Second Harmonic Operation at Four Hundred Sixty 460 Gigahertz and Broadband Continuous Frequency Tuning of a Gyrotron Oscillator

Download or read book Second Harmonic Operation at Four Hundred Sixty 460 Gigahertz and Broadband Continuous Frequency Tuning of a Gyrotron Oscillator written by Melissa Kristen Hornstein and published by . This book was released on 2004 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report the short pulse operation of a 460 GHz gyrotron oscillator both at the fundamental (near 230 GHz) and second harmonic (near 460 GHz) of electron cyclotron resonance. During operation in a microsecond pulse length regime with 13 kV beam voltage and 110 mA beam current, the instrument generates several watts of power in two second harmonic modes, the TE2,6,1 at 456.15 GHz and the TE0,6,1 at 458.56 GHz. Operation in the fundamental modes, including the TE0,3,1 mode at 237.91 GHz and the TE2,3,1 at 233.15 GHz, is observed at output powers up to 70 W. Further, we demonstrate broadband continuous frequency tuning of the fundamental modes of the oscillator over a range of more than 2 GHz through variation of the magnetic field alone. We interpret these results in terms of smooth transitions between higher order axial modes of the resonator. The 460 GHz gyrotron is currently being processed for continuous duty operation, where it will serve as a microwave source for sensitivity-enhanced nuclear magnetic resonance (dynamic nuclear polarization) studies at 16 T (700 MHz 1H), a field strength which is two-fold higher than has been accessible with previous technology. Index Terms: Gyrotron, submillimeter, harmonic, frequency tuning, dynamic nuclear polarization, nuclear magnetic resonance.