Richard J. Temkin

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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,(More)
Dynamic Nuclear Polarization (DNP) experiments transfer polarization from electron spins to nuclear spins with microwave irradiation of the electron spins for enhanced sensitivity in nuclear magnetic resonance (NMR) spectroscopy. Design and testing of a spectrometer for magic angle spinning (MAS) DNP experiments at 263 GHz microwave frequency, 400 MHz (1)H(More)
During the three decades 1980-2010, magic angle spinning (MAS) NMR developed into the method of choice to examine many chemical, physical, and biological problems. In particular, a variety of dipolar recoupling methods to measure distances and torsion angles can now constrain molecular structures to high resolution. However, applications are often limited(More)
We describe a cryogenic sample exchange system that dramatically improves the efficiency of magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments by reducing the time required to change samples and by improving long-term instrument stability. Changing samples in conventional cryogenic MAS DNP/NMR experiments involves warming the probe to(More)
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(More)
We present the design and experimental results of a novel quasioptical gyrotron traveling-wave tube (gyro-TWT) amplifier at 140 GHz. The gyro-TWT produced up to 30 kW of peak power in 2 micros pulsed operation at 6 Hz achieving a peak gain of 29 dB, a peak efficiency of 12%, and a bandwidth of 2.3 GHz. The device was operated in a very higher-order mode of(More)
We present the formulation and experimental results of a new approach to designing internal mode converter reflectors for high-power gyrotrons. The method employs a numerical phase retrieval algorithm that reconstructs the field in the mode converter from intensity measurements, thus accounting for the true field structure in shaping the beam-forming(More)
We report the first operation of a 17 GHz RF photocathode electron gun. This is the first photocathode electron gun to operate at a frequency above 2.856 GHz. Such electron guns have the potential for achieving record high values of electron beam quality. The 1 2 cell, π -mode, copper cavity was tested with 5-10 MW, 100 ns, 17.145 GHz pulses from a 24 MW(More)
In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9T, corresponding to 380 MHz (1)H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine(More)
We report the regulated continuous-wave (CW) operation of a second harmonic gyrotron oscillator at output power levels of over 8 W (12.4 kV and 135 mA beam voltage and current) in the TE(0,6,1) mode near 460 GHz. The gyrotron also operates in the second harmonic TE(2,6,1) mode at 456 GHz and in the TE(2,3,1) fundamental mode at 233 GHz. CW operation was(More)