Gyrotron FU CW VII for 300 MHz and 600 MHz DNP-NMR Spectroscopy

Fujii

et al. 2012

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A dynamic nuclear polarization (DNP)-enhanced cross-polarization/magic-angle spinning (DNP/CP/MAS) NMR system has been developed by combining a 200 MHz Chemagnetics CMX-200 spectrometer operating at 4.7 T with a high-power 131.5 GHz Gyrotron FU CW IV. The 30 W sub-THz wave generated in a long pulse TE ð1Þ 41 mode with a frequency of 5 Hz was successfully transmitted to the modified Doty Scientific lowtemperature CP/MAS probe through copper smooth-wall circular waveguides. Since serious RF noises on NMR signals by arcing in the electric circuit of the probe and undesired sample heating were induced by the continuous sub-THz wave pulse irradiation with higher powers, the on-off sub-THz wave pulse irradiation synchronized with the NMR detection was developed and the appropriate setting of the irradiation time and the cooling time corresponding to the non-irradiation time was found to be very effective for the suppression of the arcing and the sample heating. The attainable maximum DNP enhancement was more than 30 folds for C1 13 C-enriched D-glucose dissolved in the frozen medium containing mono-radical 4-amino-TEMPO. The first DNP/CP/MAS 13 C NMR spectra of poly(methyl methacrylate) (PMMA) sub-micron particles were obtained at the dispersed state in the same frozen medium, indicating that DNP-enhanced 1 H spins effectively diffuse from the medium to the PMMA particles through their surface and are detected as high-resolution 13 C spectra in the surficial region to which the 1 H spins reach. On the basis of these results, the possibility of the DNP/CP/MAS NMR characterization of the surface structure of nanomaterials including polymer materials was discussed.

Section: Introductionmentioning

confidence: 99%

Development of DNP-Enhanced High-Resolution Solid-State NMR System for the Characterization of the Surface Structure of Polymer Materials

Horii

Fujii

et al. 2012

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“…11) is also designed as a sub-THz radiation source for DNP-NMR spectroscopy but can be used for studying of both 300 MHz and 600 MHz proton spectra since it operates at frequencies around 200 GHz in a fundamental operation and around 400 GHz at the second harmonic [39]. Its demountable tube has a turbo- for the fundamental operation and several tens of watts for the second harmonic.…”

Section: Gyrotron Fu Cw VIImentioning

confidence: 99%

“…More important, however, is the stabilization of the output power for long periods of time. Typically the variation ΔP/P is less than 5% (provided that there are no big fluctuations of the line voltage) [39], which is in principle acceptable. It can be increased further by stabilizing the power supply and by a dedicated feed-back control of the electron beam parameters.…”

Section: Gyrotron Fu Cw VIImentioning

confidence: 99%

Development and Applications of High—Frequency Gyrotrons in FIR FU Covering the sub-THz to THz Range

Sabchevski

2012

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Powerful sources of coherent radiation in the sub-terahertz and in the terahertz frequency range of the electromagnetic spectrum are necessary for a great and continuously expanding number of applications in the physical research and in various advanced technological processes as well as in radars, communication systems, for remote sensing and inspection etc.. In recent years, a spectacular progress in the development of various gyrodevices and in particular of the powerful high frequency (sub-terahertz and terahertz) gyrotron oscillators has demonstrated a remarkable potential for bridging the so-called terahertz power gap and stimulated many novel and prospective applications. In this review paper we outline two series of such devices, namely the Gyrotron FU Series which includes pulsed gyrotrons and Gyrotron FU CW Series which consist of tubes operated in a CW (continuous wave) or long pulse mode, both developed at the FIR FU Center. We present the most remarkable achievements of these devices and illustrate their applications by some characteristic examples. An outlook for the further extension of the Gyrotron FU CW Series is also provided.

“…In FIR FU, a lot of high-frequency gyrotrons have been developed as sources in the millimeter and sub-millimeter wave range, which are applicable to various fields such as electron spin resonance (ESR), dynamic nuclear polarization (DNP)-nuclear magnetic resonance (NMR) spectroscopy and accurate measurements of hyperfine split of positronium [1][2][3][4][5][6][7][8]. The gyrotrons developed in FIR FU, FU series and FU CW series, are all linear type with axial output coupling, except Gyrotron FU CW I which was designed and constructed at IAP, RAS and Gycom [9].…”

Section: Introductionmentioning

confidence: 99%

Development of a kW Level-200 GHz Gyrotron FU CW GI with an Internal Quasi-optical Mode Convertor

Tatematsu

Yamaguchi

et al. 2012

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Development of gyrotrons with an internal mode convertor has started in Research Center for Development of Far-Infrared Region, University of Fukui (FIR FU). As the first gyrotron of such a kind, we have designed and manufactured Gyrotron FU CW GI. It operates at 203 GHz at fundamental cyclotron resonance. We have designed a cavity and a mode convertor under some constraints such as reuse of an electron gun and small diameter of a magnet bore. Designed output power is about 1 kW. We have succeeded in observation of a circular radiation pattern. The maximum observed output power is 0.5 kW for the setting cathode voltage of 20 kV and the beam current of 0.5 A. This success makes gyrotron development in FIR FU to proceed to a new stage.