Completely Explosive Autonomous High-Voltage Pulsed-Power System Based on Shockwave Ferromagnetic Primary Power Source and Spiral Vector Inversion Generator

Abstract

Novel explosive and conventional pulsed-power technologies were combined, and a series of explosive-driven high-voltage power supplies was designed, built, and tested. The power supply contained an explosive-driven high-voltage primary power source based on the fundamental physical effect of shockwave demagnetization of Nd₂ Fe₁₄B high-energy ferromagnet and a power-conditioning stage. The volume of the energy-carrying ferromagnetic elements in the shockwave ferromagnetic generators (FMGs) was 8.75 cm³. The power-conditioning stage was based on the spiral vector inversion generator (VIG). The combined FMG-VIG system demonstrated successful operation and good performance. The output-voltage pulse amplitude of the combined FMG-VIG system exceeded 40 kV, with a rise time of 6.2 ns. The methodology was developed for digital simulation of the operation of completely explosive FMG-VIG system. Experimental results obtained are in a good agreement with the results of digital calculations performed

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1866 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 34, NO. 5, OCTOBER 2006
Completely Explosive Autonomous High-Voltage
Pulsed-Power System Based on Shockwave
Ferromagnetic Primary Power Source and
Spiral Vector Inversion Generator
Sergey I. Shkuratov, Member, IEEE, Evgueni F. Talantsev, Jason Baird, Member, IEEE,
Millard F. Rose, Fellow, IEEE, Zachary Shotts, Zack Roberts,
Larry L. Altgilbers, Member, IEEE, and Allen H. Stults
Abstract—Novel explosive and conventional pulsed-power tech-
nologies were combined, and a series of explosive-driven high–
voltage power supplies was designed, built, and tested. The power
supply contained an explosive-driven high-voltage primary power
source based on the fundamental physical effect of shockwave
demagnetization of Nd2Fe14B high-energy ferromagnet and a
power-conditioning stage. The volume of the energy-carrying fer-
romagnetic elements in the shockwave ferromagnetic generators
(FMGs) was 8.75 cm3. The power-conditioning stage was based
on the spiral vector inversion generator (VIG). The combined
FMG–VIG system demonstrated successful operation and good
performance. The output-voltage pulse amplitude of the combined
FMG–VIG system exceeded 40 kV, with a rise time of 6.2 ns. The
methodology was developed for digital simulation of the operation
of completely explosive FMG–VIG system. Experimental results
obtained are in a good agreement with the results of digital
calculations performed.
Index Terms—Direct energy conversion, explosive pulsed
power, hard ferromagnets, shockwave demagnetization.
I. INTRODUCTION
P
tems) are important to the success of many scientific and
engineering projects [1]–[6]. Novel types of compact and ultra-
compact autonomous explosive-driven pulsed-power sources,
utilizing the electromagnetic energy stored for an infinite pe-
riod of time in high-energy hard ferrimagnets and hard fer-
romagnets, were developed recently [7]–[21]. Operation of
these devices is based on the fundamental physical effects
of shockwave demagnetization of hard ferrimagnets [7], [12]
and hard ferromagnets [8]–[21]. Miniature (9–25 cm3in vol-
ume) generators based on these effects are capable of produc-
ing high-voltage pulses with amplitudes greater than 20 kV
and pulses of high current with amplitudes exceeding 4 kA
ULSED-POWERsystemswithoutanyexternalpowersup-
plies (commonly named autonomous pulsed-power sys-
Manuscript received November 2, 2005; revised July 27, 2006.
S. I. Shkuratov, E. F. Talantsev, and J. Baird are with Loki Inc., Rolla, MO
65409 USA.
M. F. Rose, Z. Shotts, and Z. Roberts are with Radiance Technologies, Inc.,
Huntsville, AL 3580 USA.
L. L. Altgilbers is with the U.S. Army Space and Missile Defense Command,
Huntsville, AL 35807 USA.
A. H. Stults is with the U.S. Army Aviation and Missile Research, Develop-
ment and Engineering Center, Huntsville, AL 35898 USA.
Digital Object Identifier 10.1109/TPS.2006.883347
[8]–[21]. New technology [8]–[21] is expanding quickly in the
pulsed-power research and engineering community in the U.S.
and other countries. Since 2005, explosive-driven autonomous
pulsed-power sources based on the effect of shockwave de-
magnetization of hard ferromagnets [8]–[21] have been under
development in China [22].
Earlier[14]–[16],we demonstrated
possibility of constructing a completely explosive two-stage
pulsed-power system containing explosive-driven high-current
shockwave ferromagnetic primary power generator as a seed
source and spiral magnetic flux compression generator as
a pulsed-power amplifier. In the last few months [23], we
successfully developed a two-stage compact autonomous
explosive-driven pulsed-power system utilizing a high-voltage
compact explosive-driven shockwave ferromagnetic generator
(FMG) as a charging source for capacitive energy storage.
In this paper, we present another new concept for con-
structing compact autonomous explosive-driven pulsed-power
systems. This concept is based on a high-voltage ultracompact
explosive-driven FMG as a primary power source and a con-
ventional pulsed-power transformer [the spiral vector inversion
generator (VIG) [26]] as a power-conditioning stage.
the fundamental
II. PRINCIPLES OF OPERATION AND
EXPERIMENTAL TECHNIQUES
The general design of high-voltage shockwave FMG, the
schematic of loading the explosive, and the disposition of
the detonator are shown in Fig. 1. The generator contains a
hard ferromagnetic Nd2Fe14B energy-carrying element, a high-
explosive charge, a plastic pulse-generating coil holder with a
multiturn coil wound on it, and an output high-voltage terminal
system.
The design of the Nd2Fe14B energy-carrying element was
made as a hollow cylinder magnetized along the axis (Fig. 1).
During generator operation, high explosive loaded in the central
hole along the axis of the ferromagnetic energy-carrying ele-
ment is detonated, creating a transverse shockwave (the shock
wave propagates across the magnetization vector M) in the
body of the Nd2Fe14B hard ferromagnet. Further development
of the generator design has made it possible to dramatically
reduce the amount of the desensitized RDX high explosive
0093-3813/$20.00 © 2006 IEEE
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SHKURATOV et al.: PULSED-POWER SYSTEM BASED ON FERROMAGNETIC POWER SOURCE AND SPIRAL VIG1867
Fig. 1.
FMG.
General design of explosive-driven transverse shockwave high-voltage
(to 0.6 g), while still providing complete demagnetization
of Nd2Fe14B hard ferromagnet with an outer diameter of
25.4 mm, inner diameter of 8 mm, length of 19 mm, and
weight of 68 g. In the generators described in this pa-
per, a single RISI RP-501 exploding bridgewire detona-
tor initiated the high-explosive detonation. All FMGs were
loaded with 0.6 g of desensitized RDX high explosives
(Chapman–Jouguet state pressure of 22.36 GPa and detonation
velocity of 8.1 km/s).
The plastic pulse-generating coil holder protects the pulse-
generating system of the FMG against the mechanical action of
theexplosivechargeforafewtensofmicroseconds.Inaddition,
the coil holder provides electrical insulation between the pulse-
generating coil and the ferromagnetic energy-carrying element
(which is connected to electrical ground potential through the
detonator wires).
For fabrication of multiturn pulse-generating coils of the
FMGs, a heavily insulated magnet wire was used. A typical
high-voltage FMG containing 252-turn pulse-generating coil is
shown in Fig. 2 (diameter of the generator is 34 mm, and length
of the generator is 19 mm). FMGs contained Nd2Fe14B hollow
ferromagnetic cylinders with an outer diameter of 25.4 mm, in-
ner diameter of 8 mm, and length of 19 mm. The parameters of
the Nd2Fe14B material in a closed magnetic circuit are: residual
flux density Br= 1.23 T, coercive force Hc= 8.99 · 105A/m,
and maximum energy product BHmax= 0.279 J/cm3; industry
tolerance: Br± 5%, Hc± 8%, and BHmax± 10%.
The VIG is a pulse generator which, as a single unit, can
store an electric charge at one voltage and discharge it as a
pulse having a peak value higher than the stored voltage [26].
Fig. 2.
The generators contained Nd2Fe14B energy-carrying element with an outer
diameter of 25.4 mm, inner diameter of 8 mm, length of 19 mm, and pulse-
generating coil of 252 turns.
High-voltage FMG prepared for explosive and electrical operation.
Fig. 3.
pletely explosive FMG–VIG system.
Schematic diagram of the experimental setup used to test the com-
Schematic diagram of the VIG is shown in Fig. 3. The VIG con-
tains two sheets of conductive material and two sheets of elec-
trically insulating material arranged alternatively and wound
together into a roll forming open-ended transmission line. If
we charge this rolled foil capacitor to voltage U0and after that
we close the spark-gap switch, as a result of the discharge, the
electromagnetic wave originates from the switch and travels
along the transmission line. As the wave travels, it converts
the electrostatic field into an electromagnetic field, and when
it retraces its path after reflection at the end of the transmission
lines, it converts the electromagnetic field back into an electro-
static field. An output pulse of amplitude Uout= 2nU0(n is a
number of turns in the roll) and the rise time equal to double
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1868 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 34, NO. 5, OCTOBER 2006
electrical length of the transmission line appear at the contacts
of the VIG. The advantage of this system is simplicity and
short (nanosecond) rise time of the generated pulse. All VIGs
used in the experiments had these outside dimensions: 60 mm
in length, 30 mm in width, and 110 mm in height.
We performed the explosive experiments at the Rock Me-
chanics and Explosive Research Center of the University of
Missouri–Rolla, where we designed and constructed an ex-
perimental system to study explosive-driven pulsed power and
microwave sources. The setup has a diagnostic/test station
(Fig. 3) and a detonation tank where we fire the explosive-
driven generators. The detonation tank is a cylindrical steel
chamber 1.5 m in diameter and 5 m in length, having a nominal
2.54-cm wall thickness. The tank is capable of withstanding
nonfragmenting tests of up to 1 kg of high explosives. The
explosive-driven generators tested are placed inside the deto-
nation tank near a stainless-steel side port. The diagnostic/test
station containing probes, oscilloscopes, and other diagnostic
and experimental equipment is sited near the side port, but
outside of the detonation tank.
Some of generator’s output cables are connected to the diag-
nostic/test station through air-sealed connectors in the port, and
other output cables are connected to the diagnostic/test station
directly. In order to avoid mechanical strains being transmitted
through the generator’s output cables to the pulse measuring
and recording systems during generator firing, the output cables
are fixed in the port cover using specially developed cylindrical
clamps. During generator explosive operation, the cables cut off
at their generator connections instead of the measuring system
connections. Since mechanical strains are not transferred to the
diagnostic/test station through the cables, there is no mechan-
ical effect from the explosive detonation on the results of the
electrical measurements. Positioning the sensitive equipment
outside the tank in this manner protects the equipment from
the explosive environment within the tank, thereby preventing
test-related damage.
The arrangement of the shockwave experiments and the
circuit diagram of the measuring system are given in Fig. 3.
The output high-voltage pulses were measured with a Tektronix
P6015A high-voltage probe (rise time of 4 ns, input impedance
of 100 MΩ, and capacitance of 3 pF). The signals from the
probe were recorded with Tektronix TDS744A (bandwidth of
500 MHz and 2 GS/s) and Tektronix TDS2024 (bandwidth
of 200 MHz and 2 GS/s) oscilloscopes. The electric circuit
parameters of the generators were measured with a Hewlett-
Packard 4275 multifrequency LCR meter. Other experimental
conditions and the equipment used corresponded to those de-
scribed in the references [7]–[21], [23].
III. EXPERIMENTAL RESULTS
The VIG chosen for experiments described in this paper
was a five-turn unit made of 0.1-mm (thickness) capacitor
gradeTeflonasthedielectricand50.8-mm-wide0.05-mm-thick
copper shims as the capacitor conducting plates. This VIG was
wound on a ferrimagnetic mandrel (ferrite 2535) of 25.4-mm
width; as such, the VIG had a rectangular cross section, but this
did not affect its efficiency. The voltage efficiency (measured
by voltage multiplication) of the devices was in the 80%–90%
Fig. 4.
the oil bath.
(a) Photo of VIG used in these experiments. (b) VIG placed in
Fig. 5.Experimental setup for characterization of the VIG spark-gap switch.
range. The calculated capacitance of the devices was approx-
imately 5.6 nF. The device was oil impregnated to eliminate
corona effects and was capable of producing output voltages in
excess of 30 kV. The VIG is shown in Fig. 4.
The development of a VIG spark-gap switch is mostly a
matter of trial and error. We used a standard paper punch
to make repeatable holes in the dielectric films, which could
then be stacked to lengthen the gap. In this way, the switch
inductance was kept at a minimum and the breakdown voltage
could be somewhat controlled. To get some idea of the impulse
behavior of the gap, we developed a simple test fixture to allow
us to apply an impulse to the switch ensemble. A photo of the
test setup is shown in Fig. 5.
A schematic diagram of the experimental setup used to test
the FMG–VIG system is shown in Fig. 3. The FMG was
placed inside the detonation tank. The output terminals of the
FMG were connected to the input of the VIG. The negative
terminal of the FMG was grounded. Correspondingly, the FMG
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SHKURATOV et al.: PULSED-POWER SYSTEM BASED ON FERROMAGNETIC POWER SOURCE AND SPIRAL VIG1869
Fig. 6.
generating coil). Open-circuit operation.
Waveform of the pulsed EMF produced by an FMG (257-turn pulse-
produced a positive high-voltage pulse. This high-voltage pulse
was applied to the input of the VIG spark gap. The output volt-
age of completely explosive FMG–VIG system was connected
directly to the Tektronix P6015A high-voltage probe.
Operation of the FMG–VIG system is as follows. The
explosive-driven FMG produces a high-voltage pulse of dura-
tion 5–8 µs that impulse charges the VIG. When the charge
voltage exceeds the VIG spark-gap hold-off threshold, the VIG
erects in a time equal to two wave transit times through the
device (∼ 6 ns), producing a transient voltage that is several
times greater than the breakdown voltage of the VIG spark-gap
switch.
The basis for the production of high voltage at the output
terminalsofFMGisFaraday’s lawthatisrelatedtothedecrease
in the initial magnetic flux in the ferromagnetic energy-carrying
element due to shockwave action. For a multiturn coil, the
generated electromotive force (EMF) is the sum of the EMFs
produced by all the turns
Em.-turn(t) =
?
N
[−dΦn(t)/dt]
(1)
where dt is the time in which the change in the magnetic flux in
the turn, dΦn(t) is the magnetic flux captured by the nth turn
of the multiturn coil and N is the number of turns in the coil.
ThefirstseriesofexperimentswasperformedwithFMGsop-
erating in the open-circuit mode. A typical EMF waveform pro-
duced by a typical FMG containing a 257-turn pulse-generating
coil operating in the open-circuit mode is shown in Fig. 6.
TheEMFpulseamplitudewasUg(t)max= 9.44kV,FWHM =
6.67 µs, and τ = 1.2 µs. The slope of the EMF curve at the
moment of the beginning of demagnetization ∆Ug(t)max/∆t
is 7.87 kV/µs. There are no breaks or distortions in the EMF
pulse waveform. The EMF specific peak Em.-turn(t)max spec
was 36.7 V/turn. The series resistance and the series inductance
of the pulse-generating coil were RS(100 kHz) = 15.1 Ω and
LS(100 KHz) = 2.3 mH, respectively.
Fig. 7.
sive nanosecond FMG–VIG pulse-generating system.
Waveform of the high-voltage pulse produced by a completely explo-
We performed six experiments with generators of this type.
The EMF pulse waveforms were very reproducible. The av-
erage EMF pulse amplitude was Ug(t)max= 9.20 ± 0.26 kV.
The average specific EMF peak for this type of FMG was
Em.-turn(t)max spec= 35.8 ± 1.4 V/turn.
Right before the FMG–VIG experiments, we preliminarily
characterized the VIG spark gap in realtime. The gap was tuned
and set to break at U = 5.9 ± 0.3 kV.
We performed five experiments with ultracompact explosive-
driven FMG–VIG pulsed-power systems. Output-voltage pulse
amplitude and shape were very reproducible. A typical wave-
form of a high-voltage pulse produced by an explosive-driven
FMG–VIG system is shown in Fig. 7. The peak voltage am-
plitude was U(t)max= 40.2 kV, FWHM = 14 ns, and τ =
6.5 ns. The slope of the output-voltage curve at the moment of
the beginning of pulsed-power generation ∆U(t)max/∆t was
6.18 kV/ns. The slope of the output voltage ∆U(t)max/∆t
of the FMG–VIG system is increased approximately on three
orders of magnitude in comparison with the output voltage of
the FMG primary power source. The average value of the peak
voltage amplitude for the FMG–VIG system was U(t)max=
39.4 ± 1.9 kV.
IV. DIGITAL CIRCUIT ANALYSIS
At the present time, it seems practically impossible to apply
an analytical theoretical approach for describing pulsed gen-
eration in the FMG–VIG system. Instead of an analytical ap-
proach, we created an FMG–VIG digital model and performed
analysis of the electrical circuit of the FMG–VIG system using
the commercial PSpice code [27]. This approach allows us to
predicttheparametersoftheoutput-voltage pulseduetoscaling
the FMG–VIG system.
The equivalent circuit of the FMG–VIG system employed in
digital simulations is shown in Fig. 8. It is consist of two parts.
The first part is the FMG primary power source. It contains the
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1870 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 34, NO. 5, OCTOBER 2006
Fig. 8.Equivalent circuit of the FMG–VIG system employed in digital simulations.
Fig. 9. Simulated waveform of the output voltage U(t) produced by completely explosive FMG–VIG system.
FMG pulsed EMF Eg, the inductance LG, and the resistance
RGof the FMG. The EMF pulse of the FMG, averaged from six
experiments, was digitized in the source section of the PSpice
code. The PSpice inductance and resistance of the FMG were as
follows: LG= 2.25 mH and RG= 15.0 Ω. These values were
averaged from 11 devices used in this experimental series.
The second part of the equivalent circuit is the VIG part
(Fig. 8). Each turn and the next turn of the VIG were considered
as a Blumlein line. A five-turn VIG used in the experiments
was represented in the model as five Blumlein lines (five stages)
connected in series (Fig. 8). The input capacitance of the VIG
was 5.6 nF. The spark-gap switch of the VIG is shown in the
equivalent circuit as switch I. The capacitance and inductance
of the spark-gap switch in the model were Cgap= 100 pF and
Lgap= 10 nH, respectively. The capacitance and resistance of
Tektronix P6015A high-voltage probe were Cp= 3 pF and
Rp= 100 MΩ, respectively.
Results of the simulation of FMG–VIG system are shown
in Fig. 9. Switch I operated in this simulation at a voltage of
5.7 kV. Five stage switches provided short circuiting of the
stages of the VIG during charging process. At 5 ns before
the operation of switch I, all five stage switches of the system
opened, and from this moment of time, the VIG worked as a
line transformer. The amplitude of the voltage pulse produced
byFMG–VIGsystemis42kV(Fig.9),therisetimeofthepulse
is 10.5 ns, and the FWHM is 14.5 ns. Results of the simulation
are in good agreement with experimental results.
V. SUMMARY
We have demonstrated successful operation, for the first
time, of a completely explosive pulsed-power system based
on explosive-driven FMGs as the primary power sources, with
a VIG as a power-conditioning stage. Adding a VIG stage
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