Gyroklystron Research at CCR

Transcription

1 Gyroklystron Research at CCR Lawrence Ives, Michael Read, Jeff Neilson, Philipp Borchard and Max Mizuhara Calabazas Creek Research, Inc Comer Drive, Saratoga, CA W. Lawson IREAP, University of Maryland College Park, Maryland

2 Acknowledgement Work supported by the US Department of Energy contracts DE-FG02-04ER83917, DE-FG02-06ER84454, and DE- FG03-99ER82754

3 Gyroklystron Designs GHz, 10 MW - Available for testing 30 GHz, 30 MW gyroklystron Phase I design completed spring Phase II program not funded 30 GHz, 50 MW gyroklystron Phase I design completed spring No Phase II proposal submitted

4 Gyroklystron design goals Pulse power Gain Pulse width Frequency Voltage 25/50 MW ~ 50 db ~ 1 microsecond 30 GHz 500 kv

5 50 MW Design Parameters Designs at fundamental and second harmonic Parameter Fundamental Second harmonic Peak Efficiency (%) Large signal gain (db) Output Power (MW) Input Power (kw) Drive frequency (khz) Beam guiding radius (cm) Beam Voltage (kv) Beam Current (A) Average velocity ratio Axial velocity spread (%) 6 5 Drive cavity f (GHz) Tube length (cm) Drift tube ID (cm).78 NA Drift tube OD (cm)

6 Electron Gun for Fundamental Mode kv

7 Inverted MIG R (cm) Cathode anode mod anode (-10 kv kv) inner conductor Z (cm)

8 Electron Gun for Second Harmonic R (cm) Z (cm) kv Space Charge Limited

9 Input coupler cavity input guide

10 Second Harmonic Cavity Radius (cm) / Field (T) Axial distance (cm)

11 Output Guide for Second Harmonic TE 01 Input, 99.9% TE 01 Output

12 Challenges and Goals for Coaxial Gyroklystron Investigate alternative gun designs with improved performance Utilize coaxial inserted supported at both ends for precisions alignment Investigate circuit designs with high efficiency Develop output coupler consistent with coax conductor

13 Fundamental Mode Cavity Radius (cm) / Field (T) Axial distance (cm)

14 RF Structure cavities cavities inner conductor

15 25 MW RF Structure Summary Number of cavities: 5 Cavity mode TE 01 Magnetic field ~1.43 Tesla (fundamental) Q (all but output cavity) 200 Q (output cavity) 240 Stability zero-drive stable for all modes Efficiency 54% at 33 MW Gain 60 db for η=54%

16 Bandwidth 0.25%

17 1.5 m Collector Output window Output coupler Input coupler Inverted MIG

18 Input and Output couplers Wrap-around coupler used for the input Output coupling through the inner conductor is simpler and gives desired TE 01 output mode

19 Input Coupler cavity input guide

20 Output coupler outer conductor inner conductor connecting pins output cavity

21 Output cavity RF Electric Field Inner conductor Inner conductor of coax output waveguide Maximum RF electric field is 23 MV/m

22 Output coupler RF electric field

23 TE 01 mode Output window Traveling wave design used to minimize fields at ceramic

24 Fundamental Mode Collector Peak power is limiting factor Final design has peak temperature of 240 C

25 Collector for Second Harmonic Temperature Rise (K) Heat Flux (W/cm2)

26 Thermal Issues Average power of 8 kw average power does not pose a significant problem with cooling center conductor from gun and collector end Pulse heating in output cavity and collector motivated careful design, but all peak temperatures and temperature rises are within engineering limits

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28 Magnet is procured and available Superconducting Magnet

29 W-Band Gyroklystron Lawrence Ives, M. Read, J. Neilson, M. Mizuhara, T. Robinson and D. Marsden Calabazas Creek Research, Inc. W. Lawson and B. Hogan Institute for Plasma Research, University of Maryland Funded by SBIR grant DOE DE- FG03-99ER82754

30 Specifications Parameter Goal Frequency GHz Design Output Power 10 MW Efficiency 37% Gain 56 db Pulse length ~ 1 microsec Duty cycle ~ Operating mode TE01 or TE02 Output mode TE01/02 Composite Operating Voltage 500 kv Operating Current 50 A

31 Fundamental TE 01 6 Gyroklystron Circuit TE01/02 Mode Converter Radial location (mm) nd Harmonic TE Axial location (mm)

32 MAGYKLY2000 Calculation Using Measured Cavity F and Q Output frequency (GHz) Drive power (W) 23 Electronic efficiency (%) 36 Output power (MW) 10 Gain (db) 56

33 Availability The gyroklystron is fully assembled, baked, and ready for operation Superconducting magnet with power supplies are in inventory Two RF driver TWTs are in stock

34 Summary 91 GHz gyroklystron is completed and available for testing 30 GHz designs generated at 25 and 50 MW tubes can be build if funding provided