Photonic-Band-Gap Traveling-Wave Gyrotron Amplifier

Nanni, Emilio A.; Lewis, Samantha M.; Shapiro, Michael A.; Griffin, Robert G.; Temkin, Richard J.

doi:10.1103/physrevlett.111.235101

Cited by 108 publications

(57 citation statements)

References 33 publications

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“…We predict that at magnetic fields of 0.5 T and above, NOVEL DNP would surpass the SE. With the recent advances in the gyroamplifier technology, [54][55][56] we anticipate that pulsed DNP will become available at high magnetic fields in the near future. Furthermore, current applications of CW DNP in NMR require operation at cryogenic temperatures, which imposes limitations in many cases.…”

Section: Discussionmentioning

confidence: 99%

Time domain DNP with the NOVEL sequence

Can

Walish

Swager

et al. 2015

The Journal of Chemical Physics

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We present results of a pulsed dynamic nuclear polarization (DNP) study at 0.35 T (9.7 GHz/ 14.7 MHz for electron/ 1 H Larmor frequency) using a lab frame-rotating frame cross polarization experiment that employs electron spin locking fields that match the 1 H nuclear Larmor frequency, the so called NOVEL (nuclear orientation via electron spin locking) condition. We apply the method to a series of DNP samples including a single crystal of diphenyl nitroxide (DPNO) doped benzophenone (BzP), 1,3-bisdiphenylene-2-phenylallyl (BDPA) doped polystyrene (PS), and sulfonated-BDPA (SA-BDPA) doped glycerol/water glassy matrices. The optimal Hartman-Hahn matching condition is achieved when the nutation frequency of the electron matches the Larmor frequency of the proton, ω 1S = ω 0I , together with possible higher order matching conditions at lower efficiencies. The magnetization transfer from electron to protons occurs on the time scale of ∼100 ns, consistent with the electron-proton couplings on the order of 1-10 MHz in these samples. In a fully protonated single crystal DPNO/BzP, at 270 K, we obtained a maximum signal enhancement of ε = 165 and the corresponding gain in sensitivity of ε(T 1 /T B ) 1/2 = 230 due to the reduction in the buildup time under DNP. In a sample of partially deuterated PS doped with BDPA, we obtained an enhancement of 323 which is a factor of ∼3.2 higher compared to the protonated version of the same sample and accounts for 49% of the theoretical limit. For the SA-BDPA doped glycerol/water glassy matrix at 80 K, the sample condition used in most applications of DNP in nuclear magnetic resonance, we also observed a significant enhancement. Our findings demonstrate that pulsed DNP via the NOVEL sequence is highly efficient and can potentially surpass continuous wave DNP mechanisms such as the solid effect and cross effect which scale unfavorably with increasing magnetic field. Furthermore, pulsed DNP is also a promising avenue for DNP at high temperature. C 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4927087] INTRODUCTIONDynamic nuclear polarization (DNP) is a process whereby the large polarization present in an electron spin reservoir of a paramagnetic polarizing agent is transferred via microwave irradiation to nuclei, thereby enhancing the nuclear spin polarization. The initial mechanism supporting the DNP process, the Overhauser effect (OE), was proposed in 1953 1 and confirmed experimentally 2,3 in samples with mobile electrons (i.e., metals, solutions, and 1D conductors). In contrast, in insulating solids, such as glycerol/water glasses and biological samples, the OE was thought to be forbidden, but we have recently observed Overhauser enhancements using polarizing agents with narrow EPR spectra that exhibit strong 1 H−e − hyperfine couplings. 4 Furthermore, in these sorts of samples, DNP processes can also be mediated by three other mechanisms -the solid effect (SE), 5,6 the cross effect, 7-11 and/or thermal mixing. 12 Initially, the primary application of DNP was preparation of p...

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Section: Discussionmentioning

confidence: 99%

Time domain DNP with the NOVEL sequence

Can

Walish

Swager

et al. 2015

The Journal of Chemical Physics

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“…Figure 6c shows simulation results of a PBG structure with single mode confinement, adapted from Ref. 11. This would open the possibility of very long structures, free from mode crossings with the forest of intruder TE modes generally associated with high aspect ratio cavities.…”

Section: Randd and Future Directionsmentioning

confidence: 99%

“…This would open the possibility of very long structures, free from mode crossings with the forest of intruder TE modes generally associated with high aspect ratio cavities. This work builds upon a long R&D and experience base in the linear accelerator and microwave tube community 11,12 , where one of us (SML) comes from. Another focus of the program is the development of cavities of much higher quality factor Q to boost the axion-photon conversion power, including cavities of multilayer Type-II superconducting thin films.…”

Section: Randd and Future Directionsmentioning

confidence: 99%

Progress in the microwave cavity search for dark matter axions

Lewis¹,

Bibber²

2017

The Fourteenth Marcel Grossmann Meeting

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Very light axions represent an excellent dark matter candidate, and may be detected by their resonant conversion to photons in a microwave cavity within a strong magnetic field. Current experiments are commencing searches for cosmic axions in the 1-100 μeV range constituting our galactic halo. The sensitivity of these experiments largely results from the development of quantum-limited amplifiers, such as SQUIDs and Josephson Parametric Amplifiers; future experiments may achieve even greater sensitivity by evading the standard quantum limit on noise temperature altogether.

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“…The experiment achieved the highest operation frequency for a gyrotron amplifier. And it is the first amplifier that is capable of producing either high gain or high output power at such high frequency range [3]. …”

Section: Introductionmentioning

confidence: 99%

“…This led to new applications in passive devices for guiding and confining the electromagnetic radiation [3][4][5][6][7][8][9][10][11][12]. A PBG cavity operating at a TE 041 The design of the PGB structures requires an accurate prediction of the global photonic band gaps, which is still challenging and time consuming.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Photonic Bandgaps for Gyrotron Devices

Zhang

Shen

Zhang

et al. 2015

IEEE Trans. Plasma Sci.

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This version is available at https://strathprints.strath.ac.uk/52809/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output.1 Abstract -The global band gaps of the photonic crystal is theoretical analyzed in this paper. The electromagnetic wave propagation characteristics of the photonic band gap (PBG) structures, which are interested in the millimeter wave, sub-millimeter wave, and terahertz regime vacuum electronic devices and accelerators, were numerically simulated by using the finite-element method software HFSS. The dispersion curves of the lattices in different ratios of the rod radius to the rod spacing, and the global band gaps for the general two-dimensional PBG structures formed by triangular and square arrays of metal rods were simulated. A mode map which shows the relationship between the structures and the contained modes was plotted and a 220 GHz metallic PBG resonator operates at TE 04 mode was designed for a gyrotron device to verify the theoretical and numerical simulations, and the comparison of the mode density and the quality factor between the PBG resonator and the equivalent cylindrical resonator have been analyzed.

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Photonic-Band-Gap Traveling-Wave Gyrotron Amplifier

Cited by 108 publications

References 33 publications

Time domain DNP with the NOVEL sequence

Time domain DNP with the NOVEL sequence

Progress in the microwave cavity search for dark matter axions

Analysis of the Photonic Bandgaps for Gyrotron Devices

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