Transcript Magnetron_Dec_2011 - Indico

sLHC
A magnetron solution for proton drivers
Amos Dexter
Simulation Using Tech-X’s
VORPAL e.m. code
SPL11
sLHC
Collaborations
Lancaster
Richard Carter, Graeme Burt, Ben Hall, Chris Lingwood
JLab
Haipeng Wang, Robert Rimmer
CEERI
Shivendra Maurya, VVP Singh, Vishnu Srivastava
TechX
Jonathan Smith
CERN
?
ESS
?
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sLHC
The Reflection Amplifier
• Linacs require accurate phase control
• Phase control requires an amplifier
Cavity
• Magnetrons can be operated as reflection amplifiers
Compared to Klystrons, in general Magnetrons
Magnetron
Load
Circulator
Injection
Source
- are smaller
- more efficient
- can use permanent magnets (at 704 MHz)
- utilise lower d.c. voltage but higher current
- are easier to manufacture
Consequently they are much cheaper to
purchase and operate
J. Kline “The magnetron as a negative-resistance amplifier,”
IRE Transactions on Electron Devices, vol. ED-8, Nov 1961
H.L. Thal and R.G. Lock, “Locking of magnetrons by an injected r.f. signal”,
IEEE Trans. MTT, vol. 13, 1965
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sLHC
Proof of principle
Demonstration of CW 2.45 GHz magnetron driving a
specially manufactured superconducting cavity in a
VTF at JLab and the control of phase in the presence of
microphonics was successful.
Double
Balance Mixer
Phase
shifter
Spectrum
Analyzer 1
Stub
Tuner 2
Load 3
Loop
Coupler
Circulator
3
Oscilloscope
Spectrum
Analyzer 2
Stub
Tuner 1
Loop
Coupler
2.45 GHz Panasonic
2M137 1.2 kW
Magnetron
Phase
shifter
1W
Amplifier
IQ Modulator
(Amplitude &
phase
shifter)
DAC
DAC
Digital Signal
Processor
Circulator
2
Load 2
Cathode
heater
control
Load
Oscilloscope
ADC
Digital Phase
Detector
HMC439
÷2
LP Filter
8 kHz cut-off
High Voltage
Transformer
÷2
42 kHz Chopper
Agilent E4428 signal generator
providing 2.45 GHz
300 V DC +5% 120 Hz ripple
Control voltage
Pulse Width Modulator
SG 2525
1.2 kW
Power Supply
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sLHC
SCRF cavity powered with magnetron
0
0
Injection but
magnetron off
Power spectral density (dB)
-20
Injection +
magnetron on +
control
-10
Power spectral density (dB)
-10
-30
-40
-50
-60
-70
-80
-90
-100
-20
-30
-40
-50
-60
-70
-80
-90
-110
-120
-500
-250
0
Frequency offset (Hz)
250
500
Power spectral density (dB)
Cavity phase error (degrees)
0
Injection +
magnetron on
-10
-20
-30
-40
-50
-60
-70
-80
-250
0
Frequency offset (Hz)
250
-250
0
Frequency offset (Hz)
250
500
45
Control on
35
Control off
25
15
5
-5
-15
0.00
-90
-100
-500
-100
-500
0.01
500
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0.02
0.03
Time (seconds)
0.04
0.05
sLHC
Next Steps
• Development of a 704MHz Magnetron (440kW – 880kW )
Collaboration with CEERI, Pilani, India
• Procure standard modulator
Hope to use klystron modulator with different pulse transformer however
rate of voltage rise is tightly defined. Need to deal with impedance change
on start up. The CI have a suitable 3 MW magnetron modulator for short
pulses up to 5 micro-seconds and could be used for characterisation
• Establish test station with Television IOT as the drive amplifier
Could be used for conditioning SPL and ESS components
•
•
•
•
•
Understand locking characteristics of new magnetron
Commission advanced modulator with in-pulse current control
Establish minimum locking power
Establish two magnetron test stand
Develop LLRF for simultaneous phase and amplitude control
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sLHC
Layout using one magnetron per cavity
Permits fast phase control but only slow, full range amplitude control
Cavity
Standard
Modulator
Pulse to pulse
amplitude can
be varied
880 kW
Magnetron
Slow
tuner
~ -13 dB to -17 dB needed for locking
i.e. between 18 kW and 44kW hence
between 42 kW and 16 kW available
for fast amplitude control
Load
4 Port
Circulator
LLRF
60 kW
IOT
Could fill cavity with IOT then pulse magnetron when beam arrives
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sLHC
Layout using two magnetrons per cavity
Phasor
diagram
output of
magnetron 1
Permits fast full range phase and amplitude control
output of
magnetron 2
Cavity
combiner /
magic tee
Advanced
Modulator
440 kW
Magnetron
Fast
magnetron
tune by
varying output
current
440 kW
Load
440 W
~ -30 dB
needed for
locking
Magnetron
440 W
LLRF
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Advanced
Modulator
Fast
magnetron
tune by
varying output
current
sLHC
Reflection Amplifier Controllability
1.
Phase of output follows the phase of the input signal
2.
3.
Phase shift through magnetron depends on difference between input frequency and the
magnetrons natural frequency
Output power has minimal dependence on input signal power
4.
Phase shift through magnetron depends on input signal power
5.
There is a time constant associated with the output phase following the input phase
Anode
Voltage
10kW
915MH
z 30kW
20kW
916MHz
40kW
12.0 kV
3.00A
11.5 kV
2.92A
Magnetron frequency and output vary
together as a consequence of
1. Varying the magnetic field
2. Varying the anode current (pushing)
3. Varying the reflected power (pulling)
0o
Arcing
Power
supply
load
11.0 kV
line
towards
magnetron
Moding
2.85A
900 W
800 W
700 W
2.78A
10.5 kV
2
270o
2.70A
10.0 kV
1
2
3
4
5
VSWR
3 4 6
90o
+5MHz
Magnetic
field coil
current
+2.5MHz
-5MHz
Anode Current Amps
-2.5MHz
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+0MHz
180o
sLHC
CEERI Collaboration
Dr Shivendra Maurya of the Microwave Tube Division, CEERI, PILANI, India visited
Lancaster University from 1st August to 31st November to start work on the design of
a suitable magnetron.
This visit has been funded by the Royal Academy of Engineering.
If there is sufficient interest CEERI will seek funding to manufacture the magnetron.
CEERI already manufacture a range of tubes mainly for use in India.
5 MW (pk), 5kW(avg) S-band
Klystron as RF amplifier for
injector microtron in
Synchrotron Radiation Source
at RRCAT, Indore
S-band, 3.1 MW Pulse Tunable
Magnetron for Accelerator
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Specification of initial device
Frequency
Power
Pulse length
Max average power
Efficiency
Magnet
External Q
Mechanical Tunability
Cathode heating
704 MHz
200 kW to 1 MW
5ms to 5 ms (for max power)
100 kW
> 90% above 500 kW
NyFeB (< 0.5 T)
~ 50 (for ease of locking)
~ 5 MHz
indirect and controllable
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Approximate Calculations
Using standard theory one can estimate Magnetic field, anode and cathode radii from
requirement data (frequency 704 MHz, efficiency >90% and power
Power output
Overall efficiency target
DC power
DC impedance
Anode voltage
Anode current
Cathode plus circuit losses
electronic efficiency
V anode over V threshold
V threshold
Modified Slater factor
Number of Vanes
Anode radius
Cathode radius
Anode height
Cathode current density
Electric field
Voltage field product
B
W
W
Ohms
V
m
m
m
A/m^2
V/m
kV/mm^2
T
5.26E+05
0.9066
5.80E+05
1615
30611
18.954
4.00%
94.66%
1.25
24488
1.96
14
0.02400
0.01775
0.05536
3070
9.79E+06
299.6
0.30477
1.00E+06
0.9210
1.09E+06
1615
41876
25.930
4.00%
96.10%
1.25
33501
2
14
0.02401
0.01774
0.05536
4202
1.34E+07
559.8
0.41331
Given
Assumed
Derived
Guessed
Derived
Derived
Estimated
Derived
Assumed
Derived
Assumed
Assumed
Calculated
Calculated
Assumed
Derived
Derived
Derived
Calculated
Should be able to use same block for efficient generation at
both the 500 KW and 1 MW level
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e 
B  0.5Bo
B  1.5Bo
Bo  4
m rf
1
e N 1  rc ra 2
2
2m  rf  2
Vo 

 ra
e  N 
Vth
B
2
1
Vo
Bo
r r 
V
SF   a c  N 1 
Vc
 ra  rc 
 B

Vc  Vo 
 Bo 
2
sLHC
Expected operating range
Threshold
for moding
Short
circuit
regime
VORPAL
simulations
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sLHC
Take
VORPAL Predictions at 30 kV
Amps
Anode current (A)
B = 0.3 T,
Va = 32 kV,
Ic = 60 A
time (s)
Volts
Predict
Ianode = 19 A,
Efficiency = 92%,
Cathode voltage (V)
Power = 560 kW
Z = 1684 W
time (s)
Watts
Output power (W)
time (s)
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sLHC
Volts
Moding Issues
Voltage in magnetron
Excitation in the mode at
1060 MHz might be a
problem.
We think the coarse
mesh or other issues with
the simulation might
exacerbate the issue.
time (s)
Volts
time (s)
FFT (dB)
time (s)
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sLHC
MWS modes
p mode at 702 MHz
p1 mode at 1060 MHz
p1 mode at 1063 MHz
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0.010
sLHC
Efficient Orbits
0.005
An efficient orbit should have no loop
-0.025
-0.020
-0.015
-0.010
0.000
-0.005
0.000
0.005
-0.005
-0.010
-0.015
-0.020
-0.025
-0.030
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0.010
0.015
0.020
0.025
sLHC
Magnetron Size
air cooling
for cathode
704 MHz
water
cooling for
anode
Magnets
dg
dm
dg
~ 360 mm
dm
~ 165 mm
hm
~ 650 mm
cost
£8000
hm
If magnetron design is
similar to industrial design
with similar tolerances and
can be made on same
production line then cost
may not be much more
air cooling input
for dome
SPL11
sLHC
High Efficiency Klystrons
• Design of high efficiency klystrons for ESS in
collaboration with CLIC
– Similar Klystrons (704.4 MHz, 1.5 MW, 70%
efficiency) allow synergetic activities with CLIC.
– Focus on understanding of bunching process
and space charge in the output cavity.
– Using evolutionary algorithms to improve
optimisation
– New design concepts to achieve optimum beam
modulation
– Single and Multiple beams investigated
Images courtesy of Thales Electron Devices
SPL11