Transcript Klystron development in X band

Klystron development in X band
Sébastien Berger
[email protected]
R&D Thales Electron Devices
X Band Workshop - Components & Subsystems
Thales Components & Subsystems
Applications
Medical radiology
Radiography, radiology
Angiography, urology
Dental 3D imaging
Vet exams
Digital flat detectors
X-Ray Imaging Units
X-Ray Image Intensifiers
CCD cameras
Associated sub-systems
Space
Telecom
Broadcast
Earth observation
Navigation….
Defense
Radars
Countermeasures
Missiles
Traveling Wave Tubes
Amplifiers
Power Grid Tubes
Associated
sub-systems
Traveling Wave
Tubes
Transmitters
Klystrons
CFAs
Associated subsystems
Subsystems and products
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X Band Workshop - Components & Subsystems
Science
Fusion
Light Sources
Large accelerators
Klystrons
Gyrotrons
Diacrodes
Associated subsystems
Industrial
NDT-Security
Laser
Industrial heating
Sterilization
Power grid tubes
X-Ray Tubes
X-Ray detectors
Associated subsystems
From Components to Subsystems - Science
Klystrons, gyrotrons,
IOTs & tetrodes
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X Band Workshop - Components & Subsystems
RF amplifier
Energy storage
Mega Joule Laser
Outline
 Klystron technology for X band
 A single beam 9.3 GHz / 4 MW Klystron
 Alternative technologies
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PPM focusing
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Multi-Beam Klystron
X Band Workshop - Components & Subsystems
X band klystron
Klystron source for medical and
industrial applications
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X Band Workshop - Components & Subsystems
The klystron, a high-gain amplifier
Signal from 9.3 GHz
oscillator
Output ~ MW
Input ~10 W
preamplifier
Solid-state device
Isolator/circulator
Klystron
amplifier
Klystron is a high-power, high-gain amplifier providing :
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More peak power than magnetrons
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Stability of output power
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Reliability : theoretical long lifetime even at high frequencies
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Output power versatility
X Band Workshop - Components & Subsystems
X band for industrial and medical applications
Klystron
Power transmission
Linac
Focalisation
HV modulator
Oil tank
… but in field of industrial and medical applications, some others parameters
have strong importance :
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Compactness of the source as a whole : klystron + (oil tank)
+ HV modulator
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Availability of passive components
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Power consumption
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Cost
X Band Workshop - Components & Subsystems
X band klystron
Single beam 4 MW Klystron
Electromagnet focusing
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X Band Workshop - Components & Subsystems
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
0.001
Duty cycle
-1 dB bandwidth
>30 MHz
1.0 µA / V1,5
Perveance (K)
49 %
Efficiency
Expected lifetime
> 30 000 hours
Operating conditions
Cathode voltage (V)
152 kV
Cathode current (I)
60 A
X ray shielding
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X Band Workshop - Components & Subsystems
integrated
Interaction structure
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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…)
Simulation of klystron operation : electron beam interaction with cavities’ RF field
animation period = 1 / (9.3 GHz)
Axial electron velocity
RF in
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X Band Workshop - Components & Subsystems
RF out
Power transfer curve
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4.5
152 kV nominal voltage
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Output power (MW)
3.5
140 kV
3
130 kV
2.5
2
120 kV
1.5
1
0.5
0
0
10
20
30
40
50
60
70
Input power (W)
Calculation result at nominal cathode voltage : • saturation gain = 51.5 dB
(V=152 kV)
• Output power = 4.3 MW
• Efficiency = 49 %
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X Band Workshop - Components & Subsystems
Bandwidth at saturation
Wide instantaneous bandwidth compared to magnetron
Thales 9.3 GHz Klystron
52.0
51.5
51.0
50.5
Gain (dB)
50.0
49.5
49.0
48.5
48.0
47.5
47.0
46.5
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)
Calculated bandwidth at –1 dB : 60 MHz (at nominal cathode voltage)
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X Band Workshop - Components & Subsystems
The challenges of X band for standard klystron
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RF electric field in output cavity
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Directly limits the pulsed output power
Power loss in output window
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Directly limits the average output power
Calculation of window’s temperature
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X Band Workshop - Components & Subsystems
Klystron & electromagnet interfaces
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Output waveguide
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WR112 flange
SF6 pressurization (3 bars)
Water cooling
Total flow ~ 26 L / min
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Electromagnet
Power consumption ~ 4 kW
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Electron gun power supply
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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
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X Band Workshop - Components & Subsystems
Footprint and weight
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Klystron
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Electromagnet
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Height = 0,9 m
Weight ~ 60 kg
Output flange at 400 mm from axis
Outer diameter = 500 mm
Weight ~ 350 kg
X Band Workshop - Components & Subsystems
Scaling of klystron length
Klystron length = 87 cm + HV connector
Sub element
L(collector) = 30 cm
L(interaction) = 27 cm
L(gun) = 30 cm
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X Band Workshop - Components & Subsystems
Electron collector
Drift tubes
& cavities
Electron gun
Scaling : electron gun
Gun ceramic length :
L(gun)  V
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X Band Workshop - Components & Subsystems
Scaling : interaction structure
Interaction structure length :
L(interaction)  q
q : reduced plasma length
q  V.K-0.5.f -1
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Electron gun
X Band Workshop - Components & Subsystems
Scaling : collector
Collector length (empirical) :
L(interaction)  K-0.5.(V.I)0.42
K dependence due to natural beam expansion
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X Band Workshop - Components & Subsystems
Dimensioning parameters
Klystron
Power transmission
Linac
Focalisation
HV modulator
Oil tank
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
System size scales more with power and voltage than with
frequency
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Focusing solenoid is a major contributor to weight, size and
power consumption
X Band Workshop - Components & Subsystems
X band klystron
Alternative technologies
Dealing with :
 weight
 size
 high voltage
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X Band Workshop - Components & Subsystems
PPM focusing technology
Single beam klystron with PPM focusing allows reduction of
size, weight and power consumption
Magnetic field (red) and
electron trajectories
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X Band Workshop - Components & Subsystems
Multi Beam Klystron (MBK) technology
Perveance
Peak power
K = I / V1.5
P = V.I
A number of beams interacting together in cavities :
K(total) = Σ K(beam)
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Lower voltage (goal : under 50 kV for operation in air)
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Better efficiency
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Wider bandwidth (less sensibility to cavity frequency)
For medical and industrial systems :
 klystron length and modulator size reduced
 oil tank suppressed
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X Band Workshop - Components & Subsystems
TH1801 MBK
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1.3 GHz, 116 kV, 10 MW
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1.5 ms RF pulse @ 10 Hz
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7 electron beam-structure
Current status :
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7 serial tubes under operation at DESY. Stability
at every voltage.
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Currently operating under saturation on FLASH
machine.
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Full output power for conditionning and
optimization of future photo-injector of European
XFEL.
7 beam electron gun
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X Band Workshop - Components & Subsystems
9.3 GHz MBK
Choice of cavity and operating
mode :
Example : coaxial cavity
Courtesy of C. Lingwood, Lancaster U.
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Compatibility with spatial arrangement of beams
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Good beam-field coupling (high R/Q)
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Sufficient
mode
separation
or
possibilities to avoid mode competition
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Manufacturing aspect
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Fundamental mode :
damping
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High order mode :
TM 0,1,1
TM n,1,0
TM 0,10,0
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X Band Workshop - Components & Subsystems
Thales development team
Thales klystron & gyrotron development team :
Armel Beunas
Christophe Lievin
Rodolphe Marchesin
Jean-Christophe Bellemere
Sébastien Berger
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X Band Workshop - Components & Subsystems