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Development of The Klystrons for J-PARC Project

Development of The Klystrons for J-PARC Project. Kenichi Hayashi and Osamu Yushiro Toshiba Electron Tubes & Devices Co., LTD. Contents. Outline of the J-PARC project What kinds of klystron are used? What are the klystrons like? 324 - MHz, 3 - MW Klystron: E3740A Design Test results

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Development of The Klystrons for J-PARC Project

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  1. Development of The Klystrons for J-PARC Project Kenichi Hayashi and Osamu Yushiro Toshiba Electron Tubes & Devices Co., LTD.

  2. Contents • Outline of the J-PARC project • What kinds of klystron are used? • What are the klystrons like? • 324 - MHz, 3 - MW Klystron: E3740A • Design • Test results • Some of problems • 972 - MHz, 3 - MW Klystron: E3766 • We are now developing this tube. • Brief on design and test results • Summary

  3. J-PARC at JAERI Tokai site Nuclear and Particle Physics Facility Materials Life Science Facility 3 GeV Rapid Cycling Synchrotron (350 m) Linac (350 m) 50 GeV Synchrotron (1600 m) Accelerator-Driven Transmutation Experimental Facility Neutrino Experimental Facility

  4. To 3 GeV RCS To ADS The 400 MeV Linac of J-PARC • The linac requires two types of klystron. • 20 of the 324-MHz klystron, E3740A are used at DTL. • 23 of the 972-MHz klystron, E3766 are used at ACS. E3740A E3766

  5. Specs & Design Parameters of the Klystrons Triode-type electron gun for anode modulating

  6. 324-MHz Klystron E3740A: Overall Design • Aim of designing (against growing in size due to low operating frequency) • To reduce size and trim weight • By unifying the tube with the focusing solenoid to provide adequate mechanical strength. • By trimming each component. • Limitation of the building and easy handling • By placing the tube horizontally. about 65% lighter than the same-size tube we have developed.

  7. E3740A: Klystron & Klystron Assembly Output waveguide Electron gun Interaction cavities Collector Output window ~ 5 m ~3,200 kg with oil Focusing solenoid Oil tank Klystron Stand

  8. The photo of the E3740A Output window & waveguide Oil tank Collector Focusing solenoid Electron gun Interaction cavities

  9. E3740A: Design of the electron gun • To reduce the surface gradient by optimizing the electrode configuration. • To assure long life and stable emission by adopting metal-coated cathode. Cathode terminal Anode terminal Body • Beam trajectory from EGUN • Beam diameter 30 mm • Beam ripple < 3% • Surface gradient 65 kV/cm 94 kV Anode Cathode 110 kV

  10. Efficiency (%) Input power (W) E3740A: Design of the interaction circuit To shorten the tube length by ~25% using the 2nd harmonic cavity Gun side Collector side Optimizing the parameters using FCI (Field Charge Interaction 2+1/2 PIC code)

  11. E3740A: Design of the output circuit T-bar structrure : To simplify the coaxial-to-rectangular conversion section. Qext ~ 13 wave wave T bar Output cavity WR2300 Window ( TiN coated Al2O3) The simulation was done using HFSS code:Model and result.

  12. E3740A: Test Results 1 Anode voltage (a) Beam current (b) Input power Output power (MW) Output power Beam voltage Anode current Input power (W) t: 0.1 ms/div Transfer characteristics Traces of the beam & wave parameters (a) Beam voltage: 110 kV, Anode voltage: 91.7 kV, Beam current: 48.2 A (b) Beam voltage: 104 kV, Anode voltage: 86.5 kV, Beam current: 43.5 A

  13. E3740A: Summary of Operation

  14. E3740A: Problem 1, Oscillation • Oscillation at the main frequency • We observed oscillation at 324 MHz at the beam voltage above 90 kV for the first tube. • Power level of the oscillation reached up to 300 kW. • We found from various experiments and analyses that • The oscillation occurred in the input cavity. • Due to reflected electrons from the collector. • Measures: • Enlarging the collector to decrease the reflected electron. • Lowering the external Q factor of the input cavity.

  15. E3740A: Change in collector size f100 f100 f70 The first tube The second tube The final tube 0.07% 0.34% 0.18% Ratio of reflected electron to incident beam

  16. E3740A: Magnetic field distribution First Final Magnetic field (mT) First f70 f100 Final f70 • We observed during the test of the second tube that the output power sometimes failed at random. Inner diameter of drift tube: f70 to f100 Confined slow ions and electrons

  17. 972-MHz Klystron E3766: Overall Design • The tube has the same beam parameters as the E3740A to use the common power supply system. • 6 cavities for broad bandwidth 10 MHz (-3 dB). Collector Output window 2.93 m Interaction cavities Electron gun

  18. E3766: Test results • We are now testing the tube and we have confirmed that: • an output power of up to 2 MW was obtained at a beam voltage of 97 kV with an efficiency of 52%. • We intend to achieve 3-MW output by this September.

  19. Summary • The 324-MHz, 3-MW, long-pulse klystron E3740A has been developed in collaboration with KEK and JAERI. • We have confirmed : • The maximum power of 3.03 MW. • Stable operation with efficiencies above 56%. • The tube is put into commercial production: • We have already produced 13 sets, and we intend to produce 20 sets in total by this September.

  20. Efficiency Gain Output power (MW) Efficiency (%) & Gain (dB) Output power Beam current (A) E3740A: Test Results 2 Saturation characteristics

  21. E3766: Design of the electron gun Same design principles as the E3740A • To reduce the surface gradient by optimizing the electrode configuration • To assure long life and stable emission by adopting metal-coated cathode Beam diameter 21 mm Drift-tube diameter 30 mm Beam ripple < 2% Surface gradient 65 kV/cm at 120 kV Beam trajectory from EGUN

  22. E3766: Design of the output circuit • To shorten the output circuit by using step-waveguide structure. • A single-gap re-entrant cavity with an iris is used. Qext ~ 16 wave WR975 Pillbox window ( TiN coated Al2O3) Output cavity The simulation was done using HFSS code:Model and result.

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