The Development of a Compact Pyroelectric X-Ray Generator

Ross McCart

Nuclear DepartmentHMS Sultan

Project Aims

• Build a Pryoelectric X-Ray Source.

• Test and characterise the source. (Modify design if necessary)

• Research into increasing energy of X-Rays

• Possibly couple source with X-Ray collimator.

• (Adapt the source to enable the production of Neutrons)

X-Ray Tube

Pyroelectric Materials

• Non-conducting crystals develop an electric polarisation when they are subjected to a uniform temperature change.

• Only in crystals with a Polar axis.

• The requirements are fulfilled in about 10 out of the 32 crystal classes.

• Effect known since 314 B.C

• Pyroelectric effect found in motion detection, pollution monitors and in bones.

• Tourmaline, Sugar cane, Lithium Tantalate and Barium Niobate

Properties of Lithium Tantalate

Ferroelectric Effect – Polarising the crystal

LiTaO3

Z+

Z-

+

--

Crystal

LiTaO3

Z-

Li+

OO O

Ta+

Li+

OO O

Ta+

Properties of the Crystal

QACT dt

dTAI CC

For a 100°C change over 180 seconds an emission current of 2x10-8Amps is

predicted.

6.25x1010 electrons per second

The rate of polarisation per change in temperature. Negative as polarisation

occurs when crystal cools.

-2.3x10-4Cm-2K-1 for LiTaO3

Pyroelectric Constant Emission Current

Potential Difference

Cg CC

+ - +

Cg CC

G

G

C

CC

C

d

A

d

A

TA

C

QV

0

X Ray Production

Source Amptek

Cooling CycleHeating Cycle

Setup

Advantages and Disadvantages

• Low power, approximately 1.4mW.

• Runs on a 12V battery or power supply.

• Handheld and portable.

• No Radioactive Sources.

• Solid State – no moving parts

• X-Ray Flux approximately 108 Photons per second

• Isotropic production of X-Rays

• Not a continuous flux

• Cannot be turned off instantaneously

• Limited end point energy with one crystal setup.

Potential Uses

• Security

• X-Ray fluorescence

• Radiography

• Teaching and Research

• Bomb Disposal

• Non-destructive testing

Wikipedia

Neutron Generation

2H 2 H 4He 3He01n 2.45MeV

2H 2 H 4He 3H11p

2H 3 H 4He01n 14.10MeV

The potential barrier of deuterium is 288keV, however the deuterium ions are able to tunnel under the barrier, lowering the energy required.

Goals

Short Term

• Complete Build

• Characterise the electric field from X Ray emission

Research Areas of Interest

• Two Crystal Setup – Increasing Tube Potential

• Stacking Crystals – Increasing Crystal Thickness

• Continuous Flux Using Multiple Crystals

Acknowledgments

• Dr Ian Giles

• Dr Kirk D Atkinson

• Miss Samantha Morris

• Sean Jarmen

• And other members of staff at the Nuclear Department.

Any Questions?