Vacuum electronics for the 21st century

Abrams, R.H.; Levush, B.; Mondelli, A.; Parker, Robert K.

doi:10.1109/6668.951550

Cited by 76 publications

(18 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[93][94][95] In general, two different types of μw sources can be distinguished: solid-state and vacuum electronic devices. Figure 10 provides an overview of high-frequency μw sources available currently.…”

Section: A Microwave Sourcesmentioning

confidence: 99%

Dynamic nuclear polarization at high magnetic fields

Maly¹,

Debelouchina²,

Bajaj³

et al. 2008

The Journal of Chemical Physics

791

847

View full text Add to dashboard Cite

Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (μw) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (γ e /γ l ), being ∼660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (≥5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms-the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in μw and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments.

show abstract

Section: A Microwave Sourcesmentioning

confidence: 99%

Dynamic nuclear polarization at high magnetic fields

Maly¹,

Debelouchina²,

Bajaj³

et al. 2008

The Journal of Chemical Physics

791

847

View full text Add to dashboard Cite

show abstract

“…1.2, ranging from commercial communication to fusion heating. Well-known modern types of tubes are the magnetron, the klystron, the gyrotron, the traveling wave tube (TWT), phototubes, and flourescent lamps [1], [2], [3].…”

mentioning

confidence: 99%

“…Historically, the first generation of vacuum amplifiers were designed to operate cations to fusion heating [2] with three metal electrodes: two at the different ends of a tube to generate and collect the electron beams, one in the middle to provide control mechanism. The tube can be vacuum or gas-filled.…”

mentioning

confidence: 99%

“…At the same time, an electric wave is generated, which couples with the electron beam inside the tube, providing an amplifying mechanism. Fundamentally, the beam-wave interaction works as a conversion of spontaneous electromagnetic radiation to coherent radiation, which requires both synchronism condition and a condition for electron bunching [2].…”

mentioning

confidence: 99%

“…1.3 [5]. Much research is being done to improve the performance of vacuum devices, each targeting specific component of the tube, such as designing better electrons emission and/or collection, attempting different fields manipulation techniques, and investigating beam-wave coupling [2]. Recent advances in computer simulation power and hardware fabrication techniques further drive the field of vacuum electronics forward, prompting new designs and novel concepts [3].…”

mentioning

confidence: 99%

See 2 more Smart Citations

Planar Slow-Wave Structure With Parasitic Mode Control

Nguyen

Antonsen

Nusinovich

2014

IEEE Trans. Electron Devices

View full text Add to dashboard Cite

Modern vacuum tube devices dominate the field of high power and high frequency electronics. Among them, the Traveling Wave Tube Amplifier (TWTA) has broad bandwidth and consequently a wide range of applications. In this thesis, a planar sheath-like slow wave structure with rectangular geometry is studied and considered for use in a TWTA driven by a sheet electron beam. Although use of a wide sheet beam promises high power, the large transverse dimension of the structure risks interaction of the beam with multiple backward wave modes. Both the operating mode and the parasitic modes are analyzed using field theories with the planar sheath approximation. These solutions are then compared with finite element computations. Suppression of backward waves is then considered by designing the structure to preferentially absorb these waves. The results show good control of mode competition and high primary mode gain.

show abstract

Local Multipoint Distribution Services (LMDS)

Papazian

Dalke

2003

Wiley Encyclopedia of Telecommunications

View full text Add to dashboard Cite

This article describes Local Multipoint Distribution Services (LMDS), a broadband wireless access service. The band allocation and regulations established by the Federal Communications Commission (FCC) are summarized, included the millimeter wave spectrum allocation for LMDS and interference and frequency coordination issues. Advantages and disadvantages of the millimeter wave band for broadband data transmission are presented. Propagation impairments due to rain and atmospheric attenuation are discussed analytically using current models. Measured data are used to predict area coverage, depolarization and attenuation due to vegetation, and multipath effects for the broadcast mode of transmission.

show abstract

Vacuum electronics for the 21st century

Cited by 76 publications

References 24 publications

Dynamic nuclear polarization at high magnetic fields

Dynamic nuclear polarization at high magnetic fields

Planar Slow-Wave Structure With Parasitic Mode Control

Local Multipoint Distribution Services (LMDS)

Contact Info

Product

Resources

About