Operational Characteristics of a 14-W 140-GHz Gyrotron for Dynamic Nuclear Polarization |
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| Authors: | Joye Colin D Griffin Robert G Hornstein Melissa K Hu Kan-Nian Kreischer Kenneth E Rosay Melanie Shapiro Michael A Sirigiri Jagadishwar R Temkin Richard J Woskov Paul P |
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| Institution: | Student Member, IEEE, The Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 USA (e-mail: cjoye@mit.edu ). |
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| 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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