New Type of sub-THz Oscillator and Amplifier Systems Based on Helical-Type Gyro-TWTs

New Type of sub-THz Oscillator and Amplifier Systems Based on Helical-Type Gyro-TWTs

This work presents the development of a new sub-THz source for the generation of trains of coherent high-power ultra-short pulses at 263 GHz via passive mode-locking of two coupled helical gyro-TWTs. For the first time, it is shown that the operation of such passive mode-locked helical gyro-TWTs in...

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Detalles Bibliográficos
Otros Autores: Marek, Alexander, author (author)
Formato: Libro electrónico
Idioma:Inglés
Publicado: Karlsruhe, Baden : KIT Scientific Publishing 2023.
Colección:Karlsruher Forschungsberichte aus dem Institut für Hochleistungsimpuls- und Mikrowellentechnik.
Materias:
Passive resistance.
Ver en Biblioteca Universitat Ramon Llull:https://discovery.url.edu/permalink/34CSUC_URL/1im36ta/alma991009871134506719
Tabla de Contenidos:
  • Foreword of the Editor i
  • Zusammenfassung iii
  • Abstract v
  • Abbreviations xiii
  • List of Symbols xvii
  • 1 Introduction 1
  • 1.1 Aims and Objectives 1
  • 1.2 State of the Art 4
  • 1.3 Method of Mode-Locking in Laser Physics 7
  • 1.4 From Optics to Microwaves 13
  • 1.5 Outline 14
  • 2 Fundamental Theory of Passive Mode-Locked Oscillators 17
  • 2.1 Characteristics of Ultra-Short Pulses 17
  • 2.1.1 Slowly Varying Amplitudes 17
  • 2.1.2 Ultra-Short Pulses 18
  • 2.2 Haus Master Equation of Passive Mode-Locked Oscillators 20
  • 2.2.1 Amplification 21
  • 2.2.2 Saturable Loss and Self Amplitude Modulation 23
  • 2.2.3 Dispersion 24
  • .2.4 Slow Components 25
  • 2.2.5 Time-Shift 27
  • 2.2.6 Typical Values 28
  • 2.3 Passive Mode-Locked Oscillators for MW Frequencies 30
  • 2.3.1 Fast and Slow Components 30
  • 2.3.2 Fast Amplifier and Fast Absorber 31
  • 2.3.3 Slow Amplifier and Fast Absorber 35
  • 2.4 Conclusion 37
  • 3 MW Components for Passive Mode-Locked Oscillators 39
  • 3.1 Helical Gyro-TWTs 39
  • 3.1.1 Helically Corrugated Waveguides 41
  • 3.1.2 Electron Cyclotron Maser Interaction 46
  • 3.1.3 Large Orbit Electron Beams 50
  • 3.1.4 CUSP-Type Electron Guns 52
  • 3.1.5 Waveguide Polarizers 60
  • 3.1.6 Horn Antenna and Collector 62
  • 3.1.7 Broadband Windows 64
  • 3.1.8 In-and Out-coupling of High-Power Signals 68
  • 3.2 Cyclotron Absorber 70
  • 3.3 Helical Gyro-TWTs as Saturable Absorbers 77
  • 3.4 Passive Components 78
  • 3.4.1 Jones Calculus 78
  • 3.4.2 Polarization Splitter 81
  • 3.4.3 Polarizers 84
  • 4 Simulation Model for Gyro-Devices 87
  • 4.1 Field Equations 89
  • 4.1.1 Helically Corrugated Waveguide 91
  • 4.1.2 Range of Validity 94
  • 4.1.3 Multi-Mode Simulations 100
  • 4.2 Equations of Motion 101
  • 4.2.1 Source Term 103
  • 4.2.2 Space Charge 105
  • 4.3 Numerical Solution 107
  • 4.3.1 Field Equations 108
  • 4.3.2 Coupled Equations of Helical Waveguides 110
  • 4.3.3 Source Term and Equations of Motion 111
  • 4.3.4 Implementation and GPU Acceleration 112
  • 4.4 Comparison with Existing Approaches 116
  • 5 Design of Amplifier and Absorber 119
  • 5.1 Amplifier 120
  • 5.1.1 Helical Interaction Region 121
  • 5.1.2 Power Capability 122
  • 5.1.3 Synchronized Operation Regime 125
  • 5.1.4 Slippage Operation Regime 126
  • 5.1.5 Length of the Interaction Region 127
  • 5.1.6 Amplification of Ultra-Short Pulses 129
  • 5.2 Saturable Absorber 134
  • 5.2.1 Helical Gyro-TWT Absorber 135
  • 5.2.2 Cyclotron Absorber 137
  • 5.2.3 Ultra-Short Pulses in a Saturable Absorber 142
  • 5.3 Effects of Manufacturing Tolerances 147
  • 6 System Design 151
  • 6.1 Simulation of a Passive Mode-Locked Oscillator 151
  • 6.2 Different Passive Mode-Locked Oscillators 153
  • 6.3 Generated Output Signal 157
  • 6.3.1 Pulse Power and Length 158
  • 6.3.2 Pulse Shape 160
  • 6.3.3 Spectrum 161
  • 6.4 Transient Behavior of the Oscillator 167
  • 6.4.1 Start-up in the Hard Excitation Region 167
  • 6.4.2 Start-up in the Soft Excitation Region 169
  • 6.4.3 Achievable Repetition Rate 171
  • 6.4.4 Achievable Coherence 174
  • 6.5 Realistic Start-Up Scenarios 178
  • 6.5.1 High-Gain HelicalGyro-TWT 179
  • 6.5.2 Hard Excitation with a High-Gain HelicalGyro-TWT 181
  • 6.6 Conclusion 182
  • 7 Simulation Model for Passive Components 185
  • 7.1 Surface Integral Equations 186
  • 7.2 Numerical Solution 188
  • 7.2.1 Adaptive Cross Approximation 189
  • 7.2.2 Sparsified Adaptive Cross Approximation 190
  • 7.3 New Zero-Cost Preconditioner 192
  • 7.3.1 GMRE Swith Preconditioner 192
  • 7.3.2 FGMRE Swith Zero-Cost Preconditioner 193
  • 7.3.3 Performance of the Zero-Cost Preconditioner 195
  • 7.4 Implementation and Verification 200
  • 7.5 Dispersion of Helically Corrugated Waveguides 203
  • 8 Design of the Feedback System 205
  • 8.1 Requirements 206
  • 8.2 Feedback System via Overmoded Waveguides 208
  • 8.2.1 Waveguide 210
  • 8.2.2 Broadband Polarization Splitter 212
  • 8.2.3 Broadband Polarizer 215
  • 8.2.4 Performance of the Complete Feedback System 219
  • 8.3 Additional Operation Modes 220
  • 8.3.1 Operation in the Hard Excitation Region 222
  • 8.3.2 New Type of Two-Stage Amplifier 224
  • 8.3.3 Operation as a CW Source 226
  • 8.4 Conclusion 229
  • 9 Conclusion and Outlook 231
  • A Appendix 239
  • A.1 Split-Step Fourier Method 239
  • A.2 Verification of Electron-Wave Interaction Simulations 240
  • A.2.1 Short-Pulse ITERGyrotron 241
  • A.2.2 W-Band HelicalGyro-TWT 245
  • A.3 Verification of EFIE Solver 249
  • A.3.1 Verification of Simulated Field Distribution 249
  • A.3.2 Verification of Simulated Ohmic-Loss 252
  • A.4 Passive Mode-locked Oscillator with Cyclotron Absorber 254
  • Bibliography 257
  • Contents Acknowledgment 281.

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