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