violates the intuition that an emitter should place close to a uniform electric field to reduce the velocity spread. The commonly employed design guide based on the adiabatic condition predicts a huge velocity spread of 24%, but the simulation using EGUN code and verified with CST particle studio shows a very low spread of 2.8%. Examining the magnetic moment and the kinetic energy of the beam reveals that the electrons experience a relatively long acceleration process due to the much weak electric field. That's why the non-adiabatic effect matters. In addition to the cyclotron compression and the E × B drift, the "resonant" polarization drift plays a crucial role in reducing the overall velocity spread. Simulations show a decent beam quality with the pitch factor of 1.5 and the transverse velocity spread of 2.8% over a wide range of the magnetic field (7.4 − 8.0 T) and the beam voltage (12 − 22 kV) with a high structural tolerance. The promising results with the wide working range enable the development of continuous frequency-tunable gyrotrons.Gyrotrons based on the mechanism of the electron cyclotron maser (ECM) 1-3 is capable of producing high-power, coherent, terahertz (THz) waves as compared with the classical vacuum electronic tubes. Through decades of development, frequency-tunable gyrotrons receive more and more attentions 4-6 because of the frequency-sensitive applications, such as the enhancement of nuclear magnetic resonance by dynamic nuclear polarization (DNP-NMR) and the measurement of the hyperfine splitting of positronium (Ps-HFS). The beam-wave synchronism for gyrotrons is described as:where ω is the angular frequency, k z is the wavenumber, and s is the cyclotron harmonic number. Ω c is the relativistic electron cyclotron frequency which is related to the magnetic field (B 0 ) and the relativistic gamma factor (γ 0 ), i.e., Ω c = eB 0 /m 0 γ 0 . e and m 0 are the charge and the rest mass of an electron. v z is the electron axial velocity which is associated with the beam voltage (V b ). Equation (1) predicts that the frequency tunability of gyrotrons 7,8 is attainable by adjusting either B 0 or V b . Since the output power of gyrotrons is strongly related to the quality of the electron beam, high-performance electron guns deserve in-depth studies for frequency-tunable gyrotrons. Many types of electron guns have been proposed 9-11 to generate a high-quality beam with a high pitch factor (α) and a low velocity spread (∆v/v). Magnetron injection gun (MIG) 12-14 consisting of a conical-shaped cathode is one of the commonly used electron sources for gyrotrons. Electrons emitted from a convex surface with a maximal electric field are quickly accelerated to a constant value of energy, i.e., p 2 ⊥ + p 2 z = (1 + α 2 )p 2 z = const.. Then, electrons undergo a magnetic compression according to the adiabatic a) Electronic mail: thschang@phys.nthu....

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Conformal Cross-Flow Axis-Encircling Electron Beam for Driving THz Harmonic Gyrotron

Cited by 10 publications

References 18 publications

Development of a Magnetic Cusp Gun for a 1-THz Harmonic Gyrotron

Development of a Magnetic Cusp Gun for a 1-THz Harmonic Gyrotron

Investigation on the optimal magnetic field of a cusp electron gun for a W-band gyro-TWA

Nonadiabatic Effects on Beam-Quality Parameters for Frequency-Tunable Gyrotrons

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