Vacuum Electronic Devices

Peter Moller

May 21, 2015

Peter Moller Vacuum Electronic Devices May 21, 2015 1 / 24

Outline

1 OverviewOverviewHistory

2 DevicesMagnetronTraveling Wave Tube - TWTBackward wave oscillator - BWOKlystronInductive output tubes - IOTGyrotronLow frequency tubes

3 Future

4 Selected paper 1

5 Selected paper 2

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Outline

1 OverviewOverviewHistory

2 DevicesMagnetronTraveling Wave Tube - TWTBackward wave oscillator -BWO

KlystronInductive output tubes - IOTGyrotronLow frequency tubes

3 Future

4 Selected paper 1

5 Selected paper 2

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Overview

Vacuum electronic devices produce coherent electromagneticradiation through the interaction of an electron beam with anelectromagnetic structure

Applications includeI RadarI Communications (terrestrial and space)I FusionI Industrial processingI MedicineI Microwave ovens

Multidisciplinary field. Advances driven by innovations inelectromagnetic design and beam-wave interaction structures, as wellas thermal management, new materials, fabrication andcomputational techniques

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History

Many of the devices were invented during or just after World War II

These were all Slow Wave devices

During the 1950 civil applications were developed

All these devices have been further developed to provide higher powerand frequency, greater efficiency and reduced size

Hybrid vacuum/solid state microwave power module (MPM), wasrecently developed [1]

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Outline

1 OverviewOverviewHistory

2 DevicesMagnetronTraveling Wave Tube - TWTBackward wave oscillator -BWO

KlystronInductive output tubes - IOTGyrotronLow frequency tubes

3 Future

4 Selected paper 1

5 Selected paper 2

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Magnetron

Cheap

Frequency drift

Used in civil radars,microwave ovens

Pulsed or continuousoperation

<1GHz to 120GHz,5MW/4kW peak/avgpower

Figure : Magnetron cross section [2] [3]

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Traveling Wave Tube - TWT

Wide bandwidth

Reliable

Used in militaryradars, spacecommunications

Efficiency (>73%)

Max frequency50-100GHz

Figure : Cross section, beam propagation [4] [5]

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Backward wave oscillator - BWO

Similar to TWT, but noRF in

Two types, M and O

Voltage controlledfrequency

M-type, high outputpower, O-type <1W

O-type have very lownoise Figure : M-BWO [6]

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Klystron

Fixed frequency

Two cavities -Input/bouncer andOutput/catcher

More catchers increaseefficiency ->EIK

TV transmitters, radar,satellite

75 MW output (pulsed)

Up to 280GHz

Reliable

Figure : Cross section [7]

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Inductive output tubes - IOT

Invented 1938

Widely used since 1980 -replaced Klystrons

30 kW continuous power

Efficiency 60% with 8VSB

Figure : IOT [8] [9]

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Gyrotron

Gyro device - FWS -bremsstrahlung

1GHz to 1THz

Heaters for fusion reactors

Also for industrial,medical and warfare

Figure : Iter gyrotron [10] [11]

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Audio / Music applicationsOne field where vacuum tubes is superior to solid state is in guitaramplifiers. An amplifier built to distort benefits from the more pleasantovertones of tubes.

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Outline

1 OverviewOverviewHistory

2 DevicesMagnetronTraveling Wave Tube - TWTBackward wave oscillator -BWO

KlystronInductive output tubes - IOTGyrotronLow frequency tubes

3 Future

4 Selected paper 1

5 Selected paper 2

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Future

1 Terahertz gap needs to be filled

2 Normal linear SWS will have difficulties reaching higher frequencies

3 Novel materials, meta materials

4 Free electron Laser (FEL) promise high power at millimeter to X-raywavelengths [1]

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Future

Figure : The Terahertz gap [12]

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Outline

1 OverviewOverviewHistory

2 DevicesMagnetronTraveling Wave Tube - TWTBackward wave oscillator -BWO

KlystronInductive output tubes - IOTGyrotronLow frequency tubes

3 Future

4 Selected paper 1

5 Selected paper 2

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Selected paper 1 - The vacuum transistor [12]

VDS = 10V

Mean Free Path inair is too short

First attemptmanaged 460GHz

Compatible withCMOS fabrication

Design of the tipscrucial

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Outline

1 OverviewOverviewHistory

2 DevicesMagnetronTraveling Wave Tube - TWTBackward wave oscillator -BWO

KlystronInductive output tubes - IOTGyrotronLow frequency tubes

3 Future

4 Selected paper 1

5 Selected paper 2

Peter Moller Vacuum Electronic Devices May 21, 2015 19 / 24

Selected paper 2 - Metamaterial-Enhanced Traveling WaveTubes [13]

High frequency VED structures is hampered by the challenges of highprecision three-dimensional machining required for shorterwavelengths, and also by limits in maximum beam dimensions andcurrent

By using electromagnetic metamaterials (MTMs) some of thesechallenges can be addressed

This paper demostrates that when a SWS is loaded with epsilonnegative metamaterial (ENG) slabs periodically, it’s band diagram isshifted to higher frequencies

A metamaterial is a material engineered to have properties not yetfound in nature. Often arranged in a repeating pattern, atmicroscopic or smaller scale that are less than the wavelengths of thephenomena they influence

This specific metamaterial (ENG) have negative εr and positive µr

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Result

f0 = 48GHz for theunloaded unit cell

Cutoff fc = f0/1.25

Wideband withoutENG

Narrowband withENG

ENG dispersivepermittivity:εr = ε∞ − (fp/f )

2,with fp=281.6GHz

Physical dimensions35% larger, sohigher beamcurrent is possible

Figure : Unit cell of ENG loaded TWT

Figure : Phase velocities

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References I

[1] V.L. Granatstein and C.M. Armstrong. “Special issue on new vistasfor vacuum electronics [Guest Editorial]”. In: Proceedings of theIEEE 87.5 (May 1999), pp. 699–701. issn: 0018-9219. doi:10.1109/JPROC.1999.757250.

[2] Magnetron cross section. Apr. 24, 2015. url:http://hyperphysics.phy-

astr.gsu.edu/hbase/waves/imgwav/magnetronop.gif.

[3] Radar basics - Magnetorn. Apr. 24, 2015. url: http://www.radartutorial.eu/08.transmitters/Magnetron.en.html

(visited on 05/21/2015).

[4] TWT cross section. 2015. url: http://www.pendel.com/images/technology/crosssection.jpg.

[5] The Traveling wave tube. In: 2015. url: http://electriciantraining.tpub.com/14183/css/14183_101.htm.

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References II[6] Backward-wave oscillator. In: Wikipedia, the free encyclopedia.

Page Version ID: 658952539. Apr. 24, 2015. url:http://en.wikipedia.org/w/index.php?title=Backward-

wave_oscillator&oldid=658952539 (visited on 05/21/2015).

[7] Emilio Ciardiello. Klystrons. Jan. 22, 2010. url: http://www.radiomuseum.org/forum/vm_tubes_3_klystrons.html.

[8] IOT replacement. 2015. url: http://www.cybermike.net/reference/liec_book/Semi/03173.jpg.

[9] Inductive Output Tube. 2015. url:http://www.avsforum.com/photopost/data/2118934/0/0c/

0c1c2810_L3TubeRemove3.jpeg.

[10] ITER Gyrotron. ITER. 2013. url:http://www.iter.org/newsline/105/1453 (visited on05/21/2015).

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References III[11] JAEA. Gyrotron. 2015. url:

http://www.toshiba-tetd.co.jp/eng/tech/gyrotron.htm.

[12] Meyya Meyyappan and Jin-Woo Han. Introducing the VacuumTransistor: A Device Made of Nothing. June 23, 2014. url:http://spectrum.ieee.org/semiconductors/devices/

introducing-the-vacuum-transistor-a-device-made-of-

nothing (visited on 05/21/2015).

[13] A. Rashidi and N. Behdad. “Metamaterial-enhanced traveling wavetubes”. In: Vacuum Electronics Conference, IEEE International.Vacuum Electronics Conference, IEEE International. Apr. 2014,pp. 199–200. doi: 10.1109/IVEC.2014.6857559.

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