A repetitive PFN-MARX generator based on an innovative ...
Transcript of A repetitive PFN-MARX generator based on an innovative ...
7 DÉCEMBRE 2016 | PAGE 1 CEA | 20 SEPTEMBER 2016
A repetitive PFN-MARX generator
based on an innovative design
for compactness and rise time improvement
Session 7
Oral 104
F. Lassalle, A. Morell, A. Loyen, T. Chanconie, B. Roques, M. Toury
CEA, DAM, GRAMAT, F-46500 Gramat France
Presented by Martial Toury
Contact : [email protected]
This work is supported by the DGA (Direction Générale de l’Armement)
www.cea.fr
GLOBAL SCOPE OF THIS STUDY
7 DÉCEMBRE 2016 | PAGE 2 CEA | 20 SEPTEMBER 2016
Square pulse Voltage plateau 100 kV – 1 MV
Duration 30 ns – 300 ns
Rise time < 10 ns
Repetitive operation Repetition 10 pps – 200 pps
Driver compactness voltage / length > 0,5 MV / m
stored energy / volume > 1 kJ / m3
Development of HV drivers with :
Applications
Pulsed power source (modulators) for :
Microwave, EM wave, laser, electron beam, ion beam, X-ray, plasma, etc …
Application domains : Defense, Security, Research, Industry, Others …
overshoot
Juin 2014
Vo
lta
ge
(k
V)
time (ns)
plateau duration
plateau
voltage
rise time
SPECIFIC OBJECTIVE OF THIS STUDY
7 DÉCEMBRE 2016 | PAGE 3 CEA | 20 SEPTEMBER 2016
‘Development of a Compact Narrow-band High Power Microwave System’ (see Proceedings of 2016 IEEE International Power Modulator and High Voltage Conference)
300 MW HPM
system inside a
cubic volume
65cm side
Charger
45 kV
HV Driver
400 KV,100 pps
HPM Source
BWO 2-300 MW
Prime Power
Batteries
Antenna
300 MW
Need a very compact
square pulse driver
400 kV – 80 ns – 5 ns rise
repetition 100 pps
Length < 65 cm
Diameter < 40 cm
POSSIBLE TECHNICS FOR THE DRIVER
7 DÉCEMBRE 2016 | PAGE 4 CEA | 20 SEPTEMBER 2016
SQUARE PULSE DRIVER TECHNICS
Transformer + Pulse Forming Line
Marx + Pulse Forming Line
Stacked cable Marx
Stacked Blumlein Marx
Stacked stripline Marx
…
Stacked PFN Marx Chosen for its compactness, reliability,
quality shape of the pulse, …
FAST RISE TIME
Typical design :
driver with ‘slow’ rise time
+ peaking stage for sharpening
Is it possible to avoid peaking stage ?
Need for a very low inductance driver
Rise time
1,2 L / Rtotal
Driver Matched load Rload = (L/C)^0,5
K
1 2
C
L R
Rload
DESIGN APPROACH
FOR MARX COMPACTNESS OPTIMIZATION
7 DÉCEMBRE 2016 | PAGE 5 CEA | 20 SEPTEMBER 2016
A standard Marx design
A possible zigzag design
for compactness optimization
in vertical direction A cylindrical
ceramic capacitor
ground
Cap 1
HV output
Cap 2
Cap 3 Cap 4
A switch
ground
Cap 1
HV output
Switch 1
Switch 2
Switch 3
Cap 2
Cap 3
Cap 4
THE SWITCHES ARE ARRANGED
WITHIN A COLUMN
7 DÉCEMBRE 2016 | PAGE 6 CEA | 20 SEPTEMBER 2016
Column of switches for a reliable Marx erection
Pre-ionisation of gaps thanks to UV radiation from switch to switch Very reliable timing sequence in Marx erection process
Only first switch is triggered Its gap is divided in 2 by a disk trigger electrode
30 kV trigger pulse from a small pulsed transformer
Stray capacitances of stages 2 to 4 are increased, to favor the erection This stray capacitance is adjusted by reducing the gap between the
upstream stage electrode and the grounded vessel
Small gap increase from switch 2 to switch 16 Gaps from 1,3 mm to 2,2 mm for SF6 gas at 6 atm.
Switches Electrodes Tungsten-Copper alloy, to limit erosion for repetitive operation
Photo of the
4 first switches
of this column
THE INDUCTANCE OF A MARX
7 DÉCEMBRE 2016 | PAGE 7 CEA | 20 SEPTEMBER 2016
For any Marx, during the discharge, the volume occupied by the magnetic field B is between
the Marx circuit (caps and switches) and the return current electrode (vessel).
Column of switches must be closed to the return current electrode
Reduction of this magnetized volume, and so, reduction of the inductance LMARX .
A
View from A
Return current
electrode
(vessel)
Switch 3
Switch 2
Switch 1
magnetized
volume
54 mm
with SF6 @ 6atm
for this Marxground
HV output
Cap 1Switch 1
Cap 2
Cap 3
Cap 4
Switch 2
Switch 3
But the zigzag design also enables more inductance reduction …
Example : the proposed Zigzag Marx
THIS INNOVATIVE ZIGZAG DESIGN
ALLOWS EXTRA INDUCTANCE REDUCTION
7 DÉCEMBRE 2016 | PAGE 8 CEA | 20 SEPTEMBER 2016
From flux expression,
inductance LMARX is :
IdSBLMARX /.
Rise time L / R rise time optimization
Thanks to this zigzag design, 2 phenomena contribute to extra reduction of inductance LMARX :
- The reduction of the magnetized volume, due to the reduction of the Marx length along Y axis
- The coupling between the antagonistic B fields which are generated around 2 successive switches
For the specific Zigzag Marx presented here, inductance is only 25 nH / stage It would be > 40 nH / stage for a ‘straight’ Marx.
View from A
ground
HV output
IMARX
A
Y
axis
Return current
electrode
(vessel)
B
Ireturn current
Ireturn current
Ireturn current
IMARX
switch 3
B
B
IMARX
switch 2
IMARX
switch 1
VOLTAGE PLATEAU IS OBTAINED
WITH STACKED PFNs
7 DÉCEMBRE 2016 | PAGE 9 CEA | 20 SEPTEMBER 2016
Marx with N stages,
each Marx stage is a PFN,
a PFN is S cells (L,C) in serie.
PFN Marx
(N=4 and S=6 for scheme below)
Rload
L
C
Plateau duration
Marx impedance
Plateau voltage
Beyond this rise time optimization, many applications need to hold a constant voltage :
Voltage plateau with amplitude Vp and duration Tp
DETAILED DESIGN OF A PFN STAGE
7 DÉCEMBRE 2016 | PAGE 10 CEA | 20 SEPTEMBER 2016
C = 2,1 nF
is a ceramic capacitor AVX - HP60E40242K
Ceramic N4700 (with Strontium)
diam. 58 mm, height 30 mm No rigid clamp on capacitors
S = 6
6 (L,C) cells are connected in serie
L = 36 nH
is given by this strip line geometry
Hemispherical electrodes of switch are
screwed in strip line electrode ends
Curved shape of this PFN is for integration
in a cylindrical vessel
Rload
C
L switch
Top view Bottom view
C
Strip line
Connexions
to charging
circuit
Half
switch
THE 16 STAGES PFN MARX
7 DÉCEMBRE 2016 | PAGE 11 CEA | 20 SEPTEMBER 2016
scale
100 mm
Vessel inner diam. 360 mm
: increased stray capacitance
• Zigzag design for compactness and rise time optimization
• PFN stages for 85 ns plateau duration
• 16 stages, 204 J stored energy @ Vch=45 kV
• Charging circuit with inductances for repetitive operation without resistive losses
during charging
• Gas pressurized vessel Volume 63 liters for these 16 stages and switches
• Weight 44 kg (without vessel)
• Can work in any position Vertical, horizontal, tilted
• Self supporting structure
SELF SUPPORTING STRUCTURE
Self-supporting structure None additional insulating support
Minimize the risks of losses due to surface ramping
+ easy maintenance, reduction of weight
• Charging circuit is made with
4 columns of stacked inductances
• These 4 columns support the 16 PFN stages
• Striplines of the PFN stages support the switches
Zoom
on a 140 µH
single inductance
of the
charging circuit
• Same volume of gas for switches and for stages insulation
Big gas volume beneficial for better dilution of by-products
(switch electrodes erosion, gas breakdown by-products)
Improve the reliability of system for repetitive operation
Column of
stacked
inductance
Column
height
56cm
PFN MARX DESIGN AND OPERATION ARE
ANALYSED THROUGH DETAILED SIMULATIONS
7 DÉCEMBRE 2016 | PAGE 13 CEA | 20 SEPTEMBER 2016
Pspice : circuit simulations Including dynamic model for switches resistance (Braginsky), stray capacitances, transmission lines,
inductances of charging circuit, Child-Langmuir model for e-beam diode, etc.
Example :
Comparison
simulation versus
experiment
for a load 68 - 90 nH
0 50 100 150
0
100
200
300
400
80ns
Vo
lta
ge
(kV
)
time (ns)
simulation
experiment
CST : 3D EM simulations static and time domain simulations
Example :
Electrostatic simulation
of the gas-vacuum HV
insulator
EXAMPLE OF APPLICATION :
PFN MARX DRIVING A MICROWAVE TUBE
7 DÉCEMBRE 2016 | PAGE 14 CEA | 20 SEPTEMBER 2016
output of
PFN Marx U shaped line
conical
HV insulator
(Length = 130 mm)
e-beam diode
of BWO
(Zload = 100 )
Connexion between Marx and load is optimized :
U shaped to keep a length of global system < 65cm
Low inductance connexion
80 line impedance to minimize pulse reflections
Same pressurized gas insulation as the Marx
Very compact gas-vacuum HV insulator
Self-supporting structure
The load is a microwave tube :
an X-band relativistic BWO
Nota :
Marx impedance is slightly undermatched, for more compactness :
Rload = 100 and ZMARX = 66 , with N=16 stages only.
EXPERIMENTAL RESULTS
7 DÉCEMBRE 2016 | PAGE 15 CEA | 20 SEPTEMBER 2016
1000 pulses burst with 85 pps repetition * (only 100 pulses shown here)
* Repetition rate is limited to 85 pps because of the capacitor charger
A new capacitor charger is needed for higher repetition rate
-20 0 20 40 60 80 100 120 140
0
100
200
300
400
500
PFN MARX on a 100 load (BWO ebeam diode)
Juin 2014
Vo
lta
ge
(k
V)
time (ns)
pulses 1 to 20
pulses 21 to 40
pulses 41 to 60
pulses 61 to 80
pulses 81 to 100
85ns (plateau duration)
380 kV +/- 8%
5ns (rise time 10%-90%)
CONCLUSION
7 DÉCEMBRE 2016 | PAGE 16 CEA | 20 SEPTEMBER 2016
• A PFN Marx driver based on an innovative design has been developped :
Square pulse 400 kV – 85 ns, with repetition rate 100 pps
• This innovative zigzag design * allows to reach :
High compactness : 0,6 MV / m
Fast rise time : 5 ns without peaking stage
• This zigzag design and other design rules described here can be used to develop
compact and fast HV drivers (square pulse or other pulse shapes)
for a large range of applications :
Microwave, EM wave, laser, electron beam, ion beam, X-ray, plasma, etc …
covering several application domains :
Defense, Security, Research, Industry, Others …
* Patent Demande de brevet d’invention n° FR 1 552 131, déposée le 16/03/2015 à l’Institut National de la Propriété Industrielle.
Titre de l’invention : « Générateur d’Impulsions de Haute Tension ».
Titulaire : Commissariat à l’Energie Atomique et aux Energies Alternatives.
Inventeur : Lassalle Francis.
PERSPECTIVES
7 DÉCEMBRE 2016 | PAGE 17 CEA | 20 SEPTEMBER 2016
• On going work
Run 3D EM simulations of full driver, to analyse detailed behavior of this prototype and to refine
improvement capabilities
Continue testing to complete the characterisation of this prototype :
What is repetition rate limitation when working with SF6 gas ?
What are characteristics when working with other gases (Dry air, ..) ?
What are limitations for > 10s bursts of 1000 pulses (life time, service procedure, …)
…
Continue study of a 300 MW HPM system inside a cubic volume 65cm side, using this compact driver
• Other perspectives
Further compactness improvements (capacitors with improved compactness and performances,
dielectric strip lines instead of PFN lines, etc.)
Further rise time improvements : reduction of insulation gaps, optimization of zigzag effect
(switches closer to vessel, conical vessel for a progressive gap increase versus each stage voltage, …)
Extend the scope of applications of drivers and modulators based on the design rules presented here.
DAM
DEA
SERE
LDRX
Commissariat à l’énergie atomique et aux énergies alternatives
Centre de Gramat | BP 80200 46500 Gramat
T. +33 (0)5 65 10 54 32 | F. +33 (0)5 65 10 54 33
Etablissement public à caractère industriel et commercial |
RCS Paris B 775 685 019 7 DÉCEMBRE 2016
| PAGE 18
CEA | 10 AVRIL 2012
EXAMPLE OF APPLICATION :
PFN MARX DRIVING A MICROWAVE TUBE
7 DÉCEMBRE 2016 | PAGE 19 CEA | 20 SEPTEMBER 2016
-40n -20n 0 20n 40n 60n 80n 100n 120n
0
100k
200k
300k
400k
500k
PF
N M
arx
ou
tpu
t v
olt
ag
e (
V)
time
0
100M
200M
300M
400M
500M
14ns
single pulse
BW
O X
ba
nd
po
we
r (W
)
Measured radiated E-field
at 10 m from the antenna
(normalized instantaneous
and RMS values of the
horizontal component).
PFN Marx vessel Inner diam.= 360 mm
Height = 650 mm
Microwave tube : BWO Disk antenna
R. Vézinet, F. Lassalle, S. Tortel, J.C. Diot, A. Morell , A. Loyen, A. Catrain, Q. Saurin, A. Paupert,
‘Development of a Compact Narrow-band High Power Microwave System’
Proceedings of 2016 IEEE International Power Modulator and High Voltage Conference
STRAY CAPACITANCES
7 DÉCEMBRE 2016 | PAGE 20 CEA | 20 SEPTEMBER 2016
Stray capacitances Cs of stages 2 to 4 are increased,
to favor the erection.
This stray capacitance is adjusted by reducing the gap between
the upstream stage electrode and the grounded vessel.
scale
100 mmSwitch S1 is triggered
Voltage on switch S2 is :
High V needs low Cg / Cs
V0
Vessel inner diam. 360 mm
3D EM SIMULATION
OF ZIGZAG EFFECT
7 DÉCEMBRE 2016 CEA | 20 SEPTEMBER 2016
Configuration : Zigzag with electrode 10mm ;
Plane return current electrode
Z
Y
X
3D current density B field module
BY BZ
zigzag plane 54 mm 54 mm
Z
Y
X
20 mm 20 mm
BY BZ
Gap 54 mm
Zigzag
inductance
37 nH / step
Zigzag step :
length 60mm along X
+ length 33 mm along Y Comparison
with a
straight electrode
length 93mm
along Y
Gap 20 mm
Zigzag
inductance
28 nH / step
Gap 20 mm
Straight
inductance
45 nH / step
Gap 54 mm
Straight
inductance
77 nH / step
CST MWS - Simulations @50 MHz ( 5ns rise)
zigzag plane
X cut view X cut view
X cut view X cut view
ROUGH CIRCUIT SIMULATION
7 DÉCEMBRE 2016 | PAGE 22 CEA | 20 SEPTEMBER 2016
A rough simulation can evaluate rise time
but can’t give the right shape and amplitude of plateau
Need for the detailed simulation presented page 13
-20 0 20 40 60 80 100 120 140
0
100
200
300
400
500
PSpice
(rise time 10%-90%)
(plateau duration)
380 kV +/- 8%
85ns
PFN MARX on a 100 load ( BWO ebeam diode)
Vo
lta
ge
(k
V)
time (ns)
Juin 2014
5ns
Experiment
Simplified PSPICE simulation without Braginsky model for switches
without stray capacitances
without detailed transmission lines
Etc.
{C}
{L}
{C}
{L} {L} {L} {L} {Lmarx}
{C} {C} {C} {C}
{C}
{L}
{C}
{L} {L} {L} {L} {Lmarx}
{C} {C} {C} {C}
{C}
{L}
{C}
{L} {L} {L} {L} {Lmarx}
{C} {C} {C}{C}
{C}
{L}
{C}
{L} {L} {L} {L} {Lmarx}
{C} {C} {C} {C}
{C}
{L}
{C}
{L}{L}{L}{L}{Lmarx}
{C}{C}{C}{C}
{C}
0
{C}
{L}
{C}
{L}{L}{L}{L}{Lmarx}
{C} {C}{C}{C}
{C}
{L}
{C}
{L}{L}{L}{L}{Lmarx}
{C} {C}{C}{C}
{C}
{L}
{C}
{L}{L}{L}{L}{Lmarx}
{C} {C}{C}{C}
{C}
{L}
{C}
{L}{L}{L}{L}{Lmarx}
{C} {C}{C}{C}
PARAMETERS:
Lg = 140u
Lv = 140u
{C}
{L}
{C}
{L}{L}{L}{L}{Lmarx}
{C} {C}{C}{C}
{C}
{L}
{C}
{L}{L}{L}{L}{Lmarx}
{C} {C}{C}{C}
U1TCLOSE = 0
1 2
{C}
{L}
{C}
{L}{L}{L}{L}{Lmarx}
PARAMETERS:
ROPEN = 1k
TTRAN = 2n
RCLOSED = 10m
{C} {C}
U2TCLOSE = 4n
12
U3TCLOSE = 8.3n
1 2
{C}{C}
U4TCLOSE = 10n
12
U5TCLOSE = 12.9n
1 2
U6TCLOSE = 14n
12
U7TCLOSE = 15n
1 2
U8TCLOSE = 16n
12
U9TCLOSE = 16.5n
1 2
U10TCLOSE = 17n
12
U11TCLOSE = 17.25n
1 2
U12TCLOSE = 17.5n
12
U13TCLOSE = 17.75n
1 2
Lv 3
{Lv}
U14TCLOSE = 18n
12
U15TCLOSE = 18.25n
1 2
U16TCLOSE = 18.5n
12
Lv 5
{Lv}
Lv 7
{Lv}
Lv 9
{Lv}
Lv 11
{Lv}
Lv 13
{Lv}
Lv 15
{Lv}
Lg3
{Lg}
Lg5
{Lg}
Lg7
{Lg}
Lg9
{Lg}
Lg11
{Lg}
Lg13
{Lg}
Lg15
{Lg}
PARAMETERS:
C = 2.1n
L = 36n
Vch = 41k
Rload
100
0
Lline = 140 nHTline
Z0 = 80
TD = 1.75n
00
PARAMETERS:
Lmarx = 20nH
LMARX total = 320 nH
{L}
{C}
{L} {L} {L} {L} {Lmarx}
{C} {C} {C} {C}
I
V
Lg2
{Lg}
Lv 4
{Lv}
Lv 6
{Lv}
Lv 8
{Lv}
Lv 10
{Lv}
Lv 12
{Lv}
Lv 14
{Lv}
Lv 16
{Lv}
Lg4
{Lg}
Lg6
{Lg}
Lg8
{Lg}
Lg10
{Lg}
Lg12
{Lg}
Lg14
{Lg}
Lg16
{Lg}
Lv 2
{Lg}
{C}
{L}
{C}
{L} {L} {L} {L} {Lmarx}
{C} {C} {C} {C}
{C}
{L}
{C}
{L} {L} {L} {L} {Lmarx}
{C} {C} {C} {C}
{C}
{L}
{C}
{L} {L} {L} {L} {Lmarx}
{C} {C} {C} {C}