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