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X Band Workshop - Components & Subsystems
Dat
e du
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Klystron development in X bandSébastien [email protected] R&D Thales Electron Devices
X Band Workshop - Components & Subsystems2
Thales Components & Subsystems
Medical radiologyRadiography, radiologyAngiography, urologyDental 3D imagingVet exams
Traveling Wave TubesAmplifiersPower Grid TubesAssociated sub-systems
Digital flat detectorsX-Ray Imaging UnitsX-Ray Image IntensifiersCCD camerasAssociated sub-systems
Traveling Wave TubesTransmittersKlystronsCFAsAssociated sub-systems
KlystronsGyrotronsDiacrodesAssociated sub-systems
Power grid tubesX-Ray TubesX-Ray detectorsAssociated sub-systems
IndustrialNDT-SecurityLaserIndustrial heatingSterilization
Subsystems and products
ApplicationsSpaceTelecomBroadcastEarth observationNavigation….
DefenseRadarsCountermeasuresMissiles
ScienceFusionLight SourcesLarge accelerators
X Band Workshop - Components & Subsystems3
From Components to Subsystems - Science
Energy storage Mega Joule Laser
Klystrons, gyrotrons, IOTs & tetrodes RF amplifier
X Band Workshop - Components & Subsystems4
Outline
Klystron technology for X band
A single beam 9.3 GHz / 4 MW Klystron
Alternative technologies PPM focusing Multi-Beam Klystron
X Band Workshop - Components & Subsystems5
X band klystron
Klystron source for medical and industrial applications
X Band Workshop - Components & Subsystems6
The klystron, a high-gain amplifier
Klystron is a high-power, high-gain amplifier providing :
More peak power than magnetrons
Stability of output power
Reliability : theoretical long lifetime even at high frequencies
Output power versatility
preamplifierKlystronamplifier
Isolator/circulator
Signal from 9.3 GHz oscillator
Input ~10 W Output ~ MW
Solid-state device
X Band Workshop - Components & Subsystems7
X band for industrial and medical applications
… but in field of industrial and medical applications, some others parameters have strong importance :
Compactness of the source as a whole : klystron + (oil tank) + HV modulator
Availability of passive components
Power consumption
Cost
HV modulatorOil tank
Focalisation
Power transmissionLinac
Klystron
X Band Workshop - Components & Subsystems8
X band klystron
Single beam 4 MW Klystron
Electromagnet focusing
X Band Workshop - Components & Subsystems9
9.3 GHz Klystron
RF source characteristics
Frequency (f) 9.3 GHz
Pulsed output power 4.0 MW
Average output power 4 kW
RF pulse duration 5 µs
Pulse repetition rate 200 Hz
Duty cycle 0.001
-1 dB bandwidth >30 MHz
Perveance (K) 1.0 µA / V1,5
Efficiency 49 %
Expected lifetime > 30 000 hours
Operating conditions
Cathode voltage (V) 152 kV
Cathode current (I) 60 A
X ray shielding integrated
X Band Workshop - Components & Subsystems10
Interaction structure
Simulation of klystron operation : electron beam interaction with cavities’ RF fieldanimation period = 1 / (9.3 GHz)
RF in RF out
Axi
al e
lect
ron
velo
city
6 cavities including 1 harmonic Interaction length (cavity 1 to 6) = 270 mm Output cavity carefully shaped to reduce electric field below 60 MV/m (at the
expense of coupling factor…)
X Band Workshop - Components & Subsystems11
Power transfer curve
Calculation result at nominal cathode voltage :(V=152 kV)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 10 20 30 40 50 60 70
Input power (W)
Ou
tpu
t p
ow
er (
MW
)
152 kV nominal voltage
140 kV
130 kV
120 kV
• saturation gain = 51.5 dB• Output power = 4.3 MW• Efficiency = 49 %
X Band Workshop - Components & Subsystems12
Bandwidth at saturation
Thales 9.3 GHz Klystron
46.5
47.0
47.5
48.0
48.5
49.0
49.5
50.0
50.5
51.0
51.5
52.0
9.26 9.27 9.28 9.29 9.30 9.31 9.32 9.33 9.34 9.35 9.36 9.37
Frequency (GHz)
Gai
n (
dB
)
Calculated bandwidth at –1 dB : 60 MHz (at nominal cathode voltage)
Wide instantaneous bandwidth compared to magnetron
X Band Workshop - Components & Subsystems13
The challenges of X band for standard klystron
Calculation of window’s temperature
RF electric field in output cavity Directly limits the pulsed output power
Power loss in output window Directly limits the average output power
X Band Workshop - Components & Subsystems14
Klystron & electromagnet interfaces
Output waveguide WR112 flange SF6 pressurization (3 bars)
Water coolingTotal flow ~ 26 L / min
ElectromagnetPower consumption ~ 4 kW
Electron gun power supply 152 kV / 60 A / 9.2 kW modulator Oil tank insulation Heater voltage 15 V , current 13 A
Input driver Input power = 30 W at saturation
X Band Workshop - Components & Subsystems15
Footprint and weight
Klystron Height = 0,9 m Weight ~ 60 kg Output flange at 400 mm from axis
Electromagnet Outer diameter = 500 mm Weight ~ 350 kg
X Band Workshop - Components & Subsystems16
Scaling of klystron length
L(gun) = 30 cm
L(interaction) = 27 cm
L(collector) = 30 cm
Electron gun
Drift tubes& cavities
Electron collector
Sub elementKlystron length = 87 cm + HV connector
X Band Workshop - Components & Subsystems17
Scaling : electron gun
Gun ceramic length :
L(gun) V
X Band Workshop - Components & Subsystems18
Scaling : interaction structure
Electron gun
Interaction structure length :
L(interaction) q
q : reduced plasma length
q V.K-0.5.f -1
X Band Workshop - Components & Subsystems19
Scaling : collector
Collector length (empirical) :
L(interaction) K-0.5.(V.I)0.42
K dependence due to natural beam expansion
X Band Workshop - Components & Subsystems20
Dimensioning parameters
System size scales more with power and voltage than with frequency
Focusing solenoid is a major contributor to weight, size and power consumption
HV modulatorOil tank
Focalisation
Power transmissionLinac
Klystron
X Band Workshop - Components & Subsystems21
X band klystron
Alternative technologies
Dealing with : weight size high voltage
X Band Workshop - Components & Subsystems22
PPM focusing technology
Single beam klystron with PPM focusing allows reduction of size, weight and power consumption
Magnetic field (red) and electron trajectories
X Band Workshop - Components & Subsystems23
Multi Beam Klystron (MBK) technology
Perveance K = I / V1.5
Peak power P = V.I
A number of beams interacting together in cavities :
K(total) = Σ K(beam)
Lower voltage (goal : under 50 kV for operation in air)
Better efficiency
Wider bandwidth (less sensibility to cavity frequency)
For medical and industrial systems :
klystron length and modulator size reduced
oil tank suppressed
X Band Workshop - Components & Subsystems24
TH1801 MBK
1.3 GHz, 116 kV, 10 MW 1.5 ms RF pulse @ 10 Hz 7 electron beam-structure
Current status : 7 serial tubes under operation at DESY. Stability at every voltage. Currently operating under saturation on FLASH machine. Full output power for conditionning and optimization of future photo-
injector of European XFEL.
7 beam electron gun
X Band Workshop - Components & Subsystems25
9.3 GHz MBK
Choice of cavity and operating mode :
Example : coaxial cavityCourtesy of C. Lingwood, Lancaster U.
Fundamental mode :
TM n,1,0
TM 0,1,1
High order mode :
TM 0,10,0
Compatibility with spatial arrangement of beams
Good beam-field coupling (high R/Q)
Sufficient mode separation or damping possibilities to avoid mode competition
Manufacturing aspect
X Band Workshop - Components & Subsystems26
Thales development team
Thales klystron & gyrotron development team :
Armel Beunas
Christophe Lievin
Rodolphe Marchesin
Jean-Christophe Bellemere
Sébastien Berger