Pulsed Neutrons and Microwaves
from Plasma Devices
Anurag Shyam* and Rishi Verma**
*Energetics and Electromagnetics Division
Bhabha Atomic Research Centre
Gandhinagar, Gujarat, India.
**Pulsed Power Group
Institute of Plasma Research
Gandhinagar, Gujarat, India.
Institute for
Plasma Research
At Gandhinagar
Capital of State
of Gujarat
Greenest City
in the World
INSTITUTE FOR PLASMA RESEARCH
Our Pulsed Power Laboratory is probably the Largest and best Funded Laboratory
in India
Largest Bank (of its kind) in India
1.5 Terra-Watt
Pulse Power System
Largest Pulsed Power System in India
In this presentation I will discuss only those experiments
which can be conducted in a college laboratory namely
Virtual Cathode Oscillator Microwave Device
Electro Cyclotron Resonance Ion Source for Neutrons
Plasma Focus
MOTIVE FOR THIS RESEARCH AND
DEVELOPMENT
Explosive land mines cause a large number of human
casualties every year.
Several areas, all over the world, are infested with them,
from the previous wars.
These have to located and destroyed.
Pulsed neutron sources can help in locating the mines.
High power RF/microwave devices can destroy them.
.
GENERATE PLASMA
EXTRACT PARTICLES (IONS or ELECTRONS)
ACCELERATE - ENERGY TO PARTICLES
USE APPROPRITE TECHNIQUE TO PRODUCE
RF(MICROWAVE) & X-RAYs from ELECTRONS
NEUTRONS & ION IMPLANTATION from IONS
TOPICS TO BE DISCUSSED IN THIS
PRESENTATION
Plasma foci for both neutron and RF/microwave
generation.
Electron cyclotron resonance based ion source for
neutron generation and ion implantation
Microwaves from a virtual cathode oscillator device and
its pulsed power driver
For these devices to be useful in actual field condition,
their efficiencies, scaling and repetition rates are to be
improved. We shall be discussing, in this presentation,
our laboratory experiments and the diagnostics
developed for this purpose.
Neutron Sources
One of the application of pulsed neutron sources is for
detection (in conjunction with other methods) of explosive
and other illicit materials (narcotics, chemical weapon
agents, nuclear materials).
The two techniques we are investigating are
1)Using low energy neutron (D-D fusion) and discovering
the presence of hydrogen by elastic scattering (TNA).
2)Using high energy neutrons for in-elastics scattering
and resultant gamma rays emission for elemental
identification (PFNA)
Neutron Sources
In a typical (accelerator
based) neutron generators
deuterons, from an ion
source, are accelerated and
impinged on a
tritiated/deuterated target.
We are developing these
systems in our laboratory.
However Plasma focus is an
all in one device. However its
repetition rate, life (with one
filling and tritium handling
needs to be improved. Our
laboratory is working in this
direction.
DEVELOPMENT of PLASMA FOCUS as
PULSED NEUTRON SOURCE
Energy: 23kJ Neutrons > 109/dis.
Plasma
Focus
Driver
Capacitors
Plasma Focus Waveforms
Channel 1 : Rogowsky Coil
Channel 2 : X-ray and Neutron output detected by PM Tube
dI/dt
X-Rays
Neutrons
Repetitively Operating Compact D-D
PLASMA FOCUS
Plasma
Focus
Battery Powered Capacitor
Bank with Solid State Switch
ANODE LENGTH OF THE PLASMA FOCUS 45 mm.
DIAMETER OF THE ANODE AND GLASS INSULATOR 12mm.
PLASMA FOCUS CHAMBER USED AS A CATHODE DIA 38 mm.
Capacitor bank: 1 μF,
40 kV
Switch: SCR
Repetition Rate: 1 Hz
Neutrons/Dis (DD): >
106
Number of
discharges in one
filling ~ 100
Multiple Plasma Focus Device
Plasma Focus:
Energy: 5.7 kJ
Current: 200 kA
Neutrons ~ 108 (D-D)
Five such devices will be used
sequence
To increase the repetition rate and
total number of shots.
Target Rate is 50 Discharges/s
And 1000 discharges before gas
change.
CAPACITORS
10 cm long
PLASMA
FOCUS
CURRENT PLASMA
FOCUS DEVELOPMENT
For D-T FillingVery Compact for low tritium
inventory.
Low pressure operation (~0.5
mb).
Low Voltage Operations 4 kV for
compactness and IGBT as
switch.
Four commercial capacitors of 2
µF (~64 J). Current ~ 52 kA.
105-106 DD neutrons.
Rep Rate 3 Hz (Target > 10 Hz)
Half Neutron Life 15 shots
(Target 1000 shots)
Cost of System ~ $ 100.
Can be used as disposable
neutron cartridges
Schematic of High Voltage Neutron Generator
Ion
Source
The heart of this system is Electron Cyclotron Resonance Ion Source
Principle of Electron Cyclotron Resonance
Electron Cyclotron Resonance (3 mA) Deuterium
Ion Source in our Laboratory
ECR ion source
is an small mirror devices with plasma
being generated by microwave and ion
extracted by high voltage on one end.
The mirror has been built using 2 sets of
four bar shaped (NdFeB -0.9 T –
commercially available) permanent
magnets.
The microwave (300 W, 2.45 GHz) is
injected using a (dismantled) microwave
cooking oven.
A current ~ 1 mA of deuterium (10-3 mB
pressure) can be extracted with 5 KV
pulses.
Technology is not too complex and
inexpensive (< $ 300).
The device can be used for ion
implantation and neutron generation
Pulsed Microwave Generator
Pulsed Microwave Generator
It is fairly easy to fabricate and operate a Vircator (as
easy as plasma focus)
The pulsed power system is a bit more technologically
challenging (1 GW Vircator, which may be requires for
demining, requires ~1 MV, ~60 kA, 50 ns system.)
However, for laboratory studies, we have developed
vircator, which operate at ~100 kV, ~8 kA system.
Simple pulse transformer, using RG-213, cable has been
developed.
A RG-218 based pulse forming line has been developed.
This makes the system technologically simple.
The cost of the system is < $ 1000
Voltage - 500 kV
Current - 35 kA
WATER
PFLSPARK
GAP
Current
100 kA
PULSE
TRANSFORMER
TESLA TRANSFORMER - WATER PFL - VIRCATOR
VIRCATOR
DISPOSABLE TESLA TRANSFORMER and
DISPOSABLE SOLID DIELECTRIC PULSE FORMING
LINE & HPM-VIRCATOR
VIRCATOR: 100 kV, 12.5 ohm 2.5 GHz Neon Lamp Glow
VIRCATOR
With VIRCATOR Operating
With only Pulsed Power
Operating (VIRCATOR Off)
THANK YOU
FOR YOUR
ATTENTION