THERMOLUMINESCENCE PROPERTIES OF DYSPROSIUM-DOPED

CALCIUM BORATE GLASS FOR DOSE MEASUREMENT SUBJECTED TO

IONIZING RADIATION

HAMIZA BINTI AHMAD TAJUDDIN

UNIVERSITI TEKNOLOGI MALAYSIA

iv

THERMOLUMINESCENCE PROPERTIES OF DYSPROSIUM-DOPED

CALCIUM BORATE GLASS FOR DOSE MEASUREMENT SUBJECTED TO

IONIZING RADIATION

HAMIZA AHMAD TAJUDDIN

A thesis submitted in fulfillment of the

requirements for the award of the degree of

Master of Science (Physics)

Faculty of Science

Universiti Teknologi Malaysia

JUNE 2014

vi

I specially dedicate this work

To my lovely parents and parents in law Halijah Binti Haji Zabidi

Muhammad Amin Chen Bin Abdullah Suhana Binti Sudin

Mohd Shafie Bin Sukaimi

Whose love, kindness, patient and prayers have brought me this far

To my beloved husband Mohd Hairi bin Shafie

For his love, understanding and support through my endeavor

To my lovely daughters Arissa Amani and Damia Darwisyah

They fill my life with bundle of joy

To my sibling and friends

For their endless laugh and tears

Thank you so much!!!

vii

ACKNOWLEDGEMENT

In the name of Allah, the Most Gracious, Most Merciful. Praise to Allah

S.W.T, Peace and blessings of Allah be upon His Messenger, Muhammad S.A.W.

and all his family and companions.

First and foremost, I would like to express my sincere appreciation to My

supervisor Prof. Dr. Husin Wagiran and Co-supervisor, Prof. Dr. Rosli Husin and

also Dr. Suhairul Hashim for their supervision, support, guidance and encouragement

during my study toward the successful completion of this study.

Special thanks are also extended to the support of technical staff at the

Physics Department, and Ibnu Sina Institute, Universiti Teknologi Malaysia, in

particular, Mr. Nazri, Mr. Jaafar, Mrs Anis and Mrs Shazwani for their assistance

and cooperation. I gratefully acknowledge support from Mr. Hassan Ali, from

Department of Oncology and Radiotherapy, Hospital Sultan Ismail for giving an

outstanding help and guidance in the early stage of this study.

I am sincerely grateful to the government of Malaysia for a funded Master

scholarship. I am also indebted to the Academy of Sciences Malaysia, Ministry of

Science, Technology and Innovation of Malaysia and Ministry of Higher Education

of Malaysia for providing research grants for this research.

Last but not least, I would like to extend a special note of thanks to my

colleagues for their motivation and friendship during my studies in Universiti

Teknologi Malaysia. Only Allah S.W.T. can repay all your kindness.

viii

ABSTRACT

Thermoluminescene (TL) dosimeters are widely used in radiation therapy to

verify the radiation dose received by cancer patients. This research was carried out to

study the TL properties of Dysprosium (Dy) doped borate glass as a TL dosimeter

subjected to photon and electron irradiations. The glass samples with various Dy

concentrations were prepared by melt-quenching technique. X-Ray diffraction

analysis indicates that the glasses are amorphous. The performance of the glass

samples were compared to the TLD-100 in terms of TL response, linearity,

sensitivity, dose response, fading and reproducibility. The addition of Dy2O3 in

borate glass enhanced TL sensitivity and improved the TL intensity of the glass. It

was found that calcium borate with Dy concentration of 0.30 mol% was the optimum

concentration to produce the highest TL response. The TL intensity increased with

Dy concentration up to 0.40 mol% before it begin to gradually decrease. This

phenomenon is due to the concentration quenching. The TL properties were studied

over the useful radiotherapeutic dose in the range of 0.5 Gy to 4 Gy when subjected

to 6 and 10 MV photon and 6 and 12 MeV electron irradiation. The sensitivity of Dy

doped calcium borate was 5.8 times more sensitive than that of undoped sample and

6.8 times less sensitive compared to TLD-100. A correlation coefficient of 0.98 was

obtained for reproducibility and the minimum fading for this glass was 10% for 60 days

observation. By using XCOM software, the Zeff of the glass was found to be 12.14 and

13.60 for undoped and Dy doped glass, respectively.

ix

ABSTRAK

Dosimeter luminesens terma (TL) digunakan secara meluas dalam terapi

sinaran untuk mengenal pasti jumlah dos sinaran yang diterima oleh pesakit kanser.

Kajian ini dijalankan untuk mengkaji sifat TL kaca borat yang didopkan dengan

Dysprosium (Dy) sebagai dosimeter TL terhadap penyinaran foton dan elektron.

Sampel kaca dengan pelbagai kepekatan Dy disediakan dengan teknik pelindapan

lebur. Analisis pembelauan sinar-X menunjukkan kaca tersebut adalah amorfus.

Prestasi sampel kaca telah di bandingkan dengan TLD-100 dari segi sambutan

luminesens, kelinearan, kepekaan, sambutan dos, kepudaran dan kebolehulangan.

Penambahan Dy2O3 ke dalam kaca borat meningkatkan kepekaan dan keamatan

luminesens terma kaca tersebut. Kajian mendapati kalsium borat dengan kepekatan

Dy sebanyak 0.30 mol% adalah kepekatan optimum yang menghasilkan sambutan

luminesens terma tertinggi. Keamatan luminesens terma meningkat dengan

kepekatan Dy sehingga 0.40 mol% sebelum ia mula berkurang secara beransur-

ansur. Fenomena ini disebabkan oleh berlakunya lindapan kepekatan. Ciri

luminesens terma telah dikaji pada julat berguna dos radioterapi 0.5 Gy hingga 4 Gy

terhadap penyinaran foton 6 MV and 10 MV dan penyinaran elektron 6 MeV dan 12

MeV. Kaca borat yang didopkan dengan Dy mempunyai kepekaan 5.8 kali ganda

berbanding dengan kaca yang tidak didopkan dan 6.8 kali ganda kurang kepekaan

berbanding TLD-100. Pekali korelasi sebesar 0.98 dihasilkan untuk kebolehulangan

dan kepudaran minimum bagi sampel ini ialah 10% untuk tempoh 60 hari. Dengan

menggunakan perisian XCOM, Zeff bagi sampel kaca ialah 12.14 bagi kaca tidak

didopkan Dy dan 13.60 bagi kaca yang didopkan Dy.

x

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xiv

LIST OF ABBREVIATIONS xvi

LIST OF APPENDIX xvii

1 INTRODUCTION 1

1.1 Research Background 1

1.2 Problem Statement 4

1.3 Research Objectives 5

1.4 Scope of Study 5

1.5 Significant of the Research 7

2 LITERATURE REVIEW 8

2.1 Introduction 8

2.2 Basics Radiation Dosimetry 8

xi

2.3 Thermoluminescence Mechanism 9

2.3.1 Thermoluminescence Phenomena 12

2.4 Thermoluminescence Dosimetry (TLD)

Properties 13

2.5 Thermoluminescence Theory 14

2.5.1 First Kinetic Order 14

2.5.2 Seccond Kinetic Order 16

2.6 Definition of Glass 17

2.6.1 Borate Glass 18

2.7 Rare Earth (Lathanides) 19

2.7.1 Dy3+

ions 20

2.8 Thermoluminescence Studies on Borate

Glass 20

3 RESEARCH METHODOLOGY 22

3.1 Introduction 22

3.2 Sample preparation 23

3.3 X-ray Diffraction (XRD) Analysis 27

3.4 EDXS Analysis 29

3.5 Irradiation Facility 30

3.5.1 Photon Irradiation 31

3.5.2 Electron Irradiation 32

3.6 TL Measurement 33

3.6.1 TLD Reader System 34

3.7 Calculation of Effective Atomic Mass 35

4 RESULT AND DISCUSSION 36

4.1 Glass Composition 36

4.2 X-ray Diffraction Analysis 38

4.3 Optimum Doped Glass Sample 39

4.3.1 TL Glow Curve 40

4.4 Optimum Heating Rate Setting 42

4.5 Annealing Temperature Setting 43

xii

4.6 TL Properties for Photon and Electron Irradiation 44

4.6.1 TL Glow Curve 44

4.6.2 Linearity 47

4.6.3 Energy Independence 53

4.6.4 Reproducibility 56

4.6.5 Fading 60

4.6.6 Sensitivity 63

4.6.7 Lower Limit of Detection Dose 64

4.7 EDAXS 65

4.8 Effective atomic number 67

5 CONCLUSION 69

5.1 Summary of Findings 69

5.2 Recommendations and Future Research 71

REFERENCES 72

Appendix A - B 75-77

xiii

LIST OF TABLES

TABLE NO TITLE PAGE

3.1 The composition of undoped and Dy doped calcium 23

borate glass

4.1 Nominal composition of xCaO – (100-x) B2O3 38

4.2 The composition of CaO-B2O3 glass system 38

4.3 The reproducibility data for doped sample after 2 times

irradiation 57

4.4 The reproducibility data for undoped sample after 2 times

irradiation 59

4.5 Summary of percentage loss of TL signal (due to fading)

over the first 24 hours post-irradiation of various TL

material 62

4.6 TL sensitivity (TL yield.mg-1

.Gy-1

) for TLD-100 calcium

borate doped Dy and undoped calcium borate glass with

10 MV photon. 64

4.7 TL sensitivity (TL yield.mg-1

.Gy-1

) for TLD-100 calcium

borate doped Dy and undoped calcium borate glass with

6 MeV electron. 64

4.8 Element compositions for doped and undoped calcium

borate glass for 30CaO-70B2O3 glass composition. 67

4.9 Zeff calculation for glass sample at different mol % Dy 69

xiv

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 The family tree of luminescence phenomena 10

2.2 Energy level representation of TL process 11

2.4 Amorphous structure a) crystal b) Glass 17

3.1 Analytical balance 24

3.2 High temperature furnace used in sample preparation

and low temperature furnace for annealing process 25

3.3 Scheme of the steps 26

3.4 Siemens Diffractometer D5000 28

3.5 X-Ray Diffraction (XRD) principles 28

3.6 Energy-dispersive X-Ray spectrometer 30

3.7 Linear accelerator Primus MLC 3339 (LINAC Primus)

at the Department of Radiotheraphy and Oncology

Hospital Sultan Ismail, Johor Bahru 31

3.8 The sample position during electron irradiation 32

3.9 TLD Reader Hawshaw model 4500 33

3.10 Schematic diagram of a typical TLD reader 34

4.1 The X-Ray diffraction spectra for doped and

undoped glass samples 39

4.2 The bar chart of TL response against absorbed dose. 40

4.3 Glow curve for different mol (%) dopant concentration 41

4.4 Behaviour of TL response (normalized) and the

Corresponding standard deviation as a function

of heating rate 42

4.5 Behaviour of the TL response and the corresponding

standard deviation as a function of the annealing

xv

temperature 43

4.6 The glow curve for different absorded dose after

6 MVphoton 45

4.7 The glow curve for different energy of photon

Irradiation 46

4.8 Glow curve for 6 MV photon and 6 MeV electron 47

4.9 TL response in (nC/mg) of TLD-100, undoped and

Dy-doped Calcium borate glass for 6 MV photon

irradiation versus Dose in unit Gy 49

4.10 TL response in (nC/mg) of TLD-100, undoped and

Dy-doped Calcium borate glass for 10 MV photon

irradiation versus Dose in unit Gy 50

4.11 TL response in (nC/mg) of TLD-100, undoped and

Dy-doped Calcium borate glass for 6 MeV photon

irradiation versus Dose in unit Gy 52

4.12 TL response (nC/mg) of TLD-100, Dy-doped and

undoped calcium borate glass for 12 MeV electron

irradiation versus dose in Gy 53

4.13 The energy response of 0.3 mol% doped Dy for 6

and 10 MV photon irradiation. 55

4.14 Reproducibility of Dy-doped calcium borate glass

of 6 MV photon irradiation. 58

4.15 Reproducibility of undoped calcium borate glass

with 6 MV photon irradiation 59

4.16 The fading of Dy-doped calcium borate glass for

10 MV photon irradiation. 61

4.17 The fading of TLD-100 for 10 MV photon

irradiation 61

4.18 The fading of undoped Dy calcium borate glass

for 10 MV photon irradiation. 62

4.19 (a) Elemental spectrums of Dy doped sample

(b) Elemental spectrums for undoped sample. 66

4.20 The effective atomic number of 30CaO-(70-x) B2O3

glass system 68

xvi

(where x = 0, 0.05, 0.1, 0.2, 0.3 and 0.4 mol %

xvii

LIST OF SYMBOLS

Å - Angstrom

B2O3 - Pure borate

°C - degree calcius

C - Coulomb

CaO - Calcium Oxide

CaCO3 - Calcium Carbonate

d - Thickness

D - Absorbed dose

Dy - Dysprosium

Dy2O3 - Dysprosium dioxide

E - Energy difference

ε - Energy

F (D) - Dose response

Gy - Gray

k - Boltzmann’s constant

LiF - Lithium fluoride

LiO - Lithium Oxide

m - Mass

M - TL signal

MgO - Magnesium Oxide

N2 - Nitrogen

n - Refractive index

n - number if trapped electron

P - Probability of escaping per unit time

Т - Temperature

t - Time

τc - Characteristic time

xviii

wi - Fraction of that element

Z - Atomic number of the atom

Zeff, - The effective atomic number

λ - Wavelength

σ - The standard deviation

xix

LIST OF ABBREVIATIONS

EDXS Energy dispersive X-ray spectroscopy

ECC Element correction coefficient

ICRP International Commission on Radiological Protection

LINAC Linear accelerator

MU Monitor Unit

PMT Photomultiplier

RCF Reader calibration factor

SSD Source to surface distance

TLD Thermoluminescence dosimeters

TL Thermoluminescence

TTP Time temperature profile

XRD X-ray diffraction

WinREMS Window Radiation Evaluation and Management system

xx

LIST OF APPENDIX

APPENDIX TITLE PAGE

A The glass preparation calculation 76

B Titles of paper/conference (International/Local) 78

1

CHAPTER 1

INTRODUCTION

1.1 Research Background

Marie Curie died because of over expose to her discovery which is radium.

Thomas Edison discovers about the fluoroscope but he stopped his work in this area

after his assistant died due to an X-ray overdose. Two cases above had proved that

radiation can give bed effect if wrongly handled it. After many years later, there are

some improvements in understanding of the dangers of radiation, and yet human

often fail to handle it safely. It is easy to become pleased about the dangers of

radiation as it is invisible and odourless. As a result, radiation practitioner may

expose patients as well as workers to higher levels of radiation than necessary. The

hazard of excess radiation exposure is not insignificant and leading to a variety of

health issues.

Recently, research groups have reported a number of radiation effects on the

applications of glass as such the development of the optically stimulated

luminescence methodology for use with doped glass material with its possible use as

dosimeter material, measurement in-vivo of the absorbed dose in patients exposed to

radiation therapy and diagnosis (Aznar et al., 2002), and the use of borate glass as

TLD material (Espinosa et al., 2006).

Many authors have studied polycrystalline glass of alkaline and earth borate

compounds. Recently, there are many studies on thermoluminescence dosimetry

focusing on improving the TLD characteristic performance. Furthermore, the

2

increasing use of ultraviolet, X-ray and gamma radiations in industrial and medical

applications has motivated researchers on the search for new host materials with high

potential of TL properties (J. Li et al, 2005). Why choose borate instead of other

glass material? It is because borate glass compounds have been widely studied due to

their features as glass formers and also reported of being very advantageous

materials for radiation dosimetry application (Satiago et al 2001)

There are numbers of advantages of doped borate glass as radiation

dosimeter. For instance, unlike conventional TLDs, the borate glass has very low

hygroscopic nature. This is an important point for TL dosimeters because the water

can cause an adverse effect on the TL efficiency of the material associated with non-

radioactive relaxations during thermal stimulation. (McKeever, 1985).

Commercially available TLD materials such as lithium fluoride, calcium

fluorite, calcium sulphate, lithium borate and quartz are used as dosimeters in

medical, personnel, archaeological and environmental applications. However, they

have many disadvantages such as long annealing time and not reproducible (Li Juan

et al, 2008). In recent study, TLD materials have been extended to nano material and

optical fibre. Fibre Optics for example is impervious to water and for some instance

it becomes possible to locate the fibre dosimeter within a particular tissue.

The wide variety of TLD materials and their different physical forms allow

the determination of different radiation qualities at dose levels from µGy to kGy.

Most applications and major part of the literature are based on lithium fluoride doped

with magnesium and titanium (LiF:Mg, Ti). However other materials such as CaSO4:

Dy is widely used and recently TL material LiF:Mg, Cu, P also show great potential

as radiation dosimeter. In most materials, the linear interval is limited by super

linearity and decay of the TL intensity at large doses.

The useful range was determined by linear dose dependence. High sensitivity

such as high TL signal per unit absorbed dose is also one of the requirements for

TLD material. High sensitivity is an important requirement if the TLD materials are

used as personal and environmental radiation monitoring. Low dependence of TLD

3

response on the energy of the incident radiation and long fading, i.e the ability to

store dosimetric information for a long time are also required as TLD materials. The

luminescence spectrum should match the maximum spectral sensitivity of the

photomultiplier and the TL disimetric material should be mechanically strong,

chemically inert and radiation resistant. Generally, these requirements should be

fulfilled in order to produce high quality TL dosimeter.

Rare earth elements are interesting dopants donating material in host glass. In

many cases, such as in optical absorption or light emission, there exists a direct

relation to the energies in the ground and excited states of the electron system. In

recent years, studies on rare earth doped glasses have gained much interest of

researchers for the reason that the particular 4f electronic configuration of rare earth

in varied glass matrixes leads to emissions from ultraviolet to infrared with many

potential uses including in thermoluminescence dosimeter (Ferhi et al., 2009).

The present studies intend to investigate new material based on borate (B2O3)

glasses and mixed with other material such as calcium. The presence of dopants in

calcium borate glass can greatly enhance the TL sensitivity to ionizing radiations by

providing an increase number of traps. Furthermore, addition of dopant can enhance

the chemical durability and stability of the glass host.

1.2 Problem Statement

Although the fast development of active real-time electronic dosimeters,

passive dosimeters which integrate absorbed dose over a period of time are still in

demand and are frequently obligatory in radiation protection. Thermoluminescence

dosimeters are now gaining popularity in individual dosimetric services, replacing

dosimetric films, which were commonly used in the past century (Olko et al, 2006).

The property of thermoluminescence materials to ionizing radiation depends on the

relationship between the absorbed dose and the intensity of light emitted. In personal

dosimetry, thermoluminescence detectors are commonly used due to their major

advantages such as high sensitivity, low doses as low as 1 μGy to be measured, and

4

linear dose response up to at least 1 Gy, good energy response, reproducibility, and

resistance to high humidity and magnetic fields.

Despite all advantages stated above, there are also some disadvantages of any

thermoluminescence detectors such as signal erased during readout, easy to lose

reading, no instant readout, readout and calibration time consuming and not

recommended for beam calibration. TLD phosphors that most frequently used in

medical applications are LiF:Mg,Ti and LiF:Mg,Cu,P due to their tissue equivalence

characteristics. However, these well-established materials have several notable

drawbacks, including being hygroscopic and not able to store permanently dose

information since the reading of the detectors erases the dosimetric information.

TLDs only provide integrated dose information sometime after the patient has been

irradiated. Therefore, the radiotherapist cannot adjust the exposure in real-time to

ensure that the proper dose is delivered to the desired region. Additional limitations

of TLDs include their poor dose reproducibility, limited dynamic range and in certain

cases nonlinear responses (Soltani et al., 1992).

Even though many new long lasting thermoluminescence materials are

developed, the thermoluminescence phenomenon by calcium borate remains to be

explored. Thus, in this study, TL properties of Dy-doped calcium borate will be

carried out.

1.3 Research Objectives

1.3.1 To prepare and determine the optical properties of undoped and Dy-doped

calcium borate glass system.

1.3.2 To investigate the thermoluminescence properties of undoped and Dy-

doped calcium borate glass subjected to photon and electron irradiations.

5

1.4 Scope of study

In this study, an important characteristic of dosimeters such as fading, TL

glow curve, linearity, reproducibility and sensitivity characteristic of undoped and

Dy-doped calcium borate glass subjected to photon and electron irradiation will be

explored. This material might have potential as TLD material and can be used for

variety application such as environmental or personal dosimetry.

The irradiation on the glass sample has been conducted at dose ranging from

0.5 – 4.00 Gy subjected to photon and electron irradiation. The ionizing sources were

delivered by using Primus MLC 3339 linear accelerator machine (LINAC). The

energy used in this study was 6 and 10 MV photon beams and 6 and 12 MeV

electron beams.

The study of fading on calcium borate glass has been performed by using 10

MV photon beams for 1, 2, 3 and 4 Gy. Readings of TL response were obtained until

60 days after 24 hours irradiation. For reproducibility characteristic, the glass

samples were exposed to 6 MV photon with 4 Gy absorbed dose.

In this study, the effective atomic number, Zeff for glass sample has to be

determined by using XCOM method. Besides that, XRD analysis was carried out to

give confirmation on amorphous nature of sample. Since this glass sample was a new

material prepared, an investigation of sample composition is very important.

Therefore, Energy Dispersive X-ray Spectroscopy (EDXS) was used in this study.

The current chapter provide introduction to the problems associated with TL

and a review of the existing literature regarding the subject. Chapter 2 explained

previous study and theories regarding the TL models, radiation interactions, principle

of TLD and their important characteristics as a radiation dosimeter and brief

6

introduction to the technique related in this study. Chapter 3 describes the

methodology and equipment used. In Chapter 4, a range of thermoluminescence

studies and the results obtained are presented and discussed in detail. Chapter 5

summarizes the findings of this investigation, and provides an outlook for future

study in this area.

1.5 Significant of the research

This work intends to study TLD material with chemically and physically

stable and also has high TL response and good sensitivity. Calcium borate glass can

easily be prepared at low melting temperature and low cost compared to other TL

materials such as lithium fluoride, lithium borate, calcium fluoride and calcium

sulphate. The doping ion, Dy in borate host glass is expected to enhance the TL

intensity. Such study will gain knowledge for further research in the development of

new TL materials for medical and environmental applications.

72

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