EGUN Code Research Articles

Copper coil magnetic system study in a 60 GHz gyrotron design

This paper presents the study of a gyrotron magnetic system with a field intensity of 2.45 T and a triode magnetron injection gun system to achieve electron trajectories into the cavity operating zone to generate a 60 GHz radiofrequency used in electron cyclotron resonance heating applications. The operating mode of the gyrotron is TE4,3. A copper coil system arrangement of four solenoids with a stationary current of 750 A and a magnetic compression of 16.53 with a magnetic field homogeneity of 0.10% over a length of 56 mm in the operating zone was designed. A very good approximation of the magnetic field profile of the copper coil system was obtained using a novel formulation derived from the geometry of the coils. The magnetron injection gun parameters were obtained applying the trade-off equations, resulting in a cathode radius of 13.5 mm. The helicoidal and laminar trajectories of the electrons with a transverse-velocity of 1.175 are obtained from the magnetic and gun systems. The resulting trajectories are generated using the 2-D EGUN code. The study represents an effort to create an Experimental Theoretical Fusion Platform of the High Magnetic Field Program at the Autonomous University of Nuevo León (UANL).

Design and Thermal Analysis of Magnetron Injection Gun for Dual-Band Gyroklystron

In this article, the design and thermal analysis of a novel dual-emitter magnetron injection gun (MIG) for dual-band gyroklystron amplifiers have been completed. First, we determine the operating mode, frequency, current, and other parameters of the dual-band gyroklystron. Then, the geometrical structure of MIG was preliminarily calculated by the trade-off equation and optimized by using the 3-D code CST particle studio and 2-D code EGUN, and the corresponding magnetic guidance system was designed. Finally, the temperature and thermal deformation of the cathode were performed. This dual-emitter MIG can successfully work in the <inline-formula> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula>/ <i>Ku</i>-band, laying the foundation for the development of dual-band gyroklystrons.

Design, Beam-Wave Interaction, and Efficiency Enhancement Studies of Millimeter Wave Gyro-TWT With a Three-Stage Depressed Collector

In this article, a $W$ -band gyrotron traveling wave tube (gyro-TWT) amplifier that uses periodically dielectric-loaded (PDL) waveguide and operates in TE01 mode is designed and studied for its stability against backward wave oscillations and beam wave interaction behavior. The subassemblies including a magnetron injection gun using E-GUN code, RF output window, and electron collector using “MAGIC 3-D” are investigated. The present particle-in-cell (PIC) simulation of millimeter-wave gyro-TWT results in a peak RF power ~195 kW in TE01 mode with an electronic efficiency of ~28% and a saturated gain of ~63 dB. Further, the overall efficiency of the device is enhanced by using a three-stage depressed collector, which is designed and simulated using “MAGIC 3-D. ” The collection efficiency of the present collector is calculated as ~74% and the overall efficiency of the gyro-TWT is improved to ~60%.

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

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$\times$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.

Inverse Magnetron Injection Gun for Megawatt Power, Sub-THz Gyrotron

Inverse magnetron injection gun (IMIG) provides several advantages over simple MIG especially in high-power, high-frequency gyrotron. Sub-millimeter (>230 GHz), high-power (≥1 MW) gyrotrons would be required in futuristic plasma fusion machines to fulfill the need of tens of megawatt RF power for electron cyclotron resonance heating. Here, in this paper, an IMIG is designed for 0.24-THz, 1-MW gyrotron. First, the tradeoff design equations and technical constraints are used to synthesize the electrodes geometry and electrical parameters of IMIG. This synthesized IMIG model is further simulated to finalize the design using electron trajectory code EGUN. Simultaneously, the magnet system including the auxiliary gun coils and superconducting magnets (SCM) is also designed and the obtained magnetic field profile is used in the IMIG simulations. In the case of high-power MIG, the suppression of the beam halo is a major design concern and analyzed critically in the present IMIG design. The shape of the modulating anode and main anode is optimized to make a beam halo shielding. This IMIG is designed for a very high-order mode (TE46,17) simple cylindrical cavity, which confines the range of the tolerance in the electron beam parameters. So, a detailed parametric and misalignment analysis is also performed with respect to the electron beam parameters, such as pitch factor, velocity spread, and guiding center radius spread. These parametric and misalignment analyses would be utter helpful in the fabrication, assembling and testing of the IMIG as well as gyrotron.

Electronic-Tuning Frequency Stabilization of a Terahertz Gyrotron Oscillator

Gyrotron oscillator, as one kind of efficient terahertz (THz) source, is developed with the capability of frequency and power tuning to meet diverse application demands. Due to system nonlinearity, it is quite difficult to achieve high frequency stabilization (FS) during power tuning without using external auxiliary components. This paper proposes an FS scheme with simultaneous power tuning in gyrotron backward-wave oscillator state. This is realized by compensating the detuning electron cyclotron frequency during the electronic tuning process. The required quasi-linear relationship between the electron-beam pitch factor and the accelerating voltage is numerically verified by using the SLAC EGUN code. The investigation focuses on a Watt-level open-cavity gyrotron oscillator. The tens-of-Watts-level output power can be tuned by over 40% at the FS point, and especially the self-adaptive FS reaches the accuracy of about 10-MHz level. The proposed scheme would be attractive for the high-stability THz-wave heating in material sciences and biomedicines.

Design of a Double Anode Magnetron Injection Gun for Q-band Gyro-TWT Using Boundary Element Method

This paper presents a novel design code for double anode magnetron injection guns (MIGs) in gyro-devices based on boundary element method (BEM). The physical and mathematical models were constructed, and then the code using BEM for MIG’s calculation was developed. Using the code, a double anode MIG for a Q-band gyrotron traveling-wave tube (gyro-TWT) amplifier operating in the circular TE01 mode at the fundamental cyclotron harmonic was designed. In order to verify the reliability of this code, velocity spread and guiding center radius of the MIG simulated by the BEM code were compared with these from the commonly used EGUN code, showing a reasonable agreement. Then, a Q-band gyro-TWT was fabricated and tested. The testing results show that the device has achieved an average power of 5kW and peak power ≥ 150 kW at a 3% duty cycle within bandwidth of 2 GHz, and maximum output peak power of 220 kW, with a corresponding saturated gain of 50.9 dB and efficiency of 39.8%. This paper demonstrates that the BEM code can be used as an effective approach for analysis of electron optics system in gyro-devices.

Design of a double-anode magnetron-injection gun for the W-band gyrotron

A double-anode magnetron-injection gun (MIG) was designed. The MIG is for a W-band 10-kW gyrotron. Analytic equations based on adiabatic theory and angular momentum conservation were used to examine the initial design parameters such as the cathode angle, and the radius of the beam emitting surface. The MIG’s performances were predicted by using an electron trajectory code, the EGUN code. The beam spread of the axial velocity, Δvz/vz, obtained from the EGUN code was observed to be 1.34% at α = 1.3. The cathode edge emission and the thermal effect were modeled. The cathode edge emission was found to have a major effect on the velocity spread. The electron beam’s quality was significantly improved by affixing non-emissive cylinders to the cathode.

Magnetron Injection Gun for a Short Pulse, 0.67 THz Gyrotron for Remote Detection of Radioactive Materials

In this paper, the design of electron gun for a 0.67 THz gyrotron is presented. The in-house code MIGSYN is used to estimate the initial gun parameters. The electron trajectory tracing 2.5-dimensional (2.5-D) code EGUN is used to optimize the electron gun design. The parametric analysis and misalignment study is also carried out to provide the flexibility in the actual fabrication of the device.

Design of beam-wave interaction based on high efficiency of a high-power broadband klystron

The paper mainly presents the design of beam-wave interaction of a C-band high-peak-power high-efficiency broadband klystron. The beam-wave interaction section is designed based on considerations of efficiency and bandwidth synthetically. As a part of beam-wave interaction section, buncher section is simulated by Particle-In-Cell (PIC) code to observe the bunching process of electron beam to achieve high conversion efficiency of electron beam and RF field. When it comes to the other part, output circuit is designed as a three-section filter by an output cavity loaded with Chebyshev filter, and the cold test results are given. The beam-wave interaction is simulated by EGUN code and Arsenal-MSU code respectively. The simulated results indicated that, the existence of power dips in the operating bandwidth is verified by Arsenal-MSU code, comparing proper results by EGUN code. Then, the method that design parameters are not adjusted except parameters of buncher cavities to remove potential power dips is described. What is more, the simulated results of electron optics system are given by EGUN code and Arsenal-MSU code respectively. The further hot test results of klystron prove that the whole design of beam-wave interaction is effective.

Design studies of the Ku-band, wide-band Gyro-TWT amplifier

This paper reports a Ku-band, wide band Gyrotron-Traveling-wave-tube(Gyro-TWT) that is currently being developed at Kwangwoon University. The Gyro-TWT has a two stage linear tapered interaction circuit to obtain a wide operating bandwidth. The linearly-tapered interaction circuit and nonlinearly-tapered magnetic field gives the Gyro-TWT a wide operating bandwidth. The Gyro-TWT bandwidth is 23%. The 2d-Particle-in-cell(PIC) and MAGIC2d code simulation results are 17.3 dB and 24.34 kW, respectively for the maximum saturated output power. A double anode MIG was simulated with E-Gun code. The results were 0.7 for the transvers to the axial beam velocity ratio (=alpha) and a 2.3% axial velocity spread at 50 kV and 4 A. A magnetic field profile simulation was performed by using the Poisson code to obtain the grazing magnetic field of the entire interaction circuit with Poisson code.

Numerical design and analysis of parasitic mode oscillations for 95 GHz gyrotron beam tunnel

The beam tunnel, equipped with the high lossy ceramics, is designed for 95GHz gyrotron. The geometry of the beam tunnel is optimized considering the maximum RF absorption (ideally 100%) and the suppression of parasitic oscillations. The excitation of parasitic modes is a concerning problem for high frequency, high power gyrotrons. Considering the problem of parasitic mode excitation in beam tunnel, a detail analysis is performed for the suppression of these kinds of modes. Trajectory code EGUN and CST Microwave Studio are used for the simulations of electron beam trajectory and electromagnetic analysis, respectively.

Design of 28 GHz, 200 kW Gyrotron for ECRH Applications

AbstractThis paper presents the design of 28 GHz, 200 kW gyrotron for Indian TOKAMAK system. The paper reports the designs of interaction cavity, magnetron injection gun and RF window. EGUN code is used for the optimization of electron gun parameters. TE

TRIODE MAGNETRON INJECTION GUN FOR 132 GHZ GYROTRON FOR 200 MHZ DNP-NMR APPLICATION

A 132GHz gyrotron, operating at fundamental harmonic, is designed for the 200MHz DNP-NMR experiment. In this article, the design of high quality electron beam source is presented. 2.5 dimensional code EGUN and 3 dimensional code CST-Particle Studio are used in the design and optimization of electron gun. The design of electron beam source is performed for a band of magnetic fleld values at the emitter surface and cavity center which is necessary for the frequency tunabilty of 2{3GHz needed in DNP/NMR experiments. The results conflrm the axial and transverse velocity spreads around 1% and 2.2% and a pitch factor of 1.5. The parametric analyses are also performed for the various electrical parameters such as emitter voltage, anode voltage, emitter magnetic fleld, etc..

Design of a Triode Magnetron Injection Gun for a 1-MW 170-GHz Gyrotron

A triode magnetron injection gun (MIG) is designed for a 1-MW 170-GHz gyrotron, which will be used in an electron cyclotron resonance heating system for the International Thermonuclear Experimental Reactor. The initial design of MIG is performed by using the in-house code MIGSYN. For the electron-beam emission and propagation, the 2-D code EGUN is implemented. The transverse-to-axial velocity ratio α is 1.37, and the transverse velocity spread less than 4% is realized. The results are also validated against two other 2-D and 3-D codes, i.e., TRAK and CST-Particle Studio, respectively, which are in close agreement. From the fabrication and operation point of view, the parametric analysis and misalignment study of electron beam are also performed.

Electron beam emission and interaction of double-beam gyrotron

This paper presents the numerical simulation of a double-beam magnetron injection gun (DB-MIG) and beam-wave interaction for 60GHz, 500kW gyrotron. The beam-wave interaction calculations, power and frequency growth estimation are performed by using PIC code MAGIC. The maximum output power of 510kW at 41.5% efficiency, beam currents of 6A and 12A, electron beam velocity ratios of 1.41 and 1.25 and beam voltage of 69kV are estimated. To obtain the design parameters, the DB-MIG with maximum transverse velocity spread less than 5% is designed. The computer simulations are performed by using the commercially available code EGUN and the in-house developed code MIGANS. The simulated results of DB-MIG design obtained by using the EGUN code are also validated with another trajectory code TRAK, which are in good agreement.

Numerical Design of Megawatt Gyrotron with 120 GHz Frequency and 50% Efficiency for Plasma Fusion Application

The design of 120 GHz, 1 MW gyrotron for plasma fusion application is presented in this paper. The mode selection is carried out considering the aim of minimum mode competition, minimum cavity wall heating, etc. On the basis of the selected operating mode, the interaction cavity design and beam-wave interaction computation are carried out by using the PIC code. The design of triode type Magnetron Injection Gun (MIG) is also presented. Trajectory code EGUN, synthesis code MIGSYN and data analysis code MIGANS are used in the MIG designing. Further, the design of MIG is also validated by using the another trajectory code TRAK. The design results of beam dumping system (collector) and RF window are also presented. Depressed collector is designed to enhance the overall tube efficiency. The design study confirms >1 MW output power with tube efficiency around 50% (with collector efficiency).

Integrated Design of Undepressed Collector for Low Power Gyrotron

A 42 GHz, 200 kW continuous wave (CW) gyrotron, operating at TE03 mode is under development for the electron cyclotron resonance plasma heating of the Indian TOKAMAK system. The gyrotron is made up of an undepressed collector. The undepressed collector is simple to design and cost effective. In this paper, a detailed design study of the undepressed collector for the 42 GHz gyrotron is presented. The EGUN code is used to analyze the spent electron beam trajectory for the maximum spread to reduce the power loading on the collector surface. To achieve wall loading ≤1 kW/cm2, a collector with a length of 800 mm and a radius of 42.5 mm is designed. The design also includes the three magnet systems around the collector for maximum and uniform beam spread. The thermal and the structural analyses are done using the ANSYS code to optimize the collector structure and dimensions with tolerance.

Design of Magnetically Tunable Magnetron Injection Guns for Gyrotrons at Multiple Frequencies

In this paper, the design of a triode-type magnetically tunable magnetron injection gun (MT-MIG) is presented for 1-MW 110-, 120-, and 127.5-GHz-frequency gyrotrons with the various operating modes. Some basic equations relevant to the problem available in the literature have been used to obtain the preliminary design. Computer simulation has been performed by using the commercially available code EGUN. The triode-type MT-MIG with the accelerating voltage of 80 kV, the beam current of 40 A, the average transverse-to-axial velocity ratio of the electron beam of 1.26-1.35, and the maximum transverse velocity spread of less than 5% has been designed. Tuning of the MT-MIG is performed by varying the magnetic field.

Analysis of parasitic oscillations in 42 GHz gyrotron beam tunnel

Parasitic oscillation excitation analysis has been carried out for the 42 GHz gyrotron beam tunnel. This article presents a systematic approach for the analysis of parasitic oscillation excitation. The electron trajectory code EGUN has been used for the estimation of the electron beam parameters in the beam tunnel. The electromagnetic simulation code CST-MS has been used for the eigenmode and Q value analysis. The analysis of the parasitic oscillations has been performed for the symmetric TE modes and the first three cavity side copper rings. Four different approaches- the Q value study, the mode maxima-electron beam radius mismatching, the electron cyclotron frequency-mode excitation frequency mismatching and the backward wave interaction analysis- have been used for the parasitic oscillation analysis.