1
|
Stephens JC, Rosenzweig G, Shapiro MA, Temkin RJ, Tucek JC, Kreischer KE. Subterahertz Photonic Crystal Klystron Amplifier. PHYSICAL REVIEW LETTERS 2019; 123:244801. [PMID: 31922865 DOI: 10.1103/physrevlett.123.244801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 11/05/2019] [Indexed: 06/10/2023]
Abstract
This Letter reports the successful experimental demonstration of amplification of subterahertz radiation in a klystron with photonic crystal cavities. The klystron has six cavities, with each cavity having a series of oversized photonic crystal cells made up of a 5×3 array of square posts. The center post is removed from each cell to form a highly oversized (0.8 mm∼λ/4) beam tunnel, with power coupling from cell to cell through the tunnel. The pulsed electron beam is operated at 23.5 kV, 330 mA in a 0.5 T solenoidal field. At 93.7 GHz, a small-signal gain of 26 dB and a saturated output power of 30 W are obtained. Experimental results are in very good agreement with the predictions of a particle-in-cell code. The successful achievement of high gain operation of a photonic crystal klystron amplifier is promising for the future extension of klystron operation well into the terahertz frequency region.
Collapse
Affiliation(s)
- J C Stephens
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - G Rosenzweig
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - M A Shapiro
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - R J Temkin
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - J C Tucek
- Northrop Grumman Corporation, Rolling Meadows, Illinois 60008, USA
| | - K E Kreischer
- Northrop Grumman Corporation, Rolling Meadows, Illinois 60008, USA
| |
Collapse
|
2
|
Saliba EP, Barnes AB. Fast electron paramagnetic resonance magic angle spinning simulations using analytical powder averaging techniques. J Chem Phys 2019; 151:114107. [PMID: 31542017 PMCID: PMC7043854 DOI: 10.1063/1.5113598] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 08/27/2019] [Indexed: 11/14/2022] Open
Abstract
Simulations describing the spin physics underpinning nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy play an important role in the design of new experiments. When experiments are performed in the solid state, samples are commonly composed of powders or glasses, with molecules oriented at a large number of angles with respect to the laboratory frame. These powder angles must be represented in simulations to account for anisotropic interactions. Numerical techniques are typically used to accurately compute such powder averages. A large number of Euler angles are usually required, leading to lengthy simulation times. This is particularly true in broad spectra, such as those observed in EPR. The combination of the traditionally separate techniques of EPR and magic angle spinning (MAS) NMR could play an important role in future electron detected experiments, combined with dynamic nuclear polarization, which will allow for exceptional detection sensitivity of NMR spin coherences. Here, we present a method of reducing the required number of Euler angles in magnetic resonance simulations by analytically performing the powder average over one of the Euler angles in the static and MAS cases for the TEMPO nitroxide radical in a 7 T field. In the static case, this leads to a 97.5% reduction in simulation time over the fully numerical case and reproduces the expected spinning sideband manifold when simulated with a MAS frequency of 150 kHz. This technique is applicable to more traditional NMR experiments as well, such as those involving quadrupolar nuclei or multiple dimensions.
Collapse
Affiliation(s)
- Edward P Saliba
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, USA
| | - Alexander B Barnes
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, USA
| |
Collapse
|
3
|
Pan S, Du CH, Qi XB, Liu PK. Broadband terahertz-power extracting by using electron cyclotron maser. Sci Rep 2017; 7:7265. [PMID: 28779113 PMCID: PMC5544717 DOI: 10.1038/s41598-017-07545-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 06/29/2017] [Indexed: 12/02/2022] Open
Abstract
Terahertz applications urgently require high performance and room temperature terahertz sources. The gyrotron based on the principle of electron cyclotron maser is able to generate watt-to-megawatt level terahertz radiation, and becomes an exceptional role in the frontiers of energy, security and biomedicine. However, in normal conditions, a terahertz gyrotron could generate terahertz radiation with high efficiency on a single frequency or with low efficiency in a relatively narrow tuning band. Here a frequency tuning scheme for the terahertz gyrotron utilizing sequentially switching among several whispering-gallery modes is proposed to reach high performance with broadband, coherence and high power simultaneously. Such mode-switching gyrotron has the potential of generating broadband radiation with 100-GHz-level bandwidth. Even wider bandwidth is limited by the frequency-dependent effective electrical length of the cavity. Preliminary investigation applies a pre-bunched circuit to the single-mode wide-band tuning. Then, more broadband sweeping is produced by mode switching in great-range magnetic tuning. The effect of mode competition, as well as critical engineering techniques on frequency tuning is discussed to confirm the feasibility for the case close to reality. This multi-mode-switching scheme could make gyrotron a promising device towards bridging the so-called terahertz gap.
Collapse
Affiliation(s)
- Shi Pan
- School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, P. R. China
| | - Chao-Hai Du
- School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, P. R. China.
| | - Xiang-Bo Qi
- School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, P. R. China
| | - Pu-Kun Liu
- School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, P. R. China.
| |
Collapse
|
4
|
Nanni EA, Lewis SM, Shapiro MA, Griffin RG, Temkin RJ. Photonic-band-gap traveling-wave gyrotron amplifier. PHYSICAL REVIEW LETTERS 2013; 111:235101. [PMID: 24476286 PMCID: PMC4066963 DOI: 10.1103/physrevlett.111.235101] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Indexed: 05/18/2023]
Abstract
We report the experimental demonstration of a gyrotron traveling-wave-tube amplifier at 250 GHz that uses a photonic band gap (PBG) interaction circuit. The gyrotron amplifier achieved a peak small signal gain of 38 dB and 45 W output power at 247.7 GHz with an instantaneous -3 dB bandwidth of 0.4 GHz. The amplifier can be tuned for operation from 245-256 GHz. The widest instantaneous -3 dB bandwidth of 4.5 GHz centered at 253.25 GHz was observed with a gain of 24 dB. The PBG circuit provides stability from oscillations by supporting the propagation of transverse electric (TE) modes in a narrow range of frequencies, allowing for the confinement of the operating TE03-like mode while rejecting the excitation of oscillations at nearby frequencies. This experiment achieved the highest frequency of operation for a gyrotron amplifier; at present, there are no other amplifiers in this frequency range that are capable of producing either high gain or high output power. This result represents the highest gain observed above 94 GHz and the highest output power achieved above 140 GHz by any conventional-voltage vacuum electron device based amplifier.
Collapse
Affiliation(s)
- E A Nanni
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - S M Lewis
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - M A Shapiro
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - R G Griffin
- Department of Chemistry and the Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - R J Temkin
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| |
Collapse
|
5
|
He W, Donaldson CR, Zhang L, Ronald K, McElhinney P, Cross AW. High power wideband gyrotron backward wave oscillator operating towards the terahertz region. PHYSICAL REVIEW LETTERS 2013; 110:165101. [PMID: 23679610 DOI: 10.1103/physrevlett.110.165101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Indexed: 06/02/2023]
Abstract
Experimental results are presented of the first successful gyrotron backward wave oscillator (gyro-BWO) with continuous frequency tuning near the low-terahertz region. A helically corrugated interaction region was used to allow efficient interaction over a wide frequency band at the second harmonic of the electron cyclotron frequency without parasitic output. The gyro-BWO generated a maximum output power of 12 kW when driven by a 40 kV, 1.5 A, annular-shaped large-orbit electron beam and achieved a frequency tuning band of 88-102.5 GHz by adjusting the cavity magnetic field. The performance of the gyro-BWO is consistent with 3D particle-in-cell numerical simulations.
Collapse
Affiliation(s)
- W He
- Department of Physics, SUPA, University of Strathclyde, Glasgow, G4 0NG, United Kingdom
| | | | | | | | | | | |
Collapse
|
6
|
Serebryannikov AE, Magath T, Schuenemann K. Bragg transmittance of s-polarized waves through finite-thickness photonic crystals with a periodically corrugated interface. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 74:066607. [PMID: 17280162 DOI: 10.1103/physreve.74.066607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2005] [Revised: 08/11/2006] [Indexed: 05/13/2023]
Abstract
Finite-thickness photonic crystals (PC's) with periodically corrugated interfaces are suggested to realize some unusual features in the behavior of transmitted Bragg beams (diffraction orders). The scattering of s -polarized plane waves by such structures is studied. It follows from the numerical results that rather thin corrugated PC's borrow their basic properties from both conventional PC's and gratings, leading to some new effects. In particular, a shift of the actual cutoff frequencies towards larger values than those of the Rayleigh cutoff frequencies can be obtained due to the ordinary opaque range in transmission, within which all propagative orders vanish. This effect can even be enhanced due to the nonordinary behavior arising at the edges of the ordinary opaque range, which manifests itself in that some but not all propagative orders in transmission are suppressed. Hence the opaque ranges for individual orders are wider than the corresponding ordinary range. Besides, frequency ranges exist which are not connected with the edge of the ordinary opaque range, where a similar nonordinary effect does appear. As a result, each propagative order in transmission generally has its own set of opaque ranges. Only a single order can be contributive while several others are formally propagative, too. The corrugations have to be located at the upper interface in order to realize these nonordinary effects. Moving the corrugation from the upper to the lower interface leads to a disappearance of the observed effects, so that their nature cannot be explained exclusively in terms of matching the wave vectors of the diffraction orders and the Floquet-Bloch waves. The conventional sequence of cutoffs for different diffraction orders with respect to each other can be changed for certain structures if the rods of a PC are made of Drude metal. Hence, transmission regimes can be realized which are beyond the classical theory of gratings. Several effects arising when varying the angle of incidence are demonstrated and briefly discussed. The detected effects can be used for controlling the number of actually contributive beams and for obtaining alternating ranges of single-beam and multibeam operation, which should lead to extending the potentials of optical and microwave technologies based on the use of single-beam and multibeam regimes.
Collapse
Affiliation(s)
- A E Serebryannikov
- Institut fuer Hochfrequenztechnik, Technische Universitaet Hamburg-Harburg, D-21071 Hamburg, Germany.
| | | | | |
Collapse
|
7
|
Shapiro MA, Shvets G, Sirigiri JR, Temkin RJ. Spatial dispersion in metamaterials with negative dielectric permittivity and its effect on surface waves. OPTICS LETTERS 2006; 31:2051-3. [PMID: 16770429 DOI: 10.1364/ol.31.002051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The effect of spatial dispersion on the electromagnetic properties of a metamaterial consisting of a three-dimensional mesh of crossing metallic wires is reported. The effective dielectric permittivity tensor epsilon(ij)(omega, k) of the wire mesh is calculated in the limit of small wavenumbers. The procedure for extracting the spatial dispersion from the omega versus k dependence for electromagnetic waves propagating in the bulk of the metamaterial is developed. These propagating modes are identified as similar to the longitudinal (plasmon) and transverse (photon) waves in a plasma. Spatial dispersion is found to have the most dramatic effect on the surface waves that exist at the wire mesh-vacuum interface.
Collapse
Affiliation(s)
- M A Shapiro
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
| | | | | | | |
Collapse
|