New Type of sub-THz Oscillator and Amplifier Systems Based on Helical-Type Gyro-TWTs / Alexander Marek.

Format:

Book

Author/Creator:

Marek, Alexander, author.

Series:

Karlsruher Forschungsberichte aus dem Institut für Hochleistungsimpuls- und Mikrowellentechnik.

Karlsruher Forschungsberichte aus dem Institut für Hochleistungsimpuls- und Mikrowellentechnik

Language:

English

Subjects (All):

Passive resistance.

Physical Description:

1 online resource (324 pages)

Place of Publication:

Karlsruhe, Baden : KIT Scientific Publishing, 2023.

Summary:

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 the hard excitation regime is of particular importance to reach the optimal coherency of the generated pulses. This could be of particular interest for some new time-domain DNP-NMR methods.

Contents:

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.

Notes:

Description based on: online resource; title from PDF information screen (directory.doabooks.org, viewed March 30, 2023).

Includes bibliographical references and index.