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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
Peter Moller Vacuum Electronic Devices May 21, 2015 2 / 24
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 3 / 24
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
Peter Moller Vacuum Electronic Devices May 21, 2015 4 / 24
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
Peter Moller Vacuum Electronic Devices May 21, 2015 6 / 24
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
Peter Moller Vacuum Electronic Devices May 21, 2015 14 / 24
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]
Peter Moller Vacuum Electronic Devices May 21, 2015 15 / 24
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 17 / 24
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
Peter Moller Vacuum Electronic Devices May 21, 2015 18 / 24
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).
Peter Moller Vacuum Electronic Devices May 21, 2015 23 / 24
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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