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Detailed Analysis of the Interception Current Predicted by the large-signal code TESLA for an Experimental Multiple-Beam Klystron

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IEEE TRANSACTIONS ON ELECTRON DEVICES 2009年第5期56卷 877-882页

作者： Chernyavskiy, Igor A. Abe, David K. Levush, Baruch Sci Applicat Int Corp Mclean VA 22102 USA USN Res Lab Washington DC 20375 USA

We present the results of detailed modeling of an experimental eight-beam four-cavity Multiple-beam klystron (MBK) with an emphasis on the effects related to the circuit interception current. The parallel version of the 2.5-D large-signal code TESLA was used as the principal analysis tool. The primary MBK model used eight nonidentical beams/beam tunnels run in eight parallel processes using the measured values of R/Q on each gap of each beam tunnel. The simulation results are compared with the available experimental data and show good agreement between the calculations and measurements, including the predicted level of threshold RF drive power at the first appearance of body current. Additional modeling was performed using a less accurate approximation where all eight beams/beam tunnels were assumed to have identical properties. The results of the two different modeling approaches are analyzed in detail and compared with each other to determine the limits on the accuracy of the respective models.

关键词： Body current large-signal code modeling and simulation multiple-beam klystron (MBK)

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From 2D to 1.5D: Reduced Order Simulations with the large-signal code TESLA 22

From 2D to 1.5D: Reduced Order Simulations with the Large-Si...

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22nd International Vacuum Electronics Conference (IVEC)

作者： Chernyayskiy, Igor A. Naval Res Lab Elect Sci & Technol Div Washington DC 20375 USA

ISBN: (纸本)9781665441056

This work presents results of the study, which involves modifications in the algorithms of the well-known 2D large-signal klystron code TESLA with a goal to improve its performance by simplifications in the physics of its model. The proposed modifications are based on the idea to reduce number of degrees of freedom of particle's motion from 3 down to 1 by restricting their motion along Z-axis only. Essentially, this will assume that magnetic field is infinitely large and one can completely ignore radial motion of particles as they will be "frozen" and allowed move in one direction only. Such modification in effect will reduce dimensionality of the algorithm from 2D down to 1.5D as a price to pay for proposed simplifications in the model. We will discuss pilot results of modeling by using the modified, reduced order algorithm, making main emphasis on advantages and disadvantages ("gains and losses") of such step.

关键词： large-signal code degrees of freedom of motion reduced order algorithm performance of the code

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Design of a linear C-band helix TWT for digital communications experiments using the CHRISTINE suite of large-signal codes

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IEEE TRANSACTIONS ON PLASMA SCIENCE 2002年第3期30卷 1053-1062页

作者： Abe, DK Levush, B Antonsen, TM Whaley, DR Danly, BG USN Res Lab Vacuum Elect Branch Washington DC 20375 USA Sci Applicat Int Corp Mclean VA 22102 USA Univ Maryland Inst Res Elect & Appl Phys College Pk MD 20742 USA Northrop Grumman Corp Rolling Meadows IL 60008 USA

A set of optimization goal functions designed to improve the efficiency and linearity performance of helix traveling-wave tubes (TWT) is described. These goal functions were implemented in the CHRISTINE suite of large-signal helix TWT codes along with a steepest-descent optimization algorithm to automate the process of circuit parameter variation and to facilitate the rapid exploration of alternative TWT designs. We compare the predicted power, efficiency, and linearity of four different helix TWT circuits, each developed according to a different set of optimization criteria. Out of, these designs, a single design was selected to be further developed for use in C, band high-data-rate communications experiments. The detailed design of this linearized TWT with a predicted 1-dB small-signal bandwidth of 1.2 GHz, small-signal centerband gain of 35.7 dB (f(c) = 5.5 GHz), and centerband saturated output power of 52 dBm (158.5 W) is presented.

关键词： digital modulation helix traveling-wave tube high-data-rate communications large-signal code optimization traveling-wave tube (TWT)

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From 2.5-D to 1.5-D: Fast, Reduced-Order Simulations With the TESLA-Family of large-signal codes

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IEEE TRANSACTIONS ON ELECTRON DEVICES 2023年第10期70卷 5353-5358页

作者： Chernyavskiy, Igor A. Naval Res Lab Washington DC 20375 USA

This study presents the introduction of the reduced-order, 1.5-D versions of the TESLA-family of 2.5-D large-signal codes, which have been implemented by simplifications in the particle's motion model by its restriction in a single, z-direction only. This in effect assumes that the guiding magnetic field is infinite what leads to a complete elimination of any transverse motion of particles, including their radial motion and rotation. Such simplifications in the algorithms allow reach up to two-times improvement in their performance due to significantly reduced number of operations, but they also in effect reduce an overall dimensionality of the algorithms from 2.5-D to 1.5-D only. The results of the modeling performed by the newly introduced 1.5-D versions of TESLA-family of large-signal codes and their comparisons with the results of modeling by the original 2.5-D algorithms are discussed in detail. Results of this study allow find accuracy and range of applicability of the 1.5-D large-signal codes and help to determine the place of such reduced-order algorithms.

关键词： Degrees of freedom of motion large-signal code performance of the code reduced-order algorithm

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Increasingly Accurate Stability Study of the Experimental W-Band TWT Using code TESLA-Z Stability Analysis Framework

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IEEE TRANSACTIONS ON ELECTRON DEVICES 2022年第10期69卷 5819-5825页

作者： Chernyavskiy, Igor A. Cook, Alan M. Rodgers, John C. Naval Res Lab Washington DC 20375 USA

We present the results of our comprehensive numerical stability study of the experimental, high-power, two-stage Serpentine W-band traveling-wave tube (TWT) with similar to 10% working bandwidth. This device demonstrated an output power level of similar to 215 W at 92 GHz at the nominal beam voltage of 20 kV and similar to 285 W at an increased beam voltage of 20.8 kV. The experimental device was observed to be stable in all cases when operated within the designed beam voltage range. The onset of instability near the lower band edge was observed at higher beam voltages approaching a threshold value of similar to 21.0 kV. We use the recently developed stability analysis framework, based on the Naval Research Laboratory (NRL) 2-D large-signal code TESLA-Z, to find the predicted threshold of zero-drive instabilities, which could develop near the lower band edge of the experimental W-band TWT. An initial study was done by using a simplified model for geometry of the experimental electrodynamic structure of the TWT, which ignored all interface elements. TESLA-Z predictions for onset of instability, in this case, were found much higher in beam voltage than its measured value. Next, an advanced TESLA-Z-based stability study was performed using a more accurate, detailed model for geometry of the experimental electrodynamic structure of the TWT, including important elements such as couplers (transformers), lossy load (sever), and windows. This more detailed analysis gave more accurate results for the onset of instability, in good agreement with the measurements.

关键词： large-signal code onset of instability stability analysis traveling-wave tube (TWT)

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Quasi-3-D Modeling of Higher Order Mode Instability in a Two-Gap Input Cavity of Broadband MBK

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IEEE TRANSACTIONS ON ELECTRON DEVICES 2018年第6期65卷 2114-2121页

作者： Chernyavskiy, Igor A. Rodgers, John C. Vlasov, Alexander N. Abe, David K. Nguyen, Khanh T. Levush, Baruch Naval Res Lab Washington DC 20375 USA Beam Wave Res Inc Bethesda MD 20814 USA

We present the results of our comprehensive study of the stability of a two-gap input cavity used in an experimental broadband multiple-beam klystron (MBK) with 18 beams and 7 cavities, which was designed for projected > 500 kW maximum output power and similar to 13% bandwidth (so-called NRL MBK-3 design). The device was experimentally observed to be prone to self-excitation at all beam voltages below its designed operational value of similar to 42 kV. Postexperiment examination of the two-gap input cavity revealed traces of breakdown on its face. Detailed simulations performed using a 3-D computational electromagnetic code HFSS have shown presence of a few high-Q higher order modes (HOMs), which could explain self-excitation of the two-gap input cavity in a wide range of beam voltages. To explore HOM instability of the two-gap input cavity of the MBK in greater details, we applied the code TESLA-MB, which represents a parallel extension of the 2-D large-signal klystron code TESLA and which is suitable for an accurate modeling of multiple-beam devices with unique distributions of R/Qs over gaps in all its beam-tunnels.

关键词： Higher order mode (HOM) large-signal code multiple-beam klystron (MBK) stability analysis two-gap cavity wideband operation

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TESLA Modeling of the Linear-Beam Amplifiers

TESLA Modeling of the Linear-Beam Amplifiers

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10th IEEE International Vacuum Electronics Conference

作者： Chernyavskiy, Igor A. Vlasov, Alexander N. Cooke, Simon J. Abe, David K. Levush, Baruch Antonsen, Thomas M., Jr. Pershing, Dean E. Wright, Edward L. Nguyen, Khanh T. Sci Applicat Int Corp 1710 SAIC Dr Mclean VA 22102 USA Univ Maryland College Pk MD 20742 USA Naval Res Lab Washington DC 20375 USA Beam Wave Res Inc Bethesda MD 20905 USA

Recent advances in the development of the large-signal code TESLA are discussed in details from the point of view of the modeling of a wide range of linear-beam amplifiers. The results of TESLA modeling are illustrate... 详细信息

ISBN: (纸本)9781424435005

关键词： large-signal code single-beam and multiple-beams devices klystrons inductive output tubes

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Quasi-3-D Modeling of Higher Order Mode Instability in a Two-Gap Input Cavity of Broadband MBK

Quasi-3-D Modeling of Higher Order Mode Instability in a Two...

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18th International Vacuum Electronics Conference (IVEC)

作者： Chernyavskiy, Igor A. Rodgers, John C. Vlasov, Alexander N. Abe, David K. Nguyen, Khanh T. Levush, Baruch Naval Res Lab Washington DC 20375 USA Beam Wave Res Inc Bethesda MD 20814 USA

关键词： Higher order mode (HOM) large-signal code multiple-beam klystron (MBK) stability analysis two-gap cavity wideband operation

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Modeling of Coupled Cavity TWT with TESLA

Modeling of Coupled Cavity TWT with TESLA

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10th IEEE International Vacuum Electronics Conference

作者： Vlasov, Alexander N. Cooke, Simon J. Levush, Baruch Antonsen, Thomas M., Jr. Chernyavskiy, Igor A. Chernin, David P. USN Res Lab Washington DC 20375 USA Sci Applicat Int Corp Mclean VA 22102 USA Univ Maryland College Pk MD 20742 USA

Recent development of the large-signal 2.5D code TESLA allows for simulations of coupled cavity TWT is presented. The results of TESLA modeling are compared with Christine-CC code simulations.

ISBN: (纸本)9781424435005

Recent development of the large-signal 2.5D code TESLA allows for simulations of coupled cavity TWT is presented. The results of TESLA modeling are compared with Christine-CC code simulations.

关键词： coupled cavity TWT large-signal code Curnow circuit model drive induced instability

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Parallel 2D large-signal Modeling of Cascaded TWT Amplifiers

Parallel 2D Large-signal Modeling of Cascaded TWT Amplifiers

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IEEE International Vacuum Electronics Conference

作者： Igor A. Chernyavskiy Alexander N. Vlasov Baruch Levush Thomas M. Antonsen Khanh T. Nguyen Naval Research Laboratory Washington DC 20375 SAIC McLean VA 22102 Beam Wave Research Inc. Bethesda MD 20814

ISBN: (纸本)9781467359764

The 2.5D large-signal code TESLA-FW was recently developed with the goal to model TWT amplifiers based on the serpentine or folded-waveguide slow-wave structures. Predictions of the large-signal code, applied to the modeling of the single stage amplifiers, were found in a good agreement with the results of the 3D PIC code MAGIC, while its run-time was on orders of magnitude less. To extend applicability of the large-signal code, now we report its conversion into a parallel version, which allows us concurrently model all the stages of a multiple-beam cascaded TWT amplifiers based on serpentine or folded-waveguide slow-wave structures. Newly introduced parallel version of TESLA-FW is applied to model a 3-stage cascaded TWT amplifier to support on-going efforts on its design and further optimization. Obtained results are compared with the predictions of the 3D PIC code MAGIC.

关键词： traveling-wave tube broadband high power amplifier serpentine slow-wave structure folded waveguide slow-wave structure large-signal code parallel modeling

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