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. 2006 Jun;34(3):518-523.
doi: 10.1109/TPS.2006.875776.

Operational Characteristics of a 14-W 140-GHz Gyrotron for Dynamic Nuclear Polarization

Colin D Joye  1 , Robert G Griffin, Melissa K Hornstein, Kan-Nian Hu, Kenneth E Kreischer, Melanie Rosay, Michael A Shapiro, Jagadishwar R Sirigiri, Richard J Temkin, Paul P Woskov
Affiliations

Operational Characteristics of a 14-W 140-GHz Gyrotron for Dynamic Nuclear Polarization

Colin D Joye et al. IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc. 2006 Jun.

Abstract

The operating characteristics of a 140-GHz 14-W long pulse gyrotron are presented. The device is being used in dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP/NMR) spectroscopy experiments. The gyrotron yields 14 W peak power at 139.65 GHz from the TE(0,3) operating mode using a 12.3-kV 25-mA electron beam. Additionally, up to 12 W peak has been observed in the TE(2,3) mode at 136.90 GHz. A series of mode converters transform the TE(0,3) operating mode to the TE(1,1) mode. Experimental results are compared with nonlinear simulations and show reasonable agreement. The millimeter-wave output beam was imaged in a single shot using a pyroelectric camera. The mode patterns matched reasonably well to theory for both the TE(0,1) mode and the TE(1,1) mode. Repeatable mode patterns were obtained at intervals ranging from 0.8 s apart to 11 min apart at the output of the final mode converter.

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Figures

Fig. 1
Fig. 1
Gyrotron block diagram showing the electron gun (MIG), main magnet, cavity, collector, internal mode converters, and quartz window.
Fig. 2
Fig. 2
Diagram of the current electron gun showing the location of the pumping slots and vacuum pump.
Fig. 3
Fig. 3
Schematic of the resonator showing (a) the downtaper, (b) cavity straight section, and (c) uptaper section along with (d) the simulated electric field profile of the TE031 mode in arbitrary units.
Fig. 4
Fig. 4
Mode map for the 140-GHz gyrotron. Heavy circles indicate the location of highest observed power in each mode.
Fig. 5
Fig. 5
Power output for the TE031 mode versus main magnetic field comparing the measurement to simulation.
Fig. 6
Fig. 6
(a) Measured gyrotron output. (b) Theoretical TE01 mode. (c) Measured final mode converter output. (d) Theoretical TE11 mode. Scale is normalized linear power.
Fig. 7
Fig. 7
Mode measurements at the output of the final mode converter (a)–(b) 0.8 s apart and (c)–(d) 11 min apart. Scale is normalized linear power.
See this image and copyright information in PMC

References

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